Durability assessment of geopolymeric and cementitious composites for screed applications

This research aims to assess the mechanical, durability, and microstructure properties of screed flooring composites produced with different binding materials. Ordinary Portland cement and fly ash were used to produce the cement-based materials, while fly ash and ground granulated blast furnace slag were activated by alkaline solution to formulate the geopolymers. Dune sand and crushed limestone sand were used as fine aggregates, along with different solution-to-binder and binder-to-sand ratios. The results showed that using dune sand instead of crushed sand and increasing the water, solution, and sand contents decreased the compressive strength, impact resistance, and abrasion resistance, and increased the water absorption and rate of absorption. Compared to cement-based counterparts, the use of geopolymers resulted in higher compressive strength, impact and abrasion resistance, and rate of absorption, and lower water absorption. Geopolymer screeds exposed to acetic acid and hydrochloric acid exhibited superior performance than cement-based materials due to better stability of aluminosilicate links produced during geopolymerization. Crushed sand was more reactive with acetic and hydrochloric acid compared to dune sand, leading to inferior performance of associated screeds. With salt attack, the mass of cement screeds was reduced significantly, while geopolymer counterparts remained stable or increased due to matrix densification. This was evidenced by X-ray diffraction, wherein the intensities of the main cement hydration phases decreased compared to those observed in the geopolymeric activated phases.