Crack sealing capacity in chloride-rich environments of mortars containing different cement substitutes and crystalline admixtures

Abstract

This paper presents the results of a preliminary study aimed at assessing the crack sealing capacity in chloride environments of different concrete mixtures, incorporating supplementary cementitious materials as well as self healing enhancing crystalline admixtures. For each addition, also including pulverized fuel ash and silica fume, different contents were taken into consideration. Cylinder specimens were pre-cracked in splitting up to three different crack opening ranges, simulating different service conditions, and then exposed to different conditioning environments, also containing different concentrations of sodium chloride and including both permanent immersion and wet/dry cycles. Healing conditioning was performed up to three months and crack sealing was visually inspected, and quantified via image analysis procedures, monthly. Optimum dosages of each cement substitute/addition were quantified, also considering, besides the healing capacity, also the fresh state performance and compressive strength development. The good performance of mixes with crystalline admixture even under open air exposure, as well as of other investigated mixes as above with reference to crack openings and exposure conditions, paves the way to revise the significance of a serviceability design parameter such as the maximum allowable crack width as a function of the exposure with the concept of a sealable crack width.

A Review of Self‐Healing Concrete for Damage Management of Structures

“…Improved performance under exposure to artificially replicated seawater (both submersion and wet–dry cycles) was also reported by Borg et al as well as by Cuenca et al who also hypothesized a contribution of crystalline admixtures to chloride binding.…”

Crystalline Admixture as Healing Promoter in Concrete Exposed to Chloride-Rich Environments: Experimental Study

“…For instance, for a specimen without crystalline admixtures immersed in 16.5% NaCl solution with a chloride content of 0.51%, 0.75%, and 0.85% were detected after 1, 3, and 6 months of exposure time, respectively. According to previous studies (Guinee et al 2011;Borg et al 2018), it is well-known that the chloride ingress close to the exposed surface is usually not diffusion controlled, indeed is part of the convection zone. In fact, some researchers have detected an increased calcium leaching on the surface in contact with the exposure solution that results into a reduction of the chloride binding capacity (Álava et al 2016;Elakneswaran et al 2010).…”

“…It was observed that self-healing led to a reduction of chloride content for both mixes, but the chloride content in the specimens having the self-healing agent was lower. Borg et al (2018) studied the crack sealing capacity of mortars containing supplementary cementitious materials (fuel ash and silica fume) or crystalline admixture (same as used in this research) in chloriderich environments. They observed that sea water may lead to an enhancement of the self-healing capacity of mortars with respect to distilled water, especially for higher chloride contents (16.5% NaCl aqueous solution).…”

Use of Secondary Crystallization and Fly Ash in Waterproofing Materials to Increase Concrete Resistance to Aggressive Gases and Liquids

“…Research on secondary crystallization in cement composites has previously been dealing with the sealing of pore structures and sealing cracks. e benefits of utilisation of crystalline admixtures are well demonstrated in previously published studies [25][26][27][28][29][30]: however, improving the properties of concrete remains an important task even today [19]. Improving the durability of cementitious composites helps extend their longevity, thereby reducing repair costs associated with moisture damage of concrete structures [31].…”