What are the examples for the chemical admixtures that are used in the ready mixed concrete?
Chemical admixtures are materials in the form of powder or fluids that are added to the concrete to give it certain characteristics not obtainable with plain concrete mixes. In normal use, admixture dosages are less than 5% by mass of cement, and are added to the concrete at the time of batching/mixing. The most common types of admixtures are: * Accelerators speed up the hydration (hardening) of the concrete. Typical materials used are CaCl2 and NaCl. * Retarders slow the hydration of concrete, and are used in large or difficult pours where partial setting before the pour is complete is undesirable. A typical retarder is sugar (C6H12O6). * Air entrainments add and distribute tiny air bubbles in the concrete, which will reduce damage during freeze-thaw cycles thereby increasing the concrete’s durability. However, entrained air is a trade-off with strength, as each 1% of air may result in 5% decrease in compressive strength. * Plasticizers (water-reducing admixtures) increase the workabi
