Effect of curing regimes, fly ash/slag ratios and steelfibers on mechanical properties of geopolymer concrete

Ordinary Portland cement (OPC) production results in a havoc to the environment due to CO2 emission, so it is needed to find an alternative material. The properties of fly ash (FA)-based geopolymer concrete (GPC) was extensively studied in recent years. In this study, as a first step FA-based, GPC was prepared, and activated by a mix of sodium hydroxide (NaOH) and sodium silicate (Na2Sio3) solutions. Ground granulated blast furnace slag (GGBFS) was added as (0, 25, and 50) % of the total binder. Samples were cured under furnace 60 ⁰C, 80 ⁰C, and ambient state. In the second study, the effect of steel fiber on GPC was investigated. For this purpose, specimens of GPC without and with steel fiber (0.5, 1, and 1.5 %) were produced. Constant Na2Sio3/NaOH and alkaline activator to binder ratios of 2.5 and 0.5, respectively, were adopted. Experiments were made via slump, compressive strength, splitting tensile strength, flexural strength testes to detect the influence of steel fiber, GGBFS, and different curing regimes on FA-based GPC, tested at different curing dates 7, 28 and, 56 days. Test results showed that the addition of steel fiber and GGBFS affected the fresh properties negatively and notably developed bond strength and flexural performance. The effect of GGBFS was detected to be dominant on compressive strength and workability. The highest compressive strength was detected for steel fiber reinforced GPC (SFRGPC) cured at temperature 80 ⁰C for 24 hr.