Effects of alkaline solution/binder ratio on fracture properties of heat-cured lightweight fly ash C class-based geopolymer concrete

Concrete is the most diverse and widely used building material . The production of Portland cement is associated with the production of a large amount of carbon dioxide, which causes air pollution. It is inevitable to find an alternative material for Portland cement. Removal of cement is one of the greatest advantages of using geopolymer concrete. In this article, the results of tests on the fracture parameters of lightweight fly ash C class-based Geopolymer concrete (LWFCGC) as a material that has both advantages of lightness and use of green cement, are presented. These tests include three-point bending test on 49 beams with different activator to binder ratios. Also, compressive strength and tensile strength tests were performed on hardened concrete after 24 hours of processing at 80oC. In these experiments, three mix designs with 0.4, 0.5 and 0.6 activator to binder ratios were considered. By changing the activator to binder ratio from 0.6 to 0.4, compressive strength increased from 18.9 MPa to 28.4 MPa, fracture toughness improved from 19.65 MPa mm0.5 to 23.29 MPa mm0.5, total fracture energy (GF) increased from 59.20 N/m to 65.99 N/m, and the GF/Gf ratio decreased from 3.42 to 3.15.