A COMPARATIVE STUDY ON THE PROPERTIES OF CONCRETE PRODUCED BY USING TREATED AND UNTREATED DEMOLISHED CONCRETE WASTE POWDER AS A PARTIAL REPLACEMENT OF CEMENT

Abstract

Several researchers are doing experimental investigations to identify potential eco-friendly and cost-efficient cement substitute materials. Some of these materials are generated from industrial waste and agricultural waste. Very limited studies have been conducted on the utilization of construction and demolition waste as a cement substitute. Using construction and demolition waste as a potential source of raw material in the production of cement-based materials conserves the environment by reducing the exploitation of natural resources. Also, using such wastes as an alternative material for cement benefits energy conservation and reduces the release of carbon dioxide into the environment. Accordingly, this study aimed to investigate the use of powdered concrete waste generated from demolished structures in place of cement to produce C-25 concrete. The designed cement replacement dosages could be 0%, 10%, 20%, and 30%. The powder that was used for this investigation was grounded and processed as specified in ACI 555. The two types of powder that were used were untreated powder (grounded and sieved) and thermally treated powder (grounded, sieved, and treated at a temperature of 800 °C). To understand the effect of untreated and treated demolished concrete waste powder on the fresh and hardened properties of C-25 concrete, a substantial number of standard specimens were cast, cured, and conducted at the curing ages of 7, 28, and 56. The study's findings indicate that concrete's compressive strength increases when UDWCP is used in place of cement up to a 10% replacement rate; beyond that, there is a negligible reduction in compressive strength. However, the compressive strength of concrete increases when 20% of the cement is replaced with TDWCP; after that, there is a negligible fall in compressive strength. The thermal treatment Process transforms the hydrated DCWP into dehydrated DCWP, which is composed of the phases involved in strength development, primarily the calcium silicates and more mass loss. Strength development and partial hydration ability recovery are possible outcomes of this heat treatment. The crystalline phases of the hydrated DCWP processed at 800 °C and the OPC show many similarities.