| PVA fiber reinforced cementitious composite(PVA-ECC) was obtained based on micro Mechanics under the guidance of the principle, through of fiber, matrix and the interface Between fiber and matrix of optimization design. Under uniaxial tensile loading, the tensile strain of PVA-ECC was more than 3%, with obvious strain hardening and multiple crack characteristics, crack width was less than 100μm, the realization of the harmless crack. Uniaxial tensile test was the most direct method to test whether PVA-ECC has strain hardening properties. The four point bending test was the most intuitive test method to show whether PVA-ECC has super high toughness. The influencing factors of the high toughness of PVA-ECC were studied by the above two methods, and the fracture morphology of PVA-ECC was studied, and the flexural toughness of PVA-ECC was evaluated.First, the effects of curing methods, fly ash content, water binder ratio, age and fiber content on the uniaxial tensile properties of PVA-ECC were studied by uniaxial tensile test, the results showed that:(1) Curing W of PVA-ECC specimen with higher strain and ultimate tensile strength, but the number of crack was less, crack width larger; Curing WA PVA-ECC out better tensile properties, ultimate strain was above 4%, with fine multi crack characteristics.(2)The PVA-ECC specimens with fly ash content of 70% showed high strength and high ductility, and showed multiple crack characteristics, with excellent crack control ability.(3) water binder ratio was 0.22 and 0.24 PVA-ECC showed good performance of strain hardening, The ratio of water to binder ratio of 0.22 PVA-ECC had higher initial crack strength than that of water cement ratio of 0.24. ultimate tensile strain and ultimate tensile strength was basically the same, But the water binder ratio of 0.22 PVA-ECC showed a more superior crack control ability.(4) with the extension of the age, the uniaxial tensile properties of PVA-ECC was gradually increased, especially at the age of 56 d, PVA-ECC in the initial crack strength, ultimate strength, ultimate strain and crack control ability achieved the best.(5) with the increase of the fiber content, the tensile properties of PVA-ECC increased gradually, and the tensile properties of the fiber content was 2%, which showed the most favorable and stable performance.Second, through the four point bending test of the thin plate, the influence of curing methods, fly ash content, water binder ratio, age and fiber content on the flexural properties of PVA-ECC were studied, the results showed that:(1) W and WM curing PVA-ECC specimens had a high limit span deflection and ultimate bending strength, the two showed similar bending performance, but the latter crack width was greater; in the curing of the WA, The limit span deflection and ultimate bending strength of PVA-ECC are decreased to a certain extent; three energy absorption capacity and flexural toughness index were also higher.(2) The PVA-ECC specimens with fly ash content of 60% and 70% showed a very high ultimate bending strength, but its limit span was less than 20 mm.; The limit bending strength of PVA-ECC with fly ash content of 80% was reduced, But it showed good bending performance and toughness index.(3) Water binder ratio was 0.22 and 0.24 PVA-ECC showed good bending performance, the two ultimate flexural strength are approximately the same, water cement ratio 0.24 PVA-ECC bending deformation capacity was better than the water cement ratio is 0.22 PVA-ECC. At the same time, the increase of water binder ratio, flexural toughness index increased.(4) With the extension of the age, the bending performance of PVA-ECC showed that the ultimate strength increased, and the deformation decreased, but the bending toughness index tended to be stable.(5) With the increase of fiber content, the flexural performance of PVA-ECC was gradually increased, When the fiber content is 2%, the bending performance was the most superior, showing a higher bending toughness index. |
PDF Full Text Request