156 / 2022-04-29 20:55:09

Effect of superabsorbent polymer on self-healing performance of fly ash-cement systems

Superabsorbent polymer,Fly ash-cement systems,Self-healing performance

To achieve practical autonomous healing in construction, an approach that uses superabsorbent polymer (SAP) has been proposed. SAP is a cost-effective, durable, and resilient material that can absorb large amounts of water and then expand into an impermeable gel. The application of supplementary cementitious represented by fly ash to the self-healing of concrete is a feature of many sustainable structures because it reduces maintenance costs and extends service life. The effect of SAP on the self-healing performance of fly ash-cement systems and its potential application in different environments is not well understood (Fig.1). The purpose of this study is to explore the possibility of SAP in the treatment of fly-ash cement systems (Fig.2).



Many self-healing studies have shown that concrete requires extensive exposure to water to promote crack sealing. This study was based on the good water absorption characteristics of SAP, which can absorb water from a certain humidity environment to promote the healing of cracks, the hygroscopicity of SAP was tested by self-made static water vapor adsorption apparatus (Fig.3). As SAP with different particle sizes has different water absorption capacities, the larger the particle size is, the more water it absorbs (Fig.4). Therefore, three different exposure conditions were considered in this study, such as curing in the air (33%RH), wet-dry cycling in water and saturated calcium hydroxide solution, 97%RH. SAP with three-particle sizes (Fig.5) was adopted as the research object.

                                                                                      

Through fluidity test and compressive strength test, the feasible mix ratio design was studied, and the self-healing performance of concrete mixed with SAP and fly ash was analyzed and evaluated through physical properties, mainly including mechanical properties recovery experiment, crack closure experiment and capillary water absorption experiment (Fig.6). In addition to thermogravimetric analysis. The self-healing products were analyzed by XRD and FTIR, and the newly formed self-healing materials were analyzed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS).



The results showed that SAP can significantly improve the mid-term self-healing ability of the fly ash-cement system. With the increase of SAP particle size and content, the self-healing effect of SAP on fly ash-cement system was enhanced. The self-healing effects were sorted by saturated calcium hydroxide solution＞tap water ＞97%RH＞air. Crack closure was related to the development of self-healing products such as calcium carbonate C-S-H.