Pierre Richard

Composition of reactive powder concretes

Abstract Development of an ultra-high strength ductile concrete designated RPC (Reactive Powder Concrete), was made possible by the application of a certain number of basic principles relating to the composition, mixing and post-set heat curing of the concrete. RPC 200, which can be used under job site conditions similar to those for conventional high performance concretes, can be used in the construction of prestressed structures incorporating no passive reinforcement. RPC800 is suitable for precasting, and can achieve compressive strength values exceeding 600MPa. A value of 810MPa has been obtained with a mixture incorporating steel aggregate.

Hydration kinetics, change of relative humidity, and autogenous shrinkage of ultra-high-strength concrete

This research forms part of a vast experimental program designed to investigate the shrinkage and creep of compact reinforced composite (CRC), which is an ultra-high-strength concrete. In this paper, only results relating to autogenous shrinkage are presented. While shrinkage deformations were measured, cement hydration, pozzolanic reactions, and pore structure of concrete also were monitored to characterize the microstructural evolution of material. Very high autogenous shrinkage at an early age that stops 10 days after casting was observed. As far as we know, this sudden break in shrinkage kinetics has never been observed before in cement-based materials. The autogenous relative humidity measurements show high self-desiccation within the CRC. A relationship between autogenous shrinkage and self-desiccation of CRC is established and discussed.

Materials and their uses

New materials have been emerging in the industry for several decades. Recently, the research into materials has spread; the development of university and industrial laboratories, the use of physic and chemistry for their design give a new impetus to this research. A material apparently as common as concrete is no exception to this general trend. However, the economic aspect of research much always be kept in mind and performance objectives selected with discernment.