Effect of steam curing temperature on performance of high ductility cementitious composites (Part I: Modified fiber bridging model, performance and mechanism)

The preparation of High Ductility Cementitious Composite (HDCC) necessitates ample low-reactive mineral admixtures. Steam curing activates their pozzolanic reaction, swiftly yielding HDCC with requisite mechanical properties, thereby reducing production cycles. Prefabricated components facilitate controlled HDCC performance and mitigate on-site construction pollution. However, HDCC steam curing systems lack uniform selection and related standards. This paper investigates the effect of steam curing temperature on low and medium strength grade (C30-C50) HDCC engineering applications. It addresses the impact of steaming temperature on fiber bridging ability by modifying the fiber bridging model. Additionally, it employs the modified micro- mechanical model to analyze the evolution of the strain-hardening index. As curing temperature increases, matrix initial cracking strength and interfacial friction strength rise, with uneven hydration product distribution, heightened porosity, and increased defects. Concurrently, fiber tensile strength decreases, weakening interfacial bonding and fiber bridging capacity, hindering strain hardening and multiple cracking ability. Specifically, the number and width of cracks decreases from 25 cracks, 146.6 mu m at 60 degrees C to 5 cracks, 16.9 mu m at 90 degrees C, and tensile ductility declines from 4.3 % to 1.0 %. It is advisable not to exceed a curing temperature of 60 degrees C for PVAHDCC. This study provides insights into the evolution of HDCC properties under steam curing conditions and informs the selection of steam curing regimes for HDCC, offering valuable application guidance.