Reinforced concrete offers a wide range of structural alternatives and cost-effective solutions for a variety of scenarios, from residential structures with modest live loads and spans of around 25 feet to commercial buildings with larger live loads and spans of 40 feet to 50 feet and beyond. The strength of reinforced concrete depends on the quality of the mix and the amount of reinforcement used. For example, ordinary house paint is usually strong enough to give the average-size house a five-year warranty, while the same coating applied to a baseball stadium would need to be at least six months old before it could be considered safe.
The longevity of reinforced concrete structures is due to the fact that they are designed to resist internal forces such as compression and tension. These forces may become excessive in certain circumstances, such as when an earthquake hits a building site or when heavy machinery is nearby. In such cases, reinforcement is needed to prevent damage to the structure. Reinforcement can be in the form of wires inserted into the concrete during its construction or metal bars placed inside the hollow spaces of concrete frames. Modern buildings often include steel frames with glass panels attached to their exterior, which are then wrapped in plastic sheeting as part of the finishing process. This creates a completely enclosing shell within which no water can penetrate to weaken the concrete
The span of a concrete structure is the distance between its bearing walls or other supporting elements.
Concrete has a great compressive strength but a very low tensile strength. As a result, it is generally strengthened using high-tension materials (often steel). Concrete can be made into many different shapes before it hardens, and it can also be molded after it sets. It is very resistant to corrosion and does not break down easily over time.
Concrete is used in construction because of its durability and versatility. It is easy to work with and can be colored or shaped at any stage during construction. It is also inexpensive and readily available worldwide.
Concrete's main drawback is that it is heavy. For this reason, it is usually used for large structures such as buildings or bridges. It can also be used in small quantities for details on smaller projects.
The density of concrete varies depending on how much water it contains. Dense concrete can weigh more than 900 kg/m3 while lightweight concrete can be as thin as 1 mm and only 4 kg/m3.
Concrete has a high strength to weight ratio. This means that it can support a large amount of force relative to its own weight.
When dry, standard reinforced concrete weighs 150 pounds per cubic foot, although there are "light" varieties that can weigh as little as 100 pounds per cubic foot or as much as 300 pounds per cubic foot. This means that a square foot of concrete should weigh about 50 pounds if it's used as an internal wall surface.
As concrete cures, it becomes more dense and heavy. The weight of the concrete should not be significantly affected by its age because the normal reinforcing agents - wood fibers for ordinary concrete, steel fibers for high-strength concrete - remain in place, even after the concrete has cured. However, if the concrete is subject to constant freezing and thawing, the wood fibers may expand and contract enough to weaken the concrete.
Concrete loses weight as it cures because water is removed through hydration and crystallization. The amount of loss will depend on the type of concrete and the rate at which it cures. For example, plain concrete loses 2% of its original weight as it cures, while high-strength concrete loses 4%. Concrete needs to be weighted while it is curing to ensure that it does not become too light due to drying out.
The density of hardened concrete varies depending on the type of reinforcement used. Reinforced concrete is weighed while it is wet, before any moisture has had time to evaporate.
A simply supported concrete beam's greatest span has no limit; it can be 100 meters long. However, the depth will be in the region of 10 meters, necessitating massive quantities of reinforcement, labor, and, of course, expense. In practice, a simply supported concrete beam has a maximum span of 7 meters. A complex-supported beam might be expected to last much longer.
The load on a concrete beam depends on its use. For example, a bridge beam would be expected to carry significant loads, so it must be strong enough for its purpose. The load on a concrete beam is usually specified by its owner or designer. A simple concrete beam under typical loading conditions will last around 20 years.
Beams are used in many structures, including buildings, bridges, and dams. When beams are used as main support members they are called primary beams. Secondary beams are supporting elements attached to primary beams to connect them together at different levels. Tertiary beams are additional support elements attached to secondary beams etc.
Concrete has useful properties that make it suitable for structural applications. It is easy to work with, readily available, and relatively inexpensive. It has good tensile strength and compressive strength, depending on how it is made. It can be poured into any shape required by the builder, and once set it cannot be cut easily. However, if exposed to heat or air pollution during curing, it can become brittle and crack.
In residential and commercial constructions, the compressive strength of concrete typically ranges from 2500 psi (17 MPa) to 4000 psi (28 MPa) and higher. Several applications also make use of pressures greater than 10,000 psi (70 MPa). Concrete's tensile strength is about 7 MPa.
Concrete's yield strength is about 20% to 25% of its ultimate strength. Therefore, the maximum load that a concrete beam will support is approximately equal to seven times its yield strength. A common mistake is to assume that this value is its breaking strength, which is why beams are often over-designed. In fact, their typical life expectancy is 20 years or more.
The average person walking on a bridge made with normal concrete would be able to do so without any problem. The bridge would likely fail at some point, however, because its design strength is only half of its intended service level. This means that it could fail under relatively light traffic conditions.
The designer of a concrete bridge should ensure that it has sufficient depth below the surface for traffic loads as well as adequate reinforcement. For example, a deep foundation may be required for bridges that will carry heavy vehicles.
Concrete can be made stronger by using special techniques and materials when casting it. The most common method of increasing strength is to add fibers to the mix.
Concrete has a high compressive strength but a much lower tensile strength. Because of shrinkage and strain, all concrete constructions will fracture to some extent. Concrete is prone to creep when subjected to long-term stresses. This means that over time, it will lose strength.
Comparing concrete to steel, concrete has about a tenth of the tensile strength. But this should not be considered a problem because its main purpose is not to resist tension but rather to support weight. Concrete is used as a structural material because it's strong enough to carry weight, but it can also be molded into any shape you need.
Concrete structures are required by law to be inspected for safety at least once every five years. If an area of concern is found during this inspection process, then it's important to call a professional immediately so that the issue can be addressed before any further damage occurs.