DURABILITY ADVANTAGE OF CONCRETE WITH TERNARY CEMENT BLENDS AND APPLICATIONS IN INDIA

This paper makes a case for ternary combination of ordinary Portland cement (OPC), fly ash and silica fume as a sustainable and efficient binder system for structural concrete. In addition, superplasticisers are needed to ensure flowability and viscosity-modifying admixtures (VMA) are required for cohesiveness. Characteristics to meet the performance requirements of concrete for various strength grade and exposure conditions are established by laboratory investigations and case studies of applications in infrastructure projects in India, which are presented. Considerable durability advantage that accrues from use of ternary cement blends in concrete mixes is emphasized in the paper. Use of less OPC content in the concrete mix means lower carbon footprint and lower thermal cracking. Strengthening of aggregate-matrix interface results in proportionately higher tensile strength and crack-arrest property. Dense microstructure lowers permeability and chloride diffusion coefficient, and resists ingress of chlorides and other chemical salt solutions. Sulphate resistance results due to pozzolanic reactions and lower C(3)A content. All in all, more durable concrete construction with longer service life results. Construction industry in India has now accepted the use of ternary blends of cementitious binders in concrete constructions. A number of case studies presented indicate the trend.