The production of cement and traditional fired clay bricks consumes intensive energy and inversely affects the environment. In addition, a huge quantity of solid waste materials such as rice husk ash and fly ash (FA) are generated from both industrial and agricultural activities. This study investigates the use of unground rice husk ash (URHA) and FA for manufacturing unfired building bricks. FA was used as a cement substitute (15%, 30%, and 50%), whereas URHA was used as a chippings replacement (5%, 10%, and 15%) in the brick mixtures. Test results indicate that all of the brick samples had consistent dimensions and were free of visible defects. Generally, increasing the URHA or FA replacement levels reduced the strength, bulk density, and material cost. However, it increased the water absorption capacity of the brick samples. Moreover, bricks with 10% URHA and 50% FA registered the lowest cost. Properties of all of the brick samples met the Grade M15 requirements of the TCVN 6477-2011 standard of high-quality unfired building bricks. | Engineering properties of unfired building bricks produced using URHA-FA cement blends
