1 INTRODUCTION Use of high strength concrete for the construction of high-rise buildings and long-span reinforced and pre- stressed concrete bridges is wide spread. Features of high-strength concrete include high early-age and ul- timate strengths, low chloride permeability, hence improved resistance to aggressive environmental penetration. However, it is known to be less ductile compared to medium strength concrete. 1.1 Sustainability of concrete Generally, a typical high strength concrete mix con- sists of the cement content about 550kg/m 3 . With the use of superplasticizer, the water content could be significantly reduced (up to 30%) to produce worka- ble high-strength concrete and this consequently re- duces the cement content without affecting the strength of concrete. In addition, experience had shown that supplementary cementitious materials, such as, fly ash, ground granulated blast furnace slag (ggbfs) and silica fume, could be used as partial re- placement to cement without affecting the mechani- cal properties of concrete. Any reduction in cement content reduces the environmental impact of con- crete, considering the carbon dioxide liberated (1 tonne carbon dioxide per tonne of cement produced) and energy requirement associate with the produc- tion of Portland cement. The environmental impact of concrete can be further reduced if the aggregates used in concrete mixes from construction and demolition waste in- stead of virgin natural aggregates. This will help to minimize quarrying demand for natural aggregates. Therefore, a concrete mix consists of substantial amount of supplementary cementitious materials, as partial replacement to cement, and recycled concrete aggregate instead of natural aggregate can be consid- ered as concrete for sustainable construction. 1.2 Effectiveness of supplementary cementitious ma- terials in concrete Effectiveness of the supplementary materials is known to be a function of chemical composition, fineness, particle size distribution, temperature and moisture content of concrete. Silica fume due to its extreme fineness (about 16,000m 2 /kg) and high reac- tive silica content (over 95%) is highly effective in improving the strength and impermeability of con- crete compared to low fineness fly ash with the silica content around 50%. The pozzolanic reaction be- tween reactive silica and calcium hydroxide in con- crete (one of the hydration products of calcium sili- cates in cement) produces the pore-size and grain- size refinements in the hardened binder paste com- ponent of concrete. In addition, the filler effect was also found to contribute the improved hardened properties of con- High-strength self-compacting concrete for sustainable construction R. Sri Ravindrarajah Centre for Built Infrastructure Research, University of Technology, Sydney, Australia ABSTRACT: Concrete for sustainable infrastructure construction of civil engineering structures is required to use environmentally friendly concrete-making materials and to minimize both energy and manpower needs in concrete placing. With the intension of improving both environmental and economical sustainability, this study on self-compacting concrete with ground granulated blast furnace slag and recycled concrete aggregate was conducted. This paper reports the results of an experimental investigation into the production and proper- ties of high-strength self-compacting concrete mixes with a combination of Portland cement and ultra-fine slag (up to 50% of cement replacement) and with either natural or recycled concrete coarse aggregate. The strengths development and chloride migration coefficient was evaluated. The use of ultra-fine slag was found to improve the stability of self-compacting concrete independent of the type of coarse aggregate. The use of recycled concrete decreased the strengths and modulus of elasticity and increased the chloride permeability for the high strength self-compacting concrete.