Things to know about reinforced concrete

 

Reinforced concrete (reinforced concrete) is a composite material combined by concrete and steel, in which concrete and steel join forces. Reinforced concrete structures are used in almost all fields of civil construction and construction of transport works such as houses, bridges, roads, industrial factories, airports, irrigation, etc. Currently, the reinforced concrete structure plays a key role as the main bearing structure for the whole project.

In Vietnam, according to preliminary statistics, construction works from reinforced concrete structures account for 70% of total construction works.

(Photo: Internet source)

The combination of concrete and reinforcement comes from the fact that concrete is a material with low tensile strength (only from 1/20 to 1/10 compressive strength of concrete), thus limiting usability of concrete and cause waste of material usage. This feature is overcome by adding to the concrete 'reinforcing bars', usually made of steel, of a much higher tensile strength than concrete. 'Reinforcement' is therefore usually located in the tensile areas of the structure.

Construction structures using concrete combined with ‘reinforced’ are collectively referred to as the ‘reinforced concrete structure’; reinforced concrete structure, with 'reinforced' as steel bars, is the 'oldest and most widely used' reinforced concrete structure 'in construction. Under normal conditions, the combination of concrete and reinforcement works well thanks to the following characteristics:

Adhesion force between concrete and reinforcement: this force is formed during the hardening of concrete and prevents reinforcement from slipping off of concrete during bearing.

There is no chemical reaction between concrete and steel that affects each type of material, in addition, because the reinforcement is placed inside concrete, it is also protected by concrete from corrosion due to environmental impact.

Concrete and steel have approximately the same coefficient of thermal expansion:

With concrete is about 1.0 x 10-5 ~ 1.5 x 10-5. With steel is 2 x 10-5. Therefore, the normal range of temperature changes (below 100 ° C) does not affect the internal combination between concrete and reinforcement.

Because the concrete has good compressive strength and the reinforcement is introduced into the concrete to overcome the poor tensile strength of the concrete, basically in the reinforced concrete structure, the reinforcement will bear tensile stress while the concrete stress-resistant cardboard
.

(photo: Internet)

ADVANTAGES:

Reinforced concrete structure is widely used thanks to the following advantages:

Low cost: concrete is made mainly from available materials such as stone, gravel, sand ... Other materials such as cement and steel are more expensive but only account for approximately 1/6 to 1/5 of the total. mass.

Large bearing capacity: bearing capacity of reinforced concrete is much larger than other types of materials such as bricks, stones, wood ... Moreover, other than construction materials of natural origin, Reinforced concrete is an artificial material, so through fabrication it is possible to select the desired features.

High strength: concrete is a stone, so it is more resistant to corrosion, environmental erosion than materials such as steel, wood ... Maintenance costs are also lower.

Ability to create shapes easily: before freezing, the concrete in the form of liquid and flexible mixture should be able to create shapes suitable for architectural requirements thanks to the formwork system.

Good fire resistance: in the threshold below 400 ° C, the intensity of the concrete is not significantly reduced, the heat conduction coefficient of concrete is also low, so it helps protect the reinforcement at high temperatures.

Good energy absorption capacity: structures made of reinforced concrete often have large volumes, so they can absorb shock forces well.

DEFECT:

Heavy: construction structures made of reinforced concrete usually have relatively small spans, high construction costs of foundations. This disadvantage is currently overcome by the use of prestressed concrete structures or high strength concrete structures in combination with reasonable construction solutions.

Long construction time: concrete needs time to harden, during which time the quality of concrete is heavily influenced by weather, environment ... This disadvantage can be overcome by using precast concrete. assembled or semi-assembled.

Low reuse: dismantling, transporting and reusing concrete after use is costly and laborious.

Cost for formwork system.

 

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