High temperature performance of geopolymers based on construction and demolition waste
Ioanna Giannopoulou, Ponsian M. Robert, Konstantinos-Miltiadis Sakkas, M. Petrou, Demetris Nicolaides
Abstract
This paper reports an experimental study on the thermal stability and mechanical performance of geopolymers developed entirely with construction and demolition waste precursors, either bricks or ceramic tiles, upon their firing at temperatures between 600 and 1050 οC. The waste brick- and waste tile-based geopolymers were prepared with solid to liquid ratios of 2.4 and 3.4, respectively, using combined aqueous solutions of potassium hydroxide (KOH) and sodium silicate (Na2SiO3), as alkali activator. After curing for 7 days at 50 οC and hardening for 7 and 28 days at ambient temperature, the geopolymers were exposed to 600, 800 and 1050 °C for 2 h and their compressive strength, apparent density and mass loss were measured. Both materials showed good thermal stability up to 1050 °C, without observing any change in the shape of specimens or thermal deformation. The waste brick-based geopolymer developed a compressive strength of about 19 MPa after ageing for 7 days and kept it in the range of 15–21 MPa, after its exposure to 600–1050 °C. At 1050 οC, the material showed a decreased density by 8% and mass loss about 10%. The compressive strength of the waste ceramic tile-based geopolymer was about 33 MPa after 7 days of hardening and decreased to about 17 and 13 MPa, after exposure to 600 and 800 οC, respectively. At 1050 οC, its compressive strength was slightly increased compared to the initial one. At this temperature, the density of the material decreased by almost 9%, while it lost about 7% of its initial mass. Based on these results, both the developed geopolymers had the potential to find fire resistance applications in the sector of building materials.