Dry ripened mortar with quarry waste and rubber powder from unserviceable tires/Argamassa maturada seca com residuos de pedreira e po de borracha de pneus inserviveis.
The growing demand for materials used in civil construction in Brazil is increasing every year. With this, the consumption of raw materials increases, including natural sand which is mostly extracted from riverbeds, and causing damages to the environment. Government agencies such as IBAMA (Brazilian Institute of Environment and Renewable Natural Resources) have restricted this practice as a form of environmental conservation.
An alternative material to replace the natural sand is the quarry waste, called stone-quarry fines or artificial sand, resulting from the process of crushed stone production in quarries. This material has been examined for use in mortar and concrete replacing natural sand.
One of the factors that distinguish artificial from natural sand is the higher content pulverulent materials. For Bonavetti and Irassar (1994) accelerating cement hydration due to the effect of stone dust contributes to gain strength at early ages, and with this there are drying shrinkage and a positive effect of filler, increased water retention and improved plasticity. Jadhav and Kulkarni (2012) also reported an increase in mechanical properties, in addition to the reduction in workability, requiring increased water consumption, although the authors have obtained a more cohesive concrete.
Ilangovana et al. (2008) also verified a higher drying shrinkage in concrete with artificial sand, but the permeability was lower given the increased content of fines. And Donza and Cabrera (2002) mentioned that the increase in mechanical properties, even with a higher water / cement ratio, can be associated with the improvement of the paste-fine aggregate transition zone, which can be attributed to the rough texture of the artificial sand.
By using up to 15% artificial sand in high-performance concrete, Beixing et al. (2009) verified that it had not affected the permeability of chloride ions, freezing and thawing. However, in low strength concrete the freezing was affected. Raman et al. (2011) evaluated the high-performance concrete with artificial sand and rice husk ash, and obtained a negative impact for the workability in fresh concrete, but it was compensated with a good dosing design, and by the use of a superplasticizer and a mixture of rice husk ash.
An alternative material with characteristics and conditions to be used to reduce the drying shrinkage and crackings in mortar lining with stone-quarry fines is the rubber powder from unserviceable tires, which can be used either as replacement or in addition to mortar and concrete. Several authors have developed studies with this material as rubber aggregate of various sizes (SEGRE et al., 2004; HERNANDES-OLIVARES et al., 2004; GANJIAN et al., 2009; MOHAMMED, 2010).
In the study conducted with rubber aggregate in concrete, Ho et al. (2012) achieved a reduction in the brittle index of concrete with increasing rubber content and reached nearly zero with 40%, and that the kinetics of the fracture process of concrete with rubber is slower in relation to concrete without rubber. For Turatsinze and Garros (2008) despite the reduction in tensile and compressive strength of concrete, there was an improvement in the ability to absorb deformation and a reduction in potential detrimental effect of cracking, while the study of Turatsinze et al. (2007) showed that free shrinkage is improved as well as the reduction of cracking of resistant mortar.
Canova et al. (2012) analyzed mortar of quicklime and natural sand (which was oven-dried and added of rubber powder from unserviceable tires), and observed an improvement in relation to conventional mortar, with reduced water exudation, free shrinkage and cracking. The addition of 8% rubber powder from unserviceable tires was the most suitable ratio. In other study of Canova et al. (2009), the water absorption by capillarity was significantly reduced by adding rubber powder for the oven-dried mortar, and still reduced drying shrinkage with restricted surface and the void content, besides presenting a mortar with great tenacity
In this study we examined the plastering mortar with artificial sand replacing natural sand, and addition of 8% rubber powder form unserviceable tires, in which it was used the process described in Canova et al. (2012) that resulted in dry ripened mortar and established that this addition was the most suitable.
In this way, we sought to minimize environmental impacts problems and mainly to reduce the cracking of coatings, which were more pronounced in mortars with artificial sand.
Material and methods
In order to compose the volumetric proportion of mortars, it was used powder quicklime type CV--C (common quicklime), artificial sand (stone-quarry fines), natural river sand, class 32 compound Portland cement (CP II Z--32) and addition of rubber powder from ground unserviceable tires with diameter below 0.5 mm. The characterization of materials and of the addition employed is presented in Tables 1--6.
Simple mortars were prepared with quicklime and fine aggregate (artificial and natural sand) both in volumetric proportions of 1:6, were previously prepared in a 320-L inclined axle cement mixer and ripened for seven days in metal containers for quicklime hydration in laboratory ambient. After maturation, the mortar mass was determined and it was dried into a constant mass in an oven at (105 [+ or -] 10)[degrees]C. The dry mortar mass was determined and then it was grinded and sieved with a mesh of (2.4 mm), packed in grained state in plastic bags and stored for 60 days in closed dry wooden containers. Ripened and dried mortars were tested with cement composing the volumetric proportions of 1:1.5:9--equivalent in weight 1:0,993:9.623 and added 8% rubber powder from unserviceable tires and named as:
[As.sup.0.sub.RP]--Oven-dried mortar with artificial sand (stone-quarry waste), packed, and stored for 60 days. The index '0' indicates reference mortar, that is, without rubber powder and likewise [As.sup.0.sub.AN]--with natural sand.
[As.sup.8.sub.RP]--Oven-dried mortar with artificial sand. The index '8' indicates the addition of 8% rubber powder and likewise [As.sup.8.sub.AN]--with natural sand.
The volumetric proportion of ripened and dried mortars was evaluated through properties at plastic and hardened states, by means of standardized laboratory tests, as presented in Table 7. For testing mortars in the hardened state were molded the series with six cylindrical specimens with 5 cm diameter and 10 cm height, for all tests developed and tested with 28 days of age.
Crackings--It was measured the length of visible crackings on mortar panels with 1.5 cm thickness, in the dimension of 1.0 m2, with 1:3 usual roughcast (cement and sand, by volume), on ceramic block masonry at once, in environment outside of the laboratory. Measurements were taken with 24 hours and after 90 days.
Results and discussions
Results in the plastic state
Table 8 shows the ratio parameters of the mortars.
Specific gravity and void content
In Figure 1 is observed the increase in specific gravity in the plastic state for the ripened dried mortar with stone-quarry wastes in relation to natural sand. This is due to the higher specific gravity of the quarry waste. However, with the addition of rubber powder that has low specific gravity, there was a decrease for both mortars.
The dried mortar with quarry waste presented a reduction in the incorporated air content (Figure 2). This may have occurred owing the greater amount of pulverulent material of the artificial sand compared with natural sand. As for the rubber powder, there was an increase in air content because the rubber grain has a lower compactness.
A sharp reduction was found in water bleeding from dried mortar with quarry waste in relation to natural sand (Figure 3). In the same way, a decrease for both mortars with 8% rubber powder was observed, with a greater reduction for mortar with quarry waste. The rubber powder and the fine material from artificial sand may have favored the closure of the pore structure of the mortar, contributing to reduce the water bleeding.
The ripened dried mortar with quarry waste presented a greater retention of water compared with the mortar with natural sand (Figure 4), due to the higher amount of fines in the aggregate. The addition of rubber powder contributes even more for the closure of the pore structure of the mortar, generating thus a greater retention of water in the mortar with artificial sand in relation to the mortar with natural sand.
Hardened state results
Axial compressive strength
There was a slight increase in axial compressive strength at 28 days for the dried mortar with artificial sand in comparison with natural sand (Figure 5). This probably occurred given the reduction in incorporated air content, which leads to a higher compactness, directly proportional to the higher compressive strength; this corroborates the observations made by Bonavetti and Irassar (1994), with reduction for both mortars with addition of rubber powder, once it presented a low mechanical strength.
Static deformation modulus
The static deformation modulus of the dried mortar with artificial sand was slightly higher than of the mortar with natural sand (Figure 6), as also observed for the compressive strength. The addition of rubber powder led to a reduction in static deformation modulus, in the same way with further reduction for the mortar with natural sand, presenting an improvement in the ability to absorb deformation; confirming the observations of Turatsinze and Garros (2008).
Water absorption by capillarity
The water absorption by capillarity of the dried mortar with artificial sand was higher than of the mortar with natural sand (Figure 7). The greater content of fines in the artificial sand might have led to a greater microcraking of this mortar, or even to a reduction in the radius of capillary, increasing thus the surface tension. Considering the addition of 8% rubber powder, although with lower rates, the mortar with artificial sand also had a much higher capillarity rate compared with the mortar with natural sand, and a much shorter time to reach the top of the specimen, as registered by Canova et al. (2009).
The mortar with artificial sand cracked more than the mortar with natural sand (Figure 8), probably due to the higher amount of fines present in the quarry waste.
Besides, with 24 hours the incidence of crackings was higher than at 90 days. The addition of rubber powder has positively contributed to both mortars. This may have occurred due to increased retention of water and/or reduction in deformation modulus. Figure 9 illustrates the total sum of crackings of times of 24 hours and 90 days. The mortar with quarry waste had a higher amount of crackings than the mortar with natural sand.
Replacement of the natural sand in the quarry waste in dried mortar contributed to reduction in water bleeding, increase in compressive strength and water retention. But reduced the void content and increased the static deformation modulus and visible cracking.
The addition of rubber powder in dried mortar with quarry waste contributed to the increase in void content and water retention, with reducing to the water bleeding, water absorption by capillarity and significantly reduced the appearance of visible cracking. Although there was been decrease in mechanical properties. We conclude that use of 8% rubber powder is feasible to reduce cracking.
AB NT-Associacao Brasileira de Normas Tecnicas. NBR 7251: agregados em estado solto: determinacao da massa unitaria: metodo de ensaio. Rio de Janeiro: ABNT, 1982.
ABNT-Associacao Brasileira de Normas Tecnicas. NBR 8522: concreto: determinacao do modulo de deformacao estatica e diagrama--tensao deformacao: metodo de ensaio. Rio de Janeiro: ABNT, 1984.
ABNT-Associacao Brasileira de Normas Tecnicas. NBR 7217: agregados em estado solto: determinacao da composicao granulometrica: metodo de ensaio. Rio de Janeiro: ABNT, 1987.
ABNT-Associacao Brasileira de Normas Tecnicas. NBR MB 3432: cimento portland: determinacao da finura por meio da peneira 75 pm (no 200). Rio de Janeiro: ABNT, 1991.
ABNT-Associacao Brasileira de Normas Tecnicas. NBR 13276: argamassa e revestimentos de paredes e teto: determinacao do teor de agua para obtencao do indice de consistenica-padrao: metodo de ensaio. Rio de Janeiro: ABNT, 1995.
ABNT-Associacao Brasileira de Normas Tecnicas. NBR 13277 argamassa para assentamento de paredes e revestimentos de paredes e teto: determinacao da retencao de agua--argamassa de revestimento: metodo de ensaio. Rio de Janeiro: ABNT, 1995.
ABNT-Associacao Brasileira de Normas Tecnicas. NBR 13278: argamassa e revestimentos de paredes e teto: determinacao da densidade de massa e do teor de ar incorporado: metodo de ensaio. Rio de Janeiro: ABNT, 1995.
ABNT-Associacao Brasileira de Normas Tecnicas. NBR 13279: argamassa para assentamento de paredes e revestimentos de paredes e teto: determinacao da resistencia a compressao: metodo de ensaio. Rio de Janeiro: ABNT, 1995.
ABNT-Associacao Brasileira de Normas Tecnicas. NBR 9779: argamassa para assentamento de paredes e revestimentos de paredes e teto: determinacao da absorcao de agua por capilaridade: metodo de ensaio. Rio de Janeiro: ABNT, 1995.
ABNT-Associacao Brasileira de Normas Tecnicas. NBR 7215: cimento portland: determinacao da resistencia a compressao. Rio de Janeiro, 1995.
ABNT-Associacao Brasileira de Normas Tecnicas. NBR NM 23: cimento portland: determinacao da massa especifica. Rio de Janeiro: ABNT, 1998.
ABNT-Associacao Brasileira de Normas Tecnicas. NBR 9289: cal hidratada para argamassas: determinacao da finura: metodo de ensaio. Rio de Janeiro: ABNT, 2000.
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RILEM-International Union of Testing and Research Laboratories for Materials and Structures. MR--6: tendency of water to separate from mortars (bleeding). France: Rilem, 1982.
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Received on February 25, 2013.
Accepted on February 2, 2014.
Jose Aparecido Canova (1), Generoso De Angelis Neto (1) and Rosangela Bergamasco (2)
(1) Departamento de Engenharia Civil, Universidade Estadual de Maringa, Av. Colombo, 5790, 87020-900, Maringa, Parana, Brazil. (2) Departamento de Engenharia Quimica, Universidade Estadual de Maringa, Maringa, Parana, Brazil. * Author for correspondence. E-mail: firstname.lastname@example.org
Table 1. Physical and mechanical characteristics of the Portland cement (CP II Z-32). Tests Results Methods Start 2 hours and Setting time 50 minutes NBR 7215 End 7 hours and (ABNT, 1995) 18 minutes Normal consistency Water / cement NBR 7215 ratio = 0.30 (ABNT, 1995) Fineness--(% retained on 1.62 MB 3432 sieve # 200) (ABNT, 1991) Unit weight (g [cm.sup.-3]) 1.45 NBR 7251 (ABNT, 1982) True density (g [cm.sup.-3]) 3.09 NM 23 (ABNT, 1998) Compressive strength (MPa) 34.7 NBR 7215 at 28 days (ABNT, 1995) Table 2. Physical characteristics of quicklime powder dolomitic. Tests Results Limits CV-C Methods Unit weight 0.96 -- NBR 7251 (ABNT, 1982) (g [cm.sup.-3]) True density 3.10 -- NM 23 (ABNT, 1998) (g [cm.sup.-3]) Fineness--(% retained) sieve # 30 0.7 [less than or NBR 9289 equal to] 5.0 (ABNT, 2000) sieve # 200 0.22 [less than or equal to] 30 Table 3. Physical characteristics of the fine aggregate--fine washed river sand. Tests Results Methods Unit weight 1.55 NBR 7251 (g [cm.sup.-3]) (ABNT, 1982) True density gravity 2.63 Pycnometer (g [cm.sup.-3]) Sieve (mm) Accumulated % retained Particle size 2.4 0 distribution 1.2 1 NBR 7217 0.6 7 (ABNT, 0.3 67 1987) 0.15 99 max [empty set] 1.2 (mm) 1.74 Fineness modulus Table 4. Physical characteristics of the rubber powder. Determination Results Methods Unit mass 0.44 NBR 7251 (g [cm.sup.-3]) (ABNT, 1982) True density 0.79 Pycnometer (g [cm.sup.-3]) Sieve (mm) Accumulated % retained Particle size 0.6 0 NBR 7217 distribution 0.3 34 (ABNT, 1987) 0.15 99 [empty set] 0.42 max (mm) 1.33 Fineness modulus Table 5. Chemical characteristics of the rubber powder--weight in mg [kg.sup.-1]--analysis--atomic absorption spectrometry. Fe Cu Mn Zn Pb Cd Cr (total) Ni 710.00 52.60 Nd * 646.00 108.00 Nd * 32.00 4.00 Note: * Nd = not detected Table 6. Characteristics of the fine aggregate (artificial sand--stone-quarry fines). Determination Results Methods Unit mass 1.7876 NBR 7251 (g [cm.sup.-3]) (ABNT, 1982) True density 2.93 Pycnometer (g [cm.sup.-3]) Sieve (mm) Accumulated % retained 4.8 0 2.4 1 1.2 34 Particle size 0.6 50 NBR 7217 distribution 0.3 69 (ABNT, 1987) 0.15 85 0.075 96 max [empty set] 2.4 (mm) Fineness modulus 2.39 Table 7. Measured properties at plastic and hardened states. State Properties Methods Observations Plastic Consistency NBR 13276 index (ABNT, 1995) Specific gravity NBR 13278 and (ABNT, 1995) incorporated void content Water NBR 13277 The filter paper discs retention (ABNT, 1995) used had 80 g [m.sup.-2] weight and air permeability of 26 l [s.sup.-1] [m.sup.2]. Water MR-6 With measurement in bleeding RILEM (1982) weight, in five samples in times of 15 min., 30 min., 60 min. and 120 min. Hardened Axial NBR 13279 compressive (ABNT, 1995) strength Static NBR 8522 In the initial tangent deformation (ABNT, 1984) module, the loading speed modulus was 0,05 MPa [s.sup.-1] Water absorption NBR 9779 by capillarity (ABNT, 1995) Table 8. Ratio parameters of the mortars. Water / Water / Water / Aggregate / Mortar dry materials cement binders binders ratio ratio ratio ratio (mass) (mass) (mass) (mass) [As.sup.0.sub.RP] 0.216 2.59 1.356 5.27 [As.sup.0.sub.AN] 0.231 2.64 1.328 4.79 [As.sup.8.sub.RP] 0.207 2.52 1.322 5.39 [As.sup.8.sub.AN] 0.224 2.60 1.289 4.90
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|Title Annotation:||texto en ingles|
|Author:||Canova, Jose Aparecido; De Angelis Neto, Generoso; Bergamasco, Rosangela|
|Publication:||Acta Scientiarum. Technology (UEM)|
|Date:||Jan 1, 2015|
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