Percolação de água em concretos com elevados teores de escoria e cinza volante com adição de cal

Abstract

The study of concrete structures durability necessarily passes by the study of covercrete and by the understanding of the factors that affect the features of this superficial layer. The use of high contents of mineral addictions on the concrete influences meaningfully the resistance of the covering layer to the chemical attack and on the pores structure. This dissertation aimed to analyze, through the obtained results in the tests of capillary water absorption, according to the RILEM TC 116 PCD Recommendation, and to the diffusion of water held following the directives DAN et al (1988) presented by Isaia (1995), based on publications of CSTB, the percolation of water on concrete covering layer, besides co-relating with the resistance to 50 MPa, the total volume of intruding mercury and the critical diameter of the pores. To these analysis perform, prototypes specimens of 75 cm x 20cm x 15cm have been molded with high contents of mineral additions, 70 % of slag and 20% of fly ash, in replacement to the cement mass, with or without addition of 20% of hydrated lime, in mass, and w/cm relationships 0,3 ; 0,4 ; 0,5 besides the reference mix proportion, only with cement and w/cm relationships 0,4; 0,6 e 0,8. The tests of capillary absorption and water diffusion were held, on the 91 and 300 days to execute the comparative study between these two ages, extracted specimens of 10 cm x 20 cm, from the prototypes had been accomplished, being closed to 0, 2,5 e 5,0cm of depth from the surface. After performing the analysis, it has been noticed that the replacement of cement by mineral additions causes a strength reduction to the compression, being it more accentuated in the initial ages and eased as the time passes by. In relation to the coefficients of water absorption and diffusion of the concretes with mineral additions compared to the reference concretes in equality of w/cm and ages, being analyzed the use of additions, meaningful reductions that get to 79% in the absorption and 69% in the diffusion, on the 300 day. When analyzed considering the depth (in equality of w/cm) the layer reduction 3 (5cm) in relation to 1(0,5cm) gets to 55% in the absorption and 31% in the diffusion, on the 300 day, and in the mix proportion with addition of hydrated lime, justifiable by the fact of the hydrated lime stored water helping in the hydrating process producing a more compact matrix. In equality of 50 Mpa compressive strength, the reductions are 86% to the absorption and 70% to the diffusion. It s been noticed, as to the absorption as to the diffusion, a strong co-relation with the intruding total volume and the pores diameter on the 300 day.