Evaluation of Internal and Superficial Self-Healing of Cracks in Concrete with Crystalline Admixtures

Abstract

Reinforced concrete structures are prone to cracking. The development of cementitious matrices with the capacity for self-healing soon after these cracks appear represents savings with inspections and repairs of the structures. Self-healing can be stimulated with the use of crystalline admixtures. Such materials easily react with water and increase the density of C-S-H (hydrated-calcium-silicate), forming insoluble deposits blocking existing pores and cracks. In this research, self-healing in concrete cracks was evaluated using three different crystalline admixtures, submitted to two and six wetting–drying cycles. The efficiency of self-healing was evaluated by optical microscopy and using the chloride diffusion test, which allowed calculating the predicted useful life of the concretes. The results highlight two important findings: (i) in optical microscopy, crystalline admixtures were not efficient in promoting self-healing on the surface of cracks in any of the studied concretes; (ii) the passage of chlorides by diffusion was lower for concretes with crystalline admixtures compared to the reference, showing better internal healing of these materials and, consequently, greater prediction of the concrete’s useful life.

A self-healing approach to cement-based materials with crystalline admixtures in normal and accelerated environmental conditions

“…The fine aggregate used was quartz sand, with a fineness modulus equal to 1.89, ABNT NBR 7211 [15], an apparent specific mass 2.62g / cm³, and water absorption 1.30% both according to ABNT NBR 16916 [16]. The mortars mix design comes from a proportioning study conducted for other works within the Self-Healing Group / NORIE / UFRGS and are presented in Table 1 [17,18]. [20], using five specimens for each evaluated combination (four compositions, accelerated chamber and air-conditioned chamber).…”

Influence of Crystalline Admixtures and Their Synergetic Combinations with Other Constituents on Autonomous Healing in Cracked Concrete—A Review

“…Permeation (water leaking through cracks) [7,15,31,38,56] Water immersion [5,6,9,10,28,29,36,40,42,44,46,[48][49][50][51]54] Wet-dry cycles [28,36,39,51,52] Standard curing [6,44,58] Climate chamber/humidity chamber [42,45,49] Water contact [49,56] Air exposure [28,31,36,42,44,48,49] Steam curing (80 • C) [41] Water immersion (synthetic sea water) [4,55] Geothermal water immersion [45,47] Wet-dry cycles (0.545 mol/L and 2 mol/L chloride solution) [39] Wet-dry cycles (geothermal water) [45,47]…”

Preparation and Characterization of Electromagnetic-Induced Rupture Microcapsules for Self-Repairing Mortars

“…Also, internal cracks in the concrete are not easily inspected and repaired in a timely manner [ 11 ]. Therefore, the research of self-repairing materials for cracks in cement-based materials has attracted considerable attention [ 12 , 13 , 14 ].…”