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Item type:Publication, Access status: with files , Osmotische Prozesse im System zementärer Werkstoff - Reaktionsharzbeschichtung, Langfassung der Beschreibung der Arbeiten der TUHH(Technische Universität Hamburg, 2026-06-24); ; ; ; The formation of blisters in the system reactive resin coating – concrete is an important damage process. The details of the process are controversial in the scientific literature. Within the project the effects of the cementitious material (7 different mortars), the reactive resin, and other conditions were investigated systematicelly. Laboratory investigations and simulations were used. Hypothesis was, that the mineral building materials acts as a semipermeable membrane, and the damage is caused by an osmotic pressure, possibly intensified by an alkali-silica reaction (ASR). Experiments showed, that all mortars act as a semipermeable membrane. Osmotic pressure up to 4.5 bars could be measured with the mortars. The mortars where passed by all species in the solutions. The simulations showed, that osmotic pressure is not the cause of blistering, but pressure caused by the cappillary suction of moisture into the cementitious substrate. Instructions to avoid damages in systems were osmotic pressure is relevant were acquired.Publicationtype: Report70 22 - Some of the metrics are blocked by yourconsent settings
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: with files , Einfluss der Art grober Gesteinskörnung auf Struktur und Eigenschaften von ultrahochfestem Beton - Abschlussbericht in LangfassungThe addition of coarse aggregate is one possibility to lower the cement content of ultra-high strength concrete (UHPC). Within the research project an UHPC with a maximum grain size of 0.5 mm was varied with 30 vol.-% of coarse aggregate, with a grain size of 5-8 mm. 16 different rock types were added to the fine-grained reference mixture. The rock types cover most of the high strength rocks available in Germany. The rock and the UHPC specimens were examined under different aspects. Both the mechanical behaviour, as the structural and chemical properties were determined. As the main results it can be stated, that not only basalt, but a lot of rock types can be used to produce UHPC, even if the addition of coarse aggregates decrease the strength of all specimens in comparison to the original mixture. Basalt and other fine-grained vulcanic rocks are useful, but also coarse-grained plutonic granite and metamorphic granulite and gneiss. Also with dense sedimentary limestone (Massenkalk), UHPC can be produced. Coarse-grained metamorphic marble, sandstone (also with very high strength), and the sandstone-like greywacke, and metamorphic amphibolite were not successful. Dolomite and the examined quarzite resulted in somehow inconsistent strength values. There is a strong linear correlation of the rock and the UHPC compressive strength. There is no threshod value of the rock strength, resulting in a decrease of the UHPC strength, but the lower the rock strength, the lower is the UHPC strength. A correlation between the typical grain size of the rock and the UHPC strength is not visible. In no case, also with very high spatial analytical resolution, a chemical reaction was visible between the minerals of the rocks and the cement matrix. It seems, that the UHPC ist too dry, after short time, to get chemical reactions between the rock grains and the binder matrix. All rock types were very well embedded in the cement matrix. They are great differences in the coarseness of the grain surfaces. Together with differences in the porosity of the rocks this resulted in effects on UHPC workability.Publicationtype: Report34 7 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , High-resolution electron microscopic investigations on the fatigue behaviour of ultra-high-performance concrete and modelling with bonded-particle model(Springer, 2026); ; ; ; Given the increasing demand for sustainable and lightweight concrete structures, the application of ultra-high-performance concrete (UHPC) has gained significant relevance. However, in contrast to static loading conditions, cyclic loads are more prevalent in real-world scenarios. Despite the superior mechanical properties of UHPC, it may exhibit a different resistance to cyclic loading. Consequently, this study focuses on both experimental and numerical analyses to investigate the primary mechanisms responsible for crack initiation at the meso-, micro-, and nanoscale. Following mechanical fatigue testing, microstructural alterations were characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). To extend these findings to the mesoscale, a novel rheological model was developed. The results suggest that fatigue damage originates from nanoscale transformations of ettringite, combined with a densification of the cementitious matrix. Moreover, an increased content of unhydrated cement clinker within the matrix enhances fatigue resistance. At the mesoscale, stress concentrations around aggregate particles intensify with increasing load cycles, propagating into the binder matrix and contributing to further material degradation.Publicationtype: Book Part10 - 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: with files , Micro- and nanostructural investigations of high and ultra-high performance concrete under fatigue(Elsevier, 2025-04-30); ; A fine-grained UHPC, both undamaged and damaged by fatigue loading, was comparatively examined by various microstructural analytical methods, to evaluate the different techniques with respect to their applicability and relevance for the investigation of fatigue damage processes. The fatigue tests were stopped at the transition from phase II to phase III of the s-shaped strain development. The cyclic compression loading was performed with a frequency of ft = 1 Hz, and a stress level between Smin = 0.05 and Smax = 0.75 (fcm = 170.2 MPa). The fatigue process under these loading conditions is dominated by alterations and damages on the nano-scale, that can be observed by transmission electron microscopy. The resulting coarsening of the pore structure was also visible with dynamic vapor sorption. Nanoindentation indicates, that changes of the HD-C-S-H-phase occur. IR spectroscopy also indicates changes of the C-S-H phase and thermal analysis changes of the water content. Dynamic mechanical analysis (DMA) gave insight into the complex Young's modulus and Poisson's ratio changes. The acoustic emission technique gives information on the different processes during the single phases of fatigue and reveal a very different damage behaviour of dry and moist materials. Some microcracks are visible with light microscopy. It appears, that the number of cracks after fatigue is higher than before. With X-ray computed tomography, X-ray powder diffraction, the drying behaviour, the free water uptake, the water uptake under vacuum and by mercury intrusion porosimetry no significant differences between specimens with and without fatigue loading could be observed in this examination.Publicationtype: Journal Article16 11 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Effects of Si/Al molar ratio on the microstructure of Metakaolin-based geopolymersPublicationtype: Conference Paper23 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Ausgewählte reaktionskinetische Daten von Gesteinskörnungen im alkalischen Milieu als mögliche Grundlagen zur Vorhersage der Alkaliempfindlichkeit(2025); An alkali-silica reaction (ASR) is a reaction that takes place within concrete structures and whose product can significantly shorten the durability of the structures through expansion. The most reliable protection against this damage is the avoidance of alkali-reactive aggregates in the concrete. There are similar international test methods for the detection of alkali-reactive aggregates. These are mainly based on the evaluation of the elongation of specimens made with the aggregate to be analysed. This study presents a potentially new test method based on solution tests and the investigations into its suitability. In this work, a new fast test procedure developed in advance for the detection of alkali-reactive aggregate was tested for its suitability on different aggregates. For this purpose, the aggregates were precisely described in terms of their composition, structure and size, and a statistically significant number of tests were carried out. By modeling the test results and determining the influence of the characteristics of the aggregates on these results, the test procedure can be tested for suitability and evaluation criteria for the reactivity of the aggregates can be developed.Publicationtype: Doctoral Thesis62 48 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Building "without land take" - current state of land take in GermanyBased on the United Nations Agenda 2030 the government of Germany has formulated a national sustainability strategy which seeks to mitigate the ongoing increase in land take and aims for a circular economy until the year 2050 instead. Despite these political efforts, more land has been converted to building land in recent years. As part of a recent research project at Hamburg University of Technology, a preliminary study on land-take in Germany has been carried out as first milestone. Drivers of land take in recent years have been the regions of north-eastern, western and south-western Germany, while in centre regions a notable decrease in daily land take could be observed. The northern metropolitan areas mostly reported decreasing rates in their urban centres while land take increased in their suburban and greater areas. In contrast a densification of urban centres could be observed in the southern regions, while the surrounding rural areas showed decreasing or neutral trends. Only few counties reported a consistent negative land take over the recent years. Additional findings indicate that land take came almost exclusively at the expense of agricultural areas. In combination with recent efforts of afforestation backed up by comprehensive environmental protection laws, the available arable land quickly decreased over the recent years. To challenge this ongoing problem, the research project takes a novel approach on the design of large-scale commercial real estate by combining these buildings with commercial agriculture. A project outline is given at the end of the paper.Publicationtype: Conference Paper5 8