STUDY ON WORKABILITY AND PUMPABILITY OF SUPERPLASTICIZED LIGHTWEIGHT CONCRETE.

The paper discusses effects of the superplasticizer on workability and pumpability of lightweight concrete, and some recommendations for accepting superplasticizer to lightweight concrete are also presented. Results of testing conducted under the study indicate that the slump-loss of superplasticized lightweight concrete with the lapse of time after addition of superplasticizer was as rapid as in the case of superplasticized normal-weight concrete. Increases of workability of superplasticized lightweight concrete with the increase of dosage of superplasticizer were larger than that of superplasticized normal-weight concrete. The optimum dosage of superplasticizer was 0. 3 to 0. 5% by weight of cement when the slump of base concrete was 15 cm. By delayed addition of the shrinkage, slump increased by 6 to 9 cm, but air content, bleeding, compressive strength and drying shrinkage were the same as those before addition. Slump-losses of the superplasticized concrete after pumping were greater than those of conventional concrete in both normal and lightweight concretes. Pumping pressure of superplasticized normal weight concrete was found to be 20% smaller than conventional concrete with the same slump. Additional results are included in the paper.