Precast News From China
Concrete was the cornerstone of the ancient Roman Empire.
It not only propelled the far-reaching architectural revolution in Rome, but was also used to construct numerous buildings, bridges, and aqueducts.
Many of these structures are still in use today, dating back over 2000 years.
Why was ancient Roman concrete so durable?.
Concrete is an artificial stone made by mixing cement, aggregates (such as sand, stone), water, and admixtures (such as fly ash, slag, etc.
) in a certain proportion.
Its main performance includes strength, durability, and construction performance.
The strength of concrete is a comprehensive reflection of indicators such as compressive strength, tensile strength, and flexural strength; Durability involves resistance to freeze-thaw, permeability, and chemical erosion, among others; The construction performance includes characteristics such as fluidity, drop retention, and setting time.
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At present, artificial sand has become the mainstream fine aggregate in concrete preparation.
Its use not only makes up for the shortage of river sand, but also prevents the environmental damage caused by river sand mining.
However, a large amount of stone powder is generated during the production process of artificial sand, accounting for about 4% of the total production of artificial sand.
If the stone powder is not effectively utilized, it will cause environmental pollution risks and resource waste, and floating in the air will also harm people’s health and life.
Therefore, the resource utilization of stone powder is urgent.
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(1) The quality of the raw materials used is poor, manifested as unreasonable aggregate grading, excessive coarse aggregate, insufficient fine aggregate, improper aggregate size, excessive content of needle shaped particles, and poor quality of air entraining agents.
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Large volume concrete refers to concrete components with a single large volume, generally referring to concrete with a single volume of more than 1 cubic meter.
Large volume concrete is widely used in important infrastructure projects such as water conservancy hubs, large foundations, and bridges.
Compared with ordinary concrete, large volume concrete has significant temperature stress and shrinkage problems due to its larger block size, which can easily cause cracks and affect the quality and service life of the project.
Widely used in dams and ship locks in water conservancy and hydropower engineering, foundation slabs and transfer layers in industrial and civil buildings, and large bridge piers and abutments in bridge engineering.
Therefore, studying the influencing factors and effective preventive measures of cracks in large volume concrete is of great significance for improving the quality of large volume concrete engineering.
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This standard specifies the sampling and specimen preparation, mix performance testing methods, physical and mechanical performance testing methods, and long-term performance and durability testing methods for ultra-high performance concrete.
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Early cracks are the primary threat to the durability of concrete structures, which originate from stress exceeding limits caused by temperature deformation and shrinkage deformation constraints.
This article deeply analyzes the formation mechanism of early temperature and stress fields in concrete, and systematically discusses the comprehensive strategy of preventing cracks from the material source through mix proportion optimization.
The focus was on exploring the mix proportion methods to reduce hydration heat and optimize shrinkage performance, and the technical principles and applications of compensating shrinkage concrete (especially MgO expansion agent) were introduced.
The article emphasizes that “crack resistance” should be included as a key constraint condition in the multi-objective optimization design system of concrete mix proportions, to achieve the synergistic optimization of material performance, durability requirements, and economy.
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Concrete standard curing test blocks and curing test blocks under the same conditions are the core of strength testing and necessary inspection items for acceptance.
Many people may be confused: what is the difference between the two? What are their respective roles? Below is a clear comparison table for easy reference and mastery!.
The research and development of micro expansion UHPC is expected to solve the above-mentioned problems of UHPC under normal temperature curing conditions.
There is limited research on micro expansion UHPC in existing literature.
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