POLYMERS AND POLYMER MATRIX COMPOSITES |
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Influence of SAP Type on Early-crack Resistance and Drying Shrinkage Performance of Cement Mortar |
WANG Ke1, HU Yuanyuan2, HE Rui1,*, ZHENG Suining1, ZHAO Jian2
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1 School of Materials Science and Engineering, Chang'an University, Xi'an 710061, China 2 Yaobai Special Cement Technology R&D Co., Ltd., Xi'an 710100, China |
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Abstract The absorbent properties of two different types of super absorbent polymer (SAP) (sodium acrylate and composite type of polymer) were studied, and the stable water loss rate was proposed as the evaluation index of SAP's water absorption dynamic behavior in cement pastes. The working performance of the modified cement mortar and its early anti-cracking and mechanical properties under different environments (standard curing environment and natural environment) were evaluated. SEM and XRD were adopted to explore the its micro modification mechanism. The results indicate that the absorption of SAP in saturated Ca(OH)2 solution exhibits a law of rapid increase, gradual decrease, and final stability. SAP can reduce the initial fluidity of cement mortar. At the same time, it can significantly alleviate the loss of fluidity of cement mortar with time. The addition of SAP can reduce the dry shrinkage of cement mortar and inhibit the formation and germination of early cracks in cement mortar panels. Both types of SAP can improve the early mechanical properties of cement mortar (before 7 d). Still, sodium acrylate type of polymer harms the mechanical properties of cement mortar at 28 d. The standard curing environment and the addition of SAP are conducive to the formation of AFt, C-S-H and CH. The hydration degree of cement is higher after SAP incorporation. The water release process of sodium acrylate type of polymer in the plastic stage of cement mortar is not conducive to the development of the microstructure of cement mortar. At the same time, a layer of inorganic-organic film is formed on the pore wall of the composite type of polymer after water release, which is conducive to reducing the negative effect of pores on cement mortar.
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Published: 10 December 2023
Online: 2023-12-08
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Fund:National Natural Science Foundation of China (52278429), the Key Research and Development Program of Shaanxi Province (2022GY-422), Transportation Science and Techno-logy Project of Shaanxi Province (20-16K, 21-50K), Fundamental Research Funds for the Central Universities, Chang'an University (300102312402). |
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