Designing Repeatable Self-Healing into Cementitious Materials

Abstract

Designing self-healing into cementitious materials can open a new world of opportunities for resilient concrete infrastructure under service loading conditions. The self-healing process should be robust as well as repeatable, allowing for self-repair after multiple damage events. The repeatability poses great challenges when self-healing strategies mainly rely on the formation of low-strength calcium carbonate healing product, complicated by the localized cracking behavior of cementitious materials. This study aims at formulating a new cementitious material system with designed physical and chemical characteristics that favour repeatable self-healing. Advanced experimental methods, coupled with micromechanics theory, are adopted to probe and design repeatable self-healing into cementitious materials.

A methodology to assess crack-sealing effectiveness of crystalline admixtures under repeated cracking-healing cycles

“…Subsequently, the next step would be to analyze if the sealing mechanism is maintained over time after several cracking-healing cycles (self-healing repeatability). Compared to the large number of investigations on self-healing [6,7,10,11,18,19,20,9] among others, studies on the persistence of the healing capacity under repeated cracking and healing events of self-healing FRCC are less numerous [22,[39][40][41][42] which has motivated this research. Among the cited studies on the persistence of the healing capacity under repeated cracking events, it is worth recalling the works by Snoeck et al [22] and Sahmaran et al [39].…”

Self‐healing of engineered cementitious composites under reversed and sustained loading conditions

“…Generally, pre‐cracking is a force/displacement‐controlled test in which the specimen is cracked up to a specific percentage of its ultimate force/displacement capacity. After testing six dummy specimens under four‐point bending test, it was observed that the continuation of postlinear behavior (deflection‐hardening stage) is highly dependent on the weak point of cracking, crack propagation pattern and the fiber orientation and dispersion at the crack locations 24,35 . Therefore, in this study the specimens were precracked up to a point where a visually distinguishable crack (which was measured by DIC to be between 200 and250 μm, after unloading) was observed on the specimens.…”

“…Using precracking results of ECC prisms to determine the compression cycle load limit hardening stage) is highly dependent on the weak point of cracking, crack propagation pattern and the fiber orientation and dispersion at the crack locations. 24,35 Therefore, in this study the specimens were precracked up to a point where a visually distinguishable crack (which was measured by DIC to be between 200 and250 μm, after unloading) was observed on the specimens. This high deflection was selected purposefully so that fibers between cracks will not be able to interfere with the UPV measurements.…”

“…23 To help obtain a repeatable self-healing mechanism in concrete, a set of physical, chemical and environmental conditions are suggested. 24 Fibers that bridge the cracks to control the damage, high unreacted ingredients that promote the formation of materials such as calcium silicate hydrate (C-S-H) or strong crystals, and presence of moisture in the surrounding environment are suggested to be most effective. [25][26][27][28][29][30] Engineered cementitious composite (ECC) that possesses two-third of the aforementioned properties, has been of high interest to researchers for its repeatability properties.…”

“…The repeatability of a self‐healing mechanism is also a crucial asset for justifying the life cycle cost of a self‐healing mechanisms for industry 23 . To help obtain a repeatable self‐healing mechanism in concrete, a set of physical, chemical and environmental conditions are suggested 24 . Fibers that bridge the cracks to control the damage, high unreacted ingredients that promote the formation of materials such as calcium silicate hydrate (C–S–H) or strong crystals, and presence of moisture in the surrounding environment are suggested to be most effective 25–30 …”