Mechanical properties of sustainable engineered geopolymer composites with sodium carbonate activators

Abstract

Engineered geopolymer composites (EGC) have emerged as promising alternatives to engineered cementitious composites (ECC), largely owing to their low carbon emission potential. However, typical alkaline activators used in geopolymer often contribute to significant environmental impact. Sodium carbonate (SC), also known as natural alkali, is derived from abundant natural deposits and offers a potential greener alternative, with lower carbon emissions, and reduced energy consumption. This study introduces a novel hybrid activation approach using SC as a partial replacement for sodium hydroxide (SH), aiming to improve both the mechanical performance and sustainability of sodium carbonate-based engineered geopolymer composites (SC-EGCs). A series of experiments were conducted to investigate the effects of SC replacement ratio (0 %, 25 %, 50 %, and 75 %) and curing age (3 days, 28 days, and long-term) on the macroscopic property, mechanism explanation, and sustainability. The results show that SC-EGCs achieve excellent mechanical performance, with compressive strength exceeding 125 MPa, ultimate tensile stress surpassing 10 MPa, and ultimate tensile strain reaching 9 %. These remarkable properties are attributed to the synergistic effects of alkaline activators. Strength development primarily occurs at early curing ages, with marginal improvements observed in long-term curing. Computer-aided crack analysis reveals that incorporating SC enhances crack distribution, improving tensile behavior of the composites. Furthermore, increasing the SC replacement ratio significantly enhances sustainability and economic benefits, reducing the embodied carbon per Strength-Ductility Index by up to 36 % compared to EGC without SC replacement. These findings open new avenues for the utilization of sustainable geopolymer in building engineering.