Dynamic Properties and Fragmentation Fractal Characteristics of Water-Saturated Reef Limestone Concrete under Impact Loading

Reef limestone was used as a coarse-fine aggregate to prepare concrete with a strength class of C30. The mechanism of influences of water-saturated state on dynamic compressive strength, energy dissipation, and macroscopic and microscopic failure modes of reef limestone concrete was studied, and the relationships be-tween fractal dimension and loading rate, fragmentation characteristics, and energy dissipation were discussed. The results indicated that the dynamic compressive strength of reef limestone concrete presents power function growth with increasing loading rate, the free water reduces the degree of cementation among particles and weakens the quasi-static state and dynamic mechanical properties of reef limestone concrete. Meanwhile, under the same loading rate, water-saturated reef limestone concrete demonstrates a stronger energy absorption effect and a greater energy dissipation density, and the energy dissipation density is linearly correlated with the dy-namic compressive strength. In addition, the irregular shape and porous structure of reef limestone aggregate particles effectively enhances the friction strengths between the aggregates and cement slurry, causing most of the dynamic cracks in reef limestone concrete to occur in the cement-sand slurry and aggregates themselves. Finally, the results also show that the fractal dimension of the fragments of reef limestone concrete increases linearly with increases in the loading rate and fragmentation energy dissipation density. At approximately the same loading rate, the fractal dimension of dry specimens was larger, and when the fractal dimensions in the two states were similar, the energy consumed per unit mass water-saturated specimen exceeds that of dry specimens.