Adverse effects due to improper application :
Admixtures are used extensively to produce high workable, high strength high performance and highly durable concrete with minimum cost. However, these admixtures are not used judiciously and with the poor knowledge of admixture among engineers at site results in the following adverse effect on concrete.
Rapid slum loss : This effect general observed in rich mixes with higher cement content and it can be reduced by adding booster dosages at different intervals.
Severe segregation/bleeding : This is generally observed in lean mixes with low cement content and depends on dosage of admixture. This can be minimized either by reducing admixture dosage or by increasing content of fine in the concrete.
Over retardation : This effect a noticed when the admixture is added beyond the specified dosage and it would effect the construction schedule, result in low strength development at early age. However ultimate strength of the concrete remains same.
Plastic shrinkage : This is general observed in large floor slabs of this sections and due to excess evaporator of water from the surface of the concrete at high temperatures are continuous breezing. However the plastic shrinkage cracks are determental to structures.
Effect of CaCl2 on setting time of OPC