Surfactant properties of a biomimetic antifreeze polymer admixture for improved freeze-thaw durability of concrete

Abstract

Recently, a novel bioinspired approach for improving freeze–thaw resistance of concrete was proposed as an alternative to traditional air entrainment. The mechanism is based on ice recrystallization inhibition (IRI) activity displayed by antifreeze proteins and synthetic, biomimetic replicates, like nonionic polyethylene glycol–graft–polyvinyl alcohol (PEG-PVA), which can be added as a polymeric admixture to concrete in the fresh state. To further substantiate the mechanistic underpinnings of the air-entraining agent (AEA) alternative, this work measures and reports the foam stability and interfacial surface tension properties of nonionic PEG-PVA. Foam stability and tensiometry measurements of PEG-PVA were quantified and compared to a conventional anionic AEA, MasterAir (MA). Results demonstrate that PEG-PVA requires much higher concentrations (0.77–2.8% by weight of cement) to form a stable foam system in comparison to the AEA (0.027–0.19%). The results correlated well with foam stability measurements, which showed PEG-PVA’s inability to form long-lasting stable foams in comparison to MA. Tensiometry measurements also revealed that high concentrations (10–60 g/L) of PEG-PVA were required to reduce the surface tension of water in comparison to MA (0.015–0.045 g/L), indicating that PEG-PVA neither acts as a surfactant nor readily self-assembles into micelles at concentrations that proved to provide freeze–thaw resistance. Nevertheless, PEG-PVA-modified concrete showed similar resistance to MA-modified concrete in freeze–thaw cycling at concentrations as low as 0.066% by weight of cement while entraining only minimal amounts of air, suggesting that the freeze–thaw resistance is due at least in part to the IRI activity of PEG-PVA instead of its ability to entrain a proper air void system.