The purposes of this study are to produce the unfired bricks incorporating high bottom ash content and evaluate their
quality through modern techniques. Four brick mixtures were designed with a constant water-to-cement ratio of 0.40 and using bottom ash as fine aggregate to replace stone powder at different replacement levels of 50, 70, 85, and 100%. Besides the basic engineering properties, the relative quality, chemical attack resistance, and heat isolation of bottom ash bricks were tested through using modern testing equipment. The microstructure of bricks was also assessed by using scanning electron microscopy (SEM). Test results indicated that although the properties of bricks decreased with increasing bottom ash content, all bottom ash bricks in this study showed a good quality compared to the specifications of TCVN 6477-2016. More voids and micro-cracks were observed in the SEM image of brick samples with high bottom ash content. Moreover, the thermal conductivity of bottom ash ranged from 0.69 to 1.38 W/m.K. It is recommended that the durable property of the bottom ash brick is considered as good if the ultrasonic pulse velocity value of above 3360 m/s and the electrical resistance value of above 18.3 k“.cm. This study also demonstrated the possibility of using 100% bottom ash as fine aggregate instead of stone powder in the production of the unfired bricks.