DESIGN OF HIGH STRENGTH CONCRETE MIXES

Abstract

It was the advent of prestressed concrete on the construction scene that triggered interest in HSC. The increased use of precast units, nuclear containment vessels, high rise buildings and self •_ supporting structures made further demands on this technology. HSC are being increasingly used for both on-land and off-shore applications. The definition of HSC varies with lOcation and time. The line dividing medium-strength concrete, and 'HSC, too, has been scaled upwards progressively. It could be defined in a general way as concrete which possesses compressive strength properties which are difficult to obtain using local materials and practices. The selective use of materials, a different approach in the mix design procedure, special attention to compaction of concrete and a more rigorous quality control are essential to the production of HSC. With the advent of high strength cements, mineral admixtures and chemical admixtures, it is now possible to produce HSC only by normal methods. The objectives of the preSent study are to design HSC mix using the locally available materials and study the effect of type of cement, aggregate and different replacement dosage of fly ash on the strength development characteristics of the HSC mixes. Ten different mixes were cast by varying the cement, coarse aggregate and fly ash content. The replacement of cement by fly ash reduced the 28 day compressive strength and the rate of development of strength at early ages of the HSC mixes, but the workability of-the. mixes increased marginally. The type of coarse aggregate used had no. significant effect on the strength development characteristics of HSC mixes.