碱-偏高岭土-矿渣复合胶凝体系物相组成演变规律及其与强度和体积稳定性间关系模型

Alkali-activated slag cement has excellent mechanical property and durability, however, volume stability of the material is poor due to its fast setting rate, so its application and development is restricted for a long time. Geopolymer cement from alkaline metakaolin has longer setting time, so it has better volume stability. Alkali- metakaolin- slag complex cementitious system is produced by blending of metakaolin and slag under the alkaline condition, systematic researches on evolvement rules of phase compositions and establishment of relation model between phase compositions and macro-properties have important significance for development and application of high performance alkali-active materials. In view of this, this paper is in order to establish mathematic models among composition, structure, strength and volume stability of alkali-active complex cementitious system through combined research methods of macroscopic tests, microscopic tests, theoretical analysis and mathematical modeling. The following research results will be obtained in this study: .(1) Evolvement rules of phase compositions in the Alkali- metakaolin- slag complex cementitious system; (2) Constant strength curve of three-component system of Alkali- metakaolin- slag and mathematical model between phase composition and strength; (3) Volume stability change rules of the system and volume stability mathematical model based on the capillary tube theory. Researches on these critical basic issues will provide theoretical foundation for research and application of alkali-active cementitious materials.

碱矿渣水泥具有优良的力学性能和耐久性能，但由于凝结速度快，体积稳定性差长期制约其应用发展，比较而言碱偏高岭土地聚合水泥凝结时间较长，体积稳定性较好。偏高岭土与矿渣复掺，在碱组分作用下，构成碱-偏高岭土-矿渣复合胶凝体系，系统研究体系物相组成演变规律，并构建其物相组成和宏观性能间的关系模型将对开发和应用高性能碱激发材料具有重要意义。鉴于此，本项目在前期碱矿渣水泥性能研究基础上，通过宏微观试验结合、理论分析和数学建模相结合的研究方法，构建碱激发复合胶凝体系组成、结构和强度及体积稳定性间的数学模型。将获得以下成果：（1）碱-偏高岭土-矿渣复合胶凝体系物相组成演变规律；（2）碱-偏高岭土-矿渣三元体系等强度曲线及物相组成与强度间的数学模型；（3）体系体积稳定性变化规律及基于毛细管理论的体积稳定性数学模型。通过这些关键性基础问题研究，将为碱激发类胶凝材料的研究和应用提供理论依据。

碱矿渣水泥和以偏高岭土为原料的地质聚合水泥是目前研究较多的两类碱激发胶凝材料。碱矿渣水泥主要以含钙类固态废弃物为主，硬化体强度高，但是收缩较大；而地质聚合水泥主要以硅铝酸盐矿物为主，硬化体收缩小，但是强度相对较低。将矿渣、偏高岭土复掺组成碱-偏高岭土-矿渣复合胶凝体系对开发和应用高性能碱激发材料具有重要意义。本项目将矿渣与偏高岭土复合制备碱激发胶结材，对该复合其力学性能及收缩性能进行研究，以期制备出一种抗压强度高、体积稳定性好的胶结材。研究揭示的主要规律有：① 不同碱金属阳离子对硅酸盐溶液及碱激发浆体粘度的影响；硅酸盐溶液的硅金属阳离子比值越低，硅酸根的聚合度越小。在硅酸钠溶液体系中掺入一定量的钾离子可以降低体系中硅酸根离子的聚合度，显著降低溶液和浆体的黏度，使碱矿渣水泥获得更好的工作性能。同时，在较低硅金属阳离子比（Si/M≤1.5）情况下，钾离子还能够延长体系的初凝时间。② 碱偏高岭土矿渣复合胶凝体系工作性及力学性能；碱偏高岭土矿渣水泥砂浆流动度和强度均随水玻璃模数和偏高岭土掺量增大而降低。凝结时间随偏高岭土掺量的增大而增加，随水玻璃模数增大逐渐增大。经过推导，发现碱偏高岭土矿渣水泥砂浆剪切应力与剪切速率呈线性关系。关系式中的屈服应力和塑性粘度均随偏高岭土掺量和水玻璃模数增大而增大。③水化硅铝酸钙（C-A-S-H）和水化硅铝酸钠（N-A-S-H）凝胶微结构组成；在碱激发复合中钙体系中，主要凝胶类水化产物的存在与体系中钙硅元素比值有关，当钙硅比小于0.6时，水化硅铝酸钙和水化硅铝酸钠凝胶在体系中共存；当钙硅比大于0.6时，体系中仅有水化硅铝酸钙存在。当钙硅比小于1.4时，随着钙硅比增大体系反应产物中低聚合度的结构单元及水化硅铝酸钙凝胶的含量增加，同时三维网络结构中高聚合度的结构单元含量降低；钙硅比大于1.4时，体系会形成二氧化硅凝胶。项目工作有助于更深层次了解碱激发中钙复合体系的结构组成和性能特点。