Análise comparativa da tensão limite de escoamento de argamassas por meio da técnica de Pashias e reometria rotacional

Abstract

Studies about the rheological behavior of cementitious materials, especially mortars and concretes, have been developed to improve the quality and durability of these materials as well as prevent any future problems in the hardened state. The rotational rheometry is the classic test for the rheological characterization of cementitious materials, because it allows to infer about the level of yield stress and apparent viscosity of the material. The rotational rheometers are, however, costly equipments, which led to the development of alternative me-thods for low cost, as the Pashias technique. The Pashias technique is a modification of the slump-test proce-dure in order to characterize, rheologically, the materials by single determining of the yield stress. The work developed aimed to determine the yield stress of mortars from compositions of high performance concretes (HPC) dosed by the concepts of rheology and particles packing. For this, it was used the classic rheometric test and the Pashias technique (cylinder), in order to compare the results, and evaluate the capacity of alterna-tive technique in determining the yield stress of mortars. The comparison of the results obtained by different rheological test methods showed a good ability of the Pashias technique (alternative technique) to evaluate the of yield stress parameter of mortars (with errors ranging from 1% to 20%). In addition, was observed that the mortar obtained from HPC dosed by the concepts of particles packing appeared more fluid and workable, with less yield stress.