Implementation of Conductive Concrete Overlay for Bridge Deck Deicing at Roca, Nebraska

Conductive concrete is a relatively new material technology developed to achieve high electrical conductivity and high mechanical strength. In research sponsored by Nebraska Department of Roads, a conductive concrete mix specifically for bridge deck deicing was developed. In this application, a conductive concrete overlay is cast on top of a bridge deck for deicing and anti-icing. This technology has been successfully implemented in a demonstration project at Roca, about 15 mi south of Lincoln, Nebraska. The Roca Spur Bridge has a 36-m (117-ft) long and 8.5- m (28-ft) wide conductive concrete inlay. Temperature sensors and a microprocessor-based controller system were installed to monitor and control the deicing operation of the inlay. The construction was completed and the bridge was opened to traffic in the spring of 2003. Data from the first deicing event showed that an average of 500 W/m2 (46 W/ft2) was generated by the conductive concrete to raise the slab temperature about 9°C (16°F) above the ambient temperature. The details of the construction and deicing operation of the conductive concrete inlay are presented

Bridge Deck Deicing

Concrete bridge decks are prone to ice accumulation. The use of road salts and chemicals for deicing is cost effective but causes damage to concrete and corrosion of reinforcing steel in concrete bridge decks. This problem is a major concern to transportation officials and public works due to rapid degradation of existing concrete pavements and bridge decks. The use of insulation materials for ice control and electric or thermal heating for deicing have been attempted and met limited success. Conductive concrete may be defined as a cementitious composite, which contains a certain amount of electronically conductive components to attain stable and relatively high electrical conductivity. When connected to a power source, heat is generated due to the electrical resistance in the cement admixture with metallic particles and steel fibers. Based on the results of a transient heat transfer analysis, a thin conductive concrete overlay on a bridge deck has the potential to become a cost effective deicing method. Small-scale slab heating experiments have shown that an average power of about 48 W/m2 was generated by the conductive concrete to raise the slab temperature from -1.1°C (30°F) to 15.6°C (60°F) in 30 minutes. This power level is consistent with the successful deicing applications using electrical heating cited in the literature. The work described in this paper is part of an on-going research project being conducted for Nebraska Department of Roads. Two large slabs are under construction for bridge deck deicing experiment in natural environment to monitor power consumption and deicing performance. The construction costs and experimental data will be used to evaluate the cost effectiveness of using a conductive concrete overlay for bridge deck deicing or anti-icing

Airfield Pavement Deicing with Conductive Concrete Overlay

Conductive concrete is a cementitious admixture containing a certain volumetric ratio of electrically conductive materials to attain high and stable electrical conductivity. Due to its electrical resistance, a thin overlay of conductive concrete can generate enough heat to prevent ice formation when energized by AC power. Under a research sponsored by Nebraska Department of Roads, Yehia and Tuan developed a mix specifically for concrete bridge deck deicing while meeting the ASTM and AASHTO strength specifications for overlay construction. An average thermal power of 591 W/m2 (55 W/ft2) with a heating rate of 0.56oC/min (1oF/min) was generated by a 1.2 m by 3.6 m (4 ft by 12 ft) and 8.9 cm (3.5 in.) thick conductive concrete test slab in snow storms. The average energy cost was about $0.8/m2 ($0.074/ft2) per snow storm. This technology is readily available for airfield pavement deicing application. The Phase I findings of this research have shown that conductive concrete overlay has the potential to become the most cost-effective concrete pavement deicing method. A Phase II project is underway, in which a 45.7 m (150 ft) long and 11 m (36 ft) wide bridge deck at Roca, Nebraska, will have conductive concrete overlay implemented. The construction is scheduled for summer 2002. In this paper, evaluations of conductive concrete mixes with steel shaving, carbon and graphite products, in addition to steel fibers, are discussed in detail. Also, the implementation of two conductive concrete sidewalks in Shelby, Ohio is presented

Heated Bridge Deck System and Materials and Method for Constructing the Same

Aheated bridge deck (20) uses electrodes (24,26) embedded within conductive concrete and connected to a power Source to remove Snow and ice accumulation. A cement-based mixture containing optimal amounts of conductive materials is molded into pre-formed slabs (22) placed atop the paved Surface of a bridge deck. Alternatively, the conductive concrete may be cast in place on top of an existing bridge deck. A control unit with temperature and moisture Sensors may be coupled to the heated bridge deck

Half-metallicity in EuN: A First-Principles Calculation

We report on the electronic and magnetic properties of the rock salt (RS) and cesium chloride (CsCl) phases of EuN. Our calculation was performed within the framework of the density functional theory (DFT), as implemented in the Wien2k package. We have used the generalized gradient approximation (GGA) for the exchange correlation potential and, in certain, cases the Local Spin Density (LSDA) approximation, with the Hubbard interaction taken into account.  Our calculation demonstrates the presence of an energy gap in both of the RS and CsCl structures when only spin-polarized calculation is used. However, taking the Hubbard potential into consideration, via the LSDA+U scheme, led to the disappearance of the energy gap, and hence to the absence of the half-metallic behavior in this system. Keywords: rare-earth nitrides; magnetic moment; DFT; DOS; half metallicity; spin density

End Zone Reinforcement for Pretensioned Concrete Girders

In this study, a literature review was conducted to establish the background of current specifications and to evaluate the applicability of various theories and methods for design of end zone reinforcement. Analytical methods reviewed in this paper include finite element analysis, strut-and-tie modeling, and the Gergely-Sozen equivalent beam method. Previous experimental work combined with work conducted as part of this study was used to correlate between various theoretical and experimental results. This paper illustrates that no single theoretical method adequately represents the complex behavior at the end of a pretensioned concrete member. A general semi-empirical design procedure is proposed here. It is based on theoretical behavior and experimental observation. Standard reinforcement details are given. The proposed procedure could result in significant reduction in the amount of reinforcement while maintaining acceptable crack control at the member end. Application of the proposed procedure to highly pretensioned bridge girders is demonstrated

Use of Foley\u27s catheter balloon tamponade to control placental site bleeding resulting from major placenta previa during cesarean section

Aim: To evaluate the effect of 2-way Foley\u27s catheter balloon tamponade on controlling immediate postpartum hemorrhage (PPH) in cases of major placenta previa during cesarean section (CS). Methods: We evaluated women with placenta previa from May to November 2015. Women with immediate PPH during CS due to major placenta previa were managed by 2-way Foley\u27s catheter balloon tamponade when medical treatment failed, and before any surgical intervention. Results: Twenty patients, had major placenta previa, were delivered by elective CS and complicated by immediate PPH. Three placenta accreta patients (15%) underwent hysterectomy, 17 (85%) were managed by the 2-way Foley\u27s catheter balloon tamponade. In two patients, Foley\u27s catheter balloon failed to control bleeding and hysterectomy was done immediately. However, Foley\u27s catheter balloon successfully treated the remaining 15 patients. The median bleeding during the operation was 1522.5 (± 619.29) ml. None of them presented complications related to this procedure or required any further invasive surgery. Conclusion: The 2-way Foley\u27s catheter tamponade could be an option to control immediate postpartum hemorrhage resulting from major placenta previa during the cesarean section. This method is simple, cheap, nearly non-invasive and should be considered to reduce the risk of peripartum hysterectomy

Polycystic kidney disease with unilateral ventriculomegaly: a case report

Polycystic Kidney Disease (PKD) is an autosomal recessive disease with an incidence of about 1 in 30 000 births. It characterized by multiple cysts which filled by fluid that can ultimately impede kidney function leading to degeneration of renal tissue and renal failure. Oligo or anhydramnios is frequently present but not invariably so, suggesting that some degree of renal function is retained in some PKD cases. We present a 30 year old woman, gravida 5, para 4, at 22 weeks of gestation with ultrasound findings of autosomal recessive PKD, unilateral ventriculomegaly and marked oligohydramnios. Ventriculomegaly is a brain condition that occurs when the width of the atrium of the lateral ventricle is greater than 10 mm and occurs in 0.3-1.5 births per 1000. The association between autosomal recessive PKD and unilateral ventriculomegaly is not well understood and needs further evaluation