基于磁性2D材料的C-S-H凝胶有序微结构调控及混凝土增韧机理

混凝土材料脆性大、韧性差的根源在于其各组分自身具有硬脆属性，且在微结构中呈无规则分布。针对微结构的有序度提升这一难题，本项目以混凝土浆体主要成分水化硅酸钙（C-S-H）凝胶为研究对象，借助贝壳的“砖-泥”层状结构思想，开创性地以磁性石墨烯为2D模板材料，在外加磁场的作用下主动调控C-S-H的生长方向，制备C-S-H凝胶高度有序层状结构。随后将其应用与水泥混凝土浆体中，“自下而上”诱导水化产物的定向生长，从根源上提高混凝土材料的宏观韧性。综合采用偏光显微镜、透射电镜、聚焦离子技术等先进测试方法表征磁性石墨烯在磁场作用下的定向偏转行为，阐明磁性石墨烯与C-S-H凝胶界面作用机理，建立石墨烯磁化程度、溶液粘度、磁场施加参数与C-S-H凝胶成核-生长-搭接的定量关系，提出基于有序C-S-H凝胶层状结构的水泥混凝土微结构调控方法并建立多尺度增韧本构模型，为混凝土材料的本征增韧提供新的思路和方法。

The root cause of the high brittleness and poor toughness of concrete materials is related to 1) the intrinsic brittle properties of each component, and 2) their randomly distribution in the microstructure. Aiming at the key challenge of improving the order degree of microstructure, this project takes the hydrated calcium silicate (C-S-H gel), the main component of concrete, as main research object. Inspired from the “brick-mud”layered structure of shells, we creatively utilize magnetic graphene as a 2D template material and apply an external magnetic field, to actively control the growth direction of C-S-H in order to produce a highly ordered layered structure of C-S-H gel. Then it is applied in cement and concrete systems, induce the oriental growth of hydration products from “bottom-up”, intending to improve the macro toughness of concrete from its genes. Combine polarizing microscope, transmission electron microscope, focused ion beam and other advanced techniques to characterize the directional deflection behavior of magnetic graphene in magnetic field, elucidate the interaction mechanism between the magnetic graphene and the C-S-H gel, and establish the quantitative relationship between the graphene magnetization, solution viscosity, magnetic field application parameters and C-S-H gel nucleation-growth-lap, propose a new method for controlling the microstructure of cementitious materials based on ordered C-S-H layered structure and establish a multi-scale toughening constitutive model. The achievements of this project will provide new ideas and methods for the intrinsic toughening of concrete materials.