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Evaluation of capillary water absorption in rendering mortars made with powdered waterproofing additives
Construction and Building Materials 23 (2009) 3287–3291
Contents lists available at ScienceDirect
Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat
Evaluation of capillary water absorption in rendering mortars made with powdered waterproofing additives Marcos Lanzón a, P.A. García-Ruiz b,* a
Departamento de Arquitectura y Tecnología de la Edificación, Escuela de Arquitectura e Ingeniería de la Edificación, Universidad Politécnica de Cartagena, Alfonso XIII 52, E-30203 Cartagena, Spain b Grupo E047-01 QCBA, Departamento de Química Orgánica, Facultad de Química, Universidad de Murcia, E-30100 Espinardo, Murcia, Spain
a r t i c l e
i n f o
Article history: Received 17 January 2008 Received in revised form 5 May 2009 Accepted 8 May 2009 Available online 11 June 2009 Keywords: Waterproofing Sorptivity Water absorption Durability
a b s t r a c t Several additives, such as powdered stearates, oleates, silanes and silicone films, are used to avoid water absorption in renders. This paper looks at the effectiveness of six powdered waterproofing additives after 28 days of curing at: 0.00%, 0.25%, 0.50%, 1.00% and 2.00% w/w on the whole composition. The waterproofing efficiency is analyzed by capillary water absorption tests, while water immersion tests are also carried out after 20 and 90 min. Powdered silicone and sodium oleate showed the best resistance to water penetration, while metallic soaps in the form of calcium stearate and zinc stearate showed the lowest efficiency in this respect at low dosages. The results are useful for understanding the long-term durability of renders and the minimal waterproofing dosages according to the EN 998 requirements. Ó 2009 Published by Elsevier Ltd.
1. Introduction Rendering mortars are designed for external use and they are often applied on concrete blocks, bricks or previous cementitious materials. Most renders are used for decorative and protective purposes and they are usually coloured to avoid additional coatings, such as paint. Some renders, especially one-coat rendering mortars, are manufactured by mixing white cement, white limestone aggregates (marbles), pigments and different powdered additives including cellulose ethers and waterproofing agents. Of those waterproofing additives, some metallic soaps, such as calcium stearate, zinc stearate or sodium oleate, are normally used in renders to protect the mortar against moisture and rain. Metallic soaps, are salts from long chain fatty acids and are popular as waterproofings due to their low cost and effectiveness. The MERUC classification [1] defines six levels of capillary water absorption for one-coat rendering mortars. In addition, the CSTB methods describe the test methodology for evaluating the capillary water absorption coefficient [2]. The essential requirements concerning the tests methods and CE marking of rendering mortars are defined in the EN 998 standard [3,4]. The requirements for hardened mortars are divided into three sections; (i) compressive strength after 28 days [5], (ii) capillary water absorption [6] and (iii) thermal conductivity [7]. As regards capillary water absorption, the standard defines three waterproofing levels. At the W0 * Corresponding author. Tel.: +34 968 364814; fax: +34 968 364148. E-mail address: [email protected] (P.A. García-Ruiz). 0950-0618/$ - see front matter Ó 2009 Published by Elsevier Ltd. doi:10.1016/j.conbuildmat.2009.05.002
level, the capillary water absorption is not specified, that is the manufacturer does not declare any value. In the W1 type mortar the capillary water absorption should be lower than 0.4 kg/ m2 min0.5, while in the W2 type the capillary absorption should be lower than 0.2 kg/m2 min0.5. Therefore, the best performance in terms of water penetration and durability should be expected for the W2 type mortars. One-coat rendering mortars are typically classified as W1 or W2, whereas general purpose mortars are commonly marked as W0. Taking into account the latter requirements and the classification given by the EN 998-1:2003 standard, we thought that it might be interesting to study the relative effectiveness of common waterproofing additives and the optimal dosages for attaining the best classification (W2). Protection against water, especially in mortars made with carbonaceous aggregates, such as the one-coat renders, should be taken into consideration due to potential aggression by acidic pollutants dissolved in rain water [8–11]. As regards the waterproofing additives used in renders, metallic soaps, such as calcium stearate, zinc stearates and sodium oleate, are widely used although no reference has been found concerning their relative effectiveness. Powdered silicone additives may be used instead of metallic soaps but their high cost means that they are not currently a realistic alternative and few manufacturers use them. However, powdered silicones are very stable and show better resistance in the face of environmental aggression and so they could perhaps be used instead of metallic soaps at low dosages. In addition, the growing demand for special products within the building sector, such as repairing mortars, thin layer mortars or
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M. Lanzón, P.A. García-Ruiz / Construction and Building Materials 23 (2009) 3287–3291
Table 1 Waterproofing properties. Waterproofing
Nature
Appearance
Bulk density, g/cm3
Particle size (% passing 80 lm sieve)
Calcium stearate (CaS) Zinc stearate (ZnS) Sodium oleate (NaO) Silicone A (Sil-A) Silicone B (Sil-B) Ethylene–lauril-vinyl(HRP)
Metallic soap Metallic soap Metallic soap Redispersible silicone Redispersible silicone Hydrophobic redispersible polymer
White powder White powder Light beige powder White powder White powder White powder
0.28 0.27 0.15 0.45 0.36 0.43
100 100 78.85 90.60 89.87 75.67
joint mortars, might well increase the demand for powdered silicones. Finally, synthetic polymers, such as ethylene–laurate-vinyl powder, are used in conjunction with inorganic binders to increase water repellent properties of cementitious products. These polymers disperse readily in water during the mixing process and may be added in similar percentages to metallic soaps. Finally, silicone films based on siloxanes can be applied to the surface of mortars to preserve them externally [12]. However, the last method implies additional coatings and extra time, increasing the cost of the process. This paper focuses on the comparative effectiveness of several powdered waterproofings at different dosages, with the aim of ascertaining which waterproofings and dosages are most suited to protecting against water according to the requirements given by the EN 998-1:2003 standard.
2. Experimental procedure 2.1. Mix constituents 2.1.1. Portland cement All the samples were prepared with a Type I white cement 52.5R at 21% w/w of the whole composition.
2.3. Curves of capillary absorption Four discs per sample were introduced into a capillary chamber to follow their capillary water absorption. The samples were dried until constant mass before registering the curves and their weight variation was followed for 90 min. The lateral sides of the specimens were sealed to avoid water penetration. 2.4. Capillary water absorption The prismatic specimens were introduced into a capillary chamber to estimate the water absorption coefficient due to capillary action. The lateral sides of the specimens were sealed to restrict the water flow along the longitudinal axis. The water flux through the sample was measured by partial immersion of the specimens at a depth of 5 mm. The capillary absorption coefficient was calculated using the measurements for 10 and 90 min. 2.5. Water absorption tests The 4 4 16 cm specimens were weighed before being immersed in a water tank for 20 and 90 min, after which they were removed and partially dried to eliminate the excess of water on the surface. Water absorption was calculated as a percentage of the initial mass.
3. Experimental results and discussion 3.1. Capillary absorption curves
2.1.2. Aggregates A combination of coarse, medium and calcium carbonate filler was selected to achieve the correct size distribution. The grain size was 0.010–1.5 mm. 2.1.3. Additives The samples were prepared with a constant quantity of cellulose ether (dosage of 0.21% w/w) as is common practice in renders to achieve the right workability. Finally, six powdered waterproofing (calcium stearate, zinc stearate, sodium oleate, silicone A, silicone B and hydrophobic redispersable polymer) were used to study their influence on capillary water absorption (Table 1). The samples are termed CaS, ZnS, NaO, Sil-A, Sil-B and HRP, respectively, while the dosages investigated were 0.00%, 0.25%, 0.50%, 1.00% and 2.00% w/w of the whole composition. The samples were compared with non-waterproofed control samples (CT). 2.2. Mixing, moulding and conditioning The samples were first blended inside plastic bags to achieve better homogeneity. After this, the mortars were mechanically mixed with a constant percentage of water (21.1%) in an auto-mixer, following the EN 196-1 recommendations [13]. The recommended thickness of rendering mortars varies between 10 mm and 15 mm, and so a modified moulding method was proposed to reproduce, as closely as possible the recommended thickness. This method has been recently used for the capillary water absorption evaluation in rendering mortars [14]. After the mixing process, the samples were placed in 60 60 12 mm square plastic moulds. Three hours latter, the mortars, still in the moulds, were cut using a 50 mm diameter troncoconic ring, thus providing four specimens of 50 mm diameter and 12 ± 1 mm thickness from each formulation. These specimens (discs) were used to follow the capillary absorption curves obtained during 90 min. Additionally, a standard moulding method was followed by placing the samples into 4 4 16 cm prismatic moulds. Six specimens were made per sample, three of which were used to quantify the capillary water absorption after 28 days of curing according to the UNE-EN 1015-18 standard [6]. The remaining specimens were used to estimate their water absorption. Before the water absorption tests the specimens were dried to constant mass. After the moulding process, the specimens were enclosed in polyethylene bags (95 ± 5% RH) under laboratory conditions (23 ± 2 °C) for 48 h. The specimens were then demoulded and stored in the same conditions as above for 5 days and then at 23 ± 0.5 °C and 65 ± 1% RH for 21 days.
The capillary absorption curves for the CT, CaS, ZnS, NaO, Sil-A, Sil-B and HRP samples are shown in Figs. 1–4. At low waterproofing dosages (0.25% w/w) most of the waterproofed samples became saturated within 25–30 min (Fig. 1), while the control samples (CT) became saturated after approximately 16 min. Of particular note was the high effectiveness of sodium oleate (NaO) and the powdered silicone A (Sil-A) at low dosages. At 0.50% w/w (Fig. 2), became evident the first differences between calcium and zinc stearates (CaS and ZnS) the latter becoming saturated at the end of the experiment, while the CaS samples showed saturation at 36 min, approximately. At this dose, the powdered silicone B samples (Sil-B) showed a substantial reduction of capillary absorption, while the absorption curve of the hydrophobic redispersable polymer samples (HRP) and the ZnS samples were similar. The NaO and Sil-A samples were again the best in terms of capillary absorption. The 1.00% w/w doses did not point to major differences between ZnS and Sil-A (Fig. 3). Compared with the above dosages (0.25% and 0.50%) a significant reduction in capillary absorption was observed for the ZnS and CaS samples. The NaO samples were again slightly more effective than the Sil-A samples, while capillary absorption in the HRP samples did not decrease so much as in the ZnS samples. Finally, at very high dosages of 2.00% w/w no great differences were observed between most of the samples (Fig. 4). Silicone A seemed to be the most effective waterproofing, while calcium stearate seemed to be the worst. 3.2. Capillary water absorption The capillary water absorption coefficients for all the dosages are shown in Figs. 5 and 6. Each figure includes the reference levels
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0.35 CT CaS 0.25% ZnS 0.25% NaO 0.25% Sil-A 0.25% Sil-B 0.25% HRP 0.25%
0.25
CT CaS 2.00% ZnS 2.00% NaO 2.00% Sil-A 2.00% Sil-B 2.00% HRP 2.00%
0.30
Capillary abs., g / cm2
Capillary abs., g / cm2
0.30
0.20 0.15 0.10 0.05
0.25 0.20 0.15 0.10 0.05 0.00
0.00
0
2
4
6
8
0
10
2
time, min0.5 Fig. 1. Dosages of 0.25% w/w. Curves of capillary absorption for CT, CaS, ZnS, NaO, Sil-A, Sil-B and HRP samples.
Capillary water abs., kg / m2 min0.5
Capillary abs., g / cm2
0.20 0.15 0.10 0.05 0.00
0
2
8
10
1.2
CT CaS 0.50% ZnS 0.50% NaO 0.50% Sil-A 0.50% Sil-B 0.50% HRP 0.50%
0.25
6
Fig. 4. Dosages of 2.00% w/w. Curves of capillary absorption for CT, CaS, ZnS, NaO, Sil-A, Sil-B and HRP samples.
0.35 0.30
4
time, min0.5
4
6
8
10
time, min0.5
CaS ZnS NaO W1 upper limit W2 upper limit
1.0 0.8 0.6 0.4 0.2 0.0
0.0
0.5
1.0
1.5
2.0
2.5
Waterproofing dosage, % Fig. 2. Dosages of 0.50% w/w. Curves of capillary absorption for CT, CaS, ZnS, NaO, Sil-A, Sil-B and HRP samples.
0.35
CT CaS 1.00% ZnS 1.00% NaO 1.00% Sil-A 1.00% Sil-B 1.00% HRP 1.00%
Capillary abs., g / cm 2
0.30 0.25 0.20 0.15 0.10 0.05 0.00
0
2
4
6
8
10
time, min0.5 Fig. 3. Dosages of 1.00% w/w. Curves of capillary absorption for CT, CaS, ZnS, NaO, Sil-A, Sil-B and HRP samples.
given by the EN 998-1 standard (dotted/broken lines). Waterproofing dosages of 0.25% w/w are not recommendable when calcium or
Fig. 5. Capillary water absorption of samples made with metallic soaps (CaS, ZnS and NaO) at different dosages. The reference lines (dotted/broken lines) are taken from the EN 998-1 classification.
zinc stearates are used to waterproof mortars (Fig. 5). Zinc stearate only became effective at 0.50% w/w, whereas calcium stearate was less effective at this dose. At 1.00% and 2.00% w/w zinc stearate was again more effective than calcium stearate. Comparing the 0.50% and 1.00% w/w dosages, there was a very steep reduction in capillary water absorption in the samples made with zinc stearate. Although sodium oleate is chemically similar to zinc and calcium stearates, its efficiency as waterproofing was excellent even at very low dosage (0.25% w/w), and the mortar with this substance could be classified as W2 type from the lowest dose. In fact, the results obtained for the samples made with sodium oleate are comparable with those obtained by using powdered silicone A. However, a slight reduction in the relative effectiveness of sodium oleate was observed at the highest dosages (2.00% w/w). The powdered silicone samples showed different degree of effectiveness at the lowest dose (Fig. 6). At this dose (0.25%), the mortars made with silicone A could be classified as W2 type, whereas the silicone B mortars could not. Because of their cost, this finding should be borne in mind when using powdered silicones in rendering formulations. Both silicones provided similar results at higher dosages, although silicone A was better in all
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Sil-A Sil-B HRP W1 upper limit W2 upper limit
1.0 0.8
12
Water abs., %
Capillary water abs., kg / m 2 min0.5
1.2
0.6 0.4 0.2
CaS 90 min ZnS 90 min NaO 90 min
10 8 6 4
0.0
2
0.0
0.5
1.0
1.5
2.0
0
2.5
0.0
Waterproofing dosage, %
0.5
1.0
1.5
2.0
2.5
Waterproofing dose, % w/w
Fig. 6. Capillary water absorption of samples made with powdered silicones (Sil-A and Sil-B) and the hydrophobic polymer (HRP) at different dosages. The reference lines (dotted/broken lines) are taken from the EN 998-1 classification.
Fig. 8. Immersion tests for samples made with 0.00%, 0.25%, 0.50%, 1.00% and 2.00% w/w in calcium stearate (CaS), zinc stearate (ZnS) and sodium oleate (NaO) after 90 min of immersion.
the experiments and dosages. The hydrophobic redispersable polymer showed satisfactory water protection at low and medium dosages and slightly worse results than those obtained for ZnS and Sil-B.
16 14
The water absorption test confirmed most of the results obtained in the capillary water absorption experiments (Figs. 7–10). Sodium oleate and silicone A were once again the most effective at all the dosages. Comparing both additives, the water absorption percentage was slightly higher for the sodium oleate samples at the highest dose (2.00% w/w), which perhaps due to the air entraining effect of sodium oleate. As regards the rest samples, the lowest water absorption percentage was obtained at the highest dosages, as expected. The best results were obtained for the SilA samples after 20 and 90 min of immersion; 0.63% and 1.44%, respectively. At the same dosages, the worst results were observed for the CaS samples; 4.47% and 5.42%, respectively. The ZnS and HRP samples showed a noticeable increase in waterproofing capacity for dosages above 0.5% w/w.
8 6 4 2 0
14
Water abs., %
8 6
2
2.0
2.5
Waterproofing dose, % w/w Fig. 7. Immersion tests for samples made with 0.00%, 0.25%, 0.50%, 1.00% and 2.00% w/w in calcium stearate (CaS), zinc stearate (ZnS) and sodium oleate (NaO) after 20 min of immersion.
2.5
6
2
1.5
2.0
8
4
1.0
1.5
Sil-A 90 min Sil-B 90 min HRP 90 min
10
4
0.5
1.0
12
CaS 20 min ZnS 20 min NaO 20 min
0.0
0.5
Fig. 9. Immersion tests for samples made with 0.00%, 0.25%, 0.50%, 1.00% and 2.00% w/w in silicone A (Sil-A), silicone B (Sil-B) and hydrophobic polymer (HRP) after 20 min of immersion.
14
0
0.0
Waterproofing dose, % w/w
16
10
Sil-A 20 min Sil-B 20 min HRP 20 min
10
16
12
Water abs., %
Water abs., %
12
3.3. Water absorption tests
0
0.0
0.5
1.0
1.5
2.0
2.5
Waterproofing dose, % w/w Fig. 10. Immersion tests for samples made with 0.00%, 0.25%, 0.50%, 1.00% and 2.00% w/w in silicone A (Sil-A), silicone B (Sil-B) and hydrophobic polymer (HRP) after 90 min of immersion.
M. Lanzón, P.A. García-Ruiz / Construction and Building Materials 23 (2009) 3287–3291
4. Conclusions The effectiveness of powdered waterproofing additives typically used in renders was studied through water absorption experiments: capillary absorption curves, capillary absorption coefficient and water absorption percentage after 20 and 90 min of immersion. The reference levels (W1 and W2) and requirements given by the EN 998-1 standard and the method proposed in the EN 1015-18 standard were used to give an idea of the waterproofing effectiveness of each waterproofing at each dosage. We can conclude:
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as W2 type mortars. Rendering mortars made with zinc stearate were very effective at dosages above 1.00% w/w but only showed similar effectiveness to silicones or sodium oleate at the highest dosage. Rendering mortars made with calcium stearate, especially at dosages lower than 1.00% w/w, cannot be recommended to reach the minimal requirements (W1 or W2). Finally, mortars made with hydrophobic polymers (HRP) showed better results than when calcium stearate was used and they could be used to reach the W1 or W2 classification, depending on the waterproofing dosage used. Acknowledgments
1. Of the metallic soaps, sodium oleate can be considered the best alternative at all the dosages. The latter was confirmed by the capillary absorption curves, capillary water absorption coefficients and water immersion tests. The capillary water absorption value was extremely low even at the lowest dosages and the samples made with sodium oleate should be classified as W2 type mortars. In addition, sodium oleate gave better results than powdered silicones for intermediate dosages. 2. At low dosages (0.25% or 0.50% w/w), calcium stearate did not reach the minimal requirements demanded by the EN 998-1 standard. Therefore, calcium stearate should not be recommended at low dosages, whereas zinc stearate could be used instead of calcium stearate at intermediate dosages. 3. Powdered silicones were very effective as water repellents in the mortars investigated. However, silicone B was not as effective as silicone A. The Sil-A samples reached the W2 classification from the lowest dosages (0.25% w/w), whereas Sil-B only reach this level above 0.50% w/w. At the highest dosage (2.00% w/w) silicone A showed the lowest water absorption values of all the tests. Due to their chemical properties, silicones may be a good alternative for guaranteeing long term waterproofing in cementitious mortars as one-coat renders. 4. The samples made with hydrophobic polymer (HRP) gave similar results to the zinc stearate samples. However, at the lowest dosages (0.25% w/w) the hydrophobic polymer was more effective (W1) than zinc stearate. At dosages of 0.50% w/w, both additives showed very similar behaviour (W1) and finally, at the highest dosages the HRP samples were seen to be less effective than the ZnS samples. Comparing their capillary absorption coefficients and the EN 998-1 requirements, rendering mortars made with sodium oleate and silicones, especially silicone A, were extremely effective as water repellents. In most cases, these mortars could be classified
The authors express their thanks to the Centre for the Development of Industrial Technology (CDTI) under the Spanish Ministry of Science and Technology. The support given by Wacker-Chemie GmbH by providing some materials and technical information required for this research is greatly appreciated. References [1] CSTB Certification des enduits monocouches d’imperméabilisation, MERUC classification. Cahiers du CSTB 1778; 1982. [2] Certification CSTB des enduits monocouches d’imperméabilisation, Modalités d’essais. Cahiers du CSTB 2669-4; 1982. [3] EN 998-1:2003. Specification for mortar for masonry. - Part 1: rendering and plastering mortar. European Committee for Standardization. [4] EN 998-2:2003. Specification for mortar for masonry. - Part 2: masonry mortar. European Committee for Standardization. [5] EN 1015-11:1999. Methods of test for mortar for masonry. Part 11: determination of flexural and compressive strength of hardened mortar. European Committee for Standardization. [6] EN 1015-18:2002. Methods of tests for mortars for masonry. Part 18: determination of water absorption coefficient due to capillary action of hardened mortar. European Committee for Standardization. [7] EN 1745:2002. Masonry and masonry products. Methods for determining design thermal values. European Committee for Standardization. [8] Beddoe RE, Dorner HW. Modelling acid attack on concrete: Part I. The essential mechanisms. Cem Concr Res 2005;35:2333–9. [9] Brown PW, Clifton JR. Mechanism of deterioration in cement-based materials and in lime mortar. Durab Build Mat 1998;5:409–20. [10] Zivica V, Bajzab A. Acidic attack of cement based materials a review. Part I: principle of acidic attack. Constr Build Mater 2001;15:331–40. [11] Zivica V, Bajzab A. Acidic attack of cement based materials a review. Part II: factors of rate of acidic attack and protective measures. Constr Build Mater 2002;16:215–22. [12] Maravelaki-Kalaitzaki P. Hydraulic lime mortars with siloxane for waterproofing historic masonry. Cem Concr Res 2007;37:283–90. [13] EN 196-1:1994. Methods of testing cement. Part 1. European Committee for Standardization. [14] Lanzón M, García-Ruiz PA. Effectiveness and durability evaluation of rendering mortars made with metallic soaps and powdered silicone. Constr Build Mater 2008;22:2308–15.
Contents lists available at ScienceDirect
Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat
Evaluation of capillary water absorption in rendering mortars made with powdered waterproofing additives Marcos Lanzón a, P.A. García-Ruiz b,* a
Departamento de Arquitectura y Tecnología de la Edificación, Escuela de Arquitectura e Ingeniería de la Edificación, Universidad Politécnica de Cartagena, Alfonso XIII 52, E-30203 Cartagena, Spain b Grupo E047-01 QCBA, Departamento de Química Orgánica, Facultad de Química, Universidad de Murcia, E-30100 Espinardo, Murcia, Spain
a r t i c l e
i n f o
Article history: Received 17 January 2008 Received in revised form 5 May 2009 Accepted 8 May 2009 Available online 11 June 2009 Keywords: Waterproofing Sorptivity Water absorption Durability
a b s t r a c t Several additives, such as powdered stearates, oleates, silanes and silicone films, are used to avoid water absorption in renders. This paper looks at the effectiveness of six powdered waterproofing additives after 28 days of curing at: 0.00%, 0.25%, 0.50%, 1.00% and 2.00% w/w on the whole composition. The waterproofing efficiency is analyzed by capillary water absorption tests, while water immersion tests are also carried out after 20 and 90 min. Powdered silicone and sodium oleate showed the best resistance to water penetration, while metallic soaps in the form of calcium stearate and zinc stearate showed the lowest efficiency in this respect at low dosages. The results are useful for understanding the long-term durability of renders and the minimal waterproofing dosages according to the EN 998 requirements. Ó 2009 Published by Elsevier Ltd.
1. Introduction Rendering mortars are designed for external use and they are often applied on concrete blocks, bricks or previous cementitious materials. Most renders are used for decorative and protective purposes and they are usually coloured to avoid additional coatings, such as paint. Some renders, especially one-coat rendering mortars, are manufactured by mixing white cement, white limestone aggregates (marbles), pigments and different powdered additives including cellulose ethers and waterproofing agents. Of those waterproofing additives, some metallic soaps, such as calcium stearate, zinc stearate or sodium oleate, are normally used in renders to protect the mortar against moisture and rain. Metallic soaps, are salts from long chain fatty acids and are popular as waterproofings due to their low cost and effectiveness. The MERUC classification [1] defines six levels of capillary water absorption for one-coat rendering mortars. In addition, the CSTB methods describe the test methodology for evaluating the capillary water absorption coefficient [2]. The essential requirements concerning the tests methods and CE marking of rendering mortars are defined in the EN 998 standard [3,4]. The requirements for hardened mortars are divided into three sections; (i) compressive strength after 28 days [5], (ii) capillary water absorption [6] and (iii) thermal conductivity [7]. As regards capillary water absorption, the standard defines three waterproofing levels. At the W0 * Corresponding author. Tel.: +34 968 364814; fax: +34 968 364148. E-mail address: [email protected] (P.A. García-Ruiz). 0950-0618/$ - see front matter Ó 2009 Published by Elsevier Ltd. doi:10.1016/j.conbuildmat.2009.05.002
level, the capillary water absorption is not specified, that is the manufacturer does not declare any value. In the W1 type mortar the capillary water absorption should be lower than 0.4 kg/ m2 min0.5, while in the W2 type the capillary absorption should be lower than 0.2 kg/m2 min0.5. Therefore, the best performance in terms of water penetration and durability should be expected for the W2 type mortars. One-coat rendering mortars are typically classified as W1 or W2, whereas general purpose mortars are commonly marked as W0. Taking into account the latter requirements and the classification given by the EN 998-1:2003 standard, we thought that it might be interesting to study the relative effectiveness of common waterproofing additives and the optimal dosages for attaining the best classification (W2). Protection against water, especially in mortars made with carbonaceous aggregates, such as the one-coat renders, should be taken into consideration due to potential aggression by acidic pollutants dissolved in rain water [8–11]. As regards the waterproofing additives used in renders, metallic soaps, such as calcium stearate, zinc stearates and sodium oleate, are widely used although no reference has been found concerning their relative effectiveness. Powdered silicone additives may be used instead of metallic soaps but their high cost means that they are not currently a realistic alternative and few manufacturers use them. However, powdered silicones are very stable and show better resistance in the face of environmental aggression and so they could perhaps be used instead of metallic soaps at low dosages. In addition, the growing demand for special products within the building sector, such as repairing mortars, thin layer mortars or
3288
M. Lanzón, P.A. García-Ruiz / Construction and Building Materials 23 (2009) 3287–3291
Table 1 Waterproofing properties. Waterproofing
Nature
Appearance
Bulk density, g/cm3
Particle size (% passing 80 lm sieve)
Calcium stearate (CaS) Zinc stearate (ZnS) Sodium oleate (NaO) Silicone A (Sil-A) Silicone B (Sil-B) Ethylene–lauril-vinyl(HRP)
Metallic soap Metallic soap Metallic soap Redispersible silicone Redispersible silicone Hydrophobic redispersible polymer
White powder White powder Light beige powder White powder White powder White powder
0.28 0.27 0.15 0.45 0.36 0.43
100 100 78.85 90.60 89.87 75.67
joint mortars, might well increase the demand for powdered silicones. Finally, synthetic polymers, such as ethylene–laurate-vinyl powder, are used in conjunction with inorganic binders to increase water repellent properties of cementitious products. These polymers disperse readily in water during the mixing process and may be added in similar percentages to metallic soaps. Finally, silicone films based on siloxanes can be applied to the surface of mortars to preserve them externally [12]. However, the last method implies additional coatings and extra time, increasing the cost of the process. This paper focuses on the comparative effectiveness of several powdered waterproofings at different dosages, with the aim of ascertaining which waterproofings and dosages are most suited to protecting against water according to the requirements given by the EN 998-1:2003 standard.
2. Experimental procedure 2.1. Mix constituents 2.1.1. Portland cement All the samples were prepared with a Type I white cement 52.5R at 21% w/w of the whole composition.
2.3. Curves of capillary absorption Four discs per sample were introduced into a capillary chamber to follow their capillary water absorption. The samples were dried until constant mass before registering the curves and their weight variation was followed for 90 min. The lateral sides of the specimens were sealed to avoid water penetration. 2.4. Capillary water absorption The prismatic specimens were introduced into a capillary chamber to estimate the water absorption coefficient due to capillary action. The lateral sides of the specimens were sealed to restrict the water flow along the longitudinal axis. The water flux through the sample was measured by partial immersion of the specimens at a depth of 5 mm. The capillary absorption coefficient was calculated using the measurements for 10 and 90 min. 2.5. Water absorption tests The 4 4 16 cm specimens were weighed before being immersed in a water tank for 20 and 90 min, after which they were removed and partially dried to eliminate the excess of water on the surface. Water absorption was calculated as a percentage of the initial mass.
3. Experimental results and discussion 3.1. Capillary absorption curves
2.1.2. Aggregates A combination of coarse, medium and calcium carbonate filler was selected to achieve the correct size distribution. The grain size was 0.010–1.5 mm. 2.1.3. Additives The samples were prepared with a constant quantity of cellulose ether (dosage of 0.21% w/w) as is common practice in renders to achieve the right workability. Finally, six powdered waterproofing (calcium stearate, zinc stearate, sodium oleate, silicone A, silicone B and hydrophobic redispersable polymer) were used to study their influence on capillary water absorption (Table 1). The samples are termed CaS, ZnS, NaO, Sil-A, Sil-B and HRP, respectively, while the dosages investigated were 0.00%, 0.25%, 0.50%, 1.00% and 2.00% w/w of the whole composition. The samples were compared with non-waterproofed control samples (CT). 2.2. Mixing, moulding and conditioning The samples were first blended inside plastic bags to achieve better homogeneity. After this, the mortars were mechanically mixed with a constant percentage of water (21.1%) in an auto-mixer, following the EN 196-1 recommendations [13]. The recommended thickness of rendering mortars varies between 10 mm and 15 mm, and so a modified moulding method was proposed to reproduce, as closely as possible the recommended thickness. This method has been recently used for the capillary water absorption evaluation in rendering mortars [14]. After the mixing process, the samples were placed in 60 60 12 mm square plastic moulds. Three hours latter, the mortars, still in the moulds, were cut using a 50 mm diameter troncoconic ring, thus providing four specimens of 50 mm diameter and 12 ± 1 mm thickness from each formulation. These specimens (discs) were used to follow the capillary absorption curves obtained during 90 min. Additionally, a standard moulding method was followed by placing the samples into 4 4 16 cm prismatic moulds. Six specimens were made per sample, three of which were used to quantify the capillary water absorption after 28 days of curing according to the UNE-EN 1015-18 standard [6]. The remaining specimens were used to estimate their water absorption. Before the water absorption tests the specimens were dried to constant mass. After the moulding process, the specimens were enclosed in polyethylene bags (95 ± 5% RH) under laboratory conditions (23 ± 2 °C) for 48 h. The specimens were then demoulded and stored in the same conditions as above for 5 days and then at 23 ± 0.5 °C and 65 ± 1% RH for 21 days.
The capillary absorption curves for the CT, CaS, ZnS, NaO, Sil-A, Sil-B and HRP samples are shown in Figs. 1–4. At low waterproofing dosages (0.25% w/w) most of the waterproofed samples became saturated within 25–30 min (Fig. 1), while the control samples (CT) became saturated after approximately 16 min. Of particular note was the high effectiveness of sodium oleate (NaO) and the powdered silicone A (Sil-A) at low dosages. At 0.50% w/w (Fig. 2), became evident the first differences between calcium and zinc stearates (CaS and ZnS) the latter becoming saturated at the end of the experiment, while the CaS samples showed saturation at 36 min, approximately. At this dose, the powdered silicone B samples (Sil-B) showed a substantial reduction of capillary absorption, while the absorption curve of the hydrophobic redispersable polymer samples (HRP) and the ZnS samples were similar. The NaO and Sil-A samples were again the best in terms of capillary absorption. The 1.00% w/w doses did not point to major differences between ZnS and Sil-A (Fig. 3). Compared with the above dosages (0.25% and 0.50%) a significant reduction in capillary absorption was observed for the ZnS and CaS samples. The NaO samples were again slightly more effective than the Sil-A samples, while capillary absorption in the HRP samples did not decrease so much as in the ZnS samples. Finally, at very high dosages of 2.00% w/w no great differences were observed between most of the samples (Fig. 4). Silicone A seemed to be the most effective waterproofing, while calcium stearate seemed to be the worst. 3.2. Capillary water absorption The capillary water absorption coefficients for all the dosages are shown in Figs. 5 and 6. Each figure includes the reference levels
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0.35 CT CaS 0.25% ZnS 0.25% NaO 0.25% Sil-A 0.25% Sil-B 0.25% HRP 0.25%
0.25
CT CaS 2.00% ZnS 2.00% NaO 2.00% Sil-A 2.00% Sil-B 2.00% HRP 2.00%
0.30
Capillary abs., g / cm2
Capillary abs., g / cm2
0.30
0.20 0.15 0.10 0.05
0.25 0.20 0.15 0.10 0.05 0.00
0.00
0
2
4
6
8
0
10
2
time, min0.5 Fig. 1. Dosages of 0.25% w/w. Curves of capillary absorption for CT, CaS, ZnS, NaO, Sil-A, Sil-B and HRP samples.
Capillary water abs., kg / m2 min0.5
Capillary abs., g / cm2
0.20 0.15 0.10 0.05 0.00
0
2
8
10
1.2
CT CaS 0.50% ZnS 0.50% NaO 0.50% Sil-A 0.50% Sil-B 0.50% HRP 0.50%
0.25
6
Fig. 4. Dosages of 2.00% w/w. Curves of capillary absorption for CT, CaS, ZnS, NaO, Sil-A, Sil-B and HRP samples.
0.35 0.30
4
time, min0.5
4
6
8
10
time, min0.5
CaS ZnS NaO W1 upper limit W2 upper limit
1.0 0.8 0.6 0.4 0.2 0.0
0.0
0.5
1.0
1.5
2.0
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Waterproofing dosage, % Fig. 2. Dosages of 0.50% w/w. Curves of capillary absorption for CT, CaS, ZnS, NaO, Sil-A, Sil-B and HRP samples.
0.35
CT CaS 1.00% ZnS 1.00% NaO 1.00% Sil-A 1.00% Sil-B 1.00% HRP 1.00%
Capillary abs., g / cm 2
0.30 0.25 0.20 0.15 0.10 0.05 0.00
0
2
4
6
8
10
time, min0.5 Fig. 3. Dosages of 1.00% w/w. Curves of capillary absorption for CT, CaS, ZnS, NaO, Sil-A, Sil-B and HRP samples.
given by the EN 998-1 standard (dotted/broken lines). Waterproofing dosages of 0.25% w/w are not recommendable when calcium or
Fig. 5. Capillary water absorption of samples made with metallic soaps (CaS, ZnS and NaO) at different dosages. The reference lines (dotted/broken lines) are taken from the EN 998-1 classification.
zinc stearates are used to waterproof mortars (Fig. 5). Zinc stearate only became effective at 0.50% w/w, whereas calcium stearate was less effective at this dose. At 1.00% and 2.00% w/w zinc stearate was again more effective than calcium stearate. Comparing the 0.50% and 1.00% w/w dosages, there was a very steep reduction in capillary water absorption in the samples made with zinc stearate. Although sodium oleate is chemically similar to zinc and calcium stearates, its efficiency as waterproofing was excellent even at very low dosage (0.25% w/w), and the mortar with this substance could be classified as W2 type from the lowest dose. In fact, the results obtained for the samples made with sodium oleate are comparable with those obtained by using powdered silicone A. However, a slight reduction in the relative effectiveness of sodium oleate was observed at the highest dosages (2.00% w/w). The powdered silicone samples showed different degree of effectiveness at the lowest dose (Fig. 6). At this dose (0.25%), the mortars made with silicone A could be classified as W2 type, whereas the silicone B mortars could not. Because of their cost, this finding should be borne in mind when using powdered silicones in rendering formulations. Both silicones provided similar results at higher dosages, although silicone A was better in all
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Sil-A Sil-B HRP W1 upper limit W2 upper limit
1.0 0.8
12
Water abs., %
Capillary water abs., kg / m 2 min0.5
1.2
0.6 0.4 0.2
CaS 90 min ZnS 90 min NaO 90 min
10 8 6 4
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2
0.0
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2.0
0
2.5
0.0
Waterproofing dosage, %
0.5
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Waterproofing dose, % w/w
Fig. 6. Capillary water absorption of samples made with powdered silicones (Sil-A and Sil-B) and the hydrophobic polymer (HRP) at different dosages. The reference lines (dotted/broken lines) are taken from the EN 998-1 classification.
Fig. 8. Immersion tests for samples made with 0.00%, 0.25%, 0.50%, 1.00% and 2.00% w/w in calcium stearate (CaS), zinc stearate (ZnS) and sodium oleate (NaO) after 90 min of immersion.
the experiments and dosages. The hydrophobic redispersable polymer showed satisfactory water protection at low and medium dosages and slightly worse results than those obtained for ZnS and Sil-B.
16 14
The water absorption test confirmed most of the results obtained in the capillary water absorption experiments (Figs. 7–10). Sodium oleate and silicone A were once again the most effective at all the dosages. Comparing both additives, the water absorption percentage was slightly higher for the sodium oleate samples at the highest dose (2.00% w/w), which perhaps due to the air entraining effect of sodium oleate. As regards the rest samples, the lowest water absorption percentage was obtained at the highest dosages, as expected. The best results were obtained for the SilA samples after 20 and 90 min of immersion; 0.63% and 1.44%, respectively. At the same dosages, the worst results were observed for the CaS samples; 4.47% and 5.42%, respectively. The ZnS and HRP samples showed a noticeable increase in waterproofing capacity for dosages above 0.5% w/w.
8 6 4 2 0
14
Water abs., %
8 6
2
2.0
2.5
Waterproofing dose, % w/w Fig. 7. Immersion tests for samples made with 0.00%, 0.25%, 0.50%, 1.00% and 2.00% w/w in calcium stearate (CaS), zinc stearate (ZnS) and sodium oleate (NaO) after 20 min of immersion.
2.5
6
2
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Sil-A 90 min Sil-B 90 min HRP 90 min
10
4
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12
CaS 20 min ZnS 20 min NaO 20 min
0.0
0.5
Fig. 9. Immersion tests for samples made with 0.00%, 0.25%, 0.50%, 1.00% and 2.00% w/w in silicone A (Sil-A), silicone B (Sil-B) and hydrophobic polymer (HRP) after 20 min of immersion.
14
0
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Waterproofing dose, % w/w
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Sil-A 20 min Sil-B 20 min HRP 20 min
10
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Water abs., %
Water abs., %
12
3.3. Water absorption tests
0
0.0
0.5
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Waterproofing dose, % w/w Fig. 10. Immersion tests for samples made with 0.00%, 0.25%, 0.50%, 1.00% and 2.00% w/w in silicone A (Sil-A), silicone B (Sil-B) and hydrophobic polymer (HRP) after 90 min of immersion.
M. Lanzón, P.A. García-Ruiz / Construction and Building Materials 23 (2009) 3287–3291
4. Conclusions The effectiveness of powdered waterproofing additives typically used in renders was studied through water absorption experiments: capillary absorption curves, capillary absorption coefficient and water absorption percentage after 20 and 90 min of immersion. The reference levels (W1 and W2) and requirements given by the EN 998-1 standard and the method proposed in the EN 1015-18 standard were used to give an idea of the waterproofing effectiveness of each waterproofing at each dosage. We can conclude:
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as W2 type mortars. Rendering mortars made with zinc stearate were very effective at dosages above 1.00% w/w but only showed similar effectiveness to silicones or sodium oleate at the highest dosage. Rendering mortars made with calcium stearate, especially at dosages lower than 1.00% w/w, cannot be recommended to reach the minimal requirements (W1 or W2). Finally, mortars made with hydrophobic polymers (HRP) showed better results than when calcium stearate was used and they could be used to reach the W1 or W2 classification, depending on the waterproofing dosage used. Acknowledgments
1. Of the metallic soaps, sodium oleate can be considered the best alternative at all the dosages. The latter was confirmed by the capillary absorption curves, capillary water absorption coefficients and water immersion tests. The capillary water absorption value was extremely low even at the lowest dosages and the samples made with sodium oleate should be classified as W2 type mortars. In addition, sodium oleate gave better results than powdered silicones for intermediate dosages. 2. At low dosages (0.25% or 0.50% w/w), calcium stearate did not reach the minimal requirements demanded by the EN 998-1 standard. Therefore, calcium stearate should not be recommended at low dosages, whereas zinc stearate could be used instead of calcium stearate at intermediate dosages. 3. Powdered silicones were very effective as water repellents in the mortars investigated. However, silicone B was not as effective as silicone A. The Sil-A samples reached the W2 classification from the lowest dosages (0.25% w/w), whereas Sil-B only reach this level above 0.50% w/w. At the highest dosage (2.00% w/w) silicone A showed the lowest water absorption values of all the tests. Due to their chemical properties, silicones may be a good alternative for guaranteeing long term waterproofing in cementitious mortars as one-coat renders. 4. The samples made with hydrophobic polymer (HRP) gave similar results to the zinc stearate samples. However, at the lowest dosages (0.25% w/w) the hydrophobic polymer was more effective (W1) than zinc stearate. At dosages of 0.50% w/w, both additives showed very similar behaviour (W1) and finally, at the highest dosages the HRP samples were seen to be less effective than the ZnS samples. Comparing their capillary absorption coefficients and the EN 998-1 requirements, rendering mortars made with sodium oleate and silicones, especially silicone A, were extremely effective as water repellents. In most cases, these mortars could be classified
The authors express their thanks to the Centre for the Development of Industrial Technology (CDTI) under the Spanish Ministry of Science and Technology. The support given by Wacker-Chemie GmbH by providing some materials and technical information required for this research is greatly appreciated. References [1] CSTB Certification des enduits monocouches d’imperméabilisation, MERUC classification. Cahiers du CSTB 1778; 1982. [2] Certification CSTB des enduits monocouches d’imperméabilisation, Modalités d’essais. Cahiers du CSTB 2669-4; 1982. [3] EN 998-1:2003. Specification for mortar for masonry. - Part 1: rendering and plastering mortar. European Committee for Standardization. [4] EN 998-2:2003. Specification for mortar for masonry. - Part 2: masonry mortar. European Committee for Standardization. [5] EN 1015-11:1999. Methods of test for mortar for masonry. Part 11: determination of flexural and compressive strength of hardened mortar. European Committee for Standardization. [6] EN 1015-18:2002. Methods of tests for mortars for masonry. Part 18: determination of water absorption coefficient due to capillary action of hardened mortar. European Committee for Standardization. [7] EN 1745:2002. Masonry and masonry products. Methods for determining design thermal values. European Committee for Standardization. [8] Beddoe RE, Dorner HW. Modelling acid attack on concrete: Part I. The essential mechanisms. Cem Concr Res 2005;35:2333–9. [9] Brown PW, Clifton JR. Mechanism of deterioration in cement-based materials and in lime mortar. Durab Build Mat 1998;5:409–20. [10] Zivica V, Bajzab A. Acidic attack of cement based materials a review. Part I: principle of acidic attack. Constr Build Mater 2001;15:331–40. [11] Zivica V, Bajzab A. Acidic attack of cement based materials a review. Part II: factors of rate of acidic attack and protective measures. Constr Build Mater 2002;16:215–22. [12] Maravelaki-Kalaitzaki P. Hydraulic lime mortars with siloxane for waterproofing historic masonry. Cem Concr Res 2007;37:283–90. [13] EN 196-1:1994. Methods of testing cement. Part 1. European Committee for Standardization. [14] Lanzón M, García-Ruiz PA. Effectiveness and durability evaluation of rendering mortars made with metallic soaps and powdered silicone. Constr Build Mater 2008;22:2308–15.