Effect of composition of portland cement on the performance of superplasticizer admixture

Nowadays, superplasticizer admixtures have become one of the major ingredients of concrete in ready-mixed concrete industry. In this study, it was aimed to determine the performance of superplasticizer admixtures, which in turn depends on the properties of cement. Thus, the effect of cement-superplasticizer interaction on the initial fluidity and the loss of consistency was investigated. In the experimental study, 18 ordinary Portland cements CEMI 42.5 (from 18 cement plants), a sulfate resistant cement SDÇ 32.5, a white Portland cement BPÇ 42.5 and 4 different naphthalene sulfonate based superplasticizer admixtures were used. Flow time and flow diameter values of cement pastes were determined from ?Marsh Funnel? and ?Mini Slump? tests, respectively. Concrete mixtures were prepared using only one of the admixtures. The slump, slump loss and air content of fresh mixtures as well as the compressive strength of hardened concrete at different ages were determined. It was concluded that, the initial fluidity of the paste was affected by the C3A/Na2Oequivalent ratio and C4AF content of the cement. Increasing in the C3A/Na2Oequivalent ratio reduced the flow time while increasing in C4AF content increased the flow time. It was also clearly observed that the effect of properties of superplasticizer on the initial fluidity is negligible compared to that of cement. However, the properties of both cement and superplasticizer were found to be effective on the loss of consistency of the mixtures. Relatively higher C3A/Na2Oequivalent ratio of cement reduced the loss of consistency. It should also be noted that there is a good correlation between the initial fluidity of the pastes and concrete mixtures. Keywords: Superplasticizer, cement, cement-superplasticizer compatibility, Marsh funnel, mini slump, loss of consistency, compressive strength.