Experimental Study On Fracture Properties Of Concrete Using Wedge-Splitting Test

Concrete in today's world is mostly used as building materials,and now its fracture and damage research is a hot issue in fracture mechanics study.Because of micro-cracks in the concrete and sub-critical of the expansion of concrete,its typical load-displacement curve shows non-linear characteristics.Many scholars put forward a variety of concrete fracture model,and the fracture energy is a key concept in concrete fracture mechanics study,an accurate determination of concrete fracture energy is an important part of the concrete fracture mechanics study.Wedge-splitting method is commonly used to determine the fracture energy of concrete. Since no standard is now available regarding wedge splitting test,researchers often turn to formulae of compact test to determine fracture properties of concrete,where no consideration is given to vertical loads,i.e.,vertical component of force introduced by the wedge,the weights of steel loading block and specimen itself.An analysis was made to study possible influences of these factors on fracture properties of concrete when supports are placed in different positions,including single and dual supports.And data from wedge splitting test was used to verify these influences on fracture toughness.Results show that for ordinary wedge splitting specimen used in the laboratory,the fracture properties estimated will be close to the true values when the support is fixed vertically in the same plane with the force transferred by the wedge.The double-K fracture parameters are calculated,which values are all essentially keep constant when the height of wedge-splitting specimen varieties.They also have nothing to do with the ligament height for a certain dimensional specimen.It is confirmed that the double-K fracture parameters is the description of the material properties inherent in concrete.An analysis is made to study possible influences of the vertical force on fracture energy of concrete.The method of calculating fracture energy is improved and fracture energy was calculated.Fracture properties on fracture process zone are investigated by considering the influence of specimen boundary condition.An explanation is presented for the specimen size effect on specific fracture energy by introducing the concept of fracture-work-method.The experimentation was done in a different ligament of the length of the wedge splitting tensile. The results showed that,because of border restrictions,the local fracture energy spread in a non-uniform manner along the ligament length when the specimen failed,which led to the size-dependence of the traditional fracture energy.Furthermore,the computed value of the proposed fracture energy was kept approximately constant irrespective of the specimen size. The parameter reflecting the boundary influence,was also dependent.When the specimen size is large enough the local fracture energy measured by the test is the real fracture energy of concrete,which is the limit of the testing value.