Utilizing wollastonite in concrete as a replacement of cement: impact of carbonation and pore structure evaluation using EIS

Concrete is an important construction material, but its production leads to increase in carbon emissions and energy usage. To address these concerns, experimental investigations are looking into using wollastonite as a partial substitute to cement in concrete. Wollastonite (CaSiO₃) is a calcium silicate mineral along with minor impurities such as iron, magnesium, and aluminium, these components contribute to wollastonite’s stability, low water solubility, and beneficial role in enhancing the hydration process when used in concrete which is intended to improve concrete characteristics and increase sustainability. The research challenge addressed in this study, is the limited research of wollastonite powder as a cement substitute in concrete, since the prior studies focussed exclusively on wollastonite microfibre. In the current study wollastonite powder is used as supplementary cementitious material replacing cement content partially by weight like 5%, 10%, 15%, 20%, and 25%, with 0.45 w/c ratio. The present study evaluated the physical and fresh properties on raw materials. Also physical, chemical, and mechanical characteristics on mortar and concrete as well as microstructural properties which revealed modified concrete has needle like structure. Subsequently the pore structure is evaluated by electrochemical impedance spectroscopy in which Nyquist and Bode’s plots indicated the impedance value of 519.2 kΩ. Depth of carbonation of mortar specimens measured as 10.5 mm at 28 days. Further the modified concrete mix exhibited better performance than conventional mix as the optimum mix was arrived at WM_20. Thus, heralding a new era of sustainable material for advancing civil engineering infrastructure.