Na^+和K^+对水泥基材料早期收缩性能的影响  

Influence of Na+and K+on the early-age shrinkage properties of cement-based materials

作　　者：何真[1] 李洋[1] 蔡新华[1] 陈晓润[1] HE Zhen LI Yang CAI Xinhua CHEN Xiaorun(State Key Laboratory of Water Resources ＆ Hydropower Engineering Science, Wuhan University, Wuhan 430072, Chin)

机构地区：[1]武汉大学水资源与水电工程科学国家重点实验室,湖北武汉430072

出　　处：《水利学报》2016年第11期1345-1351,共7页Journal of Hydraulic Engineering

基　　金：国家自然科学基金项目(51379163);科技部973项目(2013CB035901;2015CB655101)

摘　　要：利用压汞、纳米压痕以及27Al固体核磁共振方法,系统研究了不同碱金属离子(Na^+和K^+)与含量对水泥基材料早期自收缩和干燥收缩性能的影响规律。结果表明,超量的Na^+或K^+均促进了水泥基材料早期自收缩和干燥收缩,但K^+的促进作用明显大于Na^+,其机制在于:(1)K^+比Na^+更易促进水泥基材料中小于50纳米孔数量的增加,这使得超量K^+水泥基材料在干燥时具有更大的收缩驱动力;(2)虽然K^+比Na^+更易促进水泥基材料生成高密度水化硅酸钙(HD C-S-H),但同时超量K^+水泥基材料中C-S-H总量也较高,大量的C-S-H是导致较高早期收缩的根源;(3)与Na^+相比,K^+更明显地阻碍了钙矾石(AFt)晶体的形成,削弱了AFt的骨架作用,且K^+可促使AFt向单硫型水化硫铝酸钙(AFm)转变,因而导致超量K^+水泥基材料更易发生收缩变形。The influence of the different metal ions（K^＋and Na^＋） and alkali content on autogenous shrink-age and drying shrinkage at early age has been investigated through mercury intrusion porosimetry（MIP）,nanoindentation and27 Al magic angle spinning nuclear magnetic resonance（27Al MAS NMR）. The results in-dicate that the autogeneous and drying shrinkage of cement-based materials are increased by K^＋or Na^＋,whereas the effect of K^＋is much more obvious. The mechanisms of these phenomena are attributed to threereasons：（1） the capillary pores less than 50 nm in cement-based material with high K^＋content are morethan those with high content Na^＋, leading to a higher driving force when shrinkage occurs;（2） K^＋tendsto promote the formation of high density calcium silicate hydrate（HD C-S-H）, but the total content ofC-S-H in cement-based material with high K^＋content is higher than the one with high Na^＋content, andthe large amount of C-S-H is primary cause of high early-age shrinkage; and（3） K^＋is easier to hinderthe formation of AFt and accelerate the transformation of AFt to AFm than Na^＋at early age, leading tothe weak framework function of AFt. The cement-based material with high K^＋content has more shrinkagevalues at early-age.

关 键 词：收缩 碱类型 孔结构 水化硅酸钙 纳米压痕 核磁共振 

分 类 号：TV42[水利工程—水工结构工程]