Hydration, microstructure and autogenous shrinkage behaviors of cement mortars by addition of superabsorbent polymers
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RESEARCH ARTICLE
Hydration, microstructure and autogenous shrinkage behaviors of cement mortars by addition of superabsorbent polymers Beibei SUNa,b, Hao WUa,c, Weimin SONGa* , Zhe LIa, Jia YUa a
School of Civil Engineering, Central South University, Changsha 410075, China Magnel Laboratory for Concrete Research, Department of Structural Engineering, Ghent University, Ghent 9052, Belgium c National Engineering Laboratory for High Speed Railway Construction, Central South University, Changsha 410075, China b
*
Corresponding author. E-mail: [email protected]
© Higher Education Press 2020
ABSTRACT Superabsorbent Polymer (SAP) has emerged as a topic of considerable interest in recent years. The present study systematically and quantitively investigated the effect of SAP on hydration, autogenous shrinkage, mechanical properties, and microstructure of cement mortars. Influences of SAP on hydration heat and autogenous shrinkage were studied by utilizing TAM AIR technology and a non-contact autogenous shrinkage test method. Scanning Electron Microscope (SEM) was employed to assess the microstructure evolution. Although SAP decreased the peak rate of hydration heat and retarded the hydration, it significantly increased the cumulative heat, indicating SAP helps promote the hydration. Hydration promotion caused by SAP mainly occurred in the deceleration period and attenuation period. SAP can significantly mitigate the autogenous shrinkage when the content ranged from 0 to 0.5%. Microstructure characteristics showed that pores and gaps were introduced when SAP was added. The microstructure difference caused by SAP contributed to the inferior mechanical behaviors of cement mortars treated by SAP. KEYWORDS
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Superabsorbent Polymer, mechanical properties, hydration heat, autogenous shrinkage, microstructure
Introduction
With the increasing construction of large structures, the use of mass concrete is becoming more and more extensive. When a cement is hydrated, the compositions react with water to acquire stable, low-energy states. During this process, energy is released in the form of heat [1]. For concrete construction during winter, the ambient temperature may be too low to stimulate the hydration. At this time, hydration heat helps the cement hydration. While for mass concrete structures, large hydration heat may be generated and could be a great threat when the heat cannot be properly released [2]. If no effective measure is taken, the stress generated by non-uniform temperature distribution easily leads to cracks. These cracks spread rapidly and could exacerbate the severity and extent of other distress Article history: Received Aug 18, 2019; Accepted Dec 25, 2019
which leads to the performance deterioration, shortening of service period, and increase of maintenance cost. Therefore, alleviation of the early hydration heat and autogenous shrinkage of cement-based materials are critical to impede the occurrence of early distress and prolong the lifespan. Some studies revealed certain relationship existed between the hy
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