Use of recycled water from mixer truck wash in concrete: Effect on the hydration, fresh and hardened properties

Construction and Building Materials 230 (2020) 116981

Contents lists available at ScienceDirect

Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat

Use of recycled water from mixer truck wash in concrete: Effect on the hydration, fresh and hardened properties Paulo Ricardo de Matos a,b,1,⇑, Luiz Roberto Prudêncio Jr. a, Ronaldo Pilar c, Philippe Jean Paul Gleize a,b, Fernando Pelisser a,b a b c

Department of Civil Engineering, Federal University of Santa Catarina (UFSC), Brazil Laboratory of Application of Nanotechnology in Civil Construction (LabNANOTEC), Federal University of Santa Catarina, Brazil Department of Civil Engineering, Federal University of Espírito Santo (UFES), Brazil

h i g h l i g h t s
Recycled water (RW) incorporation increased the viscosity and yield stress of pastes.
RW reduced both the concrete slump and slump loss after 60 min.
RW enhanced the Portland – fly ash cement hydration.
Concretes produced with RW showed higher compressive strengths up to 7 days.
Concretes with 50 and 100% RW reached 94 and 92% of the reference strength at 28 days.

a r t i c l e

i n f o

Article history: Received 19 June 2019 Received in revised form 2 September 2019 Accepted 15 September 2019

Keywords: Recycled water Wastewater Concrete Rheology Hydration Eco-efficient concrete Waste reuse

a b s t r a c t This work investigated the effect of using recycled water (RW) from mixer truck wash on the properties of pastes and concretes containing partial and total replacement of potable water. The fresh properties (rotational rheometry for pastes and slump for concretes, both at 0 and 60 min), hydration (isothermal calorimetry and TG) and compressive strength (at 3, 7 and 28 days) were evaluated. The results showed that the solid particles and high alkalinity of RW increased the viscosity of the pastes by up to 11% and the yield stress by up to 25% (both for 100% RW), also reducing the slump of the concretes. However, the flowability losses from 0 to 60 min were lower in the RW-containing mixtures. TG and calorimetry indicated that the RW enhanced the cement hydration at early ages, resulting in compressive strengths 8 and 16% higher than those of the reference (average of RW-containing concretes), respectively at 3 and 7 days. At 28 days, the reference concrete presented the greatest strength because of the lowest amount of water required to reach the desired flowability. Nevertheless, all concretes containing RW showed 28-days strength compatible with the reference, reaching 94% and 92% of it respectively for 50% and 100% RW. Finally, a brief discussion on the potential for RW reuse in concrete plants is presented. Ó 2019 Elsevier Ltd. All rights reserved.

1. Introduction The trend of urbanization and rapid population growth, together with the industrial growth, has substantially increased the potable water demand [1]. As a result, human water demand increased by six times in the past century [2]. According to Vajnhandl and Valh [3], the global water consumption by industrial activities would increase from 800 billion m3 in 2009 to 1500 bil⇑ Corresponding author at: Rua João Pio Duarte Silva, 205, Córrego Grande, Florianópolis, SC 88040-900, Brazil. E-mail address: [email protected] (P.R. de Matos). 1 Scopus ID: 56222333200. https://doi.org/10.1016/j.conbuildmat.2019.116981 0950-0618/Ó 2019 Elsevier Ltd. All rights reserved.

lion m3 by 2030. Moreover, the trend of global urbanization has resulted in a steady increase in urban populations, therefore increasing the urban demand for portable water. The percentage of the urban population in Europe, for example, is currently 73.4% and is expected to rise up to 81% by 2050 [4]. In China, cities like Beijing can only meet 70% of the water demand using local water resources, despite efforts to reduce domestic water consumption over the past years [5]. In this scenario, the use of alternative water sources, such as recycled water, is necessary to overcome the emerging water scarcity challenges [6]. Consequently, water treatment and reuse is currently subject of several researches, both in industrial [1,3,7–11], urban [4,12,13], and farming applications [14,15].

2

P.R. de Matos et al. / Construction and Building Materials 230 (2020) 116981

High water consumption and wastewater generation in the concrete industry have become very important environmental issues [16]. In Brazil, about 51 million m3 of concrete are produced annually in plant [17]. It is estimated that, at the end of the day, about 300 kg of plastic concrete is left in each mixer truck. This concrete can be either reused in the next day by the use of hydration stabilizing admixtures or washed out [18]. Brazil is the world leader in reuse of this concrete surplus: about 9.0%, compared to 6.0% for the USA, 2.5% for Europe and 1.5% for Japan and Hong Kong [19]. The water from the washing of the trucks, on the other hand, still does not have a large-scale application. According Borger et al. [20], the external and internal washing of each mixer truck demands 800– 1000 L of water, generating the grey water. It is estimated that there are about 9–12 thousand concrete mixer trucks currently operating in Brazil [21,22]. Thus, the cleaning of these trucks generates about 10 thousand m3 of wash water daily. After washing the trucks, the grey water is taken to decantation tanks (or settling box), which have the function of reducing the amount of solid material and segregating oils and other elements immiscible in water. The water resulting from this decantation process is called recycled water (RW) or reclaimed water [23]. The RW can be considered as a contaminating material, since it usually presents pH from 11 to 12 due to the high concentration of alkalis from Portland cement [24], besides other chemical components from admixtures. Thus, its final disposal must be done in a controlled manner, and is regulated in several countries, as in the USA by the Environmental Protection Agency (EPA) [19]. Therefore, in addition to the environmental impact caused by this material, it generates high costs for the concrete plants. Thus, the search for a suitable destination for the RW is justified. Sandrolini and Franzoni [18] evaluated the slump, 7- and 28days compressive and flexural strength, water absorption and porosity of concretes produced with total replacement of potable water by RW. Borger et al. [20] evaluated the expansion, setting time by Vicat method, flow spread and compressive strength at 3, 7 and 28 days of mortars containing a wash water produced in the laboratory. Asadollahfardi et al. [24] evaluated the slump, setting time by Vicat, and the flexural and compressive strengths up to 90 days of concretes containing from 0 to 100% RW. Chini et al. [25] also evaluated the slump, setting time (by Vicat), compressive and flexural strength of concretes containing RW, in addition to the resistance to chloride ion penetration and volumetric variation tests. Su et al. [26] produces mortars and concretes with total replacement of tap water by a wash waters collected from the top, middle and bottom parts of the settling box, evaluating the setting time, compressive strength and flow spread of the mortars, and the slump and compressive strength of the concreters. Finally, Chatveera et al. [27,28] evaluated the slump, temperature rise, setting time (by Vicat), unit weight, compressive strength up to 90 days and modulus of elasticity at 28 days of concretes produced with partial and total replacement of potable water by RW. In general, the RW incorporation led to slight reductions in the workability, mechanical strength and setting time of the mixtures, as further discussed in this paper. The works reported in the literature evaluated the cement hydration and fresh state properties through empirical tests, such as slump test for workability or Vicat method for setting time. According to Ferraris [29], empirical workability tests generally describe the flow behavior of the cement-based materials in a particular set of circumstances, indirectly evaluating its rheological properties. On the other hand, the use of rheometry can determine the actual rheological parameters of the material (i.e. viscosity and yield stress), thus describing the flow behavior in a more complete and accurate way. Regarding the cement hydration, the use of isothermal calorimetry together with thermogravimetric analysis allows to evaluate the hydration kinetic over time, in addition to

quantify the hydrated phases. Therefore, the use of those techniques in RW-containing mixtures, which are nonexistent to our knowledge, may provide valuable results to better understand the effect of using such waste on concrete properties. In this work, cement pastes and concretes were produced with 0–100% RW in potable water replacement. The hydration was evaluated by isothermal calorimetry and thermogravimetric analysis at different ages. The rheological properties of the pastes were evaluated by rotational rheometry, in addition to the concrete slump test. Furthermore, the compressive strength of the concretes was determined at 3, 7 and 28 days. Finally, a brief discussion on the potential for RW reuse in concrete plants was performed. 2. Materials and mixtures 2.1. Materials A Portland – fly ash cement was used in all mixtures, equivalent to CEM II/B-V of EN 197-1, commercially available in Brazil as CPIV [30]. This is the type of cement most commonly used by concrete plants in southern Brazil [31], and contains about 25% fly ash as verified in Table 1 by the insoluble residue content. Tables 1 and 2 present respectively the chemical composition and physical properties of the Portland cement used. In the pastes preparation, a quartz powder was used as an inert filler to avoid bleeding, which had density of 2.65 g/cm3, maximum size of 75 lm and median diameter (D50) of 40.2 lm. Fig. 1 shows the particle size distributions of the cement and quartz powder used, measured by a Microtrac S3500 Particle Size Analyzer (laser diffraction method with dry suspension). Fig. 2 presents the XRay diffraction (XRD) pattern of the quartz powder, recorded on a Miniflex II Desktop X-Ray Difractometer (Rigaku), operating at the following parameters: 30 kV/15 mA, Cu radiation, k = 1.5406 Å, 2h from 10 to 70°, and 0.05°/sec scanning rate. The only crystalline phase found was quartz, as already expected. The RW was collected from the settling box of a concrete plant in Florianópolis, SC, Brazil (Fig. 3). Table 3 presents the characterization of both potable and recycled water used. The pH was measured using a digital pHmeter (Digimed DM-22), at 25 °C and 99% RH. The solids content was determined according to the method prescribed by ASTM C1603 [32]. It can be noted in Table 3 that the recycled water meets the requirements of both ABNT NBR 15900 [33] and ASTM C1602 [34] for concrete mixing water. It is worth mentioning that the results found in this work are valid for the RW batch investigated. The RW properties may vary significantly depending on the composition of the concrete washed out (e.g. cement and admixtures types) and the decantation process, as reported by Vieira and Figueiredo [23]. For the concretes preparation, a combination of a quarzitic natural sand and a granitic manufactured sand was used as fine aggregate, in the respective ratios of 40 and 60%. The natural and manufactured sand had densities of 2.66 e 2.65 g/cm3, respectively. As coarse aggregate, a granite gravel with density of 2.61 g/cm3 was used, in two size fractions: 4.8–12.5 mm and 9.5–19.0 mm. The particle size distributions of the aggregates are shown in Fig. 4. 2.2. Mix proportioning For the reference concrete (100% potable water), a composition with a 28-days compressive strength of 35 MPa was used, conventionally employed by the concrete plant that provided the RW. The mixture presents water/cement (w/c) ratio of 0.53 and volumetric mortar content of 43%. Then, the potable water was replaced by RW in the contents of 25, 50, 75 and 100%. A slump range of 120 ± 20 mm was set for all mixtures in order to produce concretes

3

P.R. de Matos et al. / Construction and Building Materials 230 (2020) 116981 Table 1 Chemical composition of the Portland – fly ash cement used.

*

SiO2

Al2O3

Fe2O3

CaO

K2O

29.01

9.84

4.12

45.84

1.22*

Na2O

MgO

P2O5

TiO2

SO3

LoI

IR

Free CaO

2.57

–

–

2.17

3.28

25.50

0.54

Na2O equivalent Na2O + 0.64 K2O; LoI: loss on ignition; IR: insoluble residue

Table 2 Physical properties of the Portland cement used.

*

Property

Value

Density (g/cm3) Blaine fineness (m2/kg) Median diameter – D50 (mm) 28-Days compressive strength* (MPa)

2.88 417.0 16.8 42.8

In a mortar with cement: sand: water ratio of 1:3:0.48 in mass.

Fig. 3. Settling box for the concrete mixer trucks wash water treatment in the concrete plant.

Table 3 Characterization of potable and recycled water. Property

Water

pH Solid content (ppm) 1 2

Fig. 1. Particle size distribution of Portland cement and quartz powder used.

Normative limits

Potable

Recycled

6.30 <4.0

11.07 6240.0

51 50,0001,2

NBR 15900 [33]. ASTM C1602 [34].

Fig. 2. XRD pattern of the quartz powder.

Fig. 4. Particle size distribution of the aggregates.

with the same practical application. If the mixture did not initially achieve the target slump range, extra amounts of water were gradually added (within the potable/recycled water ratio initially defined) until reach that range of values. Table 4 presents the detailed proportions of the concretes investigated, before the slump adjustment. The additional water contents is presented in Section 4.1.2. The composition name is given by the prefix RW, followed by the percentage of recycled water used. Although it is common to use water reducer admixtures (e.g. superplasticizers) in concrete preparation, it was chosen not to use it in this work. It is known that the performance of dispersing agents is strongly influenced by the pH of the solution [35]. Thus, it would be difficult to predict the behavior of the admixture in the

different potable/recycled water ratios, with the pH ranging from 6.3 (100% potable water) to 11.1 (100% recycled water). For the rheological tests, isothermal calorimetry and thermogravimetric analysis, cement pastes with the same w/c ratio of the reference concrete (0.53) were prepared, with 0, 50 and 100% replacement of potable water by RW. Since the use of such w/c ratio resulted in the bleeding of the pastes, a quartz powder was used as an inert filler. The filler was employed in the mass ratio of 0.3:1.0 (quartz powder:cement) in all the mixtures, which was the minimum amount of filler requires to avoid bleeding. The detailed composition of the pastes is presented in Table 5. The mix name is given in the same way as in the concretes.

4

P.R. de Matos et al. / Construction and Building Materials 230 (2020) 116981

Table 4 Mix proportions of the concretes (kg/m3), before the slump adjustment. Mix

Portland cement

RW0 RW25 RW50 RW75 RW100

320

Sand

Coarse aggregate

Water

Natural

Manuf.

4.8–9.5 mm

9.5–19.0 mm

Potable

Recycled

333

522

642

429

170.0 127.5 85.0 42.5 –

– 42.5 85.0 127.5 170.0

Table 5 Mix proportions of the pastes (kg/m3). Mix

RW0 RW50 RW100

Portland cement

1010

Quartz powder

303

2.3. Sample preparation The concretes were prepared in an inclined axis mixer at 30 rpm in 20 L batches. The mixing procedure consisted of the following steps: (1) addition of the cement, gravel and 80% of the water, and mixing for 2 min; (2) addition of the sand and remaining water, and mixing for 2 min; (3) mixing up to a total of 10 min. The fresh state tests at ‘‘0 min” were performed immediately after the mixing procedure. Then, the concrete was packed in a plastic container covered with a damp cloth to prevent water loss. After 60 min, the concrete was homogenized again, and the ‘‘60 min” fresh state tests were performed. For each concrete, nine cylindrical specimens of 100 mm in diameter and 200 mm in height were cast for the compressive strength determination. After 24 h, the specimens were demolded and cured in a humid chamber (temperature of 23 °C and 95% relative humidity) until the respective test ages. The pastes were prepared in a high shear mixer with 500 ml and 10000 rpm capacity. The dry materials (cement and quartz powder) and the respective amounts of potable and recycled water to prepare 150 ml of mixture were added to the mixer container. The materials were homogenized manually for 1 min and then mixed at 2000 rpm for 2 min. For the rheological tests, a sample of paste was immediately added to the rheometer container (for the ‘‘0 min” tests) and the remainder was stored in an enclosed vessel to prevent water loss. After 60 min, the sample was homogenized manually for 1 min and the rheological measurements were performed again. The isothermal calorimetry test was started 10 min after the contact of the water with the dry materials.

Water Potable

Recycled

535.0 267.5 –

– 267.5 535.0


Pre shear at 100 s1 for 30 s;
Rest period of 10 s;
Increase of shear rate from 0.1 to 100 s1 in the steps 0.1, 0.5, 2.5, 10, 25, 40, 55, 70, 85, 100 s1. The shear rate was maintained for 20 s in each step to stabilize the shear stress;
Decrease the shear rate back to 0.1 in the same steps. The rheological parameters were obtained by fitting the decreasing part of the flow curves by the Herschel-Bulkley (H-B) model (Eq. (1)), where s is the shear stress (Pa); s0 is the yield stress (Pa); c is the shear rate (s1), and K and n are respectively the consistency index and pseudoplastic index. Since the H-B model does not directly provide the viscosity value, an apparent viscosity (m) was calculated by Eq. (2) proposed by de Larrard et al. [37], where K and n are respectively the consistency index and pseudoplastic index of the H-B model, and cmax is the maximum shear rate applied.

s ¼ s0 þ K  cn l¼

3K  ðcmax Þn1 nþ2

ð1Þ ð2Þ

3.1.2. Concrete fresh state The workability of the concretes was evaluated by the slump test, according to ASTM C143 [38]. The test was performed immediately after the preparation of the concretes (referred to as ‘‘0 min”), and after 60 min, which is an estimated average time between the concrete mixing and its application on site. In addition, the entrained air content of the mixtures was determined immediately after its preparation, according to ASTM C173 [39].

3. Test methods 3.2. Portland cement hydration 3.1. Fresh state 3.1.1. Paste rheological tests The paste rheological test were performed 0 and 60 min after the sample preparation. The tests were conducted with a HAAKE MARS III (Thermo Scientific) rheometer. A vane geometry with four blades was selected in order to avoid wall slip [36]. The impeller had 16.0 mm in height and 22.0 mm in diameter. The cup was 27.2 mm in diameter, and was filled with 25 ml of paste. The temperature was kept at 23 °C ± 0.1 °C using a Peltier system. The rheological tests were conducted using the following steps:

3.2.1. Isothermal calorimetry The effect of RW content on Portland cement hydration kinetics was evaluated using an isothermal calorimeter (TAM Air calorimeter, TA Instruments). After the sample preparation, about 10 g of paste was placed in the calorimeter container. The measurements were recorded for 72 h at 23 °C. The duration of the induction period was obtained as proposed by Betioli et al. [40], by the intersection of the horizontal baseline with the extrapolations of the regression line (pre-induction period) and the acceleration period (where hydration reactions increase dramatically).

P.R. de Matos et al. / Construction and Building Materials 230 (2020) 116981

3.2.2. Thermogravimetric analysis The formation of hydrated compounds was evaluated by thermogravimetric analysis (TG) at 3 and 28 days. At the respective testing ages, the samples were ground in a vibratory micro mill with agate bowl (Micro Pulverisette, Fritscher) for 20 min, collecting the portion <0.075 mm. The measurements were performed using a Q600 SDT (TA Instruments) analyzer, with a heating rate of 20 °C/min up to 950 °C, and flow rate of 100 ml/min of N2. 3.3. Hardened state The compressive strength of the concretes was determined at 3, 7 and 28 days, according to ASTM C39 [41]. For each composition and age, three specimens were tested, and mean values were adopted. 4. Results and discussion 4.1. Fresh state 4.1.1. Paste rheological tests Fig. 5 shows the flow curves of the pastes and Table 6 shows the rheological parameters obtained from the Herschel-Bulkley model. This model fitted the data well, since the coefficient of determination R2 was higher than 0.990 for all the mixtures. Fig. 6 shows the yield stress (s0) and viscosity (m) of the pastes as a function of RW content, at 0 and 60 min. At both times, increasing the RW content resulted in progressive increases of the yield stress and viscosity of the mixtures. These increases were up to 25% in yield stress (at 0 min) and 13% in viscosity (at 60 min) in comparison to the reference, both for RW100. The existence of an inverse correlation between the yield stress and the flowability of Portland cement mixtures (the latter being evaluated by mini slump, slump or slump flow tests) is widespread in the literature [37,42–44]. There-

Fig. 5. Flow curves of the pastes. (a) 0 min; (b) 60 min.

5

fore, the progressive increases in the yield stress of the pastes caused by RW incorporation is in agreement with the reduction of flowability reported in the literature for concretes [18,20,26,28], and with the results obtained for the concretes produced in this work (presented later in Section 4.1.2). This behavior can be justified by the sum of some factors, presented below. Firstly, RW has an appreciable amount of solid particles in suspension. The incorporation such fine particles results in the adsorption of water to them, leaving less free water to lubricate the mixture [36]. In addition, the incorporation of those fine particles may reduce the interparticular distance, leading to greater contact between the grains [45]. Both effects can result in increases of paste viscosity and yield stress. Furthermore, in the first instants of the Portland cement hydration, it occurs the formation of C-S-H (binder phase) and ettringite, the latter corresponding to needle-shaped crystals of calcium trisulfoaluminate hydrate [46]. As will be seen later by the calorimetric results, the alkaline pH of RW enhances the cement hydration, increasing the formation of such phases in the first minutes (cumulative heat up to 10 min: 3.25, 3.49 and 3.53 J/g of cement, respectively for RW0, RW50 and RW100). Based on this, the following factors may have influenced the rheological properties of the pastes: (i) Ettringite is positively surface charged while C-S-H is negatively charged, as found by Zingg et al. [47]. The coexistence of these phases results in the trend of attraction and coagulation, which would lead to reductions in paste flowability; (ii) According to Roussel et al. [48], formation of C-S-H bridges in the contacts between the cement grains occurs already in the first instants of hydration, resulting in a network of particles with a certain rigidity. The enhancement of cement hydration would lead to further formation of C-S-H bridges, increasing the stiffness of such network. This was confirmed by Mostafa and Yahia [49], who assessed the build-up dynamic of inert and cement-based suspensions by oscillatory rheometry. The authors observed that the pastes migrated from a viscous regime to an elastic one in a few minutes (down to 5 min), and a higher cement reaction degree resulted in a higher rigidification rates mainly due to the formation of C-S-H; (iii) The needle shape of the ettringite crystals may promote interlocking between the particles, hindering the paste flow; (iv) The ettringite formation requires 32 molecules of water (since its formula is C6AS3H32). Therefore, further formation of this phase in fresh state may cause flowability losses because of the reduction in available water. In agreement with the facts (iii) and (iv), Talero et al. [50] observed that the incorporation of inert filers led to increases in the viscosity of cement pastes due to the anticipation of hydrated products formation. It is worth noting that, although the rheological tests started immediately after the paste preparation, the mixing and test preparation procedures took about 8 min, during which the formation of the first hydrated compounds already takes place. Finally, the alkalinity of RW can affect the electrokinetic potential (or zeta potential) of the particles. In an aqueous medium, the particles in suspension may acquire surface charges due to dissociation or solubilization of groups, and/or adsorption of charged compounds present in the solution. Consequently, particles with opposite charges are attracted, while particles with equal charges repel each other. In this context, the zeta potential can be understood as the difference in electrical potential between a particle and its liquid suspension, i.e., a measure of the particle’s surface electrical charge [51]. This measure is widely used to evaluate

6

P.R. de Matos et al. / Construction and Building Materials 230 (2020) 116981

Table 6 Rheological parameters, obtained by the Herschel-Bulkley model. Mix

s0

K

n

m

R2

RW0  0 min RW50  0 min RW100  0 min RW0  60 min RW50  60 min RW100  60 min

20.00 24.75 24.92 23.57 26.88 28.38

0.034 0.097 0.123 0.090 0.277 0.427

1.687 1.460 1.411 1.478 1.235 1.146

0.65 0.70 0.72 0.70 0.76 0.80

0.994 0.991 0.992 0.992 0.991 0.993

rheological measurements in RW0, thus leading to a higher flowability in 0 min but greater flowability loss from 0 to 60 min. This trend is in line with that reported by Petit et al. [57], which evaluated the rheological properties of cement mortars in different temperatures over time. The increase in temperature (which leads to higher cement reaction rates) generally led to lower increases in plastic viscosity and yield stress over time.

Fig. 6. Yield stress (s0) and viscosity (m) of the pastes at 0 and 60 min.

the stability of suspensions and the interaction between their particles, including suspensions containing Portland cement, mineral and chemical admixtures [47,52–54]. Franks [55] evaluated the effect of pH on zeta potential and rheological properties of a silica suspension containing monovalent electrolytes. The author observed that increasing the pH resulted simultaneously in increasing the zeta potential of the particles (in absolute value) and the yield stress of the mixtures. This was justified by the higher amount of poorly-hydrated ions adsorbed on the particle surface with increasing pH. Such ions would occupy spaces between the surfaces of neighboring particles in order to minimize their free energy, resulting in a kind of attraction force. This bond results in the flocculation of the particles, and consequently in the increase of the yield stress of the mixture. Similarly, Kashani et al. [56] also observed increases in the yield stress of alkali-activated cement pastes with increasing pH. Such influence of pH is even greater in Portland cement pastes, since they present constituents that rapidly ionize after the contact with water, and have their solubilization altered by pH. Indeed, Lowke and Gehlen [52] observed that the zeta potential of Portland cement and mineral additions may vary in signal and magnitude with pH variation, which may lead to the transition from a stable to an unstable (i.e., flocculated) system. Thus, it reasonable to assume that the high pH of the RW may have influenced the surface electrical properties of the cement particles, which can lead to greater flocculation of the system. Still in Fig. 6, it can be seen that all mixtures had increases in yield stress and viscosity from 0 to 60 min, as expected. However, one can note that the reference mixture had the greatest increase in yield stress from 0 to 60 min: 18% for 0% RW vs. 9–14% for the RW-containing mixtures. This behavior is also observed in the concrete tests (see Section 4.1.2), where the increase in RW content led to lower slump losses from 0 to 60 min. Considering that RW can enhance the cement hydration, the first ettringite and C-S-H formation (mainly from C3S hydration) may have occurred in the first minutes in the RW-containing mixtures, i.e. before the first rheological test. It worth remembering that the ‘‘0 min” tests started about 8 min after the first contact of the cement with water. On the other hand, such hydrates may have been formed after the first

4.1.2. Concrete fresh properties Fig. 7 presents the slump of concretes after 0 and 60 min, before and after the water adjustment. The reference concrete (RW0) showed slump outside the target range at 0 min because this mixture was reproduced just as provided by the concrete plant. Table 7 presents the amount of water added to reach the slump of 120 ± 20 mm after 0 and 60 min. For the same testing times, all concrete containing RW presented slump lower than the reference, in agreement with the results reported in the literature [18,26–28]. Consequently, such mixtures required additional amounts of water from 6 to 16 L/m3 of concrete to achieve the target slump range. Similarly, Chatveera and Lertwattanaruk [28] reported that, in order to produce concrete with slump of 100 ± 25 mm, the total replacement of potable water by RW required approximately 6% more water, compatible with the average of 6.7% for the RWcontaining concretes produced in this work. The decrease in flowability of the concretes due to the RW incorporation is in line with the results obtained in the paste rheological tests, and the causes of this phenomenon were previously discussed in Section 4.1.1. It was also observed that, in general, there was a progressive increase in water demand with increasing RW content, from 170 L to RW0 up to 186 L to RW100. This led to the increase in the effective w/c ratio from 0.53 in the reference to 0.55–0.57 in the RW-containing mixtures. The exception to this trend was the RW75 concrete, which demanded the lowest amount of extra water among the RW-containing concrete. This can be justified by the fact that this concrete had an entrained air content significantly higher than the others: 3.6% for RW75 vs. 0.4–1.6% for the others (Table 7). The increase in the entrained air content can help

Fig. 7. Slump values of concretes with 0 and 60 min, before and after water adjustment.

7

P.R. de Matos et al. / Construction and Building Materials 230 (2020) 116981 Table 7 Initial and additional water at 0 and 60 min, effective w/c ratio and air content of the concretes. Mix

Initial water (L)

Extra water at 0 min (L)

Final water at 0 min (L)

Extra water at 60 min (L)

Final water at 60 min (L)

Effective w/c

Air (%)

RW0 RW25 RW50 RW75 RW100

170 170 170 170 170

0 0 12 0 9

170 170 182 170 179

0 9 0 6 7

170 179 182 176 186

0.53 0.56 0.57 0.55 0.58

0.4 0.4 1.6 3.6 1.6

the internal lubrication of the mixture and result in the increase of the flowability of the concrete [58,59], leading to the decrease in the amount of water required to achieve a certain slump. Fig. 8 shows the slump loss of concrete from 0 to 60 min. With the exception of RW100, the RW-containing mixtures presented lower relative losses from 0 to 60 min: 32% on average, compared to 37% of the reference. This behavior was also observed in paste rheological tests, and the causes of this phenomenon were presented in Section 4.1.1. This trend results in an interesting practical implication, since the reduction of the slump loss over time decreases the need for concrete re-dosing. 4.2. Portland cement hydration 4.2.1. Isothermal calorimetry Fig. 9 shows the heat evolution curves and Fig. 10 shows the cumulative heat of the pastes up to 72 h. The values were normalized for the cement mass of the samples. Table 8 summarizes the results obtained in the calorimetry test. The incorporation of 50% RW resulted in a slight increase in the heat flow peak by 1.9% and in the cumulative heat by 1.1% in comparison to the reference. This RW content did not significantly affected the induction period. The incorporation of 100% RW, in turn, resulted in increases in heat flow peak by 9.0% and in cumulative heat by 7.1%, as well as in the reduction of the induction period by 4.0% in comparison to the reference. This indicates both a higher reaction rate and higher hydration degree at this age for the RW100 mixture. In addition, the increase in RW content progressively anticipated the occurrence of the main peak of heat release from 11:09 (RW0) to 10:49 (RW100). Overall, these results indicate that the total replacement of potable water by RW significantly enhanced the hydration of the Portland - fly ash cement used, while such enhancement was slighter for the partial replacement of water. This behavior can be explained by the sum of a few facts presented below, related to the high pH of the RW and its solid particles content. It is worth remembering that pH measures the concentration of H+ ions on a logarithmic scale, and the composition of 50% potable water (pH = 6.30) + 50% recycled water (pH = 11.07) results in a pH of 6.60. Firstly, the alkaline pH of RW can influence the reactivity of Portland cement compounds. According to Schöler et al. [60], as

Fig. 9. Heat flow curves. (a) During 72 h; (b) During the induction period. The derivative of the heat flow curve highlights the portlandite precipitation peak.

Fig. 10. Cumulative heat curves.

Fig. 8. Relative slump loss from 0 to 60 min.

Portland cement pastes contain portlandite (Ca(OH)2 crystals), the alkalinity affects the concentration of Ca2+ ions in the pore solution: higher pH values (i.e. with more OH ions available) favor the formation and precipitation of the portlandite, reducing the concentration of free Ca2+ ions in the solution. The reduction of

8

P.R. de Matos et al. / Construction and Building Materials 230 (2020) 116981

Table 8 Summary of the isothermal calorimetry test results. Mix

Duration of the induction period (h)

RW0 RW50 RW100

01:32 01:32 01:28

Heat flow peak Time (hh:mm)

Value (mW/g of cement)

11:09 10:59 10:49

3.77 3.84 4.11

the Ca2+ saturation degree eases the dissolution of the anhydrous cement phases (which are basically calcium silicates and aluminates). In fact, Kumar et al. [61] observed that the sharp increase in the Portland cement reaction rate, which characterizes the end of the induction period, occurs just after the portlandite precipitation and consequent reduction in the degree of saturation of Ca2+ ions. Such precipitation is indicated in Fig. 9b, identified by the gentle peak of heat release during the induction period. It can be noted that the increase in RW content progressively anticipated the peak related to the portlandite precipitation. Furthermore, Xu and Stark [62] also found that the reactivity of C3A increases significantly with increasing pH of the pore solution. Finally, the fact that most of the setting accelerator admixtures commercially available are alkali-based admixtures [63] proves that increasing the pH of the solution results in the acceleration of the hydration reactions. Another possible fact is that materials containing reactive aluminates (such as fly ash, present in the Portland cement used) can undergo alkaline activation in basic media, forming inorganic polymers with good mechanical strength. This activation is the basis of alkali-activated (or geopolymer) cements [64]. Alonso and Palomo [65] verified that this process is exothermic and generally occurs in the first hours (from 1 to 10 h), thus contributing to increase the heat release during the calorimetry period. It may have occurred mainly for the RW100 paste, which was produced with a very alkaline water (pH = 11.07). Finally, the fine solid particles of RW may act as nucleation points for the precipitation and growth of hydrates from the cement reactions. This leads to increases in hydration reaction rate, and consequently in the heat release [66], as verified by the isothermal calorimetry results. Overall, the results indicated that the incorporation of RW enhanced the hydration of the Portland - fly ash cement up to 72 h, which may result in greater mechanical strength of the material, as further discussed. 4.2.2. Thermogravimetric analysis Fig. 11 presents the mass loss curves (TG) and the derivative of mass loss (DTG) of the samples containing 0, 50 and 100% RW at 3 and 28 days. The mass loss in the range of 105–410 °C was accounted as the chemically bound water (CBW), and is attributed to the hydrated products (mainly C-S-H and ettringite). This is a good indicator to evaluate the degree of reaction of the cement [67]. The mass loss in the range of 410–510 °C corresponds to the decomposition of calcium hydroxide (CH). To facilitate the quantitative analysis, Fig. 12 shows the TG mass losses for CBW and CH normalized to the residual mass of the sample, respectively determined by Eqs. (3) and (4), where M105, M410, M510 and M980 are the respective sample masses at 105, 410, 510 and 980 °C [68]. Since the decomposition range of C-S-H and ettringite overlap [67,69], it was chosen to present the total mass loss of the hydrates in Fig. 12, while each phase was just qualitatively assessed in Fig. 11.

CBW ¼ CH ¼

M410  M 105 M980

M 510  M 410 M 980

Cumulative heat after 72 h (J/g of cement)

ð3Þ ð4Þ

269.6 272.6 288.8

Fig. 11. Mass loss curves (TG) in dashed lines, and derivative of mass loss (DTG) in full lines. (a) 3 days; (b) 28 days.

At 3 days, RW50 and RW100 showed greater CWB and CH mass losses than the reference. Those values were up to 3% and 15% higher, respectively for CBW and CH (Fig. 12). This again indicates that the replacement of portable water by RW enhanced the hydration of the cement up to this age, in agreement with the higher degree of reaction of the RW-containing pastes at 3 days observed in the isothermal calorimetry. This behavior reflected on the compressive strength of the concretes at early ages, as seen in Section 4.3. At 28 days, the CBW and CH contents of RW0 narrowed the gap with the RW-containing samples. At this age, the RW50 showed the highest CBW and CH levels, indicating a higher reaction degree of this paste, which is also observed in the compressive strength of the concretes (Section 4.3). In it turns, the RW100 showed CH content similar to the RW0, but higher CWB content. It may indicate the occurrence of pozzolanic activity by the fly ash present in the cement, as observed by Matos et al. [70]. The authors found that both limestone inert filler and a pozzolanic material enhanced the Portland cement hydration (in this work, caused by the RW incorporation), and therefore increased the hydrates and CH formation. However, the pozzolan partially consumed the additional

P.R. de Matos et al. / Construction and Building Materials 230 (2020) 116981

Fig. 12. TG mass loss at 3 and 28 days. CBW: chemically bound water; CH: calcium hydroxide.

CH produced, thus resulting in similar CH and higher CBW contents in comparison to the reference (only Portland cement), as observed in RW100. Such pozzolanic reactions may bring benefits to the microstructure and durability of the concretes, both for low [59,71] and high [72] levels of incorporation.

4.3. Hardened state Fig. 13 presents the compressive strength of the concretes at 3, 7 and 28 days. The error bars correspond to ±1 standard deviation. In general, the RW-containing concretes showed higher strengths than the reference at early ages, reaching values up to 18% higher at 3 days (RW100) and 23% higher at 7 days (RW50). This behavior is justified by the results obtained in isothermal calorimetry and TG, which indicated higher reaction degrees in the RW-containing samples at 3 days. The further formation of hydrated products at early ages leads to the sooner development of the microstructure, and consequently in early mechanical strength gains [73]. Additionally, according to Haufe and Vollpracht [74], higher ettringite formation in early ages can lead to the densification of the cementitious matrix, also increasing the material strength. The results obtained are in line with those reported by Su et al. [26], which also observed increases in compressive strength of concretes produced with RW in early ages. This gain can be interesting in several applications, such as the production of precast concrete elements, which require high strengths in few hours.

9

At 28 days, the reference mixture showed the greatest compressive strength among the concretes. This occurred because the RWcontaining concretes required higher amounts of water to reach the target slump range (from 6 to 16 L/m3 in comparison to the reference), resulting in w/c ratios of 0.55 to 0.58, compared to 0.53 of the reference. It is known that the compressive strength of a concrete is inversely proportional to its w/c ratio. The mixing water that is not consumed by the hydration reactions results in the formation of voids in the concrete microstructure, therefore reducing its mechanical strength [46]. Similar results were reported by Chatveera and Lertwattanaruk [28], which produced concretes with slump 100 ± 25 mm and different potable/recycled water ratios. The authors found that increasing the RW content (and thus the solid content of the water) progressively reduced the compressive strength of the concretes due to the increasing water demand to achieve the target slump range. It worth noting that, at 3 days, the RW100 had the highest compressive strength among the RW-containing concretes, while the RW50 had the highest one at 28 days. Considering that both concretes had similar w/c ratios and air content (Table 7), the difference in their compressive strength can be attributed mainly to the reaction degree. In agreement with that, the TG showed that the RW100 had the highest hydrates content at 3 days, while RW50 showed the highest one at 28 days. Despite the reductions in compressive strength resulting from the RW use, all the concretes had strengths compatible with the reference. The concrete produced with 100% RW, for example, showed compressive strength of 33.6 MPa at 28 days, i.e. 8% lower than the reference, even with a significantly higher w/c ratio (0.58 for RW100 vs. 0.53 for RW0). One way to compensate the flowability loss caused by the use of RW without adding extra amounts of water (therefore not negatively affecting the compressive strength) is by the use of plasticizer/superplasticizers admixtures. These can increase the flowability of the concrete without the need to increase the amount of water in the mixture [51]. In this work, we chose not to use these admixtures because its performances in solutions with such wide range of pH (from 6.3 to 11.1) is hard to predict. Anyhow, the use of such admixtures may be considered, as investigated by Chatveera and Lertwattanaruk [28]. 4.4. Potential for RW reuse in concrete plants Owing to the feasibility of using the RW in concrete, we present a brief discussion on the potential for its reuse in concrete plants. For this, the following data were considered:
The RW generation in Brazil is approximately 10 thousand m3/day, obtained by multiplying the volume of water used daily to wash a concrete mixer truck (800–1000 L/truck) by the number of trucks currently in operation in the country (9000–12,000 trucks) [20–22]. It corresponds to 3.1 million m3/year, considering the plants operate 6 days a week;
The volume of concrete produced in Brazilian plants is about 51 million m3/year [17];
The water demand for concrete production and concrete plant operation are based on Mack-Vergara and John [16], who carried out an extensive study on the use of water in concrete. Fig. 14 shows the average consumption of water per activity to produce 1 m3 of concrete, according to these authors. Considering that, the reuse of RW in concrete would enable to:

Fig. 13. Compressive strength of the concretes at 3, 7 and 28 days.


Meet the total water demand (including all the activities of the Fig. 14) for the production of 10 million m3 of concrete annually, corresponding to about 20% of the Brazilian production of ready-mix concrete;

10

P.R. de Matos et al. / Construction and Building Materials 230 (2020) 116981

Declaration of Competing Interest The authors declared that there is no conflict of interest.

Acknowledgements

Fig. 14. Average water requirement per activity for the production of 1 m3 of concrete, in liters/m3 of concrete (adapted from [16]). Note: the water for hydropower generation originally presented was excluded of the analysis.

The authors gratefully acknowledge the Brazilian governmental research agencies National Council for Scientific and Technological Development (CNPq), Santa Catarina Research Foundation (FAPESC) and Coordination for the Improvement of Higher Education Personnel (CAPES) for providing the financial support for this research. We also would like to acknowledge the Engemix/ Votorantim Cimentos for providing the mix proportions and materials used in this research, and Mr. André Pinheiro Machado Roos (LabNANOTEC–UFSC) for his assistance in the XRD and TG tests.

References
Produce 15.6 million m3 of concrete annually (if used only as mixing water replacement), corresponding to about 30% of the Brazilian production of ready-mix concrete;
Provide 180% of the water demand for facilities, laboratory, truck washing, dust suppression and yard washing in concrete plants.

5. Conclusions This work evaluated the effect of using recycled water (RW) from mixer truck wash on the hydration, fresh and hardened properties of cement pastes and concretes. Based on the results obtained, the following conclusions were established:
Increasing the RW content progressively increased the viscosity and yield stress of the pastes (i.e. decreased its flowability) due to its solid particles and high alkalinity. Nonetheless, RWcontaining pastes presented lower flowability losses from 0 to 60 min. In line with that, the increase in RW level progressively increased the water demand to reach the target slump range but reduced the slump losses over time.
The isothermal calorimetry showed that the incorporation of RW reduced the induction period and increased both the rate of heat release and the cumulative heat after 72 h. In addition, the thermogravimetric analysis (TG) indicated further formation of hydrated products and calcium hydroxide in RWcontaining pastes at 3 days. In turn, all the pastes showed similar compositions at 28 days.
In general, concretes containing RW showed compressive strengths higher than the reference at 3 and 7 days, in line with the results obtained in isothermal calorimetry and TG. In contrast, at 28 days, the significantly higher w/c ratios used in the RW-containing concrete (resultant from its higher water demands to achieve the target slump range), led to strengths lower than the reference. Nonetheless, the RW-containing concretes presented compressive strengths compatible with the reference, reaching 92% of it for 100% RW. Taken as a whole, it was possible to produce concretes with partial and total replacement of potable by recycled water, with no significant impairments in fresh and hardened properties. However, for its application on a large scale, it is recommended to investigate its use together with chemical admixtures and different types of cement, as well as evaluate the durability parameters of the concretes.

[1] T. Ahmad, K. Ahmad, M. Alam, Sustainable management of water treatment sludge through 3’R’ concept, J. Clean. Prod. 124 (2016) 1–13, https://doi.org/ 10.1016/j.jclepro.2016.02.073. [2] F. Wang, S. Wang, Z. Li, H. You, K.B. Aviso, R.R. Tan, X. Jia, Water footprint sustainability assessment for the chemical sector at the regional level, Resour. Conserv. Recycl. 142 (2019) 69–77, https://doi.org/10.1016/j. resconrec.2018.11.009. [3] S. Vajnhandl, J.V. Valh, The status of water reuse in European textile sector, J. Environ. Manage. 141 (2014) 29–35, https://doi.org/10.1016/ j.jenvman.2014.03.014. [4] C. Makropoulos, E. Rozos, I. Tsoukalas, A. Plevri, G. Karakatsanis, L. Karagiannidis, E. Makri, C. Lioumis, C. Noutsopoulos, D. Mamais, C. Rippis, E. Lytras, Sewer-mining: a water reuse option supporting circular economy, public service provision and entrepreneurship, J. Environ. Manage. 216 (2018) 285–298, https://doi.org/10.1016/j.jenvman.2017.07.026. [5] K. Smith, S. Liu, H.Y. Hu, X. Dong, X. Wen, Water and energy recovery: the future of wastewater in China, Sci. Total Environ. 637–638 (2018) 1466–1470, https://doi.org/10.1016/j.scitotenv.2018.05.124. [6] R. Paul, S. Kenway, P. Mukheibir, How scale and technology influence the energy intensity of water recycling systems-An analytical review, J. Clean. Prod. 215 (2019) 1457–1480, https://doi.org/10.1016/j.jclepro.2018.12.148. [7] L. Tong, X. Liu, X. Liu, Z. Yuan, Q. Zhang, Life cycle assessment of water reuse systems in an industrial park, J. Environ. Manage. 129 (2013) 471–478, https:// doi.org/10.1016/j.jenvman.2013.08.018. [8] C. Huang, F. Peng, L. Xiong, H.L. Li, X.F. Chen, C. Zhao, X. De Chen, Introduction of one efficient industrial system for turpentine processing wastewater reuse and treatment, Sci. Total Environ. 663 (2019) 447–452, https://doi.org/ 10.1016/j.scitotenv.2019.01.213. [9] R. Wang, Q. Ma, X. Ye, C. Li, Z. Zhao, Preparing coal slurry from coking wastewater to achieve resource utilization: slurrying mechanism of coking wastewater–coal slurry, Sci. Total Environ. 650 (2019) 1678–1687, https://doi. org/10.1016/j.scitotenv.2018.09.329. [10] V.B. Brião, A.C.V. Salla, T. Miorando, M. Hemkemeier, D.P.C. Favaretto, Water recovery from dairy rinse water by reverse osmosis: giving value to water and milk solids, Resour. Conserv. Recycl. 140 (2019) 313–323, https://doi.org/ 10.1016/j.resconrec.2018.10.007. [11] S. Yerri, K.R. Piratla, Decentralized water reuse planning: Evaluation of life cycle costs and benefits, Resour. Conserv. Recycl. 141 (2019) 339–346, https:// doi.org/10.1016/j.resconrec.2018.05.016. [12] H.M. Smith, S. Brouwer, P. Jeffrey, J. Frijns, Public responses to water reuse – understanding the evidence, J. Environ. Manage. 207 (2018) 43–50, https://doi. org/10.1016/j.jenvman.2017.11.021. [13] N. Russo, A. Marzo, C. Randazzo, C. Caggia, A. Toscano, G.L. Cirelli, Constructed wetlands combined with disinfection systems for removal of urban wastewater contaminants, Sci. Total Environ. 656 (2019) 558–566, https:// doi.org/10.1016/j.scitotenv.2018.11.417. [14] M.B. Johnson, M. Mehrvar, An assessment of the grey water footprint of winery wastewater in the Niagara Region of Ontario, Canada, J. Clean. Prod. 214 (2019) 623–632, https://doi.org/10.1016/j.jclepro.2018.12.311. [15] M. Terré, C. Bosch, A. Bach, F. Fàbregas, C. Biel, M. Rusiñol, S. Bofill, M. Calderer, I. Jubany, X. Martínez-Lladó, Exploring the use of tertiary reclaimed water in dairy cattle production, J. Clean. Prod. (2019), https://doi.org/10.1016/j. jclepro.2019.04.391. [16] Y.L. Mack-vergara, V.M. John, Life cycle water inventory in concrete production—a review, Resour. Conserv. Recycl. 122 (2017) 227–250, https:// doi.org/10.1016/j.resconrec.2017.01.004. [17] ABCP, Survey of the Brazilian Concrete Market Scenario, Brazilian Portland Cement Association, 2013. http://www.abcp.org.br/conteudo/imprensa/ pesquisa-inedita-e-exclusiva-revela-cenario-do-mercado-brasileiro-deconcreto.

P.R. de Matos et al. / Construction and Building Materials 230 (2020) 116981 [18] F. Sandrolini, E. Franzoni, Waste wash water recycling in ready-mixed concrete plants, Cem. Concr. Res. 31 (2001) 485–489, https://doi.org/10.1016/S00088846(00)00468-3. [19] D. Xuan, C.S. Poon, W. Zheng, Management and sustainable utilization of processing wastes from ready-mixed concrete plants in construction: a review, Resour. Conserv. Recycl. 136 (2018) 238–247, https://doi.org/ 10.1016/j.resconrec.2018.04.007. [20] J. Borger, R.L. Carrasquillo, D.W. Fowler, Use of recycled wash water and returned plastic concrete in the production of fresh concrete, Adv. Cem. Based Mater. 1 (1994) 267–274, https://doi.org/10.1016/1065-7355(94)90035-3. [21] Itambé, Concrete mixer management reduces material loss, 2014 (in portuguese). http://www.cimentoitambe.com.br/gerenciamento-decaminhao-betoneira-reduz-perda-de-materiais/ (accessed January 31, 2019). [22] AEC, Technical tips and numbers of the truck market, 2016 (in Portuguese). https://www.aecweb.com.br/cont/m/rev/dicas-tecnicas-e-numeros-domercado-de-caminhoesbetoneira_9168_42_0. [23] L. de B.P. Vieira, A.D. de Figueiredo, Evaluation of concrete recycling system efficiency for ready-mix concrete plants, Waste Manag. 56 (2016) 337–351, https://doi.org/10.1016/j.wasman.2016.07.015. [24] G. Asadollahfardi, M. Asadi, H. Jafari, A. Moradi, R. Asadollahfardi, Experimental and statistical studies of using wash water from ready-mix concrete trucks and a batching plant in the production of fresh concrete, Constr. Build. Mater. 98 (2015) 305–314, https://doi.org/10.1016/ j.conbuildmat.2015.08.053. [25] A.R. Chini, B.S. Ellis, L.C. Muszynski, M. Bergin, Reuse of wastewater generated at concrete plants in Florida in the production of fresh concrete, Mag. Concr. Res. 53 (2001) 311–319, https://doi.org/10.1680/macr.2001.53.5.311. [26] N. Su, B. Miao, F.S. Liu, Effect of wash water and underground water on properties of concrete, Cem. Concr. Res. 32 (2002) 777–782, https://doi.org/ 10.1016/S0008-8846(01)00762-1. [27] B. Chatveera, P. Lertwattanaruk, N. Makul, Effect of sludge water from readymixed concrete plant on properties and durability of concrete, Cem. Concr. Compos. 28 (2006) 441–450, https://doi.org/10.1016/j. cemconcomp.2006.01.001. [28] B. Chatveera, P. Lertwattanaruk, Use of ready-mixed concrete plant sludge water in concrete containing an additive or admixture, J. Environ. Manage. 90 (2009) 1901–1908, https://doi.org/10.1016/j.jenvman.2009.01.008. [29] C.F. Ferraris, Measurement of the rheological properties of high performance concrete: State of the art report, J. Res. Natl. Inst. Stand. Technol. 104 (1999) 461, https://doi.org/10.6028/jres.104.028. [30] ABNT, NBR 16697: Cimento Portland — Requisitos, 2018, p. 12. [31] P.R. de Matos, M.F. Marcon, R.A. Schankoski, L.R. Prudêncio Jr., Novel applications of waste foundry sand in conventional and dry-mix concretes, J. Environ. Manage. 244 (2019) 294–303, https://doi.org/10.1016/ j.jenvman.2019.04.048. [32] ASTM, ASTM C1603: Standard Test Method for Measurement of Solids in Water, 2016, pp. 1–4. https://doi.org/10.1520/C1603-05A.2. [33] ABNT, NBR 15900-3: Água para amassamento do concreto Parte 3 – Avaliação preliminar, 2009, p. 3. [34] ASTM, ASTM C1602: Standard Specification for Mixing Water Used in the Production of Hydraulic Cement Concrete, ASTM International, 2012, pp. 1–5. doi: 10.1520/C1602. [35] C.H. Chin, A. Muchtar, C.H. Azhari, M. Razali, M. Aboras, Optimization of pH and dispersant amount of Y-TZP suspension for colloidal stability, Ceram. Int. 41 (2015) 9939–9946, https://doi.org/10.1016/j.ceramint.2015.04.073. [36] P.R. de Matos, A.L. de Oliveira, F. Pelisser, L.R. Prudêncio, Rheological behavior of Portland cement pastes and self-compacting concretes containing porcelain polishing residue, Constr. Build. Mater. 175 (2018) 508–518, https://doi.org/ 10.1016/j.conbuildmat.2018.04.212. [37] F. de Larrard, C.F. Ferraris, T. Sedran, Fresh concrete : A HerscheI-Bulkley material, Mater. Struct. 31 (1998) 494–498, https://doi.org/10.1007/ BF02480474. [38] ASTM, ASTM C143: Standard Test Method for Slump of Hydraulic-Cement Concrete, ASTM International, 2015, pp. 1–4. doi: 10.1520/C0143. [39] ASTM, ASTM C173: Air Content of Freshly Mixed Concrete by the Volumetric Method 1, Am. Soc. Test. Mater., 14, 2016, pp. 1–9. doi: 10.1520/C0173. [40] A.M. Betioli, P.J.P. Gleize, D.A. Silva, V.M. John, R.G. Pileggi, Effect of HMEC on the consolidation of cement pastes: Isothermal calorimetry versus oscillatory rheometry, Cem. Concr. Res. 39 (2009) 440–445, https://doi.org/10.1016/j. cemconres.2009.02.002. [41] ASTM, ASTM C39: Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens, ASTM International, 2018, p. 8. [42] N. Roussel, C. Stefani, R. Leroy, From mini-cone test to Abrams cone test: Measurement of cement-based materials yield stress using slump tests, Cem. Concr. Res. 35 (2005) 817–822, https://doi.org/10.1016/j. cemconres.2004.07.032. [43] B. Esmaeilkhanian, K.H. Khayat, A. Yahia, D. Feys, Effects of mix design parameters and rheological properties on dynamic stability of selfconsolidating concrete, Cem. Concr. Compos. 54 (2014) 21–28, https://doi. org/10.1016/j.cemconcomp.2014.03.001. [44] D. Feys, K.H. Khayat, R. Khatib, How do concrete rheology, tribology, flow rate and pipe radius influence pumping pressure?, Cem Concr. Compos. 66 (2016) 38–46, https://doi.org/10.1016/j.cemconcomp.2015.11.002.

11

[45] C.F. Ferraris, F. de Larrard, Testing and Modelling of Fresh Concrete Rheology, US Department of Commerce, Technology Administration, National Institute of Standards and Technology, 1998, p. 61. [46] P.K. Mehta, P.J.M. Monteiro, Concrete Microstructure, Properties and Materials, 2015. doi: https://doi.org/10.1036/0071462899. [47] A. Zingg, F. Winnefeld, L. Holzer, J. Pakusch, S. Becker, L. Gauckler, Adsorption of polyelectrolytes and its influence on the rheology, zeta potential, and microstructure of various cement and hydrate phases, J. Colloid Interface Sci. 323 (2008) 301–312, https://doi.org/10.1016/j.jcis.2008.04.052. [48] N. Roussel, G. Ovarlez, S. Garrault, C. Brumaud, The origins of thixotropy of fresh cement pastes, Cem. Concr. Res. 42 (2012) 148–157, https://doi.org/ 10.1016/j.cemconres.2011.09.004. [49] A.M. Mostafa, A. Yahia, New approach to assess build-up of cement-based suspensions, Cem. Concr. Res. 85 (2016) 174–182, https://doi.org/10.1016/j. cemconres.2016.03.005. [50] R. Talero, C. Pedrajas, M. González, C. Aramburo, A. Blázquez, V. Rahhal, Role of the filler on Portland cement hydration at very early ages: Rheological behaviour of their fresh cement pastes, Constr. Build. Mater. 151 (2017) 939– 949, https://doi.org/10.1016/j.conbuildmat.2017.06.006. [51] R.J. Flatt, I. Schober, Superplasticizers and the rheology of concrete, in: Underst. Rheol. Concr., Woodhead Publishing, Cambridge,, 2012, pp. 144–208, https://doi.org/10.1533/9780857095282.2.144. [52] D. Lowke, C. Gehlen, The zeta potential of cement and additions in cementitious suspensions with high solid fraction, Cem. Concr. Res. 95 (2017) 195–204, https://doi.org/10.1016/j.cemconres.2017.02.016. [53] P.P. Li, Q.L. Yu, H.J.H. Brouwers, Effect of PCE-type superplasticizer on early-age behaviour of ultra-high performance concrete (UHPC), Constr. Build. Mater. 153 (2017) 740–750, https://doi.org/10.1016/j.conbuildmat.2017.07.145. [54] A.M. Mostafa, A. Yahia, Physico-chemical kinetics of structural build-up of neat cement-based suspensions, Cem. Concr. Res. 97 (2017) 11–27, https://doi.org/ 10.1016/j.cemconres.2017.03.003. [55] G.V. Franks, Zeta potentials and yield stresses of silica suspensions in concentrated monovalent electrolytes: isoelectric point shift and additional attraction, J. Colloid Interface Sci. 51 (2002) 44–51, https://doi.org/10.1006/ jcis.2002.8250. [56] A. Kashani, J.L. Provis, G.G. Qiao, J.S.J. Van Deventer, The interrelationship between surface chemistry and rheology in alkali activated slag paste, Constr. Build. Mater. 65 (2014) 583–591, https://doi.org/10.1016/ j.conbuildmat.2014.04.127. [57] J.Y. Petit, E. Wirquin, K.H. Khayat, Effect of temperature on the rheology of flowable mortars, Cem. Concr. Compos. 32 (2010) 43–53, https://doi.org/ 10.1016/j.cemconcomp.2009.10.003. [58] A. Kostrzanowska-Siedlarz, J. Gołaszewski, Rheological properties and the air content in fresh concrete for self compacting high performance concrete, Constr. Build. Mater. 94 (2015) 555–564, https://doi.org/10.1016/ j.conbuildmat.2015.07.051. [59] P.R. de Matos, R.D. Sakata, L.R. Prudêncio Jr., Eco-efficient low binder highperformance self-compacting concretes, Constr. Build. Mater. 225 (2019) 941– 955, https://doi.org/10.1016/j.conbuildmat.2019.07.254. [60] A. Schöler, B. Lothenbach, F. Winnefeld, M. Ben Haha, M. Zajac, H.M. Ludwig, Early hydration of SCM-blended Portland cements: a pore solution and isothermal calorimetry study, Cem. Concr. Res. 93 (2017) 71–82, https://doi. org/10.1016/j.cemconres.2016.11.013. [61] A. Kumar, S. Bishnoi, K.L. Scrivener, Modelling early age hydration kinetics of alite, Cem. Concr. Res. 42 (2012) 903–918, https://doi.org/10.1016/j. cemconres.2012.03.003. [62] Q. Xu, J. Stark, Early hydration of ordinary Portland cement with an alkaline shotcrete accelerator, Adv. Cem. Res. 17 (2005) 1–8, https://doi.org/10.1680/ adcr.17.1.1.58390. [63] L.R. Prudêncio Jr., Accelerating admixtures for concrete, Cem. Concr. Compos. 20 (1998) 213–219. [64] J. Davidovits, Properties of geopolymer cements, Alkaline Cem. Concr. 1 (1994) 131–149. [65] S. Alonso, A. Palomo, Calorimetric study of alkaline activation of calcium hydroxide–metakaolin solid mixtures, Cem. Concr. Res. 31 (2001) 25–30, https://doi.org/10.1016/S0008-8846(00)00435-X. [66] E. Berodier, K. Scrivener, Understanding the filler effect on the nucleation and growth of C-S-H, J. Am. Ceram. Soc. 97 (2014) 3764–3773, https://doi.org/ 10.1111/jace.13177. [67] H.F.W. Taylor, Cement Chemistry 20 (1997) 335. 10.1016/S0958-9465(98) 00023-7. [68] F. Deschner, F. Winnefeld, B. Lothenbach, S. Seufert, P. Schwesig, S. Dittrich, F. Goetz-Neunhoeffer, J. Neubauer, Hydration of Portland cement with high replacement by siliceous fly ash, Cem. Concr. Res. 42 (2012) 1389–1400, https://doi.org/10.1016/j.cemconres.2012.06.009. [69] K. Scrivener, R. Snellings, B. Lothenbach, A Practical Guide to Microstructural Analysis of Cementitious Materials, CRC Press, 2016. 10.7693/wl20150205. [70] P.R. de Matos, L.R. Prudêncio, A.L. de Oliveira, F. Pelisser, P.J.P. Gleize, Use of porcelain polishing residue as a supplementary cimentitious material in selfcompacting concrete, Constr. Build. Mater. 193 (2018) 623–630, https://doi. org/10.1016/j.conbuildmat.2018.10.228. [71] N. Singh, S.P. Singh, Validation of carbonation behavior of self compacting concrete made with recycled aggregates using microstructural and

12

P.R. de Matos et al. / Construction and Building Materials 230 (2020) 116981

crystallization investigations, Eur. J. Environ. Civ. Eng. (2018) 1–24, https://doi. org/10.1080/19648189.2018.1500312. [72] N. Singh, S.P. Singh, Carbonation resistance and microstructural analysis of low and high volume fly ash self-compacting concrete containing recycled concrete aggregates, Constr. Build. Mater. 127 (2016) 828–842, https://doi. org/10.1016/j.conbuildmat.2016.10.067.

[73] D.P. Bentz, C.F. Ferraris, S.Z. Jones, D. Lootens, F. Zunino, Limestone and silica powder replacements for cement: early-age performance, Cem. Concr. Compos. 78 (2017) 43–56, https://doi.org/10.1016/j. cemconcomp.2017.01.001. [74] J. Haufe, A. Vollpracht, Cement and concrete research tensile strength of concrete exposed to sulfate attack, Cem. Concr. Res. 116 (2019) 81–88, https:// doi.org/10.1016/j.cemconres.2018.11.005.