Congress contributions

In former own publications it was shown, that high precision concrete parts are a reliable alternative to natural stone for machine base frames. Beside long term stability also a predictable and highly reproducible thermal behaviour is required. The use of low expansion materials is not appropriate for a whole machine structure since these materials are coming with several drawbacks in the mechanical behaviour in combination with high costs. Thermal compensation by special design also raises cost and complexity. The application of materials with identical thermal expansion coefficients in combination with appropriate mechanical properties can solve this problem at significantly reduced costs. Concrete is a promising material for the whole machine structure under these circumstances. In contrast to base frames moving parts need to have a lightweight design thus requiring a high level of specific stiffness. Concrete with a specific stiffness close to steel is an interesting material for the design of movable components coming up with dynamic properties comparable to welded steel structures. Additionally a high material strength is needed in lightweight design. Concrete shows high compressional strength but is sensitive to tensile stress that cannot be fully eliminated. Therefore notch effects and stress concentrations need to be avoided. Reinforcement by implementation of steel or carbon fibres is not applicable since they come with thermal inhomogeneity. An alternative reinforcement can also be done by organofunctional sol-gel silane coating.