Impact of fly ash on slag-based engineered geopolymer composites: Multiple-scale investigations
Yiming Zhou, Mohamed Elchalakani, Mohamed Ali Sadakkathulla, Reza Hassanli, Xiao Guo, Essam A. Tawfik, Osama Youssf
Abstract
This study investigates the impact of varying fly ash dosages on slag-based engineered geopolymer composites (EGC). The single-fibre pull-out, single-crack tensile, and dog-bone specimen tensile tests were carried out for the multiple-scale investigations. Results indicate that increasing the fly ash dosage from 20 % to 40 % enhanced the tensile strength, compressive strength, flexural strength, and tensile strain capacities by 150 %, 32 %, 34 %, and 319 %, respectively. The maximum bridging stress increased from 1.5 MPa to 3.72 MPa as the fly ash content raised from 20 % to 40 %, resulting in a 12.6 % tensile strain capacity in EGC. However, the mechanical performance of EGC started to deteriorate when using 50 % of fly ash. This study revealed that different geopolymer products exhibited varying interfacial properties with polyethylene fibre. According to the SEM-EDS and XRD results, low-calcium phase in geopolymer matrix provide a larger real contact area compared to high-calcium phases. Additionally, chemical bonding existed as the EGC transformed from being slag-based to fly ash-based. The impact of fly ash on slag-based EGC is significant, as it changes the interfacial properties of fibre and matrix by changing the chemical and physical properties of matrix.