Robust poly(urea-formaldehyde)/sodium alginate microcapsules for achieving efficient self-healing in concrete

Abstract

Microcracks will inevitably develop in concrete during its service life. To prolong the lifespan of concrete and facilitate the automatic repair of microcracks within the matrix, novel composite microcapsules were prepared. Poly(urea-formaldehyde) resin (PUF) and sodium alginate(SA) were used to construct the walls and epoxy resin(EP) was used as the core, EP@PUF/SA microcapsules were prepared by in-situ polymerization. The surface morphology, particle size distribution, chemical structure, and thermal stability of the microcapsules were analyzed by polarizing optical microscopy (POM)/scanning electron microscopy (SEM), laser particle size determination, fourier-transform infrared spectroscopy (FTIR), and thermogravimetry (TG), respectively. It was concluded that the introduction of SA enhanced the integrity of the microcapsules, led to a decrease in the microcapsule wall thickness, and increased the core content to 80.57 ± 2.4 wt%. EP@PUF/SA microcapsule-based self-healing concrete was prepared and its mechanical properties and self-healing performance were determined. When the microcapsule content was 12 wt% and the repair age was 45 d, the compressive strength recovery rate of microcapsule-based self-healing concrete was 157.32 ± 5.60 %.