Workability retarding water-reducing agents

The superplasticizers are a special category of water-reducing agents in that they are formulated from materials that allow much greater water reductions, or alternatively extreme workability of concrete in which they are incorporated. This is achieved without undesirable side effects such as excessive air entrainment or set retardation. 

Water-reducing agents, also called plasticizers, allow a given degree of workability to be achieved at a lower w/c ratio. Conventional water reducers allow w/c to be decreased by 5-15%. To achieve greater decreases, they would have to be used at concentrations that would also cause excessive retardation, excessive air entrainment or flash setting. More powerful water reducers, called superplasticizers, allow w/c to be decreased by up to about 30 /o these are considered in Section 11.4.2. 

Admixtures are substances that are added during the mixing process in small quantities related to the mass of cement, in order to improve the properties of fresh or hardened concrete [7,8]. The most utilised admixtures are water reducers and superplasticizers that may be added to improve the workability of concrete or reduce the amount of mix water accelerators that are used to increase the rate of development of early strength of concrete set-retarders that reduce the setting time of concrete air-entraining agents that increase the freeze-thaw resistance of concrete (Section 3.1). Recently, corrosion inhibitors have been developed in order to increase the corrosion protection of embedded steel these will be treated in Chapter 13. 

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