Textile Reinforced Concrete in Combination with Improved Self-Healing Ability Caused by Crystalline Admixture

Abstract

The main aim of this study was to investigate the improved autogenous healing of concrete caused by a crystalline admixture in combination with textile reinforced concrete (TRC). This phenomenon (improved healing) has not yet been described by any independent study, and not at all in relation to TRC. The results of the study confirmed that the interaction between TRC and the crystalline admixture’s self-healing ability is advantageous and usable. The application of crystalline admixture could ensure the long-term entirety of the TCR element, where microcracks could occur. This allows for the creation of advantageous, thin (achieved by TRC) and waterproof (achieved by the crystalline admixtures) concrete structures. Moreover, this does not depend on temperature in the range of 4–30 °C (lower temperatures are of course problematic, as for most other cementitious materials). However, the interaction of both materials has its limits; the cracks must not be too wide (max. 0.1 mm), otherwise they will not heal. On the other hand, the advantage is that it does not matter what type of cement is used (CEM I and CEM II showed the same results), and the composition of the newly formed crystals in the cracks corresponds to the composition of the C-S-H gel, so it can be assumed that secondary hydration of the Portland cement occurred in the crack area.

The Effect of Crystalline Waterproofing Admixtures on the Self-Healing and Permeability of Concrete

“…Although it was concluded in [ 35 ] that the effect of self-healing is more pronounced in concrete with higher strength, this is not confirmed here—namely, the M-0.45-CWA and M-0.55-CWA mixes have the same number of cracks healed above 90%. It is known that cracks as small as 0.1 can be healed by autogenous healing [ 16 , 37 ]. However, considering the width of cracks healed over 90%, it can be observed that a larger number of cracks healed with a width of 0.15 mm in concrete mixes with CWA than in reference concrete mixes (3 cracks with a width of 0.15 mm healed in mixes M-0.45-CWA and M-0.55-CWA, while only 1 crack healed in mixes M-0.45-R and M-0.55-R).…”

“…As a result, the water penetration depth in concrete with incorporated CWA should be lower compared to the water penetration depth in reference concrete, which is confirmed by the authors in [ 10 , 14 ] but also disputed in [ 15 ]. As previously described, CWA also promotes self-healing of cracks [ 16 , 17 , 18 , 19 , 20 ]. The research presented in [ 18 ] implies that each CWA produces different products/crystals responsible for reducing water penetration and self-healing of concrete.…”

“…The research presented in [ 18 ] implies that each CWA produces different products/crystals responsible for reducing water penetration and self-healing of concrete. Regarding self-healing, the width of cracks that can heal completely varies in the studies; the completely healed cracks in [ 16 , 17 ] are up to 0.1 mm wide, in [ 18 ] up to 0.3 mm wide, while in the studies [ 19 , 20 ] even cracks with a width up to 0.4 mm were healed. According to [ 21 ], these admixtures are more effective in mixes with a higher water–binder ratio than in mixes with a lower water–binder ratio because higher water content in the mix promotes self-healing.…”

“…Studies dealing with water penetration of concrete under pressure either use a lower water pressure value than prescribed in the standard EN 12390-8 [ 14 , 15 , 16 , 24 ] or use a test regime with time-varying water pressure [ 20 ]. So far, only the authors in [ 10 ] have applied the water pressure prescribed in EN 12390-8 [ 25 ], but on concrete specimens cured significantly longer (90 days) than prescribed in that standard (28 days).…”

Crack Width Evaluation of Cracked Mortar Specimen Using Gas Diffusion Characteristics

“…A specimen with a specified crack width can be created in multiple ways [ 21 , 22 , 23 ]. Basically, a splitting tensile test is utilized.…”