For the complete replacement of Ordinary Portland Cement (OPC), the new technology of Geo-Polymer concrete (GPC) is a promising technique. An attempt is been made to study the optimum usage of Ground Granulated Blast Furnace Slag (GGBS) in concrete.An experimental study was conducted to obtain maximum strength by increasing the content of GGBS in concrete. GGBS based geo polymer concrete develops a flexural strength of 0.56MPa for 8M, 0.67MPa for 10M and 0.79MPa for 12M after 28 days of direct sunlight curing..The results showed the increase of compressive strength to a maximum by the inclusion of GGBS. After this optimum value, it was observed that the strength decreased. The optimum level of GGBS content was fixed to about 55-59% of the total binder content. In this study the geopolymer concrete is prepared by carrying out the usual concrete technology methods. Aggregates occupy the major volume, i.e. about 75-80% by mass in the normal concrete. In geopolymer concrete 78% of volume is occupied by aggregates. It was observed that with increase in molarity of NaOH, compressive strength of GGBS based geopolymer concrete increases. It is due to increase in alkalinity of mix, which increases the rate of geo-polymerization. It can also be observed that compressive strength increases with the age of concrete specimens. This is an attempt using only NaOH whereas Potassium hydroxide can also be taken in combination with NaOH to increase the strength. Sodium hydroxide is available in plenty and Potassium hydroxide is more alkaline than NaOH.
