Reuse of hydrated mortar as partial replacement material in cement

Abstract

In this study, the reuse of hydrated mortars obtained from concrete waste materials as an additive to replace part of the Portland cement content in different ratios by weight was investigated. The properties examined included setting time, compressive strength, flexural strength, alkali–silica reaction, apparent porosity, water absorption, ultrasonic pulse velocity and dynamic modulus of elasticity. The results showed that the compressive strength of all specimens containing hydrated mortar waste (HMW) material was lower than that of the control specimens. However, the values obtained by replacement of 10–20% of Portland cement with HMW were within acceptable limits. The HMW with replacement ratio of more than ∼40% could not be used to replace ordinary Portland cement because the 28 day compressive strength was 29% lower when ∼40% cement was replaced by HMW. Moreover, the expansion of mortars due to alkali–silica reaction was significantly reduced when more than 20% of cement was replaced by HMW. Increasing the replacement ratio of cement gave rise to a longer setting time. When all the experimental results were taken into consideration, it was concluded that ground HMW can be used as a cementitious material to partially replace Portland cement.