Durability of Fly Ash–Based Geopolymer Structural Concrete in the Marine Environment

The use of supplementary cementitious materials as partial replacements of the cement in concrete will play a significant role with respect to the environmental control of greenhouse effects and global temperature reduction. The development of geopolymer concrete (GPC), in which all of the portland cement is replaced with fly ash (in combination with sodium hydroxide and sodium silicate solutions), offers a promising alternative to ordinary portland cement concrete. This paper evaluates the durability characteristics of low-calcium fly ash–based geopolymer concrete that was subjected to a corrosive marine environment. A series of GPC beams, which contained fly ash with 8- and 14-M concentrations of NaOH and ${\mathrm{SiO}}_2/{\mathrm{Na}}_2\mathrm{O}$ solutions, respectively, and were centrally reinforced with a 13-mm rebar, were tested for accelerated corrosion exposure with wet and dry cycling in artificial seawater and an induced current. A sudden rise in the current intensity that is attributable to specimen cracking was indicative of durability. The test results indicated excellent resistance of the geopolymer concrete to chloride attack, with a longer time to corrosion cracking relative to ordinary portland cement concrete.