EAGER: Increased Service Life of Sustainable Cements via Electric Fields

这个早期概念探索性研究奖助金(EARGER)项目专注于通过施加电场来改变硬化水泥的内部结构。水泥是生产混凝土的关键成分，混凝土是一种不可替代的建筑材料，在全球使用量上仅次于水。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，世界对建筑材料的永无止境的需求将继续存在。因此，目前占人为二氧化碳排放量7%的水泥必须进行快速和彻底的脱碳，以减轻其对气候变化的影响。使用更可持续的水泥将显著减少这些二氧化碳的排放；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来满足这些需求，目的是在固化前使用外加电场故意改变可持续水泥中的原子排列。预计更多的结晶型水泥将更加耐用，因为它增强了热力学稳定性，延长了使用寿命，从而在混凝土行业中进一步减少了二氧化碳排放。这项研究将利用电场通过提高传统和可持续水泥的主要粘结剂凝胶的纳米级有序性(即结晶度)来有意提高其热力学稳定性。考虑到相的结晶度直接影响其热力学稳定性，增加粘结剂凝胶的结晶度将提高对化学诱导的变化(如pH诱导的脱钙)的抵抗力。这将延长混凝土的使用寿命，也有可能改善混凝土的物理和力学性能。在本项目中，将在硅酸盐激发的闪速煅烧偏高岭土、硅酸盐激发矿渣和普通硅酸盐水泥(OPC)浆体中施加电场，并利用等温量热、X射线对分布函数分析和低温透射电子显微镜(Cryo-TEM)等一系列实验技术来测量电场对反应动力学、力学性能和结晶度的影响。此外，为了进一步促进结晶相的形成，还将探索高介电常数掺杂纳米材料与电场之间的协同作用，其中将揭示(I)掺杂形貌和(Ii)掺杂介电常数对结晶度的影响。将电场应用于这些包含高介电常数掺杂纳米颗粒的系统，应该会减少与电场引发的晶体成核相关的能量，从而减少那些包含各向异性掺杂纳米颗粒的系统，从而进一步促进晶体粘结剂的形成。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.