The reason why reinforced concrete can work together is determined by its own material properties. First of all, steel and concrete have approximately the same coefficient of linear expansion, which does not cause excessive stress from the environment. Secondly, there is good adhesion between steel and concrete. Sometimes the surface of the steel is also processed into spaced ribs (called deformed steel bars) to improve the mechanical joint between the concrete and the steel bars, which is still not enough to transfer the steel bars. When the tension between the concrete is applied, the ends of the steel bars are usually bent by 180 degrees. In addition, the alkaline environment provided by calcium hydroxide in concrete forms a passivation protective film on the surface of the steel bar, making the steel bar less corrosive than neutral and acidic environments. Concrete company
Concrete is a mixture of cement (usually Portland cement) and aggregate. When a certain amount of water is added, the cement hydrates to form a microscopic opaque lattice structure to enclose and bond the aggregate into an integral structure. Concrete structures generally 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. Any significant bending action will cause the microscopic lattice structure to crack and separate, resulting in structural damage. Most of the structural members have the requirement of tensile stress inside, so the concrete without reinforcement is rarely used alone in engineering.
Compared with concrete, the tensile strength of steel bars is very high, generally above 200 MPa. Therefore, people usually work with reinforcing materials such as steel bars in concrete, and the tensile force is taken up by the steel bars, and the concrete bears the compressive stress portion. For example, in the simply supported beam bending member of Fig. 2, when the load P is applied, the upper portion of the beam section is pressed and the lower portion is pulled. At this time, the steel bar placed at the bottom of the beam bears the tensile force (4), while the concrete (2) shown in the upper shaded area is subjected to the pressure (3). In some small-section members, in addition to tensile forces, steel bars can also be used to withstand pressure, which usually occurs in columns. The cross section of reinforced concrete members can be made into different shapes and sizes according to engineering needs.
Like ordinary concrete, reinforced concrete reaches design strength after 28 days. Concrete manufacturer
