Romualdas Mačiulaitis

The effect of concrete composition and aggregates properties on performance of concrete

Abstract The properties of the hardened concrete depend on the selected raw materials: size and amount of the particles of coarse aggregate, as well as on the ratio of other components. Particular countries use various methodologies for the selection of concrete composition to select the components of the concrete mixture. However, the properties of the concrete, selected by using any methodology for the selection of the concrete composition and hardened by following the defined conditions, must satisfy the values of certain necessary characteristics. The results of the implemented research indicate that the most optimal solution is to use the coarse aggregate of multi‐fractional or discontinuous fractional composition. The optimal composition of the concrete must be selected to ensure that the binding material is not overdosed. Yet, all components must be selected in such a way, that the required properties of the final product are retained after concrete mixture hardens. When catalyst waste materials fr...

Further opportunities for development of the method for fire origin prognosis

Abstract After fire in buildings investigators start research. The purpose of it is to find the reason of fire, but this thing can be reliably determined only if the fire origin is fixed. The instrumental fire prognosis for wooden structures is currently the most widely applied method in Lithuania. But the analysis of charring of natural wood specimens and the completed tests have revealed some drawbacks of this method, because the method fails to fully estimate the properties of wood and its protection by fireproofing compounds, the impact of the fire load, etc. The obtained test results will help further resolve the problems of reliability of the above‐mentioned method.

The regulation of physical and mechanical parameters of ceramic bricks depending on the drying regime

Abstract In the scientific studies the influence of burning regime or composition of formation mix on the final properties of the ceramic bricks is analysed most often. However, drying regime is also of paramount importance in the process of the high quality ceramic production. The formed ceramic samples were dried according to 8 different drying regimes while burning regime was not varied during the investigation. The dried samples were burnt for 24 hours keeping the maximum temperature 1050 °C for 3 hours. Later on these parameters were determined experimentally: density, general shrinkage, compressive strength and rate of ultrasound spread. As the statistical and regression analyses of data were performed, the empirical equations, showing how the selected stages of drying regime influence the physical and mechanical parameters of ceramics, and vice versa, how the selection of the dimensions of the stages of drying regime depends on the desired values of the ceramics properties, were derived.

The regulation of structural parameters of ceramics depending on the drying regime

Abstract Always in the shaped semimanufactures of ceramics is some humidity, which we must eliminate before burning. Drying process is to safeguard the satisfactory strength of semimanufactures. Additionally, changes of ceramic samples capacity is to end the drying process, associated with elimination of humidity that would not compose defects ‐ gaps, fractures, fragmentation etc. In this work it was shown, how the selected stages of drying regime influence the structural parameters of ceramics (reserve of porous volume, heterogeneity degree of structure, maximum rate of capillary rise according to watering front, capillary rate of mass flow, water absorption) and vice verse, how the selection of the dimensions of the stages for drying regime depends on the desired values of the of ceramics.

The compressive strength properties of mineral wool slabs: Influence of structure anisotropy and methodical factors

Abstract This paper presents the research on the structure and compressive stress or compressive strength of mineral wool products. The products of chaotic, directional and combinative fibres structure have been studied visually and microscopically. During mechanical tests it was determined that compressive stress (compressive strength) of the stone wool products is dependent on the direction of the load working to the product major face, test specimen dimensions, force increasing rate, fibres distribution (orientation) and methodical peculiarities.

Eco‐balance features and significance of hemihydrate phosphogypsum reprocessing into gypsum binding materials

Abstract The classification and grouping of materials investigation according to raw materials nature and product purpose (use) was conducted by using comparative material energetic usefulness and its production ecobalance analytical methods. Energy expenditures and pollution emissions into the environment were studied and compared to analogical purpose materials. One of the most economically perspective technogenic waste ‐ extractive hemihydrate phosphogypsum was investigated. Two technological production streams of phosphogypsum were studied. It was found, that the energy needs for production of analogical purpose materials (wall partitions) differ significantly. The nature of raw materials has an influence on energetic usefulness. The most effective materials according to their nature, energetic usefulness and environmental protection are mineral ones, especially if they are made with technogenic inorganic waste materials. The best results, from the energetic and ecological point of view, are obtained...

New possibilities of quality regulation for ceramic products

Abstract Investigation of ceramic products is presented in the article. Material mix of these products consists of such components as clay of Rokai deposit, sand of Daugeliai deposit, crushed brick of Rokai brickworks, anthracite of Archangelsk region, peat of Rekyvas deposit and ground bottle glass. Statistical regression analysis is performed for the measured structural parameters of a ceramic body and various components of material mix. Empirical equations are derived allowing to select the composition of material mix according to the desirable structural parameters of a ceramic article (reserve of pore volume, degree of structural in homogeneity, maximum rate of capillary wetting front, capillary rate of mass flow and total open porosity). After selecting the composition of material mix, the prognosis of ceramic body characteristics is performed. Results of the investigation will have a wide practical application.

Possibilities to recycle auto glass waste in building ceramics

AbstractSubstantial amounts of glass waste end up in landfills because unlike ordinary glass, auto glass is unsuitable for recycling in the glass industry due to organic additives. However, it was determined that the additives make auto glass waste appropriate for the production of building ceramics, which results in improved physical-mechanical and structural properties. The optimum quantity of the additive contained in auto glass waste amounts to 15% of the formation mixture, and the most appropriate burning temperature is 1080 °C. The density of such ceramic chip is 2059 kg/m3, the water absorption determined after 72 h is 1.2%, and the forecasted frost resistance at the beginning of decomposition is 1343 cycles, but amounts to 2188 cycles at the end of decomposition.

Research of natural wood combustion and charring processes

Abstract Wood is a material widely used for construction purposes and – in some cases – it is the main element of building structures. In comparison with other materials, wood has a number of advantages, such as lightness, strength, resistance to impacts and vibration, simplicity in terms of processing and etc. However, one of the largest drawbacks of wood is flammability. Charring of wooden structures is the most apparent feature of combustion in case of fire in wooden buildings or buildings made of wooden structures. This property is important in identifying causes of fire; therefore it is necessary to relate charring of wooden structures with certain significant effects of fire, such as its duration or temperature. The article addresses the wood characteristics that impact on combustion and charring. It describes test methods and properties of wood samples under research. Research of charring rate of natural softwood and hardwood as a function of heating time, and regressive analysis of data were carri...

Evaluation of service frost resistance of ceramic facing tiles

Abstract The problem of frost resistance is relevant to facing materials, especially glazed ceramic tiles. Analysing the processes of ceramic tile destruction it is important to take into account the primary destruction symptoms. New estimation of service frost resistance of ceramie tile according to residual surface and residual mass of the tile after a certain number of simulated service cycles is presented in the paper. Applying the new estimation, the forecast of frost resistance under extremely unfavourable service conditions may be performed. As for other ceramie products regarding frost resistance, one of the most important parameters is the reserve of pore volume. For a rapid estimation of service frost resistance of ceramie tile it is best to use several parameters under multiple correlation with the parameter of service frost resistance.