This paper examines diatomite (DM) and sugarcane bagasse ash (SBA) for use as partial replacements for fine aggregates in the manufacture of hollow concrete blocks, which are used in non-structural applications. Several key findings were recorded through tests on mechanical and durability performance. Substitution of fine aggregates with DM or SBA significantly reduced the bulk density, with SBA having a slightly higher reduction. Concrete compressive strength stabilizes after 28 days, with 20% replacement of DM and SBA resulting in significant strength reductions-83.7% for DM and 46.2% for SBA. Thermal conductivity showed a remarkable reduction of 65.4% and 47.3%, respectively. Moreover, the DM addition significantly improved the sound absorption capacity due to the increased void fraction. These results underline the viability of DM and SBA as sustainable alternatives to fine aggregates, exhibiting superior thermal and acoustic performances besides offering solutions to environmental concerns on the use of wastes.