Potential improvement of clinker sand in the mechanical high temperature and transport properties with GGBS-based prepacked geopolymer composite

Abstract

In this study, a new generation prepacked geopolymer composite (PGC) material that can meet different needs was obtained by combining geopolymer concrete (GPC) and prepacked aggregate concrete (PAC) technology. In the production of PGC, 5-8 mm quartz aggregates were placed in molds and, geopolymer mortar was injected between these aggregates. Aluminosilicate based blast furnace slag (GBFS) was used as binding in geopolymer mortars; sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) was used as alkali activator. In addition, clinker aggregate in different proportions was used as fine aggregate (0–4 mm) in the production of mortar. Within the scope of the study, the physical, mechanical, permeability and high temperature resistance properties of PGC were investigated. The produced samples were cured at 30 and 60 °C for 6 and 8 hours. Hardened unit weights of PGC vary between 2342 and 2539 kg/m3, and sorptivity values vary between 0 and 0.04 kg/m2.min0.5. While the increase in curing temperature and curing time increases the hardened unit weight values, it decreased permeability values. While the increase of clinker aggregate in the mortar phase does not change the hardened unit weight, it significantly reduced permeability. When the PGC samples are cured at 30 °C, the compressive strengths are 20.38–39.03 MPa; when curing at 60 °C, the compressive strengths are 35.21–57.04 MPa. Flexural strengths, 2.35–6.96 MPa with 30 °C cure, achieved 4.27–9.93 MPa results with 60 °C curing. Increasing the curing time and curing temperature significantly increased the compressive and flexural strengths. The increase in the amount of clinker aggregate added to the mortar phase decreased the strength values. While the compressive strength values of PGC mixtures do not fall below 15 MPa after being exposed to 300 °C high temperature; after the application of 600 °C high temperature, it lost up to 70% of its strength. Increasing the curing time and curing temperature, increased the high temperature resistance. The increase in the amount of clinker aggregate in the mixtures, decreased the strength loss rate.