Feasibility study on the use of processed waste tea ash as cement replacement for sustainable concrete production

In this study, processed waste tea ash (PWTA) generated by the boiler combustion of processed solid waste tea was used as a cement replacement at weights of 0%, 10%, 20%, 30%, and 40%. The effect of PWTA on the concrete properties was examined using the slump, density, compressive strength, porosity, chloride penetration depth, and microstructure as well as the embodied carbon content of concrete. Further, the contribution of the pozzolanic effect of PWTA to concrete strength was quantitatively analyzed using strength indices. The results showed that the slump and density of concrete decreased with the addition of PWTA. The concrete specimens with 10% PWTA achieved a similar compressive strength to that of control concrete at 28 days and a 4.57% higher value at 90 days due to the continuous pozzolanic reaction of PWTA. Strength indices also showed that the pozzolanic effect of 10% PWTA positively contributed to concrete strength at 90 days with a P value of 14.09%, which was higher than the percentage amount of PWTA used in the mixture. Owing to the pozzolanic reaction, the porosity and chloride pene- tration depth of 10% PWTA concrete at 90 days are lower by 4.2% and 9.4%, respectively, compared to those of control concrete. With the addition of PWTA up to 10%, the embodied carbon and carbon dioxide intensity could be reduced by 8.32% and 7.85%, respectively, compared with those of control concrete. These results suggest that PWTA is a useful replacement for up to 10% cement, enabling the production of innovative building materials for sustainable environment, with strengths similar to that of Portland cement.