Functional group selection and topological effects in concrete transport inhibitors: Nano-mechanisms and design principles

Abstract

Chloride ion (Cl⁻) ingress significantly reduces the durability of reinforced concrete, particularly in marine environments, due to the high permeability of concrete pores. Concrete transportation inhibitors (CTIs) have emerged as a potential solution, yet their inhibition mechanisms remain unclear. In this study, molecular dynamics simulations and quantum chemical analyses are employed to elucidate the performance of surfactant-like CTIs. Results show that the enhancement of nanoscale interfacial tension (IFT) is central to reducing fluid transport. Among the tested structures, the Bola-type molecule with phosphonic acid head groups (B-PO₃²⁻) demonstrates the strongest adsorption to calcium silicate hydrate (C-S-H), low self-aggregation, and an enlarged interaction area with water. These properties allow B-PO₃²⁻ to act as an effective nanoscale barrier to chloride penetration. This work provides a molecular-level framework for evaluating CTIs and offers design principles for next-generation concrete additives aimed at improving durability in aggressive environments.