Probabilistic Estimation of Corrosion Propagation Period for Prestressed Concrete Structures Exposed to Chlorides

The overall service life of concrete structures can be divided into corrosion initiation and corrosion propagation phases. The durations of these two phases depend on the chloride threshold (Clth) and corrosion rate (icorr), respectively, of the embedded steel reinforcement. Quantitative information on Clth and icorr of conventional steel reinforcement are available in literature. Now‑a‑days, the use of prestressed concrete elements are rapidly increasing and there is a dire need for estimating their service life. Quantitative information on the Clth and icorr of prestressing steel are required for this estimation. However, very limited quantitative information is available on these parameters. As such, the current practice is to assume that both conventional and prestressing steels have similar Clth and icorr – which might result in unrealistic estimations. This paper provides data on icorr obtained from a 9-month long experimental program. The icorr data was obtained using linear polarization resistance (LPR) tests on prestressing wire embedded in mortar. 10 specimens (made using the center king-wires obtained from 7-wire strands) were cast, cured, and subjected to a cyclic wet-dry exposure using 3.5 % sodium chloride solution. It is observed that the average value of icorr of prestressing steel exposed to chloride‑contaminated mortar is around 5.8 mA/cm2. The paper also provides the probabilistic estimations on corrosion propagation period, tp (defined as the time to crack after corrosion initiation) by substituting the measured icorr data into two models from literature [i.e., Morinaga (1990) and Wang and Zhao (1993)]. It is found that the estimated average tp for prestressed concrete systems are 5.4 and 9.7 years with large scatter. This paper also provides probabilistic estimations on tp for the prestressed concrete systems with 50, 65, and 80 mm cover depths

Tunneling and Non-Universality in Continuum Percolation Systems

The values obtained experimentally for the conductivity critical exponent in numerous percolation systems, in which the interparticle conduction is by tunnelling, were found to be in the range of $t_0$ and about $t_0+10$, where $t_0$ is the universal conductivity exponent. These latter values are however considerably smaller than those predicted by the available ``one dimensional"-like theory of tunneling-percolation. In this letter we show that this long-standing discrepancy can be resolved by considering the more realistic "three dimensional" model and the limited proximity to the percolation threshold in all the many available experimental studiesComment: 4 pages, 2 figure

Vanishing largest Lyapunov exponent and Tsallis entropy

We present a geometric argument that explains why some systems having vanishing largest Lyapunov exponent have underlying dynamics aspects of which can be effectively described by the Tsallis entropy. We rely on a comparison of the generalised additivity of the Tsallis entropy versus the ordinary additivity of the BGS entropy. We translate this comparison in metric terms by using an effective hyperbolic metric on the configuration/phase space for the Tsallis entropy versus the Euclidean one in the case of the BGS entropy. Solving the Jacobi equation for such hyperbolic metrics effectively sets the largest Lyapunov exponent computed with respect to the corresponding Euclidean metric to zero. This conclusion is in agreement with all currently known results about systems that have a simple asymptotic behaviour and are described by the Tsallis entropy.Comment: 15 pages, No figures. LaTex2e. Some overlap with arXiv:1104.4869 Additional references and clarifications in this version. To be published in QScience Connec

Quaternary Geology and Geomorphology of Terna River Basin in West Central India

Im vorgelegten Artikel werden die Morphostratigraphie, Lithostratigraphie sowie die Sedimentstrukturen des Terna Beckens in der Deccan Basaltic Province (DBP) im westlichen Zentralindien vorgestellt. Die Quartärablagerungen können in drei große Einheiten unterteilt werden (i) dunkelgraue Schluffablagerungen – Spätes Holozän, (ii) hellgraue Schluffablagerungen – Frühes Holozän, (iii) dunkelgrau-braune Schluffablagerungen – Spätpleistozän mit altquartären alluvialen Absätzen mit oberpleistozänen Altern. Die feinen tonig-schluffigen Ablagerungen im Unterlauf des Flusses deuten auf ruhige Ablagerungsbedingungen und einen sinusartigen Abfluss hin. Der Fluss zeigt Tendenzen zu abschwemmungsbedingten Gerinneverlagerungen, die wiederum durch vorhandene Bruchlinien gesteuert wurden. Entlang des Terna-Flusses konnten weiterhin Paläouferrücken in Form von 4–5 m hohen Rücken nachgewiesen werden, hier vor allem im Bereich der OrtschaftenTer, Killari, Sastur, Dhuta und Makni. Einige nachgewiesene Bruchlinien treten vor allem in NE-SE, NW-SE, E-W und WNW-ESE-Richtung auf und bestimmen die Struktur des Grundgebirges im Untersuchungsgebiet. Die TSI-Werte (Topographic Sinousity Index) verdeutlichen einen Erosionswechsel im Untersuchungsgebiet mit einer Verstärkung des topographischen Einflusses auf die Ausformung der Abflussbahnen. Die im Profil sichtbare Geländekante zeugt weiterhin von einer tektonischen Hebung des Gebietes im Quartär. Radiokohlenstoffdatierungen, die an einigen Holzkohlefragmenten durchgeführt wurden, die aus gefalteten Ablagerungen entnommen wurden, deuten darauf hin, dass eine seismische Aktivität in der Zeitspanne zwischen 120–1671 n. Chr. stattgefunden haben kann.researc

Residual Service Life Estimation and its Importance for Pretensioned Concrete (PTC) Bridges in Coastal Cities

Many pre-tensioned concrete (PTC) bridges are experiencing premature chloride-induced corrosion. Hence, it is crucial to estimate their residual service life and update it with newer data on a periodic basis - to plan for corrosionpreventionorcontrolmeasuresandensuresafetyofexistingbridges.Criticalchloridethreshold(Cl th) is one of the parameters necessary to estimate the corrosion initiation period. However, quantitative estimates on Clth for prestressing (PS) steel are not well-reported in literature. This paper presents experimental data on the Clth of PS steel, the chloride diffusion coefficient (Dcl), and surface chloride concentration (Cs) of concrete samples obtained from a PTC bridge girder in a coastal city in India. For estimation of Clth, 5 specimens were cast with PS steel wires embedded in ordinary Portland cement (OPC) mortar containing 30% of Class F fly ash (similar composition as that of the bridge girder). They were cured for 28 days and then subjected to cyclic wet-dry exposure using simulated concrete pore solution containing 3.5%sodiumchloride.(Linear polarization resistance (LPR) tests were performed at the end of each exposure cycle, corrosion initiation was detected using statistical methods, and Clth was determined). Using the determined Clth and Dcl, and other relevant parameters, the cumulative distribution functions of time to corrosion initiation was developed. It was found that the average time to corrosion initiation was about 40 years, whereas the structure was designed for 120 years. Also, it was estimated that the corrosion products will accumulate within the interstitial space between the 7 wires in a strand and will not flow through the concrete cover and reach the concrete surface (showing rust stains) until about 5% of strand is corroded (about 10 years). This indicates a dire need for regular data collection, updating the residual life estimates, which will help in developing corrosion prevention strategies for PTC structures

Self consistent determination of plasmonic resonances in ternary nanocomposites

We have developed a self consistent technique to predict the behavior of plasmon resonances in multi-component systems as a function of wavelength. This approach, based on the tight lower bounds of the Bergman-Milton formulation, is able to predict experimental optical data, including the positions, shifts and shapes of plasmonic peaks in ternary nanocomposites without using any ftting parameters. Our approach is based on viewing the mixing of 3 components as the mixing of 2 binary mixtures, each in the same host. We obtained excellent predictions of the experimental optical behavior for mixtures of Ag:Cu:SiO2 and alloys of Au-Cu:SiO2 and Ag-Au:H2 O, suggesting that the essential physics of plasmonic behavior is captured by this approach.Comment: 7 pages and 4 figure

A qualitative test for the determination of isoniazid acetylator phenotype

A qualitative test procedure for phenotyping isoniazid acetylators is described. It is based on a colour reaction which depends on the free sulphadimidine content in the total urine excreted over any one-hour period between 21 and 26 hours following a dose of sulphadimidine 1.0 or 1.5 g. depending on body-weight. The test correctly classified 96 per cent of 109 slow and 96 per cent of 68 rapid inactivators. Storage of urine samples at room-temperature up to 14 days did not affect the accuracy of the results

Enhancing Fodder Oat (\u3cem\u3eAvena sativa\u3c/em\u3e) Production in Problem Soils Using Phosphate Solubilizing Fungi Isolated from Acid and Salt Affected Soils of India

Tropical and subtropical soils are predominantly acidic, and often extremely phosphorus-deficient with high phosphorus sorption (fixation) capacities. Phosphorus (P) is one of the major essential macronutrients for plants, present at levels of 400–1200 mg/kg of soil. One of the drawbacks of fertilization is that only a fraction of the P added is eventually assimilated by plants, due to high reactivity of soluble phosphate with other elements the rest becomes unavailable to plants by forming complexes with either, Al, Fe, Ca or Mn depending on soil type (Rodríguez and Fraga, 1999). Even though some soils may have high levels of total P, they can still be P-deficient due to low levels of soluble phosphate available to plants. Available P concentrations for maximum pasture production are estimated to be between 20 and 50 µg/g. Because of the spiraling cost of phosphatic fertilizers coupled with low recovery (10- 30%) of phosphorous applied in the field, the developing tropical countries are attempting to utilize their indigenous reactive ground phosphate rock as a cheap alternative (Sabannavar and Lakshman, 2009). Many soil bacteria, Pseudomonas, Bacillus, Burkholderia, Arthrobacter, Alcaligenes, Serratia, Enterobacter, Acinetobacter and Flavobacterium and fungi especially Aspergillus, Penicillium, Trichoderma have the ability to solubilize elemental phosphate (Pi) and make it available to plants. They are used as biofertilizers for supplying the P requirement of the plants. However, scanty information is available on the occurrence of PSMicroorganisms (PSMs) in acid and salt affected soils. The present investigation was aimed to isolate PSMs from acid and salt affected soils that could survive and solubilize insoluble phosphate efficiently in the presence of higher salt concentration and acidic medium so as to obtain efficient isolates for application as a potential biofertilizer in acid and saline or problematic soils