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The effect of chemical degradation of surface layers on mechanical properties of wood
Drdácký, Miloš ; Kloiber, Michal ; Frankl, Jiří ; Bryscejn, Jan ; Tippner, J.
The aim of the research was the determination of the effect of chemical degradation on the surface layers of wooden constructional elements and their mechanical properties and also the depth which the damage reaches. The degradation of wood surface layers was caused by chemical reactions of some compounds contained within fire-prevention coatings applied repeatedly on wooden constructions of historic buildings in the past. These include e.g. ammonium sulphate and ammonium phosphate. This paper presents experimental procedures and results obtained through measuring of mechanical properties in the damaged layer of fibrillated wood and in wood without damage. The observed properties were wood compressive and tensile strength and wood hardness. The results proved a loss in cohesion and changes in mechanical properties only in a thin surface layer.
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Impact of chemical corrosion on mechanical characteristics of wood
Frankl, Jiří ; Kloiber, Michal ; Drdácký, Miloš ; Kučerová, I.
The contribution is dedicated to the problem of chemical corrosion of surface layers of wood in buildings, caused by reaction of chemical substances contained in formerly used chemical anti-fire agents, applied by spraying or coating on wooden construction elements. Findings discovered during survey of buildings and laboratory methods (mechanical tests) of testing of impact of damage on mechanical characteristics of wood and wooden construction elements are presented in the poster.
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Site investigation of wooden structures
Kloiber, Michal ; Holan, J.
The investigation deals with assessment of gothic part of roof frame situated in the Church Nanebevzetí Panny Marie a sv. Ondřeje at Starém Hobzí. A part of investigation there was a proposal of stabilization treatment prepared with respect of historical value of the church. The identification of main abiotic and biotic factors of degradation was performed with the aim of transition determination between the sound and destroyed parts. There was proposed mainly the construction arrangements out of preservative treatment because of their substantial effectiveness. The presumption of such arrangements there are preservative treatments such as sterilization and/or chemical preservation.
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Chemical corrosion wood
Holan, J. ; Kloiber, Michal
Chemical corrosion of wood is caused by acids, bases, and salts. Primary manifestations are changes color, next stage is defiberation of wood surface (into a few centimeters). It causes decrease of mechanical properties. Damaged structures (i.e. roof frame) are not capable enough to bear required loads and there is a threat of crash down. Improper use of preservatives on wood can induced process of corrosion what is apparent on some Czech monuments.
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Impact of the orientation and width of wood rings on the spreading of ultrasound in the wood structure
Kloiber, Michal ; Kotlínová, M.
The subject of the paper is the relationship between ultrasound wave velocity in wood, tree rings orientation and width, and wood mechanical properties (MOE in our case). For measuring, the Arborsonic Decay Detector has been chosen. Sound velocity decreased from radial to tangential direction of measurement. In groups with radial (3) and diagonal (2) position of tree ring, increasing of tree ring width has increased sound velocity. In group with tangential tree ring position no significant influence of tree ring width has been found.
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