Concrete structure is a construction material with durability and cost-benefit, however the corrosion in embedded steel causes a critical problem in structural safety. This paper presents an evaluation of chloride resistance and pull-off performance with various corrosion level. For the work, OPC(Ordinary Portland Cement) concrete and GGBFS(Ground Granulated Blast Furnace Slag) concrete are prepared with normal steel. Artificially notch induced FRP Hybrid Bar is also prepared and embedded in OPC concrete and accelerated corrosion test is performed. Through the test, FRP Hybrid Bar with notch is evaluated to have insignificant effect on pull-off capacity when corroded steel shows only 21% level of pull-off capacity. Furthermore GGBFS concrete with normal steel shows over 70% level of pull-off capacity due to reduced corrosion currency.

POST-TENSIONING GROUT PROBLEMS Bonded post-tensioned structures are at increased risk of corrosion and failure of the tendons when there are defects in the installed grout. The most common grout problems (defects) include: • Voids: Voids are common at high points of tendon ducts as a result of grout bleeding and inadequate grouting. Standard cement/water grout has typically produced grout with 3 to 5% bleed. • Chloride contaminated grout: Chloride contamination may result from the use of chloride contaminated grout or mixing water or the long-term exposure of the structure to marine environments or de-icing salts. • Soft grout: Soft grout may be created if excessive water is added during grout mixing, and wick induced bleeding causes localized grout with high water-cement ratio. THE SOLUTION The Post-Tech PTI Impregnation system has been developed to mitigate corrosion caused by these problems. The system utilizes the interstitial spaces between the wires of each strand in a multi-strand tendon to deliver (transfer) a unique corrosion inhibiting, impregnation material along the length of the cable. The impregnation material seeps between the wires of the strands to impregnate the surrounding grout or concrete. The impregnation material is designed to form a corrosion-resistant film on any exposed steel surfaces such as steel strands which are exposed in grout voids, and to make the grout more corrosion and moisture resistant. Laboratory Confirmation Laboratory confirmation was completed on tendon specimens provided by one DOT and grouted “lollipop” samples. The tendon specimens provided to Vector were sections of external tendons which had been removed from an existing bridge. Lolipop samples comprised a single strand section which was centrally grouted in a cylindrical block of prepackaged PT grout. Laboratory testing confirmed the ability of the impregnation material to travel along the length of the specimen, to soak into the grout surroundingthe strands and to pass from strand to strand across the cross-section of a grouted tendon. Accelerated laboratory testing also confirmed the ability of the impregnation process to reduce corrosion by over 90%. Field Demonstration and case study The demonstration project was completed on external tendons in a box girder bridge in Jacksonville, FL (I-95 / I-295 Interchange). The demonstration project verified the capability of impregnating the full length of 256’ and 205’ grouted tendons from end anchorage locations, the capability of impregnating up to 100’ in each direction from a mid-point location, and the capability of the impregnation material to penetrate the grout adjacent to the strand. FDOT has implemented PTI Impregnation on the tendons of I-4 Connector in which soft grout was found. All selected tendons were successfully impregnated. Free water/moisture was pushed out of the tendons during the impregnating process. CONCLUSIONS Laboratory testing confirmed the ability of the impregnation material to travel along the length of the specimen, to soak into the grout surrounding a strand and to reduce corrosion by over 90% when exposed in an accelerated corrosion cell. Field demonstration at the I-95/295 Interchange in Jacksonville, Florida and Implementation on I-4 Connector in Tampa, Florida has demonstrated the following: • All strands of 256’ long grouted tendons can be impregnated full-length from an end anchorage location, • Impregnation material can flow up to 100’ in each direction from a mid-point location,. • Impregnation material can penetrate grout adjacent to a grouted strand, and • Free water/moisture can be pushed out of the tendons during the impregnation process.

The combined effect of carbonation and chloride ingress in concrete is studied in this paper. A coupled simulation of the transports of carbon dioxide, chloride ions, heat and moisture is carried out. Several sets of experimental data were compared with the prediction by the numerical model developed in this paper, for its verification.

Recently, Advanced water treatment facilities with Ozone are being introduced domestically. However, waterproofing/corrosion prevention construction method of concrete structure for existing advanced water treatment makes waterproofing/corrosion prevention materials and concrete deteriorated because of strong oxidation of ozone. Therefore, in this study, As a one of studies for improving durability of advanced water treatment plant applied by metal spray system, electrochemical corrosion protection of metal spraying film according to surface treatment in pH 5 acid solution which is similar to pH concentration in real ozone treatment was evaluated..

In this study, Corrosion behavior in mortar was observed by the passage of time by using EIS method. As a result of EIS experiment, equivalent circuit and changes of Impedance parameter could be observed. In addition, it was confirmed that impedance of rebar in mortar and corrosion rate according to the amount of NaCl were different.

Steel is a common structural material that is used for bridges, buildings, railroad tracks, wind towers, offshore platforms, and many other applications. Steel naturally corrodes in different atmospheric environments, which results in costs for corrosion protection, prevention and maintenance. The corrosion on steel elements is identified by optical examination, which does not provide information on the material characteristics. Studies have shown that Raman spectroscopy can identify the corrosion products of steel and differentiate between iron oxides and hydroxides. The purpose of this experiment is to validate the use of Raman spectroscopy in accurately identifying corrosion material on steel without a protective coating.

Development of appropriate construction technology at frozen soil environments for developing resources is essential. However, cathodic protection technology using monitoring at frozen soil environments is lack. In this study, we want to build a real-time monitoring system at frozen soil environments through corrosion monitoring using type of gavanic metal

본 실험 논문은 초단유리섬유(milled glass fibers)가 혼입된 PSC용 그라우트 몰탈의 강재부식성능을 평가하였다. 초단유리섬유를 함유한 배합이 PSC 그라우트 몰탈로서 소요성능을 만족시키는지를 확인하기 위하여 유하시간, 블리딩 및 압축강도를 측정하였다. 초단유리 섬유를 함유한 몰탈의 부식저항 성능은 염소이온 확산시험, 몰탈 흡수시험과 표면전기저항 측정 결과에 근거하여 수행되었다. 시험결과, 초단 유리가 혼입된 모든 배합은 OPC만 사용된 배합에 비하여 그라우트의 부식저항성능을 개선시키는 것으로 확인되었다. 다만, 초단유리섬유를 사용함으로서 유하시간은 단축되지만 블리딩이 발생하여 소요성능을 만족하지 못하는 것으로 확인되었다. 그러므로 PSC 그라우트에 적합한 초단유리섬유배합이 되기 위해서는 물-바인더비의 조정이 필요한 것으로 판단된다.

A cartridge type sensor head was fabricated to detect the level of corrosion in steel cables with consistent or varying cross sections by assessing the LMA (Loss of Metallic Area) damage. Two coil sensor cartridges were made to cater to cables with up to 70mm and 150mm. The developed system was verified through lab experiment using a tapered steel cable specimen, and through a field test conducted in cable bridge. The result showed that the developed system is capable of assessing a cable with varying cross section.

The purpose of this study is to evaluate the impact on flexural strength and compressive strength of the concrete, the mixing rate of the amorphous fibers.

Many researchers have defined critical chloride content as a specific value. The studies reporting critical threshold chloride content have involved the experimental measurement of the average amount of the total chloride content. The studies have tried to define the critical chloride content within the scope of their experimental concrete mix proportion at arbitrary time. However, there is no agreement on its value. The purpose of this study is to explore the combined effect of oxygen and chloride on reinforcement corrosion. In the experimental recipe, water soluble oxygen is taken into account to define the critical chloride content. Corrosion current density of reinforcement was measured by linear polarization resistance method.

This study, depending on the concrete mix material by performing the test on the basis of the wet and dry condition and freeze-thaw, and to elucidate the difference in the corrosion initiation time of there steel, in both environments, it is an object of correlation coefficient derived through the results of the accelerated corrosion test in a laboratory corrosion period of the structure of the marine environment.

The tap water is generally known to be corrosive in the pH range at 6.5 ~ 7.5. And the degree of corrosion varies depending on the types of raw water such as river surface water or lake water of the dam. Although several corrosion index represents the corrosivity of tap water, the typical corrosion indexes such as Langelier saturation index (LI) and calcium carbonate precipitation potential (CCPP) were calculated to monitoring the corrosive water quality about raw and tap water in water distribution system. To control the corrosive water quality, the correlation between corrosion index and water quality factors were examined. In this study, corrosion index (LI, CCPP) and the pH was found to be most highly correlated.

In the paper, newly invented FRP Hybrid Bar and normal steel are embedded in RC beam member, and ICM(Impressed Current Method) is adopted for corrosion acceleration. Corrosion amount level of 4.9∼7.8% are measured in normal RC member and the related reduction of flexural capacity is measured to –25.4∼-50.8%. But, durability evaluation through long-term submerged condition is required for actual utilization.

The volume expansion of corroded steel reinforcement produces tensile stress on the surrounding concrete, which causes splitting cracking of concrete cover, and deteriorates the service ability and durability of reinforced concrete(RC) members. In addition, since the steel corrosion induces bond strength degradation between steel bar and concrete, the structural performance of RC members can be deteriorated significantly. In this study, the theoretical study was performed to probe the mechanism of the bond strength reduction due to steel corrosion. The bond strength between corroded steel bar and concrete was calculated by mathematically formulating the expansion pressure of corroded steel reinforcement. The proposed model was verified by comparing with the existing test results, and it showed that the proposed model estimate the bond strength reduction of corroded RC elements very closely.

Existing nondestructive test methods used to measure reinforcement corrosion is based on qualitative measurement of corrosion, and it has many difficulties of use because many equipment and measurement stages are required for application at actual sites. Accordingly, this study was conducted to estimate reinforcement corrosion of concrete structures using infrared thermography method as a method of measuring reinforcement corrosion in concrete. As for the specimen was to measure reinforcement corrosion, D13 reinforcement with size of 200×150×180mm was buried at length of 250mm for covering depth of 20mm and 40mm. Accelerated reinforcement corrosion test was carried out after placement of concrete. As a result of measuring reinforcement corrosion using infrared thermography method, temperature difference of 1~3°C was shown depending on the corrosion stage. There was a correlation in which temperature decreased according to chloride content. Infrared thermography method was confirmed as a useful method for measurement of reinforcement corrosion inside concrete.

Durability and structural safety of steel structure are severely affected by corrosion caused by deicer material as well as by airborne chlorides in the marine environment. In this study, based on analysis of current status it is suggested that deterioration and durability reduction by the environmental factor such as chlorides should be more reasonably taken into consideration for the accurate inspection and condition evaluation of steel structures.