What are the complementarities of the combination of concrete and rebar

Concrete is easy to obtain, cheap and can be used in large quantities; Rebar is expensive, but it can be used less than concrete.

The compressive performance of concrete is good, and the tensile performance of steel bar is good, and the two can complement each other's strengths.

Concrete is fire-resistant and corrosion-resistant, and is used to wrap steel bars to offset the characteristics of steel bars that are not fire-resistant and non-corrosion-resistant.

These are the main three points.

a): The reason why concrete and rebar can work together is:

1): There is good bonding performance between concrete and steel bar, and the two can be reliably combined together, under common force and deformed together.

2): The temperature linear expansion coefficient of concrete and steel bar is very close (o 82x105 1 1x10-5 for concrete, 1 2x10-5 for steel bar), so as to avoid large temperature stress and damage the cohesion between the two when the temperature changes.

3:) The concrete is wrapped around the outside of the rebar, which can prevent the rebar from corrosion or softening at high temperatures.

4): Prevent steel rust from corroding. The steel exposed to the air medium is easy to rust due to the influence of the acidic medium in the air, and the steel bar buried in the concrete is protected by the weakly alkaline concrete, as long as the protective layer of the steel bar to the edge of the component has sufficient compactness and thickness and the cracks of the control component are not too wide, the concrete can play a role in protecting the steel bar from corrosion, so as to ensure that the decoupling has good durability, and the steel bar and the concrete work together reliably for a long time.

5): high compressive strength of concrete, low tensile strength (the tensile strength of concrete is generally only about 1 l0 of the compressive strength), the compressive and tensile capacity of steel bars are very strong, but the cost of steel is very high, in order to make reasonable use of the high compressive performance of concrete, also in order to save steel, the two materials of steel bar and concrete are combined to work together, make full use of the high compressive strength of concrete, the tensile strength of steel bar is strong, and the compressive member mainly relies on the concrete to be stressed, and the configuration of steel bar is auxiliary, but in the tensile member, the main purpose of the reinforcement is to bear the tensile force under the action of the external load, so that the two materials can do their best and complement each other to form a structural component with good performance.

2): The basis for the two substances with different physical properties of steel and concrete to work together is that the temperature line of steel and concrete is similar to that of expansion and washing; The concrete wraps the steel bar to prevent it from rusting and softening at high temperatures. The two materials of steel and concrete have their own advantages and disadvantages, but after the combination of the two, the reinforced concrete structure complements the shortcomings and makes the best of its own advantages to form a structural material with excellent performance.

What are the similarities and differences between ordinary concrete and reinforced concrete. : Concrete is a mixture of cement (usually Portland cement) and aggregates. When a certain amount of water is added, the cement hydrates to form a microscopic opaque lattice structure, which encapsulates and binds the aggregate into a monolithic structure.

Typically concrete structures have a high compressive strength (approximately 3,000 psi, 35 MPa). However, the tensile strength of concrete is low, usually only about one-tenth of the compressive strength, and any significant tensile bending will cause its microlattice structure to crack and separate, resulting in structural failure. However, most structural components have the need for tensile stress inside, so unreinforced concrete is rarely used alone in engineering.

Compared with concrete, the tensile strength of steel bars is very high, generally above 200MPa, so people usually add stiffening materials such as steel bars to work together with concrete, and the tensile force of steel bars is borne by the steel bars, and the concrete bears the compressive stress part. For example, in Fig. 2, a simply supported beam bending member, when a load p is applied, the upper part of the beam section is compressed and the lower part is retracted. At this time, the steel bar arranged at the bottom of the spring search beam bears the tensile force (4), and the concrete (2) shown in the upper shaded area bears the pressure (3).

In some small cross-sections, in addition to the tensile force, the reinforcement can also be used to withstand the pressure, which usually occurs in the column. The cross-section of reinforced concrete members can be made into different shapes and sizes according to the needs of the project. Like regular concrete, reinforced concrete reaches its design strength after 28 days.