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Composition of Concrete

Concrete is made up of three main ingredients: water, Portland cement, and aggregates. The ratio of the ingredients changes the properties of the final product, which allows the engineer to design concrete that meets their specific needs. Admixtures are added to adjust the concrete mixture for specific performance criteria. Water The water in the concrete mix should be clean and free of impurities. The amount of water relative to the amount of cement changes how easily the concrete flows, but also affects the final strength of the concrete. More water makes for easier flowing concrete, but also makes for lower strength concrete upon curing. Portland cement Cement hardens when it is mixed with water, which binds all of the ingredients together. Portland cement is the most common cement used. It is composed of alumina, silica, lime, iron, and gypsum. Small amounts of other ingredients are also included. Aggregates The majority of a concrete mixture is made up of coars...
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Concrete and Screed

Concrete and screed and are formed of the same basic ingredients – cement, aggregates and water. But what makes them different is the size of aggregates, the cement grade, mix consistency, and their intended application or use. Composition and Mix Proportion Concrete in its simplest form is a rock like mass formed by the hardening of cement paste and aggregates  mixed in a proportion of – 1 Cement: 2 Sand: 3 Coarse aggregates (ballast/gravel). But many variations are applied to this basic mix design to suit different uses and strength requirements. Screed  is a thin layer of cement paste and sand/ fine aggregates, laid onto a concrete floor base or under floor heating to act as a smooth flat levelling surface for taking on the final floor finish. Screeds generally follow a mix proportion of 1Cement: 3-5Sand (0-4mm washed sharp sand for levelling screeds). For heavy duty screeds 25 percent of the 0-4mm sand is replaced by 6-10mm single sized aggregates, making the...
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Types of Concrete

There are different types of concrete are manufactured today for different needs and applications. The formulas and ingredients vary to suite the condition and preference of various construction designs. Today we are discussing about the different types of concrete that are commonly used. Normal or Regular Concrete The concrete in which common ingredients are aggregate, water, cement is known as normal or regular concrete. It is also called normal weight concrete or normal strength concrete. It has a setting time of thirty to ninety minutes depending upon moisture in atmosphere and the fineness of cement. The development of the strength starts after seven days the common strength values is 10 MPa (1450 psi) to 40 MPa (5800 psi). At about 28 days 75 - 80% of the total strength is attained. Almost at 90 days 95% of the strength is achieved. Its density ranges from 140 pcf to 175 pcf and is strong in compression and weak in tension. High strength concrete It posses compr...
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Production Process of Ready Mix Concrete

Ready mix concrete is a mixture of Portland cement, water and aggregates comprising sand and gravel or crushed stone. During the mixing phase the different components come together to produce a uniform mass of concrete. A ready-mix concrete plant consists of silos that contain cement, sand, gravel and storage thanks of additives such as plasticizers, as well as a mixer to blend the components of concrete. These components are gravity fed into the preparation bin. The quality of concrete can be maintained only if the formulation is carefully administered. The water dosage in particular must be very precise and the mixing itself must remain continuous and consistent. To accommodate all of these constraints, the concrete plants have been automated to ensure reliability throughout the manufacturing process using centralized computer. Finally, the concrete prepared in a batch plant is loaded into a mixer truck, also known as a transit mixer, which delivers it to the construct...
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The Advantages of Ready Mix Concrete

  Ready-mix concrete is concrete that is manufactured in a factory or batching plant, according to a set recipe, and then delivered to a work site by truck mounted in–transit mixers. This results in a precise mixture, allowing specialty concrete mixtures to be developed and implemented on construction sites. Ready-mix concrete is preferred over on-site concrete mixing because of the precision of the mixture and reduced work site confusion.   The advantages of ready mix concrete are the following. Quality assured - It is produced under controlled conditions using consistent quality of raw material. High speed of construction- Speed of construction will be fast if ReadyMix Concrete is used. Reduction in cement consumption -The consumption of cement will be reduced by 10 – 12 % due to better handling and proper mixing. Versatility in uses and methods of placing - The mix design of the concrete can be tailor made to suit the placing methods of the...
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