chapter  2
20 Pages

The Use of Superplasticizers in High Performance Concrete

ByP.-C. Aitcin

Superplasticizer variability seems to be less than that of Portland cement because they are fabricated from a limited number of fairly pure raw materials in a straightforward process. The amount of superplasticizer molecules consumed during the first moments after mixing corresponds to what has been qualified as cement/superplasticizer compatibility. In order to facilitate concrete delivery and to save money, it is judicious to use the double introduction technique, in which a certain amount of superplasticizer is added at the plant in order to obtain at the end of mixing a slump of 100 to 150 mm. The first dispersing molecules, more commonly water reducers, were produced from papermill waste and were called lignosulfonates. Concrete should have enough water to develop the full hydraulic potential of the cement while providing the rheology needed for easy placement. Researchers and concrete producers devote a lot of effort in the field because they are committed to delivering high-performance concrete with ever lower water/cement ratios.