Construction Precast Development
Precast News From China
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Insufficient concrete strength is a common quality problem in engineering, which can directly reduce the load-bearing capacity and durability of the structure, and even cause safety hazards.
Its causes can be divided into four core dimensions, and corresponding targeted prevention and control measures can be taken.
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With the continuous expansion of infrastructure, the demand for raw materials for concrete is also increasing.
As one of the six major components of concrete, fine aggregate is in short supply.
However, in recent years, due to the scarcity of natural sand resources and environmental restrictions, its usage cost has become increasingly expensive.
Therefore, machine-made sand has been widely used, especially in Chongqing, where limestone resources are abundant.
Almost all commercial concrete mixing plants in the region are using machine-made sand for concrete production.
Mechanized sand is produced through mechanical crushing, with a controllable production process and minimal environmental pollution, while also protecting natural resources.
However, the quality of mechanism sand has many influencing factors on the production quality of concrete, such as fineness modulus, stone powder content, MB value, etc.
In the technical management process of commercial concrete mixing plants, it was found that the stone powder content and MB value fluctuated greatly, which had a significant impact on production quality control.
Therefore, it is necessary to study the influence of sand and gravel powder content and MB value on the performance of concrete.
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In order to strengthen the management of the entire process of concrete test blocks in high-speed railway projects, ensure the authenticity, representativeness, and traceability of concrete test block strength testing data, and in accordance with the “Railway Concrete Strength Inspection and Evaluation Standards” (TB 10425-2019), “High speed Railway Concrete Engineering Construction Quality Acceptance Standards” (TB 10752), “Railway Engineering Concrete Solid Quality Testing Technical Regulations” (TB 10433-2023), and the “Railway Construction Project Test and Testing Management Measures” (Tiejian [2023] No.
146) of China Railway Group, this management measure is formulated.
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Concrete cracks are the most common quality problem and a major area of complaints from property owners.
Cracks not only affect aesthetics, but can also seriously affect structural safety and durability.
The treatment of cracks cannot be repaired afterwards, and efforts should be made throughout the entire process of pre control, in-process control, and post disposal.
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After demoulding, the surface of the concrete is covered with large and small air holes, resembling the appearance of insect infestation.
Although it generally does not affect structural safety, both the client and the supervisor will require rectification, which is time-consuming and labor-intensive.
Below are the reasons for the formation of pores, prevention and control measures, and post repair plans.
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In recent years, the scale of basic construction in China has been continuously expanding, the construction speed has been rapidly increasing, and the amount of concrete used has been increasing.
While high-rise buildings are erected one after another, some problems have arisen due to uneven development, differences in concepts, outdated standards, and unclear responsibilities, even causing engineering quality accidents.
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The contractor shall operate and carry out civilized construction in accordance with the approved construction measures plan.
At the same time, strengthen quality and technical management, record, collect and organize data during the operation process, and regularly report to the supervisor.
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Due to the additional protective effect of the plaster layer on ordinary concrete structural components, even if the steel reinforcement protective layer does not meet the requirements, the risk of steel reinforcement corrosion will not significantly increase under general environmental conditions; Even if the steel bars are corroded, maintenance is relatively easy.
Without a plaster layer on the surface of plain concrete, the risk of steel corrosion will significantly increase when the thickness of the protective layer is insufficient; Once the steel bars corrode, repairing them is also quite difficult.
It is difficult to ensure that the appearance indicators such as surface color, texture, and flatness are consistent with the original surface during subsequent maintenance, which is a major challenge in the repair of plain concrete structural components.
In the past 20 years, many plain concrete structures have been constructed across the country, and their unique architectural shapes and natural decorative effects have added luster to urban landscapes.
But many of the surfaces of plain concrete structures have suffered durability damage and are facing the challenge of repair and treatment.
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After the completion of concrete pouring, when various participating units have doubts about the quality of the concrete, or before the completion of the project sampling inspection, it is necessary to conduct physical testing of various indicators of the concrete to verify whether it meets the requirements of various design indicators.
The specific number of tests will be determined based on the testing purpose and the actual situation of the project.
The main quality inspection index for concrete entities is compressive strength, and two commonly used methods are core drilling method and rebound method.
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In traditional concrete construction, formwork engineering accounts for one-third to half of the total cost and construction period.
3D printed concrete (3DPC) technology is expected to completely break free from template constraints and achieve free-form, low material consumption construction.
However, topology optimization (TO) – a recognized material efficiency “miracle” – often generates structures that are too complex and seriously disconnected from the strict process limitations of 3DPC, such as fixed extrusion width, continuous path, and minimum turning radius.
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