Abstract
This work presents experimental evidence that specific molecular weights of poly(vinyl alcohol) (PVA), a molecule that displays biomimetic ice recrystallization inhibition (IRI) behavior, are required to impart freeze-thaw resistance to portland cement paste when PVA is added as a water-solubilized admixture. Three molecular weights of PVA were first tested for IRI activity. IRI-active PVA-modified cement pastes were then prepared and tested for freeze-thaw resistance. X-ray micro-computed tomography was employed to investigate internal damage and to characterize the air void system. Differential scanning calorimetry was used to quantify and compare the amount of ice that formed in the hardened pastes. Mercury intrusion porosimetry was used to characterize the pore-size distributions of cement pastes. Results substantiate that PVA with a molecular weights >31,000 g/mol can impart freeze-thaw resistance to cement paste and that the freeze-thaw enhancement is not due to improved hydrophobicity or an adequately entrained air void system. PVA additions did lead to reductions in porosity. However, the reductions were insufficient to fully explain why lower quantities of ice formed during freezing, indicating that IRI-active biomimetic polymers, like PVA, can enhance the freeze-thaw resistance of cement paste due, in part, to their interaction with ice.
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