Effects of fire-damaged concrete waste on the properties of its preparing recycled aggregate, recycled powder and newmade concrete

Abstract

Concrete in service is unpredictably exposed to fire attack, while the properties of recycled concrete aggregate (RCA) and recycled concrete powder (RCP) from demolishing fire-damaged concrete have received little consideration until now. This work investigates the effects of fire-damaged concrete waste on the properties of its preparing RCA, RCP and newmade concrete. The results show that the water absorption of RCA from 300 to 800 °C fire-damaged concrete is 39.1–169.5% higher than that of ordinary RCA from waste concrete without induced damage. The properties of concrete decrease as RCA incorporates, and decrease following the growth of undergoing temperature on the fire-damaged concrete and its RCA. The compressive strength of concrete including 100% RCA from 300 to 800 °C fire-damaged concrete is 11.4–41.4% lower than that of concrete with 100% ordinary RCA, and the transport properties of concrete including fire-damaged RCA are higher than those of concrete with ordinary RCA. There is no obvious difference in the mineral composition of RCP made from 20 to 600 °C fire-damaged concrete, but new active components appear in RCP made from 800 °C fire-damaged concrete. The activity indexes of ordinary RCP and the RCP from 800 °C fire-damaged concrete are 72.6% and 90.4%. The properties of concrete decrease as RCP incorporates, while the properties of concrete incorporating RCP from fire-damaged concrete are better than those of concrete incorporating ordinary RCP. The compressive strength and absorption coefficient of concrete including 30% RCP from 800 °C fire-damaged concrete are 20.9% higher and 24.9% lower relative to concrete with 30% ordinary RCP.