*Article* **Effect of Superfine Cement Modification on Properties of Coral Aggregate Concrete**

**Fei Wang 1, Jianmin Hua 1, Xuanyi Xue 1,\*, Neng Wang 2, Feidong Yan <sup>1</sup> and Dou Feng <sup>1</sup>**


**Abstract:** In marine engineering, using corals as aggregates to prepare concrete can reduce both the exploitation of stones and the transportation cost of building materials. However, coral aggregates have low strength and high porosity, which may affect the workability and mechanical properties of concrete. Hence, superfine cement is used innovatively in this study to modify coral aggregates; additionally, the effects of the water–cement ratio and curing time on the water absorption and strength of modified coral aggregates are investigated. Modified coral aggregate concrete is prepared, and the effect of using modified superfine cement on its workability and strength is investigated. Experimental results show that when the water-cement ratio exceeds 1.25, the slurry does not form a shell on the surface of the coral aggregates and the water absorption of the coral aggregates increases significantly. The strength of the modified coral aggregates cured for a short duration is slightly lower than that of unmodified coral aggregates, whereas that cured for 28 days is approximately 20% higher than that of unmodified coral aggregates. Using superfine cement to modify coral aggregate concrete can improve its workability, but not its compressive properties.

**Keywords:** coral aggregate concrete; superfine cement; aggregate modification; physical property; mechanical property; concrete workability
