HIGH PERFORMANCE CONCRETE FOR HIGH-RISE BUILDINGS: SOME CRUCIAL ISSUES

Abstract

High-rise building construction has been an important driver for the revitalization of urban centers throughout the world. The paper briefly summarizes the unprecedented growth in tall building construction across the globe during the past few decades. Review of tall building scenario reveals two interesting trends. Firstly, the centre of gravity of tall building construction which had already shifted from North America to Asia, is getting strengthened in the latter region, and secondly, structural concrete has emerged as a dominant material of construction of tall buildings, either in a stand-alone form or as a part of composites, surpassing structural steel. The use of High-Strength, High-Performance Concrete (HSC/HPC) has proved to be a boon for high-rise building construction. HSC and HPC are engineered concretes having vastly improved properties. With such type of concretes, it is possible to achieve high compressive strengths that are useful in reducing the sections sizes of members and high modulus of elasticity for controlling deflections. Further, these concretes can be designed to provide immensely improved long-term durability. Thanks to the availability of a latest generation chemical admixtures, it is now possible to pump HSC/HPC to greater heights. In India, the scarcity of land in metropolitan centers is driving the land prices sky high and is compelling developers and builders to build taller buildings. With the rise in the stock of tall buildings in India, the use of HSC/HPC is also on the rise. The author briefly reviews the broad trends in the use of HSC/HPC in India with specific reference to the projects he has been associated with recently. Selection of appropriate ingredients of concrete and mix proportioning methodology are the crucial parameters for achieving the desired properties of HSC/HPC. Even minor variations in the properties of ingredients and testing regime affect the fresh and hardened properties of concrete. For HSC/HPC the author makes a strong plea to use manufactured sand having lower variations in its fines content. Considering that rheology of HSC/HPC is of critical importance, the author emphasizes that it is essential to resolve the cement-admixture compatibility issue in the initial stage itself. He suggests that use of cement having low C 3 A and low C 4 AF contents would prove to be beneficial. Finally, the author highlights the urgent need of developing appropriate guideline documents for HSC/HPC in India.