Key Engineering Materials Vol. 808

Abstract: The paper deals with the theoretical analysis of physical, structural, and layout determinants affecting the design and restoration of historic buildings in terms of fire safety. Legislative requirements for fire safety of historic buildings in the Slovak Republic. Definition of the construction and layout limits in architectural solutions in model buildings in terms of optimizing the original function within the valid legislation. Construction possibilities considering the protection of building elements at higher fire load and layout changes in structures built to the original trusses.

Abstract: The paper deals with the resistance of reinforced concrete against fire and the degradation of reinforced concrete due to high temperatures. In the first part the processes of degradation of concrete are solved due to the evaporation of water and its change of state with respect to the different thermal expansion of aggregates and concrete reinforcement members. The main part is focused on the construction of monolithic and prefabricated structures of industrial chimneys. The most common types of protection of the chimney's internal parts from the exhaust gases are discussed here. Also the possibilities of designing individual expansion joints are described. In the experiment, the problem of chimney damage, with the subsequent description of the chimney diagnostics in the premises of Unipetrol in Litvínov, was solved due to an extraordinary event - explosion of the ethylene unit.

Abstract: The paper presents the results of the experimental work which was focused on the use of the Impact-echo method for testing of concrete specimens damaged by high-temperature. The test specimens were heated to 600 and 800 °C for sixty, one hundred twenty and three hundred minutes. After heating, the samples were continuously cooled to room temperature and tested by Impact-echo method.

Abstract: During the fire, structures of a building are exposed to the effect of a high temperature. As a result, the strength parameters and physical properties of concretes and cement mortars undergo change. Their range depends on the time and temperature of the fire. Describing the changes of the internal structure of concretes and mortars resulting from a fire is important in the fire diagnostics of the structures. The paper presents the results of an original research project, within which there was an attempt to relate changes in mechanical properties of the cement mortars with changes in the crystal structure of cement paste. For this purpose, the authors prepared cement prisms, which were heated at various temperatures that occur during a fire after 28 days of their curing. Then, the samples were subjected to compressive strength tests and tests of a structure and a phase composition using an electron scanning microscope. Scanning microscopy is a precious research method that allows observing surfaces of various materials with magnifications from x50 to even x1000000 at a very big sharpness depth. The tests conducted by the authors showed that the effect of fire and of the gradient of high temperatures on the executed samples causes the deterioration of the cement paste in the form of changes in physico-mechanical properties and in its internal structure. As the temperature increases, the compressive strength of the paste decreases gradually and proportionally. The SEM analysis also showed that the change in the physical parameters of the cement paste is reflected in its phase composition.

Abstract: The paper presents data on the use of the alkaline aluminosilicate binder-based adhesive of the system Na₂O•Al₂O₃•(4-6)SiO₂•(17-20)H₂O for gluing and fire protection of structural timber elements. The results of the study of thermoresistant phases in the reaction products of the alkaline aluminosilicates are reported and discussed. The results allowed to show that at SiO₂/Al₂O₃ between 5 and 6 the zeolite-like phases of heulandite types, which, under action of temperatures, are able to form a porous aluminosilicate artificial stone with low thermal conductivity (λ=0.09 Wt/m•К, DSTU B V.2.7-105-2000 (GOST 7076-99)) are formed in the reaction products. The use of the developed aluminosilicate adhesives allow for to classify the structural timber elements as hardly burnable and hardly flammable materials (GOST 12.1.044-1989, EN 13823 + A1: 2014-12, ASTM E119-07). They have the following characteristics: water resistance D3 (EN 204:2001), resistance in splitting up 7.8 MPa (GOST 16483.5-1973), adhesion in normal pull-off test up to 2.6 MPa (GOST 32299-2013 (ISO 4624:2002)).

Abstract: The paper deals with the experimental study of the behaviour of large concrete beams reinforced with glass fibre reinforced polymer (GFRP) rebars exposed to high temperatures equivalent to fire load. The four-point bending test was carried out on the beams after cooling. This study provided values for the load bearing capacity of the beams.