An experimental investigation on properties of geopolymer concrete (no cement concrete)

One of the efforts to produce more environmentally friendly concrete is to reduce the use of OPC by replacing the cement in concrete with geopolymers. In geopolymer concrete no cement is used, instead fly ash and alkaline solutions such as sodium hydroxide (Na OH) and sodium silicate (Na2O, SiO2) and potassium hydroxide (KOH) are used to make the binder necessary to manufacture the concrete. One tone of fly ash can be utilized for manufacturing about 2.5 cubic meter of high quality Geopolymer concrete. Test experiments proved as fly ash based Geopolymer concrete has excellent Compressive strength, suffers very low drying shrinkage, low creep, excellent resistant to sulphate attack and good acid resistance. Trial mixes were done and noted the properties of the concrete both in fresh state and in hardened conditions. The workability of the concrete in terms of slump and compacting factor are observed to be excellent. The geopolymer concrete in fresh state observed to be highly viscous and good in workable. Collapsed slump was observed with compaction factor of 0.95. Cube compressive strength of the geopolymer concrete cubes verified at the age the concrete 28 days from the date of their casting. Based on the test results of the trial mixes, this experimental study is carried out for 5 different mix proportions of fly ash to alkaline chemical ratios of concrete specimen. Test specimen of standard sizes of cubes (30nos), cylinders (30nos), and prisms (15nos) were cast and tested for workability in terms of slump and compacting factors in fresh state and for mechanical properties such as Compressive Strength, Splitting Tensile Strength, Flexural Strength, and Modulus of Elasticity of concrete in hardened state. The test experiment proved that a concrete of compressive strength of 30MPa could be achieved in geopolymer concrete by adopting alkaline solution to fly ash ratio of 0.50 at 16 molarity of Na OH.