Collaborative Research: Investigation of the Effect of Fly Ash Variability on Cement Paste Microstructure and Mechanical Properties Using Simulated Fly Ash

合作研究：使用模拟粉煤灰研究粉煤灰变化对水泥浆微观结构和力学性能的影响

• 批准号: 1200045
• 负责人: Amde Amde
• 金额: $ 12.11万
• 依托单位: University of Maryland, College Park
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-04-15 至 2016-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1200045&HistoricalAwards=false
• 关键词: Collaborative; Research; Investigation; Effect; Fly

This research will improve our understanding of the fundamental factors controlling the reactivity of fly ash in Portland cement concrete, leading to more accurate predictive models of performance that will enable the calculation of optimum cement replacement factors for fly ash/cement mix design,. The major innovation is the use of a simulated whole fly ash, which matches all the major properties of a real fly ash, as a model system for investigating systemically the individual factors that control its reactivity. These major properties include the glassy phase composition, the inert mass fraction and composition, and the particle size distribution (PSD). Each simulated fly ash will be a mixture of several types of synthetic glassy particles made with characteristic chemical compositions that match those of real fly ashes. These compositions will be based on analyses of individual fly ash particles using Computer Controlled SEM. The PSD, glass chemical composition and inert fraction will be independently varied among the simulated fly ashes. The mixing of the solid particles will be done using the novel Resonance Acoustic Mixing method to ensure homogenization. This research uses a combination of three measurement techniques to measure the reactivity at different length scales: wet chemistry, thermogravimetry, and standard tests of engineering properties such as compressive strength and durability. Also, the molecular structure of the gel hydration products will be characterized with solid state NMR. This multiscale approach provides a bridge from individual particle data to macroscopic engineering properties. The results of this research will lead to a model of the reactivity as a function of the glass composition, PSD and inerts fraction. It will accelerate the usage of fly ash as a replacement for Portland cement by the concrete industry. In terms of economic benefits, the increased use of fly ash will lower the cost of concrete structures. The environmental benefits include the reduction in the number of landfills otherwise needed for fly ash disposal, as well as reduced energy consumption and lower CO2 emissions from Portland cement manufacture. This collaborative project will enhance the research and education for undergraduate and graduate students between two institutions.

这项研究将加深我们对控制硅酸盐水泥混凝土中飞灰活性的基本因素的理解，导致更准确的性能预测模型，从而能够计算出用于飞灰/水泥配合比设计的最佳水泥替代系数。主要的创新是使用模拟的整个飞灰，它匹配真正的飞灰的所有主要性质，作为一个模型系统，系统地研究控制其反应活性的个别因素。这些主要性能包括玻璃相组成、惰性质量分数和组成以及颗粒尺寸分布(PSD)。每个模拟的飞灰将是几种合成玻璃颗粒的混合物，这些颗粒具有与真正的飞灰相匹配的特征化学成分。这些成分将基于使用计算机控制的扫描电子显微镜对单个飞灰颗粒的分析。模拟飞灰中的PSD、玻璃化学成分和惰性分数将独立变化。固体颗粒的混合将使用新的共振声混合方法来确保均化。这项研究使用三种测量技术的组合来测量不同长度尺度下的反应性：湿化学、热重法和工程特性的标准测试，如抗压强度和耐久性。此外，凝胶水化产物的分子结构将用固体核磁共振进行表征。这种多尺度方法提供了从单个颗粒数据到宏观工程性质的桥梁。这项研究的结果将导致反应性作为玻璃组成、PSD和惰性分数的函数的模型。这将加速混凝土行业使用飞灰作为波特兰水泥的替代品。在经济效益方面，增加粉煤灰的使用量将降低混凝土结构的成本。环境效益包括减少了处理飞灰所需的垃圾填埋场的数量，以及减少了能源消耗和波特兰水泥制造过程中的二氧化碳排放。这一合作项目将加强两所院校对本科生和研究生的研究和教育。