Abstract
This study investigated a technique of impregnating potential self-healing agents into lightweight aggregates (LWA) and the self-healing performance of concrete mixed with the impregnated LWA. Lightweight aggregates with a diameter range of 4–8mm were impregnated with a sodium silicate solution as a potential self-healing agent. Concrete specimens containing the impregnated LWA and control specimens were pre-cracked up to 300μm crack width at 7days. Flexural strength recovery and reduction in water sorptivity were examined. After 28days healing in water, the specimens containing the impregnated LWA showed ∼80% recovery of the pre-cracking strength, which accounts more than five times of the control specimens’ recovery. The capillary water absorption was also significantly improved; the specimens healed with the impregnated LWA showed a 50% reduction in the sorptivity index compared with the control cracked specimens and a very similar response to the control uncracked specimens. The contribution of sodium silicate in producing more calcium silicate hydrate gel was confirmed by characterisation the healing products using X-ray diffraction, Fourier transform spectroscopy, and scanning electron microscopy.
Highlights
Surface opening cracks are a common type of defects in concrete structures
The results demonstrated that the main mechanisms of self-healing are the reaction between the calcium cations and the dissolved sodium silicate and the crystallisation of the sodium silicate
The results indicated that the addition of 5% sodium silicate microcapsules by weight of cement increased the modulus of elasticity of the concrete specimens by 11% after healing
Summary
Surface opening cracks are a common type of defects in concrete structures. They allow penetration of water or other deleterious agents that result in loss of durability earlier than expected. Repairing formed cracks and defects becomes essential and unavoidable. Maintenance and repair of concrete structures generally rely on regular inspection programmes, which are expensive, and they depend on a combination of nondestructive testing (NDT) and human perception [1]. In case of severe damage, the structural component is replaced entirely while repairs are attempted for less extensive damage.
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