The construction sector is responsible for a significant share of global CO₂ emissions, primarily from Portland cement production. Rice husk ash (RHA), an agro-industrial by-product rich in amorphous silica, offers a promising pozzolanic substitute for cement. This study evaluates the mechanical and durability performance of solid masonry blocks (215 mm × 105 mm × 65 mm) incorporating 10% RHA as a partial cement replacement, with RHA produced by open-air burning and controlled furnace calcination at 350°C, 650°C, and 800°C. All ash was ground and sieved to below 75 μm. Blocks were cured by the sprinkler method for 7 and 28 days, then tested for compressive strength (ASTM C129), water absorption (ASTM C642), and density. The 650°C-calcined RHA blocks achieved the highest 28-day compressive strength of 12.62 MPa, surpassing the plain cement control (11.24 MPa), while still meeting acceptable water absorption limits (13.35% vs. the 20% threshold). Open-burned RHA blocks performed worst due to incomplete combustion and elevated residual carbon. These results confirm that 650°C is the optimal calcination temperature for RHA intended for masonry block production, supporting its use as an eco- friendly, cost-effective partial cement replacement.