Adorján Borosnyói

Understanding the rebound surface hardness of concrete

AbstractSurface hardness testing of materials can be considered as the oldest method to get information about strength related material properties. In recent decades the rebound hammer has been the most popular surface hardness testing device for concrete uniting the advantages of its predecessors. In the technical literature numerous proposals are available for simple, two-parameter regression analyses of rebound surface hardness vs. compressive strength relationship of concrete. The remarkable diversity of the proposed curves implies the need of the more than two-parameter regression techniques to reveal the most pronounced parameters governing hardness behaviour. The objectives of present experimental studies were to carry out dynamic and static hardness tests, Youngs modulus and compressive strength tests on concrete specimens. From the development of the tested properties with time it can be concluded that the rebound hammers provide a hardness value for high strength concretes connected to the Youn...

Performance Characteristics of Waste Glass Powder Substituting Portland Cement in Mortar Mixtures

In the present work, soda-lime glass cullet (flint, amber, green) and special glass cullet (soda-alkaline earth-silicate glass coming from low pressure mercury-discharge lamp cullet and incandescent light bulb borosilicate glass waste cullet) were ground into fine powders in a laboratory planetary ball mill for 30 minutes. CEM I 42.5N Portland cement was applied in mortar mixtures, substituted with waste glass powder at levels of 20% and 30%. Characterisation and testing of waste glass powders included fineness by laser diffraction particle size analysis, specific surface area by nitrogen adsorption technique, particle density by pycnometry and chemical analysis by X-ray fluorescence spectrophotometry. Compressive strength, early age shrinkage cracking and drying shrinkage tests, heat of hydration of mortars, temperature of hydration, X-ray diffraction analysis and volume stability tests were performed to observe the influence of waste glass powder substitution for Portland cement on physical and engineering properties of mortar mixtures.

NDT assessment of existing concrete structures: spatial analysis of rebound hammer results recorded in-situ

AbstractA comparative spatial analysis of surface hardness of structural concrete is introduced. Main objective of the paper is to make a repeatability comparison of three types of the still most popular non-destructive testing devices for concrete: L-type original Schmidt rebound hammer, N-type original Schmidt rebound hammer and N-type Silver Schmidt rebound hammer. Results indicate that the surface hardness measurement uncertainty is related to the weight of the hammer mass and is apparently not related to the impact energy of the rebound hammer devices. It is observed that the measure of surface hardness for the Silver Schmidt rebound hammer (Q-value) does not have positive correlation to the original rebound index (R). Results indicate the best performance of the N-type original Schmidt rebound hammer in terms of stability and normality of data. Geostatistical analysis of the measured data (in terms of empirical semivariograms) highlights different statistical behaviour for the mechanical recording r...

Performance of novel type three dimensionally deformed steel fibres for concrete

Preliminary results of a two years long research and development project is introduced in this paper. one novel type of 2D deformed steel fibre (with the product name of PetiX) and four different types of 3D deformed steel fibres (PetiX v45; PetiX v90; PetiX s45; PetiX s60) were designed, manufactured and tested under laboratory conditions. the laboratory tests showed promising results. superior performance of certain types of 3D deformed steel fibres was observed. considerable improvement of the bond performance of steel fibres was realized in concrete and increased flexural toughness of sFrc prismatic specimens tested in flexure was demonstrated. keywords: concrete, steel fibre, 3D geometry, bond, flexural strength, toughness Péter Kerekes civil engineer (Bsc) student at Budapest university of technology and economics (Bme), Faculty of civil engineering. main fields of interest: development and performance of steel fibres for concrete. Adorján Borosnyói civil engineer (msc), PhD, Associate Professor at Bme Dept. of construction materials and engineering Geology. main fields of interest: cracking and deflection of reinforced concrete, application of non-metallic (FrP) reinforcements for concrete structures, bond in concrete, nondestructive testing of concrete, supplementary cementing materials for high performance concretes, concrete technology. member of the fib task Group 4.1 „serviceability models”, corresponding member of riLem technical committee 249-isc „non destructive in situ strength assessment of concrete” and chairman of the szte concrete Division.