The tensile and flexural properties of polyvinyl alcohol （PVA） fiber reinforced ultra high toughness cementitious composite （UHTCC） were investigated. The composite, tested at the age of 14 d, 28 d and 56 d, shows...The tensile and flexural properties of polyvinyl alcohol （PVA） fiber reinforced ultra high toughness cementitious composite （UHTCC） were investigated. The composite, tested at the age of 14 d, 28 d and 56 d, shows extremely remarkable pseudo strain hardening behavior, saturated multiple cracking and ultra high ultimate strain capacity above 4% under uniaxial loading. Also, the corresponding crack widths are controlled under 50 um even at 56 days age. In the third point bending tests on thin plate specimens, the composite shows ultra high flexural ductility and multiple cracking on the tension surface. The high ultimate flexural strength/first tensile strength ratio of about 5 verifies the pseudo strain hardening behavior of UHTCC. SEM observation on fracture surfaces provides indirect evidence of optimal design for the composite.展开更多
Mechanical behaviors of UHTCC after freezing and thawing were investigated,and compared with those of steel fiber reinforced concrete（SFRC）,air-entrained concrete（AEC） and ordinary concrete（OC）.Four point bendin...Mechanical behaviors of UHTCC after freezing and thawing were investigated,and compared with those of steel fiber reinforced concrete（SFRC）,air-entrained concrete（AEC） and ordinary concrete（OC）.Four point bending tests had been applied after different freezing-thawing cycles（0,50,100,150,200 and 300 cycles,respectively）.The results showed that residual flexural strength of UHTCC after 300 freezing-thawing cycles was 10.62 MPa（70% of no freezing thawing ones）,while 1.58 MPa（17% of no freezing thawing ones） for SFRC.Flexural toughness of UHTCC decreased by 17%,while 70% for SFRC comparatively.It has been demonstrated experimentally that UHTCC without any air-entraining agent could resist freezing-thawing and retain its high toughness characteristic in cold environment.Consequently,UHTCC could be put into practice for new-built or retrofit of infrastructures in cold regions.展开更多
水泥基材料自身的低强、高脆性是引起开裂的主要原因,裂缝的形成和开展也加速了混凝土结构耐久性的劣化。在水泥基材料中引入高强高弹的聚乙烯醇纤维能够显著改善脆性,使其具有准应变硬化和多缝开裂特性。通过四点弯曲试验,研究养护条件...水泥基材料自身的低强、高脆性是引起开裂的主要原因,裂缝的形成和开展也加速了混凝土结构耐久性的劣化。在水泥基材料中引入高强高弹的聚乙烯醇纤维能够显著改善脆性,使其具有准应变硬化和多缝开裂特性。通过四点弯曲试验,研究养护条件(标养、水养)、基体的厚度和龄期对应变硬化水泥基材料组合结构的力学性能的影响。结果表明,标准养护优于水养,基体养护24h后浇筑砂浆有利于界面粘结和整体结构性能的发展,且20m m SH CC-砂浆组合试件的准应变硬化和多缝开展更显著,结构延性大幅度提高。此外,采用组合结构形式有利于应变硬化水泥基材料的推广应用。展开更多
基金Funded by the Hong Kong Research Grant Council( CERG UST6138/04E)the Key Program of National Natural Science Foundation of China( No.50438010)the Research & Application of Key Technology for the South-North Water Transfer Project Construction in China( JGZXJJ2006-13)
文摘The tensile and flexural properties of polyvinyl alcohol （PVA） fiber reinforced ultra high toughness cementitious composite （UHTCC） were investigated. The composite, tested at the age of 14 d, 28 d and 56 d, shows extremely remarkable pseudo strain hardening behavior, saturated multiple cracking and ultra high ultimate strain capacity above 4% under uniaxial loading. Also, the corresponding crack widths are controlled under 50 um even at 56 days age. In the third point bending tests on thin plate specimens, the composite shows ultra high flexural ductility and multiple cracking on the tension surface. The high ultimate flexural strength/first tensile strength ratio of about 5 verifies the pseudo strain hardening behavior of UHTCC. SEM observation on fracture surfaces provides indirect evidence of optimal design for the composite.
基金Funded by the Key Program of National Natural Science Foundation of China (No.50438010)
文摘Mechanical behaviors of UHTCC after freezing and thawing were investigated,and compared with those of steel fiber reinforced concrete（SFRC）,air-entrained concrete（AEC） and ordinary concrete（OC）.Four point bending tests had been applied after different freezing-thawing cycles（0,50,100,150,200 and 300 cycles,respectively）.The results showed that residual flexural strength of UHTCC after 300 freezing-thawing cycles was 10.62 MPa（70% of no freezing thawing ones）,while 1.58 MPa（17% of no freezing thawing ones） for SFRC.Flexural toughness of UHTCC decreased by 17%,while 70% for SFRC comparatively.It has been demonstrated experimentally that UHTCC without any air-entraining agent could resist freezing-thawing and retain its high toughness characteristic in cold environment.Consequently,UHTCC could be put into practice for new-built or retrofit of infrastructures in cold regions.
文摘水泥基材料自身的低强、高脆性是引起开裂的主要原因,裂缝的形成和开展也加速了混凝土结构耐久性的劣化。在水泥基材料中引入高强高弹的聚乙烯醇纤维能够显著改善脆性,使其具有准应变硬化和多缝开裂特性。通过四点弯曲试验,研究养护条件(标养、水养)、基体的厚度和龄期对应变硬化水泥基材料组合结构的力学性能的影响。结果表明,标准养护优于水养,基体养护24h后浇筑砂浆有利于界面粘结和整体结构性能的发展,且20m m SH CC-砂浆组合试件的准应变硬化和多缝开展更显著,结构延性大幅度提高。此外,采用组合结构形式有利于应变硬化水泥基材料的推广应用。
