Ueli Angst

• Professor
• Professor at ETH Zurich

This study investigates the formation mechanism of zinc phosphate conversion coatings on pearlitic steel and ferritic iron with emphasis on the impact of microstructure and substrate corrosion. Deposition parameters, including pH (2 and 2.5) and temperature (50°C and 70°C), were explored. Open circuit potential (OCP) monitoring was used to identify...

Numerous aqueous systems host elements in multiple redox states, with wide ranging implications such as their influence on the formation/dissolution of minerals, water toxicity, and nutrient cycling. To uncover governing mechanisms and complex chemical interactions in aqueous systems, reactive-transport models have increasingly gained importance. H...

Chloride‐induced corrosion of the reinforcement steel is the main degradation mechanism for reinforced concrete, considerably affecting the load and deformation capacity of structures. Despite its importance, there is limited knowledge about the morphology of corrosion attacks and accordingly, relatively crude assumptions are generally made when co...

Concrete carbonation has been proven to be a potential path for reducing the carbon footprint of cement industry. However, since carbonation reaction significantly alters the chemical composition and microstructure of cement-based materials, it is necessary to carefully assess its effects on the transport properties and durability of concrete mater...

We introduce an experimental setup to chemically image corrosion processes at metal-electrolyte interfaces under stagnant, confined conditions—relevant in a wide range of situations. The setup is based on a glass capillary, in which precipitation of corrosion products in the interfacial aqueous phase can be monitored over time with optical microsco...

Time-coherent segmentation and tracking of key meso-scale features in steel-reinforced concrete undergoing corrosion

The formation of energetically favorable and metastable mineral phases within the Fe–H2O system controls the long-term mobility of iron complexes in natural aquifers and other environmentally and industrially relevant systems. The fundamental mechanism controlling the formation of these phases has remained enigmatic. We develop a general partial eq...

It was generally recognized that water absorption into cementitious materials shows two stages, the early stage with fast water uptake and the late stage with the reduced water absorption rate. Two types of anomalous moisture transport can be classified based on the shape of the water absorption curve. To investigate the main causes of different ty...

Macroscopic voids at the steel-concrete interface and their degree of saturation with an aqueous electrolyte are known to play an important role in the corrosion of steel in reinforced concrete. Irrespective of the exposure conditions and testing parameters, corrosion products have been reported to consistently precipitate in a unique pattern withi...

We introduce an experimental setup to chemically image corrosion processes at metal-electrolyte interfaces under stagnant, confined conditions relevant in a wide range of situations. The setup is based on a glass capillary, in which precipitation of corrosion products in the interfacial aqueous phase can be monitored over time with optical microsco...

Traditional approaches to mathematically describe spontaneous imbibition are usually based on either macro-scale models, such as Richards equation, or simplified pore-scale models, such as the bundle of capillary tubes (BCTM) or pore-network modeling (PNM). It is well known that such models cannot provide full microscopic details of the multiphase...

Accurate model predictions of corrosion-driven damage in reinforced concrete structures necessitate a comprehensive understanding of the rate of corrosion product formation. Here, we investigate the influence of dissolved Si characteristic of cementitious systems on the rate of corrosion product transformation at alkaline pH. Compared to systems ag...

The durability of MgO/hydromagnesite mortars was studied with respect to their corrosion performance and resistance to chloride attack and moisture. MgO/hydromagnesite pastes were cured in chloride solution to induce potential formation of Mg-chlorides; however, no such phases were observed. Rapid chloride ingress measurements demonstrated high pen...

Corrosion of steel reinforcement in concrete is a common degradation mechanism occurring in infrastructures worldwide. Even though extensive research has been conducted over the last decades to accurately predict the influence of steel corrosion on concrete durability, a comprehensive understanding of several micro-scale processes simultaneously in...

The steel–concrete interface (SCI) is known to play a major role in corrosion of steel in concrete, but a fundamental understanding is still lacking. One reason is that concrete’s opacity complicates the study of internal processes. Here, we report on the application of bimodal X-ray and neutron microtomography as in-situ imaging techniques to eluc...

Das Dokument kann kostenlos von http://www.mobilityplatform.ch heruntergeladen werden (Eingabe der Dokumenten-Nummer). ZUSAMMENFASSUNG Der vorliegende Bericht beschreibt Untersuchungen an permanenten Mikropfählen und ungespannten Ankern der Schutzstufe 2a bezüglich ihres Zustandes mit Fokus auf Korrosionserscheinungen. Ein besonderes Augenmerk bei...

PourPy is an open-source python package, capable of generating thermodynamic stability diagrams of solid phases and complexes in aqueous electrolytes. These so-called Pourbaix diagrams provide valuable information about the reactivity of chemical elements and compounds as a function of the electrochemical potential and the pH. In the context of cor...

Accurate model predictions of corrosion-driven damage in reinforced concrete structures necessitate a comprehensive understanding of the rate of corrosion product formation. Here, we investigate the influence of dissolved Si characteristic of cementitious systems on the rate of corrosion product transformation at alkaline pH. Compared to systems ag...

Cathodic protection was introduced two centuries ago and since has found widespread application in protecting structures such as pipelines, offshore installations, and bridges from corrosion. Despite its extensive use, the fundamental working mechanism of cathodic protection remains debated, particularly for metals in porous media such as soil. Her...

The prediction and prevention of steel corrosion in engineering applications rely on the accurate understanding of kinetic parameters, such as the Tafel slopes and exchange current densities. These parameters show a large spread in literature. We investigated the dependency of these kinetic parameters on the measurement methodology for stainless an...

Recycling the concrete of old and destroyed buildings and using it to build new buildings is a promising technology for post-war Ukraine, but in many cases, it may be economically and environmentally more justified to rehabilitate such buildings. This article provides an analysis of the state of the housing stock of Ukraine from prefabricated reinf...

The formation of energetically favourable and metastable mineral phases within the Fe−H2O system controls the long-term mobility of iron complexes as well as other aqueous phase constituents in natural aquifers, soils and other environmentally and industrially relevant systems. The fundamental mechanism controlling the formation of these solid phas...

The transformation of 2-line ferrihydrite to goethite from supersaturated solutions at alkaline pH ≥13.0 was studied using a combination of benchtop and advanced synchrotron techniques such as X-ray diffraction, thermogravimetric analysis, and X-ray absorption spectroscopy. In comparison to the transformation rates at acidic to mildly alkaline envi...

Moisture in concrete is the essential factor of many degradation mechanisms to reinforced concrete structures, such as carbonation, chloride ingress, and frost attack. Therefore, it is important to arcuately determine and predict moisture state and moisture distribution inside the material. Most moisture transport models generally view concrete as...

Over the last years, significant advances were made with respect to sensors, data logging, data communication, and algorithm‐based data analysis. These developments have the potential to take structural health monitoring, especially structural corrosion health monitoring, to the next level. This contribution focuses on corrosion and durability moni...

The accumulation of corrosion products throughout the concrete pore network may lead to the development of internal stresses and spalling of the concrete cover, thus facilitating further structural detonation. To gain a more profound understanding of this self-sustaining sequence of events, both the type of corrosion product(s) as well as their rat...

Cathodic protection (CP) was introduced two centuries ago and since has found widespread application in protecting structures such as pipelines, offshore installations, and bridges from corrosion. Despite its extensive use, the fundamental working mechanism of CP remains debated, particularly for metals in porous media such as soil. Here, we offer...

Einer der maßgebenden Werkstoffe im Konstruktiven Ingenieurbau ist Stahl in Form von Baustahl, Betonstahl, Befestigungstechnik etc. Stahl bietet eine hohe Festigkeit in Kombination mit beliebiger Formbarkeit, guter Verarbeitbarkeit und Schweißbarkeit. Um das Potenzial von Stahl auszuschöpfen, ist das Wissen über dessen maßgebenden Schädigungsmechan...

The steel-concrete interface (SCI) is known to play a major role in corrosion of steel in concrete, but a fundamental understanding is still lacking. One reason is that concrete's opacity complicates the study of internal processes. Here, we report on the application of bimodal X-ray and neutron microtomography as in-situ imaging techniques to eluc...

Recycling the concrete of old and destroyed buildings and using it to build new buildings is a promising technology for post-war Ukraine, but in many cases, it may be economically and environmentally more justified to rehabilitate such buildings. This article provides an analysis of the state of the housing stock of Ukraine from prefabricated reinf...

The transformation of 2-line ferrihydrite to goethite from supersaturated solutions at alkaline pH >= 13.0 was studied using a combination of benchtop and advanced synchrotron techniques such as X-ray diffraction, thermogravimetric analysis and X-ray absorption spectroscopy. In comparison to the transformation rates at acidic to mildly alkaline env...

Understanding fracture in cementitious materials caused by the deposition and growth of corrosion products requires scale-bridging approaches due to the large length-scale difference between the micro-pores, where deposition occurs, and the structure, where deterioration manifests. Cementitious materials bear a highly heterogeneous micro-structure...

To reduce the carbon footprint of cement and concrete industry, CO2 curing has been recognized as one of the sufficient ways. However, the amount of CO2 uptake by the normal structural concrete is limited because of their low permeability. Compared to curing the traditional concrete members, CO2 curing of pervious concrete is expected to sequester...

There is a dilemma between designing cementitious binders with low greenhouse gas (GHG) emissions and at the same time attempting to satisfy carbonation test requirements. In fact, various studies have shown that with increasing clinker replacement, the carbonation rate increases. The established paradigm to ensure durability, particularly to avoid...

The carbonation of cementitious materials is often attributed to be one of the major causes of corrosion in reinforced concrete, possibly leading to premature deterioration. When assessing the effect of carbonation on corrosion, most studies are limited to measuring the carbonation rates of different concretes. From these, replacing clinker with su...

The diffusion potentials can cause significant errors in corrosion-related investigations of reinforced concrete structures (half-cell potential mapping, potentiometric sensors). Therefore, an improved understanding of the diffusion potentials in cement-based materials is needed. This study investigates the permselective behavior and its implicatio...

Understanding fracture in cementitious materials caused by the deposition and growth of corrosion products requires scale-bridging approaches due to the large length-scale difference between the micro-pores, where deposition occurs, and the structure, where deterioration manifests. Cementitious materials bear a highly heterogeneous micro-structure...

Whilst the oxidation of Fe(II) in aerobic conditions has been studied thoroughly, an in-depth knowhow on the fate or stability of Fe(II) in solutions with near-neutral pH under anaerobic conditions is still lacking. Here, we experimentally investigated the kinetics of Fe(II) oxidation in solutions with pH ranging between ∼5 and 9, under aerobic (wh...

Corrosion in reinforced concrete structures is among the major degradation mechanisms. The quantification and description of the spatial distribution of the corrosion condition within a structure on the basis of condition assessments are important. This study considered half-cell potential mapping data as a widely used technique to detect corrosion...

Unnoticed corrosion in underground reinforced concrete structural members – such as foundations, retaining walls, or piles – may severely threaten the integrity of structures. However, condition assessment of the ground-buried structural parts is challenging, because the areas of interest are hardly accessible for visual inspection or non-destructi...

Besides the fact that concrete recycling allows to avoid landfills disposal and contributes to a closed-cycle economy, such option may be very much in demand in war struck regions such as Ukraine, which after the end of the war, are faced with the problem of rebuilding and reconstructing. Beyond this emergency, even in peacetime extensive parts of...

Carbonation of cement-based materials may lead to durability problems, so that it is necessary to find a way to reduce the effect of carbonation on concrete durability. This study investigated the effects of cellulose nanofibrils (CNFs) on the durability of carbonated cement-based materials. Two dosages of CNFs were used to prepare cement pastes an...

This study explores machine learning (ML) algorithms to predict the pore solution composition of hardened cementitious systems produced with Portland cement (PC) and supplementary cementitious materials (SCM). Literature data on pore solution compositions for different cementitious systems was collected and compiled in a comprehensive database cont...

The aim of this work was to revisit second‐harmonic generation (SHG) as a technique for the in situ analysis of oxide film formation on steel samples immersed in aqueous solutions and during electrochemical experiments. The measurements were compared to active reflectance spectroscopy (ARS), which is a more established in situ spectroscopy techniqu...

Steel corrosion is the most prominent and costly reason for premature structural degradation of reinforced concrete structures. Throughout a structure's service life, if chlorides or carbonates reach the steel-concrete interface, steel reinforcement may experience corrosion. Whilst the transport of chloride and carbonate species has been extensivel...

A substantial part of corrosion research relies on the analysis of polarization curves to obtain corrosion currents, Tafel slopes and other parameters, such as exchange current densities. This, often manual analysis remains highly subjective, which hampers the reproducibility of corrosion research and makes comparison of reported Tafel slopes, corr...

We present a novel, fundamentally sound approach for the determination of corrosion rate and anode location in reinforced concrete. In this contribution, we focus on the sensitivity of this non-destructive method with respect to the state of corrosion and concrete properties. Corrosion is often the main cause for the premature deterioration of rein...

Reliable techniques for non-destructive evaluation of reinforced and prestressed concrete structures are of utmost importance for the maintenance of aging infrastructure. A particular area of interest is the evaluation of grouting quality within tendon ducts in post-tensioned concrete. Detecting voids and water-filled cavities in plastic or metal d...

Various electrochemical techniques exist to study corrosion processes locally. Generally, sample preparation is required to ensure smooth surfaces, which may limit the applicability of experimental findings to engineering conditions. To overcome these limitations, we use a probe with a soft porous diaphragm that establishes electrolytic connection...

Carbonation may potentially lead to corrosion of steel bars in reinforced concrete. This concern presents a major barrier against the implementation of sustainable low-clinker cementitious materials in the design of reinforced concrete structures. Various studies have documented the relationship between different equilibrium moisture states in carb...

Any research results related to reactive transport in porous media can be considered. If you are interested to submit your contribution to this special issue kindly contact the Lead Guest Editor (Dr. Zhidong Zhang, zhidongz@ifb.baug.ethz.ch) first and share the abstract for viewing as the first step.

The steel–concrete interface (SCI) is a complex, multi-phase and multi-scale system. It is widely known to influence the performance and long-term durability of concrete structures. However, a fundamental understanding of its properties and effects on corrosion initiation of embedded reinforcing steel remains elusive. This is attributed to its comp...

Calculation of service life costs allows for a holistic assessment of the cost‐effectiveness of options in design regarding materials and intervention strategies for an infrastructure object. A method is presented in which probabilistic service life modeling and cost calculations are combined. This method is exemplified by two cases of reinforced c...

All existing models to forecast the corrosion performance of reinforced concrete structures exposed to chloride environments are based on one common theoretical concept, namely, a chloride threshold, as a sharply defined trigger for corrosion, followed by a period of active corrosion. We critically review the resulting treatment of corrosion initia...

Electrical resistance (ER) probes are a technique used to monitor the corrosion rate (CR) of metals in a wide range of applications and industries. However, limited data comparing CR measured with ER-probes, weight loss and electrochemical methods is available. The aim of this work is to provide data regarding the reliability of CR measurements wit...

Steel corrosion can cause serious damage to reinforced concrete structures. This study employed multiple techniques, including SEM/BSE, EDX and Raman spectroscopy, to analyze the distribution and mineral composition of corrosion products (rusts) in corroded reinforced cementitious materials under two conditions, namely, chloride‐induced corrosion a...

The recent interest in 3D printing with concrete has generated great interest on how inhomogeneities arise and affect performance parameters, in particular strength and durability. With respect to durability, of particular interest is how 3D printed layer interfaces can impact transport of species of interest, such as moisture, chlorides, or carbon...

Robot‐assisted point‐by‐point wire and arc additive manufacturing is considered a promising technology for optimising the production of metallic connections used in complex nodes, space trusses or grid shells. While mechanical properties of such elements were proved suitable for structural applications, a lack of knowledge exists concerning their d...

If you want to read the full paper, please check our open-access paper https://doi.org/10.1016/j.cemconres.2022.106990. To be honest, I do not know why this paper appears in SSRN Electronic Journal.

We present an approach, termed electrochemical tomography (ECT), for the in-situ study of corrosion phenomena in general, and for the quantification of the instantaneous rate of localized corrosion in particular. Traditional electrochemical techniques have limited accuracy in determining the corrosion rate when applied to localized corrosion, espec...

Aqueous iron hydrolysis products and chloride complexes influence steel corrosion kinetics and dictate the amount and type of corrosion products formed. Here, we compile a thermodynamic database devoted to aqueous iron species and solid oxides as well as chloride complexes, aiming to describe their speciation and solubility within the prevailing ch...

The critical chloride content Ccrit is an indicator of the corrosion resistance of reinforcing steels in concrete. In this article, several experimental methods for determining the critical chloride content Ccrit of mild and alloyed (12% Cr) steel in cementitious materials are compared. The methods used include accelerated polarization tests and te...

The accurate simulation of moisture transport in cement-based materials is an important step to predict many durability processes of concrete structures. This paper studied the effects of boundary conditions on modeling moisture transport, in particular for simulating drying kinetics and the inverse determination of liquid water permeability. Three...

The critical chloride content Ccrit is an indicator for the corrosion resistance of reinforcing steels in concrete. In this article, several experimental methods for determining the critical chloride content Ccrit of mild and an alloyed (12% Cr) steel in cementitious materials are compared. The methods used include accelerated polarization tests an...

The one-dimensional water absorption into cement-based materials, possibly the simplest case of unsaturated water flow playing a fundamental role in predicting mass transport and durability, is still far from being completely understood due to several puzzling anomalies. Considering the water sensitivity of C-S-H gels (swell upon wetting and contra...

Experimental evidence related to the interactions between steel corrosion and bentonite in deep geological repositories is reconsidered. The released Fe²⁺ interacts with the smectite and precipitates as Fe³⁺ when oxidised by residual immobile oxygen. This leads to the development of coloured fronts in the bentonite. The evolution of these fronts ca...

Testing the critical chloride content (Ccrit) in laboratory samples or in samples retrieved from structures enhances the understanding of rebar corrosion initiation in concrete and can result in a significant improvement of predicting the residual service life of ageing structures. A possible drawback of test methods for Ccrit is that they can be t...

The point-by-point wire and arc additive manufacturing technology allows precisely depositing of high strength material. In combination with a robotic arm and sensing techniques during printing, it can be used as a novel efficient joining method for custom structural steel components. For accessibility to the parts to be joined, flexibility on the...

This article presents and validates active interaction force control and planning for fully actuated and omnidirectional aerial manipulation platforms, with the goal of aerial contact inspection in unstructured environments. We present a variable axis-selective impedance control which integrates direct force control for intentional interaction, usi...

Carbonation of concrete is generally assumed to lead to reinforcing steel corrosion. This mindset has long dictated the research priorities surrounding the developments towards new, low-emission binders. Here, by reviewing documented practical experience and scientific literature, we show that this widely held view is too simplistic. In fact, there...