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

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 distribution of O and N in the surface region of laser-patterned titanium revealed by atom probe tomography

Direct Laser Interference Lithography (DLIL) has shown to be a promising technique to chemically and physically alter the surface of titanium. In this work, atom probe tomography analysis was performed on DLIL-treated titanium to obtain the chemical composition of the surface in maxima and minima interference positions. The analysis revealed that a multilayer structure consisting of oxide/oxynitride is formed at both positions; however, the chemical composition is altered differently between the two. The observed difference is believed to be due to an uneven heating and temperature distribution, which is demonstrated by thermal simulations

The Efficacy of Conjoint Behavioral Consultation on Parents and Children in the Home Setting: Results of a Randomized Controlled Trial

The present study is a large-scale randomized trial testing the effects of a family-school partnership model (i.e., Conjoint Behavioral Consultation, CBC) for promoting behavioral competence and decreasing problem behaviors of children identified by their teachers as disruptive. CBC is a structured approach to problem solving that involves consultants, parents, and teachers. The effects of CBC on family variables that are commonly associated with important outcomes among school-aged children (i.e., family involvement and parent competence in problem solving), as well as child outcomes at home, were evaluated. Participants were 207 children with disruptive behaviors from 91 classrooms in 21 schools in kindergarten through grade 3 and their parents and teachers. Results indicated that there were significantly different increases in home-school communication and parent competence in problem solving for participants in the CBC relative to control group. Likewise, compared to children in the control group, children in the CBC group showed significantly greater decreases in arguing, defiance, noncompliance, and tantrums. The degree of family risk moderated parents’ competence in problem solving and children’s total problem behaviors, teasing, and tantrums

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

Characterization of nonequilibrium shock interaction in CO2-N2 flows over double-wedges with respect to Mach number and geometry

The characterization of the shock interaction mechanism originating from the high-Mach nonequilibrium flow over double-wedge geometries is key to the design of hypersonic vehicles. The impact of changes in the freestream Mach number and double-wedge geometry on the patterns of shock interaction is investigated by means of numerical simulation in the case of CO2-N2 flows. The extended laminar Navier–Stokes equations with a two-temperature model to account for translational-to-vibrational internal energy transfer are considered the physical model of this type of flow. Simulations show that reducing the freestream Mach number leads to an increase in the separation region, both in the compression corner and in the locations of shock impingement. The impact of the size of the separation region on the patterns of interaction is such that it causes variations in the type of shock interaction. From the point of view of the flow physics near the wedges, decreasing the freestream Mach number has an equivalent effect to increasing the angle of the second wedge and an opposite effect to increasing the freestream temperature on the pattern of interaction. Results show that decreasing the freestream Mach number leads to an overall reduction in pressure and heating loads along the surface of the wedges and smaller regions of thermal equilibrium behind the bow shock