Utilization of Corn Cobs Ash as Cementitious and Binary Cementitious Materials in Concrete and Cement-based Composites: A Review

Abstract

This paper reviews the utilization of corn cobs ash (CCA) as pozzolanic, cementitious, and binary cementitious materials in concrete. CCA is the grey-to-brown, inorganic or heterogeneous residual material derived from the high- temperature incineration or combustion of corn cobs (CC). Despite the typical problematic nature of biomass ash, the chemical composition of CCA renders it a potential pozzolanic material. Therefore, numerous studies have critically examined the process technologies and operational conditions for CCA production and its application as a partial replacement for cement in concrete. Other studies have extensively characterized the physicochemical, morphological, microstructure, and thermal properties of CCA through various analytical techniques. Potential pozzolanic materials must meet the condition: SiO2 + Al2O3 + Fe2O3 ≥ 70%, according to ASTM C618, to which CCA complies satisfactorily. Hence, the use of CCA as a replacement for cement has been investigated over the years. Findings indicate that the partial replacement of cement with CCA decreases compressive strength, thermal conductivity, ultrasonic pulse velocity, and density of the hardened concrete at normal temperatures. Nevertheless, the thermal treatment (calcination) of CCA and extended curing enhances compressive strength owing to higher silica content and extended surface area. Besides, the partial replacement of cement with CCA enhances the insulation properties of mortar, which improves thermal comfort, costs and energy savings in buildings. Hence, the partial replacement of cement with CCA provides an environmentally friendly, low cost, and sustainable approach for valorizing CC residues whilst addressing CO2 emissions in construction.