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Diverse types of bricks from monuments in the city of Padua (northeastern Italy) were studied using a multi-analytical approach based on spectrophotometry, X-ray fluorescence (XRF), X-ray powder diffraction (XRPD), polarized-light optical microscopy (POM) and/or high-resolution scanning electron microscopy with coupled energy-dispersive X-ray spectroscopy (HRSEM-EDS). The most representative bricks were yellow or beige and in well-preserved condition. The results showed that they were made of Mg- and Ca-rich illitic clays, were fired at high temperatures (from 900 to over 950 ∘C), and achieved an incipient vitrification. Two main processes took place during firing: (i) the development of a Ca-aluminosilicate amorphous phase where very abundant pyroxene-type crystals were nucleated and (ii) the transformation of the pristine Mg-rich clayey grains into Mg-silicate mineral phases. The analyses suggest a firing dynamic within a highly reactive and supersaturated unstable system, particularly rich in calcium and magnesium. There are also signs of the rapid heating and/or soaking of the bricks and the irregular heat distribution and/or different residence times inside the kilns. The formation of zeolite and calcite secondary phases was also observed. The former was largely promoted by the high calcium content of the bodies and the very humid conditions, while the latter was mainly precipitated from Ca-rich solutions. The preservation of the bricks was enhanced by processes that took place both during and after firing. Firstly, the significant development of a Ca-rich amorphous phase and of high-temperature pyroxene-type crystals has provided strength to the bricks. Secondly, the porosity yielded by the firing of the carbonate-rich clays was almost filled by secondary calcite, which acted as a cementing agent. The information attained has increased the knowledge of (i) the mineralogical and microstructural changes that take place during the firing over 900 ∘C of Ca- and Mg-rich illitic clays and (ii) the formation of secondary phases within highly calcareous bricks laid in very humid environments and affected by Ca-rich solutions. The key role of the Ca- and Mg-rich raw clays and of the high firing temperatures, in producing high-quality bricks, and of the secondary calcite, which increased their durability, is highlighted. All these factors have contributed to the better preservation of the built heritage of the city.

Natural stone has long been used as a building material because of its physical-mechanical resistance and its esthetic appeal. However, over the last century increasing industrial activity has produced more acidic environments, such as polluted urban areas, that can cause serious damage to many buildings and historic monuments, and in particular those made with carbonate rocks, which are most prone to decay. In order to mitigate the physicochemical processes that degrade these buildings, a number of phosphate-based consolidants have been developed, which are highly compatible with the carbonated substrate. Research about the role of the surface and its different possible finishes in the transmission of the agents that damage or protect the stone would therefore be very useful, both when choosing the most suitable stone for new constructions and when restoring historic buildings. The main objective of this research was to determine whether the roughness of three types of surface finish (saw-cut, honed and bush-hammered) influences the durability of four types of natural stone (two calcarenites, one travertine and one sandstone) widely used in Andalusia (Spain). The efficacy of a calcium phosphate-based consolidant as a mitigator of deterioration in polluted urban environments was also studied and to this end the physical properties of untreated and treated samples were measured and compared. The samples were exposed to artificial atmospheres with SO2 pollution in order to assess the damage caused to each surface finish. The results indicate that all the surface finishes were vulnerable to the decay caused by acidic atmospheres, although the saw-cut finish was less affected, perhaps because it did not require additional industrial processing. The mineral composition and texture of the rocks were critical factors in terms of the amount and type of decay they suffered, and the travertine and sandstone were more resistant to deterioration than the calcarenites. Similarly, the pore system of each rock was decisive in the penetration of the consolidant. Application of the consolidant improved the behavior of the treated samples by making them more resistant to acid attack without significantly altering the water vapor permeability, the color or the roughness of the surface.

We evaluated the consolidating capacity of ethyl silicate in three types of bricks fired at 800, 950 and 1100 °C. We chose two concentrations of product, at 25% and 50%, diluting the product in white spirit to estimate whether greater dilution enables the product to penetrate deeper into the bricks, or whether a higher concentration leads to better consolidation of bricks. The application of ethyl silicate caused bricks porosity to decline and their compactness to increase. These changes were more accentuated as the concentration of the product increased. The pore size distribution not changed substantially except that there were fewer of the smallest pores. The color and the lightness of the pieces changed after application of the consolidant, albeit slightly. The durability of bricks improved as manifested by the results of the salt crystallization test. In general, the longest-lasting pieces were those treated with 25% ethyl silicate.

This work focuses on the chemical-mineralogical, textural and physical-mechanical properties of hydraulic lime mortars made with siliceous and calcareous aggregate. Mortars were cured at 60% and 90% of relative humidity, so as to assess the variability of mortar petrophysical properties in the hardened state due to the moisture conditions. The final aim was to determine the most adequate moisture conditions to be maintained during application and hardening of hydraulic mortars intended for repair interventions. We found out that using a calcareous aggregate and curing mortar at 90% of relative humidity give place to better textural and mechanical properties. However, these characteristics mostly depend on the maximum size of the aggregate grains, which should be smaller than 6 mm, in order to avoid the occurrence of mechanical discontinuities in the mortar.

The technical and intellectual capabilities of past societies are reflected in the monuments they were able to build. Tracking the provenance of the stones utilised to build prehistoric megalithic monuments, through geological studies, is of utmost interest for interpreting ancient architectures as well as to contribute to their protection. According to the scarce information available, most stones used in European prehistoric megaliths originate from locations near the construction sites, which would have made transport easier. The Menga dolmen (Antequera, Malaga, Spain), listed in UNESCO World Heritage since July 2016, was designed and built with stones weighting up to nearly 150 tons, thus becoming the most colossal stone monument built in its time in Europe (c. 3800-3600 BC). Our study (based on high-resolution geological mapping as well as petrographic and stratigraphic analyses) reveals key geological and archaeological evidence to establish the precise provenance of the massive stones used in the construction of this monument. These stones are mostly calcarenites, a poorly cemented detrital sedimentary rock comparable to those known as 'soft stones' in modern civil engineering. They were quarried from a rocky outcrop located at a distance of approximately 1 km. In this study, it can be inferred the use of soft stone in Menga reveals the human application of new wood and stone technologies enabling the construction of a monument of unprecedented magnitude and complexity., (© 2023. The Author(s).)

This paper studies the effects of using 20, 40 and 60% vol. of either expanded polystyrene (EPS) or olive stones as additives in the manufacture of handmade bricks. The bricks were made using clayey earth from Viznar (Spain) and were fired at 950 °C. The effects of the additives on the mineralogical, textural and physical properties of the fired bricks were analysed, focusing mainly on possible changes in their pore system, thermal insulation, compressive strength, colour and salt crystallisation resistance. From a mineralogical point of view, the bricks made with olive stones had a lighter red colour due to their lower hematite content. As expected, the samples made with these additives had greater porosity and better thermal insulation. However, they also had lower compressive strength to the point that the only samples that met the recommended criteria for general construction work were those with 20% vol. EPS, while those with 40% vol. EPS met the criteria to be used as lightweight bricks. Both additives improved the resistance of the bricks to decay by salt crystallisation.

Archaeological lime mortars from the Tower Keep and West perimeter wall of Irulegi Castle (Navarre, Spain) were analysed to determine susceptibility to deterioration. Chemical, mineralogical, textural and physical characterisation was performed by different tests and multianalysis techniques in order to determine the intrinsic features of the original historical mortars at the castle. Samples from the Tower Keep are more prone to deteriorate compared with the West perimeter wall due to high water absorption capacity and high porosity. A high degree of pore interconnection, high desorption index and the presence of high pore volume in the 0.01 to 1 µm size range affect the mortar durability since pores retain water longer inside the mortar. Local environment conditions with persistent annual rainfall, high humidity and temperature variations contribute to the decay process of the original mortar. Characterisation of historical mortars not only allows better understanding of susceptibility to deterioration but also helps the design of compatible and durable repair mortar for future interventions on historical heritage. Compatibility of new materials with the historical mortar will be ensured by studying mortar characteristics and properties.

Hemp-based composites are eco-friendly building materials as they improve energy efficiency in buildings and entail low waste production and pollutant emissions during their manufacturing process. Nevertheless, the organic nature of hemp enhances the bio-receptivity of the material, with likely negative consequences for its long-term performance in the building. The main purpose of this study was to study the response at macro- and micro-scale of hemp-lime renders subjected to weathering simulations in an environmental cabinet (one year was condensed in twelve days), so as to predict their long-term durability in coastal and inland areas with Mediterranean, Tropical and Semi-arid climates, also in relation with the lime type used. The simulated climatic conditions caused almost unnoticeable mass, volume and colour changes in hemp-lime renders. No efflorescence or physical breakdown was detected in samples subjected to NaCl, because the salt mainly precipitates on the surface of samples and is washed away by the rain. Although there was no visible microbial colonisation, alkaliphilic fungi (mainly Penicillium and Aspergillus) and bacteria (mainly Bacillus and Micrococcus) were isolated in all samples. Microbial growth and diversification were higher under Tropical climate, due to heavier rainfall. The influence of the bacterial activity on the hardening of samples has also been discussed here and related with the formation and stabilisation of vaterite in hemp-lime mixes. This study has demonstrated that hemp-lime renders show good durability towards a wide range of environmental conditions and factors. However, it might be useful to take some specific preventive and maintenance measures to reduce the bio-receptivity of this material, thus ensuring a longer durability on site., (Copyright © 2015 Elsevier B.V. All rights reserved.)

The benefits of using sustainable building materials are linked not only to the adoption of manufacturing processes that entail reduced pollution, CO2 emissions and energy consumption, but also to the onset of improved performance in the building. In particular, hemp-lime composite shows low shrinkage and high thermal and acoustic insulating properties. However, this material also shows a great ability to absorb water, an aspect that can turn out to be negative for the long-term durability of the building. For this reason, the hygric properties of hemp-based composites need to be studied to ensure the correct use of this material in construction and repair works. The water absorption, drying and transpirability of hemp composites made with aerial (in the form of dry powder and putty) and hydraulic limes were investigated here and related to the microbial growth induced by the water movements within the material. Results show that hemp-natural hydraulic lime mixes exhibit the highest transpirability and drying rate, the lowest water absorption by immersion and capillary uptake and the least intense microbial attack and chromatic change. A microscopical study of the hemp shives also related their great ability to absorb water to the near-irreversible swelling of their structure under dry-wet conditions.