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

冰是地球上为数不多的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，比如暴露在水中并经历冻融循环的混凝土。用于防止水泥基材料冻融变质的传统方法包括：吸入~5-10%的空气（按体积计算），这会降低整体机械性能；或者在表面施用除冰盐，这会加剧氯化物对钢筋的腐蚀。70多年来，这些方法几乎没有改变。受大自然的启发，这项工作旨在设计和合成仿生抗冻聚合物（BAPs），明确模仿天然存在于植物、昆虫和细菌中的抗冻蛋白（AFPs）的活性、功能和结构，并评估其作为水泥基材料外加剂的适用性。研究活动将提高水泥基材料的长期耐久性，促进民用基础设施的可持续性和弹性。作为这项工作的一部分，项目团队将与博尔德仿生学、当地仿生学专家和科罗拉多大学博尔德分校科学与工程女性（WiSE）学生组织合作，通过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的观众。本工作将首先以天然AFPs为生物模板，通过研究重组AFPs在离子介质中的热滞后行为，确定理想的生物分子模型，重点研究合成、高碱性、普通硅酸盐水泥和碱活化水泥混凝土孔隙溶液。BAPs将使用普通的生物聚合物（即PLGA）和修饰的片段来合成，以明确模仿天然afp的冰结合和冰结构行为。研究人员将研究天然afp和合成bap的冰结和冰结构机制，以及它们在硬化水泥浆和混凝土中的寿命、生存能力和功效。这项工作将为afp和合成BAP在高碱性环境下的冰结晶抑制行为提供新的知识，这与目前正在进行生物学相关应用测试的BAP技术有很大的不同。此外，这项工作还通过设计BAPs来推进最先进的防冻聚合物技术，这些BAPs不仅模仿了天然AFPs的热滞后活性，而且明确地模仿了它们的功能（冰结合）和结构（冰结构）机制。这些机制的成功模拟将导致一套颠覆性的外加剂生物技术，以取代传统的胶凝材料冻融耐久性方法。

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.