Effects of Bisphenol A Diglycidyl Ether (DGEBA) Epoxy on the Properties of Mortar: From Macro to Nano Scale

The study explored the effect of DGEBA content on the performance improvement of epoxy mortar through macro- and micro-combined experiments. On this basis, through the characterization method of molecular dynamics (MD) simulation, the bonding situation between atoms of epoxy in the mortar at the nanoscale was revealed, and the bonding mechanism of the adsorption interface was further revealed. Through the mechanical test, it was found that when DGEBA:m-PDA = 5:1, the epoxy has a significant effect on the improvement of mortar. When the content was 0.10%, the compressive strength and flexural strength of the mortar were 64.53 and 8.39 MPa, respectively. The interface bonding test was used to characterize its bonding with building components. On this basis, the durability, hydration performance, and microscopic characterization of mortar were tested. Finally, the bonding mechanism between epoxy and the calcium silicate hydrate (C–S–H) interface was revealed by MD simulation. According to the above methods, it was found that the flexible chain structure of DGEBA can modulate the aggregation state of the system, which in turn affected the interfacial interaction between epoxy and C–S–H. More importantly, the ″water-locking effect″ of epoxy was innovatively proposed as an influencing mechanism, further promoting the early hydration reaction of cement. In addition, the cured epoxy particles can further enhance the density of the specimens by filling the internal pores of the mortar. When the content of epoxy was 0.10%, cured epoxy particles can further enhance the density of the specimens by filling the internal pores of the mortar.