Abstract:Coral sand, a kind of special soil, which mainly consists of biological bone fragments, shells and corals, has a great difference from the terrigenous sand in properties of making cement mortar. In order to solve this problem, the coral sand from the South China Sea was used for making cement mortar to conduct a compressive test, which considered the factors such as different mix proportion and different curing period. And, some of the specimens were scanned electron microscope test. The test results show that: the compressive strength of coral sand cement declines nonlinearly with the climbing aggregate-to-cement ratio; the compressive strength of cement mortar with low ratio of coral sand increases relativelySlargely with curing time developing; at the early period of curing, the compressive strength of cement coral mortar is relatively higher than that of cement mortar made of river sand, but it is lower than that as the curing time increasing; the wedge-shaped structure in coral sand cement mortar can improve the compressive strength of the cement mortar, however, holes inside coral sand and its fragile characteristics prevent the cement stone structure from forming a complete body, thus reducing the compressive strength of coral sand mortar.