what are the concrete admixtures?
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Admixtures are natural or manufactured chemicals which are added to the concrete before or during mix- ing. The most often used admixtures are air-entraining agents, water reducers, water-reducing retarders and accelerators.
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Pure substances are substances composed of identical particles. ... Cement is a mixture because it is composed of different types of compound particles. Each of the components of concrete by themselves would be pure substances.
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Chemical composition Portland cement is made up of four main compounds: tricalcium silicate (3CaO · SiO2), dicalcium silicate (2CaO · SiO2), tricalcium aluminate (3CaO · Al2O3), and a tetra-calcium aluminoferrite (4CaO · Al2O3Fe2O3).
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The Class of the concrete. There are two classes that concrete can be supplied as: Normal Class and Special Class. NORMAL CLASS CONCRETE has a strength grade of N20, N25, N32, N40 and N50 with the corresponding characteristic strength of 20, 25, 32, 40 and 50 MPa at 28 days.
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Typical uses: FEBMIX PLUS is designed to be used as a mortar plasticising admixture in brick and block laying mortars. The 'micro' air entraining properties of FEBMIX PLUS greatly improves the workability of the mortar whilst reducing water demand, thus greatly reducing the likelihood of cracking and crazing.
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['soda ash (NaZC03) ... ', 'soda (NazO) ... ', 'limestone (CaC03) ... ', 'lime (CaO) ... ', 'silica sand (Si02) ... ', 'silica (SiOz)']
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Wet concrete must be spreadable. It should keep its form, without water emerging from it. If your mixture is too wet, you should add extra gravel, sand and cement (according the 1 – 2 – 3 ratio) until the consistency of your wet concrete is correct. Wet concrete that contains too much water, will lose strength.
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['air entrainers.', 'water reducers.', 'set retarders.', 'set accelerators.', 'superplasticizers.', 'specialty admixtures: which include corrosion inhibitors, shrinkage control, alkali-silica reactivity inhibitors, and coloring.']
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Type 1 - Normal portland cement. Type 1 is a general use cement. Type 2 - Is used for structures in water or soil containing moderate amounts of sulfate, or when heat build-up is a concern. Type 3 - High early strength. ... Used where the water or soil is high in alkali.
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Although the terms cement and concrete often are used interchangeably, they're not the same thing. Concrete actually includes cement and other things, like aggregates and paste.
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['Use of high strength concrete results in smaller sections.', 'High strength concrete offers high resistance in tension, shear, bond and bearing.', 'Less loss of prestress occurs with high strength concrete.']
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Cementitious products comprise the glue that holds concrete together. These materials include traditional Portland cement and other cementitious materials, such as fly ash, ground granulated blastfurnace slag (GGBS), limestone fines and silica fume.
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Concrete is a mixture of water, cement, sand just like mortar. However concrete also has gravel and other coarse aggregates that makes it stronger and more durable. ... Mortar, which is a mixture of water, cement, and sand, has a higher water-to cement ratio than concrete.
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Typically pozzolans are used as cement replacements rather than cement additions. Adding pozzolans to an existing concrete mix without removing an equivalent amount of cement increases the paste content and decreases the water/cement ratio. In other words, adding more pozzolans to a mix changes the mix proportions.
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['Concrete slab or surface course.', 'Granular base or stabilized base course.', 'Granular subbase or stabilized subbase course.', 'Frost protection layer.', 'Subgrade soil.']
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A proper cohesiveness can ensure concrete to hold all the ingredients in a homogeneous way without any concentration of a single component, and even after the full compaction is achieved. An obvious separation of different constituents in concrete is called segregation, as shown in Figure 3-6.
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['Concrete is a heterogeneous mixture of an aggregate: cement, and water.', 'Sugar and sand form a heterogeneous mixture. ... ', 'Ice cubes in cola form a heterogeneous mixture. ... ', 'Salt and pepper form a heterogeneous mixture.', 'Chocolate chip cookies are a heterogeneous mixture.']