Utilization of tea waste as a bacterial carrier in self-healing mortars

Abstract

The protection of bacteria in self-healing composites is crucial for an effective healing process. However, materials used for protection often require advanced techniques and incur additional costs. This study investigates the use of tea waste as a bacterial carrier and natural fibre reinforcement in mortar. Tea waste, a fibrous by-product with high water absorption capacity, was used as a bacterial carrier for Bacillus megaterium spores. Mortar samples with different amounts of tea waste containing bacteria were evaluated through crack healing analysis, compressive strength, water absorption, ultrasonic pulse velocity (UPV), capillarity, and microstructural analyses. Additionally, the healing efficiency of the mortars was investigated using pre-cracked specimens. The results showed that tea waste effectively absorbed and protected the bacterial spores. Due to its fibrous nature, tea waste restricted cracks and created a more favourable condition for self-healing. Bacterial mortars with tea waste repaired cracks up to 0.68 mm wide and exhibited a 26.49% increase in compressive strength compared to control samples after 90 days. Moisture from the tea waste improved the bacterial environment and promoted internal curing, leading to denser structures with higher UPV, reduced water absorption, and lower capillarity. Scanning electron microscopy analysis confirmed that tea waste supported bacterial calcite formation. FT-IR analysis demonstrated that tea waste was highly compatible with the bacterial mortar matrix. Consequently, the incorporation of tea waste led to a notable presence of bacterial calcite products within the mortar structure. The findings indicate that tea waste can be effectively utilized to enhance the self-healing capabilities of mortars.