Compressive strength of high strength class C fly ash-based geopolymers with reactive granulated blast furnace slag aggregates designed by Taguchi method

Compressive strength of geopolymeric specimens produced by class C fly ash and granulated blast furnace slag aggregates has been studied. Four different independent factors comprising of aggregate content, sodium hydroxide concentration, curing time and curing temperature were considered as the variables. To attain the maximum possible accurate responses by means of the smallest amount of examinations, Taguchi design of experiment method was followed. By taking into account 3 levels for each factor, 9 series of experiments were conducted on the specimens at 2 and 7 days of water curing regime. For the both considered regimes, the specimen with 30 percent weight of aggregate and sodium hydroxide concentration of 12 M which was cured at 90 oC for 16 h had the highest compressive strength. On account of the reactivity between the aggregates and the utilized fly ash, the compressive strength was reached to 69.3±5.3 MPa and 76.2±3.6 MPa at 2 and 7 days of water curing, respectively. The fracture surface of specimens with highest and the lowest strengths as well as the effect of each considered factor on the compressive strength of the specimens were studied