烯类聚合物外加剂组织老化及其引致混凝土性能退化机理

Vinyl related polymers (VPs) are widely used as the viscosity-enhancing admixture, internal curing agent, and the other roles such as toughness improvement, cohesion increment, and et al. They form the tissues such as film and colloidal particle in the hardened concrete. Under the various service conditions where the VPs tissue in the concrete is easily aged, these meliorated functions from the VPs appearance may potentially be endangered, and also the various concrete performances are negatively affected. Unfortunately, the current research on the VPs mainly pays attention to the property improvement and the related assessment. Therefore the original physical characteristic, mechanical property and molecular structure of VPs, as well as physical characteristic, mechanical property and molecular structure of VPs in the hardened and service-life concrete will be studied. Besides, the hydrolysis reaction, chemical reaction, biological reaction, degradation reaction, cross-linking reaction and the mechanisms of these reactions in the hardening and service periods will be investigated in this project by various analysis technology and theoretical knowledge. Aging pattern and mechanism of VPs in the service period concrete will be built up. The performance and microstructure such as component phases, pores, cracks, ITZ structure of concrete under service period will be discussed, and the structures of VPs tissues will be also observed. Thus the pattern and mechanism of concrete property degeneration incurred from the tissue aging under the concrete service life will be accordingly revealed. These researches are carried out based on the previous study on the VPs aging under the conditions of 60±5℃. The implementation of this project helps take precaution against, lower and eliminate the aging of VPs in the concrete, and also the negative effects from VPs aging, improve the basic theories on VPs, modify for the current VPs, find the new VPs type, insure the safe service of concrete structure prepare with VPs. The results can also provide the technical and theoretical references for the modifying, finding of their new types and safe applications of the other concrete polymer admixtures.

烯类聚合物（VPs）以不同外加剂广泛应用于混凝土，在硬化混凝土中形成有别于传统无机相的VPs组织，其老化势必危及其改善功能，引致混凝土性能退化，威胁重大工程安全。但当前相关研究注重性能改善与评价，忽视VPs组织老化本征与条件，及其长期服役行为与作用。因此本项目拟在前期探讨聚丙烯酸组织老化基础上，采用多种表征技术，结合聚合物与混凝土学等知识，通过研究初始、硬化与服役期VPs物理性质与力学性能及分子结构的变化，水解、化学、生物、降解与交联等反应及机理，凝聚态结构变化及其机理，理清VPs组织老化规律及机理；研究硬化及服役混凝土性能与微观结构（如相组成、孔与裂缝、界面过渡区结构等）、VPs组织结构变化及其机理，阐明VPs组织老化引致混凝土性能退化规律及机理，完善VPs基础理论，为现有VPs改性，新型VPs研发，保证采用VPs制备混凝土结构服役安全，及其它有机外加剂改性、研发与正确使用提供科学依据。

本项目致力于以下四个主题的研究：典型烯类聚合物对新拌水泥基材料性能的影响规律及机理；典型烯类聚合物对水泥基材料的收缩效果的影响规律及机理；典型烯类聚合物在水泥基材料中老化规律；典型烯类聚合物在水泥基材料中老化机理。 .项目经过四年研究，实现了项目计划书设定的研究目标，达到了预期目的，发表学术论文35篇，培养研究生7名。.具体研究内容为：.PAM在常温下能较好的改善新拌水泥基材料的剪切粘度和保水性，降低流动性，且效果随着掺量的增加而显著，却随着温度升高而减弱。与PANA相比，PAM提高了水泥浆体的剪切粘度，降低了水泥浆体的流动性。然而，PANA更显著地降低了泌水率和水分蒸发损失率。PANA、HEMC和HPMC在20 °C下都可以不同程度改善水泥基材料的保水和泌水率，然而，在高温下不再显著。单掺少于0.10%SAP对流动度、剪切粘度和保水率影响较小，而泌水率随着SAP掺量的增加先增后减，但是能显著减少水泥浆体中的水分蒸发。SAP+PAM和SAP+PANA复掺对新拌水泥基材料性能的影响与单掺的叠加效果有关，尤其对泌水和保水性的改善由于单掺。.单掺PAM和PANA都促进了水泥浆体早期的水化、增大化学收缩、减小体积自收缩、干燥收缩和干燥失重，且这一效果在3 d之前较为显著，其中PAM优于PANA。单掺SAP延迟了水泥浆体早期的化学收缩，降低3-28 d 内的自收缩，也降低3 d之前的干燥收缩和干燥失重。复掺SAP+PAM和SAP+PANA对收缩性能的影响与单掺效果的叠加相关，因此复掺的减缩效果优于单掺。.随着水泥水化时间的延长，PAM从水泥浆体中的渗出率逐渐降低，且渗出的PAM分子量降低，酰胺基和羧基减少。PAM在水泥中的降解产物含有多种小分子量有机化合物，如醛类、醇类、酚类和脂类。SAP在水泥模拟孔溶液和水泥浆体中70 d后都能老化，老化产物的溶胀率、颗粒的粒径都显著变化，且在模拟孔溶液中的老化比去离子水中显著。老化后，SAP的酯基减少，羧酸盐基团改变，并且老化后的SAP颗粒不易吸水。