In-situ μ-XCT characterization of cement-waterborne epoxy resin coalescence

Abstract

Cement-polymer coalescence involves intricate physical and chemical mechanisms that still remain insufficiently elucidated. To address the coalescing process between cement grains and polymers, a dilute hydration of Portland cement in waterborne epoxy resin (WER) was designed, and the changes of the cement grains at different curing ages (1, 3, 7, and 28 d) were in-situ monitored by micro focused X-ray computed tomography (μ-XCT). SEM/BSE/EDS tests were applied to characterize the element distribution between cement grains and WER. Results show that the size and volume of cement particles in the WER continuously decrease with curing age, evidencing the occurrence of hydration for the cement grains. A coalescent zone between the cement grains and WER with the thickness around 5–10 μm was observed from different directions, confirming the cement-WER coalescence during cement hydration and WER hardening. Moreover, high Ca/Si ratios up to 8 were found in the coalescent zone. The findings provide the direct evidences of cement-WER coalescence, and deepen the knowledge in the organic–inorganic interaction mechanisms towards better designs and manipulations of cement-polymer composites.