Last modified: 2018-07-07
Abstract
One of the issues in geopolymer specimen production is the requirement for heat curing temperature to achieve its structural integrity during the curing process. It generally occurs in low calcium fly ash-based geopolymers. The use of a material with high calcium content, such as limestone, is one alternative to overcome this problem. However, the addition of high calcium content alters the basic geopolymer reactions being similar to the basic reactions in normal concrete. Geopolymerization process do not require a water treatment, while normal concrete is necessary to be cured in water during curing process. Thus, it is necessary to perform research related to the curing models of fly ash-based geopolymer incorporating limestone.
This research aims to investigate the effect of different curing models to the strength development of high calcium fly ash geopolymer specimens with limestone inclusion. High calcium class C fly ash was used as primary material. The blended sodium silicate and 10 Molar sodium hydroxide were used as alkaline activator. The variation of fly ash to ratio was 1:0, 0.9:0.1, 0.8:0.2, 0.7:0.3, 0.6:0.4, and 0.5:0.5, respectively. Three different curing models were applied for this research, i.e. water immersion 24 hours, watered once, and watered twice in a day, respectively. The compressive strength was performed at the age of 7, 14, and 28 days in accordance with ASTM standard.
The results show that the highest compressive strength was achieved by geopolymer specimens under watered once curing models. The addition of limestone also improved the strength of geopolymer under watered once curing models. The inclusion of 30% limestone under water once curing models gives the best result with the strength of 32.5 MPa. It demonstrates that geopolymer specimens do not require a high amount of water during geopoymerization process as occurs in normal concrete. This results confirm the previous results on the role of water in geopolymer specimens.