MICROSCOPICAL EXPLORATION OF POND ASH-INDUCED COMPRESSED INTERLOCKING BRICKS

Burnt clay bricks are widely used across India and remain one of the most essential materials in building construction. However, the excessive extraction of clay poses a threat to society, as brick kilns largely rely on high-quality clay sourced from agricultural land. To counter this issue this study evaluates the compressive strength and microstructural characteristics of pond ash-induced compressed interlocking bricks made using fly ash, pond ash, quarry dust, and varying amounts of lime and cement. Four different mixes (S1 to S4) were tested for compressive strength after 28 days, with the S2 mix containing 10% lime and no cement achieving the highest strength of 5.48 N/mm². SEM analysis showed a dense microstructure in S2, while S1 exhibited unreacted fly ash and calcium hydroxide, resulting in a lower strength of 3.94 N/mm². XRD results confirmed the presence of calcium silicate hydrate (CSH) gel in S2, responsible for the enhanced strength. EDAX analysis highlighted the highest calcium content in S2, further indicating the extensive pozzolanic reactions leading to better densification. The study confirms that the use of lime alone, in the absence of cement, can result in higher compressive strength through improved microstructural development.