Ultrasonic and sonic techniques applied to concrete and masonry structures

The quality assurance during and after construction of new structures and after refurbishments, the characterization of material properties and damage due to time and environmental influences are more and more becoming a serious concern. In recent years, innovative Non Destructive Testing (NDT) techniques, applicable for the assessment of existing civil structures, have become available for in situ analysis on concrete and masonry structures, but they are still not established for regular inspections. In addition, in the civil engineering field, repairing and anti-corrosion protection of the building structure is one of the most important applications of polymer composites. Nonetheless, the adhesion between overlays and concrete or masonry substrate is a concerning factor affecting the reliability and durability of repair. During the change of environmental conditions (temperature and humidity) after curing, the need exists for adhesion monitoring in the case of large area objects like industrial floors, bridge decks, injected concrete structures. In this chapter two main objectives will be discerned. The first relates to the application of sonic and ultrasonic testing techniques to measure in situ the development in time of the mechanical properties of concrete and polymer composite. The second deals with the assessment of damage and defects in concrete or masonry, and between concrete or masonry and applied polymer composite by means of sonic and ultrasonic techniques. Different data acquisition procedures and methodologies together with example applications will be described including tomography, scanning acoustic microscope, transmission and surface measurements. Further, an impact-echo example application on post-tensioned concrete will be described. The importance of data visualisation in form of 2-D images will be discussed. All these are monitoring techniques that can be applied in situ after their validation in laborator

Ultrasonic pulse velocity test for non-destructive investigations of historical masonries: an experimental study of the effect of frequency and applied load on the response of a limestone

The ultrasonic pulse velocity (UPV) method can be conveniently used for non-destructive testing of physical–mechanical properties of the stones within historical masonry, as well as to check the state of damage and microcracking. Before to proceed with in situ measurements, it is important to assess the contribution that both intrinsic characteristics of the stones and external factors may give to the ultrasonic response. In this work the effect of different wave frequencies, sample geometry and application of a compression load on the response of a natural stone to UPV test has been investigated. An extensive experimental campaign in laboratory conditions was carried out on a soft limestone, used in the historical building heritage of the Southern Italy. A negligible UPV dispersion was found at the used frequencies of 1 MHz, 120 and 55 kHz when a compression load was not applied; the measured velocities were found to be influenced by the stone inhomogeneity rather than by the sample size. They showed a slight decrease and still negligible dispersion under load up to the visible damage. Dispersion increased with the cracking progression. This indicates that enhanced capability of UPV, in checking material quality and damage conditions, can be obtained by combining the use of different wave frequencies

Thermo-hygrometric behavior of hempcrete walls for sustainable building construction in the Mediterranean area

Recent studies have demonstrated that the use of natural materials represents one of the pathways to achieve energy efficiency and environmental sustainability in buildings. In the framework of Circular Economy policies aimed at reducing the consumption of raw materials, shives, as an agricultural by-product of hemp cultivation, have gained a renovated life in the construction sector. Among all the building products made of hemp, hempcrete blocks are the most innovative, because they represent the solution to the needs of new and traditional buildings, offering a high energy saving, combined with the sustainability of materials and products, while remaining, in terms of shape and size, very close to the culture and the construction systems best known by professionals. In order to assess the potential benefits of hempcrete in the construction sector, its environmental performances were evaluated using the LCA methodology, following the international standard ISO 14044:2006+A1:2018 and in compliance with the European standard EN 15804:2012+A1:2013. To this purpose, four non-loadbearing walls were compared in the "cradle-to-gate" scenario, one made with hempcrete blocks and the others with more "traditional" materials. This research aims to be a basis for the development of future guidelines at national and international level in order to guarantee the maximum diffusion of this type of product also in the Mediterranean area. For this reason, it is important to identify the performance characteristics essential for hempcrete products studying their behavior not only as defined in the UNI EN ISO 12571, 2013 standard, but also in the Mediterranean climate. To achieve these objectives, some tests have been carried out to verify the thermo-hygrometric behavior. A 1 m2 of hempcrete wall was submitted to tests in a climatic chamber which simulated the environmental conditions typical of the south of Italy, in terms of temperature and moisture, in order to evaluate thermo-hygrometric behavior of hempcrete. Sensors and thermo-flowmeters for parameter analysis were applied on the wall. On the same material was carried out hygroscopic sorption tests as defined in the UNI-EN-ISO12571,2013 standard. The behavior detected by the experimental measurements on the masonry was compared with the simulated numerical behavior using WUFI software

Characterization of the kinetic behaviour of resin modified glass ionomer cements by DSC, TMA and ultrasonic wave propagation

none4Micelli, Francesco; Maffezzoli, Alfonso; Terzi, R; Luprano, V. A. M.Micelli, Francesco; Maffezzoli, Alfonso; Terzi, R; Luprano, V. A. M