Comprehensive analysis of pre-crack parameters on repeated impact strength and failure mechanism: Effects of crack depth, length, and position in engineering cementitious composites

Abstract

Assessing the impact resistance of engineering cementitious composites (ECC) is essential for applications that demand exceptional durability under impact loading conditions. The impact testing method developed by the American Concrete Institute (ACI) Committee 544 has traditionally been employed to evaluate the concrete impact resistance. However, current research predominantly focuses on uncracked specimens, with limited attention given to the effect of pre-existing cracks on the repeated impact strength and failure mechanisms. This study attempts to examine the impact of pre-crack depth, length, and location on the impact behavior of ECC specimens, utilizing ACI impact test specimens with intentionally introduced pre-cracks. This study presents an innovative approach by investigating 17 distinct pre-cracked specimen configurations, with cracks positioned at the bottom and impact loads applied to the top, where no predefined cracks are present. This unique specimen arrangement represents a significant contribution to the current research. The polypropylene fiber was used to prepare the ECC at 2 % dosage. Additionally, the impact strength was presented in terms of reliability by analysing the data dispersion using the Weibull distribution. Results indicate that increasing crack depth significantly reduces the impact strength of ECC specimens. Specifically, for a central full-length pre-crack, initial cracking and failure impact numbers decrease by up to 89.81 % and 78.00 %, respectively, as crack depth increases from 15 mm to 45 mm. This demonstrates an inverse relationship between crack depth and tensile performance, with deeper cracks impairing load distribution efficiency. Pre-crack location significantly influences impact resistance. Eccentric cracks (e.g., 50 mm from the centerline) result in smaller reductions in impact strength compared to centrally located cracks.