CHARACTERISTICS OF FLY ASH-BASED GEOPOLYMER MORTAR WITH VARIATION OF TYPES AND DOSAGES OF ADMIXTURE AND CURING SYSTEMS

Abstract

Geopolymer concrete is the concrete of the future because, in its manufacture, it does not cause environmental problems; instead, it can prevent air pollution and environmental pollution. Geopolymer concrete has several advantages: suitable mechanical properties, high early strength, stable heat, and fire resistance. In the mixture, fly ash, a silicate and aluminum source, is reacted with an alkaline solution as an activator to make a polymerization reaction. To carry out the polymerization reaction, it is necessary to use Sodium Hydroxide or NaOH, which has strong basic properties as an alkaline reactant, and sodium silicate or Na₂SiO₃ as a catalyst.

This study aims to determine the effect of using admixture on the compressive strength of 50x50x50 mm geopolymer mortar cubes. This study's ratio of the alkaline solution was 1/1, while the balance between fly ash/solution was 60/40. Planning a mixture of mortar composition, namely fine aggregate/paste of 65/35. The admixture used is Sikament LN and Sika Viscocrete 1050 HE with a curing system that is humid temperature and at room temperature. Sikament LN content is 0,3%, 1%, 1,5%, and 2% by weight of fly ash, while the Sika Viscocrete 1050 HE content is 0,8%, 1%, 1,5% and 2% by weight of fly ash. Mortar compressive strength test was carried out at 7 days, 14 days, and 28 days.

In this study, the optimum grade for each use of admixture in geopolymer mortar was Sikament LN 0,3% and Sika Viscocrete 1050 HE 0,8% at humid temperature curing, which produced the highest compressive strength of 37,65 MPa and 21,26 MPa at 28 days of age. Increasing the percentage level of the amount of admixture used decreases the results of the mortar compressive strength test. The curing system shows that the mortar with the humid temperature curing system produces a higher compressive strength compared to the room temperature curing system.

Keywords: Geopolymer, Fly ash, Admixture, Curing System