Effect of projectile impact and penetration on the phase composition and microstructure of high performance concretes

Abstract

a b s t r a c tAs a result of increased concerns regarding public safety in recent years, the impact and penetration resistance of infrastructure has become an emerging research focus in the cement and concrete industry. Ultra-high performance concretes (UHPCs) with fiber reinforcement usually possess compressive strengths greater than 200 MPa and are promising candidates for penetration-resistant building materials. In the current project, two UHPC materials, ERDC-M (a modified composition developed at U.S. Army Engineer Research and Development Center) and Ductal Ò , were subjected to projectile penetration testing. The microstructural evolution due to projectile impact and penetration was examined via scanning electron microscopy and X-ray diffraction. Possible phase changes were observed in the affected material volume, which can be interpreted as resulting from the high temperature and high pressure induced by the impact and penetration.

Ballistic Impact Resistance of UHPC Plates Made with Hybrid Fibers and Low Binder Content

“…The residual strength at 2.0 mm deflection reached 16.8 MPa, which was a value 35% higher than that of the UHPC1.5 mixture. The results are in accordance with findings of Ren et al [45] who reported that fibers were more effective for increasing the amount of energy required to break these reinforced matrices. The disparity between residual strength values in this stage was due to physical and morphological modifications of the material during the tests, which triggered the reinforcement wholly at the fractured section.…”

Microscopic Change in Hardened Cement Paste due to High-Speed Impact

“…The maximum temperature indicated in Section 2.6 was lower (60°C) probably because the tip of the thermocouple was not at the surface but slightly inside, while the sample for the thermogravimetry analysis was collected from the surface. Ren et al (2013) reported that a high-temperature and high-pressure phase of SiO 2 was generated. This is probably because the speed of their projectile was faster (914 m/s) than the speed used in our study, the projectile collided with the gravel, and suppression of the rate of the temperature increase due to water evaporation was small.…”

“…This should be clarified before conducting a triaxial test to simulate the response of concrete subjected to impact. Ren et al (2013) carried out scanning electron microscope (SEM) observation and X-Ray diffraction (XRD) analysis on ultra-high performance concrete after impact by a projectile of approximately 14 g flying at 914 m/s. They reported a high-pressure and high-temperature phase of silica and pointed out that the high temperature was generated due to the impact.…”

Microscopic Change in Hardened Cement Paste Due to High-Speed Impact

“…was lower (60 °C) probably because the tip of the thermocouple was not at the surface but slightly inside, while the sample for the thermogravimetry analysis was collected from the surface. Ren et al [24] reported that a high-temperature and high-pressure phase of SiO 2 was generated. This is probably because the speed of their projectile was faster (914 m/s) than the speed used in our study, the projectile collided with the gravel, and suppression of the rate of the temperature increase due to water evaporation was small.…”