The influence of SAPs on chloride ingress in cracked concrete

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.

A review of the efficiency of self-healing concrete technologies for durable and sustainable concrete under realistic conditions

“…Concerning the role of superabsorbent polymers (SAP) in self-healing, Van Mullem et al [215] verified the chloride ingress in mortar samples with a crack width of 150 μm with and without SAPs. The healing regime of wet/dry cyles was performed for 28 days before submersion of the specimens in a chloride solution with 150 g L –1 of sodium chloride.…”

Addressing the need for standardization of test methods for self-healing concrete: an inter-laboratory study on concrete with macrocapsules

“…This study focused on self-healing mortar with macrocapsules, but the combination of the water flow test in combination with an active crack width control technique can easily be applied for other healing techniques. Due to the fast execution time, it has, for example already been applied to study the sealing efficiency of superabsorbent polymers [54] and superabsorbent polymers in combination with nanosilica [55].…”

Comparative analysis of three different types of self-healing concrete via permeability testing and a quasi-steady-state chloride migration test

“…The first method consisted of a low-head water flow test on prismatic specimens cracked in a threepoint bending test with subsequent active crack width control, because it has been identified that small changes in crack width can result in significant differences with respect to water flow through a crack [22]. To test the stability of the formed healing products at higher water pressures, a high-head water flow test (up until 2 bar) was executed on these specimens [18,23].In the second method cylindrical specimens with the different agents were cracked in a Brazilian splitting test creating specimens with a different crack geometry, i.e. cracks with a constant thickness over the height instead of the more triangular shaped cracks in the prismatic specimens.…”