Abstract:Alkali slag cementitious material is a material with high strength and high durability. However, its great shrinkage and easy-cracking properties are the main reasons to restrict its wide application. The ring crack testing method is used to study the effect of single or multiple additions of MgO expansion agent, polypropylene fiber and shrinkage reducing agent on the cracking properties of alkali slag cementitious material. The study results show that the single addition of MgO expansion agent is not good for cracking resistance of alkali cementitious system, but the additions of shrinkage reducing agent and polypropylene fiber can effectively delay the formation of cracks and reduce a cracking area.