Przedstawiono zalecenia dotyczące projektowania betonów zwykłych metodą trzech równań z kruszywa dwuskładnikowego. Autorzy zaproponowali oryginalny sposób obliczania gęstości i wodożądności mieszanki kruszywa. Szczególną uwagę zwrócono na sposób ustalenia składu mieszanki kruszywa. Wyniki badań eksperymentalnych wykazały, że dobór optymalnego punktu piaskowego kruszywa w metodzie trzech równań powinien uwzględniać klasę betonu (C/W), konsystencję mieszanki betonowej oraz zawartość zaprawy i zaczynu.
EN
Some advices for projecting the concrete with two-component aggregate using three equations method are presented. Authors of this paper proposed original method for the apparent gravity and water needs calculation of aggregate mix. Main attention was paid to the choice of proper aggregate mix composition. The results of experimental investigations showed that the optimal sand point of the aggregate mix depends on the class of concrete and the workability of the concrete mix.
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In this paper the results of mortars with glass microfibers investigations are presented. The main objective of this work was to evaluate the influence of glass microfibers on shrinkage cracking, physical and mechanical properties of mortars with constant amount of superplasticizer. Obtained results showed that glass micrfibers have significant influence on shrinkage cracking of mortars. For investigated mortars with microfibers cracks did not appear or occurred later and the cracks widths were several times smaller than in mortars without fibers. The addition of microfibers decreased workability, and gravity and increased the air content in fresh mortars. It was found that mechanical properties of mortars increased when the volume fraction of fibers exceeded 0,3%. Obtained results showed that glass fibers significantly improved the cracking resistance and can be use as shrinkage reinforcement.
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This paper presents methods to determine the material constants of cement-based composites. The shear modulus G, Young's modulus E and Poisson's ratio v have been calculated. Test on cement-based composites plates in biaxial bending and pure shear state is useful tool to determine constances of materials. Obtained results are similar to others researchers results. Used method with computer support is very useful in researches where a few parameters have to be measured exactly at the same time.
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