Research On Dynamic And Static Mechanical Properties Of Coral Aggregate Seawater Concrete

Since the implementation of the“Ocean Power”strategy,the development of the South China Sea Islands and the construction of infrastructure and protection projects have accelerated.The preparation of high-strength and high-toughness coral aggregate seawater concrete has important practical significance for island reef construction,restoration of concrete engineering and military protection engineering.In this paper,three sets of strength grade coral seawater concrete?CASC?,three sets of sisal fiber coral aggregate seawater concrete?SFCASC?and one group of ordinary portland concrete?OPC?were designed,by measuring its basic mechanical properties,quasi-static and dynamic impact mechanical properties,studied the influence of strength grade and sisal fiber on the static and dynamic mechanical properties of CASC,and finally used LS-DYNA to impact mechanical properties.Numerical simulations were performed.The main conclusions of the full text are as follows:1.The basic mechanical properties such as compressive strength,tensile strength and axial tensile strength of CASC and SFCASC were tested.The experimental results show that CASC of C30,C50and C70 have the strength level of sisal fiber.When it is 3 kg/m³,the compressive strength of CASC cube increases by 8.0%¹5.5%,and the tensile strength increases by 7.3%⁴5.4%;2.The uniaxial tensile test was carried out on the CASC cylinder specimen,and the uniaxial tensile stress-strain curve was obtained.The results show that the axial tensile strength of SFCASC is 7.5%,6.6%,and 6.5%higher than that of CASC.The tensile modulus Ec of SFCASC is 11.2%,10.7%,and8.0%higher than that of CASC.The CASC and SFCASC of the C50 intensity grade were 22.4%and14.2%lower than the Ec of the OPC,respectively.The CASC tensile E_c is 36.2%,36.8%,and 26.4%higher than the compressed E_c.The tensile E_c of SFCASC is 90.9%,41.9%,and 27.3%higher than that of the compressed E_c,and the axial tensile strength and cleaving of CASC and SFCASC are established respectively.The relationship between tensile strength,axial tensile strength and cubic compressive strength,axial tensile strength and elastic modulus;3.The uniaxial compression test of the CASC prism specimen was carried out,and the axial compressive strength and the uniaxial compressive stress-strain curve were obtained.The results show that there is a significant linear relationship between the axial compressive strength of CASC and the compressive strength of cubic.The sisal fiber not only has a reinforcing effect,but also has obvious toughening effect,which can improve the brittleness of CASC and reduce the stress-strain curve.The residual stress at the stage is higher than that of CASC and lightweight aggregate concrete;4.The impact compression test of CASC and SFCASC was carried out by using the split Hopkinson pressure bar.The results show that the CASC impact compression has obvious strain rate effect,and the dynamic enhancement factor DIF has a linear relationship with the logarithm of the strain rate;the CASC toughness index has a linear relationship with the strain rate,and the sisal fiber has a significant dynamic increase for the CASC of the medium and low intensity grades?C30^C50?.The toughness effect does not have dynamic toughening effect on high-strength CASC?C70?;the sensitivity of SFCASC to variability is higher than that of CASC and OPC,and the strength increase value is larger under the same strain rate,and the strain rate is 50 s^-1160s^-1.Within the range of strain rate,the DIF of CASC increases with strain rate greater than OPC;5.LS-DYNA is used to simulate the C50 intensity class under 78 s^-11 and 101 s^-1 conditions.The parameter values and commissioning results measured by static test determine the 21 parameter values of HJC.And the actual failure mode of the test piece is compared with the simulated failure mode and the measured stress and strain value.The two are in good agreement,indicating that the simulation has high reliability;6.Using the split Hopkinson pressure bar to carry out the impact pull test of CASC and SFCASC,using the DIF calculation formula recommended by the European Concrete Committee to fit the relationship between the impact pull DIF and the strain rate;When the coupling failure of the tension and compression occurs,the strain rate is the upper limit of the critical strain rate of the impact pull,and the stress value exceeding the upper limit is not considered as the stress of the impact pull;7.The direct tensile test of CASC and SFCASC was carried out by using the split Hopkinson rod.The results show that the sensitivity of SFCASC to variability is the highest,and the impact toughness index??SFCASC?>??OPC?>??CASC?.The DIF calculation formula recommended by the European Concrete Committee is used to fit the relationship between the DIF and the strain rate of the impact shaft.By comparing the advantages and disadvantages of the impact pull and the impact shaft pull test,the impact pull DIF and the impact shaft pull are established.The conversion relationship of DIF,and the relationship between impact compression DIF,impact pull DIF and impact direct stretch DIF.