Mechanical properties and crushing mechanism of axially carbonated mortar under impact loading

To research the mechanical damage and failure mechanism of axially carbonated mortar under impact loading, dynamic uniaxial compression tests are used on specimens of different carbonization ages using a Hopkinson compression bar (SHPB) test apparatus. The effects of impact pressure and carbonation age on the longitudinal wave velocity, peak stress, energy dissipation, fractal dimension and fracture morphology of mortar materials are obtained. The failure mechanism of axially carbonized mortar is revealed. The results show that at the same carbonization age, the peak stress increases with gradually increasing impact pressure, and the strain rate effect is obvious. Under 0.65 MPa impact load, the peak stress of the values of the compressive strength of carbonated specimens for ages 3 d∼28 d are 4.97∼34.79% higher than those of the uncarbonated specimens. Carbonization increases the longitudinal wave velocity and peak stress. With increasing impact air pressure and carbonation age. the crushing energy density of mortar material increases, and although the increase significantly decreases. Carbonization reduces the fractal dimension of the specimen and enhances the deformation resistance of the specimen under an external load. With increasing "carbonization reinforcement layer" effect and decreasing impact air pressure, the failure mode of the specimen gradually changes from crushing failure to splitting tensile failure, and the degree of fragmentation decreases.