溶蚀作用下硅酸三钙水化产物微结构演变机理研究  

Microstructure evolution of hydration products of tricalcium silicate under dissolution

作　　者：李文伟 李曙光 李新宇 杨华美 LI Wenwei;LI Shuguang;LI Xinyu;YANG Huamei(China Three Gorges Corporation,Hydraulic Concrete Institute,Beijing 100038,China)

机构地区：[1]中国长江三峡集团有限公司水工混凝土工程技术研究室,北京100038

出　　处：《水利学报》2024年第4期449-455,共7页Journal of Hydraulic Engineering

基　　金：国家自然科学基金长江联合基金重点项目(U2040222);湖北省自然科学基金三峡联合基金重点项目(2023AFD183);湖北省自然科学基金三峡联合基金培育项目(2023AFD196);河南省引江济淮科研服务项目(HNYJJH JS FWKY-2021005)。

摘　　要：处于水下区的大坝混凝土由于钙离子溶出易遭受溶蚀破坏,从而造成水泥水化产物脱钙溶解,进而导致大坝混凝土性能劣化失效。为深入揭示大坝混凝土溶蚀劣化机理,有必要厘清溶蚀作用下水泥水化产物形貌与微结构的演变规律。硅酸三钙(C_(3)S)是水泥的主要矿物相,其水化产物特性对水泥及混凝土性能影响显著。为此,本研究制备了高纯度C_(3)S单体,加水水化后浸泡在不同浓度氯化铵溶液中模拟水泥水化产物的加速溶蚀,并结合热重分析、核磁共振、扫描电镜、氮吸附等微观测试方法对其溶蚀前后产物的组成、微纳观结构与形貌进行表征。结果表明硅酸三钙水化产物与氯化铵溶液发生中和反应,溶液的pH值升高;氯化铵浓度越大,反应后溶液的pH值相对越低、水化产物脱钙程度越大,证实了溶蚀程度与环境条件密切相关;溶蚀减少了水化产物中水化硅酸钙凝胶中的化学结合水含量,使硅链结构发生聚合、孔隙结构被粗化并加剧水化硅酸钙凝胶的空心程度,且结构和形貌变化程度随溶蚀程度的增加而增大,从微纳观尺度为揭示混凝土溶蚀机理提供了依据。The dam concrete in the underwater zone is susceptible to dissolution damage due to the leaching of calcium ions,which results in the decalcification and dissolution of cement hydration products,and further leads to the deterioration and failure of the dam concrete performance.To deeply reveal the deterioration mechanism of dam concrete,it is necessary to clarify the evolution law of the morphology and microstructure of cement hydration products under dissolution.As the main mineral phase of cement,the hydration product characteristics of tricalcium silicate(C_(3)S)significantly affect the performance of cement and concrete.Therefore,high-purity C 3S was prepared and then soaked in ammonium chloride solution with different concentrations after hydration,to simulate accelerated dissolution procedure of cement hydration products.The composition,micro-nano structure and morphology of the dissolved products were investigated by combining thermogravimetric analysis,nuclear magnetic resonance,scanning electron microscope and nitrogen adsorption.The results showed that the hydration product of C_(3)S was neutralized with the ammonium chloride solution,and the pH value of the solution increased.The lower pH value and more obviously decalcified of the hydration products after reaction with the increase of the concentration of ammonium chloride,demonstrated that the dissolution degree is closely related to environmental conditions.The dissolution would reduce the chemical binding water content of the hydrated calcium silicate(C-S-H)gel among cement hydration products,cause the polymerization of the silicon chain structure,coarsen the pore structure and intensify the hollowness of C-S-H gel.The deterioration degree of structure and morphology increased continuously with the increment of dissolution degree,which provides theoretical basis for explanation of concrete dissolution mechanism at micro-nano scale.

关 键 词：溶蚀 硅酸三钙(C_(3)S) 水化硅酸钙凝胶 化学结合水 硅核磁 微观形貌 

分 类 号：TV41[水利工程—水工结构工程]