Sustainable High-Ductility Concrete with Rapid Self-Healing Characteristic by Adding Magnesium Oxide and Superabsorbent Polymer

Pengfei Liu,Jun Yang,Quan Liu,Guoyang Lu,Shuyin Wu

doi:10.1155/2020/5395602

Abstract

As a class of high-ductility concrete, engineered cementitious composites (ECC) have wide application prospects in engineering fields. However, the occurrence of cracks and the limited self-healing ability hinder the development of ECC. Rapid self-healing has important significance for ECC in reducing maintenance costs and prolonging service life, which are conducive to sustainable development of ECC. Therefore, the aim of this paper is to enhance the self-healing property of ECC by adding light-burned magnesium oxide (MgO) and superabsorbent polymer (SAP) on the premise of maintaining the high ductility. First, the effect of MgO and SAP on the ductility property of ECC which is the most important feature was explored with the uniaxial tensile test. The results indicated that MgO is helpful to the strength but not conducive to the ductility of ECC, while SAP has an opposite effect. The effects of MgO and SAP on the ductility of ECC can be balanced. Later, the permeability test, scanning electron microscopy (SEM), and X-ray diffraction (XRD) were used to evaluate the effects of MgO and SAP on the self-healing property of ECC. The results showed that the combined addition of MgO and SAP shows much better effect than the individual addition and can cut the healing time by half. Overall, it is concluded that ECC with MgO and SAP have the potential for self-healing, and the ductility can also be reconciled.

Highlights

Engineered cementitious composites (ECC) are a typical kind of high-ductility cementitious composites (HDCC).e ultimate tensile strain of ECC can be above 3%, which is 300 times larger than that of the ordinary cement concrete, and the crack width in a saturated state is below 100 μm [1,2,3]
As can be seen from the figure, Magnesium oxide (MgO) and Superabsorbent polymer (SAP) do have an impact on the ductility of ECC. e order for ECC with different mix proportions based on ductility was ECC containing SAP, ordinary ECC, ECC containing MgO and SAP, and ECC containing MgO
Ese above changes are directly related to the changes of MgO and SAP. e hydration of MgO produces Mg(OH)2, as shown in Figure 7. e formation and growth of Mg(OH)2 crystals will cause expansion and make ECC denser, which is helpful to the strength but not conducive to the ductility. us, ECC containing MgO has larger strength and smaller deformation than ordinary ECC

Summary

Introduction

Engineered cementitious composites (ECC) are a typical kind of high-ductility cementitious composites (HDCC).e ultimate tensile strain of ECC can be above 3%, which is 300 times larger than that of the ordinary cement concrete, and the crack width in a saturated state is below 100 μm [1,2,3]. Cracks may occur in ECC due to the action of loading and environment, which weaken the mechanical properties and cause moisture damage. E unhydrated or insufficiently hydrated materials at the damaged part of cement-based materials tend to hydrate further and produce products to heal a crack, which is known as self-healing behavior [10]. Huang et al [11] pointed out that the early self-healing of cement-based materials is mainly realized by hydration of unhydrated cement. Lauer and Slate [12] investigated the effect of humidity on the self-healing behavior of cement-based materials and found that 95% relative humidity induces the fastest self-healing rate. Fang et al [14] concluded that Ca2+ distributed in cement-based materials and CO32− dissolved in water form CaCO3 crystals, which conduce to crack self-healing of cement-

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Conclusion