Microstructural investigation of ternary blended high-performance concrete using supplementary cementitious materials

An experimental study was performed to understand the behaviour of cementitious material on the fresh and mechanical properties of ternary blended high-performance concrete (HPC). Ordinary Portland cement (OPC) was replaced by various proportions of micro silica (MS) and fly ash (FA) resulting in ternary concrete mixes forming additional cementitious compounds that contribute to the strength and durability of the concrete. Various phases present in the cementitious materials used in the mix were observed using X-ray diffractogram. On comparing to the HPC made only with OPC, utilization of 10% MS and up to 30% FA enhanced the mechanical properties and gave better durability performance. The collective use of 20% FA and 7.5% MS with OPC (Grade 43) can be called as optimum HPC mix. Using high proportions of FA, the mix obtained was cohesive with good flowability. Rapid chloride penetration of each mix was studied to explore the durability performance. For better understanding at microstructural level, field emission scanning electron microscopy (FESEM) was used to study the pores, voids and CSH gel formations. The images obtained from SEM were further analysed using the tools of MATLAB (R 2022a) software. Pore network characteristics of the digitized images were obtained using the code generated from the image processing toolbox of the MATLAB. Based on the results, all mixes were less porous than the control mix and showed a lower chloride penetration rate.