萘磺酸盐甲醛缩合物毒害物质在水泥混凝土中渗出及稳定驻留机理

Naphthalene sulfonate formaldehyde (NSF) based superplasticizer is widely used in the production of cement concrete. NSF is the principal chemical component of the naphthalene-based superplasticizer. It is toxic substance, and may leak out from the cement concrete in the processes of concrete setting, hardening and service. The environmental safety of the relative people’s drinking engineering projects, such as water tower and pipe built with cement concrete, will be obsessed for the toxic NSF leaking. The sustainable uses of NSF based superplasticizer and cement concrete prepared with it will be also negatively affected. However, current researches on NSF based superplasticizer are mainly paid attention to its synthesis, performance improvement and evaluation. In view of these issues, the NSF leaking ratio and process, appeared speciation and distribution in the processes of concrete setting, hardening and service are discussed in this project based on the previous research on the NSF leaking from C30 cement concrete in the hardening process. The leaking and stable lingering patterns of NSF from and into cement concrete will be well built up. The processes and mechanisms of the NSF desorption, stripping, dissolution and diffusion, adsorption, wrapping, adhering, re-adsorbing, re-wrapping, re-adhering and resistance of dissolution and diffusion, also are investigated, and NSF leaking and stable lingering mechanisms are accordingly revealed. In this project, series of technologies related to the NSF analysis and characterization will be used, and the knowledge of physics, chemistry, surface physical chemistry and cement concrete will be employed. The implementation of this project helps take precaution against, lower and eliminate the NSF leaking from cement concrete in its setting, hardening and service processes, improve the basic theories on safe design and application of concrete, promote the sustainable development of NSF superplasticizer and environment, also provide the technical supports of environmental safety for other concrete admixtures contained with toxic component.

使用量大面广减水剂主要组成萘磺酸盐甲醛缩合物（NSF）毒害物质在水泥混凝土中渗出，威胁水泥混凝土水塔与水管等关系国计民生工程环境安全，困扰其可持续使用。但当前其相关研究注重合成、性能改善与评价，因此本项目拟在前期研究C30混凝土水养护过程中NSF渗出基础上，采用各种分析与表征技术，结合物理、化学、表面物理化学与混凝土学等知识，通过研究NSF在混凝土凝结硬化与服役期渗出率、渗出过程、存在形态与分布，理清NSF毒害物质在混凝土中渗出与稳定驻留规律；研究NSF解吸、剥离、溶解扩散过程与机理，吸附、包裹、粘附过程与机理，再次吸附、包裹、粘附过程与机理，及溶解扩散抵制机理，阐明NSF毒害物质在混凝土中渗出与稳定驻留机理，为防止、降低或消除NSF在混凝土中渗出造成环境污染，完善混凝土环境安全设计与应用基础理论，促进NSF高效减水剂可持续使用，其它含毒害组分水泥混凝土外加剂的安全生产与使用提供科学依据。

本项目致力于四个主题的研究：萘磺酸盐甲醛缩合物（NSF）在水泥混凝土凝结硬化与服役期渗出的规律及机理；NSF在水泥混凝土凝结硬化与服役期稳定驻留的规律及机理。.项目经过四年研究，全部实现了项目计划任务书设定的研究目标，达到了预期目的，发表SCI收录学术论文19篇，参加学术交流3次，培养研究生7名。.具体研究内容为：.NSF的渗出率随水灰比的增大而增大，并在水灰比0.5时渗出率达到58.2%。NSF在胶凝材料中渗出率的大小依次为粉煤灰、矿粉及水泥；在水泥凝结阶段，即0.5h-3h，随着时间延长，NSF的渗出率逐步减小，3h时为32.1%，7d时达到31%，最后逐渐趋于稳定，28d时为31%；NSF在未磨细水泥中的渗出率高于磨细水泥，并且随着水泥细度的减小NSF的渗出率增大；经过外加能量超声波处理后NSF在水泥中的渗出率明显增加。.NSF的吸附量随温度的升高而增多，60°C时最大可达9.00 mg/g。随时间的增加而增大，3h为6.09mg/g而后增长速率趋于稳定，28d时为7.01mg/g。矿粉对NSF的吸附量大于粉煤灰对其的吸附。在粉煤灰-水泥混合体系中，NSF的吸附量随粉煤灰掺量的增加先增大后趋于稳定。矿粉对NSF的吸附量一直增加，当矿粉为最大掺量70%时，NSF的吸附量为7.02 mg/g；NSF的吸附膜厚度随温度的升高而增长，温度为60°C时吸附膜厚度最大为6.70 nm。随时间的增加先增大，3h时的吸附膜厚度为4.63nm，而后趋于稳定，28d时的吸附膜厚度是5.70nm。.在水泥凝结阶段，钙矾石的含量连续增长。3h 时含量为1.85%，NSF的吸附量随之增加，渗出率减小；在硬化阶段，当吸附时间达到1d时，钙矾石含量为5.94%。随着C3S水化，无定形晶体含量持续增加，28d时无定形晶体含量为37.61%，水化产物的含量逐步趋于稳定，NSF的吸附量也逐步趋于稳定，渗出率逐渐趋于稳定。本项目通过研究得到了温度、时间、水灰比和胶凝材料的组成等对凝结硬化期NSF在水泥中的渗出与吸附的影响规律，并通过探究不同凝结硬化时间下水泥水化产物的演变，理清了NSF在水泥中的渗出与稳定驻留的机理，可为环境保护和后续工程研究提供技术支撑。