Search Results (17)

The objective of this investigation is to understand how to use waste tires to surround stone pillars and mix gravel with recycled asphalt pavement (RAP) and stone pillars to provide an environmentally friendly and cost-effective weak layer improvement method. To study the behavior of such stone columns, experiments were conducted in units consisting of a single stone column with recycled asphalt pavement as filling material and a single stone column covered with old tires. To test the effect of different mixing ratios, rapeseed content was selected from 0% to 100%. Elasticity tests were conducted on cladded and nonclad stone column samples. Furthermore, direct shear tests were conducted on samples with different ratios of gravel and rapeseed mixtures. The results of the load-bearing capacity test show that the cover of the stone columns with old tires can significantly increase the load-bearing capacity. Replacing 25% of natural stone column aggregates with RAP increases the load capacity. But as the percentage of RAP in the mixture increases from 25% to 100%, the loading capacity decreases. Another advantage is the reinforced stone column. From the point of view of ecology, an advantage is the use of recyclable materials. Full article

The biodeterioration of the natural surface on monuments, historical buildings, and even public claddings brings to the attention of researchers and historians the issues of conservation and protection. Natural stones undergo changes in their appearance, being subjected to deterioration due to climatic variations and the destructive action of biological systems interfering with and living on them, leading to ongoing challenges in the protection of the exposed surfaces. Nanotechnology, through silver nanoparticles with strong antimicrobial effects, can provide solutions for protecting natural surfaces using specific coupling agents tailored to each substrate. In this work, surfaces of two common types of natural stone, frequently encountered in landscaping and finishing works, were modified using siloxane coupling agents with thiol groups. Through these agents, silver nanoparticles (AgNPs) were fixed, exhibiting distinct characteristics, and subjected to antimicrobial analysis. This study presents a comparative analysis of the efficiency of coupling agents that can be applied to a natural surface with porous structures, when combined with laboratory-obtained silver nanoparticles, in reducing the formation of microbial biofilms, which are a main trigger for stone biodeterioration. Full article

Heritage buildings clad with natural rock endure over time destruction caused by weathering mechanisms, pollution from urban areas, biodeterioration due to organisms, microorganisms, and also the anthropic factor. On the surface of the limestone samples taken from the ornamental natural rock with which the outside of Markovits-Mathéser house, Oradea, Romania, is clad, two species of fungi were inoculated in the laboratory: Aspergillus spp. and Cladosporium spp. Wollastonite was then applied, and from the imaging analysis (SEM), the inhibition of fungi by it is clearly observed (48 h after its application), which was also confirmed using the image segmentation method. It was also noted that the hydrophilicity of the aqueous suspension of wollastonite resulted in the absorption of water in the substrate, which in turn resulted in the drying out and surface breakage of the specimens. X-ray diffraction analysis showed the presence of the two phases (calcite and quartz) as in the starting sample, and also an additional phase assigned to wollastonite in the later phase of the experiment. An amorphous component, due to the applied gel composition, was also reported. This research highlights the fact that there are good premises for aqueous suspension of wollastonite to have a biocidal character for Aspegillus spp. and Cladosporium spp., when applied on natural stone used in the construction of heritage buildings located in temperate climates; due to its easy application, green and ecofriendly properties, and also low cost of acquisition and application. Full article

The long-term endurance of building stones must be assured since their longevity has repercussions for their economic and social value. Frequently, slabs for flooring and cladding are installed with polished finishing in outdoor environments for technical and ornamental purposes in cultural heritage sites and modern civil architecture. Compared to any other finishing, glossy surfaces are rather vulnerable to wear, particularly when they interact with slightly acidic rainwater. Several hydrophobic treatments are applied to prevent this damage by preventing contact between rain and stone; such treatments are efficient but sometimes non-durable. Stakeholders and conservation scientists need better methods to anticipate the future behaviour of this building material and hydrophobic solutions. Complying with this demand, a comparison is made between outdoor natural ageing and artificial weathering, reproduced by UVA radiation, moisture and spray accelerated weathering. Artificial weathering is applied to predict the behaviour of stones over time in the real environment. Data obtained through the measurement of gloss and colour parameters, the detection of micro-textures through SEM, and the calculation of micro-roughness using a digital rugosimeter demonstrate that weakly acidic rainwater is the main cause of superficial decay of stone finishing over just six months of outdoor exposure. This period corresponds to 7–14 days of artificial weathering. Furthermore, the loss of efficiency and durability of the hydrophobic coatings is detected by measuring the static contact angle. This highlights that even if a protective treatment was proficient, it could easily deteriorate in normal weathering conditions if applied on polished, low-porosity stone. Additionally, water vapour permeability indicates variations of regular vapour transmission through the stones due to ageing. The first solution to threats is the prevention of pathologies, including aesthetic ones. A careful choice of the most suitable lithotype finish and an environmental study represent an existing solution to the problem. It must be highlighted that aesthetic requirements should not be prioritised to detriment of the technical requirements of architectural quality, performance, durability, and safety. Full article

Light-transmitting concrete as a building material already exists in many forms, but its light properties and the possibilities of using it to improve the lighting of interior spaces have not been investigated in detail yet. This paper focuses on the illumination of interior spaces using constructions made of light-transmitting concrete, which will allow light to pass between individual spaces. The experimental measurements carried out are divided into two typical situations using reduced room models. The first part of the paper focuses on the illumination of the room through the penetration of daylight through the ceiling made of light-transmitting concrete. The second part of the paper investigates the transmission of artificial light from one room to another through a non-load-bearing dividing structure composed of unified slabs of light-transmitting concrete. For the experiments, several models and samples were created for comparison. The first step of the experiment was to create slabs of light-transmitting concrete. While there are many options to produce such a slab, the best option is to use high-performance concrete with glass-fiber reinforcement, which improves the load transfer properties, and plastic optical fibers for light transmission. By adding optical fibers, we can achieve the transmission of light between any two spaces. For both of the experiments, we used reduced-scale models of rooms. Slabs with dimensions of 250 × 250 × 20 mm and 250 × 250 × 30 mm were used in three versions: concrete slabs with optical fibers, concrete slabs with air holes and solid slabs. The experiment measured and compared the level of illumination at several points in the model as it passed through each of the three different slabs. Based on the results of these experiments, it was concluded that the interior level of illumination of any space can be improved by using light-transmitting concrete, especially those without access to natural light. The experiment also assessed the strength properties of the slabs in relation to their intended use and compares them with the properties of stone slabs used as cladding. Full article

The evaluation of stone cladding material suitability can be a challenge due to the way that stone physical and mechanical properties, and characteristics such as mineralogy, might influence stone performance as a cladding element in a ventilated facade application. Salts can affect natural stone performance, and one of the experimental methods available to study and predict it is through accelerated aging tests such as salt fog chamber cycles. Aging test results should include the analysis of critical stone physical–mechanical properties to fully understand decay effects. The aim of this study was to reduce the lack of knowledge regarding the implications of salt fog on certain fundamental characteristics of stone cladding requirements, such as elastic properties and flexural strength, because these are particularly important properties for ventilated facade systems. A systematic methodology based on artificial salt fog cycles in a climatic chamber, microscopic analysis, weight measurement, flexural strength, and dynamic elastic modulus was performed on two limestones from Portugal: Moleanos (MO) and Semi-Rijo (SR). This study aims to contribute to improved selection stone methods linked to more sustainable stone facades, and the experimental methodology can be further applied to other stone types, particularly the ones most selected for stone cladding applications near coastal areas. In this work, results of salt fog decay cycles are presented and discussed considering their direct contribution for a better stone-cladding dimensioning process. Full article

Natural stones are a widely used construction material for both structural and decorative purposes. It is a material used for many floors and cladding due to its special beauty and quite aesthetic appearance. However, natural stones are exposed to different temperatures due to natural, urban or industrial activities and they lose their physico-mechanical properties. It is known that high temperatures and fire cause degradation of construction and building stones. There are many studies investigating the effect of high temperatures on physical and mechanical properties of natural stones, while there are very limited studies on color and gloss. In this study, the changing physical and mechanical properties, color and gloss of different light-colored polished natural stones exposed to room temperature up to 1000 °C in the oven were investigated. For this purpose, natural stones were gradually exposed to 200, 400, 600, 800 and 1000 °C, starting from room temperature. After exposure to different temperatures, water absorption, porosity, Schmidt hammer hardness, point load strength, color and gloss were measured and compared to reference samples (at room temperature). However, all samples were decayed at 1000 °C, changes at this temperature value could not be determined. The results obtained at other temperature values were evaluated separately for each parameter. While the change in physico-mechanical properties of all samples up to 400 °C was limited, a dramatic change was observed with increasing temperature. In all samples, point load strength losses were observed due to an increase in porosity and water absorption. In addition, all samples darkened at 400 °C, while the whiteness value (L*) of samples increased at 800 °C. Gloss values gradually decreased due to the increase in temperature. Full article

The buildings’ surroundings’ environmental exposure conditions (e.g., orientation, location, altitude, distance from the sea, temperature, precipitation, presence of damp, exposure to prevailing winds, among others) have a considerable influence on the performance and durability of their envelope. Furthermore, the intensity of these conditions can vary significantly with the height of the building and, consequently, influence the degradation of different parts of the same building in different ways. In a tall building, the upper part is more prone to higher solar radiation levels, temperature variations, and exposure to wind–rain action. On the other hand, external elements at the bottom are more susceptible to high levels of pollution, especially in city centres. In this sense, the main purpose of this study was to analyse the degradation processes in buildings with different heights and understand whether the processes and maintenance requirements are statistically different. A sample of 203 natural stone claddings (NSC), located in Portugal, was used as case study. The sample was collected based on the diagnosis of the degradation condition of these claddings through in situ visual inspections. To predict the degradation process of NSC over time, a stochastic service life prediction model, based on Petri nets (PN), was implemented. This model allows evaluating the performance of NSC by encompassing the uncertainty of the future performance of the claddings. The results obtained through the degradation and maintenance models were compared with real case studies to highlight the real impact of buildings’ height subjected to environmental exposure conditions on the maintainability of NSC. Full article

Façade claddings, as the outer protection layer of the building’s envelope, are directly exposed to environmental degradation agents. The façades’ orientation and their distance from the sea, among other location and protection-related factors, influence their vulnerability to climate loads, in particular wind and air humidity. These loads, as well as exposure to air pollution, affect the degradation process of claddings and the durability of façades. Therefore, studying the impact of the environmental exposure conditions on the service life of different external claddings provides useful information on their performance over time, which can support (i) decision-makers in the selection of the best façade cladding solutions and (ii) further research on the impact of climate change on building components. This study covers six types of cladding: rendered façades (R), natural stone cladding (NSC), ceramic tiling system (CTS), painted surfaces (PS), external thermal insulation composite systems (ETICS), and architectural concrete façades (ACF). Three hundred façades located in Portugal are analysed according to three main groups of variables, which characterize (i) the façades, (ii) their degradation condition, and (iii) the environmental deterioration loads and context. The statistical analysis results reveal that the environmental variables affect the cladding degradation process. South-oriented façades present lower degradation conditions than façades facing north. The distance from the sea and high exposure to pollutants add to the degradation conditions, reducing the expected service life of façades. The results reveal that claddings can be organized according to two main groups: the most durable (CTS, NSC, and ACF) and the least durable (R, PS, and ETICS) systems. This study enables a comprehensive analysis of the data, useful to draw conclusions about the influence of environmental exposure conditions on the degradation and service life of façade claddings. Full article

Accessibility to buildings’ envelope depends on efficient inspection and other maintenance actions of their components. When access to these components is not planned, special means of access are required to carry out the maintenance work. Means of access, besides having a fundamental role on the quality of maintenance works of building envelope components, also represents a considerable part of the maintenance costs. Thus, to optimize costs and resources in maintenance plans, assessment of the impact of the means of access on maintenance costs is crucial. For works in height, there are several alternative means of access. The choice of the most adequate solution is strongly linked to the characteristics (e.g., architecture, height) and constraints (e.g., users, surrounding space) of each building, the maintenance needs of the envelope, and the time and funds available for the intervention. Therefore, in this study, a sensitivity analysis to understand how the cost of means of access can influence the maintenance costs is carried out. Moreover, the optimisation of maintenance activities in façade claddings is also analysed. This study intends to assess whether it is advantageous to consider permanent means of access during the design phase or opt for temporary means of access. In a first stage, the impact of six temporary means of access (supported and suspended scaffolds; articulated booms; telescopic booms; scissor lifts; and rope access) on the maintenance plans developed for the six types of claddings (ceramic tiling systems—CTS, natural stone claddings—NSC, rendered façades—RF, painted surfaces—PS, external thermal insulation composite systems—ETICS, and architectural concrete façades—ACF) is examined. The impact is estimated through a stochastic maintenance model based on Petri nets. After that, a sensitivity analysis and a multi-criteria decision analysis are performed. Based on the results, general recommendations are presented concerning the maintenance strategies to adopt in the cladding solutions analysed. The results reveal that planning the means of access during the design stage can be economically beneficial for all buildings’ envelope components. Full article

Now more than ever, the construction sector is aiming to adopt more sustainable solutions. To achieve this purpose, more durable solutions must be adopted, making rational decisions at the design and maintenance stages regarding the conditions of environmental exposure and use. In this sense, knowledge regarding the service life of building components is crucial. This knowledge should not be a general concept, or a standard value, and adapting practices from one country to another is extremely challenging. In this sense, this study analyses the service life of natural stone claddings. We adopt a methodology initially proposed for Lisbon (Portugal), intending to evaluate its applicability to other geographical contexts, in order to perform a more reliable service life prediction of stone claddings located in Tehran (Iran). An estimated service life of 65 years was obtained for a sample of 162 stone claddings directly adhered to the substrate, located in Tehran, which were analysed by in situ inspections. The impact of different conditions (e.g., type of stone and environmental exposure conditions) on the service life of stone claddings in Tehran was quantified, which revealed that the exposure to environmental agents, such as wind, rain and pollutants, is the main cause of degradation of the natural stone claddings. Full article

Façades, as the most external building envelope component, are subject to different ex-ternal environmental loads, such as: Temperature, precipitation, damp, and wind. Therefore, the contribution of environmental actions to the occurrence of defects in façades claddings is an important subject of study since these actions strongly affect the degradation process and natural ageing of these components during their service life. In this study, a methodology to support decision-makers in the process of selecting a façade cladding system and the maintenance strategy to implement is presented and discussed. This methodology covers the performance of four façade claddings (ceramic tiling systems (CTS), natural stone claddings (NSC), external thermal insulation composite systems (ETICS), and architectural concrete façades (ACF)) over time, according to three environmental exposure variables (exposure to damp, distance from the sea, and orientation). The databases were established based on the diagnosis of the degradation condition of these claddings in-service conditions, in Portugal. The results reveal that the environmental exposure variables have a significant impact on maintenance requirements and costs. For all the categories of the environmental exposure condition variables, under all scenarios, ETICS is the least favorable constructive solution while CTS is the most advantageous solution. Furthermore, the results show that properly implemented maintenance activities enhance the performance level of building components, which positively affects their degradation behavior over time. Full article

In condition-based maintenance plans, the schedule of inspections is an important step. Condition-based actions are performed according to prescribed condition criteria (i.e., condition, cost, availability, among other factors), and the main purpose of inspections is to evaluate the façade’s condition and plan its correction in order to reduce the risk of failure of the cladding. Therefore, the main goal of this study is to implement multi-objective optimization to understand whether there is an optimal time interval for performing the inspections. For that purpose, a Petri-net condition maintenance model is used to assess the influence of different maintenance plans on the overall degradation of natural stone claddings. In this model, the maintenance activities can only be performed after an inspection has been carried out. The definition of the best maintenance policy results in a conflict of objectives. Owners/managers seek to achieve a maintenance strategy that minimizes service life costs and maintain the cladding in a safe and minimal degradation condition. Multi-objective optimization procedures are capable of considering several conflicting objectives. In this paper, the objective functions considered are minimization of the service life costs, maximization of the efficiency index, maximization of the service life, and minimization of the total number of replacements over the time horizon. Full article

This research results from the development of a global inspection system based on previous studies about individual expert inspection systems for 12 types of elements/materials of the envelopes of current buildings. The research focuses on the rational harmonisation of the causes of defects in a global classification list, established from 12 individual lists. The process considers predetermined criteria, including guidelines for merging, splitting and combining causes to reach a comprehensive and simple list. The frequency of the prescription of causes of defects is analysed and the causes “C-D12 Dampening of the cladding system” in painted façades and “C-B7 Use of unprescribed, inadequate, incompatible, low-quality, non-certified and/or non-approved materials” in natural stone claddings stand out. Additionally, when analysing the relationship of causes with defects, some causes are highlighted because they are considered direct causes of defects in a broad range of building elements/materials, namely: “C-C9 Accidental collisions with the cladding”, “C-C7 Intentional collisions/vandalism”, “C-D2 Excessive, insufficient or differentiated solar radiation”, “C-D8 Presence of rainwater or snow” and “C-D12 Dampening of the cladding system”. The proposed list of causes successfully gathers causal knowledge on the pathology of the non-structural building envelope in a single component, homogenising the vocabulary used for several building elements/materials. Full article

The Bargiolina quartzite from Monte Bracco (western Alps, northern Italy) represents one of the most important historical ornamental stones of the Piedmont region. Known and used since the prehistoric age as substituting material for chert, it was celebrated by Leonardo da Vinci, and exploited at least since the XIII century, peaking in the XX century. It was extensively used in the construction of basilicas and noble palaces by famous architects of Piedmontese Baroque, for internal and external stone cladding. There are four main commercial and chromatic varieties, and the main technical feature is the regular schistosity, to obtain very thin natural split slabs. The different varieties have a homogeneous mineralogical composition and microstructure: A fine and homeoblastic grain size, and a granular—lepidoblastic texture, with regularly spaced schistose domains. The main rock-forming minerals are quartz, phengite, small amounts of K-feldspar and traces of plagioclase and chlorite. The yield rate of quarries is about 20%, and the poor exploitation planning of the past led to only partly exploited quarry benches, with a very poor residual yield. The large amount of quartz-rich quarry waste and the presence of kaolin-rich gneisses suggests the potential for novel applications in the field of industrial minerals. Full article