Assessing Interfacial Bonding Performance of PVA Fiber and Cement Hydration Products: An Atomic Simulation

The composition and properties of the interface are the key points which determine the properties of fiber-reinforced cement-based composites. The bonding performance between fibers and different hydration products at the interface is the basis for the understanding of the interface transition zone. In this paper, the influence of different hydration products on interfacial bonding performance was investigated using the molecular dynamics method. The three models were established to study the difference in the static structure of the interface between different hydration products and polyvinyl alcohol (PVA) fibers, and then the influence of different hydration products on the interfacial adhesion properties was analyzed using fiber pull-out simulation. The results showed that the interfacial adhesion properties between PVA fiber and calcium silicate hydrate (PVA-CSH) was the best. The PVA-CSH interface is connected mainly by Ca-O bonds and H bonds, and the stability of the chemical bonds is very high. The strong interface interaction gives the CSH-PVA interface good adhesion performance, so it is necessary to overcome a large interfacial adhesion force when the fiber is pulled out. The PVA-AFt (ettringite) interface also is connected by Ca-O bonds and H-bonds. However, the stability and coordination number of the chemical bond are lower than those of the CSH-PVA interface. There are only a few weak H-bonds at the PVA-calcium hydroxide (CH) interface, which resulted in the worst interfacial adhesion performance; the force required to pull fibers out of the matrix was very small.