Effects of elevated temperature exposure on the mechanical properties of recycled fine aggregate concrete

Abstract

ABSTRACT In this work, a compound waste material was made up of raw construction waste concrete, waste tiles, and waste bricks was mixed at a weight ratio of 6:3:1. They were ground into recycled fine aggregates (RFA). RFA substituted the local river sand in proportions of 0%, 30%, 50%, 70%, and 100% for preparing recycled fine aggregate concrete (RFAC) with varied water-to-cement ratios. It intended to explore concrete’s mechanical properties and ultrasonic pulse velocity changes before and after high temperatures (300–800°C). The loss on ignition (LOI) of concrete was simultaneously determined to compare the performance in resisting elevated temperature. Test results presented that the higher the replacement ratio of RFA, the gradually higher the reduction in the concrete splitting tensile, compressive, and residual compressive strengths and ultrasonic pulse velocity after elevated temperature exposure. A rapid reduction was especially found at the heated temperature of exceeding 440°C. Furthermore, the old cement paste adhered to the surface of the raw construction waste had a relatively higher LOI. This led to the consequence that the RFAC had an increased LOI with the increment of the RFA replacement ratio, while the LOI of RFAC dropped with the increment of the originally heated temperature.