What is concrete?
Concrete is a compound material made up of cement, coarse aggregate and water – these are the main compound materials of concrete. When the compounds of concrete mixed with each other a fluid mass form of concrete is obtained and which can pour into moulds to get a specific desired shape. This fluid mass concrete hardens with respective to time. Actually the cement reacts with other compounds chemically to bind them together to form a hard thing – concrete.
Materials of concrete
Cement
Water
Coarse aggregates / fine aggregates
Admixtures
The proportion of the materials should maintain in a correct way, as the materials affect the final concrete product. Mainly the water cement ratio should be considered carefully. When the water cement ratio increases, the strength of the final product will decreased. Concrete is prepared with the consideration of time and placement area. . If good -quality concrete is to be produced, then not only must the constituents of the mix be up to standard, but also the equipment used in mixing, transporting, placing and compacting must be suitable for the task. The general properties of concrete mostly coincide with the properties of rock. Concrete is the main component of construction material as it resists compression, flexible to get multiple shapes and reinforced concrete is resistant to the tensile stress too.
Uses of concrete
Worth enough on investing for a concrete building as the strength of concrete increases with time and ability to withstand all weather conditions satisfy an investor. As the concrete is non combustible building material, it provides enough safe for the users. Before the concrete get hardens it can be mould into shapes as per owner’s wish. Concrete is good enough in compression. Concrete is a durable and sustainable building material that exists from the past.
Types of concrete
1. Plain or ordinary concrete
Main constituent materials of this type concrete are cement, aggregate and water. As the reinforcement is missing in this type of concrete, it is suitable for the structures in which high tensile strength is not necessary.
2. Reinforced concrete
Reinforced concrete is introduced to rectify the issue in plain concrete that is introduction of reinforcement to the plain concrete. Reinforcement is provided by steel rods, wire mesh or steel rods. The combination of rebar and plain concrete withstand the tensile, compressive force and behave as a single material. Nowadays most of the building structures use this type of concrete.
3. Lightweight concrete
Lightweight concrete is a type of concrete which contains an expanding agent. That expanding agent is the lightweight aggregate of lightweight concrete. That agent increases the volume of the concrete mixture and reduces the dead weight of the mixture. Lightweight concrete is prepared using light weight aggregates such as pumice, scoria, shales and clays. Lightweight concrete is a good fire resistive material but lightweight concrete is sensitive to water, takes much time for the preparation and can be breakable like a glass material (brittleness).
4. High density concrete
High density concrete is prepared using crushed rocks to provide heavy weight concrete mixture. This type of concrete is commonly used in structures where radiations are needed to be controlled.
5. Precast concrete
Precast concrete means concrete is prepared then cast on reusable moulds and cured on a factory. Normally structural components are prepared using precast concrete.
6. Prestressed concrete
Prestressed concrete is used to prepare structural elements such as floor beams, railway sleepers, piles and etc. Prestressed concrete element is prepared by applying the determined stress in advance to prevent the stress that will be applied on the same element by loading. The prestressed concrete withstands the load by the induced stress in the whole prestressed concrete element.
7. Glass reinforced concrete
Glass reinforced concrete is prepared from a concrete matrix which containing strengthened alkali resistant glass fibres. The composite material performs well to withhold the weight of load. This type of concrete is used in exterior cladding works.
8. Air-entrained concrete
Air-entrained concrete is prepared by applying air entraining admixtures to the concrete mixture when it is prepared. A certain percentage of tiny air bubbles are introduced to the plain concrete as to create chambers for water to expand into when it freezes. Purposes of air entrained concrete are increasing the durability of the hardened concrete during climatic conditions such as freeze thaw and to increase the workability of concrete in plastic state.
9. Self compacting concrete
Self compacting concrete needs a mechanical support to spread the concrete mixture as the Self compacting concrete is a non-segregating or non flowing concrete mixture. Now-a- days complex structural frames uses this type of concrete.
10. Smart concrete
Smart concrete is introduced as the stress or strain can be identified before the concrete structure fails or they help to heal the cracks as the cracks can be identified at the initial stage.
