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Proceedings of the 11th International Conference on Non-conventional Materials and Technologies (NOCMAT 2009) 6-9 September 2009, Bath, UK

INFLUENCE OF WATER/CEMENT RATIO IN MORTARS CONSTITUTED BY KAOLIN WASTES

Aline Figueiredo da Nóbrega 1, Sandro Marden Torres 2, Givanildo Alves de Azeredo 3 Normando Perazzo Barbosa 4

Civil Engineering Post Graduate course, Federal University of Pernambuco 2 Department of Mechanical Engineering, Federal University of Paraíba 3,4 Department of Civil and Environmental Engineering, Federal University of Paraíba Abstract: Industrial wastes are responsible for a great part of environment deterioration. The construction industry has the potential to absorb some of these wastes, in the use of mortars and concrete production. In this paper kaolin wastes were used to replace part of or total lime for the manufacture of mortars. These mortars were studied to determine the influence of water/cement ratio on compressive strength. The results were compared with those obtained for cement-lime mortars. Water content was fixed by the flow table standard. The influence of water/cement ratio was more important for the kaolin waste mortars than for cement-lime mortars. Keywords: Kaolin wastes, mortars, compressive strength, water/cement ratio 1 Introduction In recent years, environmental problem impacts caused by different pollution sources have been widely discussed in the world. Among them, the production of urban and industrial wastes has caused preoccupations. They are deposited in large areas, both in urban and natural areas. This generates environmental problems. The civil construction sector is potentially a great option for the use of recycled and industrial by-products (John 1999). Construction sector is responsible for a great part of the consumption of natural resources extracted in the world. This consumption CAN reach 75% of the total (John 2000). Moreover, the sector is engaged in highly polluting industrial processes, such as the manufacture of cement, lime and steel products in general. The mining off kaolin is of great importance for the socio-economic activities in Brazil. According to the Brazilian Mineral Resume 2007 (DNPM, 2007), together the USA, Community of Independent States, South Korea, Czech Republic, Brazil and the United Kingdom are responsible for 62% of all kaolin produced worldwide. But Brazil is the only country to export and import the mineral already benefited. The kaolin industry, in its process of treatment in order to get benefited kaolin, produces a large amount of waste. In this process, two types of kaolin wastes are

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1 2

Doctorate Student, [email protected] Professor and Researcher, [email protected] 3 Professor and Researcher, [email protected] 4 Professor and Researcher, [email protected]

commonly produced: one presenting a sandy texture (SKW), and the other containing fines as a clay (CKW). Kaolin wastes are not properly disposed in the environment. They are placed anywhere in the open air. The irregular disposal of kaolin wastes has turned into a problem for the residents in the surrounding areas of cities. Some studies have shown the potential of these residues in mortars. Based on a research developed by Nóbrega (2007), the aim of this study is to evaluate the influence of water/cement (w/c) in the behaviour of mortar containing kaolin wastes and compare it to Abrams' model. 2 Experimental Procedure 2.1 Materials and Physical features Both types of kaolin wastes are used. Their mineralogical composition contains kaolinite, mica, quartz, and calcite (Nóbrega, 2007). Tap water, from the Federal University of Paraíba, was used for all mortar formulations. For the physical characterization of materials the following tests were performed: specific density of fine materials was determined according to the bottle of Le Chatelier as NBR 6474 (1984); for river sand and SKW it was used the bottle of Chapman according to NBR 9776 (1987). Apparent density was measured as NBR 7251 (1982), and specific surface area (Blaine fineness) for fine materials according to NBR NM 76 (1996). Particle size distribution of river sand and sandy kaolin wastes (SKW) is presented in the study of Nóbrega et. al (2007). It is shown that for the range of sieves adopted, with meshes among 1.20 mm, 0.60 mm, 0.30 mm and 0.15 mm, SKW provides a greater amount of fines compared to the river sand. While the fine sand of the river consists primarily of quartz, SKW fines are predominantly composed of kaolinite and mica as Nóbrega (2007) and Nóbrega et al (2005) can attest. Physical features of materials used in this research are listed in Table 1. Table 1. Physical features of materials

Material Hydrated Lime Sandy kaolin waste (SKW) Clay kaolin waste (CKW) Portland Cement River sand Admixture Specific Density (g/cm3) 2.27 2.64 Apparent Density (g/cm3) 0.43 1.30 Specific Surface Area (Blaine) (cm2/g) 12,074 Wastes from kaolin beneficiation, located in Juazeirinho village, in Paraíba State, Brazil. 2.58 0.66 2,820 Description CH-I, from local trade;

Portland cement constituted by stone filler. Compressive strength 28 days 32 MPa (CPII F 32). 2.65 1.60 Fineness modulus = 1.91. plasticizer composed by natural resins. Density 1.01 g/cm3 3.15 1.08 4,289

2.2 Mortars Formulations Mass ratios were used for the mortars formulations manufacture and they are listed in Table 2. Water was added to mixtures in order to produce a flow as measured on flow table of 255 ± 10 mm (Brazilian Standard, NBR 13276, 1995). 2

Table 2. Mortars formulations by mass ratio

Mix River Cement Lime CKW SKW name Sand M1 1 1 4 M2 1 1 4 M3 1 0,5 0,5 4 M4* 1 0,5 4 M5* 1 4 M6 1 2 8 M7 1 2 8 M8 1 2 8 M9 1 2 8 *formulations with admixture. Used quantity as indicated by specifications of product.

2.3 Sample Preparation and Compressive Strength Test Mortars cylindrical specimens of 50mm x 100mm were cast. After 24 hours of setting, the specimens were de-moulded and cured for 28 days in water at room temperature (26 ± 2°C). Compressive strength test followed according to the Brazilian standard (NBR 7215). 3 Results and Discussions In Table 3, both mean compressive strength at 28 days old and the w/c ratio are listed. Table 3: Compressive strength average values at 28 days old and w/c ratio of mortars.

Mix name M1 M2 M3 M4 M5 M6 M7 M8 M9 w/c ratio 1.68 1.56 1.32 1.41 1.06 3.09 3.27 2.41 2.27 Compressive strength 28 days (MPa) 1.87 2.26 2.15 2.39 4.12 0.66 0.67 1.43 2.07

Among mixes M1 to M5 (1:1:4 ­ mortar proportion by mass ratio), the M1 presented the highest w/c ratio, containing only the SKW waste. Differently, for mixes M6 to M9, the w/c ratio was greater for the formulation contained by SKW and CKW wastes. For M1 mix, the largest amount of water was caused by lime fines, as lime is finer than CKW. M6 contains more fines than M7. Normally, a mix containing more fines means important values of specific surface area, requiring more water for the same workability. But, as M7 mix presented neither a good homogeneity nor a good plasticity, more water was added to improve these properties. With this additional water, the mortar could be tested in flowing table in order to obtain the same workability value, which was not possible due to aggregate interlock caused by absence of fines. The influence of the w/c ratio in compressive strength at 28 days old for all mortars, compared with the Abrams' curve is shown in Figure 1.

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Real Compressive Strength 28 days (MPa)

18 16 14 12 10 8 6 4 2 0 0 1 2

Model Expon. (Model)

Abrams Model: CS(MPa)=102.26/(16.40)^(a/c)

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Lime efect Filler efect 4 (SKW fines)

water/cement ratio

Figure 1: w/c ratio versus compressive strength at 28 days It can be observed that, in general, compressive strength reduction (CS) occurred when w/c ratio increased. The performance, in both 1:1:4 and 1:2:8, mixtures occurs similarly to the Abrams' curve (model). But lime and kaolin wastes caused filler effect in the mixtures. Model Abrams' follows the equation 1. CS=K1/K2(w/c) (1)

K1 and K2 are constant for the cement and the w/c ratio values. Other mixtures of mortars constituted by kaolin waste were studied by Nóbrega (2007) where the results also showed the same behaviour presented in Figure 1. In Figure 2 the difference between real compressive strength values and Abrams' model compressive strength values of mortars is shown according to w/c ratio variation.

2.5 Difference between Real Compressive Strength - Abrams model Compressive Strength 2 1.5 1 0.5 0 0 -0.5 -1 -1.5 0.5 1 1.5 2 2.5 3 3.5

Abrams Model: RCS(MPa)=102,26/(16,40)^(a/c)

w/c ratio

Figure 2: Difference between real compressive strength and Abrams' model for compressive strength versus w/c ratio.

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Compressive strength curve behaviour as a function of w/c ratio of the mortar type 1:1:4, is shown in Figure 3. For coefficients of the curve with different values from those considering only the pure cement as responsible for compressive strength, a similar behaviour to Abrams' model is observed. In this case, for example, considering a mixture well vibrated, K1 coefficient values was 16.19 to 20.91, quite below the values for the pure cement, where K1 = 102.26.

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Compressive Strength 28 days (MPa)

mortar proportion K1

K2

4

1:1:4 1:2:8

16.19 20.91

3.84 2.95

1:1:4

3

cem : (CKW and/or lime) : SKW

real model Model A Model B Expon. (model) Expon. (Model A) Expon. (Model B)

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cem : (CKW or Lime) : river sand or SKW

1:2:8

1

model

0 1 1.5 2 2.5 3 3.5

water/cement ratio

Figure 3: Comparison Abrams' model and w/c ratio of kaolin wastes mortars and cement-lime mortars.

Mortars of type 1:1:4 (proportion by mass) showed greater compressive strength, as expected, due to a lower aggregate proportion. Compressive strength decreased more intensely for the mortars 1:1:4 according to w/c ratio variation. This may indicate the role of lime binders, while CKW appears to have behaved as filler material. 4 Conclusions Considering the results it can be said that the fines of kaolin wastes caused filler effect in mortars. Both 1:1:4 and 1:2:8 mortars have shown different behaviour from Abrams' model curve. This difference was also observed in each formulation type. This behaviour difference was caused by lime and kaolin waste. Mortars 1:1:4 have presented slight variation values for w/c ratio and compressive strength compared to mortars 1:2:8. This means a better effect of the use of both types of kaolin wastes simultaneously, as well as in its use in aggregate.

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5 References ABNT, NBR 13281, 2001 ­ Argamassas de assentamento e revestimento: requisitos. Associação Brasileira de Normas Técnicas, Rio de Janeiro. ABNT, NBR 6474, 1984 - Cimento Portland e outros materiais em pó: determinação da massa específica. Associação Brasileira de Normas Técnicas, Rio de Janeiro. ABNT, NBR 7251, 1982 - Agregado em estado solto - Determinação da massa unitária. Associação Brasileira de Normas Técnicas, Rio de Janeiro; ABNT, NBR NM 76, 1998 - Determinação da finura pelo método de permeabilidade ao ar (Método Blaine). Associação Brasileira de Normas Técnicas, Rio de Janeiro. ABNT, NBR 9776, 1987- Agregados ­ Determinação da massa específica de agregados miúdos por meio de frasco de Chapman, Associação Brasileira de Normas Técnicas, Rio de Janeiro ABNT, NBR NM 248, 2003 - Agregados: Determinação da composição granulométrica. Associação Brasileira de Normas Técnicas, Rio de Janeiro. ABNT, NBR 13276,1995 - Argamassa para assentamento de paredes e tetos Determinação do teor de água para obtenção do índice de consistência padrão. Associação Brasileira de Normas Técnicas, Rio de Janeiro. DNPM, 2007. Departamento Nacional de Produção Mineral. Balanço Mineral Brasileiro ­ Sumário Mineral. Disponível em:<http://www.dnpm.gov.br > JOHN, V. M., 1999. Panorama sobre a reciclagem de resíduos na construção civil. II Seminário sobre desenvolvimento sustentável e reciclagem na construção civil. In: 41º Congresso Brasileiro do Concreto, 1999, São Paulo. Anais IBRACON, CD-ROM. NÓBREGA, A. F. DA., TORRE, S. M., BARBOSA, N. P., 2007. Uso De Resíduos de Caulim Como Materiais Constituintes Em Argamassas de Múltiplo Uso. IC-NOCMAT 2007. Conferência Internacional de Materiais e Tecnologias Não-Convencionais: Materiais Ecológicos e Tecnologias para Construções Sustentáveis. Maceió-Al, Brasil. NÓBREGA, A. F. DA., 2007. Potencial De Aproveitamento De Resíduos De Caulim Paraibano para o Desenvolvimento de Argamassas de Múltiplo Uso. Dissertação de Mestrado. Engenharia Urbana UFPB, João Pessoa, PB, Brasil. NÓBREGA, A. F., DANTAS, K.C.B., OLIVEIRA, M. P., TORRES, S. M., BARBOSA, N. P., 2005. Avaliação do desempenho de argamassas com o uso de rejeito de caulim industrial como material de substituição do cimento Portland. In: Conferência Interamericana sobre Materiais e Tecnologias não-convencionais na Construção Ecológica e Sustentável, Rio de Janeiro, Brasil.

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