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为了解决道路工程中水泥混凝土易出现的早期收缩开裂、抗冻性差等耐久性问题,采用温度敏感性水凝胶(PNIPAm)作为水泥砂浆的内养护剂,分别研究了不同吸水率、不同掺量PNIPAm对水泥砂浆的工作性能、力学特性以及韧性(折压比)的影响;采用平板法测试了水泥砂浆的早期抗裂性,根据冻融循环快冻法测试了水泥砂浆的抗冻性;利用扫描电子显微镜观察了PNIPAm改性水泥砂浆硬化体的微观结构,并采用压汞法定量测试了PNIPAm改性水泥砂浆的内部孔结构,最后分析了PNIPAm对水泥砂浆的改性机理。结果表明:PNIPAm改善了水泥砂浆的工作性能、抗折强度以及韧性,随着PNIPAm含量的升高,水泥砂浆的抗压强度略有下降;随着水泥水化的进行,水泥砂浆体系中的PNIPAm逐渐融合成薄膜网状结构,这种结构可以有效地分散水泥砂浆内部裂纹的尖端应力,降低水泥砂浆的开裂面积,延长水泥砂浆的开裂时间;PNIPAm释放的水分子对水泥砂浆起到了内养护的作用,使其无害孔含量提高,有害孔含量降低,PNIPAm的掺入有效提高了水泥砂浆的抗冻性能;综合PNIPAm对水泥砂浆强度、抗冻以及抗裂性能的影响,PNIPAm的掺量建议为水泥砂浆总质量的0.5%~0.75%。
In order to solve the durability problems of early shrinkage cracking and poor frost resistance prone to cement concrete in road engineering, temperature-sensitive hydrogel (PNIPAm) was used as internal curing agent for cement mortar. The effects of different water absorption, different dosage PNIPAm on the performance of cement mortar, mechanical properties and toughness (pressure ratio); using mortar test of early mortar anti-cracking, freeze-thaw cycles according to freeze-thaw test of cement mortar frost resistance; use of The microstructure of PNIPAm modified cement mortar was observed by scanning electron microscope. The pore structure of PNIPAm modified cement mortar was quantitatively measured by mercury intrusion porosimetry. Finally, the modification mechanism of PNIPAm to cement mortar was analyzed. The results show that PNIPAm can improve the workability, flexural strength and toughness of cement mortar. As the content of PNIPAm increases, the compressive strength of cement mortar decreases slightly. With the hydration of cement, the PNIPAm Gradually merge into a thin film network structure, this structure can effectively disperse the tip stress of the internal cracks in cement mortar, reduce the cracking area of cement mortar, extend the cracking time of cement mortar; PNIPAm released water molecules play an internal conservation of cement mortar The content of harmless pores is increased and the content of harmful holes is decreased. The incorporation of PNIPAm effectively improves the frost resistance of cement mortar. Based on the influence of PNIPAm on the strength, frost resistance and crack resistance of cement mortar, the content of PNIPAm The total mass of cement mortar 0.5% to 0.75%.