THE USE OF MULTIPLE COMBINED NON DESTRUCTIVE TESTING IN THE CONCRETE STRENGHT ASSESSENT : APPLICATIONS ON LABORATORY SPECIMENS
In this paper a series of non-destructive tests has been performed with the purpose to investigate on the mechanical properties of the concrete employed in the civil buildings. A series of specimens were prepared in order to correlate the “in situ” concrete strengths obtained by multiple combinated non-destructive methods with the cubical and cylindrical strength obtained by destructive methods. The multiple combined methods (SonReb Methods + Windsor Probe Tests) were used to quality control and strength estimation of the concrete. In particular, a series of specimens by aggregates having various Mohs’Hardness (inert of fluvial origin) and by aggregate with only a class of Mohs’Hardness (crushed aggregate) has been prepared. During the concrete casting a series of cubical specimens has been prepared. The comparison among non-destructive tests, cubical strength and cores strength are carried out.
1 The Use of Destructive and non Destructive Testing 2 in Concrete Strength Assessment for a School 3 Building 4 5
The present paper aims to increase knowlodge of the methods of resistance estimating of 13 concrete in situ by means of non-destructive tests used to integrate the quantitative results from 14 cylindrical specimens (core). The results of experimental investigations carried out on concrete 15 conglomerate samples of a school building are shown. The experimental campaign then will be 16 presented like a case study, conducted on a series of concrete beams and pillars of an existing 17 building. The destructive tests on cores were conducted at the Civil Structures Laboratory of the 18 Engineering Department of the University of Campania "Luigi Vanvitelli". The expression obtained 19 through the calibration procedure of the values of non-destructive tests with those provided by the 20 core drills allowed to estimate the average values of the compressive strength of the concrete. It is 21 highlighted how this result was achieved with a very limited core number provided that they are 22 extracted in selected points and that there was a proportionality link with the resistances obtained 23 from non destructive tests. 24
In search of optimum chest radiography techniques.
A nation-wide study of chest radiography in Sweden had previously revealed a large variation in the physical and technical factors involved, in particular the radiation dose. In this study the image quality could not be assessed unambiguously. The aim of the present study was to try to establish a correlation between visual grading of radiographs and physical and technical factors in order to find the optimum chest X-ray system. The physical and technical performance of 24 chest units was evaluated. Radiographs were taken of an anthropomorphic chest phantom supplied with test structures simulating various pathologies. Image quality was assessed by visual grading analysis of the radiographs. The physical and technical parameters of the units rated best were used to exemplify good radiographic practice. The results were in agreement with the recommendations issued by the Commission of the European Communities (CEC). It was also shown that low radiation dose is compatible with high-quality radiographic imaging of the chest.