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Item type:Publication, Access status: with files , Chemischer Angriff auf zementgebundene Baustoffe geotechnischer Elemente : Einflüsse der Baustoff-Boden-Interaktion, Bewertung und Empfehlungen hinsichtlich der Dauerhaftigkeit(2026-05); In natural groundwater and soils, cement-based building materials used in the construction of geotechnical elements can be exposed to chemical attack. In order to ensure the durability of cement-based materials, descriptive provisions are laid down in the current standardisation, which are based on empirical values. For the in situ construction of geotechnical elements, the building materials used and the relationship between load-bearing capacity and material damage, however, the specifications of descriptive requirements show deficits. In this work, the main deterioration mechanisms of concrete-aggressive substances in natural soils and groundwater are presented and concrete technology control options are shown. Furthermore, the provisions and limit values for ensuring the durability of concrete and reinforced concrete components are presented and evaluated in terms of uncertainties when transferring them to geotechnical elements. The techniques of foundation engineering that are essential for the construction of foundations and retaining systems in waterways engineering are characterised with regard to the descriptive durability that can be ensured against chemical attack and afterwards evaluated considering their sensitivity. The work contributes to a better understanding of the special aspects of the material-soil interaction, which has a considerable effect on the properties of the building materials used in geotechnical elements. Among other important aspects, the release of mixing water due to filtration effects during in situ manufacturing and the natural curing environment with low ground temperatures and permanent moisture supply lead to the development of a building material with low porosity and a dense pore structure and thus increase the resistance to chemical attack. Due to the occurrence and uncertainties regarding the effect on the load-bearing capacity, the attack of aggressive carbon dioxide on ground anchors was identified as a relevant and critical scenario and investigated experimentally. During the exposure time of 12 months, various depths of impact – mechanically degraded and chemically physically altered depths – were found for Portland and blast furnace slag cement paste samples. The depths of impact were significantly affected by the buffer capacity due to the calcium hydroxide content of the cement paste and the physical resistance in the period under review. The manufacturing of ground anchors in situ in an environment with aggressive carbon dioxide has the effect of blocking the cement paste of the grout body by adhering soil particles. Predictions for longer exposure times can only be derived with uncertainty on the basis of the available results. Based on a comprehensive research on the issue, concrete technology recommendations are given for increasing the resistance of building materials in a chemically aggressive environment. However, due to the complex interactions between exposure, material resistance and load-bearing capacity of the respective geotechnical elements presented in the work, no general concepts for durability design can be established.Publicationtype: Doctoral Thesis90 45 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Untersuchungen an Verpressankern in calcitabscheidendem Wasser(Ernst & Sohn, 2026-03-26); ; ; ; Investigations on grouted anchors in calcite-precipitating water. As part of a research project, model-scale grouted anchors were produced in sands and analysed with regard to their pull-out resistance up to a storage period of twelve months. Tap water, which, based on water analyses, is classified as calcite-precipitating, was used to flow around the anchors. Tension load tests were conducted on the grouted anchors. The results indicated that the ultimate limit state increased significantly after a storage period of six months, and further increase was observed after twelve months. After excavating, an additional layer of material with a thickness of up to three millimetres was identified on the surface of the grout body. It was observed that this layer increased in strength with an extended duration of storage. Analyses demonstrate that, within the contact zone between soil and cement paste, ions from the pore solution of the cement paste react with the calcium ions and carbonate ions present in the tap water, resulting in the formation of calcium carbonates. These carbonates form a matrix including the surrounding sand grains, which becomes stiffer over time.Publicationtype: Journal Article12 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Impact of sulfate on the release of genotoxic metals from hardened cement pastes(Elsevier, 2025-07-15); ; ; ; We investigated the effects of environmentally relevant sulfate concentrations on the leaching behavior of certain metalloids in hardened cement pastes. In our study, different cement pastes made of Portland cement (CEM I), blast furnace slag cement (CEM III/A) and a sulfate-resistant cement (CEM I SR0) were cured for 28 days and leached with ultrapure water and with sulfate-containing water. The released concentrations of the most metals and metalloids were independent of the presence of environmentally relevant sulfate concentrations below 1 µg/L or even below the limit of quantification (LOQ). However, the contact to sulfate-containing water led to an increased chromium release from CEM I, compared to leaching in ultrapure water. Under the same conditions an increased release of vanadium was observed from CEM III/A. A micronucleus test of the selected eluates revealed genotoxic effects which can be very likely attributed to the presence of vanadate. We were further able to connect the different leaching behavior of cement in sulfate-containing water compared to ultrapure water to changes of the specific surface area of the hardened cement pastes.Publicationtype: Journal Article4 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Effect of Grouting on the Resistance of Portland and Blast Furnace Slag Cement Paste Against Chemical Attack by Aggressive Carbon Dioxide(2023-06); ; Chemical attack by aggressive carbon dioxide on cement-based materials is of major concern for foundations of engineering structures with long service life. The exposure in natural groundwaters leads to dissolving attack, where all hydration products are deteriorated. The resistance of cement-based materials increases therefore with a low porosity and a high content of inert aggregates. For ground anchors cement suspensions are grouted during the manufacturing process. In non-cohesive soils the mixing water is filtered by the applied pressure. This leads to an improved and dense microstructure. Due to their small dimensions and high tensile load capacity ground anchors can be subjected to a loss of load bearing capacity already in short-term periods because of the attack by aggressive carbon dioxide. This paper investigates the effect of grouting on the resistance of cement paste against the chemical attack by aggressive carbon dioxide. Three cement types CEM I, CEM III/A and CEM III/B are investigated. The object of the investigations are grouted and neat cement paste samples which are prepared in the laboratory and afterwards stored for 3 and 6 months in an aggressive solution with ~ 90 mg CO2 /l. The depth of impact is assessed by polarized light microscopy on thin sections. The results conclude in an assessment of the resistance of the different cement types and an evaluation of the durability for issues in building practice.Publicationtype: Conference Paper19 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Attack of aggressive carbon dioxide on hardened Portland and blast furnace slag cement pasteNatural groundwater and soil can contain substances which are aggressive to concrete and cement-based structures. Especially aggressive carbon dioxide occurs frequently. Chemical attack by aggressive carbon dioxide occurs in several phases in commercial cements used in foundation engineering. After a period of carbonation a leading front where calcium hydroxide is dissolved, depending on the availability in the binder matrix, is generated. As the attack progresses, the calcium carbonate formed is dissolved, leaving a layer rich in amorphous silicon dioxide, which has lower mechanical strength. This can result in problems in the long-term load-bearing behavior of more sensitive components with smaller dimensions and under tensile stress, in particular ground anchors and micro piles, which are manufactured using cement suspensions in the subsoil. This study evaluates the mechanisms induced by aggressive carbon dioxide in CEM III/A and CEM III/B compared with CEM I paste. Cement paste specimen with water-cement ratios of 0.4 and 0.5 stored in about 90 mg/l (exposure class XA2) aggressive CO2 for 3, 6 and 12 months are investigated. The methods include X-Ray fluorescence analysis as well as polarized light microscopy on thin sections. The depth of impact is measured and evaluated in terms of durability of geotechnical elements.Publicationtype: Conference Paper20 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Quellverhalten von Portland- und Hochofenzementstein bei unterschiedlichen TemperaturenZementgebundene Baustoffe quellen bei permanenter Wasserlagerung, d. h., sie erfahren eine zeitabhängige Volumenzunahme. Wesentlich für das Quellverhalten zementgebundener Baustoffe ist der volumetrische Anteil an Zementstein. Für Bereiche, in denen Betonbauteile permanent einer Wasserumgebung ausgesetzt sind, wie zum Beispiel bei Gründungen im Grundwasser, kann das Quellverhalten ggf. die Tragwirkung verbessern, da sich Bauteile im Boden infolge des Quelldruckes verspannen. Dieser Beitrag untersucht das Quellverhalten von Zementstein aus CEM I und CEM III/B mit w/z-Werten von 0,3 und 0,5 bei 10 °C und 20 °C betrachtet. Zusätzlich wurden im Rahmen der Untersuchungen Zementsuspensionen verpresst, um Filtrationseffekte abzubilden. Neben dem Quellmaß zu verschiedenen Zeitpunkten (1, 3, 5, 7, 14, 28 und 56 Tage) wurde der Hydratationsgrad und Gehalt an Calciumhydroxid mit Hilfe der Thermogravimetrie und die Porosität mittels Quecksilberdruckporosimetrie als Materialkennwerte bestimmt. Die Untersuchungsmethoden erlauben einen Rückschluss von Porosität und Hydratphasenausbildung auf das Quellverhalten der untersuchten Zementsteine zu ziehen. Bei beiden Zementarten führen niedrigere Lagerungstemperaturen zu höheren Quellmaßen.Publicationtype: Conference Paper19 33 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Effect of grouting on the hydration and microstructure of portland cement and release of environmentally relevant substancesGround anchors are frequently used in foundation engineering. During manufacturing cement suspension is filled in a borehole and subsequently grouted. In non-cohesive soils, grouting leads to a filtration process, where the mixing water is pressed out from the cement suspension and a so-called “filter cake” is formed. The scope of the experimental investigations are ground anchors from a large-scale experiment and grouted and neat cement pastes from laboratory tests. The hydration process and microstructure of the hardened grouted cement paste have been investigated in comparison to grout bodies from the large-scale experiment. Elution tests were carried out to determine the leaching behaviour of both the neat cement paste and the grout bodies. Furthermore, filtered mixing water from laboratory test samples were analysed. The porosity was determined by water absorption under atmospheric pressure and mercury intrusion porosimetry (MIP). The hydration process was investigated by using thermogravimetric analysis (TGA). The composition of the filtered mixing water and the results of the leaching tests allowed to assess the impact of the grouting process on the surrounding soil and groundwater from an environmental point of view. This paper concludes with an evaluation of the effect of the grouting process. The results from the experimental programme are compared between grouted and neat cement paste as well as for grout bodies. The conclusion is completed by consideration of environmental aspects.Publicationtype: Conference Paper41 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Influence of cement grouting on the microstructure of cement paste(2021-06); ; In foundation engineering, ground anchors are a frequently used type of foundation element. The manufacturing method of ground anchors with grouting of cement slurry has a high impact on the load-bearing capacity of those elements especially in non-cohesive soils. In subsoils like these, a filtration of the cement grout occurs depending on the grouting pressure and duration. Due to this filtration, the initial water-cement ratio is reduced in the grouted body especially in the edge area. This paper will investigate the influence of grouting on the microstructure of various cement suspensions. Cement suspensions of different cement types (CEM I and CEM III) have been examined in laboratory tests with a filter press. Influencing factors on groutability are besides the water retention of the cement type also the building up of a filter cake in the transition respectively filtration area. The microstructure is characterized by porosity investigations (e.g. mercury intrusion porosimetry). With the aim to improve the microstructure in the contact zone additives are used and their influence on the groutability and the hardened cement paste are outlined. The results will be discussed under the aspect of providing a dense binder matrix to increase the resistance to aggressive groundwater.Publicationtype: Conference Paper102 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Cement-based geotechnical elements exposed to chemical attack—provisions for durability in standardsGeotechnical elements made of concrete, mortar and cement slurry, such as bored piles and grouted anchors, are widely used for the foundations of civil engineering structures. Depending on the environmental conditions and properties of the subsoil they can be exposed to chemical attack by groundwater and/or soil. The current system in standards for specifying and ensuring the durability of geotechnical structures is of a prescriptive nature, giving limiting values and provisions for composition and construction details. This paper examines the viability of the provisions in the standards for the durability design and assessment of various geotechnical elements against different types of chemical attack. The existing deficits and uncertainties are indicated. © 2019 Taylor & Francis Group, London.Publicationtype: Conference Paper330