Strength and durability characteristics of pumice based geopolymer paste

Cement consumption causes several environmental issues due to using a massive amount of energy and releasing gas emissions. Geopolymerization, a new technological process, provides an innovative way to produce concrete without cement usage. In this study, pumice powder, which is rich in silica and aluminum such as fly ash and metakaolin, is utilized as a binder to produce geopolymer paste. The influences of fineness of pumice, different sodium hydroxide concentration, curing temperature and curing period on the strength and freezing and thawing durability characteristics. The mass ratio of sodium silicate solution to sodium hydroxide and alkali binder ratio was fixed to 2.50 and 0.35 respectively. The geopolymer paste specimens were placed at ambient temperature for 24 hours as a rest period with different concentration (8, 10, 12, 14, 16 and 18M) of sodium hydroxide and then cured at room temperature, 60, 80 and 100 oC temperature for 24, 48, 72 and 120 hours. The compressive strengths of geopolymer pastes were tested at the ages of 7 and 28 days. Flexural strength tests were conducted at age of 28 days. The SEM analyses were performed to identify the morphology characteristics and to determine the unreacted particles of the geopolymer pastes. The results showed that optimum flexural and compressive strength can be obtained at 60 oC of oven curing for 120h with 12M. Although, high strengths can be obtained at high curing temperatures with less curing time, but when compared to low temperature and more curing time, flexural and compressive strength gains are less.