Abstract
Abstract With the increasing use of recycled materials from civil construction, mainly as substitute for some aggregates in concrete mixtures, it is necessary to obtain technical information on the performance of these new mixtures. National and international research on the use of ceramic waste in concrete production highlight good results of this new material’s mechanical performance in environmental situations. However, little is known about its behavior at high temperatures. In this context, we sought to verify the performance of concrete mixtures produced with aggregates from ceramic block waste at high temperatures, with evaluation of their residual mechanical strength, axial compressive strength and elastic modulus, and also their tendency to spalling in fire situations. The RILEM-129 MHT method [1] was used for the assessment of residual mechanical strength, and the tendency to spalling was evaluated according to the procedure suggested by Souza and Moreno [2]. In both these evaluations, there is no national standard, and, in the case of spalling, not even an international standard. Three concrete mixtures were used, one prepared with natural coarse basalt aggregate (reference) and the other two by replacing part of this natural aggregate with aggregate from ceramic block waste (40% and 100% of substitution in volume). In the end, it is concluded that the substitution of natural coarse aggregate for lightweight aggregate from ceramic block waste can be an excellent alternative to increase the resistance of concrete to fire. Thus, the results of mechanical strength and spalling in a fire situation, unprecedented in our country, can greatly support the decision-making about the use of this alternative material in the national construction industry.
Highlights
Due to population growth, humanity is currently facing the problem of the generation of large amounts of garbage and waste
It should be noted that in the case of National Standard NBR 15200 [13] and EUROCODE 2 [15], the recommended values are inherent to concretes made of silica aggregates and, the texts of these codes do not make this clear, they refer to unloaded samples ruptured by axial compression under heating, a load history which, admittedly, results in higher residual mechanical strength values than those obtained with unloaded samples tested after slow cooling
In Figure [2], it can be seen that replacing the coarse aggregate with red ceramic waste results in concretes that are more resistant to fire, i.e., the strength losses for concretes with 40% and 100% of substitution are lower compared to the reference sample
Summary
Humanity is currently facing the problem of the generation of large amounts of garbage and waste. Yan et al [24] produced cylindrical concrete samples with 50mm in diameter and 50mm in height using recycled aggregates, and evaluated their residual mechanical strength after heating. An overview of the international results on the residual mechanical strength of lightweight concrete mixtures made with alternative materials after heating is presented, and it is important to highlight the significant difference between them. This fact justifies this work, the results of which will be added to the existing ones, contributing to a better understanding of the behavior of these alternative lightweight concretes at high temperatures
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