The rheological properties of self-compacting concrete are closely influenced by temperature and the time. Previous studies which aim was to research the effect of temperature on self-compacting concrete workability, showed that the behaviour of fresh SCC at varying temperatures differs from that of normal vibrated concrete. The paper presents the study of rheological properties of fresh self-compacting concrete mixtures made with portland, blast furnace and component cement. Two types of superplasticizers were used. It was proven that temperature has a clear effect on workability; it can be reduced by selecting the appropriate superplasticizer and cement.
The cast alloys crystallizing in Fe-C-V system are classified as white cast iron, because all the carbon is bound in vanadium carbides. High
vanadium cast iron has a very high abrasion resistance due to hard VC vanadium carbides. However, as opposed to ordinary white cast
iron, this material can be treated using conventional machining tools. This article contains the results of the group of Fe-C-V alloys of
various microstructure which are been tested metallographic, mechanical using an INSTRON machine and machinability with the method
of drilling. The study shows that controlling the proper chemical composition can influence on the type and shape of the crystallized
matrix and vanadium carbides. This makes it possible to obtain a high-vanadium cast iron with very high wear resistance while
maintaining a good workability.
The Tertiary lignite formations in the Bełchatów deposit, along with coal, are built of plastic, weakly compact and loose rocks. Their physical and mechanical parameters, don’t pose operational problems. However, varieties of a different lithological character and physical-mechanical properties rocks, causing difficulties when mining the overburden rocks, appear within them. These include: Mesozoic limestones, Tertiary sandstones and conglomerates, as well as Quaternary iron feldspar rocks. The article features a lithological characterization as well as values of basic physico-mechanical parameters. They form the basis of the geological engineering classification and decide about their difficult workability. The possibilities of their raw material utilization were also discussed.
The presented results describe the effect of severe plastic deformation on the structure and mechanical properties of AA5083 and AA5754 alloys. Both materials were subjected to single hydrostatic extrusion (HE) and cumulative hydrostatic extrusion in the case of AA5083 and a combination of plastic deformation by equal-channel angular pressing (ECAP) with the next HE for AA5754. After the deformation, both alloys featured a homogeneous and finely divided microstructure with average grain size deq = 140 nm and 125 nm for AA5083 and AA5754, respectively. The selection of plastic forming parameters enabled a significant increase in the UTS tensile strength and YS yield stress in both alloys – UTS = 510 MPa and YS = 500 MPa for alloy AA5083 after cumulative HE, and 450 MPa and 440 MPa for alloy AA5754 after the combination of ECAP and HE, respectively. It has been shown on the example of AA5083 alloy that after the deformation the threads of the fasteners made of this material are more accurate and workable at lower cutting speeds, which saves the cutting tools. The resultant properties of AA5083 and AA5754 alloys match the minimum requirements for the strongest Al-Zn alloys of the 7xxx series, which, however, due to the considerably lower corrosion resistance, can be replaced in many responsible structures by the AA5xxx series Al-Mg alloys presented in this paper.