۱٫۱٫ AAC

material It is generally known that the Portland cement industry produces 5–۸% of the anthropogenic CO2 [1] emission, which contributes significantly to the increase in greenhouse gas. Therefore, there is a need to develop alternate concrete binders other than Portland cement. According to previous studies [2,3], the properties of alkali activated cement (AAC) are comparable or even superior to Portland cement. A number of studies have demonstrated that the AAC exhibits high compressive strength [4,5], excellent sulphate and seawater resistance [6,7], good performance in the environment of acid corrosion [8,9], good resistance to chloride penetration [10] and freeze–thaw cycles [11,12]. These advantages are attributed to the special nature of the hydration products and the lower porosity and permeability of the AAC. Due to its high strength and excellent durability properties, the AAC mortar/concrete has potential applications in a range of applications. In Australia, pre-mixed alkali-activated concrete has been commercialized for the construction of a bridge upgrade project [13]. Also, AAC precast footpath panel segments produced from blends of fly ash, slag and alkaline activators has been successfully demonstrated in an industrial application [14]. In Ukraine, alkali activated blast furnace slag cement has been used in the construction of apartment buildings, road sections, pipes, drainage and irrigation channels, flooring for dairy farms, precast slabs and blocks [15]. Another known application for AAC was in the production of railway sleepers. Spain led the development of pre-stressed steam-cured sleepers based on alkali activated fly ash [16]. Basically, this AAC material can be produced through the alkaline activation of aluminosilicate materials such as coal fly ash (FA) and ground granulated blast furnace slag (GGBS). But in Hong Kong, there is no any steel plants for producing GGBS and almost all FA has already been used up by the construction industry.