Effect of recycled powders on the mechanical properties and durability of fully recycled fiber-reinforced mortar

Abstract

Recycled powders from construction and demolition wastes are rarely applied due to their low additive value. This study used recycled concrete powder (RCP) and recycled brick powder (RBP) as fine particles to partly replace cement, which represents a novel application of recycled powder. Fully recycled fiber-reinforced mortar with recycled sand, recycled fiber and RCP/RBP with replacement ratios of 10%, 20% and 30% was prepared. The mechanical properties and durability, including compressive and flexural strength, dynamic elastic modulus, capillary water absorption, freeze-thaw resistance and carbonization were tested. In addition, XRD and TGA tests were carried out to reveal the mechanism of the RBP/RCP's influence on the properties of fully recycled fiber-reinforced mortar. The results show that there is a greater reduction in strength in mortars with RCP when the curing age is 3 d. When the replacement ratio is 30%, the compressive strengths of mortar with RCP/RBP reach 75.73% and 79.95% of that of cement mortar, respectively. With the addition of RCP/RBP, the capillary water absorption decreases and the carbonization depth increases. In addition, a clear increase in mass loss and decrease in dynamic elastic modulus after 50 freeze-thaw cycles are noted. The mortar with RBP has better performance than that with RCP. The XRD and TGA results show the low activity and secondary hydration of RCP/RBP.