Abstract
The effect of superabsorbent polymers (SAPs) on autogenous crack healing in cementitious materials with early-age cracking was investigated. SAP-containing samples exposed to wet/dry cycles showed better autogenous healing than those only exposed to wet conditions, as determined by water flow and compressive strength recovery tests. The water flow rates through cracks (380 ± 40 µm) in cement paste and cement mortar containing 1.0% SAP decreased by around 97.1–100% and 79.7–90.7%, respectively, after 14 cycles of healing compared to 1 cycle. Although the initial compressive strength decreased with SAP addition, it recovered somewhat after a 28-d healing period. Microscopy and spectroscopy results identified CaCO3 and/or calcium silicate hydrate (CSH) as the main healing products.
Highlights
Cracks in concrete frequently occur over the entire service life of the structure due to load- or deformation-induced stresses
Autogenous crack healing occurs via two main mechanisms: first, the cracks are filled by reaction products generated by further hydration of non-hydrated cement particles exposed to the crack surface [5]; and second, the cracks are gradually filled with precipitation of calcium carbonate (CaCO3 ) crystals [3]
Recent studies have used various approaches to increase the efficiency of autogenous healing of cementitious materials by facilitating further hydration, improving water-tightness, and reducing shrinkage; this includes the use of alternative binder materials, microfibers, expansive additives, crystalline additives, waterproofing admixtures, and internal curing agents [6,7,8,9,10]
Summary
Cracks in concrete frequently occur over the entire service life of the structure due to load- or deformation-induced stresses. In order to increase the service life by delaying concrete deterioration, crack repair is highly necessary. As maintenance costs increase with age of the concrete structures, there is a growing interest in self-healing methods that repair cracks autogenously without external factors. Microcracks in cementitious materials can be healed gradually in the presence of water; this process is generally referred to as autogenous healing [3,4]. Autogenous healing has great potential in durability improvement, it depends on an adequate supply of water to the cracked cementitious material [4]
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