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Titanium dioxide (TiO2) is used as a UV light absorber to protect wood matter from photodegradation. In this paper, interactions between wood and TiO2 coating are studied, and the efficiency of the coating is evaluated. For the experiments, two wood species were chosen: beech (Fagus sylvatica) and pine (Pinus sylvestris). Molecular and physical modifications in coated and uncoated wood exposed to UV radiation were investigated with Fourier transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR) and transmission electron microscopy (TEM). UV-VIS spectroscopy was used to describe the absorption of UV light by the TiO2 planar particles chosen for the experiment. It was demonstrated that TiO2 coating protects wood against photodegradation to a limited extent. TEM micrographs showed fissures in the wood matter around clusters of TiO2 particles in beech wood.

Structural timber is a traditional construction material. Timber structures belong to essential parts of almost all historical buildings, especially roof and ceiling structures. Their actual condition affects durability of the whole building, therefore it is necessary to check the conditions of the structure regularly and take care of possible undesirable changes. If these structures have historical value we have to use non-destructive or semi-destructive methods during this investigation. Penetration methods in combination with ultrasonic method are used nowadays [. Penetration devices are suitable to determine the density, surface and internal biological degradation, growth defects and moisture content of the element. The density and the velocity of ultrasonic wave represent input information to derive dynamical modulus of elasticity. Penetration devices work on the principle of measuring the depth of penetration of a steel tip or on the principle of resistance drilling. Another method of determining the density of inbuilt element is the radial core. These methods are semi-destructive. It is the subject matter of the authors research to replace these penetration methods by radiometric measure of mass density. This method is based on the principle of gamma rays dispersion or on the principle of gamma rays absorption in a timber element. Radiometry as a measurement of density is often used for concrete constructions and asphalt pavement now. This measurement can be applied to the inbuilt elements, which is its a main advantage.

This article presents woven carbon-fiber-reinforced polymer (CFRP) tubular mesh used as a reinforcement on the inner surface of hollow beams made of high-performance concrete (HPC). The tubular mesh was designed to serve as both the tensile and shear reinforcement of hollow beams intended for the construction of small self-supporting structures that could be assembled without mechanization. The reinforcement was prepared with a tri-axial weaving machine from carbon filament yarn and was homogenized using epoxy resin. The interaction of the composite reinforcement with the cementitious matrix was investigated, and the surface of the reinforcement was modified using silica sand and polyvinyl alcohol (PVA) fibers to improve cohesion. The sand coating enhanced bond strength, resulting in the significantly higher flexural strength of the hollow beam of 128%. The PVA fibers had a lower positive effect of 64% on the flexural strength but improved the ductility of the beam. Individual beams were connected by gluing steel parts directly inside the hollow core of the HPC beam. This procedure provides good interaction between the CFRP reinforcement and the glued steel insert and allows for the fast and simple assembly of structures. The weaving of additional layers of the CFRP reinforcement around HPC beams was also explored. A small structure made of the hollow HPC beams with inner composite reinforcement was constructed to demonstrate the possibilities of the presented technology.