Experimental Study of Biomimetic Antifreeze Polymers for Improved Durability of Cementitious Binders

University Of Colorado At Boulder, Boulder CO

Investigators

Abstract

Ice is one of the few substances on Earth that expands when it freezes. Consequently, this expansion is destructive to porous materials, like concrete that are exposed to water and experienced freeze-thaw cycling. Conventional methods used to counter freeze-thaw deterioration in cement-based materials include entraining ~5-10% air (by volume), which reduces bulk mechanical properties, or applying deicing salts on the surface, which exacerbates chloride-induced corrosion of steel reinforcement. For more than 70 years, these methods have remained virtually unchanged. Inspired by nature, this work seeks to design and synthesize biomimetic antifreeze polymers (BAPs) that explicitly mimic the activity, function, and structure of antifreeze proteins (AFPs) naturally found in plants, insects, and bacteria and assess their suitability as an admixture biotechnology for cement-based materials. The research activities will enhance the long-term durability of cement-based materials and promote the sustainability and resilience of civil infrastructure. As part of this effort, the project team will engage local and global audiences via a videotaped seminar series on biomimetic architecture and living buildings in collaboration with Boulder Biomimicry, local biomimicry experts, and Women in Science and Engineering (WiSE) student organization at the University of Colorado Boulder. Using natural AFPs as a biological template, this work will first determine an ideal biomolecular model by studying the thermal hysteresis behaviors of recombinant AFPs in ionic media with a focus on synthetic, highly alkaline, ordinary portland cement and alkali-activated cement concrete pore solutions. BAPs will be synthesized using common biopolymers (i.e., PLGA) with modified moieties to explicitly mimic the ice-binding and ice-structuring behavior of native AFPs. The ice-binding and ice-structuring mechanisms of natural AFPs and synthetic BAPs will be investigated, in addition to their longevity, survivability, and efficacy in hardened cement paste and in concrete. This work will provide new knowledge on ice crystallization inhibition behavior of AFPs and synthetic BAPs in highly alkaline environments, which represents a significant departure from current BAP technologies that are being tested for biologically relevant applications. In addition, this work advances state-of-the-art antifreeze polymer technologies by designing BAPs that not only imitate the thermal hysteresis activity of native AFPs, but also explicitly mimic their functional (ice-binding) and structural (ice-structuring) mechanisms. Successful mimicking of these mechanisms will lead to a suite of disruptive admixture biotechnologies to conventional freeze-thaw durability approaches for cementitious materials.