Atomic-level insights into the mechanism by which synthetic organic fibers enhance the tensile strength of concrete

Abstract

Improving tensile strength has always been a hot research topic in the field of concrete. Synthetic organic fibers are usually used to enhance the tensile strength of concrete, so it is important to understand its strengthening mechanism. However, there are few reports revealing its mechanism at the atomic scale. To fill this gap, we selected three typical synthetic organic fibers (Polypropylene (PP), Polyacrylonitrile (PAN), and Polyvinyl alcohol (PVA)) to prepare fiber-reinforced concrete (FRC) and investigated the influence mechanism on splitting tensile strength. The influence of fibers on concrete strength were studied and fibers’ state in concrete were observed. Molecular models of fibers and concrete hydration products (calcium hydroxide (CH) and calcium silicate hydrate (CSH)) were established to study the adsorption energy between fiber and hydration products. The chemical properties of fibers were investigated by first principles calculation. Results show that the adsorption energy is positively correlated with the splitting tensile strength of concrete. The adsorption energy of fiber to calcium hydroxide is stronger than that of calcium silicate hydrate. The electronegative groups of fibers are functional groups that increase the tensile strength of concrete splitting. These findings can provide a theoretical basis for fiber modification and serve as a valuable reference for strengthening the strength of the transition zone of concrete.