混凝土中水化硅酸钙(C-S-H)凝胶微纳结构与力学性能的计算化学研究

依靠经验模型和对比试验进行水泥基材料设计的传统方法已经成为制约混凝土可持续发展的瓶颈，揭示混凝土材料中水化硅酸钙(C-S-H)凝胶的化学微结构是突破这一难题的关键。本项目拟采用多尺度量子化学计算和分子动力学模拟，以水泥熟料的水化反应为起点，深入探索生成C-S-H凝胶的原位反应机理。在充分前期研究基础上，提出基于钙硅比演变规律的C-S-H介观模型构筑方法，实现对C-S-H化学组成、成键结构（硅氧链、氢键、离子）、表界面结构及其宏观力学性能的a priori预测。系统研究钙硅比、水灰比、水化时间、外加剂掺杂、碳化、严酷服役环境等对C-S-H微结构的影响，建立C-S-H胶凝体系的本构关系模型，探索基于微观C-S-H分子结构的混凝土宏观力学性能调控理论。

The empirical or semiempirical trial-and-error approaches for the design of concrete admixtures are the bottleneck for the significant improvement of the performance of modern concrete for sustainable infrastructure development. It is extremely critical to reveal the chemical structures of the calcium silicate hydrates (C-S-H), which is the most important hydraulic complex in cement. This project is to investigate the microscopic structures of the C-S-H gel using the ab initio methods and molecular dynamics simulations. Starting from the hydration reactions of C3S and C2S, the mechanisms for the in situ formation of C-S-H gel will be revealed step by step. The nanocrystal structures of C-S-H will be established on the basis of the transformation of tobermorite to jennite crystallines. It is aimed at obtaining a priori predictions for the chemical composites, bonding structures (Qn, silicate chains, hydrogen bonds, and Si/Ca-OH), surface/interface structures, and mechanical properties of the C-S-H gels without any empirical parameters. Dependence of the structures of C-S-H on the C/S, W/C, hydration time, additives, carbonation, and the external environment will be examined systematically. The growth kinetics and dynamics of the C-S-H gel clusters will be illustrated and the structure-activity relationship will be obtained to shed new lights on the rational design of the hydraulic structural concrete formulations.