偏高岭土对高流动性钢纤维混凝土早期力学性能和细观结构的影响  

Effect of Metakaolin on Early Mechanical Property and Microstructure of High Fluidity Steel Fiber Reinforced Concrete

作　　者：于子豪 张彤炜 崔科旺 YU Zihao;ZHANG Tongwei;CUI Kewang(Key Laboratory of Mechanics on Disaster and Environment in Western China,The Ministry of Education of China,Lanzhou University,Lanzhou 730000,China;College of Civil Engineering and Mechanics,Lanzhou University,Lanzhou 730000,China)

机构地区：[1]兰州大学西部灾害与环境力学教育部重点实验室,兰州730000 [2]兰州大学土木工程与力学学院,兰州730000

出　　处：《硅酸盐通报》2021年第9期2911-2920,共10页Bulletin of the Chinese Ceramic Society

基　　金：国家重点研发计划(2018YFC1504700,2019YFC1806004);中国博士后科学基金面上项目(2019M653791);甘肃省自然科学基金面上项目(20JR5RA259);中央高校基本科研业务费专项资金自由探索项目(lzujbky-2020-pd08)。

摘　　要：为了提高泵送混凝土流动性及早期力学性能,降低水泥用量,本文研究了高流动性偏高岭土和钢纤维复合混凝土的流动性、抗压和抗拉强度、弹性模量、破坏形态和微观结构,并在此基础上评价了偏高岭土和钢纤维对混凝土性能的影响。结果表明,随着钢纤维和偏高岭土含量的增加,浆体的流动性降低,偏高岭土影响更加显著。偏高岭土提高了钢纤维混凝土养护7 d后的抗压强度、抗拉强度和弹性模量,钢纤维对残余拉伸强度和裂纹扩展有明显的影响。通过扫描电镜(SEM)观察与X射线衍射(XRD)分析,偏高岭土的添加使试样内部产生了更稳定的水化硅酸钙(CSH)凝胶、单硫型水化硫铝酸钙(AFm)和高硫型水化硫铝酸钙(AFt)等物质。这些产物减少了孔隙和缺陷的产生,增强了界面过渡区的粘结力。由于偏高岭土和钢纤维对和易性的影响机制分别为增加黏度和提升浆体的抗剪切能力,本质上都为阻碍各组分的相对运动,所以二者在降低混凝土流动性方面具有耦合作用。偏高岭土与钢纤维影响混凝土力学性能的阶段不同,前者在未开裂阶段,后者在开裂阶段。To improve the workability of the pumped concretes at early curing stage,which are normally used in driven cast-in-place piles,this paper investigated the fluidity,compressive and tensile strength,elastic modulus,destruction morphology and microstructure of high fluidity metakaolin(MK)and steel fiber(SF)concrete.Then,the effects of metakaolin and steel fiber on concrete properties were evaluated.The results show that the fluidity of the paste decreases with the increase of steel fiber or metakaolin respectively.As metakaolin contents increased,the increment of metakaolin dominates the fluidity of concrete,and the effect of steel fiber is not evident.The compressive strength,tensile strength and elastic modulus after 7 d curing increase with SF or metakaolin respectively,and metakaolin is the key factor effecting the strength of high fluidity MK-SF concretes.Whist the residual tensile strength and crack development are significantly dominates by steel fiber.From the scanning electronic microscope(SEM)images and X-ray diffraction(XRD)spectrogram,more stable hydrated calcium silicate(CSH)gel,monosulfide calcium sulphoaluminate hydrate(AFm)and polysulfide calcium sulphoaluminate hydrate(AFt)are produced by metakaolin addition.These products reduce the porosity and defects,and strengthen the bonding in interfacial transition zone.The metakaolin and steel fiber increase the viscosity of paste and the shear resistance of interfaces,which is essentially to hinder the relative movement of each component.Then,they have a coupling effect on reducing the fluidity of concrete.The mechanisms of metakaolin and steel fiber influencing the mechanical behavior of concretes are different.Generally,the steel fiber effects the cracking stage and the metakaolin influences the non-cracking stage in strain-stress curves.

关 键 词：偏高岭土 钢纤维 高流动性混凝土 力学性能 微观机制 

分 类 号：TU528[建筑科学—建筑技术科学]