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According to the clear provisions of the national standard “Ultra High Performance Concrete”, the mechanical performance classification criteria for Ultra High Performance Concrete (UHPC) are as follows: its compressive strength is divided into six grades, UC100 to UC200, based on its performance; Meanwhile, the tensile strength is divided into six grades, UT5 to UT13.
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The phenomenon of hard shell in concrete is mainly due to the rapid evaporation of surface moisture, combined with the influence of admixture components and construction operations, resulting in surface hardening while the interior has not yet set.
I have sorted out the specific reasons and solutions for you:.
The core technique for determining the state of concrete is to accurately identify whether the concrete meets the construction requirements (such as pumping, pouring, and vibration) through the detection and evaluation of “flowability cohesiveness water retention”.
The so-called “state” refers to workability (fluidity, cohesiveness, water retention), and the following core techniques are tested through practical experiments, judged by experience, and scientifically verified, suitable for trial and error .
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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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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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