Characterisation of autogenous healing in cracked mortars under marine water exposure

Abstract

In this study, autogenous crack healing was quantified in mortar specimens under various exposure conditions. Specimens were cracked at 28 days and then exposed to a single type of environment: submersion in freshwater, submersion in marine water or cyclic submersion in marine water followed by drying daily (tidal conditions). Instead of taking measurements at a few selected points along the crack length, crack widths were innovatively determined through periodic measurements monitoring the entire crack surface profile. This enabled the identification of significant variations in the healing profile and evidence of widening mostly due to spalling. Specimens exposed to submerged marine conditions displayed maximum overall healing and were able to completely heal a higher percentage of cracks as wide as 0.72 mm as compared to the 0.6 mm reported in previous studies. Evidence of crack widening due to spalling was found in the crack profiles, and the phenomenon was shown to be dependent on the initial width, with wider cracks showing less absolute widening. Specimens exposed to tidal conditions showed the least crack widening among all exposure conditions.

Effect of different exposure conditions on the self‐healing capacity of engineered cementitious composites with crystalline admixture

“…Liu et al 39 reported that the crack closure ratio of a 400 μm crack in seawater to be 2.6 times than of the same crack healed in tap water. The Presence of different ions dissolved in seawater, e.g., Mg 2+ , helps with the formation of new healing products such as brucite (Mg(OH) 2 ) that can promote crack healing efficiency of ECC in addition to portlandite (CA(OH) 2 ) and calcite (CaCO 3 ) 26 . These additional healing products can recover the stiffness of a cracked specimen through enhancing the fiber bond.…”

“…Although the extend of healed cracks in the presence of the moisture ranges from 50 to 150 μm, the healed crack width for seawater exposure is ranging between 200 and 700 μm. 1,12,25,26 The studies on the self-healing in ECC conclude that natural environment where cycles of moisture are available, plus maintaining the cracks width below 150 μm are favorable conditions for a robust self-healing. 17,19,20 Crystalline admixture (CA) is a market label used to categorize a group of hydrophilic admixtures containing active chemicals that form water-insoluble precipitates upon reaction with water, leading to densification of calcium-silicatehydrates (C-S-H) and resisting water penetration.…”

“…In particular, seawater exposure has reported promising results of autogenous self‐healing in cementitious materials. Although the extend of healed cracks in the presence of the moisture ranges from 50 to 150 μm, the healed crack width for seawater exposure is ranging between 200 and 700 μm 1,12,25,26 . The studies on the self‐healing in ECC conclude that natural environment where cycles of moisture are available, plus maintaining the cracks width below 150 μm are favorable conditions for a robust self‐healing 17,19,20 …”

Key Factors Determining the Self-Healing Ability of Cement-Based Composites with Mineral Additives

“…The possibility of self-healing of cracks in elements exposed to water flowing through cracks has also been confirmed [48]. The course of self-healing was also studied in conditions such as seawater action [49,50].…”