Estimating reaction kinetics of cementitious pastes containing fly ash
Estimating reaction kinetics of cementitious pastes containing fly ash
复制标题
粉煤灰水泥浆体反应动力学的估算
DOI：
10.1016/j.cemconcomp.2020.103655
复制
发表时间：
2020-09-01
影响因子：
10.5
通讯作者：
Weiss, W. Jason
中科院分区：
文献类型：
--
作者：
Glosser, Deborah;Suraneni, Prannoy;Weiss, W. Jason
本文提出了一种方法来估计水泥混合物中的主要粉煤灰玻璃态氧化物的反应动力学。该方法进行了比较，从多个独立的数据集的实验结果。动力学模型是基于速率限制步骤的各种氧化物和阶段使用的一般形式的一个广泛使用的模型为普通波特兰水泥（OPC）为基础的系统。模型中的经验参数是从文献中两种粉煤灰中玻璃氧化物的溶解研究中使用非线性优化算法拟合的。模型的输出提供了在非平衡条件下将反应动力学引入热力学模拟所需的输入。该模型是用来确定每个相的量，可以通过估计的溶解质量的每个主要的水泥相和粉煤灰玻璃氧化物在不同的年龄。这种方法能够精确建模预测固体水化产物（如氢氧化钙和钙钒石），孔溶液pH值，和孔溶液化学在任何年龄的任何OPC/粉煤灰系统。从模型和热力学计算的结果进行了比较，没有动力学约束的飞灰，假设100%的反应性的建模方法。假设100%飞灰反应性的反应产物的预测显着不同于实验值时，飞灰动力学模型不使用。当使用该模型时，预测得到了极大的改善。该模型可以作为未来建模工作的框架，并更新的经验参数作为额外的溶解研究和热力学数据变得可用。
This paper proposes an approach to estimate reaction kinetics for major fly ash glassy oxides in cementitious mixtures. The approach is compared to experimental results from multiple independent datasets. The kinetic model is based on the rate limiting step for various oxides and phases using the general form of a widely used model for ordinary portland cement (OPC)-based systems. The empirical parameters in the model were fit from dissolution studies for glass oxides in two fly ashes from literature using a nonlinear optimization algorithm. The outputs of the model provide the inputs needed to introduce reaction kinetics into thermodynamic simulations at non-equilibrium conditions. The model is used to determine the amount of each phase that can react by estimating the dissolved mass of each major cement phase and fly ash glass oxide at different ages. This approach enables accurate modeling predictions of solid hydration products (such as calcium hydroxide and ettringite), pore solution pH, and pore solution chemistry at any age for any OPC/fly ash system. Results from the model and thermodynamic calculations are compared to a modeling approach without kinetic constraints on the fly ash, assuming 100% reactivity. The prediction of reaction products made assuming 100% fly ash reactivity significantly differs from experimental values when a fly ash kinetic model is not used. Predictions are greatly improved when the model is used. The model can be used as a framework for future modeling efforts, and the empirical parameters be updated as additional dissolution studies and thermodynamic data become available.