Effect of modified lignosulphonate superplasticizer on workability retention and initial setting of cement pastes

Abstract

This paper presents an experimental study on the effect of a newly developed modified lignosulphonate (PLS) superplasticizer on the workability retention and initial setting time of cement pastes in comparison to those of polycarboxylate (PCE) and naphthalene (SNF) superplasticizers. The workability retention was monitored by yield stress and effective viscosity of the pastes. The initial setting was determined by penetration depth in cement pastes. Different dosages of the superplasticizers were used to obtain cement pastes with yield stress < 6 Pa at 30 minutes at given water-to-cement ratios of 0.26 and 0.32. The results indicate that the paste with the PLS admixture had longer workable time and initial setting time than that with the PCE and SNF admixtures. Although the longer workable time is beneficial for hot weather concreting, the longer initial setting time of such material has to be taken into consideration where early strength development is essential.