Evaluation of the Self-Healing Ability of Mortar Mixtures Containing Superabsorbent Polymers and Nanosilica

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.

Influence of Environmental Factors on the Swelling Capacities of Superabsorbent Polymers Used in Concrete

“…Additionally, for acrylate-based SAP the degree of swelling also depends on the pH value of the solvent [ 19 , 20 ]. The benefit of using SAPs for cementitious materials arises from the fact that the polymer-bound water can slowly be released into a drying environment [ 21 ]. For example, modern ultra-high-performance concrete (UHPC) relies on rather low water-to-cement ( w / c ) ratios.…”

The Contribution of Elastic Wave NDT to the Characterization of Modern Cementitious Media

“…In the following section, the aforementioned elastic wave techniques are used for monitoring of all stages of the materials' life. Focus is given on the NDT aspect of the study, while preliminary results concerning the material properties have been recently published [21].…”

“…A side and bottom view of the specimens with metal framework can be seen in Figure 3a,b, respectively. A more detailed explanation on the experimental testing procedure and the results can be found in [21]. specimen, following the procedure described in [43].…”

“…A side and bottom view of the specimens with metal framework can be seen in Figure 3a,b, respectively. A more detailed explanation on the experimental testing procedure and the results can be found in [21]. For the further examination of healing by means of mechanical loading and reloading, although the sensors and excitation remained the same, the specimens' geometry was slightly modified (crosssection of 30 mm × 30 mm, and length of 360 mm) and a thin steel rebar of 6 mm diameter and a length of 700 mm was embedded at casting [44].…”

“…The further hydration is promoted by nearly 40% compared to the reference cementitious material [17], and can even be repeated for a second healing cycle [18]. The healing characteristic is an interesting feature and requires high amounts (1 m% of binder) of SAPs to be added, although detrimental for the mechanical properties [19,20], which can be counteracted by the addition of NS [21].…”