Effects of nanoclay addition on the permeability and mechanical properties of ultra high toughness cementitious composites  

纳米级粘土对超高韧性水泥基复合材料渗透性和力学性能的影响

作　　者：Min-jia WANG He-dong LI Qiang ZENG Qing-fen CHANG Xiu-shan WANG 

机构地区：[1]School of Civil Engineering and Architecture,Zhejiang Sci-Tech University,Hangzhou 310018,China [2]College of Civil Engineering and Architecture,Zhejiang University,Hangzhou 310058,China [3]Department of Architectural Engineering,Liaoyuan Vocational Technical College,Liaoyuan 136200,China

出　　处：《Journal of Zhejiang University-Science A(Applied Physics & Engineering)》2020年第12期992-1007,共16页浙江大学学报（英文版）A辑（应用物理与工程）

基　　金：Project supported by the National Natural Science Foundation of China(No.51978624);the Zhejiang Provincial Natural Science Foundation of China(No.LY19E080030);the Production and Construction Group’s Programs for Science and Technology Development(No.2019AB016);the Zhejiang Cultural Relics Protection Science and Technology Project(No.2014009);the 2017 Hangzhou Transportation Society Scientific Research Project(No.14);the First-class Disciplines Project of Civil Engineering in Zhejiang Province,China。

摘　　要：Tuning microstructures by adding nanoparticles is a promising way of improving the performance of cementitious composites.In this study,nanoclay was introduced to polyvinyl alcohol(PVA)fiber reinforced ultra high toughness cementitious composites(UHTCCs).The mechanical properties,crack patterns,water permeation resistance,and microstructures of UHTCCs with different dosages of nanoclay were studied.The addition of a proper dosage of nanoclay shows few effects on the compressive strength of UHTCCs,however,the compressive strength is decreased when an excessive amount of nanoclay is added.The flexural deformation capacity of UHTCCs is independent of nanoclay dosage,whereas the flexural strength generally decreases with an increasing dosage of nanoclay.Different cracking patterns were observed in the ultra high toughness cementitious composites containing nanoclay(NC-UHTCC)specimens subject to bending tests.A UHTCC with 1%(in weight)nanoclay shows the best water permeation resistance and the lowest water permeability.Variations in the mechanical properties and the water permeation resistance of UHTCCs containing different dosages of nanoclay could be ascribed to the synthetic effects of filling and heterogeneous nucleation of nanoclay at low dosages and the agglomeration effect of nanoclay at high dosages.This study is to optimize the water permeation resistance of UHTCCs,paving a path for the future application of UHTCCs in the fields of construction,decoration,and repair.目的:1.通过添加纳米级粘土以调节超高韧性水泥基复合材料(UHTCC)的微观结构,从而提高其抗渗性能。2.研究不同用量的纳米级粘土对UHTCC的力学性能、裂纹形态、孔结构、孔隙率及渗透性的影响规律,并阐释其抗渗机理。创新点:1.通过控制纳米级粘土的掺量,在不明显降低抗压强度的前提下,明显改善UHTCC的抗渗性能;2.通过综合分析孔结构、试件受弯裂缝和跨中挠度等,揭示粘土掺量对UHTCC的力学性能及抗渗性能的影响规律。方法:综合利用轴压试验、四点弯曲试验、抗渗试验、压汞试验和扫描电镜微观观测,系统分析纳米粘土用量对UHTCC的抗压强度、弯曲性能、孔结构及抗渗性能的影响,并尝试阐明抗渗性能提升机理。结论:1.添加质量分数为1%的纳米级粘土对UHTCC的抗压强度几乎没有影响;超过该用量,材料的抗压强度将随粘土用量的增加而逐渐降低;当纳米级粘土的添加量从0%增加到6%时,弯曲强度从约10 MPa降低到约6 MPa,但所有UHTCC的最大跨中挠度基本相同,约为5mm,说明适当掺量的纳米级粘土不会降低UHTCC的弯曲变形能力。2.添加了1%纳米级粘土的UHTCC的孔隙率最小(为31.75%),阈值孔径为183.13 nm,抗渗压力最大(为1.8 MPa),且渗透时间最大(为19 h);其优异的抗渗性能可归因于纳米级粘土的填充和异质形核效应。3.分散良好的纳米级粘土薄片使水分子渗透路径变得曲折,从而延长了渗水路程,但过量的纳米级粘土(>2%)会导致纳米团聚,并形成团簇缺陷,从而恶化抗渗性能。

关 键 词：NANOCLAY Water permeability Pore structure Cementitious composites Strain hardening 

分 类 号：TU525[建筑科学—建筑技术科学]