Calculation of t8/5 by response surface methodology for electric arc welding applications

[EN] One of the greatest difficulties traditionally found in stainless steel constructions has been the execution of welding parts in them. At the present time, the available technology allows us to use arc welding processes for that application without any disadvantage. Response surface methodology is used to optimise a process in which the variables that take part in it are not related to each other by a mathematical law. Therefore, an empiric model must be formulated. With this methodology the optimisation of one selected variable may be done. In this work, the cooling time that takes place from 800 to 500ºC, t8/5, after TIG welding operation, is modelled by the response surface method. The arc power, the welding velocity and the thermal efficiency factor are considered as the variables that have influence on the t8/5 value. Different cooling times,t8/5, for different combinations of values for the variables are previously determined by a numerical method. The input values for the variables have been experimentally established. The results indicate that response surface methodology may be considered as a valid technique for these purposes.Valcuende Payá, MO. (2014). Calculation of t8/5 by response surface methodology for electric arc welding applications. Thermal Science. 18(1):149-158. doi:10.2298/TSCI130418162VS14915818

QSI methods for determining the quality of the surface finish of concrete

[EN] The surface finish of a concrete element may become an index of its quality, relating the external and internal porosity with the mechanical and durability properties. Few methods are used to determine the surface quality of concrete elements. Mention must be made the Quality Surface Index (QSI) proposes a simplified method to quantify the surface occupied by the pores in relation with the total surface inspected, analyzing groups of pores by their diameter. The method of the CIB W29 (Commission W29 "Concrete Surface Finishings") proposes an inspection of the concrete element and its visual comparison with some standard templates. Finally, the digital processing of images allows the zones with surface defects to be delimited and quantified according to premises of quality introduced into the control software. These three methods are employed in this work and are applied in three concrete walls situated three meters from the observer (M-1, M-2 and M-3). Following the conversion of the results of the method with ImageJ and QSI, the results suppose differences that go from 0.1 tenths (2%) for M-3 up to 0.3 tenths (8%) for M-1. All values are within the obtained range with CIB W29 templates. This can validate the QSI and digital processing methods and allows a quick verification of the results. With the digital method, it is obtained that 23.5% of the total pores of M-1 have a diameter of less than 10 mm(2) and 44% of less than 100 mm(2). For M-2 and M-3 the proportions of pores with a dimension below 10 mm(2) is of 43.1% and 27.7%, respectively, and that 77.5% and 60.7% are smaller than 100 mm2. From all the above it can be highlighted that M-1 is the one with the lowest amount of pores, however the proportion of the largest is greater than for M-2 and M-3. In the case of M-3, although it has a lower proportion of larger pores than M-1, its greater amount means it is the worst in terms of surface finish of the three.Benito-Saorín, FJ.; Miñano-Belmonte, I.; Parra Costa, C.; Rodríguez-López, C.; Valcuende Payá, MO. (2018). QSI methods for determining the quality of the surface finish of concrete. Sustainability. 10(4):931-1-931-14. https://doi.org/10.3390/su10040931S931-1931-1410

Potentiometric thick-film sensors for measuring the pH of concrete

Concrete carbonation is one of the main triggers of the corrosion process and hence of the premature deterioration of concrete reinforcements. In order to monitor and control the carbonation process, a potentiometric sensor using thick-film technology was developed. This paper includes the results of the research carried out to characterise the pH sensor, including the materials, response time, sensitivity, detection limit, reproducibility, reversibility and the study of chloride interference. The sensors have been studied in pore solutions and concrete specimens. The study shows that the thick-film sensor has a potentiometric response to variations in pH and is capable of providing continuous, real-time information on the progress of the carbonation front.The pre-doctoral scholarship was granted to Roman Bataller Prats by the Research Staff Training Program, "Formacion de Personal Investigador (FPI) 2012" from Universitat Politecnica de Valencia and to Jose Enrique Ramon Zamora by the University Faculty Training Program FPU13/0091, "Formacion del Profesorado Universitario (FPU) 2013" from the Spanish Ministry of Science and Innovation. The financial support from the Spanish Government and the European FEDER funds MAT2012-38429-004-04. ETSIE (UPV) by their support to the laboratory is also gratefully acknowledged.Gandía-Romero, JM.; Campos, I.; Valcuende Payá, MO.; García Breijo, E.; Marcos Martínez, MD.; Paya Bernabeu, JJ.; Soto Camino, J. (2016). Potentiometric thick-film sensors for measuring the pH of concrete. Cement and Concrete Composites. 68(2016):66-76. doi:10.1016/j.cemconcomp.2016.02.006S667668201