Ceramics-Silikáty

This study investigates the influence of the curing conditions on the mechanical performance of a geopolymer mortar synthesised from fly ash (FA) and ground granulated blast-furnace slag (GGBS). These industrial by-products serve as a low-carbon alternatives to conventional cement, enabling reduced CO₂ emissions and efficient waste utilisation. Fourteen geopolymer mortar mixtures were prepared using different fly ash:ground granulated blast-furnace slag ratios (50:50, 30:70, and 70:30). They were activated using an alkaline solution composed of a sodium hydroxide (SHS) solution at different molarities (2.5 M, 5 M, 7.5 M, and 10 M), and a sodium silicate solution (SSS). The alkaline solution was formulated by combining sodium hydroxide flakes (SHFs) and a sodium silicate solution (SSS) in varying ratios from 1:1 to 1:3. The geopolymer mortars were subjected to four curing regimes: ambient curing, water curing, oven curing, and steam curing. The mechanical performance was assessed in terms of the compressive and flexural strength. The results show that the water curing notably enhanced the strength in the mortars with equal proportions of FA and GGBS (50:50), activated with high molarities of the sodium hydroxide solution (5 M to 10 M) compared to ambient conditions. The oven and steam curing facilitated a rapid early strength gain, though the later-age strength gain is limited. The study highlights the crucial role of the curing type and duration in influencing the strength development and structural integrity. The steam- and oven-cured GP mortars with equal FA and GGBS proportions achieved approximately 98%, 80%, and 79% of their 28-day strength at the 14th day when activated with 5 M, 7.5 M, and 10 M SHS, respectively. These findings provide valuable guidance for optimising the curing strategies to enhance the performance and sustainability of geopolymer mortars in eco-conscious construction practices.