Approaches and strategy development towards more sustainable ultra-high-performance concrete

Abstract

The main research objective of this thesis is to investigate how the use of UHPC can contribute to improving the sustainability of the concrete industry by investigating alternative approaches and develop a comprehensive strategy. Some cost aspects have been discussed to indicate whether the strategy is commercially viable. The research involved six studies: Paper I describes a background study to identify directions for a more sustainable concrete industry. Papers II–V report on how approaches to improve sustainability influence the mechanical properties of UHPC. These studies include both literature reviews and experimental activities. Paper VI concludes the research by developing a comprehensive strategy to use UHPC for a more sustainable concrete industry. Because most of the CO2 emissions (about 95%) from UHPC materials originate from the production of cement and micro steel fibres, the more efficient use of these materials is a vital step. Several different approaches have been investigated and determined to be efficient. Some approaches identified from attempts aimed at achieving a more efficient application of cement in normal concrete may be transferred to UHPC. These include partial substitution with both binding and inert materials, combined with better particle packing. The use of steel fibres was observed to have the potential to be more effective by enhancing the pull-out properties using longer or deformed fibres and hybrid fibre combinations. The use of industrial by-products or construction and demolition waste as partial replacements for cement or as aggregates was also observed as being feasible. The local development and production of UHPC builds competence, which is vital for the widespread use of UHPC. The research concludes with the formulation of a comprehensive strategy on how the development and use of UHPC can contribute to improving the sustainability of the concrete industry.