EVALUATION OF CALCULATION CORRELATION EFFICIENCY AS MENTIONED IN en 13791 IN ORDER TO DETERMINATION CONCRETE COMPRESSION STRENGTH BY NONDESTRUCTIVE TESTING
The paper presents evaluation of correlations for calculation of concrete compression strength using nondestructive testing parameters for both impact and ultrasonic pulse methods, as listed in EN 13791:2007. This standard indicates procedures relating to compression strength determination in construction and building elements. These procedures relate to compression strength evaluation based either on test specimens (drill cores) or combination of NDT and drill core testing. These nondestructive methods are not covered by procedures taking into account only nondestructive testing parameter pursuant to common calibration correlation. Correlation based on Schmidt impact hammer rebound does not respect various positions of this instrument although positioning of the same is essential for rebound value. No specific type of impact hammer is given for particular calculation correlation. In addition, another challenge is preparation of test surface along with evaluation of impact hammer measurement according to EN 12504-2 as compared with EN 13791. Dispersion of significant values varies between 15 % and 50 % depending upon specific values of impact hammer rebound. Calculation correlation based on ultrasonic pulse velocity implies that – at 4 km/s – concrete compression strength is equal to zero which is absurd conclusion, indeed. We indicate confrontation with calibration correlation as stated by technical bibliography and technical standards as well.
Non-destructive Testing of Solid Brick Compression Strength in Structures
Solid burnt brick sized 290 × 140 × 65 mm or 303 × 145 × 70 mm respectively, represents one of most widespread brick building material, both structural and nonbearing ones, in Czech historical buildings. During their rebuilding and reconstruction, we frequently ask for brickwork material strength. Most exact method is to take test samples just from the construction and put them to trial nevertheless; such method is inapplicable in principle due to damage of the construction under testing. Other potentiality consists in collection of test samples just from brickwork and preparation of small test specimens. However; currently there is no sufficient number of data for elaboration of correct rates for conversion coefficients as to compression/tensile bending strength for small test specimens and whole brick failure strength. Brick strength can be detected also by means of non-destructive testing method such as ultrasonic pulse method. Practically, it appears that non-destructive testing and ultrasonic pulse method are optimal. This paper evaluates efficiency of these methods for brick strength evaluation; It also describes – for selected methods – testing methodology and test result evaluation along with calibration correlations to determine strength based on non-destructive testing parameter. The set of 300 values for each of parameter under monitoring is adequate to specify appropriate calibration correlation. Defined correlation coefficients for given calibration are high enough (more than 0.9) so presented correlations are usable in practice.
Socially responsible enterprise in Cuba: a positive role model for Corporate Social Responsibility?’
This article examines the unique institutional environment of socialist Cuba, where currently a process of controlled marketization and expansion of private enterprise is taking place. The article investigates business behaviour in Cuba with particular reference to implicit assumptions relating to socially responsible enterprise, or Corporate Social Responsibility (CSR) as the term is understood in Western Liberal Democracies. It draws upon a series of interviews with business practitioners and business commentators (both Cuban and non-Cuban residents on the island). The interviews focused on the participants’ awareness of business ethics and socially responsible enterprise, and the cultural differences in assumptions and expectations relating to the concept of CSR between the Cuban and non-Cuban interviewees. We find that Cuba at this early stage of tentative marketization presents a positive role model of socially responsible enterprise. Both the highly regulated State economy and the embedded norms and values of social equity that have emerged as a consequence of Cuba’s socialist revolution facilitate business social responsibility. The relevance of this research to current debates in relation to CSR is discussed and it is argued that capitalist economies may similarly benefit from tighter regulatory control and by cultivating more pro-social business norms that prioritise ethical over economic concerns.