Title: Effect of Various Types of Fibers on Bond Capacity Experimental, Analytical, and Numerical Investigations
Author(s): K. Noghabai
Publication: Symposium Paper
Appears on pages(s): 109-128
Keywords: bond; carbon fibers; high-strength concrete; fiber; non-linear fracture mechanics; polyolefin fibers; splitting; tension stiffening
This paper is based on two different experiments: !) Splitting tests on thick-walled concrete rings subjected to an inner pressure. 2) Pull-tension tests on deformed rebars embedded in concrete prisms. The experiments consider different aspects of bond between deformed rebars and fiber reinforced high-strength concrete (FRHSC). Tests according to 1) study mechanisms for spalling of the concrete cover, due to the radial pressure exerted to the concrete by the ribs of a rebar in tension. There are analytical models (based on nonlinear fracture mechanics) for capacity assessment of the ring. In the experiments according to 2), the bond forces decide the development of transverse cracks in the concrete. By these tests, the so-called tension-stiffening effect on rebars may be studied. In composing the FRHSC, five different types of fibers were used: 2 steel fibers (crimped and straight), 2 polyolefin fibers and one carbon fiber. The fibers were added to a HSC with an expected 28-days compressive strength of 120MPa. Volume fraction of fibers was 1% in all cases. FRHSC is here characterized by its response under uniaxial tension. By using the tensile load-deformation curve in available analytical and/or numerical tools (such as FEM), the effect of a fiber inclusion on the structural response may be explained. Both the analytical and FE-models used herein, seem capable to describe the physical events that take place in the experiments. Thus, it is promising that in order to achieve a desired performance in the test pieces ( and consequently with respect to a desired bond capacity), a fibrous concrete may be tailor-made for a purpose.