Accurate prediction of microstructural evolution and ionic diffusivity in fly ash blended cement paste is significant for practical application and durability design of blended cementitious materials. This paper presents an integrated modelling framework for simulating 3D microstructure and effective ionic diffusivity of blended cement paste with various fly ash replacement levels and w/b ratios. A voxel-based hydration model using cellular automaton-like evolution rules was developed to simulate 3D microstructural development of fly ash blended cement, based on which the effective diffusivity was simulated using a lattice Boltzmann (LB) model for diffusion considering the contributions of both capillary pores and gel pores in C-S-H gels to ionic diffusion. A series of experiments were conducted to characterise the morphology of Portland cement and fly ash, hydration process and pore structure of fly ash blended cement paste and measure the effective ionic diffusivity. The simulation results agree well with experimental data in terms of hydration heat, calcium hydroxide content, degree of hydration of fly ash, porosity, and effective diffusivity, which suggests that the developed microstructure-based LB model for diffusion can predict the ionic diffusivity of fly ash blended cement paste with high accuracy. The addition of fly ash can help reduce the ionic diffusivity of cement paste particularly after the capillary porosity depercolation occurs due to the more tortuous diffusion paths in the pozzolanic C-S-H gels.

粉煤灰混合水泥浆中微结构演变和离子扩散率的准确预测对于混合水泥材料的实际应用和耐久性设计具有重要意义。本文提出了一个集成的建模框架，用于模拟具有不同粉煤灰替代水平和w / b比的混合水泥浆的3D微观结构和有效离子扩散率。建立了使用类似于细胞自动机的演化规则的基于体素的水化模型来模拟粉煤灰掺合水泥的3D微结构发展，在此基础上，考虑了两个毛细管的贡献，使用格子Boltzmann（LB）模型对有效扩散率进行了模拟CSH凝胶中的孔和凝胶孔会发生离子扩散。进行了一系列实验，表征了硅酸盐水泥和粉煤灰的形态，粉煤灰掺合水泥浆的水化过程和孔结构，并测量了有效的离子扩散率。模拟结果与水化热，氢氧化钙含量，粉煤灰的水合度，孔隙率和有效扩散率等方面的实验数据吻合良好，表明所建立的基于微结构的扩散LB模型可以预测粉煤灰的离子扩散率。粉煤灰混合水泥浆，精度高。粉煤灰的添加可以帮助降低水泥浆的离子扩散性，尤其是在由于火山灰CSH凝胶中较曲折的扩散路径而导致毛细孔孔隙率减渗之后。粉煤灰掺合水泥浆的水化过程和孔结构，并测量有效离子扩散率。模拟结果与水化热，氢氧化钙含量，粉煤灰的水合度，孔隙率和有效扩散率等方面的实验数据吻合良好，表明所建立的基于微结构的扩散LB模型可以预测粉煤灰的离子扩散率。粉煤灰混合水泥浆，精度高。粉煤灰的添加可以帮助降低水泥浆的离子扩散率，尤其是在由于火山灰CSH凝胶中较曲折的扩散路径而导致毛细孔孔隙率减渗之后。粉煤灰掺合水泥浆的水化过程和孔结构，并测量有效离子扩散率。模拟结果与水化热，氢氧化钙含量，粉煤灰的水合度，孔隙率和有效扩散率等方面的实验数据吻合良好，表明所建立的基于微结构的扩散LB模型可以预测粉煤灰的离子扩散率。粉煤灰混合水泥浆，精度高。粉煤灰的添加可以帮助降低水泥浆的离子扩散性，尤其是在由于火山灰CSH凝胶中较曲折的扩散路径而导致毛细孔孔隙率减渗之后。孔隙率和有效扩散率，这表明所开发的基于微结构的LB扩散模型可以高精度地预测粉煤灰掺合水泥浆的离子扩散率。粉煤灰的添加可以帮助降低水泥浆的离子扩散性，尤其是在由于火山灰CSH凝胶中较曲折的扩散路径而导致毛细孔孔隙率减渗之后。孔隙率和有效扩散率，这表明所开发的基于微结构的LB扩散模型可以高精度地预测粉煤灰掺合水泥浆的离子扩散率。粉煤灰的添加可以帮助降低水泥浆的离子扩散性，尤其是在由于火山灰CSH凝胶中较曲折的扩散路径而导致毛细孔孔隙率减渗之后。