Effect of Superplasticizer on Flow, Compressive Strength and Tensile Strength of Mortars

Abstract

The objective of this research was to study the effects of superplasticizer on the flow, the values of the compressive strength and the tensile strength of mortars. In this study two brands of Portland cement of type 3 and one brand of naphthalene-based superplasticizer were used. The dosage of the superplasticizer was in the range of 0 - 2.1 % of cement by weight. Specimens of mortar were cast according to ASTM C109 standard. The water-cement ratio was 0.485 and the ratio of cement to sand was 1:2.75 by weight. The fineness modulus of sand was 2.55. Specimens for the compressive strength were cubes of 5´x5´x5 cm and specimens for the tensile strength were of the size 7.5´x4.5x´2.5 cm. Specimens were tested at the ages of 1, 3 and 7 days. The results of the study for mortars of two brands showed that with the increment of superplasticizer from 0 - 1.9 % flow, the values of the compressive strength and the tensile strength trended to increase. However, the segregation occurred with superplasticizer higher than 1.9 %. In these cases, the flow, the values of the compressive strength and the tensile strength decreased with respect to the increment of the superplasticizer.