Replacement of Fine Aggregate with Refractory Brick Residue in Concrete Exposed to Elevated Temperatures

Abstract

Refractory brick waste, added to the fires originated in structures, makes it possible to bring together two problems to contribute to sustainable construction and introduce new aggregate alternatives in concrete. The objective of the study was to produce concrete with less fine aggregate and to evaluate a more sustainable concrete, using refractory brick residues (RBR) to replace fine aggregate in five percentages 10 %, 20 %, 30 %, 40 % and 50 % to be exposed to direct fire. The design was based on a water-cement w/c ratio of 0.71 and the production of 144 RBR-based concrete specimens. The fresh samples were subjected to slump and fresh unit weight tests, the cylindrical specimens prepared after 28 days of curing were subjected to compressive strength at room temperature and various temperatures (200 to 1 000 °C) for different times of 15, 30 and 60 minutes. In addition, a Three Factor statistical analysis of variance was performed with respect to the compressive strength at 28 days. The results showed that the RBR influences the concrete mix are less workable and reduce the fresh unit weight at higher substitution percentages. On the other hand, the ideal dosage was with the percentage of 40RBR as opposed to the other dosages subjected to heat, being insignificant at 15-minute exposure, but relevant at 30 and 60 minutes. It is concluded that RBR significantly influences the improvement of its mechanical properties under high heat and the amount of residues is limited to a specific dosage, providing a sustainable constructive approach to direct controlled fire exposures.