Carbon-reinforced concrete (CRC) - research

Table of contents

1. 1. 1. C - 32 Shear force transfer across crack flanks in carbon-reinforced concrete
      2. C - 31 Numerical simulation of carbon reinforced concrete slabs
      3. C - 30 Four-point bending test on a carbon concrete T-beam
      4. C - 29 Flexural behavior of self-prestressed concrete slabs with carbon rod reinforcement
      5. C - 28 Alternating reinforcement guidance in expansion body tests
      6. C - 5 Installation parts for components made of carbon concrete
      7. C - 2 Prestressed reinforcements made of carbon, glass and basalt

C - 32 Shear force transfer across crack flanks in carbon-reinforced concrete

Carbon-reinforced concrete enables the construction of jointless concrete pavements. Due to its corrosion resistance, the carbon reinforcement can be incorporated into the concrete pavement with a thinner concrete cover. This allows for greater flexural stiffness while using materials more efficiently. However, further studies on short- and long-term loading are still necessary for the use of carbon-reinforced concrete as a continuous concrete pavement. For example, if tensile stresses and cracks occur in this concrete pavement due to thermal deformation, shear forces from traffic loads must be transferred via the crack flanks.

In this thesis, cracked and uncracked carbon-reinforced concrete slabs shall be examined with regard to their shear force transfer across crack flanks. For this purpose, a literature review should first be conducted on shear force transfer, crack interlocking, and dowel action in carbon-reinforced concrete. Subsequently, shear force transfer shall be investigated for various crack widths. The objective is to identify the crack width up to which shear force transfer is possible for the continuous concrete pavement.

The task will be specified in consultation with the student.

Contact person:
Dipl.-Ing. Jonathan Schmidt
+49-351-463-41118

C - 31 Numerical simulation of carbon reinforced concrete slabs

Over the past decades, carbon fabrics have been continuously developed for the reinforcement of reinforced concrete components. Due to the increased tensile strength of modern carbon fabrics, different failure mechanisms occur compared to older generations. Component tests are carried out in the laboratory to investigate these mechanisms.

In order to reduce the experimental effort in the future and enable a deeper understanding of the component behavior, the use of numerical models, in particular the finite element method, is recommended.

A critical area in the modeling is the bond joint between the reinforced concrete and the reinforcement layer. This is described on the basis of the Mohr-Coulomb crack criterion. Modeling recommendations for the realistic recalculation of components have already been developed as part of a dissertation.

The aim of the project / diploma thesis is to apply these modeling recommendations to reinforced concrete slabs with varying boundary conditions (e.g. geometry and material parameters). The numerical results are to be compared with experimental test data. The FE software ATENA is used for the simulations.

Contact person:
Dipl.-Ing. Carolin Würgau
+49 351 463-39369

C - 30 Four-point bending test on a carbon concrete T-beam

*Project work/diploma thesis - Test design and investigation of the load-bearing capacity of filigree carbon concrete beams

Based on a current project work, in which the reinforcement design for a filigree carbon concrete beam was examined, the manufactured reinforcement is to be examined for its load-bearing capacity in a 4-point bending test. The special feature lies in the thin cross-section components. Since carbon reinforcement, unlike steel, cannot corrode, only a very small concrete cover is required. In a conventional reinforced concrete beam, the stirrups for absorbing the shear force enclose the longitudinal reinforcement for absorbing the tensile forces. With webs of only 3 cm, stirrup reinforcement is not feasible, so the reinforcement of the carbon yarns is alternating. The principle of alternating reinforcement has already been developed at the Institute in previous projects (for an example, see: Mesh lattice girders).

*Dependingon whether a project or diploma thesis is being prepared, the scope may only include the design of experiments or, for the latter, the focus of the load-bearing capacity analysis may be limited.

The task will be specified in consultation with the student.

Contact person:
Dipl.-Ing. Lore Zierul
0351 463 33609

C - 29 Flexural behavior of self-prestressed concrete slabs with carbon rod reinforcement

Processing only possible as part of a Master's thesis

Carbon reinforcing bars are increasingly being used as an alternative to conventional steel reinforcement, often in combination with high-strength concrete. However, this has an increased tendency to shrink, which can lead to cracking and other serviceability problems. Due to their low compressive strength, carbon reinforcement bars are only able to absorb negative shrinkage strains to a limited extent. As a result, the reinforcement can go into a passive state, which impairs its effectiveness and the structural behavior of the component.

The aim of this work is therefore to investigate the influence of swelling concrete on the load-bearing behavior of concrete slabs reinforced with carbon reinforcement bars. The swelling concrete should partially or completely compensate for shrinkage deformations through a controlled increase in volume. If there is sufficient bonding between the concrete and the carbon reinforcement bars, this expansion can also induce tensile strains in the bars, causing tensile stresses and activating the carbon reinforcement. Overall, the use of swelling concrete is expected to improve the cracking behavior and significantly reduce the deflections of the slabs.

To implement this research project, several concrete slabs made of swelling concrete with dimensions of around 1500 mm × 500 mm × 80 mm will be produced. Prior to this, tests are carried out on small-scale test specimens to investigate the bond development between concrete and carbon reinforcement bars. Distributed fiber optic sensing (DFOS) technology is used to record the expansions and strains in the concrete and the reinforcing bars.

Contact person:
Mohammed Dhahir M.Sc.
+49 351 463-40411

Jasmin Dräger M.Eng.
+49 351 463-39878

C - 28 Alternating reinforcement guidance in expansion body tests

Project work: Conceptual design of tests

Components can be manufactured thinner if carbon reinforcement is used, as only a very small concrete cover is required. This is accompanied by construction using assembled slab elements instead of full cross-sections. However, the shear force reinforcement cannot then be realized using stirrups, which leads to the concept of alternating reinforcement (for an example, see: Mesh lattice girders). Existing guidelines provide specifications for carrying out tests with a straight grid.

In the thesis, in cooperation with the Institute of Textile Machinery and High Performance Material Technology, test setups for the determination of composite properties are to be researched and a setup implemented.

The task will be specified in consultation with the student.

Contact person:
Dipl.-Ing. Lore Zierul
+49 351 463-33609

C - 5 Installation parts for components made of carbon concrete

* only in German language *

When using carbon reinforcement in precast construction, component thicknesses can be reduced to just a few centimetres. The classic connection technique relies on solid components that serve as an undisturbed anchor base. The low component thickness in carbon concrete construction and the associated increased probability of cracking place new demands on the fastening systems. Systems such as the Halfen Fassadenplatter Anchor FTA-3 adapt to the new challenges.

The aim of the work is to collect and evaluate methods that can make point load application in carbon concrete more favorable for the anchor base through spatial distribution in order to counter both the low component thickness and the expected crack formation. These methods are to be further developed into product concepts. The principle potentials of load transfer are to be estimated. FE programs can be used to analyze the load transfer. However, it is also possible to work without computer support, for example by using framework models. Details of the task are determined together with the student.

* Knowledge of fastening technology is assumed *

Contact person:
Dr.-Ing. Harald Michler
0351 463 32550

C - 2 Prestressed reinforcements made of carbon, glass and basalt

Detailed title: Possibilities and boundary conditions for the production and use of prestressed textile reinforcements

* only in German language *

Up to now, non-metallic reinforcements have mainly been used as slack reinforcement. In the meantime, however, prestressing options such as prefabricated prestressed plates (CPC plates) are already on the market. The work is intended to collect and analyze current applications for prestressed non-metallic reinforcements - mostly in the context of research projects. A comparative analysis of the material properties of metallic and non-metallic prestressing reinforcements is intended to assess the potential of the individual materials, for example the effects of relaxation. The different methods of prestressing, such as prestressing with immediate, subsequent or without bond, are to be considered individually.

The work includes a literature study and preferably comparative hand calculations. Details of the task will be determined together with the student.

Contact person:
Dr.-Ing. Harald Michler
0351 463 32550