1.The current pumping concrete slump can be up to 20 cm, extension degree more than 50 cm. But in the concrete density, especially outside the positive compatibility is poor, easy cause for variation of concrete homogeneity, and even the phenomenon such as segregation, exudation and harden.
2.Some admixtures (such as slag, fly ash) activity is low, the stabilized soil mixing station suction in cement paste is less, partly replacing cement and admixtures can improve particle size distribution, reduce the gap between the cement particles, partly filled water flow become free water out. And admixtures to replace, the greater the amount of this effect, the more obvious; Admixture of surface physical properties have an important influence, admixture particles is more close to the ball when more prone to turning and rolling, the more free water secretion, decreased stability of the slurry, this kind of situation for mixed with admixture slurry is especially obvious. Admixtures were smaller than the cement density at the same time, the comparatively light, and easy to buoyancy stratification.
3.If the aggregate gradation, the big stones (particle size greater than 23 mm) ratio, the more of the aggregate, the smaller the specific surface area, the less parcel paste volume needed for aggregate, cause excessive surplus slurry, easy to segregation and bleeding phenomenon. Small particle stones (diameter less than 10 mm) ratio, the more the greater the specific surface area of aggregate, it needs more slurry aggregate, concrete rheological property is poor, and easy to cause bleeding phenomenon; The needle flake content also for have a great influence on concrete homogeneity.
4.Concrete mixture ratio if the amount is too large, low sand ratio, dosage of water reducing agent is too large for bad easily lead to concrete homogeneity.
5.When concrete liquidity is too large, especially for low and medium grade of concrete for bad easily lead to homogeneity.
6.Concrete mixing time enough for bad easily lead to concrete homogeneity.
7.Concrete pouring process is not standard, excessive vibration is considered a degradation function, but also outside the special degradation.
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Post time: Jul-31-2017