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This study aims to conduct research about the microstructure and basic properties of recycled aggregate concrete under seawater corrosion. Concrete specimens were fabricated and tested with different replacement percentages of 0%, 30%, and 60% after immersing in seawater for 4, 8, 12, and 16 months, respectively. The basic properties of recycled aggregate concrete (RAC) including the compressive strength, the elastic modulus, and chloride penetration depth were explicitly investigated. And the microstructure of recycled concrete aggregate (RCA) was revealed to find the seawater corrosion by using scanning electron microscope (SEM). The results showed that higher amount of the RCA means more porosity and less strength, which could lower both the compressive strength and resistance to chloride penetration. This research could be a guide in theoretical and numerical analysis for the design of RAC structures.

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The 3-D four-direction braid carbon/epoxy composites have been tested in compression under quasi-static loading and high strain rate loading. And the tests were conducted at strain rates up to 2000/s by split Hopkinson pressure bar (SHPB) and MTS in the paper. The loading pulses in split Hopkinson pressure bar apparatus were modified by pulse shaping techniques such that the samples are in dynamic stress equilibrium and deformed at a nearly constant strain rate over most of the dynamic compression duration. The results indicated that the peak stress and stiffness along the transverse direction were larger than those along the thickness direction. In addition the effect of the strain rate on peak stress and the stiffness was also discussed in the paper.