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

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

Calcium sulfoaluminate cement and fly ash-based geopolymer as sustainable binders for mortars

This work investigates the hydration behaviour and the physico-mechanical properties of mortars based on calcium sulfoaluminate (CSA) cements and fly ash-based geopolymers (GEO) as alternatives to ordinary Portland cement. According to the EN 1504-3, mortars were prepared in order to reach three compressive strength classes, namely R1, R2 and R3 (R1 with Rc ≥ 10 MPa, R2 with Rc ≥ 15 MPa and R3 with Rc ≥ 25 MPa). CSA mortars were prepared by using sulfoaluminate cement alone (R3) or in mixture with a limestone filler (R1 and R2); GEO mortars were manufactured by alkali-activation of coal fly ash and calcium aluminate cement with a sodium silicate and potassium hydroxide water solution. The hydration behaviour was evaluated on pastes submitted to differential thermal-thermogravimetric and X-ray diffraction analyses. Mortars was analysed through mercury intrusion porosimetry; their mechanical properties were evaluated in terms of compressive strength and dynamic modulus of elasticity. Furthermore, capillary water absorption and drying shrinkage tests were carried out in order to evaluate their durability. Due to the rapid ettringite formation, CSA-based mixtures reached their maximum compressive strength values faster than the corresponding GEO mortars. Results showed that the lower modulus of elasticity of GEO mortars causes the higher drying shrinkage. Moreover, the lower porosity exhibited by GEO mortars was responsible for the lower water capillary absorption

Behavior of Cement-Based Alkali-Activated Lightweight Mortars at High Temperatures

Six lightweight cement-based or alkali-activated mortars are investigated after being exposed to 500, 750, and 1000 °C. In the three cement-based mortars, the binder is Portland cement, with/without fly ash or metakaolin, while in the remaining three alkali-activated mortars (all devoid of Portland cement), different combinations of fly ash and metakaolin are investigated. Replacing 40% of the cement with metakaolin and replacing 50% of metakaolin with coal fly ash enhance the resistance to high temperatures of the mortars. After the exposure to 1000 °C, the high residual compressive strength of cement-based mortars containing metakaolin comes from the formation of new crystalline phases, whereas in alkali-activated mortars the high residual compressive strength comes from their high densification

Comportamento a corrosione di armature in acciaio e acciaio zincato in una malta ad attivazione alcalina a base di metacaolino dopo carbonatazione accelerata

The work presents the corrosion behavior of bare and galvanized steel rebars embedded in metakaolin alkali-activated mortar and traditional cement-based mortar belonging to the same mechanical strength class (R3 class with Rc ≥ 25 MPa, according to UNI EN 1504-3). Tests were conducted evaluating both the corrosion potential and the polarization resistance throughout the first month of curing and during the subsequent weekly wet/dry cycles in tap water after exposure to a chamber with 3% of CO2. During the first month, the high alkalinity of alkali-activated mortar delays the achievement of the passive state in particular for galvanized steel rebars, even though, after that period, they reach the same polarization resistance of those embedded in the cement-based mortar. During accelerated carbonation, the neutralization of alkalinity in alkali-activated mortar occurs more quickly than in cement-based mortar. During exposure to wet/dry cycles in tap water, both bare and galvanized steel rebars show comparable polarization resistance values in both studied mortars

The effect of superficial hydrophobic treatments to increase the frost durability of concrete evaluated by means of acoustic emission and CDF test

Reinforced concrete structures (RCS) exposed to freezing phenomena in the presence of de-icing salts are known to be subjected to the corrosion of embedded reinforcements. The penetration of aggressive substances inside concrete is related to water suction through capillary action. In order to slow down this action, concrete surface can be treated by applying hydrophobic solutions in the admixture or onto the surface. The superficial layer which is formed can modify the water contact angle and hence hinder the water penetration. This research work is focused on the durability of concrete with or without hydrophobic treatments, and exposed to freeze-thaw cycles. Four different concrete mixtures were prepared at the same aggregate/cement ratio by varying the water/binder ratios (0.50, 0.55, 0.60, 0.65). Specimens were studied in terms of mechanical and stability properties. Flexural and compressive strength tests and CDF-test after exposure of 28-days cured concrete specimens in presence of de-icing salts were performed. Acoustic emission measurements are still going on. Results obtained highlight that the application of the surface treatment with hydrophobic admixture is an important parameter for increasing the resistance of concrete to frost phenomena

Fiat Lux: fotosintesi nelle alghe di Frasassi

si è studiata la fisiologia della "lampen flora" delle grotte di Frasassi e la loro capacità di gestire periodi prolungati di buio