State of Art Reviews on Physico-chemical Properties of Waste Concrete Aggregate from Construction and Demolition Waste

Abstract

Numbers of waste concrete have generated from construction and demolition waste (CDW) threaten environmental and human health due to the illegal dumping practices in several countries. Recently, the recycling of waste concrete has demonstrated the ability to reduce dependency on a natural resource in producing building materials as well as reducing carbon footprint in the concrete manufacturing process. The objective is to determine the limitation factors of Waste Concrete Aggregate (WCA) as a replacement for virgin concrete aggregate. Analysis by X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF), leaching, and sulphate tests were used to identify the physicochemical characteristics of WGA. Results showed WCA has high water absorption, expansion of Alkali-Silicate Reaction (ASR), low adhesive strength between aggregate and cement, leachability, and high soluble sulphate. CaO, Al2O3, SiO2, SO42-, Cr2O3, SrO, and Al2O3 were the main chemical components consisting of WCA. The leachability of Ca, Zn, and Cr in WCA was pH-dependent. High soluble sulphate content in WCA determined the extension formation of micro-crack in WCA due to extensively recrystallizing the Delay Ettringite Formation (DEF) in WCA. The formation of micro-crack, ASR, and low adhesive strength between aggregate and cement insides of WCA significantly affect the durability of recycled products in building structures. High water absorption and leachability of WCA enhanced the release of heavy metals in soil. Therefore, these limiting factors in WCA were necessarily treated before being utilized as a part of the recycled product.

Keywords

• alkali-silicate reaction
• construction demolition waste
• delay ettringite formation
• waste concrete aggregate