Abstract
Super Absorbent Polymers (SAPs) have proven to be effective as a self-healing agent for regaining the liquid tightness of cracked concrete. This is due to their large swelling capacity which allows them to (partially) block cracks which are in contact with water or moisture. Additionally, they are able to release this water when the climate becomes drier, thereby promoting the autogenous healing capacity of the concrete matrix. The effect SAPs have on chloride migration into cracked concrete is still unknown. The swelling capacity of the SAPs might partially block the crack, but this does not necessarily mean that the chloride ingress into the crack is lower. Especially, since the porosity of concrete with SAPs is slightly higher when additional water is added to compensate for the loss in workability. This paper compares the chloride ingress in cracked mortar with and without SAPs. The specimens were saturated in a chloride solution during 1 or 5 weeks after which the chloride ingress could be visualised using silver nitrate. The specimens which healed prior to chloride saturation had a significantly lower chloride ingress. The SAPs were able to delay the chloride ingress, as well as limit the influence of the crack on the chloride ingress.
Highlights
Concrete is a brittle material with a low tensile strength
The effect of the SAPs is more clearly visible when comparing the sealing efficiency after 14 wet-dry cycles SE14 W/D: 89.9% for SAP against 48.9% for reference mortar (REF). These results show that the mortar containing SAPs can seal its cracks which are subjected to wet-dry cycles quicker than the REF mortar
Up until a water pressure of 1 bar the sealing of SAP specimens is better than the sealing of REF specimens, but at a water pressure of 2 bar healing products and SAP particles are pushed out;
Summary
Concrete is a brittle material with a low tensile strength. Cracks can be the result of the structure being subjected to shear, bending, tension or torsion resulting from either direct loading or restrained or imposed deformations. Cracks can be formed due to e.g. plastic shrinkage and expansive action of corroding steel. The formed cracks are a preferential pathway for the ingress of harmful substances, especially chloride ions. Cracks often cross the structural tensile reinforcement, and in consequence chloride ions can reach the steel reinforcement directly, immediately starting chloride induced corrosion
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