EFFECTS OF SUPERPLASTICIZER ON WORKABILITY AND FLEXURAL STRENGTH OF AUTOCLAVED CALCIUM SILICATES

Investigations are reported into the effects of superplasticizer type and dosage on the workability of a cement-silica mix with a range of l iquid/solids ratios and on the flexural strength after autoclaving. Th e overall objective was to achieve as high strength as possible from p ourable mixes. The results showed that flexural strengths as high as 2 5 MPa could be achieved by using an optimum combination of superplasti cizer type, dosage and liquid/solids ratio. Such mixes had excellent f low characteristics enabling direct casting without any assistance fro m vibration. The dosages of superplasticizer per unit weight of cement plus fine silica, were found to be similar to those for normal cement , with 2% giving optimum benefits. A critical 0.25 liquid/solids ratio was found below which strength decreased and above which the conventi onal dependency found with cementitious systems was observed.