Table 1 Mix. Proportions Proportions (kg/m 3 ) Aggregate w/c Water Cement Fine Coarse AE Agent (kg/m 3 ) 60% 180 300 790 1015 0.075 EXPERIMENTAL STUDY ON CORROSION EFFECT ON TIME DEPENDENCE OF BOND Nour-Allah HUSSEIN* 1 Louis A. DARMAWAN * 2 Ryoichi SATO * 3 and Yang YANG * 4 ABSTRACT: In this study the effect of corrosion on time dependent bond behavior was investigated experimentally. Reinforced concrete prism specimens were made of concrete with 0.60 water cement ratio (w/c) and were provided with two separate reinforcement steel bars arranged along their longitudinal axis. One of the steel bars with shorter embedded length was corroded electrolytically before performing pull out test. Bond stress level was chosen as a major factor for a corrosion of 5.5% percentage of mass loss. The results show that if bond stress level exceeds 62%, remarkable creep of bond takes place. Moreover, load history may have some effect on slip creep in presence of corrosion. KEYWORDS: Bond, Slip, Creep, Corrosion, Bond stress level. 1. INTRODUCTION Vast amount of data was accumulated for the effect of corrosion on bond behavior between steel reinforcement and concrete under instantaneous load. This data is very important for safety assessment of the constructions suffering from reinforcement corrosion. However, most of the structures are subjected to long-time load, and very few studies were conducted on corrosion under sustained load. In addition, the influence of corrosion on long-term bond behavior still needs more explanation. Therefore, the present experimental study is a part of a project dedicated to study the effect of corrosion on bond characteristics between reinforcement steel bar and surround concrete under sustained load. The target of this study is to provide bond stress levels limits that should not be exceeded in presence of corrosion, in order to prevent deterioration due to large creep. In this study the effect of corrosion on time dependent bond behavior was investigated experimentally, Reinforced concrete prism specimens were made of concrete with 0.60 water cement ratio (w/c) ratio and were provided with two separate reinforcement steel bars arranged along their longitudinal axis. One of the steel bars with shorter embedded length (4.0D,D: diameter of RB) was corroded electrolytically before performing pullout test. Based on bond strength under instantaneous pull out tests, bond stress levels as well as corrosion degree (5.5%) was adopted for the sustained load test. The results show that if bond stress level exceeds 62%, remarkable creep of bond takes place. Moreover, load history may have some effect on slip creep in presence of corrosion. 2. OUTLINE OF EXPERIMENT 2.1. MATERIALS AND CONCRETE MIX Ordinary Portland cement was used to make concrete of 60% water-cement ratio (W/C), which has been used widely. The concrete mix *1 Department of Social and Environmental Engineering, Hiroshima University, Member of JCI. *2 Department of Social and Environmental Engineering, Hiroshima University. *3 Department of Social and Environmental Engineering, Hiroshima University, Prof., Member of JCI. *4 Department of Social and Environmental Engineering, Hiroshima University, Dr.E., Member of JCI. 論文 コンクリート工学年次論文集，Vol.25，No.2，2003 -985-