Influence of processed tea waste ash on the hydration products and mechanical property of hybrid cement as an eco-friendly solution

The waste generated during production in tea factories is increasing with the growth of the world population. Storage of tea waste creates problems in terms of location and environment. The aim of this study was to investigate the usability of tea waste ash in hybrid concrete to re-introduce tea waste into the economy and turn it into a useful material in the construction industry. Therefore, processed tea waste ash (PTWA) was first burned in an uncontrolled and then burned in a controlled combustion process at 650 °C. In the hybrid cement design, ground blast furnace slag was kept constant at 50 %, and PTWA was replaced with ordinary Portland cement at 0 %, 1.25 %, 2.5 %, 3.75 %, 5 %, 7.5 %, and 10 % by weight of the total binder (GBFS + OPC + PTWA). Experiments for pastes and mortars were performed for 2, 7, 28, and 90 days. Mineralogical properties (XRD, FTIR, TGA/DTA) of the paste samples were analyzed. Mechanical tests (compressive strength, initial/final setting time, flow table, leaching) were carried out on mortar samples. The results revealed that initial and final setting times (up to 10 min and 60 min, respectively) decreased significantly as the amount of PTWA substitution increased. The performance of the mortars with PTWA was observed to diminish compared to the reference for each cure age. It was determined that PTWA affected the reduction of portlandite, and this was observed most in mixtures containing 10 % PTWA. It is believed that using PTWA together with GBFS as an alkaline activator will be beneficial to the environment.