Abstract

This article reports the strength development and microstructure characteristics of a fly ash (FA) geopolymer system prepared with an alkaline activator consisting of sodium hydroxide (NaOH) solution and liquid sodium silicate (Na₂SiO₃). The effect of Na₂SiO₃/NaOH mass mixing ratio on the compressive strength and microstructure characteristics of hardened FA geopolymers at different ages was investigated. The influence of different curing conditions on the strength development of the FA geopolymer was also explored. The experimental results revealed that the alkaline activator prepared with Na₂SiO₃/NaOH ratio of 1.00 provides sufficient alkalinity to promote the geopolymerization reaction and development of high-strength FA geopolymer material. The scanning electron microscopy (SEM) results showed that the dissolution rates of the FA extremely affected by the content of NaOH solution in the liquid activator. Also, the most effective curing regime was 70 °C for 24 h to produce geopolymers with optimal strength at different aging periods. 

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