The Coupled Effect of Nano Silica and Superplasticizer on Concrete Fresh and Hardened Properties

Abstract

The The effect of individual and combined additions of both nano silica (NS) and polycarboxylate-ether superplasticizer (SP) admixtures on concrete mixes were studied. Twenty concrete mixes were prepared, keeping the water/cement ratio constant at w/c = 0.40, with different amounts of SP admixture, and NS. the superplasticizer was studied in the range of (0 - 0.88)% (over cement weight), nano silica additions were tested at (0 - 3.00)% range (over cement weight). Early, and late compressive strengths, as well as results of fresh concrete (slump) test of formulations were evaluated by means of design of experiments, in order to identify the primary factors and their interactions on the measured properties. The most desirable NS and SP % were determined. The results showed that regardless of the used NS percentage, the higher compressive strength results were reached at, or around SP observed saturation dosage (0.66% by weight cement). The statistical approach applied here enabled to develop relations, which could adequately describe the dependency of both the compressive strength, and slump on the composition of NS, and SP concretes. These relations were presented as contour plots, which from a practical point of view could serve as a basis for mix design.