Construction Precast Development
Precast News From China
conpd0523 
Have you ever seen a concrete building collapse with a loud bang during an earthquake? Traditional concrete is like a compressed biscuit, extremely hard under compression, and prone to sudden fracture once stretched.
This phenomenon caused a painful lesson in the 2008 Wenchuan earthquake.
But now, a new material that can make concrete “bend over” is changing this situation.
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On November 21st, the national concrete price index recorded 90.
47 points, a month on month decline of 0.
33% and a year-on-year decline of 19.
47%.
The national market has entered the traditional off-season, and the overall market is characterized by generally weak demand and weak prices, with significant regional differentiation.
In the north, demand has shrunk significantly due to low temperatures, while in the south, prices are difficult to support due to insufficient demand or weather factors.
The specific demand and price situation in each region are as follows:.
Immediately stop tensioning: Remove the oil pressure as soon as possible and stop all tensioning operations.
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With the acceleration of urbanization, urban surface hardening has led to a decrease in rainwater infiltration capacity, causing environmental problems such as waterlogging and a decrease in groundwater level.
Therefore, building “sponge cities” has become a goal for more and more cities.
Permeable concrete, as a new type of eco-friendly building material, has a special pore structure that can effectively discharge surface water, alleviate urban heat island effect and waterlogging, and has been widely used in urban roads, squares, parking lots and other projects.
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Self compacting concrete was first proposed by Japanese scholar Okamura in 1986.
Its excellent workability, flowability, and uniformity are significant characteristics of self compacting concrete (SCC).
SCC can use its own gravity to fill the formwork without compaction or vibration, and the hardened surface is relatively smooth and flat.
Coarse aggregates usually account for 28% to 35% of the volume of SCC, significantly affecting its performance.
The rheological properties of self compacting concrete are largely influenced by the characteristics of coarse aggregates, including shape, particle size, gradation, surface features, etc.
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The blindness of construction, the asynchronous construction of the same individual project, and the large time difference in the formation of concrete structures in different parts have caused uneven settlement of the overall project and the formation of cracks.
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The phenomenon of partial mixing water floating to the surface of concrete during the setting process, accompanied by the sinking of granular materials, after pouring and vibrating the concrete mixture, is called bleeding.
A small amount of bleeding on the surface of concrete is a normal phenomenon and has no effect on the properties of the concrete mixture and after hardening.
However, excessive bleeding can bring many adverse consequences.
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It is reported that the lifting project of precast concrete columns for the 1 # three-dimensional warehouse undertaken this time has opened up a new field for the lifting of large warehouse concrete columns, breaking the weight record for lifting.
This hoisting of precast columns is different from the previous hoisting.
The traditional towers are mostly steel cylindrical structures, with uniform materials, concentrated center of gravity and regular shape; The precast concrete columns lifted this time have a large single weight (average weight of about 192 tons per column) and a long length (up to 40.
6 meters), which belong to brittle material components.
The surface is easily damaged and the internal stress is uneven.
In addition, the precision requirements for the reserved lifting points of the columns are extremely high.
Once the stress deviation occurs, it is easy to cause cracking, and the requirements for lifting stability and synchronization far exceed those of the tower.
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