Enhanced strength reduced modulus high calcium FA geopolymer concrete containing recycled aggregate concrete and Portland cement

In this paper, a reduced modulus high-calcium fly ash geopolymer concrete was developed as a sustainable and environmentally efficient construction material for road pavement. The recycled concrete aggregate (RCA) was used to replace natural coarse aggregate (NA) in making geopolymer concrete. The waste glass fiber reinforced plastic (GFRP) of 2.36–4.75 mm was then added at dosages of 0–2.0 % of fly ash by weight. In the final step, ordinary Portland cement (OPC) was used to replace 0–15 %fly ash to produce a low elastic modulus RCA geopolymer concrete containing GPRF and OPC. Test results showed that the RCA high calcium fly ash geopolymer concrete with 1.5 %GFRP and 15 % OPC gave low elastic modulus of 16.96 GPa with high compressive strength of 41.2 MPa and flexural strength of 3.17 MPa. The RCA was incorporated for its low rigidity, GFPR for its low rigidity and contribution to strength particularly in flexure, and OPC for setting and strength development with curing at ambient temperature. The developed low elastic modulus was 56 % of that of normal OPC concrete of the same compressive strength calculated from ACI318 of 30.18 GPa.