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，对环境的影响很大。研究小组进行的初步工作表明，一种替代材料，假硅灰石（PWOL），这是一种高温多晶型的硅酸钙（CaSiO3），可以在水合和碳酸化过程中形成各种板状矿物产品。这些产品似乎类似于赋予古罗马水泥大部分强度的矿物相，即使在现代水泥迅速降解的环境中，也能随着时间的推移获得强度。此外，有理由预期，用这些产品中的一种或多种替代波特兰水泥可能会减少环境足迹。然而，存在大量的问题，即反应和化学条件的组合导致这些相的形成。该项目将开发部署PWOL基水泥所需的物理化学理解，以及以经济上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。本研究分为四个研究任务：任务1。表征在一系列天然水和大气条件下PWOL碳酸化和水合的化学动力学。任务2.评估所得矿物相的化学稳定性。任务3.测量PWOL骨水泥的机械强度。任务4.了解PWOL水泥的工业生态。这项工作将包括在高温下PWOL的水碳酸化的理解的根本性进展。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碳中性水泥替代品。将在一系列代表性条件下测试PWOL反应产物的化学稳定性和机械强度。与此同时，将研究PWOL基水泥的工业生态学，以评估这种水泥替代品的经济机会和环境影响。PWOL在自然界中相对罕见，但在水泥窑粉尘等工业废物流中含量丰富。也有可能使用其他废物流合成它，使用比制造普通波特兰水泥所需的更少的能量。这些材料的固化需要热量、水分和二氧化碳，可能会在烟道气流存在的情况下发生，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、利用和储存（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，特别是对于创新技术。为了支持在开展CCUS活动时提高透明度，该项目将制定准则和一个开源工具，用于评估CCUS项目在具体替代品领域的生命周期绩效。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值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.