Concrete Construction

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The word “concrete” has its origin from the Latin word “concretus”, which means to grow together. It is a very strong and versatile construction material as it can be moulded to take up the shapes required for the various structural forms. It is produced by mixing cement, sand, and aggregate (e.g. gravel or crushed rock) with water. The oldest concrete was discovered around 7000 BC. It was found in 1985 when a concrete floor was uncovered during the construction of a road at Yiftah El in Galilee, Israel. It consisted of a lime concrete, made from burning limestone to produce quicklime, which when mixed with water and stone hardened to form concrete [1]. Throughout history, cementing materials have played a vital role and were used widely in the ancient world. A cementing material was used between the stone blocks in the construction of the Great Pyramid at Giza in ancient Egypt around 2500 BC. Greeks and Romans used lime made by heating limestone and added sand to make mortar, with coarser stones for concrete. Examples of early Roman concrete have been found dating back to 300 BC [1]. The Romans found that a cement could be made which set under water and this was used for the construction of harbours. This cement was made by adding crushed volcanic ash to lime and was later called a “pozzolanic” cement, named after the village of Pozzuoli near Vesuvius. British engineer John Smeaton made the first modern concrete in the year 1756. He added pebbles as the course aggregate with brick powder. It is believed that the Romans used concrete that is similar to the ones that are in use today. Portland cement was developed from natural cements made in Britain beginning in the middle of the eighteenth century. In 1824, Joseph Aspdin, a British stonemason, produced a cement in his kitchen. He prepared that cement by heating a mixture of finely divided clay and hard limestone in a furnace until CO2 had been driven off. The type of modern cement was made in 1845 by Isaac Johnson, who burnt a mixture of clay and chalk by clinkering. The name “Portland cement” was given originally due to the resemblance of the colour and quality of the hardened cement to Portland stone, a type of building stone (limestone) quarried in Dorset. Concrete can be defined as a mixture of cement, water, aggregate (fine and coarse), and admixture, which is sometimes added to modify certain of its properties. It is a temporarily plastic material but is later converted to a rock-like material by chemical reaction with a high compressive strength. Normal concrete has comparatively low tensile strength and for structural applications
it is normal practice to incorporate steel bars to resist tensile forces. The strength, durability, and other characteristics of concrete depend upon the properties of its ingredients, the proportions of mix, and the method of transporting, placing, compacting, and curing. Good concrete has to satisfy performance requirements in the plastic and hardened states. In the plastic state, the concrete should be workable and free from segregation and bleeding. In the hardened state, concrete should be strong, durable, and impermeable, and it should have minimum dimensional changes. The popularity of the concrete is due to the fact that from the common ingredients, it is possible to tailor the properties of concrete to meet the demands of any particular situation. Among the various properties of concrete, its compressive strength is considered to be the most important and is taken as a measure of its overall quality

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