Development and performance of sustainable structural lightweight concrete containing waste clay bricks

Utilization of waste crushed bricks (WCB), which are obtained from brick factories and demolition waste as coarse and fine aggregate for preparing concrete, is an adequate strategy to reuse them and save natural resources to achieve environmental sustainability. This study investigates the possibility of developing eco-friendly structural lightweight concrete (SLWC) with a 100% replacement of WCB. Different contents (5%, 10%, and 15%) of supplementary cementitious materials such as silica fume, fly ash, metakaolin, and slag as a replacement by weight of cement were investigated. The slump test, dry density, and mechanical properties (compressive, splitting tensile, and flexural strengths), as well as elevated temperature resistance and water absorption, were evaluated. Microstructure tests, including thermogravimetric analysis, X-ray diffraction and scanning electron microscopy (SEM), were performed. The performance of the developed concrete under high temperature exposure of 200 °C, 400 °C, and 600 °C was evaluated. The experimental results indicated that SLWC can be obtained using WCB as a 100% replacement of aggregate and by using 15% metakaolin and 15% silica fume as alternatives to cement, with a 39.5 and 41.5 MPa compressive strength, respectively. Incorporation of 15% slag as cement replacement exhibited the best performance after 600 °C exposure compared to other fine materials. The SEM images showed an improvement in transition zone characteristics and increased bond between coarse aggregate and cement paste.