Development of Geopolymer-Based Reactive Powder Concrete Using Particle Packing Approach

This study investigated the development of geopolymer-based reactive powder concrete (RPGC) as an eco-friendly alternative to traditional Portland cement–based reactive powder concrete. Two groups of RPGC mixes (M1 and M2) were developed using ground granulated blast furnace slag (GGBFS) and fly ash (FA) as primary precursors. Each group included three mixes with varying liquid ratios, designed based on the particle packing approach. Optimization of liquid content was achieved through wet packing tests to maximize particle packing factor. The packing of particles of the RPGC mixes was found to be dependent on the liquid (alkali activator) ratio. The packing factor increased with the increase in the liquid ratio until reaching an optimum liquid ratio, beyond which further increase in the liquid ratio led to a decrease in the packing factor. For the liquid ratio below the optimum liquid ratio, the mixes were dry and unable to form a paste-like consistency to be defined as concrete. A liquid ratio of 0.50 was found to be optimal for both mix groups, M1 and M2. In the fresh state, RPGC mixes achieved their highest packing factor at the optimum liquid ratio, resulting in the lowest apparent volume of permeable voids (AVPV) in hardened concrete. As the liquid ratio increased beyond this optimum liquid ratio, the packing factor decreased, leading to higher AVPV values. The RPGC exhibited the highest compressive and flexural strength at the optimum liquid ratio, corresponding to the highest packing factor and lowest AVPV. The RPGC with GGBFS (M1) achieved an average compressive strength of 108.9 MPa and those with blended GGBFS and FA (M2) achieved an average compressive strength of 64.3 MPa for the optimum liquid ratio. At the optimum liquid ratio, the flexural strength of the RPGC with GGBFS was observed to be 8% of the compressive strength, while it was 10% of the compressive strength for the RPGC with blended GGBFS and FA. Both the compressive and flexural strengths decreased with increasing liquid ratio as the packing factor had an inverse relationship with the liquid ratio.