Experimental Investigation on Compressive Strength Enhancement of Geopolymer Paste Fly Ash/ Slag Based Cured at Ambient Condition

Abstract

In this paper, the effects of ground granulated blast furnace slag (GGBFS) content proportion on the development of compressive strength of geopolymer pastes were studied. Eleven geopolymer pastes mixes replacement (0% to 100%) by increment (10%) of binder(Fly Ash) by GGBFS with three mini-size specimens (50-mm cube) compression tests were conducted at ambient condition (30 ± 2 °C). Class F-fly ash (FA) and GGBFS were used as aluminosilicate source. The alkaline activator was a combine of sodium silicate (SS) solution and sodium hydroxide (SH) solution with (SS/SH) ratio of (2.0) and molarity of sodium hydroxide of (10M). Based on the test results, it was find that the addition of ground granulated blast furnace slag (GGBFS) to geopolymer paste based fly ash caused increase significantly of compressive strength when cured at ambient condition, and the optimum mix was found to have GGBFS content of 100%, can be improved the compressive strength as high as (74% and 62%) at 7 and 28 days respectively. The reason for this trend is that the increasing forming of calcium silicate hydrate C-S-H gel of geopolymer pastes containing a large amount of GGBFS caused more denser microstructure. Lastly, it is worth noting that this test methodology used in this study is for the purpose of determining the best ratio of slag replacement with fly ash in geopolymer paste, to give the highest improvement ratio in compressive strength compared with the reference (Fly Ash based geopolymer paste).