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The Alcazaba of Almería (Spain) is one of the most important Arabic fortresses of the Iberian Peninsula archaeological record. It is located in the south of Spain, on the Mediterranean coast, and its construction dates back to the late 10th century. It consists of three enclosures, two of which belong to the Andalusian period, while the last one dates from the 16th century. However, very few materials’ studies have been performed in this complex, despite the incomparable historic relevance. In this study, we present an extensive mineralogical and physical-chemical characterization of the construction materials of this site, divided in mortars, earthen materials and bricks. We provide an unprecedent scientifical-technical study of the building materials of this fortress, so as to understand the building techniques used and the causes of deterioration. All collected samples were analyzed by means of X-ray diffraction, scanning electron microscopy, optical microscopy thermogravimetric analysis and stereo-zoom microscopy. Our results reveal that main phases used for construction materials on this site were Ca and Mg-carbonates, accompanied by Fe-Ca-Mg silicates. Mortars showed a carbonate-binder composition with non-hydraulic nature whereas calcination of raw materials occurred below 800 ºC due to the permanence of dolomite. Furthermore, we demonstrated that the construction materials from the Alcazaba suffered such relevant damages due to the precipitation of salts (i.e., gypsum and halite) caused by coastal environment, key information for future archaeological restoration work in this highly significant location. We show that, in mortars and earthen materials, halite nucleates in fractures and dissolution pits exerting a crystallization pressure ∼ 100 MPa to cause fracture. Furthermore, calcium and magnesium silicate hydrates were observed confirming some pozzolanic properties. Finally, the bricks studied here demonstrated that firing T maximum of 700 ºC due to the presence of carbonates. This work opens new pathways to develop specific consolidation methods of materials and structural elements, as well as to ensure adequate restoration and conservation, of similar archaeological sites in coastal-related environments

Reducing energy consumption in the building sector has driven the search for more sustainable construction methods. This study explores the potential of cork-modified mortars reinforced with basalt fabric, focusing on optimizing both mechanical and hygroscopic properties. Six mortar mixtures were produced using a breathable structural mortar made from pure natural hydraulic lime, incorporating varying percentages (0–3%) of cork granules (Quercus suber) as lightweight aggregates. Micro-computed tomography was first used to assess the homogeneity of the mixtures, followed by flow tests to evaluate workability. The mixtures were then tested for water absorption, compressive strength, and adhesion to tuff and clay brick surfaces. Adhesion was measured through pull-off tests, to evaluate internal bonding strength. Additionally, this study examined the relationship between surface roughness and bond strength in FRLM composites, revealing that rougher surfaces significantly improved adhesion to clay and tuff bricks. These findings suggest that cork-reinforced mortars offer promising potential for sustainable construction, achieving improved hygroscopic performance, sufficient mechanical strength, internal bonding, and optimized surface adhesion.

A favorable environment for fungi colonization in building materials’ surfaces can emerge when certain hygrothermal conditions occur. Thus, reducing fungal growth susceptibility is of major interest. Furthermore, if the integration of bio-wastes is performed in parallel with the development of innovative materials for this purpose, a more sustainable and environmentally friendly material can be obtained. In this study, the fungal susceptibility of lime mortars incorporating almond-shell powder (ASP) microparticles (2 and 4%, wt.–wt. in relation to the binder content) was evaluated. The particle-dispersion technique was employed to prepare the bio-waste introduced in the mixtures. The fungal susceptibility of ASP samples was compared with nanotitania (n-TiO2) with recognized antifungal properties. Mechanical strength, water absorption, and wettability tests were also performed for a better characterization of the composites. Although the addition of 2% ASP led to mechanical properties reduction, an increase in the compressive and flexural strength resulted for 4% of the ASP content. Difficulties in fungal growth were observed for the samples incorporating ASP. No fungal development was detected in the mortar with 2% of ASP, which may be correlated with an increase in the surface hydrophobic behavior. Furthermore, mortars with ASP revealed a reduction in water absorption by capillarity ability, especially with 4% content, suggesting changes in the microstructure and pore characteristics. The results also demonstrated that an improvement in the physical and mechanical properties of the lime mortars can be achieved when ASP microparticles are previously subjected to dispersion techniques.

Slaked lime is traditionally a suitable material for use in construction activities in historic and traditional buildings whose constitutive characteristics demand compatible and appropriate material solutions. Therefore, knowing the physical and mechanical characterization of lime pastes and mortars for use in restoration is considered an important step in the process of scientific development of a material that, in the Mexican case, has lacked scientific rigor in its production, use and commercialization. With this in mind, the present article aims to investigate the characteristics of lime pastes and mortars that have been used in the traditional way and the new limes that exist in the market, offering suitable options for restoration, for which an integrated methodology was used consisting of physical tests such as surface area, electrical resistivity, pulse velocity, colorimetry, and mechanical tests such as compressive strength, giving as a result that “traditional slaked” lime is more likely to deteriorate than powdered lime, which leads us to conclude that powdered hydrated lime has optimal characteristics for restoration activities.

Abstract The most obvious characteristics of the Ming Great Wall are external masonry walls made of natural stones, bricks and lime mortars. According to the chemical and mineralogical compositions of the original bedding and pointing mortars, dolomitic lime binder was used dominantly in the construction of the Ming Great Wall in provinces such as those around Beijing and Hebei. Calcium-rich lime and air lime with low natural hydraulically reactive phases, which are hydrated and react slowly with the carbon dioxide in air to form calcium carbonate, were used in some western provinces. Chemical and microscopic investigations show that both dolomitic and calcium-rich lime mortars are almost aggregate-free. Historic dolomitic lime mortars are characterised by high strengths, low porosities and dense micro-scale textures. The most recent conservation principle is to preserve the Ming Great Wall as a ruin. Therefore, the conservation strategy should be redefined in terms of mortars. Since some of the damage to the Great Wall is related to reactions between dolomitic lime mortars and air pollutants, calcium-rich lime binders should be used for conservation and even for restoration of those parts of the Great Wall that were originally built with dolomitic lime. Binders based on natural hydraulic lime and calcium-rich lime gauged with natural pozzolana might be more compatible than other binders” for the structural consolidation of the ruins of the Great Wall.

Today's society is increasingly aware of the conservation of architectural heritage and, at the same time, is committed to the use of new technologies in construction and the use of more sustainable construction materials. This work has a double objective, on the one hand, to develop new measurement equipment based on Arduino platform for the monitoring of moisture and temperature parameters, and on the other, to determine the evolution of these properties and the physical-mechanical characteristics of lime-based mortars used in rehabilitation works. An experimental campaign has been carried out where two types of hydraulic lime mortars have been used that differ according to the aggregate either, natural or mixed recycled ceramic. The results show how it is possible to monitor in real-time the temperature and moisture parameters in the mortars from the beginning of the setting process, which is of great relevance for the control of the execution process in restoration works. Besides, it has been possible to observe how lime mortars with recycled aggregate present good technical performance for use in rehabilitation works, although without reaching the physical and mechanical properties of traditional mortars.

This study examines the mortar materials used in the construction of the walls at the Archaeological Roman Fortification site (Ovidiu, Romania) on the shore of Siutghiol Lake. Several analyses were conducted to determine the mortars’ basic physical properties, mineralogical composition, and microstructural characteristics in order to describe the mortars used in the construction of the Roman fortress. The investigation utilized X-ray diffraction (XRD), energy dispersive X-ray fluorescence spectroscopy (XRF), scanning electron microscopy (SEM-EDAX), and differential thermal analysis (TGA-DTA). The results indicated that siliceous aggregates and lime binders were used in the production of the studied mortars, the structure was constructed in the sixth century, and the raw materials used to construct the site are of local origin. Using the methods mentioned above, there is the possibility of recreating the fortification’s mortar formula using contemporary materials and recommending intervention materials for the preservation of the archaeology of the Roman Fortification. Furthermore, this study opens up many other research opportunities regarding the reuse of mortars extracted from archaeological sites in the rehabilitation process by integrating them into new mortar recipes that can then be tested to compare the results with those obtained from standardized recipes.

Lime materials are in great demand for the restoration of the walls of historical buildings. However, lime coatings have insufficient resistance during operation. The purpose of this work was the modification of lime mortars with silicic acid sol in order to obtain more durable crystalline materials for construction purposes. A technology has been developed for obtaining a silica-containing additive, which consists in passing a liquid glass solution with a density of 1.053 kg/m3 through a cationic column and obtaining a silicic acid sol with a pH of 3–4 and a charge of (−) 0.053 V. The regeneration time and the amount of sol have been determined. Regularities of change in the radius of particles of silicic acid sol depending on age are determined. It is established that at an early age (up to 5 days), the radius of sol particles can be determined in accordance with the Rayleigh equation, and at a later age, in accordance with the Heller equation. The results of the calculation show that at the age of 1–5 days, the radius of the sol particles is 17.1–17.9 nm, and then the particles become coarser and the particle radius is 131.2–143 nm at the age of 19 days. The work of adhesion of silicic acid sol to lime and the heat of wetting are estimated. It is shown that the work of adhesion of water to lime is 28.9 erg/cm2, and that of the sol is 32.8 erg/cm2. The amount of heat Q released when lime is wetted with SiO2 sol is 15.0 kJ/kg, and when lime is wetted with water, it is 10.6 kJ/kg.

This research aims to revalue the possibilities presented by lime mortars for use in renovation and as cladding material on facades. The study focuses on analyzing the technical feasibility of lime mortars with the incorporation of residues from three types of thermal insulation materials: expanded polystyrene with graphite especially suitable for use on facades; expanded polystyrene for use indoors; and insulating mineral wool. The incorporation of these construction and demolition residues makes it possible to improve several technical performance aspects of lime mortars, and to incorporate circular economy criteria in the manufacturing process of these materials. The results showed that the incorporation of mineral wool improves the mechanical resistance to the bending of mortars, increases their durability against freeze–thaw cycles and salt crystallization, and reduces the final shrinkage of mortars. For their part, mortars with the addition of polystyrene-insulating residues reduce mechanical resistance, but also reduce thermal conductivity, and are lighter, which is why they are shown as a possible alternative for use in precast.

In addition to serving as documentation of cultural existence, historical structures are important part of the living environment. Thus, it is important to transfer them to future generations. Historical buildings that have been damaged over time due to various reasons are in need of conservation and restoration. However, methods applied with lack of scientific research can have harmful effects on the structure and create new damages. The scientific research on hydraulic, lime-based grout that is frequently used in the restoration of historical buildings is insufficient. In particular, the research on commercially sold lime-based grout needs more interest. The injection of grout is an irreversible technique and more scientific research can prevent unpredictable damages. Furthermore, although it is widely used, there are no national or international standards regarding the use of hydraulic lime-based grout. The aim of this study is to analyse the development of the grouting technique and the lime based grouts used in the restoration of buildings with historical masonry structure within the literature review context and to offer a contribution to the required standards and further scientific research. This research is an examination of the available resources in related topics in a chronologic order. First, the technique used to inject the grout during the restoration of buildings with historical masonry is described. Studies performed related to other grouts and mortars that contributed to the development of the use of hydraulic, lime-based grouts are discussed. Then, the development of the hydraulic, lime-based grout material and the test methods for this material are examined. There is also an analysis on the research performed with regard to the commercially available, hydraulic, lime-based grouts. Finally, the previous and ongoing research considering the use of this grout in Turkey is mentioned in the scope of this study.

The Church of the Company of Jesus in Quito (1605–1765) is one of the most remarkable examples of colonial religious architecture on the World Heritage List. This church has multiple constructive phases and several interventions with no clear record of the entire architectural site, including the historical mortars. A total of 14 samples of coating mortars inside the central nave were taken, with the protocols suggested by the research team and a comparative sample of the architectural group that does not have intervention. The analysis presented in this paper focuses on mineralogical characterization, semi-quantitative analysis by X-ray diffraction and scanning electron microscopy with microanalysis of the samples. The results showed the presence of volcanic aggregate lime and gypsum, used in lining mortars and joint mortars. Mineralogical and textural composition data have allowed the mortar samples to be relatively dated.

The study of external renderings in the scope of conservation and restoration has acquired in the last years great methodological, scientific and technical advances. These renderings are important elements of the built structure, for besides possessing a protection function, they possess often a decorative function of great relevance for the image of the monument. The maintenance of these renderings implies the conservation of traditional constructive techniques and the use of compatible materials, as similar to the originals as possible. The main objective of this study is to define a methodology of conservative restoration using strategies of maintenance of renderings and traditional constructive techniques. The minimum intervention principle is maintained as well as the use of materials compatible with the original ones. This paper describes the technique and products used for the consolidation of the loss of cohesion. The testing campaign was developed under controlled conditions, in laboratory, and in situ in order to evaluate their efficacy for the consolidation of old renders. A set of tests is presented to evaluate the effectiveness of the process. The results are analysed and a reflection is added referring to the applicability of these techniques. Finally the paper presents a proposal for further research.

Intervention in ancient buildings with historical and architectural value requires traditional techniques, such as the use of lime mortars for internal and external wall renderings. In order to ensure the desired performance, these rendering mortars must be rigorously specified and quality controls have to be performed during application. The choice of mortar composition should take account of factors such as compatibility with the substrate, mechanical requirements and water behaviour. The construction schedule, which used to be considered a second order variable, nowadays plays a decisive role in the selection of the rendering technique, given its effects upon costs. How should lime-based mortars be specified? How much time is required for the application and curing of a lime-based render? This paper reflects upon the feasibility of using traditional lime mortars in three-layer renders inside churches and monasteries under adverse hygrothermal conditions and when time is critical. A case study is presented in which internal lime mortar renderings were applied in a church in Northern Portugal, where the very high relative humidity meant that several months were necessary before the drying process was complete.

Portugal is one of the European countries in which built heritage is a testimony of its history. In this context, the legacy of the decorative glazed tile coatings of facades must be preserved and restored. This research is dedicated to the conservation of such facades in the city of Ovar, considered an example due to its rich heritage in glazed tiles, a high percentage of which requires a deep intervention. Therefore, this work is focused on the study of lime renders serving as a support for this type of tile facades. For this, samples were collected from several buildings in the city, targeting their mechanical and physical study with the aim of producing compatible mortars to be used for application of detached tiles in these buildings and generally for the repair of the facades with glazed tile coatings. For this purpose, four lime mortar formulations with different volumetric ratios were composed. The aggregates used were: ordinary river sand and local gravel. In three of the mixtures, metakaolin was added, with the intention of acting as an artificial pozzolan and thus improving the performance of these mortars. The use of a pozzolanic addition promotes hardening of lime mortars in cases when the ingression of carbon dioxide is low as is the case of mortars placed below glazed tile coatings. These mortars were also tested in the laboratory taking into account their physical and mechanical characteristics. The mechanical characteristics determined were: modulus of elasticity by two different methods, compressive strength and flexural strength. In turn, the physical characteristics determined were: water vapour permeability and water absorption by total immersion and capillary action. The best mechanical behaviour (compressive and flexural) was observed in the mortar with pozzolanic additions. Similarly, the value of the modulus of elasticity was better in mortars with pozzolanic additions. The performance of these mortars was also adequate in terms of water behaviour. The mortars revealed suitable characteristics for application in building conservation situations concerning coating with glazed tiles.

In the selection of materials required by any work on Architectural Heritage, a series of special requirements must be borne in mind which are essential to guarantee the application of the repairs. In this work the guidelines and basic criteria for the selection of repair mortars that have led to the design of mortars to restore the Kings Portal of the church of San Juan del Mercado (Benavente, Zamora), carved in stone in the Romanesque style and later polychromed are shown. The study is based on the characteristics of the ancient historical mortars, the compatibility of the restoration mortars with the mortars already existing in the monument, and the application needs of the specific work. Finally, the characteristics and properties of the specific repair mortar chosen are shown

Researchers have related the manufacturing technique of plasters and stucco in the Maya area with their period of production but not with their architectural function. In this paper, we establish a relationship between those three features (manufacturing technique, age, and architectural function) in the plasters of the Maya site of Dzibanché in southern Quintana Roo. Dzibanché has abundant remains of stuccos and plasters found mainly in three buildings (Plaza Pom, Pequeña Acrópolis, and Structure 2). We used thin sections, SEM and XRD, and archaeomagnetic dating processes. The pictorial layer of Structure 2 was the earliest (AD 274–316 and the stuccoes and plasters of the other two buildings were dated to the Middle Classic (AD 422–531), but we obtained different archaeomagnetic dates for the red pigment layers found in the buildings of the Pequeña Acrópolis and thus we were able to determine their chronological order of construction. The raw materials and proportions were carefully chosen to fulfil the mechanical necessities of the architectonic function: different proportions were found in plasters of floors, in the external walls, and inside the buildings; differences between earlier and later plasters were also detected.

The systematic analysis of mortars from monuments or historic buildings and the simultaneous study of the construction environment show that it was common practice to use naturally occurring sand from local rivers or streams for the production of the mortars. There are cases though, mainly on islands, where sands of natural origin were limited, and marine or crushed sands were used possibly after elaboration. In all cases the particle size analysis of old mortar confirms the presence of even distribution of the granules. As regards the design of the repair mortars, there are criteria that should be taken into consideration in order to produce materials with compatible properties. The main properties concerning sands are the grain distribution and maximum size, the color, the content of fines, and soluble salts. The objective of this research is the study of the physical characteristics of the sands such as the sand equivalent, the gradation, the apparent density, the morphology of the grains, their mineralogical composition and the influence of these properties on the behavior of lime mortars, notably the mechanical and physical properties acquired.