Construction Precast Development
Precast News From China
When the daily average outdoor temperature is below 5 ℃ for 5 consecutive days, or the daily minimum temperature is below 0 ℃, it enters the category of “winter construction”.
At this time, concrete is most prone to “early freezing damage”: the volume of water freezing expands by about 9%, forming microcracks inside.
Even if it is later subjected to normal temperature curing, its strength can never be restored to its unfrozen level.
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The test section is located on the B ramp of the Lukou Interchange in Section B of the Nanjing New Airport Expressway (BK0+080-BK0+180), which is a connecting road between Lukou Development Zone and Ningli Highway.
The roadbed width is 19 meters, the pavement width is 14.
4 meters (2 × 7.
2 meters), the central divider width is 1.
6 meters, and the soil shoulder width is 1.
5 meters.
The total length of the test road is 100 meters, and the pavement width is 7.
2 meters (single width).
Use post tensioning method for construction.
The test road was completed on June 30, 1997, and the testing work will be carried out regularly for a long time.
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As an experienced engineer who has been working on bridge construction sites for decades, I am well aware that the appearance quality of precast T-beams is not only a facade project, but also a direct reflection of their internal quality.
A T-shaped beam with a smooth appearance and uniform color often means that its internal quality can withstand the test.
The beams with honeycomb and pockmarks on the surface and staggered cracks may also have hidden quality hazards.
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[Example 1] The high temperature of cement causes rapid loss of concrete slump.
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Ultra high performance concrete (UHPC) is a new type of cement-based composite material with ultra-high strength, ultra-high toughness, and ultra-high durability.
In the national standard “Ultra high Performance Concrete” (GB/T 31387-2025), it is officially defined as fiber-reinforced ultra-high strength concrete produced by using cement and mineral admixtures as cementitious materials, combined with aggregates, additives, high-strength micro steel fibers and/or non-metallic fibers, water, etc.
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I believe many friends have doubts about the retention of concrete test blocks for cast-in-place piles.
Here, I have consulted relevant specifications and excerpted the following:.
Concrete enterprises are mainly engaged in the production of commercial concrete and commercial mortar.
They must have certain hardware facilities (production line equipment, green environmental protection facilities, etc.
) and qualified technical personnel, and obtain the “Construction Enterprise Qualification Certificate” issued by the local government construction commission department before they can carry out product production and sales.
It plays a positive role in optimizing the comprehensive utilization of building materials resources, improving the quality of concrete products, and strengthening environmental protection in the basic construction of national roads and bridges and real estate development and construction.
There are many different grades of concrete products according to different formulas, such as C30, C40, C50, C60 and other series of products.
The sales price is mainly determined by the production cost, so its cost accounting and control determine the operating results and development momentum of the enterprise.
Abstract: The performance of concrete is influenced by various factors, especially the addition of active silica fume, which can effectively improve its performance and extend its service life, thus improving the quality of engineering.
This article reviews the effects of silica fume and its mixed additives on the durability and mechanical properties of concrete, and looks forward to the research prospects of silica fume on improving concrete performance.
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In today’s development of concrete technology towards high-strength, high-performance, and high fluidity pumping construction, it is necessary to explore the regularity of the relationship between the various elements in the concrete mix proportion and the workability, strength, and long-term performance of concrete.
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The generation and existence of bubbles on the surface of concrete not only affect the aesthetics of the project, but more importantly, it reflects that the quality of the project has not yet reached the standard specifications.
How to eliminate surface bubbles in concrete is a common and difficult problem encountered by many technicians and supervisors.
Therefore, engineering and technical personnel should pay sufficient attention to it.
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