Design of high strength concrete mixes

Abstract

High strength concrete offers many advantages in the construction of high-rise buildings and bridges. In many countries, concrete strengths higher than 40 MPa are widely produced on commercial basis using normal aggregates and cement. Use of chemical and mineral admixtures has become an integral part of producing high strength concretes. At present, normal strength concrete is used in reinforced concrete construction in Sri Lanka. As the current trend for high rise buildings and the use of precast concrete is expected to increase, there wall be a greater demand in Sri Lanka for high strength concrete. A study was undertaken at the University7 of Moratuwa to examine various approaches for developing high strength concrete and to achieve concrete strengths higher than 40 MPa using only locally available materials. A high range water reducing admixture presently available in the market was used to reduce water/cement ratio of the concrete mixes while achieving sufficient workability. Compressive strengths up to 65 MPa w7ere achieved using locally available cement, sand and coarse aggregates with moderate dosages of water reducing admixture.