2019-06-20 10:30:05

Study on the impact of PVA fiber length and content on engineering cement matrix composite performance impact

The effect of polyvinyl alcohol (PVA) fiber content and length on fluidity, flexural and compressive strength of engineering cement-based composite (ECC) was studied by table jumping test and flexural compressive strength test. Cementitious Composite (ECC) is a new kind of fiber reinforced cement-based material. The results showed that adding PVA fiber could reduce the fluidity and slump of ECC. Different PVA fiber lengths reduced ECC fluidity and slump, but there was no significant correlation between fluidity and fiber length. The addition of PVA fiber can significantly enhance the flexural strength of ECC. The larger the fiber content is, the more obvious the enhancement effect is; and the longer the fiber is, the greater the flexural strength is. The addition of PVA fiber reduced the compressive strength of ECC, but to a lesser extent.

Study on mixing uniformity of PVA fiber cement stabilized crushed stone

In order to study how to evenly disperse PVA fiber in cement stabilized crushed stone base material, our company has carried out a variety of mixing technology schemes to add PVA cement stabilized crushed stone mixing test. The uniformity of PVA fiber cement stabilized crushed stone is judged by the deviation coefficient of mass fraction ratio coefficient and mass fraction ratio coefficient. The results show that the mass fraction ratio coefficient of the mixture is generally larger than that of PVA fiber when the mass fraction ratio coefficient tends to be stable under different feeding sequence. From the perspective of mixing stability alone, the best feeding sequence of PVA fiber cement stabilized crushed stone is to put aggregate and PVA fiber bundle first, and then add cement and water to continue mixing. The mixing time when the mass fraction ratio coefficient deviation coefficient and the PVA fiber mass deviation coefficient value reach the minimum value increases with the increase of single stirring quantity and decreases with the increase of stirring speed. It is recommended that the optimal single-machine stirring volume V= 615l, the optimal stirring shaft rotation speed is omega = 48 r /min, and the optimal mixing time is 35s for wdz-600 type stable soil mixing station. Specific conclusions are as follows:

1) Under different feeding sequences, when the dispersion coefficient of mass fraction ratio coefficient of mixture tends to be stable, it is generally larger than the mass dispersion coefficient of PVA fiber. From the perspective of mixing stability alone, the optimal feeding sequence of PVA fiber cement stabilized crushed stone is to first put in aggregate and PVA fiber bundle to stir for 5 s, and then add cement and water to continue mixing, and the optimal mixing time is 30 s.

2) The mixing time when the mass fraction ratio coefficient deviation coefficient and the PVA fiber mass deviation coefficient value reach the minimum value increases with the increase of the single mixing volume. The optimal single mixing volume of wdz-600 stabilized soil mixing station is V = 0. 9V0. That is, V = 615 L, and its optimal mixing time is 35 s.

3) Mixing time when mass fraction ratio coefficient deviation coefficient and PVA fiber mass deviation coefficient reach the minimum value decreases with the increase of stirring speed. Considering mixing production efficiency and mixing quality, the optimal mixing shaft speed omega = 48 r /min, its optimal mixing time is 35s. Through comprehensive analysis of the influence of feeding order, single mixing amount and mixing speed on mixing uniformity of PVA fiber cement stabilized gravel, the optimal single mixing amount of wdz-600 type stabilized soil mixing station is V = 615l, the optimal stirring rotation speed of mixing shaft omega is ω = 48 r /min, and the best mixing time is 35s. Although the microdispersity of PVA fiber still needs to be further improved under different mixing process schemes, its distribution is relatively uniform from the macroscopic perspective.