LAUSR

Abstract Brazil produces 900 mi m2 of ceramic tiles annually, which generates about 60,000 tons of porcelain tile polishing residue (PPR). In previous work, the authors confirmed the feasibility of using PPR in the production of geopolymer pastes regarding mechanical and microstructural properties. This work investigated the rheological and ecological performance of geopolymer pastes and mortars produced with metakaolin replacement by PPR in 0–100%, activated with Na2SiO3/NaOH solution. Rotational rheometry and mini slump test were conducted in pastes, in addition to flow table test for mortars. Furthermore, the CO2 emission related to 1 m³ of mortar was estimated for each composition. Results showed that geopolymer pastes behaved as a Bingham fluid (R2 of 0.999–1.000). The increase in PPR level linearly decreased the yield stress of the pastes from 10.5 to 0.2 Pa, and the viscosity from 4.2 to 1.5 Pa.s. Furthermore, PPR incorporation progressively increased the spread of the pastes (mini slump) and mortars (flow table) by up to 20% and 17%, respectively. The yield stress and mini slump spread of the pastes showed a linear correlation with R2 of 0.992, indicating that this test is efficient to assess the yield stress of geopolymer pastes, as widespread for Portland cement pastes. Finally, PPR incorporation progressively reduced the CO2 emission per m³ of mortar from 636 (0% PPR) to 532 kg CO2-eq/m³ (100% PPR). Replacing 15% metakaolin with PPR reduced the CO2 intensity of the material (i.e. kg CO2-eq/m³.MPa) by 11% and 7% respectively at 7 and 28 days. Overall, PPR incorporation improved the fresh and hardened performance of metakaolin-based geopolymer composites while reducing its CO2 emission, reinforcing the good technical and environmental performance of the residue as binding material.