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... their applications of use within the construction industry. There are a variety of admixtures that improve the performance of concrete in many different ways; however, there are only two main basic types, chemical and mineral. Admixtures are classed according to their function and it is for this reason that both chemical and mineral types can be further categorised as each displays different characteristics when used in concrete. 2 TYPES OF ADMIXTURE 2.1 Chemical Chemical admixtures are employed to modify the properties of hardened concrete and to ensure its quality during mixing, transporting, placing, and curing. They also reduce the cost of construction and prevent certain emergencies from occurring during concrete operations. They fall into five distinct classes: 1. Air entrainers 2. Water reducers 3. Retarding 4. Accelerating 5. Speciality admixtures 2.1.1 Air Entrainers. Air entrainment admixtures work by purposely placing microscopic air bubbles into the concrete. This results in air entrained concrete which contains billions of microscopic air cells. These air cells then work ...