Q.: When using high range water reducers in 3000-psi or 4000-psi concrete we ordinarily introduce the admixture at the plant instead of at the jobsite, though many experts advocate adding it at the site. Does anyone add high range water reducers at the plant when they are making high strength concrete?

A.: It has been reported that in the Chicago area it has been common to add the superplasticizer to high strength concrete at the plant. In Chicago, the plant is typically only about 20 minutes from the job so it is possible to discharge the concrete within 50 minutes after batching. If superplasticizer is batched at the plant it is always added at about the same age and this gives the supplier more confidence in the degree of control.