Propriétés mécaniques et microstructurales de nouvelles matrices à ultra haute performance (M.U.H.P.)

Abstract

Ultra high performance matrices contain large quantities of Portland cement and silica fume. Their delicate rheology requires an optimization of superplasticizer dosage as well as careful placing. However, few studies have been carried out on the anhydrous materials used. The main goal of this study was to design a cementitious matrix in which a large part of the Portland cement would be substituted by other mineral additive such as blast-furnace slag or fly ashes, taking into account their effects on flow and compressive strength. Afterwards, a mix containing slag was studied. Aside from the evolution of the characteristics of the fresh and hardened material as a function of the water/binder ratio and the superplasticizer content, the consequences of the thermal curing at 20 and 90ÀC was also investigated, the results being compared to that of a reference {cement + silica fume}. The obtained results enable to study the evolution of the matrix microstructure with the slag content or the thermal curing using a new technique, Nuclear Magnetic Resonance (NMR). It showed that the polymerization degree of the C-S-H in the cured matrices increases with the slag content. Links could also be made between compressive strength and NMR results, emphasizing the effects of hot-water curing on cementitious matrices.