2 - Development, testing, and numerical simulation of ultra-high performance concrete at material level

Abstract

Development, testing and material modeling of an advanced ultra-high performance concrete (UHPC) material are presented in this chapter. The new concrete material is distinguished from previous development by the inclusion of the nanoparticles. It was noticed that addition of nanoscale size particles results in significant improvement of material properties without much change of the material composition. This study focuses on influence of fiber material addition and nanomaterial addition on mechanical properties of UHPC material. Different kinds of steel fiber material with varying volume fractions are considered in the material design, in combination with different nanomaterials at varying weight dosages. Static material tests are carried out to understand material strength and ductility. Uniaxial compressive tests and flexural tensile tests reveal the exceptional material strength, ductility, and energy absorption capability. Because the material aims at improving the structural performance under extreme loading conditions, dynamic material properties are also of significant importance. Split Hopkinson Pressure Bar (SHPB) tests are conducted on UHPC samples; dynamic compression tests and split tensile tests are studied and compared with static material strength to obtain the dynamic increase factor that is critical in the design of material and structures against dynamic loads. Three-dimensional (3D) mesoscale model with consideration of both the concrete matrix and fiber phase is established. Model calibration is conducted in comparison to static material test results, and further validation is obtained through SHPB split tensile test simulation. The proposed 3D mesoscale model can effectively model the material behavior, especially the post-yielding ductility.