An improved basis for characterizing the suitability of fly ash as a cement replacement agent
An improved basis for characterizing the suitability of fly ash as a cement replacement agent
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表征粉煤灰作为水泥替代剂的适用性的改进基础
DOI：
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发表时间：
2017
期刊：
影响因子：
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通讯作者：
G. Sant
中科院分区：
文献类型：
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作者：
Tandré Oey;Jason Timmons;P. Stutzman;J. Bullard;Magdalena Balonis;M. Bauchy;G. Sant
粉煤灰是部分替代普通波特兰水泥（OPC）在混凝土混合物的粘合剂部分的关键材料。然而，显著的成分可变性目前限制了粉煤灰的使用。例如，OPC-飞灰混合物的性能不能使用当前的表征标准（例如，ASTM C618）。在这项研究中，粉煤灰跨越广泛的组成范围内的玻璃和结晶相的特征在于使用X射线荧光（XRF），X射线衍射（XRD），和扫描电子显微镜与X射线能量色散谱（SEM-EDS）技术的组合。将组成数据提取为无单位参数，网络比（Nr），其表示形成构成粉煤灰的碱金属/碱土金属-铝硅酸盐玻璃的原子的网络行为。Nr与已知的组成相关特征相关，包括玻璃化转变温度和非晶XRD峰（“驼峰”）位置。热释放数据和抗压强度的分析用于评估粉煤灰组合物的反应动力学和水泥粉煤灰混合物的工程性能的影响。结果表明，具有高网络比（即，具有较不稳定的玻璃结构）比其它的更具反应性。
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Fly ash is a critical material for partial replacement of ordinary portland cement (OPC) in the binder fraction of a concrete mixture. However, significant compositional variability currently limits fly ash use. For example, the performance of OPC-fly ash blends cannot be estimated a priori using current characterization standards (e.g., ASTM C618). In this study, fly ashes spanning a wide compositional range are characterized in terms of glassy and crystalline phases using a combination of X-ray fluorescence (XRF), X-ray diffraction (XRD), and scanning electron microscopy with X-ray energy dispersive spectroscopy (SEM-EDS) techniques. The compositional data are distilled to a unitless parameter, the network ratio (Nr), which represents the network behavior of atoms that form alkali/alkaline earth-aluminosilicate glasses that make up fly ashes. Nr is correlated to known composition-dependent features, including the glass transition temperature and amorphous XRD peak (“hump”) position. Analysis of heat release data and compressive strengths are used to evaluate the impact of fly ash compositions on reaction kinetics and on the engineering properties of cement-fly ash blends. It is shown that fly ashes hosting glasses with a high network ratio (i.e., having a less stable glass structure) are more reactive than others.
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