Normal-setting water-reducing admixtures

The normal water-reducing admixtures allow a reduction in the water-cement ratio at a given workability without significantly affecting the setting characteristics of the concrete. In practice, this effect can be utilized in three ways ... 

Conventional water-reducing admixtures used in marine construction are normally of the set-retarding type. The use of air-entraining agents in conjunction... 

The setting of concrete as defined by the stiffening times in BS 5075 Part 1 for concrete containing these admixtures must be within 1 hour of the equivalent plain concrete mix. In practical terms normal water-reducing admixtures can be regarded as not affecting the setting characteristics of the concrete. 

Chemical admixtures They are generally water-soluble, added mainly to control setting and early hardening of fiesh concrete, and to reduce water requirements. Chemical admixtures include accelerators, normal water reducers, superplasticizers, and retarders. The accelerators may contain calcium chloride, alkali hydroxide, calcium formate, calcium nitrate, etc. Examples of retarders are Na, Ca, or NH4 salts of lignosulfonic acids, hydroxy carboxylicacids,orderivativesofcarbohydrates.Normal water reducers may contain salts of refined lignosulfonic acids, hydroxycarboxylic acids, hydroxylated polymers, etc. Superplasticizers may contain sulfonated melamine formaldehyde, sulfonated naphthalene formaldehyde, car-boxylated synthetic polymers, etc. 

---