Influence of grouting conditions on deterioration of post-tensioned prestressed concrete beams (original) (raw)
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コンクリート工学年次論文集, 2005
An experimental program was carried out to clarify the effect of chloride-induced corrosion on post-tensioned concrete (PC) beams under different grout conditions using accelerated corrosion testing method (ACTM). The influence of different quantities of grout in parabolic segment of sheath on prestressing tendon corrosion was clarified. The radial pressure surrounding the tendon during corrosion process was also investigated. After a period of accelerated corrosion, the mechanical behavior of the deteriorated PC beams was clarified through loading test.
Advances in Structural Engineering, 2020
Prestressed concrete beams are widely used in construction, while they may be attacked by the corrosion medium during the service. Past research works show that coupled effect of high stress and corrosion can significantly deteriorate the performance of prestressed concrete structures. This article presents an experimental investigation on long-term behavior of prestressed concrete beams under the coupled effect of sustained load and corrosion. During the accelerated corrosion process, six prestressed concrete beams were subjected to different levels of sustained loads, and time-dependent prestress loss and concrete stains were recorded and analyzed. It is observed that the local corrosion (i.e. pitting corrosion) of the steel strands was significantly affected by the sustained load level, and the coupled effect led to more serious damage on the beams than individual sustained load or corrosion. Bending loads were finally applied to investigate the influence of corrosion on flexural...
Behavior of corroded bonded fully prestressed and conventional concrete beams
HBRC Journal, 2016
Prestressed concrete is widely used in the construction buildings. And corrosion of steel is one of the most important and prevalent mechanisms of deterioration for concrete structures. Consequently the capacity of post-tension elements decreased after exposure to corrosion. This study presents results of the experimental investigation of the performance/behavior of bonded fully prestressed and conventional concrete beams, with 40 MPa compressive strength exposed to corrosion. The experimental program of this study consisted of three fully prestressed and two conventional concrete beams with overall dimensions equal to 150 Â 400 Â 4500 mm. The variables were considered in terms of corrosion exposure effect, prestressed level, and corrosion location effect for fully prestressed beams. Mode of failure, cracking width/distribution, ultimate load and the corresponding deflection of each beam were recorded. The results showed that the fully prestressed beam in comparison with conventional beam was considered to be even more resistance to corrosion because it was perceived to be crack-free as a result of prestressing. Also the mention deterioration incident in fully prestressed beams fully corrosion exposure level unnoticed that deterioration incident in partially corrosion exposure level. The most of deterioration incident in fully prestressed beam acts on compression of non-prestressed steel reinforcement. Because the bonded tendons are less likely to corrode. Cement grout/duct is a barrier to moisture and chloride penetration,
1170 Experimental Investigation on Chloride-Induced Corrosion in Post-Tensioned Concrete Beams
コンクリート工学年次論文集, 2004
An experimental program was carried out to investigate the behavior of post-tensioned concrete (hereafter PC) beams under severe condition of environment. To simulate deterioration of PC beams in a short period, an accelerated corrosion testing (hereafter ACT) method was adopted in this study. A series of accelerated corrosion tests were carried out to evaluate the influence of various parameters on corrosion of sheath and prestressing steel. Further, loading tests were conducted to investigate the mechanical behavior of PC beams deteriorated by corrosion. Results of experiments show that corrosion of sheath and prestressing steel has significant influence on load carrying capacity of PC beams.
Proceedings of CORROSION AND PREVENTION, 2009
In 2002, the 45 year old Sorell Causeway Bridge inTasmania’s south east was demolished due to fears surrounding the serviceability of the prestressed concrete beams, in relation to the corrosion of the post-tensioning strands. Attempts were madeto determine the extent and severity of the corrosion prior to its demolition by employing a number of conventional non-destructive and diagnostic techniques, yet a firm conclusion could not be reached regarding the structure’s condition. To further investigate the degree of correlation between these conventional assessment techniques and the physical condition of the embedded steel in relation to corrosion risk guidelines recommended in the literature, a number of beams of varying condition were salvaged from the bridge demolition and subjected to further detailed investigations. The current paper focuses on the half-cell potential and chloride profile results obtained for two such beams in good and poor condition relating to the reinforcing and prestressing steel condition. In summary, the comparison of results yielded inconsistencies with the literature guidelines. Survey areas showing highly negative potentials and elevated chloride concentrations did not necessarily indicate corrosion activity or severity. In contrast, instances of severe corrosion were found on both reinforcing and prestressing steel where literature guidelines for these tests recommend that the risk of corrosion is low.
Corrosion of Post-Tensioned Tendons With Deficient Grout
2016
Severe corrosion recently documented in Florida posttensioned bridges were related to grout segregation that created deficient grout with characteristics of having low chloride content, high sulfate concentration, high pore water pH, and high moisture content. The role of elevated sulfate concentrations in the development of steel corrosion in deficient grout has not been elucidated. As first approach to determine the corrosion mechanism of steel strand in deficient grout, the objective of the research, described here, was to evaluate the role of sulfate ions on the corrosion of steel in alkaline solutions. Steel coupons were exposed to two different alkaline solutions (SPS) simulating pore solutions with pH 12.6 (SPS1) or 13.3 (SPS2) with varying sodium sulfate levels (early fixed content and later increments). Electrochemical experiments included the steady-state condition and potentiodynamic polarization tests. Solution pH was found as an important parameter in the corrosion development of steel in sulfate SPS solutions. In the highly SPS2 solution (pH 13), sulfate ions did not impair passive film growth or stability. In the moderate SPS1 solution (pH 12.6), early fixed sulfate presence could be aggressive by impairing passive film development; however, even high levels of later increments of sulfates cannot depassivate steel. The instability of the passive film in alkaline sulfate solutions resulted in pitting corrosion of steel.
Corrosion Damage for Prestressed Concrete Bridge Girders
Abstract: The deterioration process includes three stages: diffusion of chlorides, corrosion of steel strands, and cracking/spalling of concrete. The time to initiation of corrosion depends on concrete cover depth, quality of protective coating (if any), and diffusion coefficient. Occurrence of cracks can be very important, as it facilitates the penetration of aggressive chemicals (salt). The diffusion coefficient can be significantly larger for cracked sections (areas) than for intact concrete. For the cracked section under service load, it is taken as an average value with regard to time and area. A 2-D and 3-D models are developed for prediction of the chloride concentration at the surface of reinforcement. The probability of the initiation of corrosion is calculated for representative design cases. Recommendations are formulated for design of prestressed concrete bridge girders, including allowable tensile stress and cover depth for various conditions (i.e. level of exposure to ...