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

冰是地球上少数几种在冻结时会膨胀的物质之一。因此，这种膨胀对多孔材料是破坏性的，如暴露于水并经历冻融循环的混凝土。用于对抗水泥基材料冻融劣化的常规方法包括夹带约5-10%的空气（按体积计），这会降低整体机械性能，或在表面上施用除冰盐，这会加剧钢筋的氯化物诱导腐蚀。70多年来，这些方法几乎没有改变。受自然界的启发，这项工作旨在设计和合成仿生防冻聚合物（BAP），明确模仿植物，昆虫和细菌中天然存在的防冻蛋白（AFP）的活性，功能和结构，并评估其作为水泥基材料混合物生物技术的适用性。研究活动将提高水泥基材料的长期耐久性，并促进民用基础设施的可持续性和复原力。作为这项工作的一部分，项目团队将通过与博尔德仿生学、当地仿生学专家和科罗拉多博尔德大学的科学与工程妇女（WISE）学生组织合作，举办一系列关于仿生建筑和生活建筑的视频研讨会，吸引当地和全球观众。 以天然AFP为生物模板，研究了人工合成、高碱性、普通波特兰水泥和碱激活水泥混凝土孔隙溶液中重组AFP在离子介质中的热滞行为，确定了理想的生物分子模型。BAP将使用常见的生物聚合物（即，PLGA）与修饰的部分，以明确模拟天然AFP的冰结合和冰结构化行为。冰绑定和冰结构机制的天然AFP和合成BAP将进行调查，除了他们的寿命，生存能力，和硬化水泥浆和混凝土中的功效。这项工作将提供关于AFP和合成BAP在高碱性环境中的冰结晶抑制行为的新知识，这代表了与目前正在测试生物相关应用的BAP技术的重大偏离。此外，这项工作通过设计BAP来推进最先进的防冻聚合物技术，BAP不仅模仿天然AFP的热滞后活性，而且明确模仿其功能（冰结合）和结构（冰结构化）机制。这些机制的成功模仿将导致一套破坏性的外加剂生物技术，以传统的冻融耐久性的方法，胶凝材料。

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.