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Bridge construction utilizing post-tensioned (PT) tendon systems have become increasingly popular. 1-2 PT construction allows engineers greater options for the design of highway bridges and provides efficient structures with advantages in construction, economy, and serviceability. In bonded post stresses to the reinfotensioned systems, the introduction of rced concrete element is made through tensioned highstrength steel strand that are anchored and encapsulated in a cementitious grout within a tendon.3-4 The hardened grout allows development of the stress along the length of the tendon and also provides corrosion protection by the presence of the alkaline pore water to passivate the steel strand and by creating a barrier from external contaminants.
PT construction provides efficient bridge with advantages in construction, economy, and serviceability. In bonded posttensioned systems, the introduction of stresses to the reinforced concrete element is made through tensioned highstrength steel strand t hat are encapsulated in a cementitious grout. The hardened grout provides corrosion protection by the presence of the alkaline pore water to passivate the steel strand and by creating a barrier from external contaminants. However, there have been documente d cases of strand corrosion relating to deficiencies of the grout materials. Segregation of thixotropic grouts allowed for the development of chemically deficient grouts (characterized as having high sulfate concentrations) in verticallydeviated tendons in part attributed to an upward moisture and ion mobility. The Schupak pressure bleed test and vertically cast grout specimens was utilized to assess the performance of grout materials subjected to adverse construction practices including prehydration and a ddition of excess mix water. Results indicated that there is limited availability of sulfate ions upon initial grout casting but would still be able to accumulate via transport of the free water. Greater pressures and vertical deviations allowed for greate r accumulation. moisture transport and sulfate Keywords, PT tendons, grout, segregation, sulfate, bleed INTRODUCTION Bridge construction utilizing post increasingly popular. 12tensioned (PT) tendon systems have become PT construction allows engineers greater options for the design of highway bridges and provides efficient structures with advantages in construction, economy, and serviceability.
F22 is a low alloy steel that typically contains 12% Carbon, 2.25% Chromium, and 1.0% Molybdenum1. This steel has been widely used in oil production systems, especially in well head design and construction. As a low alloy steel, F22 can be corroded by oilfield chemicals under certain circumstances. For example, it was observed in the Gulf of Mexico that typical scale inhibitor chemistries caused severe corrosion on F22.
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During the last decades, low alloyed steels with improved resistance to Sulfide Stress Cracking (SSC) have been developed for covering specific applications as heavy wall casings1 or expandable tubings2 or for reaching higher mechanical properties, such as 125 ksi Specified Minimum Yield Strength (SMYS) materials.3-6 For the latter, relevant sour environments for developed grades are mild, meaning that all sour applications cannot be covered while a strong interest exists for O&G operators to use high strength materials when designing wells. Consequently, there is an incentive to push the limits of use of high strength sour service steels by enhancing their resistance to SSC. Several recommendations were already published when designing high strength sour service grades: hardness level shall be limited as much as possible and be preferentially below 22 HRC7, microstructure shall present a minimum required amount of martensite8 which is well known to be ideal for combining high mechanical properties and high resistance to hydrogen. Besides, many authors highlighted some other influencing parameters related to the material or the process.
Mineral scales frequently occur in tanks, pipelines, cooling and heating system, production wells ofoil and gas, external and internal membrane, and other equipment during industrial processes,causing the reduction of process efficacy and millions of dollars on dealing with the scale issues. Asoil and gas are produced increasingly in more unconventional reservoirs, such as deeper and tighterzones, with new technologies, more challenges are encountered to mitigate scale problems.