基于吸附层结构与空间构象演变机制的聚羧酸减水剂硫酸盐敏感度调控研究

Sulfate influences the adsorption behavior and dispersing capability of polycarboxylate superplasticizer (PCE), and impairs the rheological characteristics of ‘cement-water-PCE’ fresh system. Thus, sulfate is considered as a prominent factor of the compatibility between PCE and component materials in concrete, which has become one of the technical bottlenecks in the application of PCE in high performance concrete. This research focuses on the scientific problem of the intrinsic relationship between the parameters of PCE molecular structures and the adsorption-dispersing performance as well as sulfate sensitivity of PCE. Effects of sulfate on the rheological characteristics of the ‘cement-water-PCE’ fresh system are systematically analyzed, and the dynamic evolution process of the adsorption layer structure and the spatial conformation of PCE is investigated. Grey relational analysis is adopted to reveal the intrinsic discipline and the relationship between PCE molecular structure parameters and PCE adsorption structure as well as spatial conformation. Cluster analysis is applied to layout the coordination section of PCE molecular parameters concerning proper adsorption behavior and dispersing capability. Grey modeling methods are applied to construct the correlation model between PCE molecular structure parameters and sulfate sensitivity index. Based on practice and verification, the new design methods aiming at sulfate sensitivity control can be worked out. This research will provide scientific theory and methods for improving the adaptability of PCE in concrete.

硫酸盐作为影响聚羧酸减水剂与混凝土组成材料相容性的主要因素，显著削弱聚羧酸减水剂吸附-分散性能，已成为聚羧酸减水剂在高性能混凝土中应用技术瓶颈之一。本项目聚焦于聚羧酸减水剂分子结构参数与其吸附-分散性能以及硫酸盐敏感度内在关系这一科学问题。系统分析硫酸盐对聚羧酸减水剂吸附-分散性能的影响规律，探索聚羧酸减水剂吸附层结构与空间构象动态演变机制。采用灰色关联方法分析聚羧酸减水剂分子结构参数与其吸附层结构及空间构象关联规律，运用模糊聚类方法规划聚羧酸减水剂吸附-分散性能协同作用的分子结构参数区间，并通过灰色建模系统建立聚羧酸减水剂分子结构参数与硫酸盐敏感度关联分析模型。基于实践与验证，创建基于硫酸盐敏感度调控机制的聚羧酸减水剂构效优化设计科学方法，为提升聚羧酸减水剂与混凝土原材料相容性提供科学理论与方法。

硫酸盐影响聚羧酸减水剂适应性显著制约其在工程中应用。本项目研究了硫酸盐对聚羧酸减水剂吸附-分散性能影响机制并通过优化聚羧酸减水剂分子结构调控聚羧酸减水剂硫酸盐敏感性。结论如下：.（1）硫酸盐降低聚羧酸减水剂在水泥颗粒表面的吸附量，减薄水泥颗粒表面起分散作用的有效吸附层厚度，破坏水泥浆液双电层，削弱水泥颗粒表面静电斥力作用，降低聚羧酸减水剂对水泥浆体分散作用；随着硫酸根离子溶出率和溶出速率的增加，硫酸根离子与聚羧酸减水剂竞争吸附作用增强；同等硫酸根离子浓度情况下，碱金属离子的大量存在会促进硫酸根离子与聚羧酸减水剂竞争吸附作用，压缩聚羧酸减水剂水化直径，使得聚羧酸减水剂在浆液中的链构象发生聚集行为，从而减弱其空间位阻效应。.（2）优化设计聚羧酸减水剂分子结构参数，合成不同羧基密度、不同侧链长度及侧链接枝密度、不同主链官能团的聚羧酸减水剂，分析聚羧酸减水剂分子结构参数与其吸附-分散性能关联性。聚羧酸减水剂主链上羧基密度越高，其对水泥颗粒表面吸附量越大，对水泥浆体分散性越好，但羧基的强引气效应使得高羧基密度的聚羧酸减水剂显著削弱水泥砂浆密实性及力学强度。聚羧酸减水剂主链嵌入磺酸基可提高聚羧酸减水剂吸附-分散性能，促进水泥早期水化，而聚羧酸减水剂主链嵌入酯基或酰胺基则降低聚羧酸减水剂吸附-分散性能，延缓水泥早期水化。硅烷改性聚羧酸减水剂通过化学吸附作用提高聚羧酸减水剂吸附-分散效果。侧链长度长且酸醚比较大的聚羧酸减水剂表现出更好的吸附分散性能。.（3）综合分析聚羧酸减水剂分子结构与其硫酸盐敏感性关联性并优化设计聚羧酸减水剂提高聚羧酸减水剂与混凝土原材料相容性。通过增加聚羧酸减水剂主链酸醚比及侧链长度、利用γ-甲基丙烯酰氧基丙基三甲氧基硅烷部分取代主链羧基，通过自由基聚合法合成硅烷改性聚羧酸减水剂，可有效改善聚羧酸减水剂硫酸盐抵抗性能，提高聚羧酸减水剂适应性。