02 high strength concrete high strength concrete is a concrete that uses ordinary cement and sand as raw materials, adopts conventional production technology, mainly relies on high-range water reducer, or adds a certain amount of active mineral admixture at the same time, so that the strength grade after hardening is not lower than C60.
High performance concrete has low water consumption, good fluidity, high segregation resistance and excellent filling performance.
1) Good self compacting.
It means that the concrete mixture has a certain ability to keep water from bleeding out.
Long press to enter the clean park book store welcome message concrete, known as artificial rock, which is often called artificial concrete.
2) Disadvantages of high-strength concrete ① high-strength concrete is easy to be affected by environmental conditions in all aspects of construction, so it requires high quality management level in its construction process.
4) The heat of hydration is low.
These properties determine the durability of concrete, so it is called durability.
② High strength concrete is dense and hard.
Since the water cement ratio of high-performance concrete is low, the hydration reaction will be terminated earlier, so the hydration heat will be correspondingly reduced.
Durability of concrete refers to the ability of concrete to resist the action of environmental media and maintain its good performance and appearance integrity for a long time.
As one of the important building structural materials, concrete needs to know its characteristics.
In short, the durability of concrete includes impermeability, frost resistance, corrosion resistance and carbonization resistance.
High performance concrete will crack and peel off under high temperature.
Admixtures used in high-performance concrete must comply with gb8076 concrete admixtures and gb50119 technical specification for application of concrete admixtures, and be harmless to concrete and reinforcement.
(2) Physical and mechanical properties of high strength concrete 1) compressive properties.
Part II special concrete 01 high performance concrete high performance concrete (HPC) is a new type of high-tech concrete.
There are several special types of concrete, including high-performance concrete, high-strength concrete, light aggregate concrete, porous concrete, waterproof concrete, fiber concrete and polymer concrete.
1) Select high-quality and qualified cement and coarse and fine aggregate.
6) Less creep.
③ For prestressed reinforced concrete components, high-strength concrete can apply greater prestress and prestress earlier, and reduce prestress loss due to creep because of its large stiffness and small deformation.
Mineral admixtures with certain potential activity or pozzolanic activity shall be selected, such as silicon powder, fly ash, ground slag powder, natural zeolite powder, metakaolin powder and composite fine powder.
It refers to the performance of concrete mixture flowing under its own weight or construction vibration and filling the model evenly and compactly, which is expressed by slump.
It is a comprehensive concept, including impermeability, frost resistance, corrosion resistance, carbonization, alkali aggregate reaction and reinforcement corrosion in concrete.
Because of its good self compactness, it will explode and break when encountering high temperature and fire, that is, it is afraid of fire and high temperature.
1) Advantages of high-strength concrete ① high-strength concrete can reduce the structural section, reduce the amount of reinforcement, increase the usable area and effective space of the house, and reduce the foundation load.
(3) Water retention.
This kind of concrete is especially suitable for high-rise buildings, bridges and buildings exposed to harsh environments.
The selected mineral fine powder must be harmless to concrete and reinforcement and meet the requirements of relevant quality standards and technical specifications.
3) High strength.
Compared with ordinary strength concrete, the total creep of high-performance concrete (the sum of basic creep and dry creep) is significantly reduced.
3) Select fine powder.
Any fact has two sides.
In addition to the general frost resistance and permeability of high-performance concrete, the CL permeability of high-performance concrete is significantly lower than that of ordinary concrete.
Therefore, the high performance concrete with proper mix proportion and high fluidity has better self compacting property.
8) Poor resistance to high temperature (fire).
4) Improve the concrete construction process.
5) The shrinkage is small.
2) Early and late strength..
Workability of concrete includes: (1) fluidity.
The total shrinkage of HPC is inversely proportional to its strength, and the higher the strength, the smaller the total shrinkage.
Technical specification for application of high performance concrete (cecs207-2006) defines high performance concrete as concrete produced with conventional materials and processes, having various mechanical properties required by concrete structures, and having high durability, high workability and high volume stability.
The compressive strength of high-performance concrete has exceeded 200MPa.
Durability includes fluidity, cohesiveness and water retention.
2) Volume stability.
(1) Characteristics: self compacting body has high stability and strength, less hydration, shrinkage and creep, and good durability.
2) High range water reducing agent shall be selected.
7) Good durability.
Its impermeability, frost resistance, corrosion resistance and impact resistance are better than ordinary concrete.
② The ductility of high strength concrete is worse than that of ordinary concrete.
High performance concrete with 28d average strength between 100-120mpa has been applied in engineering.
Part I concrete characteristics the characteristics of concrete include workability and durability.
(2) Cohesion.
It means that the concrete mixture has a certain cohesion, which will not cause delamination and segregation during transportation and pouring, so as to keep the concrete mixture uniform as a whole.
(2) Technical approach for preparing high performance concrete: water consumption per cubic meter of high performance concrete should not be greater than 175KG / m ³。 The total amount of cementitious materials should be 450-600kg / m ³， The amount of mineral fine powder should not exceed 30% of the total amount of cementitious materials.
The creep deformation of high-performance concrete is significantly lower than that of ordinary concrete.
It combines many advantages, but it is not without disadvantages.
