High-temperature resistance of ceramic sanitaryware waste and fly ash-based geopolymer and hybrid geopolymer mortars produced at ambient curing conditions

Abstract

In this study, five different hybrid geopolymer mortar mixtures were prepared, incorporating two different geopolymers and low percentages of Portland cement (PC), (16.6 % and 33.3 %). In geopolymer mixtures, 100 % ceramic sanitaryware waste (SW) and 100 % fly ash (FA) were used as precursor materials. In hybrid mixtures, the precursor materials include FA+ PC, SW+PC, and FA+SW+PC. The flexural and compressive strengths of mortars were determined up to 56 days to investigate their strength development. Additionally, the mortars were exposed to elevated temperatures up to 800 °C, separately. After the high-temperature exposure, phase (XRD) and microstructure (SEM/EDS) analyses were conducted on the selected mortars. All the hybrid geopolymers had higher flexural and compressive strengths than the geopolymers for all the curing ages. The highest 28-day flexural and compressive strength values of 5.3 MPa and 37.0 MPa were obtained on the mixture where FA+SW+PC precursors were used in equal amounts, respectively. The geopolymer and hybrid geopolymer mortars (containing 16.6 % PC) performed well under the high-temperature effect up to 800ºC. The strength values of all the mortars were obtained higher at 800ºC than at 600ºC. After high-temperature exposure, additional crystalline phases such as gehlenite were detected in hybrid mortars.