The goal of this project was to synthesize and evaluate a class of low-cost, non-toxic, biodegradable antifreeze biopolymers and biomimetic small molecules. The molecules were evaluated for their effectiveness in preventing or slowing ice formation and growth on roadway and bridge surfaces during winter and as an additive to concrete in lieu of entrained air system.
The work was carried out in three stages. Stage I focused on the identification, synthesis, and characterization of biomimetic antifreeze molecules (BAMs). Polyvinyl alcohol (PVA), polyvinyl alcohol-polyethylene glycol-graft-copolymer (PVA-g-PEG), poly(2-hydroxyethyl methacrylate) (pHEMA), poly(2-hydroxypropyl methacrylamide) (pHPMA), gelatin, and folic acid, citric acid, and 2-hydroxyethyl methacrylate (HEMA) BAMs were synthesized or synthetically modified to mimic ice-binding residues and were investigated for their ice recrystallization inhibition (IRI) and freezing point depression. BAM activity was tested in deionized water as a proxy. Results suggest that BAMs in ultra-low concentrations (<0.01 mg/mL) can inhibit ice recrystallization. Smaller molecules were found to be less IRI active than larger molecules, but HEMA alone was found to depress the freezing point by 2 to 4„aC at concentrations of 1 to 10 mg/mL—behavior that is similar to moderate concentrations of common deicing salts. Stage II focused on the biodegradability and cytotoxicity of BAMs. Biocompatibility of BAMs were assessed and compared to traditional deicing solutions using a LIVE/DEAD assay with human-derived dermal and lung cells. Results indicate that PVA, PVA-g-PEG, folic acid, and pHPMA perform as well as (or better than) traditional deicing solutions (i.e., NaCl, MgCl2, CaCl2) in the LIVE/DEAD assay. Degradability of BAMs in aqueous river water was assessed. PEG and PVA-g-PEG displayed mild degradation after 16 weeks, while PVA exhibited no degradation. Stage III focused on testing the ability of BAMs to perform as deicers and additives for freeze-thaw resistance. Additionally, PVA and PVA-g-PEG were studied for freeze-thaw resistance in ordinary portland cement (OPC) paste. While these molecules were found to be non-effective deicers, both polymers displayed freeze-thaw resistance in ordinary portland cement (OPC) paste in modified ASTM C666 testing. PVA-g-PEG modified concrete displayed freeze-thaw resistance in ASTM C666 testing.
In summary, it was found that BAMs would not effectively melt ice once it has formed nor provide additional synergistic benefit to using the molecules in tandem with traditional deicers. Contrastingly, BAMs did prevent freeze-thaw damage in cement paste and concrete. The results of this IDEA concept provide the foundational work for BAMs as an alternative to traditional air entraining agents for freeze-thaw resistance in concrete. The results of freeze-thaw testing clearly show that BAM-modified cement paste and concrete are freeze-thaw resistant and that the freeze-thaw resistance occurs with minimal air entrainment in concrete.
The final report is available.