Towards a more common use of Ultra-High Performance Concrete (UHPC) – development of UHPC for ready-mix and prefabrication concrete plants

This study addresses the development of ultra-high performance concrete (UHPC) suitable for a mass production in conventional ready-mix and prefabrication concrete plants. In order to facilitate the production process, curing regime and to minimize the costs, no additional treatments (e.g. thermal or steam curing) are applied to the concrete. The concrete composition is optimized using the modified Andreasen & Andersen packing model. Fine and coarse aggregates in the size range of 0-6 mm are used. Steel fibres are added to increase concrete ductility. Silica fume and limestone powder are applied to improve concrete fresh behaviour, mechanical properties as well as durability. The developed concrete has self-compacting properties. The mixtures are designed and tested in the laboratory, yielding at very high mechanical properties as well as high durability. Subsequently, one concrete composition is produced in a ready-mix concrete plant (three batches of 1.5 m3 each) and another one in a prefab plant (two batches of 0.22 m3). A number of test samples are prepared and analysed from each batch. The developed concretes have very high compressive strength (200 MPa), elastic modulus (70 GPa) as well as superior durability indices (e.g. chloride ingress and carbonation resistance). Moreover, for demonstration, two concrete bridge-deck slabs (5 m x 3 m, 45 mm thick) are cast from the ready-mix concrete and one small bridge (3 m x 1.4 m, thickness of 45-55 m) is cast in the precast plant. The two concrete bridge slabs are proof-loaded under static and dynamic conditions, demonstrating a great performance of UHPC. The presented findings show that UHPC can be successfully produced in conventional concrete plants and the obtained results prove the outstanding potential that UHPC has for a more common application in the construction practice.