Concrete was mixed in the laboratory to cast the test specimens. General purpose Portland cement was used for OPC concrete. Commercially available Class F (ASTM: C618) fly ash was used to manufacture geopolymer concrete. The percentage
of the fly ash passing through a 45 lm sieve was 75%. The chemical
compositions of the cement and fly ash are given in Table 1. The alkaline liquids for geopolymer concrete were sodium hydroxide and sodium silicate solutions. Commercial sodium hydroxide pellets were dissolved in water to make 14 M solution. The sodium silicate solution had a mass composition of 14.7% Na2O, 29.4% SiO2, and 55.9% water. Both the liquids were mixed together before adding to fly ash and aggregates. The coarse aggregates were 10 and 20 mm nominal size crushed granites. The sand used was riversand. Tap water was used in mixing of the concretes. The mixture proportions of the OPC and geopolymer concretes are given in Table 2. The concretes were mixed in a pan type laboratory con- crete mixer. Standard slump tests were carried out to determine the workability of fresh concrete. The slump value of OPC concrete was 100 mm and that of geopolymer concrete was 250 mm. Both the concretes had reasonable workability at these values of slump.