Fracture Resistance of Alkali Activated Concrete under the Mixed Mode I/II Load Conditions

Abstract

Nowadays, traditional concrete mixture uses as a binder well known Portland cement. However, the production of the Portland cement is not environmentally friendly, due to high production of CO2 in the fabrication process. In recent years, there are some trends to use secondary materials as a binder or as replacement of aggregate in the process of making the concrete mixture. This modified material uses alkali reaction in the hardening of fresh mixture, therefore an alkali activated concrete (AAC) term is used. This AAC is then used in formwork as it was traditional concrete, due to similar properties. Despite the use of advanced material, standards for structural design do not provide any instruction for practical application. Subsequently, the knowledge of fracture of this material is limited. The fracture mechanical properties help to perform advanced structural analysis, especially when some of the structural elements have a crack. The load presence on the structure can be divided into tensile, shear, and into combination of tension and shear. Therefore, it is necessary to perform test, which covers mixed mode I/II loading conditions. One of the tests usually used for the evaluation of fracture resistance of concrete is the Brazilian disc test with a central notch. This contribution evaluates the fracture resistance of alkali activated concrete, which will be used as a possible replacement for traditional structural concrete with cement binder, subjected to mixed mode I/II loading. The generalized maximum tangential stress (GMTS) criterion was used for the evaluation of the fracture resistance curve.Nowadays, traditional concrete mixture uses as a binder well known Portland cement. However, the production of the Portland cement is not environmentally friendly, due to high production of CO2 in the fabrication process. In recent years, there are some trends to use secondary materials as a binder or as replacement of aggregate in the process of making the concrete mixture. This modified material uses alkali reaction in the hardening of fresh mixture, therefore an alkali activated concrete (AAC) term is used. This AAC is then used in formwork as it was traditional concrete, due to similar properties. Despite the use of advanced material, standards for structural design do not provide any instruction for practical application. Subsequently, the knowledge of fracture of this material is limited. The fracture mechanical properties help to perform advanced structural analysis, especially when some of the structural elements have a crack. The load presence on the structure can be divided into tensile, shear, and into combination of tension and shear. Therefore, it is necessary to perform test, which covers mixed mode I/II loading conditions. One of the tests usually used for the evaluation of fracture resistance of concrete is the Brazilian disc test with a central notch. This contribution evaluates the fracture resistance of alkali activated concrete, which will be used as a possible replacement for traditional structural concrete with cement binder, subjected to mixed mode I/II loading. The generalized maximum tangential stress (GMTS) criterion was used for the evaluation of the fracture resistance curve.