Durability Characteristics of Ultra High Performance Concrete

Abstract

There is an increasing demand of development of new type of concretes which have high strength, durability, improved serviceability and better economy for a larger span of time. Ultra High Performance Concrete (UHPC) also known as Reactive Powder Concrete (RPC), is a cementitious composite material with low water-binder ratios of less than 0.25 and an optimized gradation of granular constituents which provides an excellent alternative to this increased demand for high strength concrete. The characteristic compressive strength of UHPC should be greater than 120 MPa. UHPC shows irregular pore structure which helps in reducing the liquid permeability and thus, increases the durability when compared with other types of concrete. The advent of UHPC has led to development of new technologies and solutions which enables to create customized applications like lightweight structures, ultra-thin panels, multiplex shapes and curvatures which are difficult to create with the normal reinforced concrete. UHPC has great plastic and hardening properties which does not requires the use of reinforcement which further helps pre-casters to create structures with complex shapes with having high durability and overall less economy, and also little preservation is required in these types of structures. The aim of this study was to evaluate the compressive strength and durability properties like sulphate attack resistance and Rapid Chloride Penetration Test (RCPT) values of concrete mixtures incorporating supplementary cementitious materials like silica fume, nano silica and ground granulated blast slag (GGBS) or alccofine as a partial replacement of cement, along with three different percentages of steel fibers (i.e. 0.5%, 1% and 1.5%) with a water-binder ratio of 0.18. To understand the various properties of UHPC a comprehensive literature review is carried out which is assembled from various references representing many development, deployment efforts and research around the world. This investigation reveals that it is possible to achieve UHPC mixes with optimal usage of supplementary cementitious materials like silica fume, nano-silica and GGBS. Also, the mixes so developed provide excellent resistance to sulphate attack. In addition resistance to chloride penetration is found out to be very good, with all the mixes so developed falling under the ‘Very Low’ to ‘Negligible’ category as per ASTM C 1202.