水化硅酸钙力学参数跨纳-微观尺度计算方法

为了准确高效地基于分子动力学模拟计算微观尺度高、低密度水化硅酸钙(C—S—H)的力学参数,选用7种常用的C—S—H晶体类似物结构和三种多孔介质力学模型进行对比分析研究。首先在纳观尺度通过分子动力学模拟得到C—S—H晶体类似物结构的体积模量、剪切模量、弹性模量和泊松比四个力学参数;并与第一性原理计算得到的结果进行对比,以此为基础,再应用多孔介质力学模型计算获得微观尺度高、低密度水化硅酸钙的相应力学参数;并与已有文献实测的高、低密度水化硅酸钙弹性模量进行验证。结果表明,与第一性原理计算相比,6种Tobermorite晶体结构模型的力学参数计算平均误差约20%; Jennite晶体结构模型计算平均误差达59%。采用C—S—H晶体类似物结构Tobermorite 14,结合Mehta或张俊彦的多孔介质力学模型进行模拟计算,效果最佳。C—S—H晶体结构类型对C—S—H跨纳-微观尺度力学参数准确性影响最大。提出的基于分子动力学模拟和多孔介质力学模型进行水化硅酸钙力学参数跨纳-微观尺度计算方法,避免了采用大规模分子动力学模拟获得高、低密度水化硅酸钙的微观力学参数,计算效率高且结果可靠。

Study on Nano-Micro Scale Calculation Method of Mechanical Parameters of Hydrated Calcium Silicate

In order to accurately and efficiently calculate the mechanical parameters of high and low density hydrated calcium silicate (C-S-H) at the microscale based on molecular dynamics simulation, seven common C-S-H crystal analogues and three porous media mechanical models were selected for comparative analysis. Firstly, the bulk modulus, shear modulus, elastic modulus and Poisson''s ratio of C-S-H crystal analogues were obtained by molecular dynamics simulation at the nanoscale, the results of which were compared with those calculated by first principles. On this basis, the mechnical parameters of high and low density hydrated calcium silicate of the microscale were obtained by the use of porous media mechanical models, which were verified with the elastic modulus of high and low density hydrated calcium silicate measured in the literature. The results show that, compared with the first principles calculation, the average error of mechanical parameters of six crystal models of Tobermorite is about 20%, and that of Jennite is 59%; When the structure of Tobermorite 14? is used and the porous media mechanical model of Mehta or Junyan Zhang is utilized, the simulation effect is the best; The structure type of C-S-H crystal has the greatest influence on the accuracy of nano-micro scale mechanical parameters of C-S-H; The nano-micro scale calculation method of mechanical parameters of calcium silicate hydrate based on molecular dynamics simulation and porous media mechanical models proposed, a large amount of calculation by molecular dynamics simulation to obtain the micro mechanical parameters of HD and LD C-S-H is avoided and the efficiency of the calculation method is high and the result is reliable.