Concrete is a hard and chemically inert structural material consisting of aggregate (usually sand and gravel), cement, and water. It has been used in construction since ancient times, with clay being the most widely used binding substance. This form of concrete is still widely used in industry and modern construction. Reinforced concrete is created by placing wires, steel rods or cables into the concrete before it sets, which increases its strength.
Fibers are also sometimes used to reinforce the concrete. Invented in the 19th century, reinforced concrete has revolutionized the construction industry, allowing for the building of bridges, roads, and other large structures. Rebar reinforced concrete is commonly seen at construction sites. Prestressed concrete units are also used in large projects.
This type of concrete is created using a special technique that involves tensioning bars or tendons prior to the application of the concrete. This process makes the lower section of the unit stronger against tensile forces, but requires heavy equipment and skilled labor. Prestressed concrete is used to build bridges, heavy-load structures or roofs that have long spans. Precast concrete units are also used in construction.
These units are manufactured in a factory to exact specifications and then transported to the site for assembly. The advantage of precast concrete is its rapid assembly and high quality. Air can be entrained into the concrete by adding foaming agents such as alcohols, resins or fatty acids during the mixing process. This must be done under careful engineering supervision since concrete is usually mixed on-site.
Entrained air adds up to 3-6% of the volume of the concrete and is almost always used in freezing environments or where there are freeze-thaw cycles. Smart concrete technology offers an alternative method for monitoring the condition of reinforced concrete structures. Short carbon fibers are added to the concrete using a conventional mixer, which affects its electrical resistance when it encounters stress or strain. This type of concrete can be used to detect possible problems before failure occurs. Reinforced Concrete (RC) is a versatile compound and one of the most used materials in modern construction. It combines the high-strength compressive properties of concrete with the high tensile strength of steel.
In reinforced concrete, stresses are borne by steel reinforcement, while prestressed concrete bears load through induced stresses throughout the structural element. Glass Reinforced Concrete (GRC) or Glass Fiber Reinforced Concrete (GFRC) is a building material commonly used to form exterior cladding panels. Self-Compacting Concrete (SCC) is another important recent advance in concrete technology. It is a non-segregating concrete that can flow under its own weight, spread out, fill formwork and encapsulate reinforcements without mechanical consolidation. Structures can be composed of three basic types: load-bearing structures, slab and beam structures, and lightweight frame structures. Load-bearing structures transfer weight to walls in the form of ceilings and floors supported directly on walls.
Slab and beam structures involve bending members where slabs rest on beams which transfer load to columns connected to footings resting on ground that carry load to hard strata. Lightweight frame structures are usually built from powder or lightweight concrete blocks above basement with access space extending between walls of base. Wood or rectangular steel, tube or channel are usually used as material for lightweight frame structure with wooden parts attached by fastening nails or bolted steel parts attached by nuts and bolts. Exterior finishes for walls and ceilings include plywood or composite siding, brick or stone surfaces and various plaster finishes while interior wall coverings include drywall, plank, plaster, decorative wood or fiberglass panels.