Abstract
Addition of superabsorbent polymers (SAPs) to cementitious mixtures promotes the self-healing ability of the material. When cracking occurs; SAPs present inside the crack will swell upon contact with water and subsequently release this water to stimulate the further hydration of unhydrated cement particles and the calcium carbonate crystallization. However; the inclusion of SAPs affects the mechanical performance of the cementitious material by the creation of macro-pores as water is retracted from the swollen SAP. To counteract the reduction in strength, part of the cement is replaced by nanosilica. In this research, different mixtures containing either SAPs or nanosilica and a combination of both were made. The samples were subjected to wet–dry cycles simulating external conditions, and the self-healing efficiency was evaluated by means of the evolution in crack width, by optical measurements, and a water permeability test. In samples containing SAPs, an immediate sealing effect was observed and visual crack closure was noticed. The smaller influence on the mechanical properties and the good healing characteristics in mixtures containing both nanosilica and SAPs are promising as a future material for use in building applications.
Highlights
Concrete is known to be highly sensitive to cracking, due to its low tensile strength, which increases the possibility of aggressive substances entering the concrete element and causing damage to both the cementitious matrix and the reinforcement material
The specimens were kept in plastic foil at a average crack widths is shown in Figure 3 for the four different testing series
The broken halves were subsequently used for measurement that was not subjected to wet–dry cycles is shown by means of a dotted line
Summary
Concrete is known to be highly sensitive to cracking, due to its low tensile strength, which increases the possibility of aggressive substances entering the concrete element and causing damage to both the cementitious matrix and the reinforcement material For this reason, the repair of concrete structures is of utmost importance and comprises around 50% of the annual construction budget in Europe [1]. The repair of concrete structures is of utmost importance and comprises around 50% of the annual construction budget in Europe [1] These high costs, combined with the fact that most repairs are only temporary solutions, lead to the introduction of self-healing concrete. In this case, Materials 2020, 13, 380; doi:10.3390/ma13020380 www.mdpi.com/journal/materials
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