Engineering Properties of Fly Ash-Based Geopolymer Concrete with Various Alkaline Activator Solution Dosages

This paper presents an experimental study of fly ash-based geopolymer concrete with various alkaline activator solution dosages. The alkaline activator solution consisted of sodium silicate solution and sodium hydroxide solution with a concentration of 12M. The specimens were prepared with various alkaline activator solution / fly ash (AAS / FA) ratios of 0.3, 0.4, and 0.5. The sodium silicate solution to sodium hydroxide solution ratio was preselected at 2.5 by weight. The specimens were cured at 65°C in a dry oven for 24 hours and then continued curing at room temperature for 7, 14, and 28 days. Test results indicated that compressive and flexural strengths significantly increased with an AAS / FA ratio in a range of 0.3–0.5. At 28 days, the compressive and flexural strengths gained 33.30–41.1 MPa, and 3.41–5.61 MPa, respectively. Moreover, the strength significantly developed being cured in temperature conditions at early ages and then slowly increased at long-term ages. Then, based on the obtained data, this study used the ACI code to determine the compressive strength at t-day based on 28 days. Finally, correlations between flexural strength– compressive strength, compressive strength–ultrasonic pulse velocity, flexural strength–ultrasonic pulse velocity, and elastic modulus–ultrasonic pulse velocity were also obtained.