Effect of integrating industrial and agricultural wastes on concrete performance with and without microbial activity

Cement is an essential material used in constructional activities. An emerging concern in the industry however is the CO₂ emissions, which are triggered by cement manufacturing units. These emissions can be controlled to some extent by not using cement exclusively and instead replacing a percentage of it with waste material with properties similar to cement. Electric arc furnace dust (EAFD) and rice straw ash (RSA) are waste materials from industrial and agricultural sources which also contain similar constituents that are present in cement. Thus, the objective of this study is to check the effect of EAFD and RSA on concrete properties with the application of Aspergillus niger and Bacillus megaterium. Taguchi's design of experiments has been utilised to explore the effect of operating parameters (i.e. EAFD and RSA replacement (5%, 10% and 15%), curing period of concrete cubes (7, 14 and 28 days) and cell count of fungus/bacteria (10⁴, 10⁶ and 10⁸ CFU/ml)) on the compressive strength and water absorption capacity of concrete blocks in three different scenarios. Optimisation has then been carried out by using the multi-objective genetic algorithm to evaluate the maximum performance of concrete. However, the results of the study indicate best performance in the 2nd context where dust replacement, curing time and cell count were 5%, 18 days and 9.39 × 10⁷ cells per ml of water, respectively, for concrete production utilising Aspergillus niger.