New Materials and Technologies for Durability and Conservation of Building Heritage

The increase in concrete structures’ durability is a milestone to improve the sustainability of buildings and infrastructures. In order to ensure a prolonged service life, it is necessary to detect the deterioration of materials by means of monitoring systems aimed at evaluating not only the penetration of aggressive substances into concrete but also the corrosion of carbon-steel reinforcement. Therefore, proper data collection makes it possible to plan suitable restoration works which can be carried out with traditional or innovative techniques and materials. This work focuses on building heritage and it highlights the most recent findings for the conservation and restoration of reinforced concrete structures and masonry buildings

The evolution of primate short-term memory

Short-term memory is implicated in a range of cognitive abilities and is critical for understanding primate cognitive evolution. To investigate the effects of phylogeny, ecology and sociality on short-term memory, we tested the largest and most diverse primate sample to date (421 non-human primates across 41 species) in an experimental delayed-response task. Our results confirm previous findings that longer delays decrease memory performance across species and taxa. Our analyses demonstrate a considerable contribution of phylogeny over ecological and social factors on the distribution of short-term memory performance in primates; closely related species had more similar short-term memory abilities. Overall, individuals in the branch of Hominoidea performed better compared to Cercopithecoidea, who in turn performed above Platyrrhini and Strepsirrhini. Interdependencies between phylogeny and socioecology of a given species presented an obstacle to disentangling the effects of each of these factors on the evolution of shortterm memory capacity. However, this study offers an important step forward in understanding the interspecies and individual variation in short-term memory ability by providing the first phylogenetic reconstruction of this trait’s evolutionary history. The dataset constitutes a unique resource for studying the evolution of primate cognition and the role of short-term memory in other cognitive abilities

FTIR spectroscopy structural analysis of the interaction between Lactobacillus kefir S-layers and metal ions

FTIR spectroscopy was used to structurally characterize the interaction of S-layer proteins extracted from two strains of Lactobacillus kefir (the aggregating CIDCA 8348 and the non-aggregating JCM 5818) with metal ions (Cd+2, Zn+2, Pb+2 and Ni+2). The infrared spectra indicate that the metal/protein interaction occurs mainly through the carboxylate groups of the side chains of Asp and Glut residues, with some contribution of the NH groups belonging to the peptide backbone. The frequency separation between the νCOO− anti-symmetric and symmetric stretching vibrations in the spectra of the S-layers in presence of the metal ions was found to be ca. 190 cm−1 for S-layer CIDCA 8348 and ca. 170 cm−1 for JCM 5818, denoting an unidentate coordination in both cases. Changes in the secondary structures of the S-layers induced by the interaction with the metal ions were also noticed: a general trend to increase the amount of β-sheet structures and to reduce the amount of α-helices was observed. These changes allow the proteins to adjust their structure to the presence of the metal ions at minimum energy expense, and accordingly, these adjustments were found to be more important for the bigger ions

Electrical resistivity and electrical impedance measurement in mortar and concrete elements: A systematic review

This paper aims at analyzing the state-of-the-art techniques to measure electrical impedance (and, consequently, electrical resistivity) of mortar/concrete elements. Despite the validity of the concept being widely proven in the literature, a clear standard for this measurement is still missing. Different methods are described and discussed, highlighting pros and cons with respect to their performance, reliability, and degree of maturity. Both monitoring and inspection approaches are possible by using electrical resistivity measurements; since electrical resistivity is an important indicator of the health status of mortar/concrete, as it changes whenever phenomena modifying the conductivity of mortar/concrete (e.g., degradation or attacks by external agents) occur, this review aims to serve as a guide for those interested in this type of measurements

Continuous monitoring of the health status of cement-based structures: electrical impedance measurements and remote monitoring solutions

The continuous monitoring of cement-based structures and infrastructures is fundamental to optimize their service life and reduce maintenance costs. In the framework of the EnDurCrete project (GA no. 760639), a remote monitoring system based on electrical impedance measurements was developed. Electrical impedance is measured according to the Wenner's method, using 4-electrode arrays embedded in concrete during casting, selecting alternating current as excitation, to avoid the polarization of both electrode/material interface and of material itself. With this measurement, it is possible to promptly identify events related to contaminants ingress or damages (e.g. cracks formation). Conductive additions are included in some elements to enhance signal-to-noise ratio, as well as the self-sensing properties of concrete. Specifically, a distributed sensor network was implemented, consisting of measurement nodes installed in the elements to be monitored, then connected to a central hub (RS-232 protocol). Nodes are realized with an embedded unit for electrical impedance measurements (EVAL-AD5940BIOZ board with AD5940 chip, by Analog Device) and a digital thermometer (DS18B20 by Maxim Integrated), enclosed in cabinets filled with an IP68 gel against moist-related problems. Data are available on a Cloud through Wi-Fi network or LTE modem, hence can be accessed remotely via a use-friendly multi-platform interface

Piezoresistive behaviour of mortars loaded with graphene and carbon fibers for the development of self-sensing composites

In recent years, infrastructures have become of primary importance for society and for the economic development. This led to the introduction of monitoring systems for their protec-tion, and for an eco-friendly saving of resources for their maintenance. In the field of rein-forced concrete, there is a growing interest for the introduction of conductive cement-based composites for monitoring the health of structures through the evaluation of their electronic parameters. In this work, resistivity and piezoresistivity of mortars added with graphene nano-platelets (GNP), and carbon fibers (CF) were evaluated. The variations in electrical resistivity as a function of strain were analyzed under cyclic uniaxial compression of the mortars sam-ples. The results shown a high piezoresistivity behavior of the mortars with an optimal disper-sion of GNP and CF, with a quite reversible relation between fractional change in resistivity (FCR) and compressive strain

Automated measurement system for detecting carbonation depth: Image-processing based technique applied to concrete sprayed with phenolphthalein

This paper aims at discussing an automated measurement system for detecting carbonation depth in concrete sprayed with phenolphthalein. Image processing and Convolutional Neural Networks strategies are exploited to accurately separate the carbonated and non-carbonated areas and to remove those aggregates on the carbonation front that could bring to a wrong evaluation of the carbonation depth. Very strong correlation (R2 = 0.96) is found between results provided by the proposed approach and the method suggested by the EN 13295 standard. The expanded uncertainty (coverage factor k = 2) of this novel approach is 0.08 mm. ANOVA analysis performed in multi-operator tests proved that the highest source of uncertainty is the measurement system, which, on the other hand, is robust to changes in the operator performing the measurement

Automated measurement system for detecting carbonation depth: Image-processing based technique applied to concrete sprayed with phenolphthalein

This paper aims at discussing an automated measurement system for detecting carbonation depth in concrete sprayed with phenolphthalein. Image processing and Convolutional Neural Networks strategies are exploited to accurately separate the carbonated and non-carbonated areas and to remove those aggregates on the carbonation front that could bring to a wrong evaluation of the carbonation depth. Very strong correlation (R2 = 0.96) is found between results provided by the proposed approach and the method suggested by the EN 13295 standard. The expanded uncertainty (coverage factor k = 2) of this novel approach is 0.08 mm. ANOVA analysis performed in multi-operator tests proved that the highest source of uncertainty is the measurement system, which, on the other hand, is robust to changes in the operator performing the measurement