Abstract
Natural rocks of magmatic origin are alternative precursors in alkali-activated materials and provide opportunities in the search for more environmentally friendly binders compared to portland cement. The pumice is one of these rocks and its amorphous structure and chemical composition make it one of the candidates as a precursor in producing geopolymer binder when finely ground. Since the majority of the pumice reserves are located in Turkey increases its potential utilization in this area, even more. This paper evaluates the physical, mechanical, and microstructural properties of geopolymer pastes and mortars manufactured with pumice powder (PP) and ground granulated blast furnace slag (BFS) with the activating agents sodium hydroxide (NaOH), potassium hydroxide (KOH), and sodium silicate (SS) solution. The experimental results showed that the compressive strength of the geopolymer pastes was mainly affected by the activator concentration and the PP ratio, rather than the activator type, for single activator mixes. However, the incorporation of SS changed this trend as the KOH and SS combination resulted in higher compressive strength compared to the NaOH and SS. The gradual increase of the PP ratio in the mix design decreased the density and thermal conductivity, on the other hand, increased the water absorption values of the geopolymer mortars. However, the physical properties were insignificantly changed in geopolymer mortars incorporating 60, 70, and 80% of PP in the binder.
Highlights
Concrete is utilized more extensively throughout the world on a volume basis than any other engineered material because of its indispensable role in the construction industry
The compressive strength of the geopolymer paste mixes was investigated using different concentrations of NaOH, KOH independently, and in combination with sodium silicate (SS), and the results are presented in Figs. 5-6 and Table 5
The results showed that the paste mixes containing KOH and SS alkaline solution had higher compressive strength compared to that of the mixes with NaOH and SS, and the highest strength at 28 days was observed as 29.0 MPa in P-6K-SS1.0 mix
Summary
Concrete is utilized more extensively throughout the world on a volume basis than any other engineered material because of its indispensable role in the construction industry. Safari et al [31] studied the mechanical properties of pumice-based geopolymer paste with an alkaline solution of sodium hydroxide and sodium silicate cured at different temperatures and durations. They claimed that optimum compressive and flexural strength could be obtained with the alkali solution of concentration 12 M cured at 60°C for 120 hours. The present study aims to contribute to the knowledge on the PP-based geopolymer materials by investigating the effect of alkali activator type and concentration as well as the PP and BFS mix ratio on the physical, mechanical and microstructural properties of ambient cured geopolymer paste and mortar
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