DESIGN AND EXPERIMENTAL INVESTIGATION OF HIGH STRENGTH CONCRETE USING FLY ASH AND SILICA FUME

Abstract

This research study presents the design and results of experimental work on compressive strength and workability of High Strength Concrete containing fly ash and silica fume as mineral admixtures following the guidelines of BIS code 10262:2009. The aim of the study was to design high strength concrete having compressive strength of the order 95-105 MPa and above with good workability by varying the percentage of replacement of cement by two different mineral admixtures. The work focused on concrete mixes having a constant total binder content of 635 kg/m3 at constant dosage of superplasticizer. The compressive strength test were conducted upto an age of 90 days. Total eight mix were casted having (0, 20%, 25% and 30%) fly ash and (5% and 10%) silica fume. One mix contained fine fly ash in order to investigate its effect on the properties of concrete. And apart from this one ternary blended concrete mix having both fly ash and silica fume together was also tested. The findings of this research indicate that both flyash and silica fume play a significant role in the long term strength gain of concrete. Fly ash reduces the early age strength gain whereas silica fume due to its high reactivity rapidly enhances the early strength gain in concrete. On one hand, addition of flyash increases the workability of mix while on the other hand addition of silica fume follows a reverse trend. Also the ternary blended concrete mix produced satisfactory results with intermediate workability and compressive strength equivalent to mix having cement content of 635 kg/m3.