Abstract: The steeply inclined layered rock masses of the roadway roof is prone to "slip along the bedding" break along the weak bedding surfaces. The expansive slurry is used to slurry the weak bedding surfaces to produce the "first squeezing and then bonding" reinforcement effect，which could improve the strength and integrity of the roof surrounding rock. Aiming at the expansion grouting reinforcement and support technology，the concept of expansive slurry was proposed， and the expansion mechanism of expansive slurry was analyzed. The selection of expansive materials for the expansive slurry is the key issue.By summarizing the development history of various expansive materials and the research status at home and abroad，the expansion mechanism of them were discussed. The properties of expansive materials were analyzed from four aspects such as expansion development time，volume expansion rate，mechanical strength，and expansion stress. On the basis of these，HSCA- Ⅱ static cracking agent was selected as the expansion source. The expansion development time，volume expansion rate and mechanical strength characteristics of the static cracking agent-cement expansive slurry were analyzed through the tests including the expansive slurry ratio test and volume expansion rate test，mechanical strength test. Research results show that with the increase of the content of static cracking agent，the compressive strength of the static cracking agent-cement expansive slurry decreases，the expansion development time is prolonged，and the volume expansion rate increases. The static cracking agent-cement expansive slurry has reasonable expansion development time，large volume expansion rate，high self-strength，and the expansion stress can provide squeezing force in supporting rock mass，which may have good engineering application significance. In order to achieve good engineering application effect，a large number of theoretical and experimental studies need to be carried out in the following directions in the later stage:optimization and development of expansive materials，expansion mechanism of expansive slurry，mechanical behavior of expansive slurry rock mass，mechanism of expansion solidification flow coupling of expansive slurry，theoretical and technical research of expansive slurry support，etc.

Key words: expansive slurry, expansion mechanism, expansive materials, static cracking agent