Effect of waste travertine powder on properties of rhyolitic tuff-based geopolymer

Abstract

This investigation explores the potential of geopolymer technology as an eco-friendly substitute for conventional construction materials by emphasizing the innovative use of naturally occurring green rhyolitic tuff and repurposed travertine powder in geopolymer paste formulations. Replacement levels of tuff with travertine at 40 %, 45 %, and 50 %, along with an alkaline solution with a NaOH molarity range of 8.2 M-22.1 M, have been analyzed for their impact on flowability, water absorption, porosity, compressive strength, and unit weight of the geopolymers over curing periods of 2, 28, and 90 days. The flowability measurements show that adding 40 %, 45 %, and 50 % travertine leads to approximately 7 %, 31 %, and 31 % reductions in the flowability of the geopolymer, respectively. It is demonstrated that adding 40 % travertine significantly improves the geopolymers' compressive strength with an 11.5 M NaOH concentration, showing substantial increases of approximately 15.5, 9.0, and 2.4 times at the curing duration of 2, 28, and 90 days, respectively, relative to the geopolymer without travertine. As an optimum points, an 18.5 M NaOH and an 0.7 solution-to-powder ratio decrease the long-term apparent porosity and water absorption of the geopolymer without travertine by about 14 % and 19 % compared to those at the same solution-to-powder ratio with 11.5 M NaOH, respectively. Microscopic examinations were employed to validate the development of sodium aluminosilicate hydrate, calcium aluminosilicate hydrate, and calcium silicate hydrate gels, underscoring the advantageous contribution of the elevated CaO content in the travertine to the geopolymer matrix. This research not only highlights the environmental benefits of repurposing waste materials but also contributes to the development of more sustainable and durable geopolymer pastes, offering a promising approach to enhancing environmental stewardship in material science practices.