Distribution and curing kinetics of waterborne epoxy resin in repair system: Characterization and quantification by 1H low-field NMR

Abstract

Cement-based mortars are commonly modified with Waterborne Epoxy Resin (WER). However, the curing kinetics of WER in mortars has never been quantified up to now. This study proposed using 1H low-field nuclear magnetic resonance (1H LF-NMR) to quantitatively determine the curing kinetics of WER in polymer-cement composite. The distribution and curing of WER in repair systems was also explored using 1H LF-NMR. To avoid the interference of the NMR water signal, heavy water was used to prepare repair mortar. It was found that the curing reaction of WER in a mortar was significantly influenced by the cement hydration. It starts to accelerate when the cement hydration stepped into an acceleration period. Moreover, the 1D spatial NMR signal distribution showed that WER in the repair materials permeated into the substrate with water, which is affected by both the W/C of the repair and the RH of the substrate. The WER was enriched at the interface between the substrate and the repair mortar and exhibited a gradient in the distribution both upwards into the repair mortar and downwards into the substrate.