Engineering Microbial-Induced Carbonate Precipitation via Meso-Scale Simulations

老化的基础设施是一个日益严重的经济和环境问题。经济，因为虽然一立方米混凝土的生产成本在45英镑到55英镑之间，但据估计，目前修复/维护一立方米相同材料的直接成本约为100英镑。环保是因为水泥生产产生的二氧化碳占全球排放量的5%到8%。抵消混凝土的降解将降低对新材料的需求，从而减少资源的消耗和温室气体的排放。工程师们提出了一种革命性的解决方案，其灵感来自大自然：由于细菌的代谢活动，能够自我修复的自我修复材料。混凝土愈合的主要机制是微生物诱导的碳酸钙沉淀（MICP）， MICP填充损伤材料的裂缝。然而，目前微生物自愈混凝土技术的方法是确定少数几种细菌，这些细菌适用于有限的混凝土和环境，并通过实验逐步优化它们的MICP性能。这导致解决方案很难转移到新的应用中，除非进行新的昂贵的实验活动。在这一建议中，我们的目标是提供一个新的理论基础，一旦确定了周围环境混凝土的特定应用化学成分，就可以预测细菌和混凝土最有希望的组合。这将为混凝土细菌系统的数字化设计建立一个新的范例，并将使整个建筑部门的技术转移成为可能。我们提出的方法包括两个主要步骤：1)开发和验证世界上第一个混凝土细菌自愈模拟器，从单个裂缝的长度尺度（1-100微米）开始，然后将自愈动力学信息传递到混凝土力学的宏观模拟；2)使用新的模拟器为实验活动提供信息，旨在优化自愈合混凝土的配方，以应用于工业废水处理的侵略性化学环境。新的模拟器将通过建立在纽卡斯尔和卡迪夫大学最近开发的三个现有的最先进的模拟器上获得，并且该模型迄今为止分别涉及自我修复的三个主要步骤：i)细菌生长；Ii)浸在溶液中的矿物颗粒集合体的动力学演化；iii)随强度和刚度变化的混凝土构件宏观力学。实验将首先为模拟和验证数据提供输入。这些实验将在大学实验室进行，并将涉及所有相关的长度尺度，从混凝土中矿物相形态的纳米尺度，到单个裂缝内自愈过程的微观尺度，再到自愈混凝土样品的宏观尺度。经过验证的模拟将用于预测模拟污水处理厂内的环境条件。模拟将确定细菌和混凝土化学的最佳组合，以确保在这种条件下的自修复，最终的实验将产生模拟引导的自修复混凝土，并在我们的工业合作伙伴Northumbrian Water的设施中测试它们的性能。如果成功，该项目将通过模拟提供一种全新的方法来设计自愈材料。这将大大降低开发这些材料的成本、时间和不确定性，提高该领域的进展速度，并使英国在这项新技术方面处于世界前列。

Ageing infrastructure is an increasing economic and environmental problem. Economic because, while the production cost of one cubic metre of concrete varies between £45 - £55, it is estimated that currently the direct cost for repairing/maintaining one cubic metre of the same material is around £100. Environmental because production of cement generates 5 to 8% of the world's carbon dioxide emissions. Counteracting the degradation of concrete would lower the requirement for new materials and thus reduce the consumption of resources and the emission of greenhouse gases. Engineers have proposed a revolutionary solution, which was inspired by nature: self-healing materials able to self-repair as a result of the metabolic activity of bacteria. The main mechanism of concrete healing is the microbial-induced precipitation of calcium carbonate (MICP), which fills the cracks of the damaged material. However, the current approach in microbial self-healing concrete technology is to identify a few species of bacteria that work for limited sets of concretes and environments, and to optimise their MICP performance incrementally by experiments. This leads to solutions that are poorly transferable to new applications, unless new costly experimental campaigns are undertaken. In this proposal we aim to provide a new theoretical basis to predict the most promising combinations of bacteria and concrete, once the application-specific chemical compositions of the concrete of the surrounding environment are identified. This will establish a new paradigm for the digital design of concrete-bacteria systems and will enable technology transfer across the constructions sector.The approach we propose entails two main steps:1) developing and validating the world-first simulator of bacterial self-healing in concrete, starting from the length-scale of a single crack (1-100 micrometres) and then transferring information on the kinetics of self-healing to macroscale simulations of concrete mechanics;2) using the new simulator to inform an experimental campaign aimed at optimising the formulation of self-healing concrete for application in the aggressive chemical environment of an industrial wastewater treatment.The new simulator will be obtained by building on three existing state-of-the-art simulators that have been very recently developed at Newcastle and Cardiff universities and that model, to date separately, the three main steps involved in self-healing: i) bacterial growth; ii) kinetic evolution of an aggregate of mineral particles immersed in a solution; and iii) macro-mechanics of concrete elements with evolving strength and stiffness.The experiments will first provide inputs to the simulations and data for their validation. These experiments will be carried out in university laboratories and will address all the relevant length scales, from the nanoscale of the morphology of the mineral phases in concrete, to the microscale of the self-healing process inside single cracks, to the macroscale of self-healing concrete samples.The validated simulations will be run predictively to simulate the environmental conditions inside a wastewater treatment plant. The simulations will identify the best combinations of bacteria and concrete chemistry to ensure self-healing in such conditions, and the final experiments will produce the simulation-guided self-healing concrete and test their performance in the facilities of our industrial partner Northumbrian Water.If successful, this project will provide a completely new way to approach the design of self-healing materials via simulations. This would drastically reduce the cost, time, and uncertainty related to developing these materials, enhancing the rate of progress in the field by orders of magnitude and putting the UK at the forefront worldwide in this new technology.