New publication

März 3, 2022

T. B. Mrohs, O. Weichold
Multivalent Allylammonium-Based Cross-Linkers for the Synthesis of Homogeneous, Highly Swelling Diallyldimethylammonium Chloride Hydrogels
Gels 2022, 8, 100 (open access)

New doctoral student

Januar 19, 2022

Since January, Nils Münstermann has been supporting the research group in the area of bio-based building materials and is developing swellable chitosan derivatives for concrete and agricultural applications.

Lecture announcement

Januar 4, 2022

O. Weichold
Alkaline hydrogels – multifunctional materials for concrete rehabilitation – International Congress on Polymers in Concrete (IPCIC 2022)

POSTPONED TO 2023

Lecture announcement

Januar 3, 2022

O. Weichold
High-alkaline hydrogels - the Swiss Army Knives of restoration
NuBau – 5. Tagung Nutzerorientierte Bausanierung, Weimar.

POSTPONED TO 2023

New publication

Dezember 20, 2021

M. Brenner, O. Weichold
Poultry Feather Waste as Bio-Based Cross-Linking Additive for Ethylene Propylene Diene Rubber
Polymers 2021, 13(22), 3908 (open access)

Master thesis completed

Dezember 8, 2021

Congratulations to Nils Münstermann on the successful completion of his master's thesis entitled "Synthesis and properties of superabsorbents based on chitosan hydrogels" in the Chemistry program!
The thesis originated in the ongoing project Biosuperabsorbers.

Front page

September 15, 2021

The publication Alkaline hydrogels as ion-conducting coupling material for electrochemical chloride extraction by Andre Jung in Mater. Corr. has made it to the cover of volume 72 issue 9!
Click here for the Cover→

New publication

August 10, 2021

P. B. Sassmann, O. Weichold
Synergistic effects in cross-linked blends of ion-conducting PEO-/PPO-based unsaturated polyesters
Ionics 2021, 27, 3857–3867 (open access)

New project: Bio-based glazes and adhesives for wood

Juli 20, 2021

A new project focusing on bio-based building materials will start on 1.10.2021. Based on chitosan, we are developing glazes and adhesives for wood together with two industrial partners. The project is supervised by Tobias Boehnke.

Lecture

Juli 14, 2021

Report from the ongoing project Rissinjektion:

O. Weichold
Acrylic-free two-component gels for crack injection
7. Kolloquium „Erhaltung von Bauwerken“, Technische Akademie Esslingen, 14.7.2021, Ostfildern

Lecture

Juli 14, 2021

Report from the completed project Chloride extraction with gel:

O. Weichold
Alkaline hydrogels as coupling material for electrochemical chloride extraction
7. Kolloquium „Erhaltung von Bauwerken“, Technische Akademie Esslingen, 14.7.2021, Ostfildern

New publication

Mai 11, 2021

A. Jung, A. Faulhaber, O. Weichold
Alkaline hydrogels as ion-conducting coupling material for electrochemical chloride extraction
Matter. Corr. 2021, 72, 1448–1455 (open access)

A publication from the completed ZIM project "Chloride extraction with gel".

Lecture

März 18, 2021

O. Weichold
Self-extinguishing wood-fibre boards using waste poultry-feather hydrolysates
1^st International Conference on Science Technology & Innovation, 19.3.2021, Chiang Mai, Thailand

Lecture

März 16, 2021

Report from the completed project Chloride extraction with hydrogels:

O. Weichold
Electrochemical Chloride Extraction using diallyldimethylammonium hydroxide based hydrogels as electrolytes
3^rd International Conference on the Chemistry of Construction Materials, 17.3.2021, Karlsruhe

Got up to speed

März 12, 2021

For the reproducible and high-quality production of test specimens and samples, e.g. from our biobased materials, we have procured a Stepcraft M-1000 CNC milling machine with a working range of 679 × 1044 mm². Contact person is Tobias Boehnke.

Front page

März 10, 2021

The publication Protein Hydrolysates from Biogenic Waste as an Ecological Flame Retarder and Binder for Fiberboards von Markus Brenner hat es auf die Titelseite der Ausgabe 5 Band 50 geschafft! Hier geht es zum Cover→ 

New project: Biosuperabsorber

März 3, 2021

Retroactive to 1.1., we were approved for a project to develop water-swellable materials based on renewable raw materials. In cooperation with industrial partners, the relationship between composition and properties is being clarified, capacities for scale-up are being built up and suitable prototypes are being tested in end applications. The project is supervised by Tobias Boehnke.

New project: recycled foams

März 3, 2021

Retroactive to 1.11., we were granted a project for the development of mechanically stable foams. The project is based on the materials described in Appl. Sci. 2020. In addition, the effect of fillers made from recycled materials is being tested. The project is supervised by Fabian Weitenhagen.

New employee

Dezember 22, 2020

Since December, Fabian Weitenhagen has been supporting the working group in the area of bio-based building materials and is developing the initial work on polycondensation resins (Appl. Sci. 2020) further.

New publication

Dezember 18, 2020

M. Brenner, O. Weichold
Protein Hydrolysates from Biogenic Waste as an Ecological Flame Retarder and Binder for Fiberboards
ACS Omega 2020, 5, 32227 (open access).

Publication

Oktober 6, 2020

A. Jung, M. B. Endres, O. Weichold
Polymers 2020
To the article→

Influence of Environmental Factors on the Swelling Capacities of Superabsorbent Polymers Used in Concrete

ABSTRACT: Superabsorbent polymers (SAP) are of major interest as materials to control the cement hydration process. The swelling behavior of the SAPs significantly influences the performance of the resulting concrete by slowly releasing polymer-bound water in order to maintain a consistent w/c value. A round-robin test conducted by the RILEM Technical Committee 260-RSC showed that the same batch of polymer can lead to large deviations in concrete performance and this was assumed to originate in di
erent storage conditions of the SAP. In this contribution the change in the performance of two SAPs, a crosslinked poly(acrylate) and a crosslinked poly(acrylate-co-acrylamide), was assessed after ageing in standard climate, at 50
°C, and under UV irradiation. During storage in standard climate or 50 °C, ageing led to dehydration of the SAP, and this subsequently led to a higher water uptake during swelling. By contrast, UV irradiation reduced the water uptake, most likely as a result of photo-crosslinking. Dynamic water vapor sorption experiments indicated a strong dependence of the water uptake on both the ambient humidity and the temperature. As a result, cement mixtures containing SAP must be calculated on the dry mass of the SAP rather than the actual weight on site. A standard procedure of how to pack and handle SAP to be used in concrete is also provided.

Bachelor thesis

September 4, 2020

Denis Clou

Congratulations on the successful completion of the bachelor thesis
Geflügelfedern als biobasierter Füllstoff in Elastomerlagern
Use of poultry feathers as a bio-based filler in elastomer bearings

Bachelor thesis

September 3, 2020

Marvin Oomen

Congratulations on the successful completion of the bachelor thesis
Chitosanbasierte Interpolyelektrolytkomplexe zur Oberflächenversiegelung
Chitosan-based interpolyelectrolyte complexes for surface sealing

Publication

Mai 5, 2020

M. Brenner, C. Popescu, O. Weichold
Appl. Sci. 2020
To the article→

Anti-Frothing Effect of Poultry Feathers in Bio-Based, Polycondensation-Type Thermoset Composites

ABSTRACT: The formation of polycondensation-type thermoset resins from natural reactants such as citric and glutaric acid, as well as 1,3-propanediol and glycerol, was studied. Monitoring the mass loss by thermogravimetric analysis (TGA) allowed the rate constants of the esterification to be calculated, which were in the order of 7·10−5 s−1 for glutaric acid and approximately twice as high for citric acid. However, the combination citric acid/glycerol was previously reported to froth up at high conversions, giving rise to foams, which makes the preparation of compact engineering composites challenging. In light of this, we observed that shredded poultry feathers not only increased the conversion and the reaction rate of the combination citric acid/glycerol, but increasing the amount of feathers continuously decreased the number of visible bubbles. The addition of 20 wt% of feathers completely prevented the previously reported frothing and gave rise to compact materials that were macroscopically free of defects. Besides this, the addition of feathers also improved the fire-retardant properties. The tensile properties of the first specimens are still rather low (σ = 11.6 N/mm2, E = 750 N/mm2), but the addition of poultry feathers opens a new path for green thermoset resins.

Master thesis

Februar 3, 2020

Tim Mrohs

Congratulations on the successful completion of the Master's thesis
Synthese von vernetzten Copolymerelektrolytgelen auf Basis von Diallyldimethylammoniumchlorid und -hydroxid
Synthesis of crosslinked copolymer electrolyte gels based on diallyldimethylammonium chloride and -hydroxide

Lecture

Oktober 1, 2019

O. Weichold, P. B. Sassmann

Jahrestagung der GDCh-Fachgruppe Bauchemie, 1.10.2019, Aachen

Numerical structural analysis for the in silico design of advanced hybrid materials

ABSTRACT:
Moderne Hochleistungsmaterialien erhalten ihre außergewöhnlichen
Eigenschaften aus dem Zusammenspiel einzelner Komponenten. Aus
mechanischer Sicht ergeben sich jedoch Probleme bei der Bestimmung des
makroskopischen Materialverhaltens. Ziel ist demnach die Ermittlung des
Materialverhaltens durch numerische Simulation am Beispiel eines
polymergetränkten Betonkörpers.

Lecture

Oktober 1, 2019

M. Brenner

Jahrestagung der GDCh-Fachgruppe Bauchemie, 1.10.2019, Aachen

Use of feather keratin as fire protection impregnation for wood and as non-combustible thermal insulation material

ABSTRACT:
Es werden neue Verwendungsmöglichkeiten für Federn gezeigt, da diese
als biogener Reststoff in großen Mengen anfallen. Dabei ist die
Verbesserung der Brandeigenschaften ein zentraler Punkt. Die Federn
werden einerseits zu einer nicht brennbaren Wärmedämmplatte verarbeitet.
Außerdem werden keratinhaltige Lösungen zur Behandlung von
Holzwerkstoffen genutzt um gezielt die Brennbarkeit zu verringern und
das Glimmverhalten zu verbessern.

Bachelor thesis

August 13, 2019

Kaja Kensmann

Congratulations on the successful completion of the bachelor thesis
Thermoplastische Verarbeitung von Federn mit einem polymerisierbaren Weichmachersystem
Thermoplastic treatment of feathers with a polymerizable plasticizer system

Bachelor thesis

August 5, 2019

Sarah Weides

Congratulations on the successful completion of the bachelor thesis
Synthese und elektrochemische Charakterisierung von Oligoethylenglykol-modifizierten 4,4′-Bipyridinen
Synthesis and electrochemical behaviour of oligoethyleneglycol-modified 4,4′ bipyridines

Lecture

Juni 3, 2019

O. Weichold

European Polymer Congress, 13. Juni 2019, Kreta

Fighting fire with feathers – transforming natural waste into flame-retardant materials

ABSTRACT:
Keratin is a natural fibre protein widely found in the animal kingdom,
where it is the basis of e. g. wool and hair, horns, scales, and
feathers. Besides its broad spectrum of mechanical properties, keratin
is particularly characterized by its poor flammability and even
self-extinguishing behaviour. Most approaches which use keratin as a
chemical feedstock require a solubilisation step, and this can be
accomplished by either alkaline hydrolysis or reduction of the
disulphide bridges. We have refined the latter to be more convenient and
economical, but more importantly to produce two kreatin fractions,
which were both found to be valuable intermediates in producing
flame-retarding materials. The first fraction consists of water-soluble
protein hydrolysates, which can be used as impregnation for particle and
fibre boards. The second fraction is a gel, which can be transformed
into foamed boards. These materials match commercial EPS/XPS boards in
terms of their thermal conductivities, but will not ignite or burn when
subjected to an open flame. The contribution will present our latest
results on the preparation and application of these two fractions.

Publication

Januar 16, 2019

T. Juraschek, O. Weichold
Concrete 2019, 5, 168–171.

Electrochromy for the visualisation of small amounts of electricity

ABSTRACT:
Ein Nachteil aktueller Korrosions-Monitoringsysteme ist die
Verfügbarkeit geeigneter Auslesegeräte zur Prognose der Lebensdauer der
überwachten Strukturen. Vor Ort installierte, wartungsfreie und einfach
abzulesende Einheiten wären für den Einsatz von Vorteil. Vor diesem
Hintergrund wurde ein Bauteil entwickelt, das in der Lage ist, kleine
Strommengen auf Basis der Elektrochromie zu visualisieren. Ziel ist es
in erster Linie, Korrosionsströme zu erfassen und visuell entsprechend
darzustellen. In dem Beitrag werden der Aufbau des Bauteils, seine
elektrochemische Charakterisierung und die Visualisierung von
Korrosionsströmen unter Laborbedingungen sowie an real korrodierenden
Stahlbetonprüfkörpern beschrieben.

Publication

Januar 16, 2019

C. Morales Cruz, Oliver Weichold, H.-J. Kocks
Concrete 2019, 5, 162–167.

FOULPROTECT - on the problem of fouling in seawater structures

ABSTRACT:
Im Rahmen des Verbundprojekts FOULPROTECT „Bewuchsschutz und Vermeidung
von Biokorrosion in der Maritimen Technik“ wurde am Institut für
Bauforschung der RWTH Aachen University (ibac) in Zusammenarbeit mit den
Firmen Salzgitter Mannesmann Line Pipe GmbH (SMLP) und LimnoMar eine
mineralische Ummantelung mit erhöhtem mechanischen Widerstand für
Stahlkonstruktionen im Meerwasserbereich entwickelt. Die Eignung
verschiedener kommerziell verfügbarer Werktrockenmörtel als
Schutzschicht wurde am Beispiel von Stahlrohren für Gründungsstrukturen
von Offshore-Windkraftanlagen getestet. Dazu wurden die Frisch- und
Festmörtelkennwerte bestimmt sowie Dauerhaftigkeitsuntersuchungen in
Laborversuchen unter realen Bedingungen (Luft- und Meerwasserlagerung)
durchgeführt. Der Aufwuchs (Biofouling) auf der Mörtelumhüllung bei
einer Meerwasserlagerung konnte bei keinem der untersuchten Materialien
verhindert werden, aber fluoreszenzmikroskopische Untersuchungen zeigten
weder Mikro- noch Makrobesiedlungen unterhalb der Mörteloberfläche.
Zwischen den einzelnen Materialien wurden deutliche Unterschiede bei der
Rissanzahl der ausgelagerten Proben festgestellt. Unter
Berücksichtigung aller Untersuchungen weisen hochfeste Mörtelmischungen
das größte Potenzial auf, abrasiven Einwirkungen und inneren
Sprengdrücken dauerhaft standzuhalten.

Publication

Januar 14, 2019

P. B. Sassmann, O. Weichold
Ionics 2019
To the article→

Preparation
and characterisation of ion-conductive unsaturated polyester resins for
the on-site production of resistivity sensors

ABSTRACT:
Ion-conductive unsaturated polyesters were synthesised from
poly(ethylene oxide) and maleic anhydride for use in the development of
improved methods for the structural-health monitoring of infrastructural
buildings. The unsaturated polyesters (UP) were cross-linked with
styrene using a redox initiator in the presence of LiClO4.
Electrochemical impedance-spectroscopy was used to study the effects of
initiator and styrene concentration as well as the EO:Li+ ratio.
Increasing the initiator or styrene content results in an increased
resistivity of the final materials. Cross-linking with styrene does not
appear to cause microphase separation into pure UP and polystyrene
phases, since the resulting resistivities are significantly lower than
predicted by the rule of mixtures. For all temperatures under
investigation (0 °C to 60 °C), the lowest resistivities were found for a
EO:Li+ ratio of 50 (400 Ω·m at 22 °C), which is in accordance with
previous findings. The electrical properties of the present materials
are determined by diffusion controlled process in such a way
polarisation prevails at high temperatures. In a proof of principle
experiment, one selected UP formulation was injected into drill holes in
concrete and cured at different temperatures and moisture conditions.
This system reliably monitors the resistivity against an embedded
reference electrode.

Publication

November 20, 2018

M. B. Endres, O. Weichold
Carbohydrate Polym. 2018
To the article→

Sorption-active transparent films based on chitosan

ABSTRACT:
In this paper we describe the preparation of alkanoic acid-based
aqueous chitosan solutions, which show no sign of acid-catalysed
depolymerisation over time – something commonly accompanying other
preparation methods. Longer chitosan chains have previously been shown
to exhibit more advantageous biological activities, and constant
viscosities are essential for consistent quality in biomedical
applications. Avoiding acid-catalysed depolymerisation requires careful
control of the stoichiometry between the free amino groups of chitosan
and the appropriate solubilising acid. Acetic and butyric acid are both
suitable solubilising agents, but chitosan butyrate exhibits lower
solution viscosities due to a combined electric and steric shielding of
the chains.
These solutions dry into clear transparent films that
remain fully water soluble and absorb up to 70 wt% of water from 90 %-RH
vapour phase at 25 °C. The absorption follows simple first-order
kinetics and the rate constants increase with increasing humidity up to
approx. 71 %-RH, where a metastable chitosan trihydrate salt appears to
be formed. Desorption is slightly faster, but more complex, as it
exhibits two distinct first-order processes. In addition, films prepared
in this way are thermally more stable than the usual chitosan
hydrochloride.

Front page

Oktober 16, 2018

A. Jung, O. Weichold

Andre's publication "Preparation and characterisation of highly alkaline hydrogels for the re-alkalisation of carbonated cementitious materials" was selected by Soft Matter for the cover design.

Bachelor thesis

Oktober 3, 2018

Lutz Burow

Congratulations on the successful completion of the bachelor thesis
Untersuchung der thermischen Eigenschaften von mit Keratin imprägnierten Holzspänen
Thermal properties of keratin-impregnated chipped wood

Lecture

September 11, 2018

O. Weichold
IBAUSIL, Weimar, 12.–14. September 2018

Polymere und Beton – Eine wilde Ehe mit Potential

Bachelor thesis

September 3, 2018

Lena Schmitz

Congratulations on the successful completion of the bachelor thesis
Vernetzte Polyethylenglycole als Träger für ionenleitfähige Filme
Cross-linked polyethylene glycol matrix for ion-conductive films

Master thesis

August 14, 2018

Jan Tenbusch

This master's thesis was carried out externally in cooperation with Henkel. Congratulations on the successful completion.

Bachelor thesis

August 7, 2018

Kathrin Dahm

Congratulations on the successful completion of the bachelor thesis
Synthese ethoxylierter und propoxylierter Styrole zur Herstellung ionisch leitfähiger Polyester
Synthesis of ethoxylated and propoxylated styrene for the formation of ionic conductive polyesters

Bachelor thesis

Juli 3, 2018

Julia Littke

Congratulations on the successful completion of the bachelor thesis
Synthese ungesättigter Polyester auf Basis von PPO
Synthesis of unsaturated polyesters based on PPO

Publication

Mai 9, 2018

A. Jung, O. Weichold
Soft Matter. 2018
To the article→

Preparation and characterisation of highly alkaline hydrogels for the re-alkalisation of carbonated cementitious materials

ABSTRACT:
Highly alkaline hydrogels that allow the restoration of alkaline buffer
in cementitious materials can be obtained from diallyldimethylammonium
hydroxide. The latter must be prepared in dilute solutions and
polymerised at ambient temperatures in order to avoid decomposition.
Using methacrylamide as a neutral co-monomer capable of forming hydrogen
bonds, the rheological properties of the gels can be adjusted over a
wide range; e.g. the viscosity increases a thousandfold from 0.35 Pa·s
to 4350 Pa·s by using 10 mol% methacrylamide. For the proof of principle
experiments, gels with 9 mol% methacrylamide were used, which contain
approx. 1.6 mol hydroxide ions per kg gel. Ion exchange between this and
a neutral chloride containing gel provided an apparent diffusion
coefficient of 4.12·10−7 m2 s−1 for the hydroxide ions and confirmed the
transport of chloride ions into the alkaline gel. The re-alkalisation
was tested on fully carbonated mortar prisms made from Portland cement.
Re-alkalisation of the mortar was confirmed by the phenolphthalein test
according to DIN EN 14630:2007-01 and by a control experiment with pure
calcium carbonate using IR spectroscopy.

Bachelor thesis

April 3, 2018

Jan Bandowski

Congratulations on the successful completion of the bachelor thesis
Entwicklung von Steuerungsmechanismen zur Regulierung der viskosen Eigenschaften eines PolyDADMAC-Gels
Development of mechanisms to control the viscous properties of PolyDADMAC gels
The work was carried out together with the FH Aachen, Department of Chemistry and Biotechnology.

Publication

Oktober 3, 2017

T. Juraschek, O. Weichold
J. Phys. Org. Chem. 2017; e3739
To the article→

Development
of an electrochromic device triggered by the macrocell current in
chloride-induced corrosion of steel-reinforced concrete

ABSTRACT:
This article presents the development and characterisation of an
electrochromic device and its application to detect steel corrosion in
reinforced concrete. Steel corrosion inflicts an enormous annual
economic damage, which could be reduced by the installation of
appropriate monitoring devices. These should be simple, reliable, long
lasting, and should not require service or maintenance. The present
electrochromic device is constructed in such a way that it uses the
macrocell current in an active, chloride‐induced corrosion element as
power supply to trigger the colour change. This way, the system stays
inactive until corrosion occurs. The device consists of diheptyl
viologen in a liquid polymer electrolyte made from LiClO4 and
poly(ethylene glycol) with Mw = 400 g mol−1. The addition of viologen
lowers the resistance but causes no further changes in the
electrochemical properties of the polymer electrolyte. Impedance spectra
indicate ion transport rather than capacitance effects to dominate the
electrochemical properties. Experiments using direct current in the
microampere range show electrochromic switching times of several
minutes, which is sufficient for the intended monitoring application.

Lecture

September 19, 2017

M. Brenner
Tagung der GDCh-Fachgruppe Bauchemie, Weimar, 19. September 2017

Functionalisation of fibre surfaces for textile-reinforced elastomers

ABSTRACT: Decisive for the load-bearing capacity of textile-reinforced structures is the performance of the interface. In cementitious systems, this is usually achieved by form-fit joints (e.g. carbon textiles impregnated with epoxy resin and sanded). In polymeric materials, such a stiff bond is often undesirable due to the smaller modulus of elasticity, and in elastomers it is even counterproductive. The presentation reports on an investigation into the targeted chemical functionalisation of glass, basalt and carbon fibres to reinforce chloroprene and EPDM. The fibres were modified with bis[3-(triethoxysilyl)propyl]tetrasulphide (TESPT) and 3-(mercaptopropyl)trimethoxysilane (3-MPTMS). For application, the substances were mixed with dissolved elastomer and applied to the fibres by hand. The modified fibres were then vulcanised into the elastomer in a specially manufactured mould and the fibre-matrix adhesion was tested in a pull-out test. With glass and basalt fibres, an improvement in the bond of up to approx. 100 % could be achieved; with the modification of carbon fibres, the bond can be improved by approx. 50 %.

Lecture

September 19, 2017

O. Weichold

Tagung der GDCh-Fachgruppe Bauchemie, Weimar, 19. September 2017

Polymere im Bauwesen – weiche Materialien in einer harten Welt

Publication

September 4, 2017

O. Weichold, U. Antons
J. Infrastruct. Syst. 2017, 23, 04017010
To the article→

Assessing the Performance of Hydrophobing Agents on Concrete using Non-Destructive Single-Sided Nuclear Magnetic Resonance

ABSTRACT:
Single-sided nuclear magnetic resonance is a nondestructive analytical
technique by which the ingress behavior of hydrophobing agents as well
as the properties and performance of the resulting hydrophobic layers
can be assessed quantitatively. The method is used to compare the
behavior of two low-molecular-weight hydrophobing agents,
n-octyltriethoxysilane and i-butyltriethoxysilane, on concrete and to
assess the properties of the resulting hydrophobic layers. For the octyl
derivative, ingress appears to be a simple transport process without
pronounced polycondensation in the liquid phase or reaction with the
pore walls because the detectable amount stays rather constant during
the first day of observation. In addition, the thickness of the
resulting hydrophobic layer correlates well with the endpoint of the
transport process. In contrast, the detectable amount of the butyl
derivative is reduced to half during the first 18 h, indicating either
substantial polycondensation or anchoring to the pore walls, and the
hydrophobic layer is approximately 25% thicker than indicated by the
ingress profiles. The different behavior could originate in differences
in the molecular structure, particularly the steric demand of the alkyl
substituents, although this requires a more detailed study. Both
compounds proved to be excellent hydrophobing agents since the layers
were found to be impermeable when kept in a shallow water bath
(unidirectional transport through the layer) for more than 1 year. The
results demonstrate that single-sided nuclear magnetic resonance is an
excellent nondestructive tool for quality assurance when applying such
protective layers.

Lecture

September 3, 2017

T. Juraschek
EUROCORR 2017, Prag, 3. September 2017

Chemical, Non-Electronic Corrosion Indication Systems

ABSTRACT:
Corrosion of the steel reinforcement in concrete causes an enormous
economic damage. In particular, chloride-induced macroelement corrosion
of the reinforcement is one of the bottlenecks in the service life time
design of a majority of infrastructure buildings with a significant
exposition to chloride. Corrosion monitoring offers a possibility to
detect the onset of corrosion events and start independent restoration
actions at a point, where costs can be kept at a minimum.
The
presentation focusses on the testing procedure and verification of the
prototype, under conditions simulating real-life corrosion events. Color
change is not observed when applying zero-load currents, but occurs
within minutes after raising either the potential or current to levels
typical for corrosion events. The color change is persistent even after
turning the power source off. We applied potential controlled current
profiles as well as voltage controlled current profiles to the device,
also with respect to peak current profiles to show the response of the
system under realistic circumstances. Also, we investigate the influence
of zero-load current and voltage events during the passive state of the
reinforcement steel after passivation. Furthermore, experiments on
reinforcement steel and reinforced concrete samples are shown as a
proof-of-principle experiment.

Career

Juli 1, 2017

Our alumna Elena Heß starts a job at HeidelbergCement on 1 July 2017.

Publication

Juni 7, 2017

R. Schulte Holthausen, O. Weichold
J. Infrastruct. Syst. 2017, 23, B4016006.
To the article→

Non-destructive Evaluation of Thermal Damage in Concrete by Single-Sided Nuclear Magnetic Resonance

ABSTRACT:
A new technology to coat concrete with coherent layers of glass by
flame-spraying is currently developed at the Institutes of Building
Materials Research and Mineral Engineering of RWTH Aachen University in
Germany through a joint program. A major factor influencing the pull-off
strength of the flame-sprayed glass coating is thermally induced damage
in the underlying concrete substrate. In this article, the authors
present a nondestructive test method using single-sided 1H nuclear
magnetic resonance (NMR) to evaluate the thermally induced damage in
concrete specimens. The particular NMR device used in this project
primarily detects water and can qualitatively assess the water content
as well as the relative size of water-filled voids such as pores and
cracks. To do so, the specimens are water saturated and subsequently
analyzed by NMR. Changes in the NMR-signal are interpreted in terms of
change in porosity and development of cracks inside the cement stone as a
function of depth from the concrete surface.

Bachelor thesis

Juni 3, 2017

Iva Rroshi

Congratulations on the successful completion of the bachelor thesis
Zur Untersuchung der Genauigkeit bei der Ermittlung des Bindemittelgehalts an Betonproben durch Methoden der chemischen Analytik
Investigation
of the accuracy conerning the determination of the binder content of
concrete samples by methods of analytical chemistry

Master thesis

März 3, 2017

Markus Brenner

Congratulations on the successful completion of the Master's thesis
Funktionalisierung von Faseroberflächen für textilbewehrte Elastomerlager
Functionalization of Fiber Surfaces for Textile-Reinforced Elastomeric Bearings

Lecture

Januar 25, 2017

O. Weichold
Seminar „Stadtstraßen / Ortsdurchfahrten“ des VSVI Niedersachsen e.V., ABZ Mellendorf, 25. Januar 2017

CARPET – Konfektionierter, aufrollbarer, polymerbasierter Straßenbelag

Konferenzbeitrag

Januar 10, 2017

T. Juraschek, O. Weichold
6th International Conference on Concrete Repair (Concrete Solutions), Thessaloniki, 2017, S. 207–211.

In-situ methods of detecting steel corrosion using permanent and non-electronic systems

ABSTRACT:
Current systems for detecting corrosion of the reinforcement in
concrete are realized via highly specialized systems that are
commercially not available. Thus, these systems require complete
technical support by the installing company. This report shows a cheap,
efficient, independent, and reliable method to detect corrosion events
in concrete. The detection system is based on an electrochromic device,
which changes its colour upon the change of electrochemical potential
caused by the corrosion process. The device is realized by a
layer-by-layer setup of a transparent electrode, e. g. indium-doped tin
oxide (ITO), followed by an electrochromic layer. The system is closed
by a metal counter electrode. The electrochromic layer can consist of an
electrochromic compound in a conducting polymer system. By connecting
such elements to a series of sensors, e. g. an anode ladder, it is
possible to monitor the corrosion progress and to verify the service
life design of a structure.

Konferenzbeitrag

Januar 10, 2017

P. B. Sassmann, O. Weichold
6th International Conference on Concrete Repair (Concrete Solutions), Thessaloniki, 2017, S. 235–238.

Development
of Electrically Conductive Resins for the On-Site Fabrication of
Sensors for Corrosion Detection and Risk Assessment in Reinforced
Concrete

ABSTRACT: Assessing the risk of corrosion in
steel-reinforced concrete can be accomplished using different types of
sensors such as anode ladders or multi-ring electrodes. The former are
unsuitable for retrofit installations, while the latter require the use
of embedding mortars to achieve conductive connections with the
surrounding concrete. However, the porosity of the embedding mortar
differs from that of the concrete and the retrofitting action introduces
additional moisture. This interferes with resistivity and/or potential
measurements and makes interpretations of the actual situation
problematic. To circumvent these disadvantages, we have developed a
liquid reactive polymer resin with high electrical conductivity that can
be used to fabricate sensors directly inside drill holes. The mixture
solidifies in a short time and its adhesive properties provide an
excellent conductive connection to the concrete walls. The resin
contains no water so that reliable values can be obtained immediately
after solidification. By changing the additives both resistivity and
potential sensors can be obtained. The mixture is cheap so that large
sensor networks can be installed at reasonable costs. Such networks are
ideal for the precise localization of corrosion events and more
importantly for risk assessment in steel-reinforced structures.

Lecture

Dezember 2, 2016

O. Weichold
nuBau – 3. Tagung Nutzerorientierte Bausanierung, Weimar, 30. November – 1. Dezember 2016

Neue Methoden zur Auswertung von Sw-ρ-Beziehungen

ABSTRACT:
Der spezifische elektrische Widerstand des Betons wird häufig
herangezogen, um Aussagen über die Dauerhaftigkeit von
Stahlbetonbauwerken zu treffen. Das Ziel der vorgestellten
Untersuchungen besteht darin, Wassergehalt-Widerstandsbeziehungen in
Abhängigkeit von relevanten Strukturparameten des Betons zu
charakterisieren. Hierzu wurde ein Ansatz auf Basis von Archies Gesetz
gewählt, dessen Ergebnisse vorgestellt und mit dem üblicherweise
velwendeten Modell verglichen werden. Es wird versucht, ausgewählte
Parameter mit den Eigenschaften des Porensystems der Betone zu
konelieren und so die Möglichkeiten des vorgestellten Ansatzes
aufzuzeigen.

Lecture

Oktober 12, 2016

P. B. Sassmann
2nd International Conference on the Chemistry of Construction Materials (ICCCM), München, 10.–12. Oktober 2016

Development of ion- conductive polymer resins for the on-site fabrication of corrosion sensors

ABSTRACT:
Assessing the corrosion risk in steel-reinforced concrete can be
accomplished by implementing monitoring systems. For retrofit
installations the electrically conductive connection of sensors and
surrounding concrete is currently realised with cement-based embedding
mortars. The use of such aqueous systems changes the moisture content of
the concrete close to the sensor, which interferes significantly with
resistivity and/or potential measurements and makes interpretations of
the measured values problematic.
To circumvent these disadvantages,
we developed a liquid, reactive, non-aqueous polymer resin with high
electrical conductivity that can be used to fabricate sensors directly
inside drill holes. This way, a close contact between sensor and the
concrete walls is automatically provided. Since the polymer resin is not
aqueous, the moisture balance of the old concrete is not altered so
that reliable values can be obtained immediately after solidification.

Buchbeitrag

Mai 20, 2016

J.-P. Lecomte, O. Weichold
in Y. Liu (Ed.), Silicone Dispersions (Surfactant Science Series Vol. 159), CRC Press, Boca Raton, 2016, S. 301–331.

Silane-based Water Repellents for Inorganic Construction Materials

Master thesis

Mai 2, 2016

Pia B. Sassmann

Congratulations on the successful completion of the Master's thesis
Ionenleitende ungesättigte Polyester zur Ankopplung von Zulagekathoden in Beton
Ion-conductive unsaturated polyester for contacting galvanic couples in concrete

Publication

April 2, 2016

D. Heinze, Th. Mang, C. Popescu, O. Weichold
Thermochim. Acta 2016, 637, 143–153
To the article→

Effect
of side chain length and degree of polymerization on the decomposition
and crystallization behaviour of chlorinated poly(vinyl ester) oligomers
ABSTRACT:
Four members of a homologous series of chlorinated poly(vinyl ester)
oligomers CCl3–(CH2CH(OCO(CH2)mCH3))n–Cl with degrees of polymerization
of 10 and 20 were prepared by telomerisationusing carbon tetrachloride.
The number of side chain carbon atoms ranges from 2 (poly(vinyl acetate)
to 18 (poly(vinyl stearate)). The effect of the n-alkyl side chain
length and of the degree of polymerizationon the thermal stability and
crystallization behaviour of the synthesized compounds was
investigated.All oligomers degrade in two major steps by first losing
HCl and side chains with subsequent breakdownof the backbone. The
members with short side chains, up to poly(vinyl octanoate), are
amorphous andshow internal plasticization, whereas those with high
number of side chain carbon atoms are semi-crystalline due to side-chain
crystallization. A better packing for poly(vinyl stearate) is also
noticeable.The glass transition and melting temperatures as well as the
onset temperature of decomposition areinfluenced to a larger extent by
the side chain length than by the degree of polymerization.
Thermalstability is improved if both the size and number of side chains
increase, but only a long side chaincauses a significant increase of the
resistance to degradation. This results in a stabilization of PVAc
sothat oligomers from poly(vinyl octanoate) on are stable under
atmospheric conditions. Thus, the way todesign stable, chlorinated PVEs
oligomers is to use a long n-alkyl side chain.

Bachelor thesis

April 2, 2016