溶蚀作用下中热硅酸盐水泥净浆劣化机理  

Deterioration Mechanism of Moderate Heat Portland Cement Pastes Under Leaching

作　　者：马跃峰 金鸣 汤金辉 李文伟 刘加平[1,2] MA Yuefeng;JIN Ming;TANG Jinhui;LI Wenwei;LIU Jiaping(College of Materials Science and Engineering,Chongqing University,Chongqing 400045,China;School of Material Science and Engineering,Southeast University,Nanjing 211189,China;China Three Gorges Corporation,Hydraulic Concrete Institute,Beijing 100084,China)

机构地区：[1]重庆大学材料科学与工程学院,重庆400045 [2]东南大学材料科学与工程学院,南京211189 [3]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：《硅酸盐学报》2024年第11期3351-3360,共10页Journal of The Chinese Ceramic Society

基　　金：国家自然科学基金(52293430,U2040222,52379118)。

摘　　要：溶蚀是大坝混凝土不可忽略的耐久性问题。本工作对中热硅酸盐水泥(MHC)净浆、中热硅酸盐水泥-粉煤灰净浆和普通硅酸盐水泥(OPC)净浆进行加速溶蚀试验,通过强度测试、溶蚀深度、孔结构、X射线衍射、热重分析和硅谱固体核磁研究了溶蚀劣化机理。结果表明:与OPC净浆相比,MHC净浆水化产物中Ca(OH)_(2)含量更少,在溶蚀过程中具有更好的力学性能和更慢的溶蚀深度发展,因此抗溶蚀性更好。30%粉煤灰掺入降低MHC水化产物中Ca(OH)_(2)含量,并增加其孔隙率,但是降低了抗压强度下降率和孔隙增长率。溶蚀前后MHC净浆中C-(A)-S-H凝胶硅链长度大于OPC净浆,但其溶蚀后硅链增长率却较低。溶蚀后30%粉煤灰掺量的MHC净浆中C-(A)-S-H凝胶劣化程度最高,出现了层间交联并部分转变为硅胶。Introduction Moderate heat Portland cement(MHC)enhances early concrete strength,reduces hydration heat,and increases crack resistance,making it widely used for dam construction.Most dams located underwater therefore having to face to leaching issues.Prolonged concrete exposure to water leads to the dissolution of Ca(OH)_(2)from hydration products,thus decreasing internal alkalinity so as to cause the breakdown of ettringite,C-(A)-S-H,and clinker.The phenomena result in deterioration of mechanical properties and impermeability.Current research on the leaching of cementitious material mainly focuses on ordinary Portland cement(OPC)and its blends with mineral admixtures,while little attention is paid to MHC and moderate heat Portland cement-fly ash(MHC-FA)systems.The latter two MHCs are commonly employed in dam construction.In this work,leaching tests were conducted on MHC pastes and MHC-FA pastes.Comparison with OPC pastes system was further carried out,focusing on the evolution of leaching depth,deterioration of compressive strength,and the impact on phase composition and C-(A)-S-H structure.Methods Specimens with a water-to-cement ratio of 0.5 were prepared from MHC pastes(M0),MHC with 30%FA pastes(M30),and OPC pastes(P0).The size of the formed specimens was 40 mm×40 mm×40 mm.After curing in a standard concrete curing room for two years,five surfaces of the specimens were sealed with epoxy resin,leaving one surface exposed for accelerated leaching in a 5 mol/L NH_(4)Cl solution.The specimens were taken out from the solution after 7,14,28 d,and 56 d,following a test on compressive strength and leaching depth.The leaching depth is determined by spraying a 1%phenolphthalein solution in alcohol on the cut-open specimens.Samples were taken from areas 0-3 mm and 3-6 mm from the leaching exposure surface and pristine surface at 56 d.The thickness of 0-3 mm is labeled as the external layer of the leaching zone,and the thickness of3-6 mm is labeled as the internal layer of the leaching zone.Characterization techniques i

关 键 词：中热硅酸盐水泥 粉煤灰 溶蚀 结构和组成 水化硅(铝)酸钙凝胶 

分 类 号：TV431[水利工程—水工结构工程]