Oil Palm Ash-based Geopolymer Mortar with Variation Na2SiO3/NaOH Ratio

Geopolymer concrete is an environmentally technology which is nowadays becoming an alternative to Portland cement as a construction material. Geopolymer material selection is utilized as one of the local plantation industry waste such as oil palm ash. Polymerization process performed the oil palm ash as precursors that contains high silicate-calcium with Na2SiO3 and NaOH as alkali activator. Mix design is carried out by a ratio of alkali activator 2,0, 1,5 and 1,0 at a concentration of NaOH 8, 10, 12, 14 and 16 M at a temperature of 90 degrees C for 24 hours. The method used is the method separate mixtures with extra water and mixed methods directly without extra water. The result shows that the higher concentration of NaOH solution, the compressive strength is increased at level of 12,4 MPa = 8,4 M for the mortar with extra water and 20,2 MPa = 16 M without extra water at a ratio of 1,5 alkaline activators. The ratio mixture of alkali activator 1,0 and 2,0 would produce a low compressive strength. Microstructure result shows that the matrix is formed more solid at each increase in the concentration of NaOH solution. The ratio of alkali activator 1,5 causes precursor and alkaline activators to react homogeneously so that the geopolymerization process is more complete.