THE EFFECT OF ADMIXTURE VARIATIONS ON WORKABILITY AND COMPRESSIVE STRENGTH OF GEOPOLYMER CONCRETE FLY ASH BASED WITH HIGH CALCIUM CONTENT

The use of class C fly ash on geopolymer concrete causes flash setting characteristics. The objective of this research is to analyze how the addition of admixture as an alternative delay flash setting increases the workability of concrete. In this study, geopolymer concrete was made with admixture variations of 0%, 0.5%, 1%, 1.5%. The alkaline activator used in this study was 10 M NaOH and Na2SiO3, and the activator ratio was 1:1. The type of admixture used is sucrose. The tests carried out were: compressive strength at the age of 7, 14, 28, 56 days, slump test, permeability test, porosity test, and resistivity test. The mixing method applied was the dry mixing method, where the alkaline activator used was in a dry form (solid) crushed with fly ash to produce geopolymer cement. Geopolymer cement was mixed with water fine and coarse aggregates to make geopolymer concrete. The results of this research show that the slump values for the 0%, 0.5%, 1%, and 1.5% are 12.5 cm, 16.5 cm, 18.5 cm, and 19.5 cm, respectively. Whereas the average compressive strength of 3 cylinders of geopolymer concrete aged 28 days is 16.58 MPa, 29.55 MPa, 35.29 MPa, and 29.05 MPa, respectively. The effective admixture in this study is 1%. Since the addition, 1% admixture increases the workability of geopolymer concrete without reducing its compressive strength. The admixture used in this study is 1%. It is the most effective amount as it increases the workability of geopolymer concrete without reducing the compressive strength.