Eco-friendly utilization of corncob ash as partial replacement of sand in concrete

Abstract

The natural sand reservoirs are depleting globally due to nonstop consumption of aggregate in concrete. The detrimental effect of uncontrolled fine aggregate extraction from riverbeds is also a major concern. Moreover, the proper disposal of agricultural waste resulting from biomass burning is a major environmental challenge. Hence, in this research, we have proposed an eco-friendly solution by investigating the utilization of corncob ash with 0, 5, 10, 15 and 20% as fine aggregate in concrete. CCA was characterized to determine its suitability as fine aggregate by determining physical and chemical properties as well as investigating its morphology at micro and macro level. Thereafter, in fresh state, the CCA concrete was tested for slump, shrinkage and density while in hardened state; it was tested for compressive strength, water absorption, ultrasonic pulse velocity, and density at the age of 7, 28, 56, and 90 days. The thermal gravimetric analysis was also performed to evaluate the possible pozzolanic potential of CCA composite. Test results showed that CCA was well graded, amorphous, free from organic impurities, and having highly porous morphology due to the presence of micro pores, perforations, and tubules. The slump and shrinkage values increased while the fresh concrete density decreased with the increase in the percentage of CCA. The compressive strength, ultrasonic pulse velocity, and hardened concrete density decreased with the increase in the percentage of CCA while the values of these parameters increased with the age of testing. The values of water absorption were found to decrease with the age of testing. At 28 days, the compressive strength of concrete with 10% CCA as replacement of fine aggregate was found to be 22 MPa. For all mixes, the weight loss in sulfuric acid was more pronounced than hydrochloric acid due to more aggressive and destructive nature of sulfuric acid. Chemical composition of CCA and TGA results of CCA composite showed that CCA has pozzolanic potential when used in concrete as partial replacement of fine aggregate. The utilization of CCA provides eco-friendly solution of ash disposal problem. It also provides viable source of raw materials for construction industry and hence would help in conserving natural aggregate resources. Hence, the benefits of using CCA as fine aggregate in concrete were verified.