الفهرس 
L ITERATURE R EVIEW
R ESEARCH P LAN , C ONSTRUCTION , AND T ESTING P ROCEDURESOnly 14 pages are availabe for public view
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Abstract
Reinforced concrete structures are vulnerable to high temperature conditions such as those during exposure to fire. At elevated temperatures, the mechanical properties of concrete and reinforcing steel as well as the bond between steel rebars and concrete may significantly deteriorate. The decrease in the bond strength may influence the moment capacity of the reinforced concrete elements. The assessment of bond strength degradation is required for structural design of fire safety and structural post-fire repair. Therefore, there is a need to investigate the bond behavior between concrete and steel rebars after fire exposure and to study the most suitable repairing techniques and materials to restore the bond strength between concrete and reinforcing steel after fire exposure.
This thesis contains an experimental and analytical investigation on the residual bond strength between concrete and steel rebars after fire exposure and normal cooling to room temperature. Also, it discusses the effectiveness of using different repairing techniques and materials to restore the bond strength between concrete and steel rebars. The bond tests were carried out using beam end specimens. The test parameters considered in the current research include: exposure condition, concrete class, rebar type, rebar size, rebar location, repairing technique and repairing material. Two different exposure conditions were applied to the specimens, namely fire exposure and ambient exposure. In the fire condition, all the fire damaged specimens were subjected to a heating regime before testing in bond while in the ambient condition, the specimens weren’t exposed to any heating regimes before testing. Concrete strengths included are 20 and 40 MPa. The different types of rebars considered are ribbed and plain rebars. Rebar sizes considered are 22, 16 and 8 mm. The rebar locations considered are outside and inside with respect to the transverse bars.
Two different repairing techniques were conducted in this study. The first technique was deep repair where the deteriorated concrete layer was removed by breaking off at least 25 mm behind the tested rebar then replaced with the repairing material. The second technique was shallow repair in which the deteriorated concrete up to the center line of the tested rebar was removed. Four different repairing materials were used in the study namely; concrete, polypropylene Fiber reinforced concrete, polymer modified cement mortar and commercially available fiber reinforced polymer modified cement mortar.
The experimental test results showed a significant loss up to 70 % in the bond strength between concrete and steel rebars after fire exposure with a dramatic change in the bond stress-slippage behavior. Considering the repair of fire damaged specimens, the shallow and the deep repair techniques using the polymer modified cement mortar, for the specimens involving plain rebars restored 77% and 93%, respectively of the original bond strength whereas for the specimens involving ribbed rebars, the highest observed restoration was 48.7% and 65%, respectively of the original bond strength. The specimens repaired with deep repair using the concrete restored up to 83% of the original strength, whereas fiber reinforced concrete and fiber reinforced polymer modified cement mortar restored about 86%and 96% respectively of the original bond strength.
Based on the experimental results, an analytical expression was proposed to predict the bond stress-slippage relationship and for computation of the residual bond strength between concrete and steel rebars after fire exposure. Also, a heat transfer analysis was carried out using FEM to obtain the temperature distribution within the cross section of the fire exposed specimens.