Self-healing capability of cementitious composites incorporating different supplementary cementitious materials

Abstract

a b s t r a c tThe presence of deleterious substances and their transport are among the most important factors controlling the durability of cementitious composites. The present paper studies the relationship among the applied mechanical deterioration in terms of splitting tensile deformation, curing conditions and chloride ion permeability of Engineered Cementitious Composites (ECCs) that contain different supplementary cementitious materials (SCMs). Three SCMs, representing a wide range of compositions, were used in the study. The splitting tensile deformations are introduced to generate microcracks in ECC specimens, where cylindrical specimens were pre-loaded to different deformation levels. After that, the mechanically pre-cracked and pristine ECC specimens were exposed to three different curing conditions (continuous wet, continuous air, and freeze-thaw cycle) for up to 2 months. Rapid chloride permeability test (RCPT), microscopic observation and microstructural analysis were used to assess the rate and extent of selfhealing. Test results indicate that the SCM type greatly affects the self-healing capability of cementitious composites as measured by chloride ion permeability. Although ECC samples with fly ash have more unhydrated cementitious materials, and therefore, expectedly, a higher capacity for self-healing, more evident self-healing product was observed from the ECC mixture incorporating slag. Therefore, in addition to the crack width distribution and curing condition, the reaction products associated with SCMs have a great impact on the self-healing capability of cementitious composites.

Effect of Self-Healing on the Different Transport Properties of Cementitious Composites

“…The self-healing performance of the ECC_S mixtures was surprising since it was presumed that specimens with slag would result in considerably lower amounts of anhydrous materials and higher matrix maturity along with higher total crack openings upon pre-loading. The enhanced self-healing performance of microcracked ECC_S specimens has been of issue in another study of the authors of this paper (Sahmaran et al 2013). In that study, the authors concluded that since slag particles have lower amounts of SiO 2 in their chemical compositions compared to other mineral admixtures, lower rates of pozzolanic reactions are anticipated, which would cause portlandite (as a product of cement hydration) to remain longer and in greater amounts in the cementitious matrices, leading to higher pH of the pore solution.…”

“…Just as in the sorptivity measurements, tests were repeated after 7, 30, 60 and 90 days of CW exposure beyond initial curing periods to observe selfhealing performance of ECCs. Although different crack characteristics were acquired with the application of pre-loading to ECCs with different mineral admixtures (MAs), the effect of self-healing on crack recoveries has not been accounted for in this study since this point has already been investigated in detail in several previous papers (Sahmaran et al 2013(Sahmaran et al , 2014.…”

Self-repairing properties of OPC clinker/natural zeolite blend in water and alkali carbonate environments at 270°C

“…Among the major technical strategies for developing self-healing cements, autogenous healing relies on the hydration of residual non-hydrated and partially hydrated cement particles by permeation of water through cracks and the carbonation of hydrates with crack plugging by the hydration and carbonation reaction products (Edvardsen, 1999;Huang et al, 2013;Talaiekhozan et al, 2014). Another, autogenous healing approach involves the incorporation of pozzolan-latent cementitious materials such as fly ash (Sahmaran et al, 2008(Sahmaran et al, , 2013Termkhajornkit et al, 2009), ground granulated blast-furnace slag (GBFS) (Huang et al, 2014) and silica fume (Qian et al, 2010) as healing aids into cements. In contact with calcium-and sodium-containing alkaline fluids penetrating through the fractures, these nonreacted pozzolan materials form amorphous and crystalline calcium silicate, calcium aluminosilicate, sodium aluminosilicate and calcium(sodium) aluminosilicate products, which seal the cracks.…”

Effects of autogenous healing on the recovery of mechanical performance of High Performance Fibre Reinforced Cementitious Composites (HPFRCCs): Part 1

“…Moreover, water does not only promote further hydration of cement and binder grains but may also encourage the dissolution and leaching of calcium hydroxide from the cementitious matrix to form calcium carbonate self-healing crystals with the carbon dioxide dissolved in water [7]. Different supplementary cementitious materials, such as fly ash (class C or F) and slag, also play different role in enhancing the self-healing capacity [8], thanks to their delayed reaction, guaranteeing the repeatability and persistence of the same capacity upon repeated cracking-healing cycles [9].…”