Characterizing the reactivity and industrial ecology of pseudowollastonite to enable highperformance building materials from waste streams

普通波特兰水泥是一种重要的建筑材料，具有很大的环境足迹。研究小组开展的初步工作表明，另一种替代材料伪硅灰石(Pwol)是硅酸钙(CaSiO3)的高温多晶型，在水化和碳化过程中可以形成各种板状矿物产品。这些产品似乎类似于矿物相，正是这些矿物相赋予了古罗马水泥很大的强度，以及即使在会迅速降解现代水泥的环境中，随着时间的推移也能获得强度的非凡能力。此外，有理由预计，用这些产品中的一种或多种取代波特兰水泥可能会导致环境足迹减少。然而，关于哪些反应和化学条件的结合导致了这些相的形成，仍然存在大量的问题。该项目将发展部署普沃尔基水泥所需的物理化学知识，以及以经济上具有竞争力和可持续的方式部署这些类型材料的系统级生命周期和技术经济潜力。这项工作分为四个研究任务--任务1.表征在一系列自然水和大气条件下Pwol碳化和水化的化学动力学。任务2.评估生成的矿物相的化学稳定性。任务3.测量普沃尔水泥的机械强度。任务4.了解普沃尔水泥的工业生态。这项工作将包括在理解高温下Pwol的水碳化方面的基本进展。初步实验表明，Pwol与CO2、H2O和Na+的反应与硅灰石非常不同，硅灰石已经被积极开发为一种碳中性水泥替代品。Pwol反应产物将在一系列典型条件下进行化学稳定性和机械强度测试。同时，将研究Pwol基水泥的工业生态，以评估这种水泥替代品的经济机会和环境影响。Pwol在自然界中相对少见，但在工业废流中大量存在，如水泥窑粉尘。它也有可能用其他废液合成，比制造普通波特兰水泥所需的能源更少。这些材料的固化需要热量、水分和二氧化碳，可以在烟道气流存在的情况下进行，因此将进行地理空间分析，以了解这些废物流在美国的哪些地方非常接近。开发碳捕获、利用和封存(CCUS)技术的努力，就像这里提出的那样，部分是出于减少温室气体净排放的目标。量化这些排放可能具有挑战性，尤其是对创新技术而言。为了支持提高开展CCUS活动的透明度，该项目将制定准则和一个开放源码工具，用于评估CCUS项目在具体替代品领域的生命周期绩效。这样的努力可以作为其他CCUS应用领域的典范，帮助促进CCUS早期风险的透明度和快速评估。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。

Ordinary Portland cement is a critical building material with a large environmental footprint. Preliminary work carried out by the investigator's group suggests that an alternative material, pseudowollastonite (PWOL), which is a high temperature polymorph of calcium silicate (CaSiO3), can form a variety of platey mineral products during hydration and carbonation. It appears that these products resemble the mineral phases that give ancient Roman cement much of its strength and its remarkable ability to gain strength over time even in environments that would rapidly degrade modern cements. Also, there is reason to anticipate that substituting one or more of these products for Portland cement may lead to a decreased environmental footprint. However, a large number of questions exist as to which combination of reactions and chemical conditions result in the formation of these phases. This project will develop both the physicochemical understanding needed to deploy PWOL-based cements and the systems-level life cycle and techno-economic potential of deploying these types of materials in an economically competitive and sustainable manner. The work is divided into four research tasks-- Task 1. Characterize the chemical kinetics of PWOL carbonation and hydration under a range of natural water and atmospheric conditions. Task 2. Evaluate the chemical stability of the resulting mineral phases. Task 3. Measure the mechanical strength of PWOL cements. Task 4. Understand the Industrial Ecology of PWOL cements. This work will include fundamental advances in the understanding of aqueous carbonation of PWOL at high temperatures. Preliminary experiments suggest that PWOL reacts very differently with CO2, H2O, and Na+ than wollastonite, which is already being actively developed as a carbon neutral cement alternative. The products of PWOL reactions will be tested for their chemical stability and mechanical strength under a range of representative conditions. In parallel, the industrial ecology of PWOL-based cements will be studied to evaluate both the economic opportunity and environmental implications of this cement substitute. PWOL is relatively uncommon in nature but abundant in industrial waste streams such as cement kiln dust. It is also possible that it could be synthesized using other waste streams using less energy than it takes to make ordinary Portland cement. The curing of these materials, which require heat, moisture andCO2, could occur in the presence of a flue gas stream, and so a geospatial analysis will be carried out to understand where in the United States these waste streams are in close proximity. Efforts to develop carbon capture, utilization, and storage (CCUS) technologies, like the one proposed here, are motivated in part by the goal of reducing net emissions of greenhouse gas. Quantifying those emissions can be challenging, especially for innovative technologies. To support greater transparency in pursuing CCUS activities, this project will develop guidelines and an open-source tool for evaluating the life cycle performance of CCUS projects in the concrete alternatives space. Such an effort can serve as a model for other CCUS applications areas to help promote transparency and rapid assessment of early-stage CCUS ventures.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.