Effect of silica fume on the mechanical properties of fly ash based-geopolymer concrete

In this paper fly ash based geopolymer concretes with different percentages of silica fume were made by using NaOH/sodium silicate and cured in an oven at 100 °C. Workability, compressive strength, flexural and tensile strengths were determined. Portland cement concrete was used as a reference. Sodium hydroxide (14 M) and sodium silicate were used as alkali activators. The results have shown that addition of silica fume improved the compressive strength of the produced geopolymer concretes. Tensile and flexural strengths also increased as the silica fume content increased. The geopolymer concretes were found quite durable in the presence of 2% H2SO4, 5% Na2SO4 and 5% NaCl.