THE EFFECT OF STEAM CURING METHOD TO THE COMPRESSIVE STRENGTH OF GEOPOLYMER CONCRETE WITH DIFFERENT MOLARITY

Cement, an important part of concrete mixture, determine the mechanical properties of concrete. The mixture of cement and water will stimulate the hydration reaction which will produce CSH gel and heat of hydration. The high level of CO2 pollution produced in the cement manufacturing process requires alternative efforts to replace cement with other pozzolanic materials. One of the materials that can replace the role of cement in concrete mixture is fly ash. The replacement of cement 100% with fly ash will produce a geopolymer concrete, which requires an alkaline solution as a reagent from fly ash. This research was conducted with the aim to explore the effect of steam curing to the compressive strength of geopolymer concrete with different molarities. As the test object in this study was a geopolymer concrete cylinder with a standard size i.e. 150 mm × 300 mm. The molarity of NaOH solution varying from 6, 8, 10, 12, 14 to 16 M. The temperature of steam curing was carried out varied from 60oC, 80oC, up to 90oC, with duration from 1 until 4 hours. The compressive strength test conducted for 28 days old of concrete cylinder specimens. The results show an indication of an increase in the compressive strength of the concrete along with the increase in the molarity of the NaOH solution. In addition, it can also be shown that the steam curing process at a temperature of 60oC with 4 hours in duration shows optimal compressive strength results.