Estudo do cisalhamento puro em concretos com gradação funcional

Abstract

Concrete is one of the most widely used materials globally. However, due to its heterogeneous nature, there is no guarantee that the material can adequately withstand the various stresses to which it may be subjected. The quest to expand and optimize the application of concrete has been the subject of research in some studies on functional gradient concretes, which exhibit a gradient that can be continuous or layered. This concept aims to address challenges in various advanced applications where two or more materials with distinct characteristics are combined. This study presents three types of layered functional gradient concretes, comprising two or three layers, using self-consolidating concrete with natural aggregate (CAA) and two types of lightweight concrete, varying their foam content by 10% and 20% (CCE10 and CCE20). For these concretes, a shear test, specifically pure shear, was proposed and conducted to induce only shear stresses in the test. The goal was to evaluate the shear resistance of these concretes and analyze the adhesion between the layers. It was observed that the casting time significantly influences the achievement of layered gradient concrete. It was concluded that the time interval of 1 hour and 20 minutes to 1 hour and 30 minutes between the castings of CCE20 and CAA is the necessary time to obtain layered concrete. For the pure shear test on the individual concretes CAA, CCE10, and CCE20, the shear resistance results in the first molding were 9.41 MPa, 6.45 MPa, and 4.93 MPa, respectively, indicating a decrease in shear resistance with the addition of foam (voids). For the CCE1020 (2 layers), CCE20CAA (2 layers), and CCE1020CAA (3 layers) gradient concretes, the shear resistance results in the first molding were 5.84 MPa, 5.16 MPa, and 5.31 MPa, respectively, indicating a higher adhesion between the layers where anchoring occurred between the pores and voids of the concretes and that the time interval between the castings of CAA and CCE20 reduces the adhesion between these concretes.