A study of the natural self-healing of mortars using air-flow measurements

• Published in: Materials and structures 2012-11, Vol.45 (11), p.1625-1638
• Main Authors: Gagné, R., Argouges, M.
• Format: Article
• Language: English
• Subjects: Age; Applied sciences; Building construction; Building Materials; Buildings. Public works; Carbon dioxide; Categories; Civil Engineering; Concrete structures; Concretes. Mortars. Grouts; Cracks; Engineering; Exact sciences and technology; Fracture mechanics; General (composition, classification, performance, standards, patents, etc.); Machines; Manufacturing; Materials; Materials Science; Measurements. Technique of testing; Mortars; Original Article; Processes; Simulation; Solid Mechanics; Theoretical and Applied Mechanics
• ISSN: 1359-5997; 1871-6873
• DOI: 10.1617/s11527-012-9861-y

The aim of this research is to investigate the natural self-healing of mortars using air-flow measurements through a single crack of controlled geometry. Mortars were made with water–cement (W/C) ratios of 0.35, 0.45 and 0.60. For each type of mortar, three crack categories were created: 50 ± 15, 105 ± 15 and 220 ± 35 μm. Mortars were cracked at the age of 28 days and 6 months. Cracked mortars were stored in air at 23 °C and 100 % R.H. for up to 5 months to simulate the environmental conditions for open-air above-ground concrete structures. During the first month, the kinetics of self-healing is noticeably faster. The self-healing mechanism mainly involves carbonation and the formation of secondary hydration products in the crack volume. For fine cracks (50 μm), the self-healing rate is slow (5–10 μm/month). For larger cracks (>200 μm), the self-healing rate is faster (15–30 μm/month), as there is no space limitation for the formation of self-healing products and also because the effective crack opening remains high enough for the supply of external CO 2 and water. For crack openings higher than 300 μm, the final natural self-healing level is less than 20 % after 5 months. For the mortar tested, age at the time of cracking only plays a minor role on self-healing kinetics.