What are the characteristics of the structure of concrete, and what are the main forms of the struct

Structural characteristics: multi-phase, porous composite cement stone contains crystalline and amorphous hydrates.

unhydrated cement particles, various pores and water; Sand.

Aggregates contain a variety of rocks, minerals and pores, and the interface also contains cement hydrates and pores. Cement, stone and sand and gravel aggregates are multi-phase, porous materials, solid particle aggregates, and coarse aggregates are filled by fine aggregates. The pores of fine aggregate accumulation are filled by hydrate and cement particles, mineral admixture powder particles; This results in a dense aggregate structure of solid particles. The concrete structure is a particle aggregate of various sizes, the sand and gravel particles are piled up into a skeleton, the hydrate and cement particles are piled up into a cement stone, and the types of complex and heterogeneous aggregates are different, the shape and size are unequal, and the distribution is uneven; uneven composition and structure of cement stone; The presence of weak transition zones (thickness of about 10 50 m) is non-fixed and variable, and the composition and structure of cement and stone and transition zones are constantly changing with time, temperature and humidity.

Advantages of concrete structure:

Reasonable use of materials:

The material strength of steel and concrete can be fully exerted, the ratio of structural bearing capacity and stiffness is appropriate, there is basically no local stability problem, the unit stress is low, and the economic indicators are better than those of steel structures for general engineering structures.

Good moldability: Concrete can be poured into various properties and sizes as needed, and is suitable for various structures with complex shapes, such as thin shells in space.

box-shaped structure, etc.

Good durability and fire resistance, low maintenance costs:

The steel bar has a protective layer of concrete, which is not easy to corrode, and the strength of concrete increases with time; Concrete is a poor conductor of heat, 30mm thick concrete protective layer.

It can be fire-resistant for 2 hours, so that the steel bar will not lose its strength due to excessive heating.

The integrity of the cast-in-place concrete structure is good

Through suitable reinforcement, good ductility can be obtained, which is suitable for seismic and explosion-resistant structures; At the same time, the anti-vibration and anti-radiation performance are good, and it is suitable for protective structures.

High stiffness and damping:

It is beneficial for the deformation control of the structure.

Easy to source from local sources:

In recent years, industrial waste has been used to make artificial aggregates or as an additive component of cement to improve the performance of concrete.

In addition to having higher bearing capacity and better mechanical performance than plain concrete structure, the reinforced concrete structure also has the following advantages compared with other structures:

1) Local materials. In reinforced concrete structures, sand and stone account for a large proportion, and cement and steel make up a small proportion, and sand and stone can generally be provided from the vicinity of the construction site.

2) Save steel. Reinforced concrete structures have a high bearing capacity and can be used to replace steel structures in most cases, thus saving steel.

3) Durable and fire-resistant. The steel bars are buried in concrete, which is protected by concrete and is not prone to corrosion, thus improving the durability of the structure. When a fire breaks out, the reinforced concrete structure will not be burned like a wooden structure, nor will it be destroyed as quickly as a steel structure can reach a softening temperature.

4) Good modularity. Reinforced concrete structures can be poured and pounded into any shape as needed.

5) The cast-in-place or assembled monolithic reinforced concrete structure has good integrity and high stiffness. Reinforced concrete structures also have the following major drawbacks:

1) Self-weight. The gravity density of reinforced concrete is about 25kN3, which is greater than the gravity of both masonry and wood. Although less heavy than steel, the structure has a larger cross-sectional dimension, so its dead weight far exceeds the weight of a steel structure of the same span or height.

2) Poor crack resistance. As mentioned earlier, the tensile strength of concrete is very low, therefore, ordinary reinforced concrete structures often work with cracks. Although the presence of cracks does not necessarily mean that the structure has failed, it does affect the durability and aesthetics of the structure.

When the cracks are more numerous and wider, they can also create a sense of insecurity.

3) Brittle in nature. The brittleness of concrete increases with the increase of concrete strength grade.

To sum up, it is not difficult to see that the advantages of reinforced concrete structures outweigh their disadvantages. Moreover, many effective measures have been worked out to overcome its shortcomings. For example, in order to overcome the shortcomings of reinforced concrete's own weight, many lightweight, high-strength concrete and high-strength steel bars have been studied.

In order to overcome the shortcomings of ordinary reinforced concrete, which is prone to cracking, prestress can be applied to it. In order to overcome the brittleness of concrete, fibers can be mixed into concrete to make fiber concrete.

1. What are the types of concrete structures?

1. Reinforced concrete frame structure.

Now the building is mainly based on this structure, which is generally used in the load-bearing aspect of the house, including beams and columns, floor roofs and other structures, and will use reinforced concrete structure, which belongs to a kind of frame structure, and is generally made in a cast-in-place way. After the frame is made, the partition wall can be filled with lightweight materials such as shale hollow bricks, light steel keel gypsum board, etc.

2. Shear wall structure.

The shear wall itself belongs to the seismic structure wall, and the wall itself has good load-bearing, and the wall is made of reinforced concrete. When making, the steel bars are bundled, and after the formwork is assembled outside, the concrete can be poured.

3. Plate and column structure.

Plate and column structure building is relatively rare, because its overall seismic resistance is weak, not suitable for use in the first area, this structure is made of reinforced concrete columns, beamless floor panels.

4. Cylinder structure.

It is enclosed by reinforced concrete wall, which is manifested as a cylinder shape, and the stiffness of the cylinder is larger, which is the main load-bearing place.

Pros:1High intensity.

2.The cost is low, the economic performance is good, and the local materials can be used.

3.Water resistance, fire resistance.

4.It has high ductility and strong radiation resistance.

5.Strong modularity.

Cons: 1Self-weighted.

2.The construction period is long.

3.Poor crack resistance.

Features of concrete:

1. Good water resistance;

2. Abundant component materials and good economy;

3. Easy to form as components of any shape and size;

4. A large amount of industrial waste can be used

5. It can be used in combination with steel.

Advantages: 1. Abundant raw materials and low cost;2. Good plasticity;3. High strength;4. Good durability;5. It can be reinforced with steel bars.

Disadvantages: 1. Self-weight;2. Brittle materials.

Harder, harder than most materials after molding.

It's hard!It's all about reinforced concrete. How hard!

Answer]: c, d, e

This question assesses the merits of concrete structures. Advantages of concrete construction:

1) The strength is high, and the strength of both steel and concrete materials can be fully utilized 52) The moldability is good, and the application is wide

3) Good durability and fire resistance, low maintenance cost;

4) The cast-in-place concrete structure has good integrity and ductility, which is suitable for seismic and explosion-resistant structures, and has good anti-vibration and anti-radiation performance, and is suitable for protective structures;

5) It is easy to take materials from the sedan car. The disadvantages of the trembling car of the concrete structure: self-weight, poor crack resistance, complex construction and long construction period.

Answer] Shanna: a, b, c, e

This question assesses the merits of concrete structures. The advantages of concrete structure include: (1) high strength, and the strength of both steel and concrete materials can be fully utilized; (2) Good modularity, wide range of application; (3) Good durability and fire resistance, low maintenance cost; 4) The cast-in-place concrete structure has good integrity and ductility, which is suitable for seismic and explosion-resistant structures, and has good anti-vibration and anti-radiation performance, and is suitable for protective structures; (5) Easy to take local materials.