Projectile impact resistance of corundum aggregated UHP-SFRC

• UHP-CASFRC was prepared under common curing temperature and pressure procedures.
• Influences of coarse aggregates on static strengths and projectile impact resistance were experimentally studied.
• UHP-CASFRC was validated having superior projectile impact resistance than UHP-BASFRC and HSC.
• UHP-CASFRC with the corundum sizes ≥1.5d was suggested for the constructions of protective structures.
• Mass loss and DOP of the ogive-nosed projectile penetrating into UHP-CASFRC target were analyzed.

The ultra-high performance steel fiber reinforced concrete (UHP-SFRC) with the corundum coarse aggregate (UHP-CASFRC) was prepared under common curing temperature and pressure procedures. The static tests on UHP-CASFRC were conducted, including the uniaxial compression, direct tensile and four points bending tests. Totally 16 shots of reduce-scaled projectile penetration tests on UHP-CASFRC and 2 comparative shots on HSC targets were conducted. The influences of the strength (hardness), size and volumetric ratio of coarse aggregate, incident velocity of the projectile (510–850 m/s) as well as the repeated strikes on the depth of penetration (DOP), area and volume of the impact crater, as well as the structural integrity and mass loss of the projectile were discussed.By comparisons with the previous conducted basalt aggregated UHP-SFRC (UHP-BASFRC), the superior projectile impact resistance of UHP-CASFRC targets was verified. Within the discussed parametric variation ranges, it derived that: (i) Enlarging the size of the coarse aggregates can help reducing the DOP, impact crater area and volume, the harder coarse aggregate can decreasing the DOP by aggravating the mass abrasions of the projectile. The influences of coarse aggregate hardness on impact crater area and volume mainly depends on its surface roughness; (ii) When the sizes of the coarse aggregates were less than the projectile shank diameter (d), the harder coarse aggregates only aggravates the mass abrasions of the projectile, while the structural integrity of projectile could be maintained; (iii) For UHP-CASFRC target, the structural destruction of the projectile occurred when the coarse aggregates sizes increasing larger than d. From a structure protective point of view, the corundum sizes ≥1.5d is suggested; (iv) The hardness of the coarse aggregate is the most influential factor on the mass abrasion of the projectile, and the previously proposed engineering models for mass abrasions of the ogive-nosed projectile high-speed penetrating into concrete target are further validated.