Effect of Pretreated Corn Cob Ash on the Mechanical and Durability Characteristics of High-Strength Concrete

Portland cement, a key binder for concrete, is a significant contributor to non-renewable resource consumption and greenhouse gas emissions. To address these issues, it is often replaced with materials from industrial and agricultural waste. Corn cobs are such agricultural waste. The reactive silica and alumina in corn cob ash can react with free lime in Portland cement, enhancing its strength and durability. However, research has shown that the chemical composition of corn cob ash varies significantly due to agricultural practices. Potassium-rich fertilizers, which promote corn growth, produce corn cob ash with high potassium and phosphorous oxides, which negatively affect concrete strength and durability. The objective of this research was to develop a suitable method for pretreating corn cob to reduce its potassium oxide and phosphorous oxide content and, at the same time, increase the pozzolanicity of the ash. The ash from pretreated corn cob was used to partially replace Portland cement in concrete production, and 28-day strength in excess of 40 MPa was produced, which increased to more than 70 MPa at 90 days. Moreover, the concrete had reduced water absorption, which was an indicator of improved pore density and improved resistance to sulfuric acid attack.