Research in the Division of Building Materials

The application of recycled aggregates in the concrete construction process enhances the resource efficiency and sustainability of concrete construction. Concretes with recycled aggregates, so-called R-concretes, will be used more frequently in construction projects in the future. In addition, the aim is to significantly increase the proportion of recycled aggregates in concretes beyond the permissible proportions currently regulated in Germany. However, the fire behavior of these concretes, which partly contain organic components and above all have a higher porosity, is largely unexplored and there are no reliable design rules. As a result, the increased use of recycled aggregates in building construction in Germany is restricted.

The aim of the proposed research project is to characterize and investigate the material properties of concretes with recycled aggregates for use in building construction and to review or adapt design rules according to prEN 1992-1-2 (2021-09) and DIN 4102-4 to facilitate their use in practice.

In the project, the limits of the addition of recycled aggregates are to be examined and their effect on the technical concrete properties such as fresh concrete properties, strength and durability under ambient conditions are to be investigated experimentally. To characterize the fire behaviour, the thermal and thermo-mechanical properties will be investigated and compared with those of standard concrete. 

On this basis, recommendations for the fire protection design of concrete components containing a larger proportion of recycled aggregate will be developed.

Project partners: Division of Fire Safety, Institute for Building Materials, Solid Construction and Fire Safety, TU Braunschweig

Project funding: Zukunft Bau (https://www.zukunftbau.de) - Federal Institute for Research on Building, Urban Affairs and Spatial Development (BBSR) at the Federal Office for Building and Regional Planning (BBR)

Responsible persons: Dr.-Ing. Thorsten Leusmann, Mahmoud Eslami Pirharati M. Sc.

Funding period: 01.11.2023 to 01.11.2025

The aim of the project is the development of a combined additive manufacturing process for the robotic production of rammed earth components with integrated rammed concrete reinforcements. The objective is to enhance the performance of rammed earth components by strategically incorporating rammed concrete reinforcements along the primary load paths, utilizing the robotic rammed earth manufacturing technology. The separability of rammed earth and rammed concrete during processing allows for the stabilization of rammed earth components without compromising the excellent recycling properties of the earth material.

Combined additive manufacturing relies on a finely tuned material-process interaction that allows both materials to benefit from each other.

Project funding organization: Zukunft Bau

Project partner: Institute for Structural Design (ITE) at the Technische Universität Braunschweig

Duration: 3 years (start: 01.08.2023)

Contact person: Evelien Dorresteijn M. Sc., Dr.-Ing. Thorsten Leusmann, involved scientists: Prof. Dr.-Ing. Dirk Lowke (TU München)

The high-level radioactive waste (spent nuclear fuel, reprocessing waste) resulting from the use of nuclear energy in Germany is currently stored in transport containers in interim storage facilities at 16 different sites. The interim storage facilities are designed for a service lifetime of 50 years (operating lifetime 40 years).

Due to delays in the site selection for the construction of the final underground repository for high-level nuclear waste, it will unavoidable to keep the interim storage facilities operating much longer than originally planned. Impacts from environmental conditions (wind, humidity, temperature, etc.) will cause increasing damage to the interim storage structures during their lifetime. Therefore, the safe use especially beyond the planned lifetime of the interim storage facilities requires a detailed condition assessment and monitoring.

The objective of the research project is to develop a condition assessment and monitoring concept, including a life prediction model, for predicting and monitoring the remaining useful life of building structures for interim storage facilities. The research project includes the following aspects:

• Identification and quantification of damage processes and descriptive damage models
• Selection of suitable monitoring and measurement techniques to record the damage processes
• Creation of a measurement-based prediction model for the service life of interim storage facilities using measurement data
• Acquisition, management and evaluation of measurement data with interfaces to BIM and a digital twin of an exemplary building structure

In addition, existing knwoledge from the monitoring of structural facilities in other fields is to be taken into account and, if possible, adapted to the special requirements of interim storage facilities.

Project funding organisation: Bundesministerium für Umwelt, Naturschutz, nukleare Sicherheit und Verbraucherschutz

Project partners: Bundesanstalt für Materialforschung und -prüfung (BAM), Gesellschaft für Anlagen- und Reaktorsicherheit (GRS) gGmbH

Duration: 3 Jahre (Beginn: 01.08.2023)

Contact person: Dr.-Ing. Thorsten Leusmann

This project aims to develop a Mobile Robotic Rammed Earth system for on-site production with the use of locally sourced materials. An important part of this process is the development of an automated mixing, conveying, and feeding process of the local materials. iBMB is responsible for the characterization and development of a local material that can be used in the Robotic Rammed Earth process.

Project funding organization: Golehm-Initiative

Project partner: Institute for Structural Design (ITE) at the Technische Universität Braunschweig, and Institute of Machine Tools and Production Technology (IWF), at the Technische Universität Braunschweig

Duration: 2 years (start 01.09.2022)

Contact person: Evelien Dorresteijn M. Sc., Dr.-Ing. Thorsten Leusmann, involved scientists: Prof. Dr.-Ing. Dirk Lowke (TU München)

The basic research project "Large Particle 3D Concrete Printing" (LP-3DCP) investigates the applicability of the particle bed 3D printing process with coarse particles in the construction industry. Similar to conventional particle bed 3D printing processes, the LP-3DCP process first applies a layer of coarse particles, which are then locally bound by applying a fine-grain concrete. The application of the fine-grain concrete is carried out by a shotcrete process. These processing steps are repeated until the 3D geometry to be printed is completely produced.

While particle bed 3D printing processes developed so far operate with aggregate in the micrometre or millimetre range, large particles up to a maximum diameter of 63 mm will be used for the particle bed in this project. A robot-assisted shotcrete technology developed at the Institute of Structural Design (ITE) will be used to apply the fine-grain concrete. The aim is to produce free-form, high-strength concrete elements that significantly improve CO2 efficiency by means of recycled aggregate and reduced cement quantities. In this interdisciplinary research project, the fundamental relationships between material technology, process technology and architectural-constructive aspects are being investigated.

Project partner: Institute of Structural Design (ITE), TU Braunschweig

Project funding organisation: Zukunft Bau (https://www.zukunftbau.de) - Federal Institute for Research on Building, Urban Affairs and Spatial Development (BBSR) at the Federal Office for Building and Regional Planning (BBR)

Duration: 18 months (start: 15.08.2021)

Contact persons: David Böhler M. Sc., Dr.-Ing. Inka Mai

Particle-Bed 3D Printing by Selective Cement Activation (SCA) – Particle Surface Functionalisation, Particle-Bed Compaction and Reinforcement Implementation (A01)

The project focuses on the 3D printing of reinforced concrete components in a particle bed. In comparison with other additive manufacturing processes in the construction industry, particle bed 3D printing processes have almost no restrictions in the choice of geometry and enable a high resolution. In order to significantly improve the functional and mechanical performance of printed elements, the multi-material powder bed printing technique is fundamentally investigated in this project. Besides the shape accuracy and resolution of the components, the homogeneous mechanical property is one of the biggest challenges regarding the applicability of particle bed techniques in 3D printing. Therefore, the project aims at an in-depth process and material understanding. For this purpose, the fluid intrusion process and the contacts between particles and their layers in the powder bed as well as between particles and reinforcement will be investigated. Particles and reinforcement will be tailored to their process engineering requirements. Special focal points are the functionalisation of the particle surface, the compaction of the particle bed, the fluid infiltration into the particle bed, the active structural build-up of the matrix and the formation of the interface between the particle bed layers and between reinforcement and matrix.

Project partner: Institute for Particle Technology (TU Braunschweig)

Contact persons: Friedrich Herding M. Sc., Dr.-Ing. Inka Mai

Integrated Additive Manufacturing Processes for Reinforced Shotcrete 3D Printing (SC3DP) Elements with Precise Surface Quality (A04)

The aim of this project is to investigate collaborative additive manufacturing processes for the production of material-efficient and force-flow-optimised reinforced concrete components with precise surface quality and high geometric accuracy based on Shotcrete 3D Printing (SC3DP). The SC3DP technology, which is being developed at the TU Braunschweig at the Digital Building Fabrication Laboratory (DBFL) and the Smart Additive Manufacturing Material Investigator (SAMMI), among others, offers great potential for fully exploiting the new possibilities of additive manufacturing with regard to the production of geometrically complex and structurally efficient large-scale components.

The main objective of this project is to conduct basic research on methods, design tools, materials and processes, as well as research into efficient integration of reinforcement elements. This is intended to enable the production of large-scale concrete elements by means of SC3DP using significantly lower quantities of reinforcement and concrete compared to conventional concrete construction principles.

In order to facilitate the integration of reinforcement and the production of material-efficient components with complex and precise geometry, the aim is to further develop design methods as well as the process and material control. The precise control of material and process parameters as well as high geometric and surface accuracy represent the essential prerequisites for reproducible and automated production of structurally efficient concrete components.

Project partners: Institute of Structural Design, Institute of Machine Tools and Production Technology (TU Braunschweig)

Contact person: Niklas Freund, M. Sc.

Transdisciplinary research on the disposal of high-level radioactive waste in Germany (TRANSENS)

Ability to act and flexibility in a reversible process (TAP HAFF)

Path dependency as a risk and challenge for the design of above-ground structures at the repository site

In TRANSENS, research is transdisciplinary. The interested public and other non-academic actors are integrated into research contexts and transdisciplinary work packages (TAP) in a planned manner.

Flexibility instead of a linear process flow: step-by-step procedures, checkpoints in the process, the option of sensible steps backwards and the reaction to new research results are the topics in the transdisciplinary work package (TAP) HAFF.

The iBMB analyzes above-ground storage concepts for high-level radioactive waste and develops ideal-typical concepts for above-ground facilities of deep repositories in a transdisciplinary procedure, consisting of an entrance storage facility with conditioning plant as well as its infrastructure and the structural transport infrastructure underground.

The most appropriate concepts are visualised in 3D in an interactive virtual environment (VR). In the design of the concepts, the focus is on monitoring, retrievability, life cycle assessment and construction costs. An essential element is an adaptive life cycle management system that can be used to assess the current structural condition of the infrastructure at any time. This information can then be taken into account at any stopping points in the further decision-making process.

Project funding organisation: Bundesministerium für Wirtschaft und Energie

Research institutions involved in the project:

TRANSENS is a collaborative project in which 16 institutes or subject areas from nine German and two Swiss universities and research institutions are working together.

Funding period/ duration: 01.10.2019 until 30.09.2024

Contact person: Sina Bremer M. Sc.

The project addresses the issue of particle bed 3D printing (PB3DP) and proposes an innovative numerical approach to simulate and predict the printing process. One of the most promising particle bed 3D printing processes is Selective Paste Intrusion (SPI). This process is based on the local introduction of a fluid (cement paste) into a particle bed (aggregate) and its subsequent solidification and hardening. The main advantage of this technique is the high resolution and the possibility to produce almost arbitrarily shaped components. So far, this technique has been successfully applied to small and medium scale objects with strengths up to 70 N/mm². However, in order to realize a successful application in the construction industry, fundamental questions still need to be addressed. Suitable models for describing and predicting the printing process are therefore essential.

The aim of this project is to numerically investigate the process of PB3DP and to predict the penetration of the fluid into the particle bed. Based on the experimentally determined input parameters, such as the rheological properties of the penetrating fluid and the permeability of the particle bed, the final penetration depth, which determines the quality of the printed part (mechanical properties, durability and geometric precision), will be predicted. The result should be a numerical tool that can simulate and predict the printing process. The tool will be able to predict and optimize the flow of the cement paste in the process.  The originality and innovation potential of the research approach is based on two features: (I) description of the particle bed as a porous medium and (II) explicit consideration of the structural build up caused by thixotropy. To achieve the above-mentioned objectives, fundamental research regarding (a) the specific characterisation and control of the rheological properties of cement pastes for PB3DP, (b) the packing and permeability properties of the particle bed and (c) the numerical methods for the simulation and prediction of the printing process is necessary.

Project funding organisation: German Research Foundation (DFG)

Research institutions involved in the project:  BAM, Berlin

Funding period/ duration: 01.08.2019 until 30.11.2021

Contact person: David Böhler M. Sc., Dr.-Ing. Inka Mai

For the first time, architects, epidemiologists, hygienists, material scientists and building technicians will work together in an interdisciplinary way under the leadership of the Institute for Structural Design, Industrial and Health Construction (IKE) at the TU Braunschweig. The aim of the collaborative project is the cross-sectoral assessment of risk factors for the transmission of infections on the basis of existing infrastructures worthy of protection and the associated identification of procedural processes. These are brought together and weighted in an overall assessment in order to derive tangible recommendations for action to interrupt the spread of infection for the areas of construction, materials and building services. Selected model solutions for specific problems that are likely to have a significant influence on the interruption of infection transmission pathways will be developed and presented in the first half of the project.

At the end of the project, all recommendations are to be compiled into a "White Paper on the Structural Infection Prevention of Critical Infrastructures". The publication will take place via open access and a website that will be permanently accessible free of charge.

The iBMB measures the mechanical, physical and chemical impact on commonly used surfaces in critical infrastructures. The results are intended to provide an overview of the durability and change in surface condition with regard to cleansability.

Project funding organisation: Federal Institute for Research on Building, Urban Affairs and Spatial Development (BBSR) within the Federal Office for Building and Regional Planning

Project partners: Institute of Construction Design, Industrial and Health Care Building (IKE) Technische Universität Braunschweig, Hermann-Rietschel-Institut (HRI) Technische Universität Berlin, Charité – Universitätsmedizin Berlin

Duration: September 2020 – März 2022

Contact person: Jens Brack M.Sc., Dr.-Ing. Inka Mai

Rheology of reactive, multiscale, multiphase construction materials (DFG SPP 2005)

The processing of mineral building materials is the technological core in the production and maintenance of buildings. However, the lack of a scientific basis for mastering rheology-based processes is a key obstacle in the development of new, highly innovative construction technologies, such as 3D printing with concrete, and in formulating solutions for current technical challenges, such as pumping at extreme heights.

The reason for the lack of rheological fundamentals resides in the very high complexity of cementitious systems. The high chemical reactivity of mineral binders leads to changes in particle morphology, the dissolution of larger cement grains and the formation of new nanoscale particles as well as to significant changes in the carrier fluid chemistry only a few seconds after the addition of water. Both the newly formed nanoparticles and the carrier fluid interact in turn with granular raw materials of up to several centimetres in size.

Cement suspensions are complex multiphase systems that contain water and various mineral particles, as well as organic admixtures and air voids. Eventually, the placement and processing of cementitious materials takes place under an enormous range of deformation speeds, which impose extremely high demands on characterisation and simulation methods.

The aim of the priority programme is to determine and describe the scientific basis for the understanding and targeted control of rheology-based construction processes as well as for the development of innovative, sustainable building materials and associated future-oriented processing technologies.

Project funding organisation: German Research Foundation (DFG)

Duration: February 2021 - January 2024 (DFG SPP 2005 - funding phase 2) www.spp2005.de

Rheology of low clinker concretes with tailored superplasticizer polymers - Control and modelling of viscosity and thixotropic structural build-up

This project aims to understand and describe the decisive effects of the molecular structure of PCE superplasticizers on viscosity and thixotropic structural build-up of low clinker concretes (LCC) in order to derive rheological material laws to control technological processing in practice. The key element here is the explicit characterization of the particle microstructure in the binder suspension under quantitative consideration of both the colloidal interparticle interactions and the very early hydration kinetics.

Reducing the clinker content in cement and concrete is a promising way to reduce the CO₂. Therefore, modern concretes are increasingly characterized by low clinker content and high content of supplementary cementitious materials (SCM) such as ground limestone, ground granu­lated blast-furnace slag or calcined clays. Given the high specific surface area of SCM, especially of calcined clays, on the one hand, and the increased requirements for modern concretes in terms of easy workability on the other, the addition of superplasticizers is essential.

Although some PCEs were found to effectively disperse particles in calcined clay blended cements, a high viscosity and respectively stickiness was observed. This is not a surprising fact, since boundary conditions regarding particle surface charge, ions in the liquid phase, solid content and particle size distribution differ significantly from OPC systems. Therefore, to control concrete fresh properties, a comprehensive understanding of the effect of PCE molecular structure on viscosity and thixotropy in low clinker binder systems with high amounts of SCM is important.

In this research, tailored superplasticizers with varying side chain length, side chain density and backbone length will be investigated. Both, viscosity and the thixotropic structural build-up will be determined, not only on paste but also on mortar and concrete. This is an important step, as the upscaling can significantly change the behaviour of plasticized cementitious materials.

Additionally, the colloidal interparticle interactions, hydration kinetics as well as the particle microstructure will be quantified. Based on FBRM-coupled rheology to determine the in-situ agglomerate size, a microstructural model for viscosity and the thixotropic structural build-up at rest will be developed. The novelty of this model is that it specifically captures the particle microstructure of the binder suspension, thus bridging the gap between effects at the nano scale (PCE molecular parameters, colloidal interactions, hydration) and the macro scale (rheological properties). To exploit the full potential of LCC for future applications, easy workability and robust fresh concrete properties are key requirements. This aspect in focus, the model will allow for a comprehensive control and prediction of the mechanisms that significantly affect viscosity and thixotropy of LCC.

Project partner: Dr. rer. nat. Daniel Jansen, FAU Erlangen (GeoZentrum Nordbayern, Chair of Mineralogy)

Contact person: David Nicia M.Sc., Prof. Dr.-Ing. Dirk Lowke

From micro to macro – fundamental concrete modelling considering local shear rate and microstructure inhomogeneities due to processing using a scale-bridging approach

During processing, e.g. pumping, casting or slip-forming, concrete flow behaviour is determined by the rheological properties of a) the bulk material and b) the interface layer near the wall. Hence, modelling the macroscopic flow behaviour of concrete or other cementitious suspensions during processing requires a clear description of the mechanisms forming the interface layer as well as of rheological properties of bulk and interface material. Therefore, the shear induced particle migration (SIPM) has to be taken into account as a dominating mechanism, with larger particles migrating from regions of high shear rates to regions of lower shear rates. Another key issue is upscaling from cement paste to mortar or concrete modelling. Nowadays, fundamental models based on chemical and physical particle interactions mostly exist for cement paste, whereas existing concrete rheology models are largely based on continuum mechanics or Discrete Element Method (DEM) and validated based on empirical data.

The goal of the present project is to investigate and model macroscopic concrete flow behaviour with regard to both, the influence of the interface layer at the wall and the particle interactions, being the key issues for fundamental modelling of concrete rheology. To consider the effect of particle interactions on the macro-scale rheological models, the problem of upscaling from cement paste to concrete level has to be solved in the first place. The rheology of cement paste highly depends on its microstructure, which is determined by the shear history and hydration effects. Hence, fundamental rheological models must consider effects on microstructure formation. However, shear rates acting on cement paste at concrete level are largely unknown. In fact, the real shear rate acting on cement paste at concrete level is significantly higher than the global, i.e. macroscopic, shear rate. This so called local shear rate acting on cement paste in concrete is determined by the particle packing (distance between larger particles, i.e. sand and gravel) and the relative velocity of two adjacent large particles. As (specifically) larger particles are subject to SIPM, leading to severe inhomogeneous particle distributions at the macro-scale, the local shear rates are also varying depending on the actual solid concentration and particle size distribution in a certain volume increment. Therefore, the aim of the present project is the investigation and modelling of time- and shear-dependent microstructure (disperse properties) and rheological properties of cementitious suspensions subjected to shear. In this project, the addressed key issues are a) SIPM, b) interface layer and its formation mechanisms, c) local shear rates induced by larger particles and d) its effect on microstructure and rheology taking chemical and physical based particle-particle interactions into account. Only a scale-bridging approach from the micro-scale (d_particle<100 µm) over the meso-scale (0.1≤d_particle≤4 mm) to the macro-scale (d_particle>4 mm) enables to adequately achieve this goal.

Project partner: Prof. Dr.-Ing. Carsten Schilde, iPAT, TU Braunschweig

Contact person: Mahmoud Eslami Pirharati M. Sc., Dr.-Ing. Inka Mai

The aim of the project is to quantify and present the industry-relevant potential and performance of additive manufacturing processes in reinforced concrete construction using Shotcrete 3D Printing (SC3DP) as an example. For this purpose

• production time
• production costs (e.g. personnel, energy, equipment) and
• durability properties of the material

are determined for an additively and a conventionally produced reinforced concrete component with different geometric complexity.

These data allow an initial evaluation of the competitiveness of additive manufacturing in the field of reinforced concrete construction and thus represent an important basis for future industry-oriented research and development strategies in concrete construction.

Project funding organisation: Deutscher Beton- und Bautechnik-Verein E.V., DBV (www.betonverein.de)

Project partner: Institute of Structural Design (ITE), TU Braunschweig

Duration: 2 years (start: 01.08.2020)

Contact person: David Böhler M. Sc., Dr.-Ing. Inka Mai

In this project, a sensor-based and web-based diagnosis and monitoring system is to be developed to analyze ASR (alkali-silica reaction) damage to traffic and engineering structures and to determine the development of damage progression and remediation measures. For this purpose, a valid measuring method and system for the recording and analysis of structure- and rehabilitation-specific parameters is to be developed. The technical development goals within the R&D project include a high degree of innovation and a high technical risk.

The main tasks of the TU BS in the present R&D project include, on the one hand, the determination of the influencing factors and technical parameters of an ASR damage process by means of a laboratory test set-up to be newly developed. On the other hand, the development of algorithms for the filtering and analysis of the monitoring data, as well as the participation in the validation of possible sensor systems for the envisaged monitoring system. There are close interfaces to the two cooperation partners IMF and ME, which will be discussed in the following description of the work.

The development of ASR characteristics, i.e. the determination of the influencing factors and technical parameters for the analysis and prognosis of the damage process, is carried out in subproject B of the TU BS by simulation of ASR damage on a laboratory and pilot plant model. In subproject A of IMF, comparative characteristic data of the ASR damage progression between rehabilitated and non-rehabilitated areas on the object are determined in practical tests. From this, together with the ASR damage responses and impact factors investigated by TU BS, mathematical models will ultimately be derived to determine a suitable repair timing and recommend a rehabilitation system.

Project partners: Institute for Materials Testing and Research GmbH (IMF)
                              Müller-electronic GmbH (ME)

Project funding organisation: AiF Projekt GmbH, Central Innovation Programme for SMEs (ZIM) of the BMWi

Duration: 3.5 years

Contact person: Sina Bremer M. Sc.

Civil engineering structures are designed and built for use according to plan during life-time. The design is usually performed under the assumption of an ideal state of structures and building materials during the total life-time. Actually the state of materials and thus the properties of buildings are changing over the period of use, what may influence the reliability and quality of the building during life-time and may lead to a reduction of safety with respect to loads and usage. The evolution of the properties of building materials and structures may be caused by physical or chemical reasons and takes place on different spatial and temporal scales.

Goal of the research programme is the development of scientific approaches to describe and to evaluate the changing of properties and quality of buildings and infra-structures with respect to physical and chemical effects. The multi-coupled processes, which are responsable for the evolution of building materials, will be described by model equations on different spatial and temporal scales within the theory of continuum mechanics and the theory of porous media. The models will be the basis for prognoses of the development of building materials and structures.

The multi-scale models describe the different phenomena of aging as a coupled process, what needs a direct coupling of the single processes in space and time, in order to consider the interaction of processes and to integrate all information for an evaluation of the quality of buildings. In an extension of the current approaches on the macroscopical scale, the mechanisms of transport as well as physical and chemical damage shall be investigated experimentally and shall be modelled on different scales of materials and buildings. Based on experimental and numerical investigations simplified engineering approaches shall be taken into account, which can be realized to practice.

The scientific training of the doctoral-students follows a structured programme of workshops, seminars and publications, whereas the individual work will be honoured by credits. The programme contains scientific experiences in the field of experimental work, mathematical modelling of processes and structural analysis, and the training of key skills in the field of scientific work and scientific management. Based on the broad education regarding different building materials the doctoral-students will get the possibility to understand and to evaluate completely different phenomena and to describe them by advanced models for life-time-prognosis of civil engineering structures.

Further information on the Research Training Group: https://www.tu-braunschweig.de/en/grk-2075

Spokesperson: Prof. Dr.-Ing. Manfred Krafczyk

Institutes involved: Institutes of the TU Braunschweig of the Faculty of Architecture, Civil Engineering and Environmental Sciences as well as the Carl-Friedrich-Gauß-Faculty, the Fraunhofer Institute for Wood Research and the LU Hannover

Funding period / duration: 4.5 years

Funded by: German Research Foundation (DFG)

Ageing influences on the interaction of embedded reinforcement and externally bonded carbon fibre lamellae in reinforced concrete components

Ageing, material fatigue and the increased traffic load on many concrete bridges on federal trunk roads in Germany necessitate restoration or strengthening measures. An economical method of strengthening reinforced concrete components is to use bonded reinforcement made of carbon fibre reinforced polymer (CFRP). The externally bonded reinforcement increases the load-bearing capacity of the aged concrete components and thus causes an extension of the service life. The load-bearing effect of this rehabilitation measure is mainly influenced by the adhesive bond between the bonded carbon fibre polymer and the concrete. However, the adhesive bond is considerably affected by environmental influences, ageing phenomena and fatigue damage over the period of use. To ensure the stability of these reinforced components, the load-bearing capacity of the adhesive bond must be ensured. The investigation and modelling of the composite load-bearing behaviour are crucial for concrete components reinforced with bonded CFRP lamellae.

The aim of the research project is to determine the internal forces in concrete, steel and bonded reinforcement of a reinforced concrete component under steady states of stresses. In this context, approaches have to be developed to determine the force distribution between inserted and bonded reinforcement, considering different bond ratios.

Experimental investigations on mixed reinforced concrete beams will serve as the basis for modelling the time-dependent composite load-bearing behaviour of different reinforcement strands as well as the degradation behaviour of the concrete. Furthermore, state-of-the-art fibre-optic measuring systems will be used to record the strain states of the reinforced component throughout the period of investigation.

With the description of the time-dependent material behaviour and the degradation models of the composite load-bearing behaviour, it will be possible to create a prognosis model that is able to make a statement about the residual load-bearing capacity of the reinforced structure.

Contact person: Zhuo Chen M. Sc.

Influence of mechanical properties of materials on the durability of repaired reinforced concrete components

In a classic concrete repair, the damaged concrete is removed and re-profiled with a repair mortar or concrete. After such a repair, a structural element is usually considered to be as good as new. A detailed statement on the remaining service life of a repaired reinforced concrete component was not possible until recently. However, this is of great interest to the owner or user of a reinforced concrete structure from an economic point of view.

As a result of two research projects at the Technical University of Munich, it has now been possible to transfer the approach to probabilistic lifetime design according to Gehlen into a semi-probabilistic, and thus strongly practice-oriented approach. It is now possible to calculate the remaining service life of a reinforced concrete component with regard to carbonation-induced and chloride-induced corrosion, depending, among other things, on the weather conditions, the applied mortar layer thicknesses and the material-specific resistance to chloride penetration and carbonation.

The basis of the calculation approaches is Fick's 2nd law, which describes the diffusion mechanisms and allows a material-specific estimation of the penetration behaviour of liquids and gases into the concrete on a chemical level. The ageing of a component and its material resistance to chemical attack is taken into account in the case of carbonation using the root-time approach and in the case of chloride penetration by adjusting the chloride diffusion coefficient using an experimentally determined age exponent.

The influence of mechanics on the description of aging processes in a repair layer has not been integrated in the current models for lifetime design so far. The need for research in this area becomes clear when considering the controllability of stress distributions between repair material and old concrete via the variation of the Young's modulus in the repair layer. A soft system avoids the load, while a stiffer system relieves the old concrete and takes over the load transfer itself. As a result of deformations, micro-cracking of the hardened cement paste matrix occurs long before the formation of cracks visible to the eye. This is accompanied by a change in the material resistances relevant to durability.

The aim of the work is therefore to determine ideal combinations of mechanical parameters between old concrete and repair material, initially on the basis of laboratory tests and depending on numerous variables (e.g. class of old concrete, geometry of concrete repair, load scenario, modulus of elasticity, strength) in order to achieve the longest possible service life. The stress distribution in the cross section of the component and also on the composite joint is to be considered. In the following, these considerations will be linked to investigations on the influence of mechanical ageing on the chloride diffusion coefficient.

Contact person: Dipl.-Ing. Stefan Ullmann

Crack initiation along the bonded joint between concrete and CFRP laminates

The rehabilitation of aged buildings and infrastructure projects has become increasingly important in civil engineering. Engineers often have to deal with old buildings that require retrofitting. A material that meets the requirements for reinforcement, is easy to process and has good mechanical properties is carbon fibre reinforcement plastic (CFRP). An important point of reinforcement is to check the adhesive bond between the concrete and the slats because the bond failure, called decoupling, is brittle and occurs without notice. In the course of previous investigations, a possible correlation between cracking and a coefficient of the bond that depends on the fracture energy was found. Cracking has so far been represented by roughness parameters, but the factors influencing cracking are still the subject of research.

The aim of the project is to investigate the properties of concrete that can be decisive for the formation of cracks. The parameters to be investigated are the mechanical properties of the aggregate and the cement paste as well as the shape and grain distribution (grading curve) of the aggregate. The research programme will be divided into two parts. First, attention will be paid to the small scale (mesoscale) to better understand the mechanisms. In this part of the research, the focus will be on the examination of the samples using micro CT and the subsequent analysis (segmentation and reconstruction) of the images. The knowledge gained will be validated in further experiments in the second phase of the project. Here, experiments on the macro level are planned in particular, in which samples are subjected to cyclic loading. Based on the results of the experimental programme, an engineering model applicable in practice will be developed.

Contact person: Matteo Lunardelli M. Sc.

Mesoskalen-Modellierung der Riss-induzierten Durchlässigkeit von Beton

Cracking due to tension in concrete is characteristic for reinforced concrete construction. In the case of macro cracks even small crack widths are able to impair the durability of struc- tures. In particular, the prediction of water transport focus great interest in practice. The influence of crack width on flow rates has been investigated in several researches.

Nowadays the fluid transport coul d be estimated considering crack opening and roughness of the crack surface. A flow law, which is often used because of its simplicity is the cubic law (q = (ξ∙g∙I∙b∙w³)/(12∙ν) [m³/s]).

The goal of the project is to improve the approach taking into account other important parameters of the material like concrete strength and concrete mixture. The degree of reinforce- ment and the element thickness are import ant factors as well.

Several experiments are planned. At first a permeation test of reinforced c oncrete samples with a specific crack width at the sample surface will be performed. Wedges will be pushed into the concrete sample in order to induce crack between 0,1 and 0,3 mm. In the first step the fluid will be water, in further steps also corrosive fluids will be investigated. Furthermore, several values like the used aggregates and w/c-values and concrete mixtures will be varied. To determine the effect of selfhealing of cracks the permeation test will be carried out as a short term and as a long term experiment. Micro-CT investigations will be carried out on cores drill ed from the permeation test samples. The crack will be filled with epoxy resin before x-rays measure ments to fix the crack pattern and get detailed information of the crack geometry. To estimate the roughness, the samples fractured surfaces will be analyzed with a digital microscope.

Approaches to develop the cubic law are:

• Stochastic description of cr ack path and roughness of the crack surface,
• Stochastic description of the crack width through the component thickness,
• Description of the concrete permeability by taking into account the influence of macro cracks. A computational description model is plan ned b esides the mentioned experiments,
• The experimental and computational results will be used to express a finer and more extensive description of the fluid transport for cracked porous structures for the practical applications.

Publications within the framework of the RTG:

Conference contribution with publication in conference proceedings:

L. Mengel, D. Köhnke and H. Budelmann. Radiation effects on concrete. Research on Radioactive Waste Management, Ethics - Society - Technology. Final ENTRIA Conference, Braunschweig, September 2017.

Contact person: Lena Mengel M. Sc.

The aim of the project is to develop a clay-based material that can be used to extrude/print a durable formwork for the production of a concrete column. An advantage of this manufacturing process is that it is environmentally friendly since the clay-based material can be reused, and besides, it allows a high degree of freedom in the design of a mold. The main objective of the TU Braunschweig is the development of the clay-based material, where the material should have sufficient green strength while maintaining the processability of the material. The project is being carried out in collaboration with the TU Munich (Germany) and the USI in Mendrisio (Switzerland), where the overall concept and robot path planning are being developed.

Project funding organization: DFG, AMC TRR 277, SNSF

Project partner: Institute of Digital Fabrication, Technical University of Munich and Universita Svizzera Italiana, Accademia di Architettura, FMAA, Switzerland

Duration: 1 year (start: 01.12.2022)

Contact person: Evelien Dorresteijn M. Sc.

Development of concretes with low global warming potential, good workability, strength and durability from locally available raw materials.

The objectives of the project are:

• the development of concrete formulations with a significantly improved ecological balance with the same technical performance (workability, strength and durability) compared to solutions based on the current state of the art.
• the development of a new model to describe the technical performance of eco-concretes.
• the development of methods for the combined technical and ecological assessment of concretes in relation to the construction task, taking into account the entire life cycle.

At the same time, existing hurdles to the market acceptance of eco-concrete are to be overcome with the help of an innovative, practice-oriented recipe development concept. The existing hurdles include:

• the high material costs resulting from the complex requirements for the concrete constituents of classic eco-concretes (and thus also impairing the environmental balance).
• the difficult workability of eco-concretes due to their very high viscosity.
• the often lower technical performance of eco-concretes, especially with regard to some durability aspects. Finally, the material and methodological solutions developed within the framework of this project are to be validated using two concrete construction tasks as examples.

Participating institutes: Braunschweig University of Technology, Institute for Building Materials, Solid Construction and Fire Protection (iBMB), Department of Building Materials and Bochum University of Applied Sciences, Department of Architecture, Chair of Building Physics and Energy-efficient Construction,

Funding period / duration: January 2021 to December 2022 (2 years)

funded by: Dres. Edith and Klaus Dyckerhoff Foundation

Contact: Jens Brack M.Sc.

The aim is to establish a device infrastructure ("RheoStruc3D Lab") for the integral characterisation of the rheological properties and the microstructure of materials during processing in additive manufacturing (3D printing) in the construction industry. The "RheoStruc3D Lab" represents a research infrastructure that is unique in Germany and Europe and offers excellent new research opportunities for investigating and describing relationships between the properties of cement-based material systems and their structure and rheology in the various process steps in additive manufacturing that have been insufficiently established to date. The aim is to develop the scientific and technical foundations for the development of innovative materials and the optimisation of the individual process steps for additive manufacturing in the construction industry, with special consideration of the procedure-material interaction.

The investment in the new device infrastructure includes:

1. Probe for laser-optical determination of the microstructure and particle size distribution of fresh, non-hardened solid suspensions
2. Precision rheometer for the characterisation of shear rate-dependent rheological properties with integration of the probe from 1
3. High-performance laboratory mixer for mixing and homogenising suspensions
4. Laboratory multiprocess 3D printer for cement-based materials to facilitate the transfer between basic research and applied research on a semi-technical and technical scale

In accordance with Section 19 (2) VOL/A, information is provided on the contract procurement:

Re 1: The contract for a ParticleTrack G400 laser-optical probe was awarded to Mettler-Toledo in July 2018.

Re 2: The contract for an MCR 502 rheometer was awarded to Anton Paar in March 2018.

Re 3: The contract for a high-performance Eirich R08W laboratory mixer was awarded to Dyckerhoff in June 2018.

Re 4: The contract for a 3D particle bed printer for mineral materials was awarded to a company for machinery [&] automation in Italy in September 2019.

Project funding organisation: NBank/EFRE

Duration: 01.01.2018-31.12.2019

Contact person: Dr.-Ing. Inka Dreßler, Dr.-Ing. Hans-Werner Krauss

The processing of mineral building materials is the technological core in the production and maintenance of structures. Although their malleability in the fresh state offers almost unlimited possibilities in terms of building design and execution technologies, only a fraction of this enormous potential is used today. The reason for this is that traditional, simple component geometries such as walls or ceilings can supposedly be "cast" solely on the basis of empirically obtained rule. This illusion is a reason for the lack of in-depth study of the rheological behaviour of building materials. However, an extremely high number of structural damages, a low efficiency of construction processes and problems with the use of changing building material compositions and processing techniques prove the glaring deficits of this empirical approach. The lack of a scientific basis for mastering rheology-based processes, however, is above all a central obstacle in the development of new, highly innovative construction technologies, such as 3D printing with concrete, as well as in finding solutions to current technical challenges, such as pumping at extreme heights.

The second reason for the lack of rheological fundamentals is a very high complexity of the building material systems. The pronounced chemical reactivity of mineral binders leads to a strong change in particle morphology, the dissolution of larger and formation of new, nanoscale particles and a drastic change in the chemistry of the carrier fluid only seconds after the addition of water. Both the nanoparticles formed and the carrier fluid in turn interact with granular starting materials up to several centimetres in size (multiscale). Furthermore, building material suspensions are always complex multiphases that contain organic additives and air voids in addition to water and a wide variety of mineral particles. Finally, the processing of building materials is characterised by an enormously wide range of deformation rates, which in turn places extremely high demands on characterisation and simulation methods.

The aim of the proposed SPP is to create the scientific basis for a rheology-based design of building processes and for the development of new, sustainable building materials and groundbreaking processing technologies.

This approach, which is completely new in the building industry, will lead to a significant increase in the economic efficiency and sustainability of construction through the reliable exclusion of manufacturing-related damage as well as the efficient use of materials, technology and energy, and opens the door to new building forms and construction methods.

The high complexity of the scientific question requires a broad bundling of competences from engineering and natural scientists. Due to current advances in the field of relevant measurement technology and simulation methods, an SPP offers ideal framework conditions, especially at the present time, for successfully researching the complex of topics described.

Weitere Informationen zum Schwerpunkprogramm: http://www.spp2005.de/

Spokesperson: Prof. Dr.-Ing. Viktor Mechtcherine, Institute of Construction Materials, TU Dresden

Participating institutions:Friedrich-Alexander University Erlangen-Nuremberg, Technische Universität Berlin,Karlsruhe Institute of Technology (KIT), Technische Universität Bergakademie Freiberg, University of Stuttgart, Technical University of Munich, Technical University of Darmstadt, Technische Universität Braunschweig, Federal Institute for Materials Research and Testing (BAM), Gottfried Wilhelm Leibniz Universität Hannover, Technische Universität Dresden, Bauhaus-Universität Weimar,  Friedrich Schiller University Jena, Leibniz Institute of Polymer Research Dresden e.V., Paderborn University

Project funding organisation: German Research Foundation (DFG)

Funding period / Duration: 3 years

Superplasticizer/Particle Interactions and its Effect on Microstructure, Viscosity and Thixotropy of Cementitious Suspensions

To understand the fundamental mechanisms of properties of fresh cementitious materials, systematic research is required on the relationship between microstructure and the rheological properties of fresh cement paste. The aim of this research is to examine the effect of superplasticizer / particle interactions on the microstructure, viscosity and thixotropic structural build-up of cementitious suspensions.

Understanding the internal structure of cementitious suspensions is not an easy task due to polydispersity, opaqueness, high solid fraction and hydration reactions. Thus, there is a lack of fundamental understanding of the intrinsic structure of fresh cement paste which is of great importance for the workability of concrete. Furthermore, the initial fresh state microstructure affects the microstructure of the hardened paste and consequently strength and durability. The microstructure of a cementitious suspension is determined by the interparticle interactions. In simple terms, particles agglomerate when attractive interactions exceed repulsive interactions. Therefore, understanding the effect of superplasticizer on microstructure and obtaining a reliable estimate of the interparticle interactions in cementitious suspensions is a crucial step towards understanding the rheological properties.

In this research, pastes and mortars will be prepared using specifically polymerized superplasticizers with either phosphonate or polycarboxylate functional groups and variations in backbone length, side chain length and side chain density. Viscosity and thixotropic build-up will be determined using rotational rheometry. Simultaneously, the evolution of microstructure is observed with an in situ laser backscattering measurement device (Dynamical Optical Reflectance Measurement with Selective Multi Depth Focus). Whereas, the kinetics of structural break-down in dependence of shear load is not addressed in this research. Finally, the effect of superplasticizer technology on microstructure as well as viscosity and thixotropic structural build-up will be discussed on the basis of colloidal surface interactions, hydration kinetics and a microstructural model.

Contact person: David Nicia, M. Sc.

Simulation based modelling of time- and shear-dependent disperse and rheological properties of cement suspensions

The aim of the project is to develop enhanced constitutive models for the prediction of rheological properties of cementitious materials based on chemical and physical particle and fluid characteristics. Due to its fundamental basis the modelling approach exhibits a general validity and applicability. Bridging the gap between fundamental insights into chemical and physical processes at nano as well as micro scale and the macroscopic flow behavior, the project makes a contribution for overcoming limitations of existing constitutive rheological models. Thereby, a more reliable simulation and modelling of concrete flow even for complex processing steps with time-variant shear history, such as pumping, 3D printing or spraying, is enabled. To that end, the time- and shear-dependent disperse and rheological properties of cementitious suspensions are investigated and modelled based on fundamental material properties and interactions with the help of coupled CFD-DEM simulations. With the help of the simulations, the basic interactions depending on numerous chemical and physical particles and fluid characteristics, mixture composition and processing parameters can be modelled comprehensively for the first time. New time-dependent contact models are developed and used for the coupled CFD-DEM simulations. The results of the simulation environment are calibrated and validated by different experiments. The properties of particles and fluid relevant for the simulations are investigated in cooperation with other working groups. Therefore, different reacting and non-reacting technical and model particulate systems are used. The disperse and the rheological properties of the suspensions are characterized comprehensively. Relevant particle and fluid characteristics are investigated by rotational and oscillation rheometer tests. The microstructure effect on the rheological properties is described by the particle agglomeration behavior. Therefore, the agglomeration state and the rheological properties are characterized for different shear rates, time steps and shear histories with and without regard for hydration effects. The particle size distribution and the agglomeration state of the pastes are determined under shear conditions by a laser backscattering method integrated into a new coaxial cylinders rheometer setup. Based on the simulation and experimental results the time- and shear-dependent microstructure effects are implemented into existing constitutive models enabling the consideration of thixotropic effects and ageing effects due to cement hydration. Being a key parameter for constitutive models and multi-scale modelling, a special focus will be on the determination of local shear rates acting on the paste phase. The approach enables to capture realistic shear parameters for the simulations and experiments at micro scale, hence allowing a more reliable scale-up and modelling.

Contact person: Mahmoud Eslami Pirharati, M. Sc.

Each year, approximately 600,000 patients succumb to a nosocomial infection, an illness that first occurs during a stay or treatment in a hospital. The high number of hospital infections depends on many factors, including suitable structural and functional conditions and operational measures. Whilst at a higher level the spatial arrangement can be adapted to processes from the point of view of minimising the risk of infection and the technical equipment can also be optimised, at a smaller level the choice of materials is a further factor in achieving an optimal hygienic design.

The materials used in hospitals are, on the one hand, typical building materials such as plaster, masonry, dry construction materials or wall and floor coverings that come into little or at least only indirect contact with staff and patients. On the other hand, there are also furnishings, fittings and trimmings of windows, doors or in the sanitary area, which are always in direct contact. Depending on the respective place of use, the materials are assigned to certain environmental conditions and are classified. Furthermore, essential material properties are to be investigated that are very likely to determine the colonisation and spread of germs on surfaces.

The aim is to ensure that hospitals are hygienically safe through a clever choice of materials and thus to reduce nosocomial infection rates.

Project funding organisation: Federal Office for Building and Regional Planning in the framework of the research initiative "Zukunft Bau"

Research institutions involved in the project: 

Institute of Construction Design, Industrial and Health Care Building at  Technischen Universität Braunschweig

Funding period/ Duration: 01.09.2014 - 31.10.2016

Contact person: Dr.-Ing. Inka Dreßler

Publications:

• Sunder, W.;  Holzhausen, J.; Gastmeier, P.;  Haselbeck, A.; Dreßler, I.: Zukunft Bauen: Forschung für die Praxis, Band 13: Bauliche Hygiene im Klinikbau - Planungsempfehlungen für die bauliche Infektionsprävention in den Bereichen Operation, Notfall- und Intensivmedizin. Hrsg.: Bundesinstitut für Bau-, Stadt- und Raumforschung im Bundesamt für Bauwesen und Raumordnung. 2018, 76 Seiten.
• Dreßler, I.; Jin, X.; Budelmann, H.; Kasal, B.: Zusammenhang von Adhäsion und Reinigung von Mikropartikeln auf strukturierten Oberflächen. In: Chemie Ingenieur Technik 2018, 90, No. 3, 8 Seiten.
• Dreßler, I.: Hygienesichere Oberflächen im nicht-immergierten System. Dissertation TU Braunschweig, 2018.
• Dreßler, I.; Holzhausen, J.; Sunder, W.; Budelmann, H.: Prevention of healthcare-associated infections in intensive care units - potential for improvement due to construction design and operational actions. In: Antimicrobial Resistance & Infection Control 2017 6(Suppl 3): 52, p. 162
• Budelmann, H.; Dreßler, I.: Beurteilung der Reinigbarkeit von Oberflächen bei partikulärer Kontamination. In: Chemie Ingenieur Technik 2017, 89, No. 00, 9 Seiten.
• Holzhausen, J., Sunder, W.; Dreßler, I.; Stiller, A.: Bauliche Hygiene: Mit Architektur und Design gegen multiresistente Erreger. In: das Krankenhaus, 12, 2016, S.1130-1132.

High performance concrete allows increasingly lighter, more filigree and resource-saving structures, which are, however, more susceptible to vibrations due to their reduced dead weight. Structures and components such as long-span bridges of high-speed train traffic, wind turbines or machine foundations are also typically subjected to very large variable stresses and very high numbers of load cycles. The fatigue behavior of high-performance concrete is crucial for the design and realization of such concrete applications. Due to the current gaps in knowledge regarding the development and propagation of fatigue damage in high performance concrete, the effective use of modern high performance concrete is hindered.

The aim of this research project is to understand, describe, model and predict the material degradation of high-performance concretes using a combination of the latest experimental and virtual-numerical methods. Since damage processes occur at very small scale levels, they cannot be fully observed in loading tests. Already the acquisition of suitable damage indicators during the test makes the already time-consuming fatigue tests very demanding. In this respect, the desired findings are developed in close interaction between building material science and numerical mechanics, i.e. in the interlocking of experiment and calculation - in the Experimental Virtual Lab. The modeling of the heterogeneous structure of concrete as well as the damage and crack modeling on different scale levels and over several thousand load cycles represent specific challenges in this research initiative.

Further information concerning the priority program: www.spp2020.uni-hannover.de

Project funding organisation: German Research Foundation (DFG)

Duration: 3 years

Contact person: Gauravdatt Basutkar

Multiscale Investigation of Fatigue Crack Development in High Performance Concrete Based on Computed Tomography and Phase Field Modelling

The aim of the project is to analyze crack growth under cyclic loading in high-strength concrete both experimentally and numerically on the mesoscale. The experimental program includes fracture mechanics tests with a few cycles and fatigue tests with up to 2 million load cycles on specimens of different sizes, some of which are performed in a computer tomograph. The mesoscale is defined as the scale at which the concrete constituents aggregate, pores, cement mortar matrix and contact zone (ITZ) are distinguished. Since it is computationally impossible to resolve aggregates and pores of any size scale, those below a suitable size threshold are idealized to be incorporated into the cement mortar matrix and also into the contact zone material. Simulation methods are being developed to describe crack initiation and propagation using a three-dimensional mesostructural model created from CT scans. Computed tomography will also be used for deformation measurement and crack pattern observation, which will be key to validating the modeling results.

The project is located in WG3 Concrete composition/structure.

Project partner: Institute of Applied Mechanics (TU Braunschweig)

Contact person: Gauravdatt Basutkar, M. Sc.

While the topic of "Industry 4.0 - human-robot cooperation" is already being discussed in industrial manufacturing, the construction industry has not even reached Industry 3.0 yet. Digitalisation has already found its way into planning in the form of design, calculation and simulation programmes. However, construction itself has not changed significantly. The high-quality materials and industrially produced prefabricated parts are still processed according to the principle of "brick on brick". Human activity leads to varying component quality as well as cost-intensive work processes. The discrepancy between what can be planned theoretically and what can be implemented in reality is correspondingly high and will continue to increase in the future unless a rethink takes place. Digital fabrication offers a solution that is able to realise innovative designs with increasing component quality and efficient use of resources.

The aim of this interdisciplinary research project is therefore to develop a process for the production of geometrically complex components. In doing so, the use of formwork elements, which determine the shape of the components as well as their economic efficiency, is to be dispensed with. Instead, an innovative, robot-supported manufacturing process is to be developed, which is based on the shotcrete technology known from tunnel construction. To realise the project, findings from the fields of mechanical engineering, computer science and materials science are to be combined with those from civil engineering.

The basis for carrying out the research project is a large-scale research device called "DBFL - Digital Building Fabrication Laboratory". The large-scale device funded by the DFG is unique in its conception and design. Within the workspace, freely orientable processing heads can apply material additively, process high-strength materials subtractively and perform "pick and place operations" cooperatively.

The first phase of the iBMB sub-project deals with the development of a suitable shotcrete formulation for the manufacturing process. In doing so, the shotcrete formulation must be matched to the requirements resulting from an upstream pumping process and the subsequent process of shotcrete application. In a second project phase, the thermal and mechanical component properties are to be modelled.

Project partners:

Institute for Assembly Technology, Leibniz Universität Hannover

Institute of Structural Design (iTE), Technische Universität Braunschweig

Institute of Machine Tools and Production Technology (iWF), Technische Universität Braunschweig

Institute for Building Materials, Solid Construction and Fire Protection (iBMB), Technische Universität Braunschweig

Institut für Informatik Software Systems Engineering, TU Clausthal

Institute of Non-Metallic Materials, TU Clausthal

Project funding organisation: University of Applied Science Nordost-Niedersachsen

Duration: 3 years (2016 – 2018)

Contact person: Niklas Nolte M. Sc.

[Translate to English:]

Das Ziel des Projektes ist die Entwicklung eines innovativen Betonpumpverfahrens mit erhöhter Leistungsfähigkeit und Effizienz zum Erzielen größerer Pumphöhen bei niedrigerem Pumpendruck und somit geringerem Energieverbrauch. Dafür ist eine neue, innovative Verfahrenstechnik zur modellunterstützten und sensorbasierten Steuerung des Pumpprozesses sowie ein System zur Beeinflussung des Betonfließverhaltens im Rohr während des Pumpprozesses auf der Grundlage elektromagnetischer Pulsation zu entwickeln. Weiter werden innovative Methoden und Materialien für die Skalenübertragung vom Labor in den Originalmaßstab entwickelt, welche die Parameteridentifikation und die Anwendung des Verfahrens unter verschiedenen Randbedingungen erleichtern. Zudem sollen mögliche Veränderungen der Betoneigenschaften durch die elektromagnetische Pulsation oder die sehr hohen Scherkräfte beim Pumpen untersucht werden, um eine Zertifizierung des Pumpverfahrens im Anschluss an das Projekt vorzubereiten.

Kooperationspartner: ifT – Institut für Fluidtechnologien GmbH (Bremerhaven) und NADA Engineering&Construction Co., Ltd. (Südkorea) und Myongji University (Südkorea)

Projektträger: AiF Projekt GmbH, Zentrales Innovationsprogramm Mittelstand (ZIM) des BMWi

Laufzeit: 3 Jahre (2016-2018)

Ansprechpartner: Dr.-Ing. Inka Dreßler, Niklas Nolte M. Sc., Dr.-Ing. Hans-Werner Krauss

The project aims to create innovations in material and process technology with which the repair of concrete and reinforced concrete components under heavy chemical attack (biogas plants and wastewater structures) can be carried out significantly more economically and efficiently than with methods commonly used today. The intention is to develop a composite material (mortar system) consisting of an alkali-activated and fibre-reinforced mortar and a steel-free reinforcement (e.g. glass fibre fabric). The material should be resistant to aggressive media and have crack-bridging properties in order to permanently guarantee a high level of impermeability and acid resistance even with variable crack widths in the component. Due to the extreme environmental conditions and the special material properties, the success of a repair depends to a large extent on the techniques and procedures for applying the material to be developed within the framework of the project. The innovations in material and process technology to be developed will enable a significantly more economical repair as well as a longer service life of the repaired plants.

The objective is to develop a cement-free mortar system based on alkaline-activated binders with crack-bridging properties as well as suitable application techniques for different areas of application and boundary conditions. This should enable the repair of reinforced concrete surfaces with separating cracks (with/without variable crack widths) under strong chemical attack with considerable advantages over today's usual repair measures in terms of service life, economic efficiency and work hygiene.

Project partners: BIT Bauwerkserhaltung GmbH, Hamburg und Remmers Baustofftechnik GmbH, Löningen

Project funding organisation: AiF Projekt GmbH, Central Innovation Programme for SMEs (ZIM) - BMWi

Duration: 2 Jahre

Contact person: Dipl.-Ing. (FH) Stefan Ullmann

The DFG's Priority Programme 1542 deals with the theoretical and constructive basis of Lightweight building with concrete.The core idea in this context is "form follows force".

The working group "Development of novel connections for geometrically complex surface and bar elements made of UHPC" is researching hybrid load-bearing structures made of fibre-reinforced ultra-high performance concrete (UHPFRC). The aim is to produce organic node elements from casting moulds in order to be able to realise modular truss-like load-bearing structures. In addition to the optimisation of the complex node geometry, the production of the components is an essential task.

Furthermore, shell structures are being investigated as part of the priority programme "Development of novel connections for geometrically complex surface and beam elements made of UHPC". The overall system of the shell is to be broken down into individual, self-supporting surface bearing elements. In this context, the formation of the coupling points is to be researched by means of numerical simulations and experimental investigations.

In the 2nd funding period, the sub-project: "From component joining to lightweight load-bearing structures: Hybrid, dry-joined beam, surface and space support elements made of UHPFRC", the modular construction method with large UHPFRC components is being investigated.

Further information on the priority programme: www.spp1542.tu-dresden.de

Project partner: TU Braunschweig, Institute of Structural Design

Funding period / Duration: 3 years

Funded by: Deutsche Forschungsgemeinschaft (DFG)

Contact person: Dipl.-Ing. Sven Lehmberg