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Rendering mortars with incorporation of very fine aggregates from construction and demolition waste
Construction and Building Materials 229 (2019) 116844
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Rendering mortars with incorporation of very fine aggregates from construction and demolition waste Sara Jesus a, Cinthia Maia a,b, Catarina Brazão Farinha a,b, Jorge de Brito a,⇑, Rosário Veiga b a b
CERIS, Instituto Superior Técnico, University of Lisbon, Av. Rovisco Pais, 1, 1049-001 Lisbon, Portugal National Laboratory for Civil Engineering, Av. do Brasil 101, 1700-066 Lisbon, Portugal
h i g h l i g h t s CDW as a filler incorporation improved the workability of the mortars. Mechanical strengths were improved by the incorporation of RCA and MRA from CDW. Water absorption was reduced by the incorporation of RCA and MRA. The incorporation of RCA and MRA reduced the deformability of the mortars. Modified mortars presented significant microcracking.
a r t i c l e
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Article history: Received 2 May 2019 Received in revised form 1 August 2019 Accepted 1 September 2019
Keywords: Render Mortar Filler CDW Reuse Sustainability
a b s t r a c t The intense rate of construction and demolition waste generation (CDW) over the years should boost recycling. The use of CDW as constituents of cementitious composites has been considered a feasible alternative to dumping. This paper presents a study of the behaviour of cementitious renderings incorporating very fine recycled aggregates from two types of CDW. Only particles of recycled aggregates below 0.149 mm were used as filler, hereinafter referred as recycled concrete aggregate (RCA) and mixed recycled aggregate (MRA). The incorporation’ percentages used were 0%, 10%, 15% and 20% of natural aggregates’ volume. Several tests have been carried out, in order to evaluate the mortars in terms of mechanical strength, workability, water absorption, dimensional instability and water vapour permeability. The experimental programme consisted in three consecutive phases, in which the mortars that presented the best performances were selected for a deeper analysis of their features. The test results showed that modified mortars had a better behaviour in most of tests compared with the reference mortar (with no CDW). Mortars with incorporation of 20% of RCA and 15% of MRA presented the best performance. Ó 2019 Elsevier Ltd. All rights reserved.
1. Introduction As the population continues to grow, there is also a subsequent development of economic sectors and therefore a significant increase of energy and natural resources’ consumption. Construction and demolition waste (CDW) has been considered a relevant environmental issue. According to Eurostat [1], the amount of CDW generated in 2014 was 868 million tonnes. In order to encourage the use of recycled aggregates, the Waste Framework Directive 2008/98/EC of the European Parliament established a target for all the member states of European Union: at least 70% of reduction, reuse and recycling of CDW by 2020. ⇑ Corresponding author. E-mail addresses: [email protected] (S. Jesus), cinthiamaia@tecnico. ulisboa.pt (C. Maia), [email protected] (C. Brazão Farinha), jb@civil. ist.utl.pt (J. de Brito), [email protected] (R. Veiga). https://doi.org/10.1016/j.conbuildmat.2019.116844 0950-0618/Ó 2019 Elsevier Ltd. All rights reserved.
To accomplish this aim, there have been several researches focused on the use of recycled aggregates. One of the viable solutions is the replacement of natural sand for recycled aggregate in mortar production [2–10]. Notwithstanding some shortcomings of recycled aggregate such as high heterogeneity, high water absorption and presence of contaminants [2,11–13], studies have reported that fine recycled aggregate could result in improvements on the performance of mortars, with a proper production process and pre-treatments. Although several works have been published about the use of recycled aggregate as replacement of natural sand, the incorporation of recycled aggregate from CDW as filler has limited studies. Several researches focused on the behaviour of mortars with incorporation of fine recycled aggregates of construction waste such as ceramics, concrete, glass, sanitary ware, marble powder and glass fibre reinforced polymer [8,14–18]. These studies allowed positive
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prospects concerning the use of the finest material of recycled aggregates. Regarding the incorporation of fine recycled aggregate from CDW, a few works presented general results [10,19,20]. The incorporation of the fine particles provided improvements in the mortar performance, concerning properties such as workability, mechanical strength, water absorption and adherence strength [8,14,15–20]. In this work, mortars with non-structural functions with incorporation of CDW and low cement contents, hence very significantly influenced by the aggregates’ characteristics, were studied. Several functional and durability characteristics were assessed, such as shrinkage, cracking behaviour, modulus of elasticity, durability and water vapour permeability that were not determined in previous studies for these kinds of wastes. Ledesma et al. [10] investigated the replacement of fine natural sand by fine recycled aggregate in masonry mortars. Therefore, in this study, the performance of rendering mortars is analysed, in order to develop a new cementitious rendering. Modified mortars reduced the water requirement to maintain similar consistency [8,14–20]. This is due to the filler effect as the fines fill the voids within the mortar structure, decreasing the amount of water required to hydrate and lubricate the aggregates [18]. Mechanical strengths, as flexural, compressive and adherence strength, are significantly improved compared with the reference mortars, when filler wastes are introduced. The incorporation of these particles produces more compact mortars, due to the filler effect [8,14–20]. Mortars with fine waste presented a better adherence strength than the mortars with only sand as aggregate [8,14–20]. It was found that the incorporation of fines enhanced the mechanical behaviour of the mortars, and this could be explained by the cement, water and fines that are partially absorbed by the substrate and develop a stronger bond. The compactness of mortar also influences the water absorption. The incorporation of fine waste material provided a smaller water absorption of modified mortars when compared to plain mortar [8,14–20]. This is due to a denser microstructure, linked to the filler effect. Even though the fines provide a greater compactness of the modified mortars, which results in many advantages, the authors reported some drawbacks such as higher modulus of elasticity and higher susceptibility to cracking [8,14–20]. The increase of the modulus of elasticity implies a stiffer mortar, which means a lower capacity to deform under the action of stresses from loading. This can lead to internal and external cracking in the modified mortars. The aim of this work is to contribute to the study of an alternative to natural aggregates, using the finest material of recycled aggregates from construction and demolition waste. The main objective of this study is to boost the use of this waste in cementitious materials in non-structural applications, namely coatings, presenting many advantages regarding mechanical and water behaviour. Different characteristics such as shrinkage, crack behaviour and durability were assessed, in order to examine the possibility of significant drawbacks that could hinder the feasibility of application. The new applications contribute to providing a better disposal of the wastes. This research analyses the use of two types of recycled aggregate: recycled concrete aggregate (RCA) and mixed recycled aggregate (MRA), in ratios of 0%, 10%, 15% and 20%. The mortar performance was evaluated in the fresh and hardened state.
2.1. Materials Modified mortars were produced with replacement of sand (in volume) with fine recycled aggregate (RCA and MRA) from CDW, at 10%, 15% and 20%. Only particles of recycled aggregates below 0.149 mm were used. RCA were made of mainly crushed concrete and MRA were composed of several CDW materials such as mortar, concrete, ceramics, plastic, glass, metals, gypsum and wood. The mortars were produced with: cement, river sand and fine recycled aggregate from CDW. The binder used was cement type CEM II/ B-L 32.5 N, from the Portuguese cement producer Secil. The natural sand was from the Tagus River and only particles below 2.38 mm were used. The recycled aggregates came from two Portuguese CDW recycling plants: RCD - Resíduos de Construção e Demolição SA (recycled concrete aggregates) and SGR Ambiente (recycled mixed aggregates). The type of recycled aggregate, degree of contamination and particles’ size were indicators for the selection. The recycled aggregates were purposely used without any additional processing, to preserve the properties inherent to the manufacturing process. The sand and recycled aggregates grading curves are presented in Fig. 1. It is noticed that river sand consists of about 0.73% of particles below 0.149 mm. In this research, the incorporation of filler intended to reach a ratio of particles below 0.149 mm of 10%, 15% and 20%. Since sand already presents 0.73% of the particles under this value, the incorporation of CDW was slightly smaller than reported, about 9.27%, 14.27% and 19.27%. However, in order to simplify, values of 10%, 15% and 20% were used to characterize the incorporation of recycled aggregate. The river sand presented a continuous grading curve, which leads to more compact mortars. Also, it was found that the recycled aggregate presented a higher content of fines compared to the sand, especially MRA that presented about 5% of particles below 0.149 mm. Through the apparent bulk density test, it was noticed that RCA and MRA presented apparent bulk density lower than that of the river sand. The test results are presented in Table 1. Recycled aggregates obtained from recycling plants of CDW are very heterogeneous, and therefore a meticulous characterization was carried out. Although the incorporation, in this research, was only of particles below 0.149 mm, physical, chemical and mineralogical tests were performed. Table 2 shows the composition of each recycled aggregate used. These results cannot be generalized, since waste materials depend on the type of construction and the constructive technology where they were used originally. Therefore, recycled aggregates’ properties vary over time and from place to place. Table 3 presents the detailed composition of the recycled aggregates. Although RA contains few contaminants, it could be found that this does not make its use unfeasible. The chemical analyses by FRX are presented in Table 4.
2. Experimental programme In order to evaluate the influence of the fine recycled aggregates from CDW, various standard tests used for the assessment of the performance of renderings were carried out.
Fig. 1. Particle size distribution of sand and recycled aggregates.
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Table 1 Apparent bulk density of the constituents of the mortars produced. Constituents
Apparent bulk density (kg/m3)
Cement River sand RCA (0.149 mm) MRA (0.149 mm)
1030 1471 878 810
3
REF – Reference mortar 0% of incorporation; RCA10 – Mortar produced with 10% of RCA incorporation; RCA15 – Mortar produced with 15% of RCA incorporation; RCA20 – Mortar produced with 20% of RCA incorporation; MRA10 – Mortar produced with 10% of MRA incorporation; MRA15 – Mortar produced with 15% of MRA incorporation; MRA20 – Mortar produced with 20% of MRA incorporation.
2.2. Methods The experimental programme was divided in three phases:
Table 2 Composition of the recycled aggregates. Aggregate
Cementitious residues (%)
Ceramics (%)
Others (%)
RCA MRA
99.67 70.83
0.29 17.34
0.04 11.82
Table 3 Detailed composition of the recycled aggregates. Tests
RCA
MRA
Water soluble chlorides (%Cl) Total sulphurs (%SO3) Acid soluble sulphates (%SO3) Contaminants (%) Humus content
<0.010 0.1 0.3 0.3 Not detected
0.021 1.8 4.4 8.6 Not detected
Table 4 Chemical composition of the recycled aggregates. Elements (% in mass)
RCA
MRA
Al2O3 SiO2 P2O5 SO3 Cl K2O CaO TiO2 Fe2O3 ZnO PbO Others
3.59 39.71 0.00 1.64 0.02 1.18 52.52 0.29 1.01 0.01 0.002 0.018
3.90 55.27 0.19 9.37 0.10 2.08 26.42 0.43 2.12 0.08 0.01 0.03
The FRX analysis showed SiO2, CaO and Al2O3 as the major components of both recycled aggregates, which are related to natural aggregates, ceramics and hardened mortar residues. Also, in DRX analysis detected cementitious components, quartz and calcite in the recycled aggregates. Gypsum was found in the composition of MRA. These analyses may explain the differences in the mortars’ behaviour. All the mortars evaluated had the same volumetric ratio of 1:4 (binder: aggregate); the composition of the mortar mixes is described in Table 5. The mortars are specified as: Table 5 Composition of the mortar mixes (kg/m3). Mortar
REF RCA10 RCA15 RCA20 MRA10 MRA15 MRA20
Water
230 208 204 198 200 198 205
Cement
205.9 205.9 205.9 205.9 205.9 205.9 205.9
River sand
1177.1 1068.8 1010.0 951.1 1068.8 1010.0 951.1
Recycled aggregate Concrete
Mixed
– 64.6 99.7 134.9 – – –
– – – – 59.6 92.0 124.3
First experimental phase: characterisation of the components of the mortar - cement, sand and recycled aggregates; Second experimental phase: characterisation tests of all the mortars. Modified mortars with the most satisfactory results were selected for the final experimental phase; Third experimental phase: more specific tests for assessment of the performance of renders were carried out on the mortars (chosen from the previous experimental phase). The methods used in the tests are indicated hereinafter, in Table 6. To ensure an adequate workability and to improve the comparability of the mortars, the values of consistency were fixed in the spread range of 160 ± 3 mm. All specimens of hardened mortar were submitted to the same curing conditions, except in the ‘‘susceptibility to cracking”, ‘‘shrinkage” and ‘‘water vapour permeability” tests. The specimens for most of the tests, as specified by the European standards [21–35], were subjected to a relative humidity of 95 ± 5% and a temperature of 20 ± 2 °C for 2 days inside the moulds. After demoulding, the specimens were maintained in the same conditions for 5 more days. Afterwards, the specimens were submitted to a 65 ± 5% relative humidity until being tested. In the susceptibility to cracking and shrinkage tests, the specimens were submitted to a temperature of 23 ± 2 °C and relative humidity of 50 ± 5% until they were tested. In water vapour permeability tests, the specimens were maintained in a temperature of 23 ± 2 °C and relative humidity of 95 ± 5%. After demoulding, the relative humidity was 50 ± 5%.
3. Results and analysis 3.1. First experimental phase 3.1.1. Consistency of fresh mortars The consistency test quantifies the water content to be added to the mortar, in order to obtain a pre-defined fluidity of fresh mortar. The results are presented in Table 7. The incorporation of fine recycled aggregate up to 20% ratio decreases the water content to maintain the same workability, for both wastes incorporated. This reduction is due to the filler effect. The fine particles of recycled aggregate filled the empty voids between the larger particles of sand, decreasing the amount of water needed in the mix [18]. There are some characteristics of the wastes that tend to decrease the workability, as their water absorption [36], but the filler effect overlapped those effects and was responsible for a reduction of the water content. All the mortars have the same volumetric ratio and, therefore, the same binder content. As a consequence of the incorporation of recycled aggregate, the water/binder ratio decreases. The reduction of water needs and, as a consequence, the reduction of the water/binder ratio can indicate better mechanical behaviour of the mortar.
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Table 6 Methods used in the experimental campaign. Experimental phase
Test
European Standard
Number of samples
Specimens
1°
Size distribution Apparent bulk density Physical, chemical and mineralogical composition
EN 1015-1 [21] Cahier 2669-4 [22] –
6
Sand and recycled aggregate Cement and recycled aggregate Recycled aggregates
2°
Consistence by flow table Bulk density Dry bulk density Dynamic modulus of elasticity Ultra-sound pulse velocity Flexural and compressive strengths Water absorption by capillarity Susceptibility to cracking Drying Open porosity Magnifying glass observation
EN 1015-3 [23] EN 1015-6 [24] EN 1015-10 [25] EN 14,146 [26] Fe Pa 43 [27] EN 1015-11 [28] EN 1015-18 [29] – EN 16322 [30] NP EN 1936 [31] –
2 3 3 3 1 3 3 2 3 3
Fresh mortar Fresh mortar Hardened mortar Hardened mortar Hardened mortar Hardened mortar Hardened mortar Brick with a layer of mortar Hardened mortar Hardened mortar Hardened mortar
3°
Air content Shrinkage Water vapour permeability Artificial ageing test Permeability to water under pressure Adherence strength
EN 1015-7 [32] Cahier 2669 [22] EN 1015-19 [33] EN 1015-21 [34] EN 1015-21 [34] EN 1015-12 [35]
2 3 2 2 2 2
Fresh mortar Hardened mortar Hardened mortar Brick with a layer of mortar Brick with a layer of mortar Brick with a layer of mortar
Table 7 Consistency of the mortars tested. Mortar
Consistency (mm)
Water/binder ratio
REF RCA10 RCA15 RCA20 MRA10 MRA15 MRA20
159.5 161.5 158.5 159.0 159.0 160.0 162.0
1.12 1.01 0.99 0.96 0.97 0.96 1.00 Fig. 2. Bulk density of the mortars tested.
The incorporation of 20% of RCA maintains the same trends. However, the mortar with 20% of MRA demanded more water to achieve the same consistency. This was probably because MRA have a higher specific surface area due to the increase of fine content. Therefore, more water was required for the cement hydration reactions and also to lubricate the aggregate’s surface. Nevertheless, all the modified mortars obtained lower water/ binder ratio for the same workability than that of reference mortar. The increase of fines improved the plasticity of the mortars. These results followed the trend found by Selmo and Miranda [20], Silva et al. [8], Braga et al. [14], Oliveira et al. [15], Jochem et al. [19], Farinha et al. [16] and Farinha et al. [18]. Those authors noticed that the increase of fine aggregate’ incorporation reduced the water required to have the same consistency. 3.1.2. Bulk density of fresh mortars The fresh bulk density increased when recycled concrete aggregate was incorporated, although the concrete fines presented a lower bulk density than river sand. This was due to the filler effect and the reduction of water content in the mortar. On the other hand, the incorporation of the recycled mixed aggregate reduced the bulk density of fresh mortar compared to the reference mortar. Both wastes have a lower particle bulk density in comparison with sand (see Section 2.1). Therefore, there are two effects that influence the mortars’ bulk density: the bulk density of the particles and the filler effect. In the case of RCA, the filler effect had more influence than the particles’ bulk density and resulted in a heavier mortar. In the incorporation of MRA, the particles’ bulk density seemed to have more influence in mortars’ bulk density. Results are presented in Fig. 2.
Braga et al. [14] and Farinha et al. [16] obtained results similar to RCA’s with the incorporation of fine concrete and sanitary ware aggregates, respectively. Conversely, when fine ceramics aggregate was incorporated in mortars a decrease in the fresh bulk density was observed [8]. Therefore, the nature of the waste has influenced the bulk density of the mortars. 3.1.3. Dry bulk density of hardened mortars The results of the dry bulk density of hardened mortars at 28 and 90 days are presented in Fig. 3. They followed the same trend as in the fresh state, at both ages under analysis. According to those results, mortars properties were related to the nature of the recycled aggregate. The incorporation of RCA increased the dry bulk density of the mortar compared to the plain
Fig. 3. Dry bulk density of the mortars tested.
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mortar. This was due to a filler effect, in contrast with the MRA incorporation, which showed a decrease in dry bulk density. For both aggregate, the dry bulk density increased as the RA content increased. Also, the results at 90 days showed an increase, compared to those at 28 days. 3.1.4. Dynamic modulus of elasticity of hardened mortars The modulus of elasticity measures the mortars ability to absorb deformations [2]. A rendering mortar must support the loading applied without cracking. The dynamic modulus of elasticity test was determined at 28 and 90 days and the results are presented in Fig. 4. The incorporation of RCA and MRA increased the modulus of elasticity, in comparison with the one presented by the reference mortar. This was due to the filler effect and to the late hydration of non-hydrated cement residues. The filler increased the compactness of the mortars, decreasing their deformability, which results in a higher modulus of elasticity. MRA incorporation presented a less significant change in this property. However, mortars with RCA obtained a substantial increase. The highest increase occurred for RCA20, which had a 47% higher modulus than the conventional mortar, at 90 days. Only the modified mortar MRA20 had a reduction of the modulus of elasticity (-6%), probably due to the high porosity of this mortar, in comparison with the remaining ones. An increase in modulus of elasticity with incorporation of fines was also found by other authors when fine concrete, glass, sanitary ware and CDW were incorporated [14–16,19]. Contrary to this trend, Silva et al. [8] found a decrease in modulus of elasticity when 10% of fine ceramics in mortars were incorporated. A decrease of modulus of elasticity from 28 to 90 days was also noticed. This decrease is consistent with the decrease of mechanical strengths, verified and discussed below.
Fig. 5. Ultrasound pulse velocity of the mortars tested.
3.1.6. Flexural and compressive strength of hardened mortars The flexural and compressive strength tests were performed at 28 and 90 days. The results of these tests are presented in Figs. 6 and 7. The incorporation of fine recycled aggregate provided the mortars with a better mechanical performance. Both the flexural and compressive strength increased in all modified mortars relative
to the reference mortar. The incorporation of RCA led to higher flexural and compressive strength in comparison with MRA mortars. Three factors may explain these results: a filler effect, the lower water content in the modified mortars and the possible presence of non-hydrated cement that completed hydration during the preparation of the new mortars. The fine aggregate fills the voids between the sand aggregates, which increased the compactness of the mortars. Consequently, the modified mortars presented higher mechanical strength. At 28 days, RCA20 obtained the highest values for mechanical strengths, presenting a flexural strength 137% higher than that of the reference mortar and a compressive strength 208% higher, at the same age. For both ages, a higher RCA content increased the mechanical strengths. Whereas the incorporation of MRA up to 15% also increased the mechanical strength, it decreased from then on. This is because this higher incorporation led to an increase of porosity. A decrease of flexural and compressive strengths from 28 days to 90 days was found. A similar behaviour was noticed by other authors in rendering mortars [15 16]. The decrease of strengths can be due to internal micro-cracking of the specimens [16]. The type of waste and the incorporation percentage influence the improvements on mechanical properties. Several studies [8,15–17,19] found that the incorporation of fines increased the mechanical strengths, as shown in Fig. 7. According to the results presented in Fig. 8, the incorporation of 20% fine sanitary ware had the highest increase in flexural strength [16]. However, RCA20 also presented a significant improvement in this property. A significant decrease of strengths from 28 days to 90 days was noticed. RCA20 had a decrease of about 32% and MRA20 presented a reduction of 42% compared to the control mortar. A similar behaviour was noticed by other authors [15,16]. A possible microcracking of the mortars was pointed out as the main reason for that possible reduction of strengths.
Fig. 4. Dynamic modulus of elasticity of the mortars tested.
3.1.7. Water absorption by capillarity of hardened mortars The results of the water absorption by capillarity tests, at 28 days, are presented in Fig. 9. The capillary coefficient was calculated using the mass of water absorbed between 10 and 90 min, per area unit and square roof of time. The coefficient indicates the rate of water absorption by capillarity, in the first minutes of test. The capillary coefficient and the total water absorption decreased with the incorporation of fine recycled aggregate, relative to the reference mortar. This was, once more, due to the filler effect that reduced the porosity of the mortars, probably decreasing the volume of capillary pores and had as a consequence an improvement of the water absorption behaviour.
3.1.5. Ultra-sound pulse velocity of hardened mortars The ultra-sound pulse velocity test was performed at 28 and 90 days and the results are in Fig. 5. The results agreed with those of the modulus of elasticity. As more RA were incorporated, was the ultra-sound pulse velocity increased. MRA20 was the only mortar that showed a decrease when compared to the reference mortar. However, it was a slight decrease of about 3.25%, at 90 days. RCA20 had the highest increase (15%) in comparison with the control mortar.
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A trend of decreasing capillary coefficient as increasing the RCA content was observed. For MRA, the opposite occurred, i.e. a higher incorporation led to a higher capillary coefficient, confirming the hypothesis that an increase of porosity due to MRA may overlap the filler effect for high levels of incorporation. Silva et al. [8], Braga et al. [14], Oliveira et al. [15], Farinha et al. [16] and Kabeer and Vyas [17] found that the incorporation of ceramics, concrete, glass, sanitary ware or marble fine waste also decreased the capillary coefficient. These authors found out that the lowest capillarity coefficient corresponded to the highest percentage of incorporation of each waste.
Fig. 6. Flexural strength of the mortars tested.
Fig. 7. Compressive strength of the mortars tested.
Fig. 8. Comparison of the flexural strength of the mortars tested, at 28 days.
Fig. 9. Water absorption by capillarity of the mortars tested.
3.1.8. Drying Immediately after the end of the water absorption by capillarity test the drying test began. The drying test determines the drying time of the mortars. Figs. 10 and 11 present the drying curves of all the mortars under analysis, per square root of time. Modified mortars have smaller capillary pores, in comparison with the REF mortar, due to a filler effect, which probably hinders water evaporation. Although the REF mortar absorbed the water by capillarity faster, the water was also able to evaporate faster. However, the change found in the drying curves of these mortars was not very significant. Modified mortars presented a decrease in the evaporation rate, due to a filler effect and smaller pores. The results showed that MRA20 and RCA10 obtained the best performance compared to the other modified mortars. It was noticed that the nature of the waste can differently influence the drying time of the mortars. 3.1.9. Open porosity The volume of interconnect pores in a mortar can be estimated by the open porosity test. The results are shown in Fig. 12. The type of recycled aggregate led to a different behaviour. It was found that the incorporation of RCA decreased the open porosity, meaning that the total volume of interconnected pores is lower than REF’s. The mortar with 20% of RCA waste presented a decrease of porosity of 10%, in comparison with the reference mortar. The incorporation of MRA in mortars was characterized by a similar open porosity comparing with the reference mortar, around 22%. The major difference found was in the MRA with 20% that presented an increment of 3% of open porosity. The filler effect of the particles was more efficient with the incorporation of RCA than with MRA, which resulted in different open porosities of the RCA mortars and MRA mortars. Possibly, a higher open porosity of the aggregate MRA compared with both RCA and natural sand can explain this inversion of results. Farinha et al. [16] found the same trend for sanitary ware fine aggregates’ incorporation. The lowest value for open porosity occurred for 20% of sanitary ware incorporation. In this research,
Fig. 10. Drying of the mortars tested with recycled mixed aggregate.
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formance compared to the others. However, taking into account that the main objective of this research was related to the recycling of CDW, it was decided to proceed to the third phase of the tests with RMA15. Despite slightly lower performance in some properties, the decreases are not very significant and it is possible to increase the amount of recycled aggregate used.
3.2. Second experimental phase
Fig. 11. Drying of the mortars tested with recycled concrete aggregate.
Fig. 12. Open porosity of the mortars tested.
RCA20 presented a lower open porosity, compared to the conventional mortar, by 10.5%. 3.1.10. Susceptibility to cracking To observe potential cracks, a layer of mortar 2 cm thick was applied on ceramic bricks and visually evaluated for 3 months. RCA20 was the only specimen that showed visible cracks. None of the other mortars presented any signs of cracking. High shrinkage and high stiffness can explain the tendency for micro-cracking of RCA20. 3.1.11. Magnifying glass observation All the specimens were observed under an electronic magnifying glass, in order to verify whether internal micro-cracking occurred. In Fig. 13, some images, at 90 days, are presented. In all the mortars, it was possible to observe internal micro-cracking. The micro-cracking pattern and crack widths increased with the recycled aggregate’s incorporation ratio. The modified mortar RCA20 had the greatest micro-cracking pattern. These results explain the decrease in mechanical strengths and dynamic modulus of elasticity between 28 days and 90 days. 3.1.12. Selection for the next phase Two modified mortars were chosen to be to analyse in depth, one for each recycled aggregate. This choice was based on the results of the previous tests. Table 8 presented the percent variations in the parameters under analyses, which were calculated relative to the results of the reference mortar. Mortars with the best performance in each test are shaded in green. Regarding the incorporation of fine recycled concrete aggregate, the modified mortar RCA20 presented the best performance in the previous phase. In the case of mortars produced with fine recycled mixed aggregate, it has found that MRA10 presented a better per-
3.2.1. Air content of fresh mortars An increase of air content can contribute to an improvement of workability. However, in the hardened state, it can lead to decreased mechanical strength and adhesion of the mortar to the substrate. According to the results presented in Table 9, MRA15 obtained an increase of approximately 95% of the air content compared to the reference mortar. This result may explain the decrease of the bulk density of all mortars with this type of aggregate. For RCA20, an increase of about 25% was found in comparison with the control mortar. Oliveira et al. [15] detected the same behaviour. This trend could be attributed to the shape of the aggregate particles.
3.2.2. Shrinkage The free shrinkage test was carried out up to 90 days, since it is a parameter that tends to stabilize over time. This test may predict the behaviour of each mortar in the long-term. It was found that the largest dimensional variation occurred at early ages, as shown in Fig. 14. The modified mortars present a significant increase in shrinkage compared to reference mortar. At 90 days, RCA20 and MRA15 obtained an increase up to 65 and 45%, respectively. These results may lead to a higher probability of cracking. This behaviour may be explained by the increase of the capillary pores stress and the increase of the modified mortars’ cementitious content. Recycled aggregate presented old hardened mortar adhered to the particles, leading to a high content of cement, which may be incompletely hydrated.
3.2.3. Water vapour permeability of hardened mortars Water in the wall, whether of the construction work phase or due to leakage through the cracks and big pores of the coatings or to absorption from the exterior by the coatings, should not remain in inside them. In addition, the water vapour formed inside the constructions should also come out. Therefore, the permeability to water vapour is a very important property of mortars. Mortars with a high permeability to water vapour facilitate drying of the coating and prevent the condensation of water on their surface, avoiding problems inherent to the phenomenon of interior condensations. The results are presented in Table 10. The incorporation of 20% RCA led to a decrease of 11% in water vapour permeability. However, the addition of 15% MRA did not significantly influence the permeability of the mortar. Thus, MRA mortar presents a water vapour release identical to that of the reference mortar. In fact, this mortar has an open porosity similar to that of the reference. Silva et al. [8], Braga et al. [14] and Farinha et al. [16] also evaluated this property. The authors found out that the addition of fine wastes was responsible for the decrease of water vapour permeability, similar to that observed for the addition of 20% RCA. However, Jochem et al. [19] concluded that mortars produced with recycled aggregates from CDW with a fine incorporation of 24% have higher permeability than mortars with the same additions but formulated with aggregates of crushing of natural granite aggregates.
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Fig. 13. Mortars observed at 700% (7) magnifying glass observation.
Table 8 Results of the tests of the second experimental phase and selection of the mortars with better performance.
Table 9 Air content of the mortars tested. Mortar
Air content (%)
REF RCA20 MRA15
7.13 8.88 13.88
Table 10 Water vapour permeability of the mortar tested. Mortar
Water vapour permeability (ng/(m.s.Pa))
REF RCA20 MRA15
17.52 15.67 17.21
Fig. 15. Permeability to water under pressure of the mortars tested. Fig. 14. Dimensional variation of the mortars tested.
3.2.4. Evaluation of durability by the artificial accelerated ageing test The artificial ageing process consisted of heat-freeze and humidity-freeze cycles. The heat-freeze cycle resulted from the incidence of an infrared radiation on the surface of the specimens for 8 h ± 15 min. The specimens reached a temperature of 60 ± 2 °C. After that period, the specimens were submitted to 15 ± 1 °C in a freezer for 15 h ± 15 min. Eight cycles of heat-freeze were performed. After these cycles, the specimens were submitted to another eight humidity-freeze cycles. Each cycle consisted of 8 h ± 15 min of water sprinkling, at 20 ± 2 °C. After that period,
the specimens were submitted to 15 ± 1 °C in the freezer for 15 h ± 15 min. After the eight cycles of heat-freeze and humidityfreeze, the specimens were maintained under controlled temperature and humidity of 20 ± 2 °C and 65 ± 5% for two weeks. The permeability to water under pressure and adherence strength were analysed before and after these cycles. 3.2.5. Permeability to water under pressure The water permeability under pressure test measures the amount of water under pressure absorbed by a mortar per unit area. The results are presented in Fig. 15.
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S. Jesus et al. / Construction and Building Materials 229 (2019) 116844 Table 11 Adherence to the substrate of the mortars tested. Mortar
REF RCA20 MRA15
Before ageing
After ageing
Adherence (MPa)
Predominant type of rupture
Standard deviation (MPa)
Adherence (MPa)
Predominant type of rupture
Standard deviation (MPa)
0.54 0.87 0.66
A/B A/C A
0.11 0.07 0.1
0.55 0.66 0.64
B A A/B
0.06 0.05 0.07
Before and after accelerated ageing, a decrease in permeability to water under pressure was noticed from the incorporation of fine aggregates. However, this reduction was more significant after ageing. This decrease in the permeability of mortar with MRA corresponded to 25% and the incorporation of RCA presented a reduction of 39% compared to the reference mortar. The ageing caused an increase of the permeability to water under pressure in all the studied mortars, which was more significant in the reference mortar. A decrease in the permeability value to water under pressure is considered positive, since it is an indication that water in liquid state has greater difficulty in penetrating the mortar. Thus, it is concluded that both modified mortars in this study showed an improvement. Silva et al. [8], Oliveira et al. [15] and Farinha et al. [16] concluded that the addition of red ceramics, glass and sanitary ware, respectively, allowed reducing the permeability to water under pressure of these mortars at 28 days, as well as after accelerated ageing. Additionally, Farinha et al. [16] found an increase in permeability after ageing. However, Oliveira et al. [15] reported that the climatic cycles improved the behaviour of mortars, i.e. the mortars with recycled aggregates had a lower permeability to liquid water. 3.2.6. Adherence strength of hardened mortars The adherence strength test results are presented in Table 11. It was found that the incorporation of fine recycled aggregate increased the adherence strength, before and after ageing, in comparison with the REF mortar. This was due to the higher mechanical strengths, when compared with REF’s. Other authors [8,15–17] found the same trend: the incorporation of fine aggregates increased the adherence strength of the modified mortars. This is attributed to a higher fine content that provides a stronger interface between the substrate and the coating, by the substrate’s suction of fines and water from the rendering. At 28 days, MRA15 showed an increase of 22% compared to the control mortar. RCA20 obtained a higher increase of about 61%. A factor for this different trend could be the partial filling of the substrate’s pores with MRA’s fines, in substitution of part of the cement, hence reducing the adherence strength. Although after ageing all the mortars changed the predominant type of rupture, only RCA20 showed a significant decrease in adherence strength. This could be related to micro-cracking inside the mortar. 4. Conclusions This paper investigates the performance of rendering mortars with incorporation of recycled aggregate from construction and demolition waste (CDW). Two types of recycled aggregate were used as filler: recycled concrete aggregate (RCA) and mixed recycled aggregate (MRA), in percentages of 0%, 10%, 15% and 20%. The results of all the properties tested showed that the incorporation improved the mechanical and water behaviour of the modified mortars. It was found that the incorporation of RCA and MRA influenced mortars’ performance differently, thus the type of wastes used have their own trends. Mortars with RCA exhibited
a better performance when compared to those with incorporation of MRA, especially concerning mechanical strength, water absorption by capillarity, water permeability under pressure and adherence strength. Regarding mortars with MRA, they also presented better results compared to the reference mortar. In the third experimental stage, RCA20 and MRA15 were selected for a deeper study. These modified mortars had a better performance in adherence strength and water permeability under pressure compared to the plain mortar. However, RCA20 and MRA15 showed an increase of 65% and 45%, respectively, in shrinkage. In conclusion, the incorporation of both types of fine recycled aggregates in mortars enhanced their properties, concerning mechanical and water behaviour, while providing a proper disposal to the waste generated. However, the increase of shrinkage and correspondent trend for micro-cracking is a drawback and solutions to minimize it will be studied in further studies. Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. References [1] Eurostat, ‘‘Waste statistics in Europe,” 2019. [2] R.V. Silva, J. De Brito, R.K. Dhir, Performance of cementitious renderings and masonry mortars containing recycled aggregates from construction and demolition wastes, Constr. Build. Mater. 105 (2016) 400–415. [3] L.F.R. Miranda, S.M.S. Selmo, CDW recycled aggregate renderings: Part II Analysis of the effect of materials finer than 75 lm under accelerated aging performance, Constr. Build. Mater. 20 (9) (2006) 625–633. [4] I. Martínez, M. Exteberria, E. Pavón, N. Díaz, Influence of demolition waste fine particles on the properties of recycled aggregate masonry mortar, Int. J. Civ. Eng. 16 (9) (2018) 1213–1226. [5] R.L.S. Ferreira, M.A.S. Anjos, A.K.C. Nóbrega, J.E.S. Pereira, E.F. Ledesma, The role of powder content of the recycled aggregates of CDW in the behaviour of rendering mortars, Constr. Build. Mater. 208 (2019) 601–612. [6] C.C. Fan, R. Huang, H. Hwang, S.J. Chao, The effects of different fine recycled concrete aggregates on the properties of Mortar, Materials (Basel) 8 (5) (2015) 2658–2672. [7] J.R. Jiménez, J. Ayuso, M. López, J.M. Fernández, J. De Brito, Use of fine recycled aggregates from ceramic waste in masonry mortar manufacturing, Constr. Build. Mater. 40 (2013) 679–690. [8] J. Silva, J. de Brito, R. Veiga, Incorporation of fine ceramics in mortars, Constr. Build. Mater. 23 (1) (2009) 556–564. [9] I. Martínez, M. Etxeberria, E. Pavón, N. Díaz, Influence of demolition waste fine particles on the properties of recycled aggregate masonry mortar, Int. J. Civ. Eng. 16 (9) (2018) 1213–1226. [10] E.F. Ledesma et al., Effect of powdered mixed recycled aggregates on bedding mortar properties, Eur. J. Environ. Civ. Eng. 8189 (2016) 1–17. [11] J. de Brito, F. Agrela, R.V. Silva, Construction and demolition wasteNew Trends in Eco-efficient and Recycled Concrete, Elsevier Ltd, 2019. [12] J. De Brito, R. Silva, Current status on the use of recycled aggregates in concrete: where do we go from here?, RILEM Tech Lett. 1 (March) (2016) 1. [13] F. Rodrigues, M.T. Carvalho, M.F. Pereira, J. De Brito, Physical and chemicalmineralogical characterization of fine recycled aggregates from construction and demolition waste, J. Cleaner Production 4 (November 2015) (2011). [14] M. Braga, J. De Brito, R. Veiga, Incorporation of fine concrete aggregates in mortars, Constr. Build. Mater. 36 (2012) 960–968. [15] R. Oliveira, J. De Brito, R. Veiga, Incorporation of fine glass aggregates in renderings, Constr. Build. Mater. 44 (2013) 329–341. [16] C. Farinha, J. de Brito, R. Veiga, Incorporation of fine sanitary ware aggregates in coating mortars, Constr. Build. Mater. 83 (May) (2015) 194–206.
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[17] K.I.S.A. Kabeer, A.K. Vyas, Utilization of marble powder as fine aggregate in mortar mixes, Constr. Build. Mater. 165 (2018) 321–332. [18] C.B. Farinha, J. de Brito, R. Veiga, Assessment of glass fibre reinforced polymer waste reuse as filler in mortars, J. Clean. Prod. 210 (2019) 1579–1594. [19] L.F. Jochem, J.C. Rocha, M. Cheriaf, Estudo Comparativo entre Argamassas de Revestimento com Agregado Reciclado de RCD e com Agregado de Britagem, Conference: Encontro Latinoamericano de Edificações e Comunidades Sustentáveis, 2013 (in Portuguese). [20] L.F.R. Miranda, S.M.S. Selmo, CDW recycled aggregate renderings: Part I – Analysis of the effect of materials finer than 75 lm on mortar properties, Constr. Build. Mater. 20 (9) (2006) 615–624. [21] EN 1015-1, Methods of test for mortar for masonry – Part 1: Determination of particle size distribution (by sieve analysis), 1998. [22] Cahier 2669-4, Certification CSTB des enduits monocouches d’imperme´abilisation, Modalite´s d’essais, 1993. [23] EN 1015-3, Methods of test for mortar for masonry – Part 3: Determination of consistence of fresh mortar (by flow table), 1999. [24] EN 1015-6, Methods of test for mortar for masonry – Part 6: Determination of bulk density of fresh mortar, 1998. [25] EN 1015-10, Methods of test for mortar for masonry – Part 10: Determination of dry bulk density of hardened mortar, 1999. [26] EN 14146, Natural stone test methods. Determination of the dynamic elastic modulus of elasticity (by measuring the fundamental resonance frequency), 2004.
[27] FE Pa 43, Test of evaluation of the mechanical characteristics by ultra-sounds (in Portuguese), 2010. [28] EN 1015-11, Methods of test for mortar for masonry – Part 11: Determination of flexural and compressive strength of hardened mortar, 1999. [29] EN 1015-18, Methods of test for mortar for masonry – Part 18: Determination of water absorption coefficient due to capillary action of hardened mortar, 2002. [30] EN 16322, Conservation of Cultural Heritage – Tests methods – Determination of drying properties. European Committee for Standardization (CEN), 2013. [31] EN 1936, Natural stone test methods. Determination of real density and apparent density and total and partial open porosity, 2007. [32] EN 1015-7, Methods of test for mortar for masonry – Part 7: Determination of air content of fresh mortar, 1998. [33] EN 1015-19, Methods of test for mortar for masonry – Part 19: Determination of water vapour permeability of hardened rendering and plastering mortars, 1998. [34] EN 1015-21, Methods of test for mortar for masonry – Part 21: Determination of the compatibility of one-coat rendering mortars with substrates, 2002. [35] EN 1015-12, Methods of test for mortar for masonry – Part 12: Determination of adhesive strength of hardened rendering and plastering mortars on substrates, 2000. [36] C.B. Farinha, J. de Brito, J.M. Fernández, J.R. Jiménez, A.R. Esquinas, Wastes as aggregates, binders or additions in mortars: Selecting their role based on characterization, Materials (Basel) (2018).
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Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat
Rendering mortars with incorporation of very fine aggregates from construction and demolition waste Sara Jesus a, Cinthia Maia a,b, Catarina Brazão Farinha a,b, Jorge de Brito a,⇑, Rosário Veiga b a b
CERIS, Instituto Superior Técnico, University of Lisbon, Av. Rovisco Pais, 1, 1049-001 Lisbon, Portugal National Laboratory for Civil Engineering, Av. do Brasil 101, 1700-066 Lisbon, Portugal
h i g h l i g h t s CDW as a filler incorporation improved the workability of the mortars. Mechanical strengths were improved by the incorporation of RCA and MRA from CDW. Water absorption was reduced by the incorporation of RCA and MRA. The incorporation of RCA and MRA reduced the deformability of the mortars. Modified mortars presented significant microcracking.
a r t i c l e
i n f o
Article history: Received 2 May 2019 Received in revised form 1 August 2019 Accepted 1 September 2019
Keywords: Render Mortar Filler CDW Reuse Sustainability
a b s t r a c t The intense rate of construction and demolition waste generation (CDW) over the years should boost recycling. The use of CDW as constituents of cementitious composites has been considered a feasible alternative to dumping. This paper presents a study of the behaviour of cementitious renderings incorporating very fine recycled aggregates from two types of CDW. Only particles of recycled aggregates below 0.149 mm were used as filler, hereinafter referred as recycled concrete aggregate (RCA) and mixed recycled aggregate (MRA). The incorporation’ percentages used were 0%, 10%, 15% and 20% of natural aggregates’ volume. Several tests have been carried out, in order to evaluate the mortars in terms of mechanical strength, workability, water absorption, dimensional instability and water vapour permeability. The experimental programme consisted in three consecutive phases, in which the mortars that presented the best performances were selected for a deeper analysis of their features. The test results showed that modified mortars had a better behaviour in most of tests compared with the reference mortar (with no CDW). Mortars with incorporation of 20% of RCA and 15% of MRA presented the best performance. Ó 2019 Elsevier Ltd. All rights reserved.
1. Introduction As the population continues to grow, there is also a subsequent development of economic sectors and therefore a significant increase of energy and natural resources’ consumption. Construction and demolition waste (CDW) has been considered a relevant environmental issue. According to Eurostat [1], the amount of CDW generated in 2014 was 868 million tonnes. In order to encourage the use of recycled aggregates, the Waste Framework Directive 2008/98/EC of the European Parliament established a target for all the member states of European Union: at least 70% of reduction, reuse and recycling of CDW by 2020. ⇑ Corresponding author. E-mail addresses: [email protected] (S. Jesus), cinthiamaia@tecnico. ulisboa.pt (C. Maia), [email protected] (C. Brazão Farinha), jb@civil. ist.utl.pt (J. de Brito), [email protected] (R. Veiga). https://doi.org/10.1016/j.conbuildmat.2019.116844 0950-0618/Ó 2019 Elsevier Ltd. All rights reserved.
To accomplish this aim, there have been several researches focused on the use of recycled aggregates. One of the viable solutions is the replacement of natural sand for recycled aggregate in mortar production [2–10]. Notwithstanding some shortcomings of recycled aggregate such as high heterogeneity, high water absorption and presence of contaminants [2,11–13], studies have reported that fine recycled aggregate could result in improvements on the performance of mortars, with a proper production process and pre-treatments. Although several works have been published about the use of recycled aggregate as replacement of natural sand, the incorporation of recycled aggregate from CDW as filler has limited studies. Several researches focused on the behaviour of mortars with incorporation of fine recycled aggregates of construction waste such as ceramics, concrete, glass, sanitary ware, marble powder and glass fibre reinforced polymer [8,14–18]. These studies allowed positive
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prospects concerning the use of the finest material of recycled aggregates. Regarding the incorporation of fine recycled aggregate from CDW, a few works presented general results [10,19,20]. The incorporation of the fine particles provided improvements in the mortar performance, concerning properties such as workability, mechanical strength, water absorption and adherence strength [8,14,15–20]. In this work, mortars with non-structural functions with incorporation of CDW and low cement contents, hence very significantly influenced by the aggregates’ characteristics, were studied. Several functional and durability characteristics were assessed, such as shrinkage, cracking behaviour, modulus of elasticity, durability and water vapour permeability that were not determined in previous studies for these kinds of wastes. Ledesma et al. [10] investigated the replacement of fine natural sand by fine recycled aggregate in masonry mortars. Therefore, in this study, the performance of rendering mortars is analysed, in order to develop a new cementitious rendering. Modified mortars reduced the water requirement to maintain similar consistency [8,14–20]. This is due to the filler effect as the fines fill the voids within the mortar structure, decreasing the amount of water required to hydrate and lubricate the aggregates [18]. Mechanical strengths, as flexural, compressive and adherence strength, are significantly improved compared with the reference mortars, when filler wastes are introduced. The incorporation of these particles produces more compact mortars, due to the filler effect [8,14–20]. Mortars with fine waste presented a better adherence strength than the mortars with only sand as aggregate [8,14–20]. It was found that the incorporation of fines enhanced the mechanical behaviour of the mortars, and this could be explained by the cement, water and fines that are partially absorbed by the substrate and develop a stronger bond. The compactness of mortar also influences the water absorption. The incorporation of fine waste material provided a smaller water absorption of modified mortars when compared to plain mortar [8,14–20]. This is due to a denser microstructure, linked to the filler effect. Even though the fines provide a greater compactness of the modified mortars, which results in many advantages, the authors reported some drawbacks such as higher modulus of elasticity and higher susceptibility to cracking [8,14–20]. The increase of the modulus of elasticity implies a stiffer mortar, which means a lower capacity to deform under the action of stresses from loading. This can lead to internal and external cracking in the modified mortars. The aim of this work is to contribute to the study of an alternative to natural aggregates, using the finest material of recycled aggregates from construction and demolition waste. The main objective of this study is to boost the use of this waste in cementitious materials in non-structural applications, namely coatings, presenting many advantages regarding mechanical and water behaviour. Different characteristics such as shrinkage, crack behaviour and durability were assessed, in order to examine the possibility of significant drawbacks that could hinder the feasibility of application. The new applications contribute to providing a better disposal of the wastes. This research analyses the use of two types of recycled aggregate: recycled concrete aggregate (RCA) and mixed recycled aggregate (MRA), in ratios of 0%, 10%, 15% and 20%. The mortar performance was evaluated in the fresh and hardened state.
2.1. Materials Modified mortars were produced with replacement of sand (in volume) with fine recycled aggregate (RCA and MRA) from CDW, at 10%, 15% and 20%. Only particles of recycled aggregates below 0.149 mm were used. RCA were made of mainly crushed concrete and MRA were composed of several CDW materials such as mortar, concrete, ceramics, plastic, glass, metals, gypsum and wood. The mortars were produced with: cement, river sand and fine recycled aggregate from CDW. The binder used was cement type CEM II/ B-L 32.5 N, from the Portuguese cement producer Secil. The natural sand was from the Tagus River and only particles below 2.38 mm were used. The recycled aggregates came from two Portuguese CDW recycling plants: RCD - Resíduos de Construção e Demolição SA (recycled concrete aggregates) and SGR Ambiente (recycled mixed aggregates). The type of recycled aggregate, degree of contamination and particles’ size were indicators for the selection. The recycled aggregates were purposely used without any additional processing, to preserve the properties inherent to the manufacturing process. The sand and recycled aggregates grading curves are presented in Fig. 1. It is noticed that river sand consists of about 0.73% of particles below 0.149 mm. In this research, the incorporation of filler intended to reach a ratio of particles below 0.149 mm of 10%, 15% and 20%. Since sand already presents 0.73% of the particles under this value, the incorporation of CDW was slightly smaller than reported, about 9.27%, 14.27% and 19.27%. However, in order to simplify, values of 10%, 15% and 20% were used to characterize the incorporation of recycled aggregate. The river sand presented a continuous grading curve, which leads to more compact mortars. Also, it was found that the recycled aggregate presented a higher content of fines compared to the sand, especially MRA that presented about 5% of particles below 0.149 mm. Through the apparent bulk density test, it was noticed that RCA and MRA presented apparent bulk density lower than that of the river sand. The test results are presented in Table 1. Recycled aggregates obtained from recycling plants of CDW are very heterogeneous, and therefore a meticulous characterization was carried out. Although the incorporation, in this research, was only of particles below 0.149 mm, physical, chemical and mineralogical tests were performed. Table 2 shows the composition of each recycled aggregate used. These results cannot be generalized, since waste materials depend on the type of construction and the constructive technology where they were used originally. Therefore, recycled aggregates’ properties vary over time and from place to place. Table 3 presents the detailed composition of the recycled aggregates. Although RA contains few contaminants, it could be found that this does not make its use unfeasible. The chemical analyses by FRX are presented in Table 4.
2. Experimental programme In order to evaluate the influence of the fine recycled aggregates from CDW, various standard tests used for the assessment of the performance of renderings were carried out.
Fig. 1. Particle size distribution of sand and recycled aggregates.
S. Jesus et al. / Construction and Building Materials 229 (2019) 116844
Table 1 Apparent bulk density of the constituents of the mortars produced. Constituents
Apparent bulk density (kg/m3)
Cement River sand RCA (0.149 mm) MRA (0.149 mm)
1030 1471 878 810
3
REF – Reference mortar 0% of incorporation; RCA10 – Mortar produced with 10% of RCA incorporation; RCA15 – Mortar produced with 15% of RCA incorporation; RCA20 – Mortar produced with 20% of RCA incorporation; MRA10 – Mortar produced with 10% of MRA incorporation; MRA15 – Mortar produced with 15% of MRA incorporation; MRA20 – Mortar produced with 20% of MRA incorporation.
2.2. Methods The experimental programme was divided in three phases:
Table 2 Composition of the recycled aggregates. Aggregate
Cementitious residues (%)
Ceramics (%)
Others (%)
RCA MRA
99.67 70.83
0.29 17.34
0.04 11.82
Table 3 Detailed composition of the recycled aggregates. Tests
RCA
MRA
Water soluble chlorides (%Cl) Total sulphurs (%SO3) Acid soluble sulphates (%SO3) Contaminants (%) Humus content
<0.010 0.1 0.3 0.3 Not detected
0.021 1.8 4.4 8.6 Not detected
Table 4 Chemical composition of the recycled aggregates. Elements (% in mass)
RCA
MRA
Al2O3 SiO2 P2O5 SO3 Cl K2O CaO TiO2 Fe2O3 ZnO PbO Others
3.59 39.71 0.00 1.64 0.02 1.18 52.52 0.29 1.01 0.01 0.002 0.018
3.90 55.27 0.19 9.37 0.10 2.08 26.42 0.43 2.12 0.08 0.01 0.03
The FRX analysis showed SiO2, CaO and Al2O3 as the major components of both recycled aggregates, which are related to natural aggregates, ceramics and hardened mortar residues. Also, in DRX analysis detected cementitious components, quartz and calcite in the recycled aggregates. Gypsum was found in the composition of MRA. These analyses may explain the differences in the mortars’ behaviour. All the mortars evaluated had the same volumetric ratio of 1:4 (binder: aggregate); the composition of the mortar mixes is described in Table 5. The mortars are specified as: Table 5 Composition of the mortar mixes (kg/m3). Mortar
REF RCA10 RCA15 RCA20 MRA10 MRA15 MRA20
Water
230 208 204 198 200 198 205
Cement
205.9 205.9 205.9 205.9 205.9 205.9 205.9
River sand
1177.1 1068.8 1010.0 951.1 1068.8 1010.0 951.1
Recycled aggregate Concrete
Mixed
– 64.6 99.7 134.9 – – –
– – – – 59.6 92.0 124.3
First experimental phase: characterisation of the components of the mortar - cement, sand and recycled aggregates; Second experimental phase: characterisation tests of all the mortars. Modified mortars with the most satisfactory results were selected for the final experimental phase; Third experimental phase: more specific tests for assessment of the performance of renders were carried out on the mortars (chosen from the previous experimental phase). The methods used in the tests are indicated hereinafter, in Table 6. To ensure an adequate workability and to improve the comparability of the mortars, the values of consistency were fixed in the spread range of 160 ± 3 mm. All specimens of hardened mortar were submitted to the same curing conditions, except in the ‘‘susceptibility to cracking”, ‘‘shrinkage” and ‘‘water vapour permeability” tests. The specimens for most of the tests, as specified by the European standards [21–35], were subjected to a relative humidity of 95 ± 5% and a temperature of 20 ± 2 °C for 2 days inside the moulds. After demoulding, the specimens were maintained in the same conditions for 5 more days. Afterwards, the specimens were submitted to a 65 ± 5% relative humidity until being tested. In the susceptibility to cracking and shrinkage tests, the specimens were submitted to a temperature of 23 ± 2 °C and relative humidity of 50 ± 5% until they were tested. In water vapour permeability tests, the specimens were maintained in a temperature of 23 ± 2 °C and relative humidity of 95 ± 5%. After demoulding, the relative humidity was 50 ± 5%.
3. Results and analysis 3.1. First experimental phase 3.1.1. Consistency of fresh mortars The consistency test quantifies the water content to be added to the mortar, in order to obtain a pre-defined fluidity of fresh mortar. The results are presented in Table 7. The incorporation of fine recycled aggregate up to 20% ratio decreases the water content to maintain the same workability, for both wastes incorporated. This reduction is due to the filler effect. The fine particles of recycled aggregate filled the empty voids between the larger particles of sand, decreasing the amount of water needed in the mix [18]. There are some characteristics of the wastes that tend to decrease the workability, as their water absorption [36], but the filler effect overlapped those effects and was responsible for a reduction of the water content. All the mortars have the same volumetric ratio and, therefore, the same binder content. As a consequence of the incorporation of recycled aggregate, the water/binder ratio decreases. The reduction of water needs and, as a consequence, the reduction of the water/binder ratio can indicate better mechanical behaviour of the mortar.
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Table 6 Methods used in the experimental campaign. Experimental phase
Test
European Standard
Number of samples
Specimens
1°
Size distribution Apparent bulk density Physical, chemical and mineralogical composition
EN 1015-1 [21] Cahier 2669-4 [22] –
6
Sand and recycled aggregate Cement and recycled aggregate Recycled aggregates
2°
Consistence by flow table Bulk density Dry bulk density Dynamic modulus of elasticity Ultra-sound pulse velocity Flexural and compressive strengths Water absorption by capillarity Susceptibility to cracking Drying Open porosity Magnifying glass observation
EN 1015-3 [23] EN 1015-6 [24] EN 1015-10 [25] EN 14,146 [26] Fe Pa 43 [27] EN 1015-11 [28] EN 1015-18 [29] – EN 16322 [30] NP EN 1936 [31] –
2 3 3 3 1 3 3 2 3 3
Fresh mortar Fresh mortar Hardened mortar Hardened mortar Hardened mortar Hardened mortar Hardened mortar Brick with a layer of mortar Hardened mortar Hardened mortar Hardened mortar
3°
Air content Shrinkage Water vapour permeability Artificial ageing test Permeability to water under pressure Adherence strength
EN 1015-7 [32] Cahier 2669 [22] EN 1015-19 [33] EN 1015-21 [34] EN 1015-21 [34] EN 1015-12 [35]
2 3 2 2 2 2
Fresh mortar Hardened mortar Hardened mortar Brick with a layer of mortar Brick with a layer of mortar Brick with a layer of mortar
Table 7 Consistency of the mortars tested. Mortar
Consistency (mm)
Water/binder ratio
REF RCA10 RCA15 RCA20 MRA10 MRA15 MRA20
159.5 161.5 158.5 159.0 159.0 160.0 162.0
1.12 1.01 0.99 0.96 0.97 0.96 1.00 Fig. 2. Bulk density of the mortars tested.
The incorporation of 20% of RCA maintains the same trends. However, the mortar with 20% of MRA demanded more water to achieve the same consistency. This was probably because MRA have a higher specific surface area due to the increase of fine content. Therefore, more water was required for the cement hydration reactions and also to lubricate the aggregate’s surface. Nevertheless, all the modified mortars obtained lower water/ binder ratio for the same workability than that of reference mortar. The increase of fines improved the plasticity of the mortars. These results followed the trend found by Selmo and Miranda [20], Silva et al. [8], Braga et al. [14], Oliveira et al. [15], Jochem et al. [19], Farinha et al. [16] and Farinha et al. [18]. Those authors noticed that the increase of fine aggregate’ incorporation reduced the water required to have the same consistency. 3.1.2. Bulk density of fresh mortars The fresh bulk density increased when recycled concrete aggregate was incorporated, although the concrete fines presented a lower bulk density than river sand. This was due to the filler effect and the reduction of water content in the mortar. On the other hand, the incorporation of the recycled mixed aggregate reduced the bulk density of fresh mortar compared to the reference mortar. Both wastes have a lower particle bulk density in comparison with sand (see Section 2.1). Therefore, there are two effects that influence the mortars’ bulk density: the bulk density of the particles and the filler effect. In the case of RCA, the filler effect had more influence than the particles’ bulk density and resulted in a heavier mortar. In the incorporation of MRA, the particles’ bulk density seemed to have more influence in mortars’ bulk density. Results are presented in Fig. 2.
Braga et al. [14] and Farinha et al. [16] obtained results similar to RCA’s with the incorporation of fine concrete and sanitary ware aggregates, respectively. Conversely, when fine ceramics aggregate was incorporated in mortars a decrease in the fresh bulk density was observed [8]. Therefore, the nature of the waste has influenced the bulk density of the mortars. 3.1.3. Dry bulk density of hardened mortars The results of the dry bulk density of hardened mortars at 28 and 90 days are presented in Fig. 3. They followed the same trend as in the fresh state, at both ages under analysis. According to those results, mortars properties were related to the nature of the recycled aggregate. The incorporation of RCA increased the dry bulk density of the mortar compared to the plain
Fig. 3. Dry bulk density of the mortars tested.
S. Jesus et al. / Construction and Building Materials 229 (2019) 116844
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mortar. This was due to a filler effect, in contrast with the MRA incorporation, which showed a decrease in dry bulk density. For both aggregate, the dry bulk density increased as the RA content increased. Also, the results at 90 days showed an increase, compared to those at 28 days. 3.1.4. Dynamic modulus of elasticity of hardened mortars The modulus of elasticity measures the mortars ability to absorb deformations [2]. A rendering mortar must support the loading applied without cracking. The dynamic modulus of elasticity test was determined at 28 and 90 days and the results are presented in Fig. 4. The incorporation of RCA and MRA increased the modulus of elasticity, in comparison with the one presented by the reference mortar. This was due to the filler effect and to the late hydration of non-hydrated cement residues. The filler increased the compactness of the mortars, decreasing their deformability, which results in a higher modulus of elasticity. MRA incorporation presented a less significant change in this property. However, mortars with RCA obtained a substantial increase. The highest increase occurred for RCA20, which had a 47% higher modulus than the conventional mortar, at 90 days. Only the modified mortar MRA20 had a reduction of the modulus of elasticity (-6%), probably due to the high porosity of this mortar, in comparison with the remaining ones. An increase in modulus of elasticity with incorporation of fines was also found by other authors when fine concrete, glass, sanitary ware and CDW were incorporated [14–16,19]. Contrary to this trend, Silva et al. [8] found a decrease in modulus of elasticity when 10% of fine ceramics in mortars were incorporated. A decrease of modulus of elasticity from 28 to 90 days was also noticed. This decrease is consistent with the decrease of mechanical strengths, verified and discussed below.
Fig. 5. Ultrasound pulse velocity of the mortars tested.
3.1.6. Flexural and compressive strength of hardened mortars The flexural and compressive strength tests were performed at 28 and 90 days. The results of these tests are presented in Figs. 6 and 7. The incorporation of fine recycled aggregate provided the mortars with a better mechanical performance. Both the flexural and compressive strength increased in all modified mortars relative
to the reference mortar. The incorporation of RCA led to higher flexural and compressive strength in comparison with MRA mortars. Three factors may explain these results: a filler effect, the lower water content in the modified mortars and the possible presence of non-hydrated cement that completed hydration during the preparation of the new mortars. The fine aggregate fills the voids between the sand aggregates, which increased the compactness of the mortars. Consequently, the modified mortars presented higher mechanical strength. At 28 days, RCA20 obtained the highest values for mechanical strengths, presenting a flexural strength 137% higher than that of the reference mortar and a compressive strength 208% higher, at the same age. For both ages, a higher RCA content increased the mechanical strengths. Whereas the incorporation of MRA up to 15% also increased the mechanical strength, it decreased from then on. This is because this higher incorporation led to an increase of porosity. A decrease of flexural and compressive strengths from 28 days to 90 days was found. A similar behaviour was noticed by other authors in rendering mortars [15 16]. The decrease of strengths can be due to internal micro-cracking of the specimens [16]. The type of waste and the incorporation percentage influence the improvements on mechanical properties. Several studies [8,15–17,19] found that the incorporation of fines increased the mechanical strengths, as shown in Fig. 7. According to the results presented in Fig. 8, the incorporation of 20% fine sanitary ware had the highest increase in flexural strength [16]. However, RCA20 also presented a significant improvement in this property. A significant decrease of strengths from 28 days to 90 days was noticed. RCA20 had a decrease of about 32% and MRA20 presented a reduction of 42% compared to the control mortar. A similar behaviour was noticed by other authors [15,16]. A possible microcracking of the mortars was pointed out as the main reason for that possible reduction of strengths.
Fig. 4. Dynamic modulus of elasticity of the mortars tested.
3.1.7. Water absorption by capillarity of hardened mortars The results of the water absorption by capillarity tests, at 28 days, are presented in Fig. 9. The capillary coefficient was calculated using the mass of water absorbed between 10 and 90 min, per area unit and square roof of time. The coefficient indicates the rate of water absorption by capillarity, in the first minutes of test. The capillary coefficient and the total water absorption decreased with the incorporation of fine recycled aggregate, relative to the reference mortar. This was, once more, due to the filler effect that reduced the porosity of the mortars, probably decreasing the volume of capillary pores and had as a consequence an improvement of the water absorption behaviour.
3.1.5. Ultra-sound pulse velocity of hardened mortars The ultra-sound pulse velocity test was performed at 28 and 90 days and the results are in Fig. 5. The results agreed with those of the modulus of elasticity. As more RA were incorporated, was the ultra-sound pulse velocity increased. MRA20 was the only mortar that showed a decrease when compared to the reference mortar. However, it was a slight decrease of about 3.25%, at 90 days. RCA20 had the highest increase (15%) in comparison with the control mortar.
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A trend of decreasing capillary coefficient as increasing the RCA content was observed. For MRA, the opposite occurred, i.e. a higher incorporation led to a higher capillary coefficient, confirming the hypothesis that an increase of porosity due to MRA may overlap the filler effect for high levels of incorporation. Silva et al. [8], Braga et al. [14], Oliveira et al. [15], Farinha et al. [16] and Kabeer and Vyas [17] found that the incorporation of ceramics, concrete, glass, sanitary ware or marble fine waste also decreased the capillary coefficient. These authors found out that the lowest capillarity coefficient corresponded to the highest percentage of incorporation of each waste.
Fig. 6. Flexural strength of the mortars tested.
Fig. 7. Compressive strength of the mortars tested.
Fig. 8. Comparison of the flexural strength of the mortars tested, at 28 days.
Fig. 9. Water absorption by capillarity of the mortars tested.
3.1.8. Drying Immediately after the end of the water absorption by capillarity test the drying test began. The drying test determines the drying time of the mortars. Figs. 10 and 11 present the drying curves of all the mortars under analysis, per square root of time. Modified mortars have smaller capillary pores, in comparison with the REF mortar, due to a filler effect, which probably hinders water evaporation. Although the REF mortar absorbed the water by capillarity faster, the water was also able to evaporate faster. However, the change found in the drying curves of these mortars was not very significant. Modified mortars presented a decrease in the evaporation rate, due to a filler effect and smaller pores. The results showed that MRA20 and RCA10 obtained the best performance compared to the other modified mortars. It was noticed that the nature of the waste can differently influence the drying time of the mortars. 3.1.9. Open porosity The volume of interconnect pores in a mortar can be estimated by the open porosity test. The results are shown in Fig. 12. The type of recycled aggregate led to a different behaviour. It was found that the incorporation of RCA decreased the open porosity, meaning that the total volume of interconnected pores is lower than REF’s. The mortar with 20% of RCA waste presented a decrease of porosity of 10%, in comparison with the reference mortar. The incorporation of MRA in mortars was characterized by a similar open porosity comparing with the reference mortar, around 22%. The major difference found was in the MRA with 20% that presented an increment of 3% of open porosity. The filler effect of the particles was more efficient with the incorporation of RCA than with MRA, which resulted in different open porosities of the RCA mortars and MRA mortars. Possibly, a higher open porosity of the aggregate MRA compared with both RCA and natural sand can explain this inversion of results. Farinha et al. [16] found the same trend for sanitary ware fine aggregates’ incorporation. The lowest value for open porosity occurred for 20% of sanitary ware incorporation. In this research,
Fig. 10. Drying of the mortars tested with recycled mixed aggregate.
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formance compared to the others. However, taking into account that the main objective of this research was related to the recycling of CDW, it was decided to proceed to the third phase of the tests with RMA15. Despite slightly lower performance in some properties, the decreases are not very significant and it is possible to increase the amount of recycled aggregate used.
3.2. Second experimental phase
Fig. 11. Drying of the mortars tested with recycled concrete aggregate.
Fig. 12. Open porosity of the mortars tested.
RCA20 presented a lower open porosity, compared to the conventional mortar, by 10.5%. 3.1.10. Susceptibility to cracking To observe potential cracks, a layer of mortar 2 cm thick was applied on ceramic bricks and visually evaluated for 3 months. RCA20 was the only specimen that showed visible cracks. None of the other mortars presented any signs of cracking. High shrinkage and high stiffness can explain the tendency for micro-cracking of RCA20. 3.1.11. Magnifying glass observation All the specimens were observed under an electronic magnifying glass, in order to verify whether internal micro-cracking occurred. In Fig. 13, some images, at 90 days, are presented. In all the mortars, it was possible to observe internal micro-cracking. The micro-cracking pattern and crack widths increased with the recycled aggregate’s incorporation ratio. The modified mortar RCA20 had the greatest micro-cracking pattern. These results explain the decrease in mechanical strengths and dynamic modulus of elasticity between 28 days and 90 days. 3.1.12. Selection for the next phase Two modified mortars were chosen to be to analyse in depth, one for each recycled aggregate. This choice was based on the results of the previous tests. Table 8 presented the percent variations in the parameters under analyses, which were calculated relative to the results of the reference mortar. Mortars with the best performance in each test are shaded in green. Regarding the incorporation of fine recycled concrete aggregate, the modified mortar RCA20 presented the best performance in the previous phase. In the case of mortars produced with fine recycled mixed aggregate, it has found that MRA10 presented a better per-
3.2.1. Air content of fresh mortars An increase of air content can contribute to an improvement of workability. However, in the hardened state, it can lead to decreased mechanical strength and adhesion of the mortar to the substrate. According to the results presented in Table 9, MRA15 obtained an increase of approximately 95% of the air content compared to the reference mortar. This result may explain the decrease of the bulk density of all mortars with this type of aggregate. For RCA20, an increase of about 25% was found in comparison with the control mortar. Oliveira et al. [15] detected the same behaviour. This trend could be attributed to the shape of the aggregate particles.
3.2.2. Shrinkage The free shrinkage test was carried out up to 90 days, since it is a parameter that tends to stabilize over time. This test may predict the behaviour of each mortar in the long-term. It was found that the largest dimensional variation occurred at early ages, as shown in Fig. 14. The modified mortars present a significant increase in shrinkage compared to reference mortar. At 90 days, RCA20 and MRA15 obtained an increase up to 65 and 45%, respectively. These results may lead to a higher probability of cracking. This behaviour may be explained by the increase of the capillary pores stress and the increase of the modified mortars’ cementitious content. Recycled aggregate presented old hardened mortar adhered to the particles, leading to a high content of cement, which may be incompletely hydrated.
3.2.3. Water vapour permeability of hardened mortars Water in the wall, whether of the construction work phase or due to leakage through the cracks and big pores of the coatings or to absorption from the exterior by the coatings, should not remain in inside them. In addition, the water vapour formed inside the constructions should also come out. Therefore, the permeability to water vapour is a very important property of mortars. Mortars with a high permeability to water vapour facilitate drying of the coating and prevent the condensation of water on their surface, avoiding problems inherent to the phenomenon of interior condensations. The results are presented in Table 10. The incorporation of 20% RCA led to a decrease of 11% in water vapour permeability. However, the addition of 15% MRA did not significantly influence the permeability of the mortar. Thus, MRA mortar presents a water vapour release identical to that of the reference mortar. In fact, this mortar has an open porosity similar to that of the reference. Silva et al. [8], Braga et al. [14] and Farinha et al. [16] also evaluated this property. The authors found out that the addition of fine wastes was responsible for the decrease of water vapour permeability, similar to that observed for the addition of 20% RCA. However, Jochem et al. [19] concluded that mortars produced with recycled aggregates from CDW with a fine incorporation of 24% have higher permeability than mortars with the same additions but formulated with aggregates of crushing of natural granite aggregates.
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Fig. 13. Mortars observed at 700% (7) magnifying glass observation.
Table 8 Results of the tests of the second experimental phase and selection of the mortars with better performance.
Table 9 Air content of the mortars tested. Mortar
Air content (%)
REF RCA20 MRA15
7.13 8.88 13.88
Table 10 Water vapour permeability of the mortar tested. Mortar
Water vapour permeability (ng/(m.s.Pa))
REF RCA20 MRA15
17.52 15.67 17.21
Fig. 15. Permeability to water under pressure of the mortars tested. Fig. 14. Dimensional variation of the mortars tested.
3.2.4. Evaluation of durability by the artificial accelerated ageing test The artificial ageing process consisted of heat-freeze and humidity-freeze cycles. The heat-freeze cycle resulted from the incidence of an infrared radiation on the surface of the specimens for 8 h ± 15 min. The specimens reached a temperature of 60 ± 2 °C. After that period, the specimens were submitted to 15 ± 1 °C in a freezer for 15 h ± 15 min. Eight cycles of heat-freeze were performed. After these cycles, the specimens were submitted to another eight humidity-freeze cycles. Each cycle consisted of 8 h ± 15 min of water sprinkling, at 20 ± 2 °C. After that period,
the specimens were submitted to 15 ± 1 °C in the freezer for 15 h ± 15 min. After the eight cycles of heat-freeze and humidityfreeze, the specimens were maintained under controlled temperature and humidity of 20 ± 2 °C and 65 ± 5% for two weeks. The permeability to water under pressure and adherence strength were analysed before and after these cycles. 3.2.5. Permeability to water under pressure The water permeability under pressure test measures the amount of water under pressure absorbed by a mortar per unit area. The results are presented in Fig. 15.
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S. Jesus et al. / Construction and Building Materials 229 (2019) 116844 Table 11 Adherence to the substrate of the mortars tested. Mortar
REF RCA20 MRA15
Before ageing
After ageing
Adherence (MPa)
Predominant type of rupture
Standard deviation (MPa)
Adherence (MPa)
Predominant type of rupture
Standard deviation (MPa)
0.54 0.87 0.66
A/B A/C A
0.11 0.07 0.1
0.55 0.66 0.64
B A A/B
0.06 0.05 0.07
Before and after accelerated ageing, a decrease in permeability to water under pressure was noticed from the incorporation of fine aggregates. However, this reduction was more significant after ageing. This decrease in the permeability of mortar with MRA corresponded to 25% and the incorporation of RCA presented a reduction of 39% compared to the reference mortar. The ageing caused an increase of the permeability to water under pressure in all the studied mortars, which was more significant in the reference mortar. A decrease in the permeability value to water under pressure is considered positive, since it is an indication that water in liquid state has greater difficulty in penetrating the mortar. Thus, it is concluded that both modified mortars in this study showed an improvement. Silva et al. [8], Oliveira et al. [15] and Farinha et al. [16] concluded that the addition of red ceramics, glass and sanitary ware, respectively, allowed reducing the permeability to water under pressure of these mortars at 28 days, as well as after accelerated ageing. Additionally, Farinha et al. [16] found an increase in permeability after ageing. However, Oliveira et al. [15] reported that the climatic cycles improved the behaviour of mortars, i.e. the mortars with recycled aggregates had a lower permeability to liquid water. 3.2.6. Adherence strength of hardened mortars The adherence strength test results are presented in Table 11. It was found that the incorporation of fine recycled aggregate increased the adherence strength, before and after ageing, in comparison with the REF mortar. This was due to the higher mechanical strengths, when compared with REF’s. Other authors [8,15–17] found the same trend: the incorporation of fine aggregates increased the adherence strength of the modified mortars. This is attributed to a higher fine content that provides a stronger interface between the substrate and the coating, by the substrate’s suction of fines and water from the rendering. At 28 days, MRA15 showed an increase of 22% compared to the control mortar. RCA20 obtained a higher increase of about 61%. A factor for this different trend could be the partial filling of the substrate’s pores with MRA’s fines, in substitution of part of the cement, hence reducing the adherence strength. Although after ageing all the mortars changed the predominant type of rupture, only RCA20 showed a significant decrease in adherence strength. This could be related to micro-cracking inside the mortar. 4. Conclusions This paper investigates the performance of rendering mortars with incorporation of recycled aggregate from construction and demolition waste (CDW). Two types of recycled aggregate were used as filler: recycled concrete aggregate (RCA) and mixed recycled aggregate (MRA), in percentages of 0%, 10%, 15% and 20%. The results of all the properties tested showed that the incorporation improved the mechanical and water behaviour of the modified mortars. It was found that the incorporation of RCA and MRA influenced mortars’ performance differently, thus the type of wastes used have their own trends. Mortars with RCA exhibited
a better performance when compared to those with incorporation of MRA, especially concerning mechanical strength, water absorption by capillarity, water permeability under pressure and adherence strength. Regarding mortars with MRA, they also presented better results compared to the reference mortar. In the third experimental stage, RCA20 and MRA15 were selected for a deeper study. These modified mortars had a better performance in adherence strength and water permeability under pressure compared to the plain mortar. However, RCA20 and MRA15 showed an increase of 65% and 45%, respectively, in shrinkage. In conclusion, the incorporation of both types of fine recycled aggregates in mortars enhanced their properties, concerning mechanical and water behaviour, while providing a proper disposal to the waste generated. However, the increase of shrinkage and correspondent trend for micro-cracking is a drawback and solutions to minimize it will be studied in further studies. Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. References [1] Eurostat, ‘‘Waste statistics in Europe,” 2019. [2] R.V. Silva, J. De Brito, R.K. Dhir, Performance of cementitious renderings and masonry mortars containing recycled aggregates from construction and demolition wastes, Constr. Build. Mater. 105 (2016) 400–415. [3] L.F.R. Miranda, S.M.S. Selmo, CDW recycled aggregate renderings: Part II Analysis of the effect of materials finer than 75 lm under accelerated aging performance, Constr. Build. Mater. 20 (9) (2006) 625–633. [4] I. Martínez, M. Exteberria, E. Pavón, N. Díaz, Influence of demolition waste fine particles on the properties of recycled aggregate masonry mortar, Int. J. Civ. Eng. 16 (9) (2018) 1213–1226. [5] R.L.S. Ferreira, M.A.S. Anjos, A.K.C. Nóbrega, J.E.S. Pereira, E.F. Ledesma, The role of powder content of the recycled aggregates of CDW in the behaviour of rendering mortars, Constr. Build. Mater. 208 (2019) 601–612. [6] C.C. Fan, R. Huang, H. Hwang, S.J. Chao, The effects of different fine recycled concrete aggregates on the properties of Mortar, Materials (Basel) 8 (5) (2015) 2658–2672. [7] J.R. Jiménez, J. Ayuso, M. López, J.M. Fernández, J. De Brito, Use of fine recycled aggregates from ceramic waste in masonry mortar manufacturing, Constr. Build. Mater. 40 (2013) 679–690. [8] J. Silva, J. de Brito, R. Veiga, Incorporation of fine ceramics in mortars, Constr. Build. Mater. 23 (1) (2009) 556–564. [9] I. Martínez, M. Etxeberria, E. Pavón, N. Díaz, Influence of demolition waste fine particles on the properties of recycled aggregate masonry mortar, Int. J. Civ. Eng. 16 (9) (2018) 1213–1226. [10] E.F. Ledesma et al., Effect of powdered mixed recycled aggregates on bedding mortar properties, Eur. J. Environ. Civ. Eng. 8189 (2016) 1–17. [11] J. de Brito, F. Agrela, R.V. Silva, Construction and demolition wasteNew Trends in Eco-efficient and Recycled Concrete, Elsevier Ltd, 2019. [12] J. De Brito, R. Silva, Current status on the use of recycled aggregates in concrete: where do we go from here?, RILEM Tech Lett. 1 (March) (2016) 1. [13] F. Rodrigues, M.T. Carvalho, M.F. Pereira, J. De Brito, Physical and chemicalmineralogical characterization of fine recycled aggregates from construction and demolition waste, J. Cleaner Production 4 (November 2015) (2011). [14] M. Braga, J. De Brito, R. Veiga, Incorporation of fine concrete aggregates in mortars, Constr. Build. Mater. 36 (2012) 960–968. [15] R. Oliveira, J. De Brito, R. Veiga, Incorporation of fine glass aggregates in renderings, Constr. Build. Mater. 44 (2013) 329–341. [16] C. Farinha, J. de Brito, R. Veiga, Incorporation of fine sanitary ware aggregates in coating mortars, Constr. Build. Mater. 83 (May) (2015) 194–206.
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[17] K.I.S.A. Kabeer, A.K. Vyas, Utilization of marble powder as fine aggregate in mortar mixes, Constr. Build. Mater. 165 (2018) 321–332. [18] C.B. Farinha, J. de Brito, R. Veiga, Assessment of glass fibre reinforced polymer waste reuse as filler in mortars, J. Clean. Prod. 210 (2019) 1579–1594. [19] L.F. Jochem, J.C. Rocha, M. Cheriaf, Estudo Comparativo entre Argamassas de Revestimento com Agregado Reciclado de RCD e com Agregado de Britagem, Conference: Encontro Latinoamericano de Edificações e Comunidades Sustentáveis, 2013 (in Portuguese). [20] L.F.R. Miranda, S.M.S. Selmo, CDW recycled aggregate renderings: Part I – Analysis of the effect of materials finer than 75 lm on mortar properties, Constr. Build. Mater. 20 (9) (2006) 615–624. [21] EN 1015-1, Methods of test for mortar for masonry – Part 1: Determination of particle size distribution (by sieve analysis), 1998. [22] Cahier 2669-4, Certification CSTB des enduits monocouches d’imperme´abilisation, Modalite´s d’essais, 1993. [23] EN 1015-3, Methods of test for mortar for masonry – Part 3: Determination of consistence of fresh mortar (by flow table), 1999. [24] EN 1015-6, Methods of test for mortar for masonry – Part 6: Determination of bulk density of fresh mortar, 1998. [25] EN 1015-10, Methods of test for mortar for masonry – Part 10: Determination of dry bulk density of hardened mortar, 1999. [26] EN 14146, Natural stone test methods. Determination of the dynamic elastic modulus of elasticity (by measuring the fundamental resonance frequency), 2004.
[27] FE Pa 43, Test of evaluation of the mechanical characteristics by ultra-sounds (in Portuguese), 2010. [28] EN 1015-11, Methods of test for mortar for masonry – Part 11: Determination of flexural and compressive strength of hardened mortar, 1999. [29] EN 1015-18, Methods of test for mortar for masonry – Part 18: Determination of water absorption coefficient due to capillary action of hardened mortar, 2002. [30] EN 16322, Conservation of Cultural Heritage – Tests methods – Determination of drying properties. European Committee for Standardization (CEN), 2013. [31] EN 1936, Natural stone test methods. Determination of real density and apparent density and total and partial open porosity, 2007. [32] EN 1015-7, Methods of test for mortar for masonry – Part 7: Determination of air content of fresh mortar, 1998. [33] EN 1015-19, Methods of test for mortar for masonry – Part 19: Determination of water vapour permeability of hardened rendering and plastering mortars, 1998. [34] EN 1015-21, Methods of test for mortar for masonry – Part 21: Determination of the compatibility of one-coat rendering mortars with substrates, 2002. [35] EN 1015-12, Methods of test for mortar for masonry – Part 12: Determination of adhesive strength of hardened rendering and plastering mortars on substrates, 2000. [36] C.B. Farinha, J. de Brito, J.M. Fernández, J.R. Jiménez, A.R. Esquinas, Wastes as aggregates, binders or additions in mortars: Selecting their role based on characterization, Materials (Basel) (2018).