bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimizing the Acid Resistance of Concrete with Granulated Blast-Furnace Slag
Authors: Breitenbücher Rolf , Bäcker Jan , Kunz Sebastian , Ehrenberg Andreas , Gerten Christian
Published: October 2018

Concrete for agricultural or industrial applications is often subject to intense acid attack. Most affected structures are sewage structures and biogas plants, natural draught cooling towers or silage silos. Widely independent from acid type, in most cases the acid attack on concrete runs the same way, starting with dissolution of easily soluble calcareous phases like calcium hydroxide. With ongoing attack, calcium-silicate-hydrate crystals (CSH) are also affected by acidic media. In contrast, siliceous phases like silicon-dioxide (SiO2) are widely unaffected by acid attack. While the dissolution of the matrix is increasing with ongoing attack, quarzitic aggregates remain unchanged. Beside the use of coarse SiO2-aggregates, the resistance against acid attack is mainly increased by a minimization of the porosity. For this purpose on one hand, a low water/cement-ratio has to be sought, on the other hand also the fines should be distributed with an optimized grading curve (e.g. Fuller-principle). In practice, this results in a combination of various fine and ultra-fine components, e.g. fly ash, GGBS, silica fume or metakaolin. Such binder compositions lead to a particularly dense microstructure, especially at pore sizes below 1 micron, and a higher chemical resistance due to a lower Ca(OH)2 content. This paper gives an overview on typical acid-resistant concretes, most common applications as well as the effects of the related acid attack and points out the potential of granulated blast furnace slag addition to such concretes.
Changes of microstructure and diffusivity in blended cement pastes exposed to natural carbonation
Authors: Soja Wioletta , Maraghechi Hamed , Georget Fabien , Scrivener Karen
Published: October 2018

This study compares the phase assemblage and pore structure variation of Portland cement and blended cements, containing limestone and burnt oil shale, during carbonation. Hardened cement paste was exposed to natural carbonation (400 ppm of CO2) at a relative humidity of 70 % for one year. Samples were prepared and cured at 95 % RH for 28 days. Reference mixes were exposed to CO2-free atmosphere to decouple the effect of ongoing hydration and drying from that of carbonation. The phase assemblage was investigated using XRD-Rietveld refinement and thermogravimetric analyses. The porosity and pore structure was assessed based on the results from mercury intrusion porosimetry. Additionally preliminary results of gas diffusion experiment of carbonated and non-carbonated samples are presented.
Deterioration model of RC beams under marine atmospheric environment
Authors: Guo Hongyuan , Li Guobing , Gu Xianglin
Published: October 2018

This paper primarily proposes a deterioration model of reinforced concrete (RC) beams under marine atmospheric environment. Considering factors including corrosion initiation time, corrosion rate, corrosion non-uniformity and its effects on mechanical performances of steel bars, a comprehensive model was developed for the assessment of mechanical behaviour of RC beams under marine atmospheric environment. Also, to avoid the shortages brought by the classical truss theory, a modified compression field theory (MCFT) was applied to evaluate the effects of stirrups corrosion on the shear capacity of an RC beam. Then, according to a virtual case, the life-cycle performance of an RC beam was predicted through probability density evolution method (PDEM). Results approved the feasibility and effectiveness of the proposed model. Finally, further study work was pointed out.
Investigation on the transport properties of chlorides in concrete (I) Identification of ITZ
Authors: Ye Tian , Xianyu Jin , Nanguo Jin
Published: October 2018

Concrete is a multiphase composite material, in which the mortar, aggregate and interfacial transition zone (ITZ) have important influence on the chloride ions transport. In this research, the thickness ITZ was measured and the concentration distribution of chloride ions in concrete was obtained through electron microprobe analysis. The experiment results that the thickness of ITZ follows a normal distribution and the size of aggregate shows no clear influence on the thickness of ITZ.
Development of an improved cracking method to reduce the variability in testing the healing efficiency of self-healing mortar containing encapsulated polymers
Authors: Van Mullem Tim , Van Tittelboom Kim , Gruyaert Elke , Caspeele Robby , De Belie Nele
Published: October 2018

Concrete cracking can result in a significant reduction of the durability and the service life due to the ingress of aggressive agents Self-healing concrete is able to heal cracks without external intervention, thereby mitigating the need for manual repair. In the assessment of the healing efficiency of self-healing concrete the to-be-healed crack width is an important parameter and different researchers have emphasised that the variability of the crack width significantly hampers an accurate assessment of the healing efficiency. With two new crack control techniques the variability of the crack width was reduced in order to decrease the variability on the calculated healing efficiency. This paper reports on the application of these techniques for the assessment of self-healing mortar containing encapsulated polyurethane. The healing potential was investigated by looking at the degree of sealing using a water flow test setup. It was observed that by using a crack control technique the variability on the crack width can indeed be reduced. Nonetheless, this does not translate in an equivalent reduction on the variability of the healing efficiency. This indicates that other factors contribute to the variability of the healing efficiency.
Living with AAR: An Engineer’s Perspective
Authors: Wood Jonathan G M
Published: October 2018

In the 1980s some unexpected cases of AAR cracking developed in the UK. There was no guidance on its effects on structures. In Devon many bridges, a car park and the 400 bed Exeter hospital had severe cracking and it was growing. Innovations in testing and analysis on these structures and their concrete led to the development of the IStructE Guidance on Structural Effects of AAR. The severity of damage to the hospital led to its replacement. Other buildings and bridges throughout the UK have benefited from this engineering approach to their management. It has provided a basis for RILEM international guidance. Expansion to date can be determined from surface cracking or loss of stiffness of cores. Well detailed reinforcement, to contain expansion in 3-dimensions, retains strength. Cracking leading to failure can develop where there is no reinforcement aligned to contain it. Petrography can diagnose AAR, even when it is trivial, but cannot quantify its severity. Most structures can live safely with an AAR diagnosis, but the containment provided by the reinforcement must be checked and augmented if necessary. Controlling moisture can slow the reaction, but this is not possible below ground where the worst problems occur.
Effects of alkali-silica reaction on a hydropower structure after 50 years of ongoing deterioration
Authors: Brueckner Rene , Ndugga Noah , Meri Tony C.
Published: October 2018

The Nalubaale hydropower station was constructed between 1949 and 1954. Deterioration of the powerhouse structure was first noticed in 1964 when hairline cracking in the generator floor started to appear. The cracking progressively continued resulting in degradation of the generator floor, upper gallery and structural frame of the powerhouse. It was not until 1990 that alkali-silica reaction (ASR) in the mass concrete elements was identified to be the root cause of the deterioration. The condition of the powerhouse structure was reassessed in 2015 25 years after the investigations in 1990. The assessment comprised the determination of the concrete properties 50 years after ASR had initiated and a comprehensive evaluation of instrumentation data was undertaken to identify the effects of ASR on the powerhouse structure. This paper presents the findings of the condition assessment and provides an update on the concrete properties after more than 50 years of ongoing ASR. It also provides an assessment of the residual life of the structure and proposes rehabilitation methods to control the effects of ASR.
Towards understanding corrosion initiation in concrete – influence of local concrete properties in the steel-concrete interfacial zone
Authors: Boschmann Käthler Carolina , Angst Ueli M. , Elsener Bernhard
Published: October 2018

Chloride-induced corrosion is the most common deterioration process for reinforced infrastructure objects. Improving the understanding of the conditions for initiation of localized corrosion is urgently needed. Research is focused on the influence of “defects” at the steel-concrete interface (SCI), as these weak points might be responsible for corrosion initiation. In contrast to numerous studies with “lab concrete”, this study reports results from reinforced concrete cores drilled from old infrastructure objects containing a non-corroding rebar. In contrast to laboratory studies, this guarantees real conditions at the SCI comprising also irregularities such as air voids, plastic settlement voids, cracks, etc. This allows to study chloride-induced corrosion in real conditions and to determine the so-called “critical chloride content”Ccrit. Visual inspection of the SCI enables to establish (or not) influences of the local conditions at the SCI andCcrit. It was found thatCcrit strongly decreased with the carbonation depth, even if the carbonation front had not reached the steel. Moreover, coarse air voids and cracks were in this study not particularly susceptible sites for corrosion initiation.
A new approach to determine the chloride threshold initiating corrosion: Preliminary results
Authors: Chalhoub Chantal , François Raoul , Carcassés Myriam
Published: October 2018

The initiation of corrosion by chlorides is traditionally based on the existence of a threshold that would lead to corrosion. Almost all existing approaches considered implicitly that corrosion induced by chlorides is uniform and take not into account the intrinsic localized character of corrosion in reinforced concrete structures. This work aims to implement a new test protocol that takes explicitly into account the localized nature of chlorides-induced corrosion by inducing physical separation between anode and cathode thus permitting to measure the corrosion current. The anodic part allows to test different levels of chlorides and the cathodic part to highlight the ohmic (limiting ionic current by low porosity) and cathodic (restricting access to oxygen due to saturation of porosity, low porosity, dioxygen consumption by additions) control of corrosion. The chloride threshold is set on the basis of a threshold corrosion current that is considered acceptable with respect to the structure’s life. The first results provide a preliminary idea of the variation of corrosion rate in function of chlorides content. This method also highlights the influence of surface condition of the steel-concrete interface on the corrosion current.
Corrosion of steel in concrete due to one and two dimensional chloride ingress
Authors: Zakka Ze Gyang , Otieno Mike
Published: October 2018

This paper presents results of an ongoing research of the effect of 1D and 2D chloride ingress on concrete resistivity and corrosion rate of steel reinforcement. 12 concrete beams made with concrete of binder blend PC(50)/GGBS(50), w/b = 0.40, 10 mm steel reinforcement rods at concrete cover of 20 mm were used in this laboratory based experiment. The steel reinforcement bars were placed at the middle or at an orthogonal corner of the concrete beams subjected to 1D and 2D chloride ingress respectively. A single crack was induced using 3-point bending on one-half of the beams. The beams were exposed to a repeated cycle of 2 weeks ponding in 5% NaCl and then air drying in ambient laboratory condition for 2 weeks. The corrosion rate of both cracked and uncracked specimens exposed to 2D chloride ingress was significantly higher than that of beams exposed to 1D chloride ingress. The uncracked specimens had lower concrete resistivity values compared to the cracked specimens even though higher corrosion rates were measured.
Towards arresting reinforced concrete corrosion – a review
Authors: Christodoulou Christian , Goodier Chris , Glass Gareth
Published: October 2018

This work reviews developments in the understanding of chloride induced corrosion of steel in concrete from both a kinetic and thermodynamic perspective. Corrosion damage is at least in part attributed to the production of acid at sites of corrosion initiation. Solid phase inhibitors provide a reservoir of hydroxyl ions to inhibit damage. Pit re-alkalisation is identified as an important protective effect in electrochemical treatments used to arrest corrosion. A process like pit re-alkalisation is achieved more easily by impressing current from sacrificial anodes using a power supply which may then be followed by low maintenance galvanic protection to prevent local acidification. Methods for monitoring the steel corrosion rate in electrochemically treated reinforced concrete have been developed and used to assess corrosion risk. Some of these concepts have been adopted in the recent international standard on cathodic protection, ISO 12696:2016, some of the amendments of which are considered in the work presented here.
Long-Term Performance of Hybrid Anodes for Cathodic Protection of Reinforced Concrete
Authors: Dodds Wayne , Christodoulou Christian , Goodier Chris Ian
Published: October 2018

The long-term performance of hybrid anode corrosion protection systems (UK invention disclosed in Patent GB2426008B) was investigated on six bridge structures as part of a holistic approach to corrosion risk management, using the performance criteria in ISO BS EN 12696:2016. The aim of the study was to review the effectiveness of current design approaches to meet the residual service life when the anodes are operating in the galvanic phase. This was achieved by analysing data on the general condition of the structures, the ongoing performance of the installed hybrid anodes, and assessing the subsequent corrosion risk. It was found that the six structures were generally in good condition, 1 to 8 years after refurbishment works, with low associated corrosion risk in areas protected by the hybrid anode systems. This is a positive finding for the wider implementation of hybrid anode systems as an alternative corrosion management technique. The reinforcement in the protected areas remained predominately in a passive condition, with calculated corrosion rates below the ISO 12696:2016 recommended threshold of 2mA/m2.
Maintenance and repair of steel reinforced concrete structures by galvanic corrosion protection – field experiences over 10 years
Authors: Schwarz Wolfgang , Pichlhöfer Alexander , van den Hondel Anthony , Esteves Hernani
Published: October 2018

A galvanic zinc anode system, composed of a zinc mesh embedded into a proprietary solid matrix with ion exchange properties, was developed by CAS. The solid matrix of the embedded zinc anode system (EZA) is based on a tecto-alumosilicate-binder containing additives that prevent passivation of the zinc anode, assure high and durable galvanic activity of the zinc anode and high and durable adhesion towards the concrete overlay. The efficiency of the EZA, applied to concrete members of four types of civil structures – abutment of a road bridge in the Styrian Alps in Austria (2007), support-beams for the bearings of four viaducts in Den Hague in the Netherlands (2009) and a parking deck in Saas Fee in Switzerland (2011), was monitored with embedded reference cells and macro cell sensors. Data collected over a period of up to 10 years show that the EZA protects the steel reinforcement efficiently and reliably. An advanced EZA system – based on the novel shrinkage controlled EZA binder (SEZAC) covered with a novel water vapor permeable epoxy/PU membrane was installed July 2017 at the tunnel entrance of a federal road in the Styrian Alps. The EZA exposed to harsh weathering conditions proves to be efficient in protecting the steel reinforcement from corrosion.
Corrosion protection of embedded steel bars in concrete
Authors: Pistolesi L., , Zaffaroni C.,
Published: October 2018

The design and construction of structures is a responsible decision, based on sound engineering principles, and virtuous and cautious consideration should be paramount. This presentation is based on the results of two different field studies to protect and ensure longevity of structural reinforced steel in structural concrete.1) Application of sacrificial anodes for the galvanic cathodic protection of reinforced steel.2) Application of a cementitious polymer based elastic coating as a viable corrosion protection system against aggressive elements. The use of these materials allows the protection and increases durability of reinforcement steel in concrete, from premature degradation caused by carbonation and chloride attack, ensuring an extended life span.Sacrificial anodes for galvanic cathodic protection are composed of zinc in conjunction with electrolytic gels that, thanks to electrochemical processes, once connected with the reinforcement steel, lower the potential of corrosion to the reinforcement steel themselves. Thus, allowing the prolongation of corrosive events in structures which need to be repaired whilst preventing degradation, if correctly applied, in new structures.Furthermore, in such protection systems, a polymer-modified cementitious membrane is used, with superior elastic and crack bridge properties in environmental exposure temperatures of up to -20°C, thus protecting the concrete from penetration of carbon dioxide and chloride attack.Due to an in-depth laboratory study in combination with live field tests, this paper will highlight that a 2-mm thick protection layer can effectively counteract the penetration of CO2 for over 50 years, and is comparable to a concrete cover thickness of 54 mm of concrete, at a w/c ratio of 0,5. With regards to chloride attack, studies confirm that 2,5 mm of coating equals 30 mm of concrete cover at a w/c ratio of 0,452.
Cathodic protection of concrete with conductive coating anodes: 25 years of experience with projects and monitoring results
Authors: van den Hondel Anthony , van den Hondel Hans
Published: October 2018

An overview of projects with CP systems in the Netherlands is given, where during a period of 25 years conductive coating was used as an anode. Projects on bridges, viaducts, power plants, apartment and industrial buildings will be presented, with reinforced and pre-stressed concrete, and with the protected elements varying from floors to balconies, beams to abutments and cantilevers to columns. All being monitored for up to 25 years and now presented in one overview showing the possibilities of the application of these types of anode, as well as the thresholds. Measurements on a variety of constructions were carried out during 25 years and show interesting results, enlarging the knowledge on CP with conductive coatings as an anode and the effectiveness of this type of CP systems and its development in time, as determined by the depolarisation values of the system and (protective) current densities. From these measurements conclusions can be drawn and lessons can be learned regarding the use, design, installation and effectiveness of CP systems with conductive coatings as an anode.
Reliability assessment of existing bridge constructions based on results of non-destructive testing
Authors: Küttenbaum Stefan , Taffe Alexander , Braml Thomas , Maack Stefan
Published: October 2018

The non-destructive testing methods available for civil engineering (NDT-CE) enable the measurements of quantitative parameters, which realistically describe the characteristics of existing buildings. In the past, methods for quality evaluation and concepts for validation expanded into NDT-CE to improve the objectivity of measured data. Thereby, a metrological foundation was developed to collect statistically sound and structurally relevant information about the inner construction of structures without destructive interventions. More recently, the demand for recalculations of structural safety was identified. This paper summarizes a basic research study on structural analyses of bridges in combination with NDT. The aim is to use measurement data of nondestructive testing methods as stochastic quantities in static calculations. Therefore, a methodical interface between the guide to the expression of uncertainty in measurement and probabilistic approximation procedures (e.g. FORM) has been proven to be suitable. The motivation is to relate the scientific approach of the structural analysis with real information coming from existing structures and not with those found in the literature. A case study about the probabilistic bending proof of a reinforced concrete bridge with statistically verified data from ultrasonic measurements shows that the measuring results fulfil the requirements concerning precision, trueness, objectivity and reliability.
Corrosion on prestressing wires due to segregation of the injection mortar – Detection of injection defects with Ultrasonic-Echo Technique
Authors: Sodeikat Christian , Mayer Klaus , Obermeier Philipp
Published: October 2018

Unsuitable granulometry of injection mortar can promote segregation if high hydrostatic pressure impacts on the mortar for longer time during hardening. Endangered for segregation are long perpendicular prestressing tendons e.g. used in high towers due to the high hydrostatic pressure inside. The segregation causes an accumulation of water and solved ions on top of the tendons. In this area an extremely high pH-value and a very low electrochemical potential occurs. This environment is extremely corrosive and can cause wire breaks within only few months. With the Ultrasonic-Echo Technique (Flaw Detectors) it is possible to detect injection defects by using the phase shift technique.
Workability and mechanical properties of ultrafine cement based grout for structural rehabilitation: A parametric study on the partial replacement with SCMs
Authors: Shamsuddoha Md , Hüsken Götz , Schmidt Wolfram , Kühne Hans-Carsten , Baeßler Matthias
Published: October 2018

Grouting is a universal repair and strengthening technique, which is constantly used for structural remediation of concrete components, trenches, mine subsidence, dam joints, restoration of masonry structures, and geological stabilizations. Having an extremely small particle size of only few microns, ultrafine cements are ideal for grouting applications due to their superior permeability and compressive strength properties of the hardened cement paste compared to that of the less-expensive, but coarser ordinary Portland cements. Supplementary cementitious materials (SCMs) are often used to replace ultrafine cement in order to modify certain properties and to reduce costs. The aim of this experimental study is to investigate the effect of three supplementary materials: microsilica (MS), fly ash (FA), and metakaolin (MK) on the workability, and mechanical properties of an ultrafine cement based grout with a constant water-binder ratio and constant superplasticizer content. Maximum percentages of replacement with ultrafine cement were 6% by volume of cement for MS and 16% for FA, and MK. In general, results suggest that the workability is improved by addition of FA, whereas is reduced, when modified with MS and MK. The compressive strength of grout after cement replacement remains comparable to that of pure cement grout. However, there is a tendency of the MS to positively affect the compressive strength opposite to FA, whereas flexural strength is positively affected by FA. Based on the results, it is evident that grouts with Hägerman cone flow more than 500 mm and compressive strength of more than 90 MPa after 28 days can be produced.
Alternative patch repair materials for rebar corrosion damage
Authors: Jassa Primesh , Beushausen Hans , Tchetgnia Ngassam Ines
Published: October 2018

One of the most common methods adopted in the rehabilitation of corrosion-damaged concrete is the patch repair procedure. However, in practice this method has shown to often be unreliable as a consequence of the widespread occurrence of shrinkage induced cracking and poor substrate-patch adhesion leading to debonding of the patch repair. From a practical point of view, such failed repair systems essentially restore the repaired concrete back to a deteriorated state. There is a common belief that repairing concrete with specialised proprietary repair materials would guarantee durability. However, the widespread premature failure of patch repairs conducted using such materials has proven the contrary. This paper presents an understanding of the materials and issues concerning the durability and serviceability of concrete patch repairs, with the aim of identifying alternative non-structural patch repair materials for the effective repair of corrosion-damaged concrete structures. The potential patch repair materials researched were polymer-cement concrete (copolymer of vinyl acetate and ethylene with 5% cement replacement) and 60%, 80% and 100% fly ash (FA) mortar. Patch repairs were conducted on substrate moulds to test application and observe cracking/debonding occurrence. Furthermore, compressive strength, durability index, accelerated drying shrinkage, restrained shrinkage, workability and scanning electron microscopy (SEM) tests were conducted to determine the properties of the materials developed with reference to performance requirements of durable concrete repairs. It was concluded that the 60% FA and polymer-cement concrete repair materials had the best overall performance. This research established that innovative alternative repair materials such as a 60% FA or polymer-cement concrete material, can be developed for non-structural patch repairs with improved long-term performance relative to conventional materials.
Design and Construction of Ultra-Thin Continuously Reinforced Concrete (UTCRC) on N1 near Hugenote Tunnell
Authors: Bredenhann Steph , van Heerden Johan , Strauss Pieter , Joubert Phillip
Published: October 2018

In 2009, the National Route 1 Section 1 between km 56.1 and km 61.5, located North East of Paarl in the Western Cape Province of South Africa, was rehabilitated and widened. As part of the rehabilitation and widening contract the downhill truck crawler lane was constructed as an experimental pavement section. This experimental pavement section was constructed with a 50 mm thick Ultra-Thin Continuously Reinforced Concrete Pavement (UTCRCP). Early in 2010 sections of the experimental UTCRCP started to fail and consequently necessitated repair. In October 2014 a service provider was appointed for the special maintenance of the truck crawler lane on the National Route 1 Section 1. The project called for the reinstatement of the failed experimental UTCRCP with a re-engineered UTCRCP and a Enrobé à Module Élevé (EME) asphalt base layer with an Ultra-Thin Friction Course (UTFC), at various locations along the southbound (downhill) truck crawler lane. The project objective was specifically formulated to enable a long term performance comparison of both the re-engineered UTCRCP and the EME with UTFC under repeated traffic loading. The focus of this paper is the documentation and assessment of the initial pavement (structural analysis) and material design process, the construction of the UTCRCP, with cognizance of the challenges experienced during construction as well as the initial performance comparison. EME will not be discussed in this paper.
Axial stress-strain behaviour of pre-damaged square concrete column repaired with FRP jackets
Authors: Li Pengda , Zhou Yingwu , Han Ningxu , Xing Feng
Published: October 2018

This paper presents the results of an experimental study on the behaviour of pre-damaged concrete square columns that have been strengthened with carbon fibre-reinforced polymer (CFRP) wrap. Tests were conducted on 46 concrete columns involving variations of corner radius ratio, damage degree, and confinement pressure. The effect of corner radius on the main parameters of stress-strain curve for FRP strengthened pre-damaged specimens, such as compressive strength, strain capacity, initial elastic modulus, was investigated. The test results demonstrated that the efficiency of repairing damaged columns significantly depends on the corner radius ratio, the strength gain after FRP-strengthening decreases as the corner radius ratio reduces. Using those test data, new ultimate strength and ultimate strain model are proposed. The proposed models involved the effect of both corner radius and damage level, showing good agreement with the experimental results.
Basalt reinforced concrete structures for retrofitting concrete surfaces
Authors: Wolf Benjamin , Kustermann Andrea , Schuler Christian , Dauberschmidt Christoph , Bucak Ömer
Published: October 2018

Reinforced concrete facades exist since decades exposed to natural weather conditions. Thus nowadays lot of them are damaged by carbonation induced corrosion and therefor require repairing and retrofitting. The aim of this research project is to investigate the possibilities of basalt fibre reinforced concrete as repairing material and also basalt rebars as additional strengthening reinforcement. Investigations with basalt fibre reinforced mortar prisms showed best results in 3 point bending tests, tensile strength and also compressive strength using 0.3 Vol.-% basalt fibres in mixture. The mechanical properties of basalt rebars made of basalt fibre reinforced polymer were tested, showing higher values in tensile strength and Young´s Modulus than comparable steel reinforcement samples. The basalt rebar reinforced concrete samples achieved higher ultimate loads in three-point bending test compared to SRC samples. But after failure in the bonding area no residual load capacity remained. Finally basalt reinforcement bars seems to be well suited for use as retrofitting material for facade elements, but numerous properties have to be examined in further investigations.
Seismic Retrofitting of a Bridge Pier with Ultra High Performance Fibre Reinforced Concrete
Authors: Adriano Reggia , Morbi Alessandro , Plizzari Giovanni A.
Published: October 2018

The increasing number of road infrastructures needing repair and retrofit is raising the problem of how to improve seismic behaviour for all those structures for which substitution is unlikely. This work deals with the application of a retrofitting technique for Reinforced Concrete (RC) elements based on the use of Ultra High Performance Fibre Reinforced Concrete (UHPFRC). A thin layer of UHPFRC, cast around an existing RC element, can both improve its structural performance and enhance its durability against environmental actions. This kind of rehabilitation intervention may represent, in many practical cases, a cost effective solution compared with the replacement of the entire structure. The aim of this paper is the definition of a reinforcement strategy and the presentation of a 1:4 scale laboratory test of a highway bridge pier reinforced with a 30 mm layer of UHPFRC.
Case Study of Concrete Repairs on Jetty in Port Nolloth, Northern Cape
Authors: Schrecker Malan , Viljoen Duan , van der Spuy Pierre
Published: October 2018

This paper describes the rehabilitation of the jetty in Port Nolloth, Northern Cape. The history of the jetty is not 100% certain, but it is believed that the previous wooden jetty was replaced by the current concrete structure towards the late 1940’s. There were no as-built drawings of the jetty structure available. The jetty was in a deteriorated state and required a very thorough forensic investigation to determine the state of deterioration and to develop a design for the rehabilitation thereof. The forensic study, conducted by a specialist sub-contractor, included ferro-scanning (steel reinforcement number and spacing), core samples, non-destructive testing on the structure and visual inspections. From the investigation it was found that the concrete used for the jetty is generally of good quality (high strength, good compaction, and good aggregate distribution) and cover depths are in most locations in excess of 40 mm. However, after 60 years of marine exposure the structure suffers from very high chloride contamination and severe rebar corrosion damage. Previous repairs were found to generally have failed to offer any noteworthy protection to the structure. Large cracks, spalled concrete and exposed corroded steel reinforcement were evidence of the chloride contamination. A structural analysis to verify the jetty capacity was also completed and it was found that it is imperative that the original cross-sectional area of the piles is restored. The methods proposed and employed to rehabilitate the jetty were patch repair (trowel applied concrete and sprayed concrete), sectional casting of concrete (with formwork), and replacement of reinforcement. The work commenced mid-2016 and was substantially completed end of 2017.
The Rehabilitation of Structures on the National Route 10 Section 12 between Upington Km 0.0 and Nakop Km134.17
Authors: Massingue Tiago , Zietsman Bennie
Published: October 2018

National Route 10 Section 12 is situated between Upington and Nakop at the border between South Africa and Namibia in the Northern Cape Province. As part of SANRAL’s Bridge Management System, three bridges and twenty four major in-situ cast culverts were identified to be in need of rehabilitation and/or strengthening. This paper details the condition of the existing structures as well as the methods and materials used to repair and strengthen the structures to be in a safe and serviceable condition. Due to the harsh environmental conditions, as well as the remoteness of the structures, the methods and materials for repair had to be carefully considered. In this regard, special reference is made to the use of carbon fibre strips to increase the bearing capacity of the bridgeand culvert deck slabs. The method for the strengthening of the floor slabs and internal walls of a number of culverts, for which the compressive strength of the existing concrete was found to be in the order of 1.0 MPa, is also discussed.
Strengthening, rehabilitation and widening of the existing arch bridge on national route 7 over the Olifants River, South Africa
Authors: van der Spuy Pierre , Niehaus Hennie
Published: October 2018

This paper describes the rehabilitation of the existing bridge over the Olifants River. The bridge is on National Route 7 near Klawer and dates back to 1957. The defining feature of this elegant bridge is a concrete arch spanning 92.7 m. The existing bridge displayed extensive cracking, failed expansion joints and spall damage to beam soffits. Some columns showed vertical cracks while some foundations presented with horizontal cracks. The arch presented with longitudinal cracks on both the upper and lower surfaces and a previous attempt to fill the cracks proved unsuccessful, as the cracks continued to widen. This paper presents the investigations undertaken to determine the cause for the observed defects as well as the methods employed to rehabilitate the bridge. These measures include strengthening with carbon fibre, coatings, patch repair, replacement of reinforcement, replacement of expansion joints and replacement of parapets. The work commenced early 2016 and was substantially completed mid-2018.
Study on Characteristics of Tensile Strength of Concrete Considering Temperature Dependence in Mass Concrete Structures
Authors: Izumi Hiroki , Arai Juniti , Mizobuchi Toshiaki
Published: October 2018

It is important to grasp mechanical and thermal properties in order to verify the possibility of thermal cracking. In this study, for the purpose of improving the accuracy of analysis in prediction of cracking caused by thermal stress, it was investigated that the direct tensile strength and thermal properties considering temperature history inside concrete member may be applied as a design values for the analysis of prediction of cracking caused by thermal stress. From results of these experiments, in early age, the direct tensile strength under mass curing which is considered temperature history inside concrete member is higher than the splitting tensile strength under standard curing. Which is cured under water of 20°C. However, the direct tensile strength under mass curing is lower than the splitting tensile strength under standard curing after 7 days. At 28 days, the strength of former was about 20% lower than that of latter. In this study, the estimated formula on the strength development of the direct tensile strength was proposed. And the thermal expansion coefficient was estimated using measured values of strain and temperature. In this paper, it was reported that the test method of direct tensile strength considering temperature history inside concrete member was proposed and that the accuracy of analysis for the prediction of thermal cracking by using this method would be improved.
Tensile strength of carbon rovings impregnated with different materials under anodic polarization
Authors: Asgharzadeh Amir , Raupach Michael
Published: October 2018

Carbon textiles are used more and more as reinforcement in concrete structures. Due to their high durability the concrete covers can be extremely thin compared to traditional steel reinforced concrete, resulting in the possibility to build very thin elements with excellent performance. To improve the properties of the carbon textiles, the rovings are normally impregnated with different types of polymers. Additionally to the use as reinforcement, carbon textiles can also be used as anodes for cathodic protection. However, while first tests have shown, that impregnated carbon rovings are suitable to be used as CP-anodes, it is still not clear under which conditions the new types of anodes are stable or when they start to dissolve. This paper describes investigations on the influence of an anodic polarisation on the tensile strength of different types of impregnated carbon rovings.
Influence des effets dynamiques et thermiques sur l’assemblage par clouage
Authors: Goldspiegel Fabien , Michel Philippe , Blumenfeld Jean-Baptiste , Oszenda Jean-Baptiste , Mocellin Katia
Published: October 2018

L’assemblage par clouage de deux tôles d’acier est présenté au moyen d’une approche numérique et expérimentale. Un modèle de l’étape d’assemblage est réalisé et confronté aux données expérimentales pour différents paramétrages de la machine. La simulation est ensuite utilisée pour l’évaluation des phénomènes locaux observés au sein des tôles, tels que les modes de rupture et les élévations de température.
43-ème Congrès National d'Analyse Numérique, CANUM2016
Authors: Ramdani Karim
Published: October 2018

Survey articles from the 43rd CANUM - Articles de revue issus du 43-ème CANUM.
Höhergradige Mehrlingsschwangerschaften und Mehrlingsreduktion
Authors: Abel Judith Sarah , Geipel Annegret
Published: October 2018

Mehrlingsschwangerschaften gelten als Risikoschwangerschaften. Die iatrogene Mehrlingsreduktion wurde als klinische Methode in den 1980er Jahren entwickelt, um das Outcome einer höhergradigen Mehrlingsschwangerschaft zu verbessern. Seit ihrer Einführung wird sie medizinisch und ethisch kontrovers diskutiert. Eine Herausforderung auch für die Beratung der betroffenen Frau, die möglichst interdisziplinär über ihre Situation und die sich bietenden Handlungsoptionen aufgeklärt werden sollte.
Zweizeitige Geburt von Zwillingen
Authors: Boßung Verena
Published: October 2018

Experten-Interview | Die zweizeitige Geburt ist eine Option für ausgewählte dichoriale, diamniote Zwillingsschwangerschaften, um nach spontaner Frühgeburt des ersten Zwillings an der Grenze zur Überlebensfähigkeit ein höheres Gestationsalter für den zweiten Geminus zu erreichen. Im vorliegenden Fall konnten an der Klinik für Frauenheilkunde und Geburtshilfe des Universitätsklinikums Schleswig-Holstein (UKSH) Campus Lübeck beide Kinder gerettet werden.
Amyotrophe Lateralsklerose
Authors: Weishaupt Jochen H. , Dorst Johannes , Ludolph Albert C.
Published: October 2018

Das Bild der Amyotrophen Lateralsklerose (ALS) hat sich in den vergangenen Jahren durch neue Erkenntnisse im Hinblick auf Phänotyp und Verlauf, Neuropathologie
und Genetik deutlich gewandelt. Zudem werden aktuell innovative verlaufsmodifizierende Therapieansätzen sichtbar.
Doxercalciferol Alleviates Bone Deteriorations and Cartilage
Degeneration in Aging Mice
Authors: Li Jian , Li Nan , Yan Shuangtong , Liu Minyan , Sun Banruo , Lu Yanhui , Shao Yinghong
Published: October 2018

Background Age-related bone deteriorations are the common endocrine
disorders in the elderly population, leading to an increased risk of fractures.
Therefore, effective treatment strategies provide a way to prevent bone loss and
improve the quality of life in the elderly population. The present study aimed
to investigate the anti-osteoporotic effects of doxercalciferol (DOX) in aging
mice.

Methods Bone metabolism-related markers were measured by ELISA assay. The
expression of bone formation and resorption-related genes was performed by
RT-qPCR analysis. Hematoxylin and eosin (H&E) and Safranin O staining
were performed to analyze the trabecular bone and cartilage degeneration.

Results Aging resulted in urine ca2+ excretion, a decrease in
bone ca2+ content and reduction of biomechanical strength in mice. We
also found that the level of PTH was increased in aging mice, while DOX
administration markedly down-regulated serum PTH in aging mice. H&E and
Safranin O staining showed that DOX protected against aging-induced bone loss
and cartilage regeneration in the tibia from aging mice. Furthermore, DOX
treatment resulted in an increase in Runx2, osterix and Col1a1 mRNA expression
and a decrease in Ctsk, MMP-9 and CAII mRNA expression in the tibia from aging
mice.

Conclusion These findings indicated that DOX had a beneficial effect on
age-related bone deteriorations in aging mice by promoting osteoblast activity
and cartilage regeneration and inhibiting osteoclast-specific genes
expression.
Changes in Palm Temperature as Predictor of Long-term Cure of Sympathicotomy for Palmar hyperhidrosis?
Authors: Liu Gaoli , Kang Ganjun , Xie Songping , Hu Haifeng , Huang Jie
Published: October 2018

Objectives To investigate the long-term relationship between intraoperative temperature changes of the palm, treatment effects and compensatory hyperhidrosis (CH).

Methods We retrospectively analyzed the data of 41 patients with palmar hyperhidrosis who underwent bilateral endoscopic sympathicotomy 3 to 6 years ago. Before and after the operation, changes in ipsilateral palm temperature were monitored and recorded to evaluate the curative effect of the sympathicotomy.

Results All operations were performed successfully. Concerning cure, there was no statistically significant difference between patients with different maximum temperature (Tmax) values (p = 0.455). There was a very weak correlation between postoperative palm temperature (34.309 ± 1.377°C) (p = 0.049; correlation coefficient − 0.218). The T3 + T4 sympathicotomies had a higher Tmax (p = 0.000). The incidence and degree of CH had no relationship with Tmax in the left (p = 0.266 and p = 0.168, respectively) or the right hand (p = 0.640 and p = 0.824, respectively).

Conclusions Temperature change has a relationship with surgery, but it cannot directly predict the long-term curative effect of a sympathicotomy or the occurrence of CH. Additional studies are required.
Extradural Characteristics of the Origins of Lumbosacral Nerve Roots
Authors: Matejcik Viktor , Kuruc Roman , Líška Ján , Steno Juraj , Haviarova Zora
Published: October 2018

Background and Study Aims A great number of unsuccessful intervertebral herniated disk surgeries in the lumbosacral region have highlighted the importance of a comprehensive knowledge of the different types of nerve root anomalies. That knowledge gained by anatomical studies (and intraoperative findings) might contribute to better results. In our study we focused on intraspinal extradural lumbosacral nerve root anomalies and their possible role in radiculopathy.

Material and Methods The study was performed on 43 cadavers within 24 hours after death (32 men and 11 women). Bodies were dissected in the prone position, and a laminectomy exposed the entire spinal canal for the bilateral examination of each spinal nerve root from its origin to its exit through the intervertebral foramen or sacral hiatus. Uncommon extradural features in the lumbosacral region were pursued and documented. The spinal dural sac was also opened, aimed at recognizing the normotyped, prefixed, or postfixed type of plexus.

Results A total of 20.93% of anomalies of extradural lumbosacral nerve root origins were observed, with the normotyped plexus prevailing. We observed atypical spacing of exits of lumbosacral roots (four cases), two roots leaving one intervertebral foramen (one case), extradural anastomoses (two cases), and missing extradural nerve root courses (two cases). The results were differentiated according to the normotyped, prefixed, or postfixed plexus type.

Conclusion Results of similar studies dealing with anomalies of lumbosacral nerve roots were aimed at improving the results of herniated disk surgeries because ∼ 10% of misdiagnoses are related to ignorance of anatomical variability. Our observations may help explain the differences between the clinical picture and generally accepted anatomical standards.
Implementation and Impact of a Maternal–Fetal Medicine Telemedicine Program
Authors: Leighton Cassandra , Conroy Molly , Bilderback Andrew , Kalocay Wendy , Henderson James K. , Simhan Hyagriv N.
Published: October 2018

Objective The increase in maternal morbidity has resulted in higher need for maternal–fetal medicine (MFM) subspecialty care. To meet the rising demand, particularly in rural areas, the use of MFM telemedicine services has increased. This study describes the structure, implementation, and patient and child health outcomes associated with a large health system's MFM telemedicine program.

Study Design Observational electronic health record data are used to compare maternal and childbirth outcomes between patients receiving care via telemedicine or in-person visits through regression analysis. Average patient time and resources saved are calculated, and patient satisfaction scores are reported.

Results The telemedicine patients experienced similar outcomes to the in-person group, indicating that MFM telemedicine can serve as an effective substitute for in-person care. MFM telemedicine patients saved $90.28 per consult in travel and work-related expenses. An overwhelming majority of MFM telemedicine patients were satisfied with their visit and indicated that they would be interested in receiving care via telemedicine in the future.

Conclusion The results indicate that the patients may benefit financially and experience similar outcomes when telemedicine programs are appropriately designed to eliminate access barriers and provide high-quality care.