Physical and mechanical properties of coral aggregates in the South China Sea

Coral aggregate (CA) is a type of marine resource with rich storage capacity and complex physical characteristics, and it is increasingly recognized as an important island engineering material. For the regional variability of CA in the South China Sea, the physical and mechanical properties of different CAs were experimentally studied in this paper. Using the X-ray Computed Tomography technique, the pore characteristics of CA were quantitatively studied in term of the pore shape, size, sphericity, number, volume, etc. Additionally, the uniaxial compressive properties of cylinder CA samples were investigated in term of the failure patterns, stress-strain curves, elastic modulus, strength, and toughness. Results indicate that different CA samples contain a considerable amount of pores with different shapes that are closely related to the coral growth environment. It was found that content of the millimeter-sized pores with a diameter of 0.5∼1 mm is the highest, while the content of the centimeter-sized pores with a diameter greater than 1 cm is the lowest. The porosity of light and heavy CA was determined as 1.37%–22.55% and 3.72%–22.64%, respectively. Splitting failure is the main form of failure to CA under uniaxial compression loading. While the compressive toughness of CA could be effectively improved by the surface-filling method treatment using coral mortar. According to the present results and the existing data, a series of regression equations concerning the physical-mechanical properties of CA were established, which has significant values for the study and application of CA in the South China Sea.