Método de dosagem de concretos de alto e ultra-alto desempenho autonivelantes

Abstract

High and ultra-high performance concretes (HPC and UHPC, respectively) are cementitious composites that have superior characteristics to those of traditional concretes, such as greater durability and workability, in addition to improved mechanical properties. To obtain this high performance, the homogeneity of the composite material and a denser particle packing are sought, through the choice of raw materials and their adequate supply. Despite superior properties, its large-scale application is limited by the absence of a simple and widely accepted dosing method. There are numerous theories and packing models that aim to obtain high compactness, however they disregard the morphology and allow between particles. In view of these restrictions, the present work proposes an empirical method for dosage of self-levelling HPCs and UHPCs, produced from Portland cement. The steps suggest optimizing the ratio between the binders, followed by engineering the saturation content of the additive and, developing the aggregate content for different water/binder ratios, in order to achieve a spread between 320-360 mm. This method tolerates producing concretes with self-leveling characteristics, with resistances in the range of 80-100 MPa at 3 and 28 days. However, for this dosage method, with low water/binder ratios and very different aggregate contents, Abrams' Law does not apply.