Effects of corn cob ash and rice husk ash usage in mortar productions

Abstract

The cement industry faces serious environmental challenges, with emissions like air pollutants and cement dust posing health risks to nearby communities and contributing to global issues such as climate change. As environmental awareness about possible adverse effects has significantly expanded, using agricultural and industrial waste by-products has become an increasingly desirable option for waste disposal. This study focused on enhancing the environmental friendliness of concrete mixtures by using and evaluating the performance of mortars incorporating corn cob ash (CCA) and rice husk ash (RHA) as part of Ordinary Portland Cement (OPC) to create more sustainable cement mortar composites. The experimental methodology in this study involves three phases aimed at exploring the potential of corn cob ash (CCA) and rice husk ash (RHA) as a Supplementary Cementitious Material (SCM) in improving the environmental sustainability and performance of mortar. Phase 1 focuses on evaluating the pozzolanic activity index of both corn cob ash (CCA) and rice husk ash (RHA). The Pozzolanic Activity Index (PAI) is a measure used in cementitious materials to assess the reactivity of pozzolanic materials, a high PAI indicates a higher reactivity of the pozzolanic material, meaning it can contribute more effectively to the strength and durability. The optimal burning temperature for corn cob ash (CCA) was also identified in this phase by burning corn cobs at temperatures from 400°C to 700°C. Phase 2 focuses on identifying the optimal mix ratio between corn cob ash (CCA) and rice husk ash (RHA) that offers the best balance between pozzolanic activity and mechanical properties. In Phase 3, the main objective is to determine the optimum percentage replacement of cement with corn cob ash (CCA) and rice husk ash (RHA) mixtures. based on the findings from the previous phases, different percentages of cement replacement (5%, 10%, 15%, and 20%) are investigated. An X-ray fluorescence test (XRF) was used to determine the chemical composition of the cement, rice husk ash (RHA), and corn cob ash (CCA) used in the production. Various tests were carried out to determine the impact of CCA-RHA combinations on mortar characteristics. During the production phase, the workability of mortars incorporating corn cob ash (CCA) and rice husk ash (RHA) was evaluated through a flowability test. Additionally, the air content of mortars with varying proportions of corn cob ash (CCA) and rice husk ash (RHA) was calculated. To measure the expansion of each mortar, an accelerated mortar bar test was performed with varying replacement percentages. Furthermore, flexural and compressive strength tests were conducted at 7 and 28 days. X-ray diffraction analysis, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) tests were performed to examine the pozzolanic reaction in order to investigate the effect of corn cob ash (CCA) and rice husk ash (RHA) on calcium hydroxide (CH) consumption, calcium silicate hydrate (C-S-H) formation, and quartz formation with an increasing cement replacement percentage. The study's deep investigation reveals that rice husk ash (RHA) and corn cob ash (CCA) hold promise as effective supplementary materials for enhancing the mechanical and microstructure properties of mortar paste. Optimal calcination temperatures and mix ratios were identified, with a 5% cement replacement showing the most favorable mortar performance. X-ray diffraction (XRD) analysis indicates enhanced cementitious properties and pozzolanic activity with increasing replacement percentages, supported by thermogravimetric analysis (TGA) showing a decline in calcium hydroxide (CH) content. Scanning electron microscopy (SEM) images depict microstructural changes indicative of improved mechanical properties and stability with higher replacement percentages. Rice husk ash (RHA), and corn cob ash (CCA) are therefore regarded as an effective cement replacement material.