OPTIMIZATION OF ULTRA-HIGH-PERFORMANCE CONCRETE BY THE USE OF A PACKING MODEL

The concept of high packing density has been recently rediscovered, as a key for obtaining ultra-high-performance cementitious materials. First, this paper presents two models allowing to predict the packing density of a particle mix. These models are derived from the Mooney's suspension viscosity model. At a second step, considerations on the parameter to be maximized during the mix-design process are presented. Reference is made to the Maximum Paste Thickness concept, which leads to choose a fine sand for optimizing the compressive strength of cementitious materials. Then, an optimal material is sought, based on the following requirements: fluid consistency, classical components (i.e. ordinary aggregate, sand, Portland cement, silica fume, superplasticizer, water), and moderate thermal curing. A selection of mixes is made with the help of the Solid Suspension Model, and tests are performed in order to verify that the mix obtained is definitely optimal. The final result is the production of a fluid mortar having a water/binder ratio of 0.14 and a compressive strength of 236 MPa.