Coal bottom ash is one of the waste materials generated by coal thermal power plants. In the world, there is a huge amount of coal bottom ash released to the environment every year. The availability of such coal bottom ash with insufficient treatment method leads to many serious environmental troubles. Therefore, turning this waste ash into useful construction material is concerned by many researchers so far. The performance of concrete incorporating coal bottom ash as a natural sand substitution was evaluated in this study through the compressive strength and other nondestructive tests of ultrasonic pulse velocity, water absorption, porosity, electrical surface resistivity, and thermal conductivity. Moreover, the scanning electron microscope was also used to characterize the microstructure of the hardened concrete. In this study, coal bottom ash sourced from Vietnam was used to replace the natural sand in the normal-strength concrete at different replacement levels of 0, 30, 50, 70, and 100% by weight. The results show that using coal bottom ash to replace natural sand was found to have a significant influence on the properties and performance of concretes. The compressive strength, ultrasonic pulse velocity, electrical surface resistivity, thermal conductivity, water absorption, and porosity values of concretes were measured in the ranges of 14.2 – 27.7 MPa, 4336 – 4823 m/s, 6.41 – 12.25 k
cm, 1.202 – 1.739 W/mK, 2.47 – 5.72%, and 3.72 – 8.34% after 28 days of curing, respectively. In real practice, therefore, an optimal coal bottom ash replacement level will be suggested with the consideration of specific requirements for the quality of concrete used in particular applications. The results of this study further demonstrate the good performance of concrete incorporating coal bottom ash and the optimal replacement level of natural sand by coal bottom ash was 30%.