1, the current pumping concrete slump can reach 20cm, expansion of more than 50cm. However, the density of each component in concrete is different, especially when the positive compatibility is poor, it is easy to cause the homogeneity of concrete deterioration, and even segregation, bleeding and compaction and other phenomena.
2, some admixtures (such as slag, fly ash) activity is very low, stable soil mixing station cement slurry less water absorption, and partially replace the cement filler can improve the particle size distribution, the gap between the cement particles Reduced, part of the filling water free out of the water out of the free water. Moreover, the greater the substitution amount of the admixture, the more obvious this effect; Admixture of the physical properties of the surface also has an important impact, the closer the ball particle admixture more prone to rotation and rolling, there will be more Free water out, so that slurry stability decreased, this situation is particularly obvious for admixture of slurry. At the same time most of the admixture than cement density is small, relatively light, easy to float layer.
3, if the aggregate of poor grading, large grained stones (particle size greater than 23mm) the proportion of the more specific surface area of the smaller aggregates, the amount of slurry required for the less aggregate, resulting in excess slurry surplus, Easy to cause segregation, bleeding phenomenon. The larger the proportion of small-grained stones (less than 10mm), the larger the specific surface area of the aggregate, which requires more slurry wrapped aggregate, concrete rheology is poor, and easy to cause bleeding phenomenon; needle content On the homogeneity of concrete have a great impact.
4, the concrete mix ratio If the amount of pulp is too large, too low sand rate, water-reducing admixture is too large are easy to lead to poor uniformity of concrete.
5, when the concrete fluidity is too large, especially for low-grade concrete easily lead to poor uniformity.
6, concrete mixing time is not easy to lead to poor uniformity of concrete.
7, concrete pouring process is not standardized, over-vibration are considered a deterioration, but also consider the special deterioration of external force, mixed with minerals in the ultra-fine powder is resistant to durability of the disease an effective technical means.
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