The effect of a polynaphthalene sulfonate superplasticizer on the contribution of the interfacial transition zone to the electrical resistivity of mortars containing silica and limestone fine aggregate

The effect of the varying dosages of a polynaphthalene sulfonate superplast icizer on the electrical resistivity and the interfacial transition zone (I TZ) characteristics of mortars containing reactive and non-reactive fine ag gregates was investigated, using AC impedance spectroscopy and electrical c onductivity models. The water-to-cement (W/C) ratio used was 0.45. The sand -to-cement (S/C) ratios ranged from 0.5 to 2.5. Superplasticizer contents b y mass of cement were 0% to 1.5%. The results showed that the effect of the superplasticizer on the ITZ of the mortars was dependent on not only the d osage levels of the superplasticizer, but also W/C ratio, S/C ratio and typ e of aggregate. The improvement of the interfacial zone due to the presence of superplasticizer in low W/C ratio mortars does not necessarily occur in high W/C ratio mortars due to possible bleeding, segregation and increased water layer thickness around the aggregate. The number of aggregate-paste interfaces may also be a contributing factor. (C) 2000 Elsevier Science Ltd . All rights reserved.