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

冰是地球上少数几种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劣化的传统方法包括：在水泥基材料表面引入5-10%的空气(按体积计算)，这会降低体积力学性能；或者在表面涂抹除冰盐，这会加剧氯离子对钢筋的腐蚀。70多年来，这些方法几乎没有变化。受自然的启发，这项工作旨在设计和合成仿生防冻聚合物(BAP)，明确模拟植物、昆虫和细菌中自然存在的抗冻蛋白(AFP)的活性、功能和结构，并评估它们作为水泥基材料外加剂的适宜性。研究活动将增强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韧性。作为这项工作的一部分，项目团队将通过与博尔德仿生公司、当地仿生专家和科罗拉多大学博尔德大学妇女科学与工程(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。本工作将以天然AFP为生物模板，通过研究重组AFP在离子介质中的热滞行为，重点研究合成的、高碱性的、普通的硅酸盐水泥和碱激发的水泥混凝土孔洞溶液，确定理想的生物分子模型。BAPS将使用带有修饰部分的常见生物聚合物(即PLGA)来合成，以明确模拟天然AFP的冰结合和冰结构行为。除了研究它们在硬化水泥浆体和混凝土中的寿命、存活率和有效性外，还将研究天然AFP和合成BAP的结冰和结冰机理。这项工作将为AFP和合成BAP在高度碱性环境中的冰结晶抑制行为提供新的知识，这与目前正在测试的生物相关应用的BAP技术有很大不同。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，这些BAP不仅模拟本地AFP的热滞活性，而且明确模拟其功能(结合冰)和结构(构造冰)机制。对这些机制的成功模仿将导致一套颠覆性的生物技术，以取代传统的水泥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.