Role of Chemical Bonding on Durability of Epoxy Adhesion to Mortar

这笔赠款提供资金，用于研究环氧树脂与水泥浆体或砂浆界面的化学作用，以及水对这些作用的影响。在已知的水泥浆体表面化学的基础上，类比于环氧树脂与铝的粘接，我们提出了环氧树脂与水泥浆体形成氢键的观点。在水的存在下，这些水-水泥浆体键被水分子取代，导致界面弱化。我们建议通过光谱测量和机械测量相结合的方法来检验这一假设。使用X射线光电子能谱(XPS)和衰减全反射红外光谱(ATR-IR)对环氧树脂、水泥浆体和砂浆的表面化学进行鉴定。两者之间的结合将通过在水泥浆体或砂浆上涂上一层薄薄的环氧涂层，并用XPS和ATR-IR识别结合来识别。氢键的作用将通过修饰表面来改变表面氢键的浓度，并通过XPS和ATR-IR光谱的定量分析来量化。水的影响将在30、40、50或60摄氏度下浸泡长达12周的样品上使用光谱和机械测量来确定。直接拉伸拉拔试验将被用来测量粘结强度随浸泡和表面处理的变化，并与XPS和ATR-IR观察到的粘结变化相关联。该项目将为环氧树脂和水泥浆体之间的粘合以及环境暴露如何影响粘合和所产生的性能提供新的见解。该项目的主要目标是提供所需的基础科学，以了解这些材料在实际应用中的行为。这一结果可用于开发改进的老化模型，用于预测环氧树脂与水泥粘结的体系的寿命。它还可以为开发性能更好、寿命更长的新材料提供指导。

This grant provides funding to investigate the chemical interactions at the interface between epoxy and cement paste or mortar, and the effect of water on those interactions. Based on what is known about the surface chemistry of cement paste, and by analogy with epoxy adhesion to aluminum, we propose that epoxy forms hydrogen bonds with cement paste. In the presence of water, these water-cement paste bonds are displaced by the water molecules, leading to a weakening of the interface. We propose to test this hypothesis through a combination of spectroscopic and mechanical measurements. The surface chemistry of epoxy, cement paste, and mortar will be identified using x-ray photoelectron spectroscopy (XPS) and attenuated total reflection infrared spectroscopy (ATR-IR). Bonding between the two will be identified by placing a thin epoxy coating on the cement paste or mortar and identifying the bonds with XPS and ATR-IR. The role of hydrogen bonds will be quantified by modifying the surfaces to change the surface concentration of hydrogen bonds and by quantitative analysis of the XPS and ATR-IR spectra. The effect of water will be identified using both spectroscopic and mechanical measurements on specimens that have been immersed at 30, 40, 50, or 60 C for up to 12 weeks. Direct tension pull-off tests will be used to measure changes in bond strength as a function of immersion and surface treatment and correlated to the changes in bonding observed with XPS and ATR-IR.This project will provide new insights into the adhesion between epoxy and cement paste and how environmental exposure affects that adhesion and the resulting properties. The primary objective of the project is to provide the fundamental science needed to understand the behavior of these materials when used in real-world applications. The results may be used to develop improved models of aging for lifetime prediction of systems in which epoxy is bonded to cement. It may also provide guidance for developing new materials with improved performance and lifetime.