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6 Types of Concrete
Over the years, various types of concrete have been developed for different applications. Their material
constituents, mix design, construction methods, area of application and properties are also different.
Following are some of the concrete types which are in normal and special use.
Plain concrete: Plain concrete is manufactured by mixing the basic ingredients of concrete, that is, cement,
aggregate and water. It does not have any reinforcement and normally uses a proportion of 1:3:6 or maximum
1:2:4. This type of concrete is normally used as lean concrete under footings, rafts etc and also as slab-on-
ground and in areas where there is limited demand for tensile strength.
Reinforced Concrete: Today’s concrete, with cement as one of its main components, is able to support huge
amounts of weight without crumbling. It has high compressive strength. Though concrete has high compressive
strength, it is relatively brittle material whose tensile strength, that is, ability to bend is limited compared to
compressive strength. Concrete breaks when it bends. That is a big problem when building bridges, dams or
support columns that must make adjustments for weather, earthquake and wear to endure. To offset this
limitation, it was found possible in the second half of nineteenth century, to use steel with its high tensile
strength to produce reinforce concrete.
In 1849, just twenty-five years after the patenting of Portland cement, Joseph Monier, a Parisian pot maker,
invented reinforced concrete. Monier received a patent for his method of adding steel bars or mash to
concrete before it hardens which bought about yet another innovation in modern building techniques and
improved the tensile strength of concrete.
But according to Mark Andrew Miodownik, a British materials scientist and engineer, reinforced concrete was
invented by a plasterer from Newcastle called W.B. Wilkinson in 1953. He inserted steel barrel hoops into wet
concrete to resist the tensile forces that cause concrete to crack under load.
The reinforcement is usually round steel bars with appropriate surface deformations to provide interlocking, is
placed in the forms in advance of concreting. When completely surrounded by hardened concrete mass, it
forms an internal part of the member. The resulting combination of the two materials, known as reinforced
concrete, combines many advantages of the two materials: relatively low cost, good compressive strength,
high tensile strength, much greater ductility and toughness of steel. Reinforced concrete is still widely used
today in a multitude of projects, from skyscrapers to dams, bridges and highways.
Prestressed concrete: In prestressed concrete, there is special technique by which the bars or the tendons that
are used in concrete are stressed before the application of the service load. The bars or tendons are placed
and anchored firmly from both end of the structural element during the placing of concrete.
Precast concrete: In precast concrete structural elements are made and cast in the factory as per specification
with arrangements for joining different elements and brought to the site and assembled with other elements.
Precast wall and slab blocks, beams, concrete lintels, staircase units are some examples of precast units of
reinforced concrete. Precast concrete has the advantage of shortened construction time compared to in-place
concrete. As the elements are constructed in the factory, quality is assured but special care shall have to be
taken during transporting and handling to avoid damage.
Lightweight concrete: Lightweight aggregate is used in the manufacturing of lightweight concrete. It has a
density of about 1440 to 1840 kg/m 3 (90 to 1115 lb./ft3) compared to normal weight concrete density of 2240
to 2400 kg/m3 (140 to 150 lb./ft3). Lightweight aggregates used in structural lightweight concrete are typically
expanded shale, clay or slate materials that have been fired in a rotary kiln to develop a porous structure.
Other products such as air-cooled blast-furnace slag are also used. There are special requirements for
lightweight structural concrete in the code.
High density concrete: The concretes that have densities ranging from 3000 to 4000 kg/m 3 (190 – 250 lb./ ft3).
The key to high density (HD) concrete is the aggregate. The quality and types of aggregate are the most
important factors in the selection process. No matter what types of heavy aggregate are chosen, they must
meet the same standard of quality as normal aggregate such as ASTM C 33. Every other properties remaining
constant, the relative density of the aggregate should be suitable to produce the desired concrete density. In
the ‘60s and ‘70s, HD concrete was used quite a bit due to boom in nuclear power plant construction. High
density concrete costs more than normal concrete but provides excellent shielding from harmful radiation due
to its mass.
Air entrained concrete: Air-entrained concrete contains billions of microscopic air cells per cubic foot. These
air pockets relieve internal pressure on the concrete by providing tiny chambers for water to expand when it
freezes. Air-entrained concrete is produced by using air-entraining Portland cement, or by the introduction of
air-entraining agent, under careful engineering supervision. The amount of entrained air is usually between
four and seven or eight percent of the volume of concrete. This type of concrete is used in countries where
there is alternate cycle of freezing and thawing of water.