bluuebunny/crossref_metadata_2025 huggingface dataset:
Interest of using a model combining carbonation/chloride ingress and depassivation to better anticipate the rehabilitation of concrete structures
Authors: Schmitt Lucie , Mai-Nhu Jonathan , Duprat Frédéric , De Larrard Thomas , Rougeau Patrick
Published: October 2018

Mastering and optimizing the durability of concrete structures and also the rehabilitation of concrete structures is a major challenge for all actors of the concrete construction field. An experimental program is conducted to get a complete characterization of the mechanical, chemical and physical properties of four concretes and their performances towards the main aggressive environment for the reinforcement corrosion. The evaluated durability properties are chloride migration, porosity, water absorption and carbonation. Moreover, for each concrete, some reinforced specimens are manufactured to measure the electrochemical properties of the reinforcement such as potential. The project achievements are used to optimize and improve the durability model SDReaM-crete developed by Cerib and LMDC. This model can simulate the migration of chlorides, the combination of this migration with the mechanism of carbonation and the corrosion of reinforcing bars according to wetting-drying cycles. Finally, the present work aims to optimize the sizing of the cover thickness for new structures and to facilitate the lifespan prediction for existing structures. This paper describes the model SDReaM-crete and its recent improvements. Some experimental results and some interpretations as well as simulations made with SDReaM-crete are also presented.
Perpendicular-to-crack chloride ingress in cracked and autonomously healed concrete
Authors: Van Belleghem Bjorn , Van den Heede Philip , Van Tittelboom Kim , De Belie Nele
Published: October 2018

Cracks in reinforced concrete structures exposed to a marine environment or de-icing salts can cause major durability issues due do accelerated ingress of chloride ions. In this study, the influence of autonomous crack healing by means of encapsulated polyurethane on the chloride ingress perpendicular to cracks was evaluated. This was done quantitatively by determining perpendicular-to-crack chloride profiles by means of profile grinding followed by potentiometric titration and qualitatively through visualization of the chloride penetration front by means of the AgNO3 spray method. The resulting chloride profiles showed that the healing mechanism was able to reduce the chloride concentrations in the direct vicinity of the crack to a large extent and to reduce the perpendicular-to-crack chloride penetration, especially further away from the exposed surface. Visualization of the chloride penetration front showed some variation in crack healing. For some healed samples almost no additional chloride ingress was found compared to uncracked samples, others showed a slightly enhanced ingress at the crack location but less perpendicular-to-crack chloride penetration compared to untreated cracked samples. Generally, the reduced amount of chlorides present in the concrete matrix due to crack healing will enhance the durability and service life of concrete structures.
Investigation on the transport properties of chlorides in concrete II Numerical simulation
Authors: Ye TIAN , Xianyu JIN , Nanguo JIN
Published: October 2018

The chloride ions diffusion in concrete is an important problem inducing the corrosion of reinforcement under marine environment. Based on a parallel transmission model, the diffusion coefficient of chloride ions in ITZ was determined. Thereafter, the measured parameters of ITZ were integrated into a numerical model to simulate the chloride ions diffusion and the reliability of the model was verified by comparing the numerical simulation with the surface scanning results collected from the electron microprobe. The test results show that if the concrete is taken as a threephase composites, the numerical model can reflect the real transmission process of chloride ion more accurately.
Leaching, carbonation and chloride ingress in reinforced alkali-activated fly ash mortars
Authors: Gluth Gregor J. G. , Hlaváček Petr , Reinemann Steffi , Ebell Gino , Mietz Jürgen
Published: October 2018

Alkali-activated fly ash mortars were studied with regard to durability-relevant transport coefficients and the electrochemical behaviour of embedded carbon steel bars on exposure of the mortars to leaching, carbonation and chloride penetration environments. The transport coefficients differed considerably between different formulations, being lowest for a mortar with BFS addition, but still acceptable for one of the purely fly ash-based mortars. Leaching over a period of ~300 days in de-ionized water did not lead to observable corrosion of the embedded steel, as shown by the electrochemical data and visual inspection of the steel. Exposure to 100 % CO2 atmosphere caused steel depassivation within approx. two weeks; in addition, indications of a deterioration of the mortar were observed. The results are discussed in the context of the different reaction products expected in highand low-Ca alkali-activated binders, and the alterations caused by leaching and carbonation.
Effectiveness of Silane to Mitigate Alkali-Silica Reaction in a Historical Bridge
Authors: Schindler Anton , Johnson Darren , Warnock Robert , Barnes Robert
Published: October 2018

Alkali-silica reaction (ASR) is a detrimental reaction in concrete that may lead to severe expansion and cracking in structures. The Bibb Graves Bridge is a reinforced concrete bridge that was constructed in 1931, and is located in Wetumpka, Alabama, U.S.A. Both arches of Span 5 have severe cracking and surface deposits caused by ASR. In order to mitigate ASR, a silane-based surface sealer was applied to Spans 4 and 5 of this bridge. The goal of this mitigation procedure was to decrease the internal relative humidity of the ASR-affected concrete to less than 80 percent so that continued ASR-related expansions do not occur. After the execution of the mitigation procedure, the internal relative humidity, concrete expansion, and new crack development in the bridge were monitored for 35 months to evaluate the effectiveness of the mitigation procedure. Analysis of these data revealed few signs of decreasing relative humidity or decreased expansion rates in the ASR-affected concrete. It is concluded that the silane sealer was ineffective and alternative mitigation options should be considered.
Galvanic cathodic protection of corroded reinforced concrete structures
Authors: Whitmore David
Published: October 2018

Reinforced concrete structures can be designed and maintained to achieve long service lives, even in aggressive chloride environments. Unfortunately, many structures, such as bridges, piers, and wharves, show signs of active corrosion (e.g. rust staining, concrete spalling, etc.) in as little as 5 to 10 years. Left unchecked, chloride induced corrosion can lead to major structural problems. Many severely corroded structures have been replaced at great expense and with significant disruption to the public. As an alternative to demolition and replacement, a viable option is to repair and protect severely deteriorated structures utilizing a galvanic encasement that both structurally upgrades and catholically protects the structure. This approach can provide an effective, low maintenance galvanic cathodic protection solution for deteriorated concrete structures. Galvanic encasements consist of distributed galvanic anodes embedded in a concrete overlay or concrete jacket. The galvanic encasement may include additional reinforcing steel to create a one-step structural repair and protection system. This paper presents case studies on the use of galvanic encasements to repair and protect reinforced concrete structures. Long term monitoring of field projects over more than 10 years indicates that effective cathodic protection can be provided for 20 to 40+ years.
Investigations on the detectability of water intruding into bridge deck sealings by electrical resistivity measurements
Authors: Driessen Carla , Raupach Michael
Published: October 2018

In the context of a current joint research project a monitoring system to detect leakages in bridges is implemented by using a textile reinforced concrete interlayer which consists of two carbon meshes with a spacing of 15 mm and a new developed mortar. Between the two carbon meshes the resistivity is measured with alternating current. If a leakage in the bridge deck sealing occurs and water gets into the interlayer a drop in the measured resistivity occurs and the leakage is detected. In this case repair measures can be carried out in an early stage or a preventive cathodic protection can be switched on. To assess which sizes of leakages are detectable under which boundary conditions, laboratory tests and tests on a 100 m2 outdoor demonstrator were carried out. Therefore leakages were artificially produced and the changes in the measured resistivity values were observed under different climatic conditions. Impacts such as the form of the leakages or the position of the leakages in the measuring field were varied.
Condition assessment of reinforced concrete beams – Comparing digital image analysis with optic fibre Bragg gratings
Authors: Kearsley Elsabe , Jacobsz SW
Published: October 2018

Reinforced concrete is the most widely used construction material and thus effective condition assessment of reinforced concrete elements forms a significant part of structural health monitoring. An effective structural health monitoring system should be able to give the owner prior warning that structural elements are reaching conditions approaching either serviceability or ultimate limit states. The aim of this investigation is to compare strain data recorded during load testing of a reinforced concrete beam using Fibre optic Bragg Gratings (FBG) and a photographic technique to determine circumstances most suitable for the use of each of the techniques. The test results indicate that FBG sensors can be used to detect small strains as well as large strains in uncracked concrete elements, while optical images can be used to accurately map crack development over the surface area of the structure.
The MFL technique – Basic application for PT cable break detection in concrete structures
Authors: Wilcke Martin , Walther Andrei , Szielasko Klaus , Youssef Sargon
Published: October 2018

From the beginning of building techniques creating pre-stressed and accordingly post-tensioned concrete structures until the late 1980ies manufacturers and construction companies dealt with pre-stressing steel material vulnerable to stress corrosion cracking. Almost every load-bearing structure requires regular inspection on a mandatory basis. Due to knowledge of pre-stressed structural reinforcement susceptible to stress corrosion cracking being used during construction or visible damage alongside the tendon area arises the demand for detailed investigation of cracks within the post-tensioned steel elements. Even though the pre-stressed steel elements of a structure are not especially at risk for stress corrosion cracking by its manufacturing process, the natural deterioration of the building fabric and manifold eventual defects and failure during structure erection encourage the requirement for an inspection of their structural integrity at least within the most important load-bearing areas. Therefore needed investigations can be carried out by application of the non-destructive magnetic flux leakage measurement technique for single bar elements and stranded wire tendons even inside cladding tubes. This testing method is subject to successful research work for more than 30 years now and has proven its validated functionality with impressive results on a big number of investigated structures including bridge elements, truss beams and container components.Starting with the basic physical measurement principle of magnetic flux leakage for dipole-formation in the area of fractures of the magnetized pre-stressed steel elements this document presents the practical application possibilities and development history of the testing method.With the consecutively presented further development of the BetoFlux-System we can provide a piece of testing equipment which combines the advantages of a pure physical measurement principle with the economical requirements for an on-site-application to investigate pre-stressed reinforcing steel elements at an early stage prior to structural collapse hazards.
Characterization tools for shrinkage-compensating repair materials
Authors: Bissonnette Benoît , Essalik Samy-Joseph , Lamothe Charles , Jolin Marc , Courard Luc , Gagné Richard , Morin Richard
Published: October 2018

Achievement of dimensional compatibility is one of the most important considerations in order to consistently achieve lasting repair works that do not undergo harmful cracking. Drying shrinkage of Portland cement concrete is generally inevitable and, although its magnitude can be reduced by optimizing or modifying the composition parameters, it remains significantly larger than its ultimate tensile strain. Conversely, the use of shrinkage-compensating concrete (ShCC) may allow to achieve a zero-dimensional balance with respect to drying shrinkage, through the use of a mineral expansive agent. The experimental work carried out in recent years at Laval University to evaluate the potential of shrinkage-compensating concretes (ShCC) for use as repair materials has in fact yielded quite promising results. Nevertheless, more research is required to turn ShCC systems into a truly dependable and versatile repair option. Among the issues still unresolved, suitable tests methods must be developed, not only to better characterize ShCC, but also to guide the specifications and perform field quality control. Efforts have thus been devoted to adapt or develop test procedures intended to better capture the particular volume change behavior of ShCC’s. The paper presents two test procedures intended to assess the shrinkage-compensating potential and the effective strain balance of ShCC in restrained conditions.
Intrinsic modification of repair mortars made with EVA and CaO, impacts at the earlier ages
Authors: Ngassam Inès L. Tchetgnia , Schmidt Wolfram , Beushausen Hans , Kühne Hans-Carsten
Published: October 2018

Many studies have been realised on polymer-modified mortars (PMMs). Among the polymers used, ethylene vinyl acetate (EVA) has revealed evident interaction between calcium ions and its acetate groups. Most of the studies have shown a positive impact of EVA on mortar performance, which is enhanced by the combination of the EVA with calcium oxide CaO. However, there is still a lack of understanding of the nature of these interactions and no clear link has been established between these interactions and the properties of the cementitious materials at early ages. This article aims to tackle this topic by focusing on the evolution of EVA particles in a pore solution and the properties of a cement modified with EVA and CaO, especially the rheological behaviour. As results, it is observed that the zeta potential of the pore solution decreases when EVA is added. Furthermore, the hydrodynamic radius of this polymer tends to increase over time in the pore solution. On the other hand, the EVA tends to delay the setting time while the CaO accelerates it. For the rheological state, EVA tends to govern the plastic viscosity of the cement paste while CaO governs the yield stress and these parameters are not affected by the mixing time during the first 100 min. Their combination enhances these rheological parameters.
Using GLP as Partial Replacement in Cement Mortars
Authors: El-Tair Ahmed , Youssef Passant , El-Nemr Amr
Published: October 2018

For the last decade, recycled construction wastes were promoted to be reused in concrete manufacture process to achieve sustainability of structures. Recently, crushed glass has been investigated many researchers [1-9] as a partially replacement for coarse and fine aggregates, finally; cement. This study investigated the influence of both the mechanical behaviour and microstructure of cement mortar when partially replaced by powder glass. Here in, six mixes were design for six percentages of replacement; considered incrementally, each 5% (0%, 5%, 10%, 15%, 20%, and 25%) of cement weight. 36 mortar cubes and 18 prisms were cast and cured for 28 days. Then after, the specimens were tested in compression and indirect splitting tensile strength to determine their influence on mechanical properties. In addition, scanning electron microscope as well X-ray diffraction was used to examine their microstructure cement. The results showed that 20.5% increase in compressive strength at 7 days while at 28 days, the compressive strength increases insignificantly by value of 0.3% when using 5% GLP replacement. In addition, 46.9% increase was achieved in flexural strength at 28 days. Furthermore, the SEM micrographs observed some clear glass particles while the XRD clearly monitored the high count of silica and could not detect the calcium silicate that represents the amorphous part.
UHPFRC for concrete repair
Authors: Maltais Alexandrine , Petrov Nikola , Thibault Michel , Bissonnette Benoit
Published: October 2018

As part of the St. Lawrence Seaway lock maintenance, the current practice is to perform concrete repairs entirely with reinforced concrete, using either ordinary concrete or high performance concrete (HPC) mixtures. However, with the recent advances in the field of ultra-high performance fiber-reinforced concrete (UHPFRC), the use of this new material is considered in view of improving the overall performance of repairs. The goal is to implement repairs capable of dissipating a lot of energy before breaking when a ship hits a concrete lock wall. Numerous rehabilitation materials and methods have been experimented in the past. They all were unsuccessful due to inadequate shear and impact strength characteristics of the repair materials used. These needs can be efficiently fulfilled with UHPFRC, with their superior mechanical properties and very high energy-dissipation ability. To analyze the in-situ behavior of UHPFRC, two main mixture designs were investigated: a 160-MPa mixture containing 3% of steel fibers and a 120-MPa mixture containing 3.5% of a steel fiber blend. Thick repairs with average depths of 700 mm were carried out during the winter shut down period, in very harsh climatic conditions (-12 °C, gusty wind). The performance exhibited by the repairs after a full year shows that UHPFRCs can withstand very effectively the impacts from the transiting vessels
Use of polypropylene fiber and silica fume modified concrete as a repair material
Authors: Liu Jing , Liu Wen , Guan Shugang , Guo Chao , Zheng and Xinguo
Published: October 2018

Polypropylene fiber and silica fume were used to get high impermeability and cracking resistance concrete as a repair material. Results showed just incorporating fiber (without silica fume) had no obvious improvement on strength and impermeability of concrete. The usage of polypropylene fiber and silica fume together in concrete increased the compressive strength and caused a significant reduction in chloride permeability. The improvement of fiber and silica fume on concrete properties was attributed to both the anti-cracking effect from polypropylene fiber and densification reinforcement action to the interfacial transition zones of both fiber —matrix and aggregate—cement paste from silica fume. These properties made them suitable for certain applications such as concrete repairs.
Durability of flax/bio-based epoxy composites intended for structural strengthening
Authors: Benzarti Karim , Chlela Robert , Zombré Wendlamita , Quiertant Marc , Curtil Laurence
Published: October 2018

Environmentally friendly FRP composites, made of natural fibres and bio-based polymer matrices, may be used as externally bonded reinforcement for civil structures or buildings subjected to moderate outdoor conditions, in replacement of traditional carbon/epoxy systems. However, a major drawback of natural fibers is their sensitivity to moisture, which can affect both the mechanical properties of FRP composites and their adhesive bond with concrete. This research, funded by the French National Research Agency (ANR Project MICRO), aims at studying the influence of hygrothermal ageing on the performances of “green composites” manufactured by hand lay-up process using unidirectional flax fabrics and a bio-based epoxy matrix. The test program consists in subjecting FRP laminates and FRP strengthened concrete slabs to accelerated ageing conditions under various combinations of temperature and humidity. Aged laminates are then periodically characterized by tensile tests and interlaminar shear tests, while the bond properties of concrete/composite assemblies are assessed by pull-off tests. This paper presents the first results of this ongoing program which is scheduled over a period of 2 years. Results are discussed in the light of complementary investigations (water sorption behaviour, microscopic observations and evaluation of the glass transition temperature by differential scanning calorimetry – DSC) in order to relate observed performance evolutions to actual microstructural changes or damage processes taking place in the material.
Guidelines for concrete surface preparation: 10 years research and experience
Authors: Courard Luc , Bissonnette Benoît , Garbacz Andrzej , Vaysburd Alex M. , von Fay Kurt F.
Published: October 2018

To repair reinforced concrete infrastructures requests specific preparation operations needed for guaranteeing compatibility between substrate and new materials as well as the development of adhesion properties. These guidelines contain design and construction recommendations for surface preparation of concrete for repair and overlay. The paper illustrates current knowledge, best practices and results of the research concerning the surface preparation of concrete prior to application of repair/overlay materials. This is based on 10 years research activities on this topic through scientific cooperation programs between Wallonia, Quebec and Poland and a document edited by U.S. Bureau of Reclamation (Denver, CO, U.S.A.) entitled Development of Specifications and Performance Criteria for Surface Preparation Based on Issues Related to Bond Strength.
Bond behaviour of thin concrete overlays for maintenance of concrete pavements
Authors: Breitenbücher Rolf , Schulte-Schrepping Christoph , Kunz Sebastian
Published: October 2018

Concrete pavements are exposed to a number of stresses during their service life, mostly resulting from traffic and climate conditions. In consideration of the continuously rising traffic volume, the durability requirements of concrete pavements become more and more significant. In this context, maintenance and repair become increasingly important. Small-scale repairs like spalling at edges up to the replacement of whole slabs are proven in several cases. In contrast, large-scale maintenance techniques for partial repairs of whole pavement sections are not available, yet. If the upper layer concrete is deteriorated, while the lower layer and the base course are still intact, the whole pavement needs to be replaced, due to a lack of alternatives. Therefore new maintenance techniques like the application of concrete overlays are needed for an economic rehabilitation and the prevention of an unnecessarily long traffic disruption by time-consuming maintenance of complete pavements. The relevant questions how a durable bond between old and new concrete can be ensured and which parameters affect this bond, were investigated in representative studies on large-scale concrete beams with a thin concrete overlay on existing concrete.
Behavior of RC beams strengthened in shear with ultra-high performance fiber reinforced concrete (UHPFRC)
Authors: Sakr Mohammed A. , Sleemah Ayman A. , Khalifa Tarek M. , Mansour Walid N.
Published: October 2018

This paper investigates the behavior of RC beams strengthened in shear with UHPFRC. In order to ensure high quality and facilitate the strengthening process on site applications, it has been considered to apply UHPFRC as a plate pasted on concrete using epoxy. In addition to the control beam, two strengthened RC beams using prefabricated UHPFRC plates were prepared and tested. All beams had the same rectangular cross-section geometry (150mm x 300mm x 2000mm). Two different techniques were considered during the strengthening process; the first application was the addition of two 30 mm UHPFRC plates, whereas the second beam strengthened using one 60 mm UHPFRC plate. Results showed that strengthening RC beams using two UHPFRC plates improved load carrying capacity with 145 % comparing with the control beam. Moreover UHPFRC plate in case of strengthening one side of the RC beam prevented shear cracks from appearing on the strengthened side.
Characterization and application of FRCM as a strengthening material for shear-critical RC beams
Authors: Younis Adel , Ebead Usama
Published: October 2018

This paper investigates the effectiveness of fabric reinforced cementitious matrix (FRCM) systems in shear-strengthening of reinforced concrete beams. Three types of FRCM systems were considered, namely, polyparaphenylene benzobisoxazole (PBO)-FRCM, Carbon-FRCM, and Glass-FRCM. At first, tensile characterization test was performed on 15 FRCM coupons with the aim of identifying the tensile properties of the FRCM systems adopted. After that, seven shear-critical RC beams were tested under three-point loading, with the consideration of two test parameters: (a) FRCM material (glass/carbon/PBO); and (b) strengthening configuration (full/intermittent). The study results revealed the use of FRCM as a strengthening material to achieve a considerable improvement in the structural capacity of shear-critical RC beams. The average gain in the shear capacity of the FRCM-strengthened beams was 57%. The beam specimens strengthened with carbon-FRCM showed the highest improvement as compared to those strengthened with glass-and PBO-FRCM systems. As intuitively expected, the shear capacity improvement achieved with the full-length strengthening systems was generally higher than that with the intermittent counterparts.
Durability of concrete with CFRP wrapping
Authors: Yu Qian-Qian , Li Xiang , Gu Xiang-Lin
Published: October 2018

Carbon fibre-reinforced polymer (CFRP) material has a high strength-to-weight ratio and good resistance to corrosion and environmental attacks. It has been widely used in rehabilitation of aged infrastructure. However, the durability of the strengthened system has not been yet assessed thoroughly since most of the previous study was conducted based on accelerated tests while the long-term investigation was less reported. This paper investigated the effect of CFRP wrapping on the axial behaviour of concrete cylinders subjected to different environments for more than 13 years. The specimens were exposed to five different conditions, including standard curing, immersion in distilled water, immersion in saturated Na2SO4 solution, outdoor sheltered from the rain, and outdoor without shelter from the rain. Axial compression tests were performed on the wrapped concrete cylinders. The load-bearing capacity and stress-strain responses were recorded. It was found that CFRP wrapping could effectively improve the ultimate strength and ductility of the columns. Though scatter existed, no significant effect of the environmental exposure on the load-bearing capacity of the cylinder specimens was observed which indicates a good durability of the strengthening system.
Rehabilitation of the Komati River Bridge B1604
Authors: Strydom Johnnie , du Plessis Etienne , Pieters Lourens
Published: October 2018

In this paper, the retrofitting and rehabilitation of the Komati River Bridge, Bridge B1604 on the N4 in Mpumalanga, South Africa, is presented. The bridge consists of 17 simply supported spans, 20 metres in length, with a post-tensioned beam and slab deck. The deck is supported on steel bearings, and the abutments are of the spill through reinforced concrete type. The wall type piers are founded on shallow rock with pad footings. The bridge was constructed in 1940, and in 1998 the deck was widened on both sides with larger pre-cast, post-tensioned beams. SMEC South Africa under a Trans African Toll Concessions (TRAC) appointment inspected the bridge in 2014 as part of South African National Roads Agency’s (SANRAL) routine bridge inspections. It was found that the old beams had extensive bending cracks. The cracks were mainly caused by locked in loads due to the jamming of the steel bearings. The rehabilitation design was completed by SMEC South Africa and was implemented by DSC Zendon cc with TRAC as the client in 2017. The repairs included the replacement of 272 steel bearings with elastomeric bearings, crack injection and carbon fibre strengthening of 68 deck beams. DSC Zendon cc utilised mobile platforms to access the soffit of the deck. Hanging platforms were used to minimise the impact on the Komati River and its crocodiles.
Influence of superabsorbent polymer on the splitting tensile strength and fracture energy of high-performance concrete
Authors: Olawuyi Babatunde James , Boshoff William Peter
Published: October 2018

Superabsorbent polymers (SAP) addition as an internal curing (IC) agent in concrete is an approach being adopted for the mitigation of autogenous shrinkage. Micro-voids created by SAP are arguably believed to be detrimental to the mechanical properties especially the fracture tendencies of the concrete. This paper presents the report of an experimental study of SAP’s influence on the splitting tensile strength and fracture energy of low water/binder (W/B) high-performance concrete (HPC). Reference HPC mixtures (M1F, M1S, M2 and M3) designed for a 28-day minimum cube compressive strength of 70 N/mm2 (MPa) were examined for the effect of SAP grain size, content and binder type on the above stated properties. Wedge splitting test was carried out on 100 mm cube specimen of HPC containing varied SAP contents (0.2, 0.3 and 0.4 by weight of binder (bwob)) and SAP sizes, cured by water immersion for 28, 56 and 90 days respectively. The results obtained was plotted as splitting force (Fsp in kN) against the crack mouth opening displacement (CMOD in mm) for computing the work of fracture (Wf), which is the area under the Fsp CMOD curve. The study concludes that the splitting tensile strength and fracture energy of the HPCs are not directly affected by SAP addition (i.e. neither grain size nor content).
Mechanical properties of Hybrid steel/PVA fibers reinforced high strength concrete
Authors: Abbass Wasim , Khan M. Iqbal
Published: October 2018

The high strength concrete exhibits improved compressive strength with drawback of brittle failure due to lack of tensile strength which can be catered by the addition of fibers. The efficient use of fibers with hybridization at macro and micro level can improve mechanical properties of high strength concrete. The effect of hybridization of hooked end steel macro fibers (60 mm) and PVA micro fibers (12 mm) with different dosages was investigated in this research work. The different percentage of steel and PVA were hybridized to find out the best combination of hybridized fibers in high strength concrete. The compressive and flexural properties of high strength concrete along with complete load vs deflection behaviour of hybrid fiber reinforced concrete were investigated. The results revealed that hybridization of macro and micro fibers provided better improvement in flexural performance. It was observed from the results that the hybrid combination of fibers of 1% macro steel fiber and 0.15% micro PVA fibers proved to be the best for enhancement in flexural performance of high strength concrete.
Steel fibre-reinforced concrete: Multi-scale characterisation towards numerical modelling
Authors: Zeranka Stephan , van Zijl Gideon
Published: October 2018

The Mode I and II fracture response of steel fibre-reinforced concrete is investigated experimentally at the single fibre and composite scale. A constitutive material model is developed and is implemented in a numerical procedure via a user material (UMAT) in the commercial finite element package ABAQUS. An empirical model reconciles the single fibre and composite scale for Mode II fracture.
Measured temperature effects during the construction of a prestressed precast concrete bridge beam
Authors: Küsel Frank , Kearsley Elsabe , Butler Liam J. , Skorpen Sarah A. , Elshafie M.Z.E.B.
Published: October 2018

Prestress losses in precast concrete beams include the short-term effects of elastic shortening and the long-term effects of concrete shrinkage, concrete creep and steel relaxation. Temperature effects are, however, excluded. The aim of this research was to monitor the behaviour of a prestressed precast concrete bridge beam, focussing on temperature effects and destressing. Successful monitoring assists in comparing the real performance of a structure to the expected design performance, and in managing the durability of the monitored structure. The effect of temperature variation on strains in prestressed beams was investigated by instrumenting a precast beam. Temperature and strains were monitored from the day of casting up to and including the cutting of the pretensioning strands. Daily temperature variations causing vertical non-linear temperature profiles resulted in internal strains of up to 28 % of the strains caused by destressing. It was therefore concluded that thermal effects before destressing resulting from elevated curing temperatures and daily temperature changes should be considered in the calculation of prestress losses. The monitoring techniques used were successful in determining the stresses and strains within the beam, which can be used to compare real prestress losses with the losses assumed in design.
Concrete hydration temperatures for the design of crack-width reinforcement in concrete water-retaining structures – design values versus in-situ values
Authors: Angelucci Matteo
Published: October 2018

Cracking in concrete can occur due to temperature changes at early ages and exposure to ambient temperature changes in the long term. Design codes and standards allow engineers to design for cracking by quantifying the effects of thermal variations into outputs such as limiting crack widths and reinforcement configurations. Design values given in these codes are however not fully understood by many users, may not be representative of recent developments in concrete materials technology and can potentially result in over-conservative designs. In this paper, concrete hydration temperatures were measured on site using a Thermocouple Data Logger and compared to values used in the project-specific design with the intention of providing a basis on which a database of temperatures representative of mixes commonly used in the South African industry may be compiled. Findings revealed that measured temperature values were around 30 – 50% lower than those given in design codes. Among the reasons identified for this is the fact that readily used design codes for crack-width design of water-retaining concrete structures in South Africa were compiled with data obtained from the use of 42.5 N cements, which may well have been quite different from the now more modern and readily available 52.5 N cements. Furthermore, design codes focus extensively on factors like binder content, binder type and formwork type, while the effects of other factors such as coarse aggregate type, coarse aggregate nominal size and construction sequence (which also play a significant role) are not quantified in the selection process of temperature values. Recommendations for further studies are made which aim to incorporate a wider variety of factors that affect development of thermal properties of concrete. This can allow members of the project team (engineer, contractor) to act during the relevant stages of design/construction of a project to mitigate thermal effects that can incur unwanted cracking.
Die Huntington-Erkrankung
Authors: Lang Christina , Landwehrmeyer Bernhard G.
Published: October 2018

Die Huntington-Krankheit ist durch fortschreitende Beschwerden mit motorischen Beeinträchtigungen und kognitivem Abbau sowie Verhaltensauffälligkeiten
gekennzeichnet. Die Ursache liegt in einer Verlängerung einer Triplett-Repeat-Sequenz in einem spezifischen Gen, Huntingtin-Gen genannt. Bei einer deutlich
erhöhten Anzahl an Triplett-Repeats, kann die Erkrankung bereits im Jugend- oder jungen Erwachsenenalter beginnen. Eindrücklichstes motorisches Symptom ist die
Chorea, die sich in Form von unwillkürlichen, plötzlichen, kurzen Bewegungen darstellt. Bereits vor dem Auftreten von motorischen Symptomen können Patienten
kognitive Einschränkungen entwickeln. Die kognitiven Einschränkungen betreffen primär Exekutivfunktionen wie beispielsweise Problemlösen. Als dritter großer
Symptombereich können in jedem Stadium der Erkrankung psychiatrische Störungen hinzukommen. Häufig leiden Patienten unter Depressionen, später kommen vermehrt
Irritabilität oder Perseverationen vor. Das Genprodukt Huntingtin ist ubiquitär in allen Körperzellen vorhanden – man vermutet verschiedene Funktionen, die
insbesondere in Neuronen wichtig zu sein scheinen. Aufgrund des autosomaldominanten Vererbungsmodus hat die prädiktive Diagnostik bei dieser Erkrankung einen
wichtigen Stellenwert. Trotz der Entdeckung der genetischen Ursache vor nun 25 Jahren ist die Behandlung der Huntington-Krankheit gegenwärtig noch auf die
Therapie der Symptome und den Erhalt von Funktionen beschränkt. Für die Huntington-Krankheit gibt es noch keine Behandlung, die eine weitere
Krankheitsprogression bremsen oder den Krankheitsbeginn verzögern könnte. Allerdings gibt es Hoffnung – klinische Studien mit Therapieformen, die auf die
genetische Ursache abzielen, sind bereits auf dem Weg.
DiaLife – zusammen leben mit Diabetes
Authors: Fabisch Gottlobe
Published: October 2018

DiaLife – zusammen leben mit Diabetes heißt das erste Schulungsprogramm für Angehörige von erwachsenen Menschen mit Diabetes mellitus. Es schließt eine große Bedarfslücke, denn die chronische Erkrankung beeinflusst nicht nur das Leben des Betroffenen, sondern in entscheidendem Maße auch dessen direktes soziales Umfeld: Lebenspartner, Geschwister, Eltern, Verwandte oder Freunde
1
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Diastolische Herzinsuffizienz bei Typ-2-Diabetes
Authors: Heilmeyer Peter , von Bibra Helene
Published: October 2018

Seit Jahrzenten empfehlen Fachgesellschaften für Patienten mit Typ-2-Diabetes eine fettarme und kohlenhydratbetonte Ernährung. Diese kann aber zu einer Insulinresistenz führen, was wiederum eine diastolische Dysfunktion zur Folge haben kann. Deshalb wurde bei einem adipösen Typ-2-Diabetiker mit Herzinsuffizienz und Insulinresistenz ein anderes Konzept angewendet: Eine dreiwöchige diätetische Therapie mit kohlenhydratreduzierter Kost und moderatem Bewegungstraining.
Diabetische Neuropathie
Authors: Chrubasik-Hausmann Sigrun
Published: October 2018

Obwohl die diabetische Polyneuropathie meist distal symmetrisch auftritt und oft mit Fußgeschwüren einhergeht, kann sie sich auch im Mund als Burning-Mouth-Syndrom oder gastrointestinal mit entsprechenden abdominellen Dysfunktionen bemerkbar machen. Phytotherapeutische Zubereitungen stellen eine Alternative zur schulmedizinischen Behandlung dar, allen voran lokal applizierbare Extrakte aus dem spanischen Pfeffer (Capsicum annuum). Aber auch ein hochprozentiges Pfefferminzöl und andere komplementärmedizinische Verfahren wie z. B. lokale Kälteanwendungen oder transkutane Nervenstimulation sind einen Versuch wert. Es gibt Hinweise, dass durch eine frühzeitige Einnahme von pflanzlichen Antioxidantien die diabetische Stoffwechsellage gebessert und damit das Fortschreiten der Neuropathie verzögert werden kann.
Wünsche, Sorgen und Bedürfnisse bezüglich der Insulinpumpentherapie im Alter: Ergebnisse einer Befragung bei Menschen mit Typ-1-Diabetes mellitus im höheren Lebensalter und von Diabetesfachkräften
Authors: Grammes Jennifer , Küstner Eva , Demattio Silvia , Priesterroth Lilli , Heinemann Lutz , Kubiak Thomas
Published: October 2018

Hintergrund Mehr als die Hälfte aller Menschen mit Diabetes in Deutschland ist älter als 65 Jahre. Für eine erfolgreiche Insulinpumpentherapie (Continuous Subcutaneous Insulin Infusion; CSII) im hohen Erwachsenenalter sind Wünsche, Sorgen und Erfahrungen älterer Menschen mit Typ-1-Diabetes, erlebte Barrieren und förderliche Bedingungen von zentraler Bedeutung.

Methodik Ältere Menschen mit Typ-1-Diabetes, die sich mit einer CSII behandeln (n = 136), sowie Fachkräfte aus dem Diabetesbereich (Diabetes Health Care Professionals; HCP; n = 96) nahmen an einem Fragebogensurvey teil, in dem anhand zweier offener Fragen Wünsche, Sorgen und Erfahrungen älterer Menschen mit Typ-1-Diabetes erfasst wurden. Durch systematische, induktive Datenreduktion wurden aus den Antworten zentrale Kategorien und Subkategorien identifiziert.

Ergebnisse Es konnten vier Inhaltskategorien abgeleitet werden: (1) Fremdhilfe, (2) Technische Innovation, (3) Gesundheitspolitik und (4) Umstellung auf ICT. Am häufigsten wurde das Vorhandensein von kompetenter Hilfe von außen durch den HCP aus dem Diabetesbereich sowie durch Angehörige und andere Betroffene gewünscht. Die Befragten formulierten klare Wünsche an ein altersgerechtes Design von Insulinpumpen (z. B. großes Display, Sprachsteuerung). Sorgen der Pumpenträger/-innen bezogen sich u. a. auf Hilflosigkeit, Akutkomplikationen und verschlechterte Stoffwechsellage.

Schlussfolgerung Die Befragten äußerten große Sorgen und Unsicherheiten bezüglich CSII im Alter, auf die seitens der Diabetologie, Industrie und Gesundheitspolitik eingegangen werden sollte, um Insulinpumpentherapie altersgerecht zu gestalten.
Mit Leidenschaft für Lehre, Forschung und Praxis
Authors: Schwarz Christiane , Stamm Anja
Published: October 2018

Zum April 2018 berief die Universität zu Lübeck Christiane Schwarz zur Professorin für Hebammenwissenschaft. Die promovierte Hebamme übernahm damit den ersten dualen Bachelorstudiengang für Hebammen an der medizinischen Fakultät einer Universität in Deutschland. Im Interview mit DIE HEBAMME verrät die engagierte Praktikerin und Wissenschaftlerin, was sie nach dem ersten Semester begeistert und welche Perspektiven sie in der neuen Rolle für die Berufsgruppe sieht.
Anwendung von Pflegeprodukten und Ölen in der Säuglingspflege
Authors: Dachs Claudia , Busmann Ulla , Merk Hans F.
Published: October 2018

Die Hautpflege bei Neugeborenen und Säuglingen ist ein wichtiges Thema in der Beratung junger Eltern. Teil 3 der Artikelserie verrät, wie Öle in der Säuglingspflege sich auf die Hautschutzbarriere auswirken, welche Inhaltsstoffe in Pflegeprodukten enthalten sind und welche Empfehlungen zur Beschaffenheit von Reinigungs- und Pflegeprodukten für die Säuglingshaut auf Basis wissenschaftlicher Untersuchungen gegeben werden können.
Andere Neurodegenerative Parkinson-Syndrome
Authors: Pinkhardt Elmar H.
Published: October 2018

Zu den neurodegenerativen Parkinson-Syndromen abseits des Idiopathischen Parkinson Syndroms (IPS) zählt eine heterogene Gruppe von Erkrankungen, die als eines
der Hauptsymptome einen meist hypokinetisch-rigiden Parkinsonismus zeigen und als atypische Parkinson-Syndrome zusammengefasst werden. Diagnostisch stellen
diese Erkrankungen im klinischen Alltag eine Herausforderung dar, da sie gerade im frühen Verlauf teils schwierig von einem IPS unterscheidbar sind und auch
untereinander phenotypisch weite Überlappungen zeigen. Die Therapie erfolgt momentan rein symptomatisch, wobei ein Therapieversuch mit Dopaminergika bei allen
diesen Erkrankungen gerechtfertigt ist, da zum Teil ein – wenn auch zeitlich limitiertes – Ansprechen auf Levodopa vorliegt.
Pädiatrische Radioonkologie
Authors: Seidensaal Katharina , Harrabi Semi Ben , Debus Jürgen
Published: October 2018

Als Querschnittsdisziplin ist die Strahlentherapie in der Behandlung vieler onkologischer Krankheitsbilder vertreten, und deckt damit nahezu das gesamte Spektrum
der Onkologie ab. Aufgrund der Komplexität der Krankheitsbilder, der Seltenheit der Erkrankungen und den speziellen Anforderungen multimodaler Therapieregime
nimmt die pädiatrische Radioonkologie in diesem Spektrum eine Sonderstellung ein. Sowohl das besondere Nebenwirkungsprofil als auch der erhöhte logistische und
technische Aufwand erfordern neben einer engen interdisziplinären Abstimmung insbesondere die Erfahrung eines auf die Behandlung pädiatrischer Patienten
spezialisierten Teams. Dank ihrer besonderen physikalischen Eigenschaften mit einer sehr hohen Konformität verspricht die Protonentherapie bei gleicher
Effektivität eine geringere Nebenwirkungsrate im Vergleich zur konventionellen Radiotherapie mittels Photonen. Der folgende Artikel bietet einen kurzen
Überblick über die Besonderheiten der pädiatrischen Radioonkologie.
90 % aller Krebsheilungen durch Chirurgie und Strahlentherapie
Authors: Wiedemann Günther J.
Published: October 2018

Für die etwa 482 470 im Jahr 2016 neu an Krebs Erkrankten erwartet das Robert Koch-Institut eine deutlich über 50 %ige Heilungswahrscheinlichkeit (Männer: 62 %,
Frauen: 67 %). Die altersstandardisierte Krebssterblichkeit geht weiter zurück (Männer: um 13 %, Frauen: um 9 %) – gute Nachrichten für die mindestens 1,6
Millionen Krebspatienten (deren Diagnose nicht länger als 5 Jahre zurückliegt), die in Deutschland leben. Bei den meisten Krebsentitäten erreichen Krebspatienten,
die rezidivfrei 5 Jahre überlebten, die durchschnittliche Lebenserwartung der gleichaltrigen Männer und Frauen. Die absolute Krebssterblichkeit nimmt mit der
zunehmenden Zahl der Krebskranken allerdings weiter zu.
Chlorophyll Breakdown – How Chemistry Has Helped to Decipher a Striking Biological Enigma
Authors: Kräutler Bernhard
Published: October 2018

How the fall colors arise and how chlorophyll (Chl) breakdown occurs in higher plants has remained enigmatic until three decades ago. Fundamental insights into this fascinating puzzle have been gained, meanwhile, by basic contributions from plant biology and chemistry. This short review is a personal account of key advances from synthetic, mechanistic, and structural chemistry that led to the discovery of the bilin-type Chl catabolites and helped elucidate the metabolic processes that generated them from Chl.

1 Introduction

2 Discovery and Structure Elucidation of a First Non-Green Chl Catabolite

3 Structure Elucidation of Fleetingly Existent Blue-Fluorescent Chl Catabolites

4 The Red Chl Catabolite – Key Ring-Opened Tetrapyrrole Accessed by Partial Synthesis

5 Synthesis of ‘Primary’ Fluorescent Chl Catabolites by Reduction of Red Chl Catabolite

6 Nonfluorescent Chl Catabolites from Isomerization of Fluorescent Chl Catabolites

7 Persistent Fluorescent Chl Catabolites and Blue-Luminescent Bananas

8 Discovery, Structure Elucidation, and Biological Formation of Dioxobilin-Type Chl Catabolites

9 Occurrence, Partial Synthesis, and Structure of Phyllochromobilins, the Colored Bilin-Type Chl Catabolites

10 Conclusion and Outlook
Regioselective and Catalyst-Free Epoxidation of (E)-3-[3-(2-Hydroxyaryl)-3-oxoprop-1-en-1-yl]chromones
Authors: Hammadi Mohamed , Talhi Oualid , Silva Artur , Ameraoui Rachid , Hassaine Ridha , Bouchama Abdelghani , Abdeldjebar Hasnia , Belmiloud Yamina , Brahimi Meziane , Paz Filipe , Bachari Khaldoun
Published: October 2018

The uncatalyzed reaction of hydrogen peroxide with (E)-3-[3-(2-hydroxyaryl)-3-oxoprop-1-en-1-yl]chromones resulted in a regio­selective epoxidation of the chromone intracyclic C(2)=C(3) double bond to afford unique isomeric (E)-7a-[3-(2-hydroxyphenyl)-3-oxoprop-1-en-1-yl]-1aH-oxireno[2,3-b]chromen-7(7aH)-ones in high yields. 2D NMR and single-crystal X-ray diffraction were used to elucidate the structures of the chromanone epoxides. Density functional theoretical studies demonstrated a high electrophilicity of the starting chromones.