The PhD dissertation of researcher Mohammed Saber Abdul Hassan was discussed at the College of Engineering, University of Basrah, Department of Civil Engineering, entitled EFFECT OF INCORPORATING HEMATITE POWDER ON TORSIONAL BEHAVOIR OF HIGH STRENGTH FIBER REINFORCED CONCRETE MEMBERS The purpose of this study is to investigate the effect of incorporating hematite powder on themembers made from high strength concrete strengthened by steel fibers and subjected to pure torsion. In addition to find the ratio of hematite powder that will provide the maximum strength against pure torsion, it is also included specify the shape of steel fiber with acceptable ratio will lead to optimum torsional strength without implementation problems. The specimens of this study were classified as beams with and without hollow, the dimensions of the beam are (200 x 200 mm) with total length (1200mm), and the test region length is (800mm) for all specimens (beams), but the dimensions of hollow cross-section were varied.
Finite element method via ANSYS 18.2 software was used to verify the experimental results for the beams of this study. To represent the materials, (SOILID65) was used to represent the concrete, (LINK180) was used to represent the main and transverse reinforcement. Steel fiber has been represented through concrete’s properties, in addition, smeared element (REINF-265) was used to represent the steel fiber. The effect of hematite powder was taken into account through the properties of the concrete.
The results showed that adding steel fiber led to enhance the cracking and ultimate torque, as well as improved the properties of the concrete such as compressive and tensile strength. Adding hematite powder as a cement replacement contribute to enhance the first cracking and ultimate torque as well as the concrete properties, the highest first cracking and ultimate torque was gained at ratio of hematite 2.5% with mixed steel fiber ratio 1.5%. Experimental results showed that the first cracking and ultimate torque increased when reducing the size of hollow in presence of hematite powder, and the beams with circular hollow have torsional resistance higher than the beams with square hollow. Transverse reinforcement effect found neglectable on first cracking torque and led only to increase the ultimate torque, but in case of adding hematite powder with transverse reinforcement, both first cracking and ultimate torque increased. The results of finite element method were compared with the experimental results and showed good agreement
