Fundamental Analysis of the Machining Process of a Composite Material Made of Concrete and CFRP with Diamond Grinding Tools

Although concrete is able to bear high compressive loads, its possibility to withstand tensile loads is very low. Hence, in construction elements steel bars are embedded as reinforcement. To avoid corrosion, a thick concrete covering of the steel bars is necessary. The new composite material made of carbon fibre reinforced plastic (CFRP) and high-performance concrete offers an alternative possibility and provides the opportunity for thinner and lighter construction elements. Advantages of the new construction material compared to reinforced concrete are, among others, corrosion resistance, conserving resources and new possibilities in the design of constructions.

According to recent developments in the construction industry and existing research programs it can be assumed that the amount of CFRP reinforced concrete elements will increase in the next few years. Assuming that each construction will be rebuild or demolished during its life cycle, there is a need for efficient machining of this construction material. As the impact of the CFRP elements on the machining process have not yet been researched, this project will analyse the basic interrelationships in machining based on model experiments. Metal bonded diamond tools are used for machining the new composite material as is customary for the machining of concrete. The combination of the different materials with their inhomogeneous material properties places particular demands on the development of diamond tools for the machining of the composite material carbon concrete.

The research project comprises an analysis of the material separation of the new construction material by diamond tools as well as the mechanisms acting through the phase change between CFRP and concrete. Scratch tests are a fundamental testing method to understand the general mechanism of material removal. Therefore single grain scratch tests will be carried out to analyse the elementary interdependencies of the machining process. The knowledge of single grain scratch tests and multi grain single segment tests can be used for the optimisation of the machining process of the multiphase material CRFP reinforced concrete. Based on the quantitative and qualitative results of single grain scratch tests and multigrain single segment tests, process models of core drilling processes will be generated. Hence, these investigations constitute the fundamental basis for the development of efficient diamond tools for the machining of CFRP reinforced concrete.

Fig.:Levels of analysis of the research project “Machining process of CFRP reinforced concrete”