Alkaline Activators Concentration Effect to Strength of Waste Paper Sludge Ash-Based Geopolymer Mortar

The purpose of this study is to determine the effect of concentration of sodium hydroxide solution on the strength of Waste Paper Sludge Ash (WPSA)-based geopolymer mortar. Initially, the WPSA samples were been analyzed using X-ray Fluorescence (XRF) to determine the chemical composition. From the XRF analysis, the by-product WPSA manufactured from Malaysian Newsprint Industry (MNI), located at Mentakab Pahang, Malaysia containing higher amount of calcium, silica and alumina. Alkaline solution are from soluble sodium-based used in geopolymerization are combination of Sodium Hydroxide (NaOH) and Sodium Silicate (Na2SiO3). The specimens were carried out on size 50 × 50 × 50 mm cube and fresh mortar were been cured at an oven temperature and ambient temperature. The compressive strength tests were conducted after aging the specimen at 3, 7, 14, and 28 days. The results revealed that as the concentration of NaOH increased, the compressive strength of geopolymer mortar increases. However, the optimum NaOH concentration of WPSA geopolymer mortar is at 12 M. More than 12 M concentrations of NaOH were produced high porosity and decreasing the strength. The range of Na2SiO3 to NaOH solution ratio by mass to produce high strength geopolymer mortar is 2.5. Moreover, curing of fresh WPSA geopolymer mortar is performed mostly at an oven temperature compared to ambient temperature due to heat being a reaction accelerator.