The thermal power industry is one of the major solid waste-generating industries. With 31 coal thermal power plants in operation, the coal fly ash and slag generate about 18.07 million tons annually. So, the promotion of the treatment and utilisation of this waste as raw materials for building materials production and construction application has been of great interest in Vietnam in recent years. This paper analyses and summarizes the recent results on the physicochemical properties and puzolanic activity of fly ash (FA) that affect its usability in cement, mortar and concrete production. These characteristics are evaluated and compared with the current Vietnamese standard specifications and FAs from other countries (USA, India, China). It can be seen that FA has many beneficial properties such as pozzolanic activity, fine particle composition, spherical and porous particle structure, etc. Therefore, it is very suitable as a mineral additive for cement, mortar and concrete products. Regarding chemical characteristics, most Vietnamese FAs are F class and their loss on ignition content is less than 10%. Therefore, to thoroughly solve the FA generation as well as increase the added value and efficiency of FA, we need to promote the use of high-volume FA in the production of Portland cement blend or cement replacement in sustainable mortar and concrete products in Vietnam.