EAGER: Increased Service Life of Sustainable Cements via Electric Fields

这个早期概念的探索性研究资助（EAGER）项目的重点是通过电场的应用来改变硬化水泥的内部结构。 水泥是生产混凝土的重要成分，是一种不可替代的建筑材料，在全球使用量仅次于水。随着未来几十年人口增长预计将大幅增加，以及随之而来的大规模城市化，世界对建筑材料的需求将继续无法满足。因此，水泥目前占人为二氧化碳排放量的7%，必须进行快速和剧烈的脱碳，以减轻其对气候变化的影响。使用更可持续的水泥将大大减少这些二氧化碳排放量;然而，这些水泥还需要具有较长的使用寿命和高水平的耐久性。该项目通过基础研究解决了这些需求，旨在使用外加电场在固化前故意改变可持续水泥中的原子排列。据设想，由于增强的热力学稳定性，更多的结晶水泥将更耐用，延长使用寿命，从而在混凝土工业中提供额外的CO2节约。这项研究将利用电场，通过增强纳米级有序（即，结晶度）。考虑到相的结晶度直接影响其热力学稳定性，增加粘合剂凝胶结晶度将改善对化学诱导的变化（例如pH诱导的脱钙）的抗性。这将延长混凝土的使用寿命，并有可能改善混凝土的物理力学性能。在这个项目中，电场将被施加到硅酸盐活化的闪烧偏高岭土，硅酸盐活化矿渣和普通波特兰水泥（OPC）浆体，其对反应动力学，力学性能和结晶度的影响将使用一套实验技术，包括等温量热法，X射线对分布函数分析和低温透射电子显微镜（cryo-TEM）测量。此外，为了进一步增强结晶粘合剂相的形成，将探索高介电常数掺杂剂纳米材料与电场之间的协同作用，其中将揭示（i）掺杂剂形态和（ii）掺杂剂介电常数对结晶度的影响。将电场施加到这些含有高介电常数掺杂剂纳米颗粒的系统应减少与电场激发的晶体成核相关的能量，并且含有各向异性掺杂剂纳米颗粒的那些也是如此，该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的评估来支持。影响审查标准。

This EArly-concept Grant for Exploratory Research (EAGER) project focuses on the modification of hardened cement internal structure via the application of electric field. Cement is a vital ingredient for the production of concrete, an irreplaceable construction material that is second only to water in terms of global usage. With population growth forecast to significantly increase over the coming decades and, with it, substantial urbanization, the world’s insatiable need for construction materials will continue. Thus, it is imperative that cement, which is currently responsible for 7% of anthropogenic CO2 emissions, undergoes rapid and drastic decarbonization to mitigate its effect on climate change. The use of more sustainable cements will significantly reduce these CO2 emissions; however, these cements also need to possess long service-lives and high levels of durability. This project addresses these needs via fundamental research aiming at using applied electric fields to deliberately change the atomic arrangements in sustainable cements prior to setting. It is envisioned that more crystalline cements will be more durable due to enhanced thermodynamic stability, elongating service-lives and thus providing additional CO2 savings in the concrete industry. This research will exploit electric fields to deliberately increase the thermodynamic stability of traditional and sustainable cements by enhancing the nanoscale ordering (i.e., degree of crystallinity) of their main binder gels. Given that the degree of crystallinity of a phase directly influences its thermodynamic stability, increasing the binder gel crystallinity will improve resistance to chemically-induced changes such as pH-induced decalcification. This will extend the service life of the concrete, and also has the potential to improve the physical and mechanical properties of the concrete. In this project, an electric field will be applied to silicate-activated flash calcined metakaolin, silicate-activated slag and ordinary Portland cement (OPC) paste, and its impact on reaction kinetics, mechanical properties and degree of crystallinity will be measured using a suite of experimental techniques that includes isothermal calorimetry, X-ray pair distribution function analysis and cryo-transmission electron microscopy (cryo-TEM). Moreover, to further enhance formation of crystalline binder phases the synergy between high dielectric constant dopant nanomaterials and electric fields will be explored, where the impact of (i) dopant morphology and (ii) dopant dielectric constant on the degree of crystallinity will be uncovered. Application of the electric field to these systems containing the high dielectric constant dopant nanoparticles should reduce the energy associated with electric-field-instigated crystal nucleation, and so too those containing anisotropic dopant nanoparticles, thereby further enhancing the formation of a crystalline binder.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.