The Impact of Silica Fume Addition on the Early Age Compressive and Flexural Strength of Geopolymer Mortar with Various Binders

The study aims to explore the early age strength of geopolymer mortars using three precursors: palm shell ash, rice husk ash, and clamshell ash, with varying silica fume additions (0%, 5%, 10%, 15%, 20%). The mortars were made with a 3:2 ratio of precursor to activator solution, using sodium hydroxide and sodium silicate in a 1:2 ratio. Beam specimens (4 cm x 4 cm x 16 cm) underwent a flexural test at three days old, followed by a compression test. Results show the highest compressive strength for geopolymer mortar with palm shell ash (GM-PSA) was 36.03 MPa, geopolymer mortar with clamshell ash (GM-CSA) was 32.47 MPa and geopolymer mortar with rice husk ash (GM-RHA) was 36.56 MPa. All of them were reached at 20% silica fume addition. The highest flexural strengths were also reached at 20% silica fume addition, which are 0.31 MPa, 0.24 MPa, and 0.34 MPa for GM-PSA, GM-CSA, and GM-RHA, respectively. Adding silica fume significantly enhanced the compressive and flexural strength of GM-RHA, GM-PSA, and GM-CSA.