Experimental Study On Dynamic Tensile Of Typical Engineering Material

In the thesis, static and dynamic mechanical properties under direct tensile, splitting and spalling of the recycled aggregate concrete (RAC) are studied. The main research content is as follows:1. To study the direct tensile properties and fracture patterns of RAC with various replacement percentage (i.e.0%,25%,50%,75% and 100%) of recycled coarse aggregates (RCA), the quasi-static and dynamic direct tensile tests of RAC in the strain-rate range of 100-102 s-1 were carried out using WDW-100 double pillar microcomputer control electronic universal testing machine and large diameter (75 mm) split Hopkinson tensile bar (SHTB), respectively. Test results show that the tensile strength of RAC increases with the increase of the average strain-rate, and the average strain-rate affects the damage form of RAC, which indicate that the RAC has obvious rate sensitivity. Under the same water cement ratio, the quasi-static and dynamic tensile strength of RAC is 1.3%-15.9% and 1.7%-29% lower than that of ordinary concrete, respectively.2. In order to study the RAC splitting tensile properties and fracture state with various RCA replacement percentage (i.e.0%,25%,50%,75%,100%), the quasi-static and dynamic splitting test of RAC was carried out using The MTS-815 Flex Test GT rock mechanics experimental system and large diameter (75 mm) split hopkinson pressure bar (SHPB), respectively. The results showed:the recycled concrete splitting tensile strength increased with the increase of gas pressure, and the gas pressure affected the recycled concrete fracture state, so it had obvious rate sensitivity; The damage state of concrete was not only assumed by the destruction of the coarse aggregate and cement mortar interface, but also was associated with the fracture damage of aggregate; Under the same water cement ratio, when the replacement percentage of coarse aggregates was 50%, the gradation of natural and recycled coarse aggregate was optimal, the splitting tensile strength was the largest.3. To study the RAC spalling properties and fracture state with various RCA replacement percentage (i.e.0%,25%,50%,75% and 100%), the dynamic spalling test of RAC was carried out using large diameter (75 mm) SHPB. The results show that the recycled concrete spalling strength increases with the increase of loading rate, and the loading rate also affects the recycled concrete fracture shape and fracture patterns, which indicates that the recycled concrete has obvious rate sensitivity. The damage state of the recycled concrete is not only the destruction of the interface between coarse aggregate and cement mortar, but also associates with the fracture damage of aggregates. Under the same water cement ratio, the gradation of natural and recycled coarse aggregate is optimal, and thus the spalling strength is closest to that of normal concrete.