Mechanical and microstructural properties of sustainable ternary blended alkali-activated concrete

Abstract

In recent years, there has been a surge in interest surrounding alkali activated concrete (AAC), a novel type of concrete praised for its environmental and construction applications. This study focuses on ternary blended alkali-activated concrete (TBAAC) using fly ash, ground granulated blast furnace slag (GGBS), and silica fume as binders. It also aims the replacement of sodium silicate (SS) solution with neutral grade sodium silicate (NGSS) solution with a silica modulus (SiO₂/Na₂O) of 3.12 to improve the fresh and hardened properties of TBAAC. In this context, the effects of silica fume and alkaline activators are studied to determine the optimum mix design and to evaluate the fresh and hardened properties of TBAAC cured under ambient conditions. To investigate the performance of TBAAC, various experiments were carried out to measure its workability, compressive strength, splitting tensile strength, flexural strength, regression analysis and microstructural characteristics. The results show TBAAC of 40 % fly ash, 50 % GGBS and 10 % silica fume resulted in higher mechanical properties, including compressive strength (74.12 MPa), splitting tensile strength (18.46 MPa), and flexural strength (20.45 MPa). The results of the XRD, SEM and EDX analysis show the formation of C-A-S-H, C-S-H, and N-A-S-H gel, indicating a densified matrix with fewer cracks and pore spaces. Furthermore, the Life Cycle Assessment (LCA) results demonstrate that the use of NGSS, with its improved environmental profile, leads to a lower environmental impact, contributing to a significant reduction in the carbon footprint of TBAAC and enhancing the sustainability of construction materials. The findings suggest that using NGSS-based TBAAC is advisable for construction applications, offering practical implications for reducing environmental impact while maintaining high performance in construction projects.