Effect of concrete surface treatment on adhesion in repair systems

Existing concrete surfaces need to be roughened to a profile necessary to achieve mechanical interlocking with any repair material. In this study, different surface treatments (e.g. grinding, sandblasting, shotblasting, hand- and mechanical milling) were performed and the quality of the preparation established on the basis of three main parameters: surface geometry, superficial concrete microcracking and adhesion. Surface geometry was characterised on the basis of the measurement of surface profile-profilometry-and the analysis of statistical and amplitude parameters calculated from the waviness (lower frequencies) and the roughness (higher frequencies) profiles of the surface. Investigations were also performed to assess the quality of the superficial zone of concrete and cracks were systematically observed in relation to surface treatment where both scanning electron microscopy and light microscopy were used for analysis. Finally, a repair mortar with or without bond coat, was applied to the concrete substrates in order to measure adhesion. Relationships clearly show the effect of roughness on adhesion in the case where no bond coat was used and also the influence of the power of the surface treatment on the waviness shape of the profile and the presence of microcracks in the near-surface layer related to failure type

Effect of concrete surface treatment on adhesion in repair systems

peer reviewedExisting concrete surfaces need to be roughened to a profile necessary to achieve mechanical interlocking with any repair material. In this study, different surface treatments (e.g. grinding, sandblasting, shotblasting, hand- and mechanical milling) were performed and the quality of the preparation established on the basis of three main parameters: surface geometry, superficial concrete microcracking and adhesion. Surface geometry was characterised on the basis of the measurement of surface profile-profilometry-and the analysis of statistical and amplitude parameters calculated from the waviness (lower frequencies) and the roughness (higher frequencies) profiles of the surface. Investigations were also performed to assess the quality of the superficial zone of concrete and cracks were systematically observed in relation to surface treatment where both scanning electron microscopy and light microscopy were used for analysis. Finally, a repair mortar with or without bond coat, was applied to the concrete substrates in order to measure adhesion. Relationships clearly show the effect of roughness on adhesion in the case where no bond coat was used and also the influence of the power of the surface treatment on the waviness shape of the profile and the presence of microcracks in the near-surface layer related to failure type

Metallographic and corrosion research of copper from archaeological sites

In this study, copper slabs - ingots, from both Gdańsk and Krakow were examined. Besides metallographic examinations, attention was focused on analyses of corrosion products. The following techniques were applied: scanning electron microscopy with fluorescent X-ray microanalysis and X-ray diffraction. The conducted investigations enabled determination of the causes of corrosion in the old copper slabs, due mainly to the mediaeval alloying techniques and copper processing technologies

Scattering of Dirac particles from non-local separable potentials: the eigenchannel approach

An application of the new formulation of the eigenchannel method [R. Szmytkowski, Ann. Phys. (N.Y.) {\bf 311}, 503 (2004)] to quantum scattering of Dirac particles from non-local separable potentials is presented. Eigenchannel vectors, related directly to eigenchannels, are defined as eigenvectors of a certain weighted eigenvalue problem. Moreover, negative cotangents of eigenphase-shifts are introduced as eigenvalues of that spectral problem. Eigenchannel spinor as well as bispinor harmonics are expressed throughout the eigenchannel vectors. Finally, the expressions for the bispinor as well as matrix scattering amplitudes and total cross section are derived in terms of eigenchannels and eigenphase-shifts. An illustrative example is also provided.Comment: Revtex, 9 pages, 4 figures, published versio

Refining processes in the copper casting technology

The paper presents the analysis of technology of copper and alloyed copper destined for power engineering casts. The casts quality was assessed based on microstructure, chemical content analysis and strength properties tests. Characteristic deoxidising (Logas, Cup) and modifying (ODM2, Kupmod2) formulas were used for the copper where high electrical conductivity was required. Chosen examples of alloyed copper with varied Cr and Zr content were studied, and the optimal heat treatment parameters were tested for a chosen chromium copper content, based on the criterion of hardness and electrical conductivity tests. Searching for materials with high wear resistance, the influence of variable silicone content on the properties of CuNiSi alloy was researched

The technology transfer of non-ferrous alloys casting during the middle age

The article reports on the findings from the metallographic analysis of 13th c. archaeological objects from Chełm (eastern Poland). The group submitted for analysis includes jeweller’s dies used in the production of women’s ceremonial ornaments, crucibles and bronze ornaments. The Mongol invasion of 13th c. had caused craftsmen from central areas of East Europe to flee and seek shelter in the western parts of Rus. It may be safe to interpret the finds from Chełm as the remains of a jeweller’s workshop, the site of casting and working copper alloys and silver. The analysis of the technology used in casting copper alloys and silver in the jeweller’s workshop were made using optical microscopy, X-ray spectroscopy and X-ray radiography

Family involvement for children with disruptive behaviors: The role of parenting stress and motivational beliefs

Children with disruptive behaviors are at risk for adverse outcomes. Family involvement is a significant predictor of positive child behavior outcomes; however, little research has investigated parent psychological variables that influence family involvement for children with disruptive behaviors. This study investigated the role of parental motivational beliefs (i.e., role construction and efficacy) as a potential mechanism by which parenting stress impacts family involvement for families of children with disruptive behaviors. Results indicated that parent role construction mediated the relation between parenting stress and all aspects of family involvement examined (i.e., home-based involvement, school-based involvement, and home–school communication). Parent efficacy mediated the relation between parenting stress and home-based involvement only. Parents of children with disruptive behaviors reporting stress may experience negative beliefs about their role and efficacy to support their child’s education, which may thereby negatively influence their actual involvement. Therefore, parent motivational beliefs may serve as an important point for intervention to support involvement of families of children with disruptive behavior