In the recent past, the importance of geopolymer concrete as an eco-friendly product to replace portland cement concrete is continuously increasing over time. Yet less research effort has been invested in this area compared with some topical issues in civil engineering. Thus, the objective of this article is to analyse the mechanical properties of geopolymer concrete where the cement is replaced by fly ash and ground granulated blast-furnace slag (GGBS). Sodium silicate and sodium hydroxide 8

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... larity solution was used. The compressive strength of a cube in an 8 molarity solution was measured for various mixtures (i.e. G50F50 where G and F stand for GGBS and flyash, respectively while the numerical value denotes the cement percentage) and the cement contents (i.e. 0, 10, 20, 30, 40%). The cube specimens are 100mmx100mmx100mm with the ambient curing at 35- 400C. In total, 9 cubes, 3 beams and 3 cylinders are cast at 7days, 14days and 28days while the compressive strengths of different mixes and cubes are calculated. For 28days, beams and cylinders are measured for flexural and tensile strength. The compressive strength at 7,14 and 28 days nearly doubled the target strength by using geopolymer concrete instead of normal concrete. Compressive strength is about 10% higher at 7 and 14days and 20% higher at 28days after replacing 40% of the cement. Flexural strength increased by 50% when 40% of the cement was replaced but split tensile strength only increased by 1%.