Developing a sustainable concrete incorporating bentonite clay and silica fume: Mechanical and durability performance

Abstract

The use of supplementary cementitious materials (SCMs) can improve the properties of concrete, reduce pressure on natural resources and CO2 emissions. However, certain SCMs are unable to meet the growing demand of construction sector. The presented study investigates the role of bentonite clay (BC) and its synergistic effect with silica fume (SF) as partial replacement of cement on strength, durability, and microstructure of concrete. Five different mixtures were prepared containing 0%, 7.5%, 15% and 22.5% (by weight) of BC as a replacement of cement whereas SF was kept constant at 10% replacement level. The experimental results showed that the addition of SF had a positive impact on compressive strength with increase in curing time i.e., a maximum value of 43.09 MPa was achieved. The bentonite based concrete requires excess curing to achieve high strength. The ultrasonic pulse velocity of all tested specimen lies in the range of "good" quality concrete i.e., > 3.5 km/s. Durability testing depicted that the BC and SF significantly improved the pore structures and resistance against sulfate attack and chloride ingress. The proposed empirical formulations (using machine learning technique i.e., gene expression programming) were found accurate (correlation>0.9) and can be utilized for prediction of properties of concrete. The environmental impact analysis revealed that utilization of BC and SF can reduce the carbon emission by approximately 23% compared to control mix. It is recommended to conduct leachate analysis for each mixture prior to use. The proposed concrete mixtures were deemed technically, environmentally, and economically viable for application in construction sector.