Open Access

Supplementary cementitious materials (SCM) are promising alternatives for the reduction of CO2 emissions in the cement industry. Despite extensive research, their adoption, using Germany as an example, remains low due to potential disruption in manufacturing processes and standardization issues. Furthermore, the precursor output rate of e. g., fly ash and ground granulated blast furnace slag (GGBFS) is limited not only due to general cement substitution but for shortages in their respective industries. As a result, SCMs may only serve as a viable alternative binder in niche applications, such as concrete maintenance and repair. Additionally, the use of dry activators such as Na2CO3 facilitates conventional production methods. This paper discusses results of sodium carbonate-activated slag mortars that were applied to concrete reference plates (A3-type as described in “Technische Regel Instandhaltung von Betonbauwerken,” eng. technical guideline for maintenance of concrete structures). The performance of alkali-activated slag (AAS) mortars was evaluated in terms of shrinkage behavior, compressive, flexural, and adhesive strength after dry thermal cycling and thunder-shower cycling. Interestingly, the results showed enhanced strength after exposure to these experimental conditions in comparison to ambient temperature curing. This highlights the critical role of proper curing, as AAS mortars are highly susceptible to increased shrinkage when not exposed to sufficient moisture. The previous results show that AAS mortars - even without optimization - meet the required properties for structural repair class “R3” as defined in DIN EN 1504-3, promoting SCMs as promising alternative binders for these practical use cases.

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Der Strukturwandel in der Landwirtschaft in Brandenburg hat dazu geführt, dass immer mehr landwirtschaftliche Betriebe vor der Nutzungsaufgabe stehen oder bereits seit Jahren brachliegen. Gleichzeitig ist im ländlichen Raum ein hohes Defizit an kulturellem Angebot festzustellen. Die Stärkung des Kulturangebots wird sowohl auf kommunaler als auch auf Bundesebene befürwortet. Zahlreiche Förderprogramme sollen den Ausbau des Kulturraums unterstützen, doch gerade die Umnutzung ehemaliger Agrargebäude stellt sowohl Kulturveranstalter als auch Planer oftmals vor eine große und scheinbar unlösbare Herausforderung. In diesem Leitfaden wird untersucht, mit welchen baurechtlichen Themen sich auseinandergesetzt werden muss, wenn in ehemals landwirtschaftlich genutzten Gebäuden Kulturveranstaltungen realisiert werden sollen und wie ein Gebäude auf seine Eignung als Veranstaltungsort überprüft werden kann. Die Einordnung der erforderlichen Ablaufschritte und Prüfkriterien soll anhand von Checklisten und Grafiken auch für semi-professionelle Nutzer möglich sein. Die schriftliche Ausarbeitung übernimmt eine erklärende Funktion und geht auf Grundlagen der Zulässigkeit sowie die baulichen Anforderungen und Genehmigungen ein. Dabei werden die drei Säulen des öffentlichen Baurechts intensiv beleuchtet.

In geotechnical engineering, the heterogeneity and variability of soil properties can pose a significant challenge for the design and construction of structures. This often-complex subsurface environment is generally represented by simplified homogeneous subsoil models derived from in-situ soundings and boreholes. However, these models do not consider the natural variability of the subsoil and the related uncertainties and, as such, disregard their influence on the design of geotechnical structures. Geostatistical models can be used to capture the inherent spatial subsoil variability by generating random fields (equiprobable realizations). The Random Finite Element Method (RFEM) is an approach that can be used to investigate the influence of soil variability (random fields) on the design of geotechnical structures. In this study, the technical implementation of the RFEM and its application for a twin tunnel case study in Munich (Germany) were examined. The influence of unexpected geological conditions was conducted within a probabilistic framework with the aim of comparing the results with the deterministic approach (idealized subsoil model). A conventional sensitivity analysis of soil variability was also performed. The results of this study demonstrate that deterministic approaches alone cannot adequately characterize tunneling-induced ground and foundation responses in heterogeneous subsoil conditions. Incorporating subsoil variability through RFEM provides a more realistic assessment, enabling engineers to better quantify risk, identify critical settlement zones, and ultimately improve the reliability of tunnel design.

In this study, we investigate with the Discrete Element Method (DEM) the mechanical behavior of a cohesionless granular material under undrained true triaxial conditions, considering both monotonic and cyclic loading. We link the microstructure evolution within the granular assembly to its macroscopic cyclic response. To capture the mechanical response of our reference material (Karlsruhe fine sand), a rolling resistance linear contact model along with spherical particles is calibrated through a trial-and-error process, adjusting the model parameters to capture the experimentally observed behavior as close as possible. A series of cyclic undrained triaxial tests were simulated to investigate the micromechanical processes underlying liquefaction of sand under cyclic shearing. We analyzed the evolution of various fabric indices, including the redundancy index, contact normal orientations, and fabric anisotropy in relation to the pre- and post-liquefaction responses. The results reveal that a redundancy index below unity provides a unified criterion for the loss of the isostatic condition within the granular assembly, which triggers the onset of liquefaction. Throughout the cyclic loading process, sliding-dominant contact-yielding mechanisms remain prevalent. Additionally, significant changes in contact normal orientation and increasing fabric anisotropy dependent on the induced axial strain occur as the sample undergoes post-liquefaction deformation.