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In recent years, in Europe, the use of wood-based products for structural solutions has increased, mainly because of the recent technological developments (e.g. development of products for high-rise buildings) and of the environmental benefits of wood-based products (e.g. carbon content of wood products). This study proposes a methodology based on life cycle assessment (LCA) approach to define a structurally equivalent functional unit for the comparison of the environmental impacts between wood-based solutions for building’s floors. The proposed methodology comprises five main steps: definition of the functional equivalence; definition of structural solutions; structural analysis; design of structural products; and calculation of the volume of structural products. This method was used to compare the environmental impacts from cradle-to-grave of structurally equivalent solutions for floors made of wood-based products with various strength and stiffness properties: solid wood (SW; softwoods and hardwoods); glued laminated timber (GLT); I-joists (IJ); and laminated veneer lumber (LVL). The results showed that, during the production stage, softwoods have the lowest environmental impact in the majority of the categories assessed. On the other hand, hardwoods (in particular D30) showed the best environmental performance during the entire life cycle. The discussion of results showed that the preliminary sizing rules have a high influence on the impacts of products with higher strength and stiffness properties. The results were compared per cubic meter and per structural solutions and showed that the products with higher strength and stiffness properties have a higher variation between the two results. The consideration of energy recovery at the end-of-life of products reduces the life-cycle environmental impacts of the structural solutions.

Environmental Product Declarations (EPDs) provide quantified information based on the Life Cycle Assessment (LCA) method, and other relevant information, related to the environmental aspects of products and services. The main advantage of EPDs is the possibility of comparison of the environmental performance of various products. The balanced comparison of the environmental performance of structural products requires that their structural performance is also taken into account. This study reviews 23 EPDs of solid wood (SW) and glued laminated timber (GLT) structural elements developed according to the EN 15804 product category rules. The NativeLCA methodology is applied in this study to review LCA procedures and technical data of EPDs, as well as to determine and compare the European Reference Values (ReVa) for the environmental impacts of SW and GLT products. Since the strength classes are not indicated in the documents, a methodology to estimate them and compare the environmental impacts of SW and GLT products was developed. The methodology proposed is applied to the selected EPDs to calculate and compare the ReVa of each estimated strength class. The environmental impacts’ comparison of various strength classes ReVas’ are also made considering a structurally equivalent functional unit. The methodology to obtain the SW’s strength classes from EPDs is based on the species of wood, country of origin and mean density, while for GLT strength classes are inferred from the type of GLT (homogenous or combined) and mean density. The calculation of ReVa for each SW and GL’s strength class allows the comparison of the environmental impacts of products with different structural performances. The majority of SW and GLT EPDs have been identified as C24 and GL24h strength classes, respectively. For the same structural equivalent functional unit, and for GWP, EP and PE-NRe environmental impact categories, the SW products presented lower environmental impacts than the GLT ones. An increase of GLT’s strength classes decreases PE-Re and PE-NRe and increases GWP environmental impacts for the functional unit considered.

Architectural concrete surfaces are a durable solution, but their deterioration process is unavoidable and begins as soon as the element is built. This study establishes a methodology for predicting the service life of architectural concrete surfaces, through the application of the factor method. For this purpose, 239 architectural concrete surfaces in in-service conditions are analysed. Different durability factors are studied and their impact in the service life of architectural concrete surfaces is evaluated. Different scenarios are analysed for the quantification of the durability factors. Scenario 4 presents the best results, leading to a higher similarity between the estimated service lives predicted by the factor method and obtained by the graphical method. The application of the factor method, as described in this study, allows one to predict the service life of architectural concrete surfaces. An estimated service life ranging between 43 and 48 years was obtained, which agrees with the literature and empirical knowledge.

Window frames are an important element of buildings, with an enormous impact on the thermal performance and interior comfort conditions of buildings. Knowledge regarding the service life of window frames is extremely relevant, aiding the adoption of adequate solutions in the design and maintenance stages. This study proposes a methodology for the service life prediction of window frames, based on the visual inspection of 182 case studies, in-use conditions, in which the degradation phenomena and various characteristics of window frames are surveyed. This information is converted into degradation curves, which express the evolution of the degradation of window frames over time, allowing their service life to be estimated, as well as the influence of their characteristics on their durability. For aluminum and wooden frameworks, estimated service lives of 37.6 and 27.3 years are obtained. These results reveal that the window exposure conditions and the users’ behaviors have a substantial impact on the degradation of window frames.

Gypsum is widely used in the construction sector in internal coatings. The fact that the chemical composition of gypsum does not change makes the material fully and eternally recyclable, potentially solving the important problem of the large amounts of gypsum waste that each year go to landfills. Up to now, most of the works that use gypsum wastes subjected the material to a previous heating process. This implies a significant energy consumption, reducing the environmental benefits of the recycling process. This paper shows the second part of a research on which two different types of gypsum waste were used as a substitute of commercial gypsum: gypsum waste from industrial plasterboard production and flue gas desulphurization gypsum from a thermal central plant. In this research, the influence of the heating process on the development of new gypsum plaster composites containing different types and contents of waste was studied. Their mechanical properties and thermal conductivity were determined and a brief environmental analysis, using the Life Cycle Assessment method, was carried out. Based on the findings of this paper, it is confirmed that it is possible to substitute 100% of commercial gypsum with gypsum waste from industrial plasterboard production without any heating treatment, but maintaining a good performance. With this action, apart from the benefits in terms of environmental impacts, a slight improvement in the density, mechanical properties and thermal conductivity of the plaster was obtained.

Research on the variability of the properties of recycled aggregate concrete is lacking and is necessary for the development of reliability analyses and code calibration procedures. This paper presents an experimental programme on the within-batch variability of the compressive strength, Young’s modulus, and splitting tensile strength of several recycled and natural aggregate concrete mixes. The influence of the recycled concrete aggregates on the mechanical properties and variability of concrete is analysed and discussed and benchmarks with standard predictions for the variability of natural aggregate concrete are made. It was found that full recycled aggregate concrete incorporation did not increase the variability of any of the properties tested, but intermediate ratios of recycled aggregate incorporation did. The properties of high-strength concrete mixes were more variable than that of all other mixes, irrespective of recycled aggregate incorporation. All properties of all compositions were suitably modelled by normal distributions. The coarse recycled aggregates were sourced from concrete waste.

During decades, the maintenance of buildings has been mainly reactive, based on subjective criteria, thus compromising the users’ safety and leading to a built park highly deteriorated. The effective planning of maintenance strategies requires the development of accurate tools to aid stakeholders’ decisions about when and how to intervene. This study analyses the utility of two computational tools to aid the adoption of condition-based maintenance policies, developed for the buildings’ envelope elements. The first tool is as an expert diagnosis and inspection system, which allows understanding how to intervene, based on the pathological characterization of the element analysed. The second tool provides information related with the element’s service life (when to intervene), according to their characteristics. However, before the definition of these tools, a question must be raised: “Do users need a buildings’ inspection, diagnosis and service life prediction software?” Therefore, this study performs a market survey involving 57 varied stakeholders working on the maintenance sector, evaluating the usefulness of the proposed computational tools, identifying the characteristics that the software must have to ensure its use by the sector.

Climate change is accelerating and can seriously affect the built environment, if not properly acknowledged in the design and maintenance stages. Despite the globally expected warming, climate changes will differ depending on region and climate type. What implications will temperature, precipitation and wind changes have on the degradation of the building envelope, in Southern Europe? How will the performance of façade claddings be affected by the end of the century? The purpose of this research is to determine the expected impact of climate change on the degradation of rendered façades, in a dry and hot summer temperate climate. This study is based on the complex relationship between climate parameters projections for Portugal and the known effects of environmental agents on the degradation of renderings. Projections indicate the increase of mean temperature and heat waves, reduction of precipitation and wet days, intensification of rainfall in shorter periods and decrease of wind speed in most of the country. Notwithstanding the projections’ inherent uncertainty, more cracking and fewer stains are expected. Due to the cracking increase, more loss of adhesion is probable. Further research is necessary to assess the risks of intense rainfall events to rendered façades, considering the also projected precipitation decrease.

The evaluation of the service life and maintainability of building’s envelope elements allows finding more sustainable solutions, ensuring the long-term durability of assets and reducing the costs associated with rehabilitation activities. The development of degradation models, without considering the impact of maintenance activities, is an extremely relevant step. In this study, a model to assess the degradation of External Thermal Insulation Composite Systems (ETICS) over time is defined, based on a Petri net modelling technique. A sample of 378 ETICS, located in Portugal, is evaluated through in-situ visual inspections. The uncertainty associated with the transition between the different degradation conditions is modelled by different probabilistic distributions. The validation of the model is based on probabilistic indicators of performance, computed through Monte Carlo simulation. The model proposed allows evaluating the probability of belonging to a given degradation condition and estimating the end of the service life of ETICS.

The density, colour and texture, plus mineral and chemical features of 18 ceramic-like CDW samples from the Abruzzo region (Central Italy) were characterised. The concretes, natural stones, tiles, roof-tiles, bricks and perforated bricks are either aphanitic to porphyric. Concretes and natural stones are grey to white and tend to be > 2.0 g/cm3; the masonries are brown to reddish and close to 40 wt%) and LOI (volatiles, CO2 + H2O). The masonries are instead calcite-, CaO- ( The petrography of CDW concretes is similar among geographical areas with abundance of limestones used as aggregates. However, in limestone-poor areas CDW are SiO2- and Al2O3-rich, reflecting the prevalent use of masonry and/or silicate-rich construction materials, implying that each geographical area is characterised by peculiar CDW composition. Therefore, the knowledge of mesoscopic, physical and petrographic aspects has to be known for planning adequate sorting methods, promoting upcycling reusing applications. Some of the studied CDW samples are susceptible to release relative high Cr and As content.

The valorization of waste material for building applications has a long and successful history. Nowadays, byproducts such as fly ash, ground-granulated blast furnace slag (GGBFS), and silica fume are usual constituents of cement and concrete. These supplementary cementitious materials (SCMs) are recognized for enhancing certain properties of concrete, while also reducing its environmental impact. The huge amount of cement consumed globally demands additional sources of SCMs. A number of waste materials are prospective candidates, and reports on almost any type of waste being used in cementitious materials can be found in the present literature. The comprehensive study of their capabilities should comprise their ecological, economic, and engineering benefits. This chapter focuses on the effect of alternative SCMs from wastes on the transport properties of concrete. Transport properties are important for durability and performance in the service life of concrete structures. The most usually assessed transport properties are water transport (permeability, sorptivity, and absorption), gas permeability (oxygen and air), carbonation, ion transport (chloride penetration and lixiviation), and electrical resistivity. Although they are connected, there are specific features to observe for each case. The effect of SCMs on transport properties mainly depends on the chemical and physical modifications that they cause in the microstructure. Some properties are more affected by chemical changes, whereas others are more affected by physical changes. The analysis of transport properties in cementitious materials with waste used as SCMs allows developing the most convenient cementitious systems containing them. Alternative sources of SCMs are numerous; therefore a comprehensive analysis of all of them is rather difficult. This chapter offers a review of a limited number of types of waste that have been tested as SCMs in cement, mortar, and concrete. Byproducts that are already extensively used in the market (e.g., fly ash,GGBFS, limestone powder, and silica fume) are not included in this review. The selected materials are not necessarily the ones that demonstrate the most convenient technical or commercial features but the ones with which the authors have more experience. Some of the comments in this chapter are certainly applicable to other types of SCMs, so the content may still be valuable for readers interested in other types of SCMs not included in this section.

Fiber-reinforced polymer (FRP) composites are being increasingly used in the construction sector, especially in corrosion-prone applications. However, there is still a lack of knowledge abo...

A recent quest for more sustainable cement-based construction materials has triggered the pursuit of technically viable alternatives of cement, making reactive magnesium oxide (MgO) one of the least known top contenders to reduce this sector’s environmental impact since it participates in the cement’s hydration reactions and presents enhanced carbon capture ability during its life cycle. In this study, two different commercially available reactive MgO samples were evaluated as partial cement replacements (at 10%, 15%, and 20%, by weight) in the production of mortars. Thermogravimetric analysis (TGA), energy-dispersive X-ray (EDX) analysis, differential thermal analysis (DTA), and powder X-ray diffraction (XRD) analysis of cement, MgO samples, and resulting mortars were carried out. All specimens were evaluated in terms of their mechanical and durability-related performance (i.e., flexural and compressive strength, carbonation, water absorption by capillary action, and shrinkage). The main results suggest that, in spite of the decreased, albeit acceptable, performance with increasing incorporation of MgO as partial cement replacement, a significant decrease was observed in the shrinkage strain of cementitious materials.

This paper presents a literature review concerning the performance from an environmental viewpoint of construction related products made with municipal solid waste incinerator bottom ash. It starts with an initial assessment of the bottom ash, and how it performs when used as aggregate substitute in cement-based products, as cement constituent and as raw feed in cement production. Evaluation of the material’s environmental performance when used as aggregate replacement in unbound and cement-bound base and subbase layers for road pavement construction, as well as in asphalt concrete layers, is also undertaken. This paper also appraises the behaviour of ceramic-based products, including glass, glass-ceramics, and general ceramics. As a result of the high quantities of potentially leachable contaminants inherent to the bottom ash, the environmental assessment carried out throughout this paper is mostly based on the materials’ leaching behaviour, but also based on life cycle assessments and gas emission analyses. The results of several leaching trials, conducted according to various specifications, were reviewed and paralleled with corresponding regulations, with the objective of establishing the products’ viability from an environmental point of view.

The evaluation of the performance, service life and maintainability of the buildings’ envelope is crucial to the accomplishment of more sustainable solutions. For that purpose, reliable methodologies should be defined to predict the service life of the buildings over time and according to their characteristics. In the last decades, several service life prediction methods have been established. This study intends to compare different service life prediction models applied to renderings, based on a multi-criteria decision analysis, in which two main criteria are analyzed: i) decision criteria, evaluating the features of each of the models proposed; and ii) the main goals of the stakeholders when applying a specific model, weighting the decision criteria according to their preferences. The analysis proposed comprises: the designer's perspective, who develops the model; and the user's point of view, who wants to use the model. In this study, a weighting and a sensitivity analysis of the criteria adopted are also proposed, providing stakeholder with information to select the most suitable model for a given use (e.g. a stakeholder without programming experience will tend to give more importance to the criterion “difficulty in learning the model”; whilst insurance companies may find stochastic models more adequate as they include uncertainty and risk). The results obtained in this study reveal that: simpler methods can be highly accurate but are only capable of analyzing the degradation phenomena in one dimension (relating the degradation condition of the rendered facades with their age); more complex models, are more demanding and more accurate, allowing encompassing the relevant variables for the explanation of the degradation of rendered facades; and stochastic models lead to the most relevant results, providing the risk of failure of the renderings according to their age and characteristics.

Steel corrosion is one of the biggest threats to the service life of reinforced concrete structures and chloride penetration favours the corrosion process. Due to sustainability and environmental issues, the use of recycled aggregate in concrete production has been growing. The aim of this study is to develop analytical models that allow predicting the performance of concrete incorporating recycled aggregates regarding chloride penetration. Multiple linear regression analysis was applied to a dataset collated from the literature. The dataset comprised 942 case studies from 33 publications. The analyses allowed identifying the explanatory variables and developing two mathematical models. One of these models is intended to predict the chloride diffusion coefficient from accelerated non-steady state migration tests, while the other predicts the charge transfer in rapid chloride permeability tests. The obtained correlation coefficients and analysis of variance (ANOVA) test results evidence the adequacy of both models. Thus, it is possible to estimate the resistance to chloride penetration in concrete incorporating recycled aggregates through the proposed models.

This paper presents a literature review concerning the fresh properties of concrete containing recycled aggregates from beneficiated construction and demolition wastes. It starts with the identification of the main variables affecting the workability of concrete, such as the quality and moisture state of the recycled aggregates. The effectiveness of water-reducing admixtures and of mineral additions on the fresh properties of recycled aggregate concrete is also analysed. A brief insight is given on the influence of using recycled aggregates on the main characterizing parameters of the material’s rheological behaviour. Other properties of recycled aggregate concrete in its fresh state are also discussed, including stability (i.e., bleeding and segregation), temperature of hydration, air content, and fresh density.

External renders are the first barrier against degradation agents and their performance affects directly that of building facades. During the life cycle of renders there is a progressive reduction of their performance until they are no longer able to fulfil their required functions, such as protection of walls and finishing of surfaces. The evaluation to understand how a render performs over time is a complex activity, not only due to the multiple factors concerning its exposition, but also to the difficulty in assessing the in-service behaviour. The use of in-situ techniques gives the possibility of obtaining the information about in-service performance of renders. This paper discusses the use of ultrasound and pendulum rebound hammer techniques for assessing the mechanical performance of rendered walls under natural ageing conditions. The results of ultrasound pulse velocity and rebound hammer index, in conventional and industrial renders, allowed identifying some of the main influencing factors, related both to the rendering-wall system (characteristics and degradation) and the inspection conditions and procedures. This study has confirmed the usefulness of these in-situ tests to evaluate the mechanical performance of rendered walls, despite their variability in natural ageing conditions.

The importance of knowing the service life of buildings and their components is recognized. Several studies have been developed, in different countries, to address this research topic. In some situations, the existing knowledge/information is easy to understand, but only offers absolute and standard values, which do not provide relevant information on the real service life of the elements. In real-world situations, the decision-makers usually face time-constraints in searching for service life data and apply service life values obtained from normative guidelines or a limited number of studies. This study thus fills an existing gap, identifying and synthesizing the relevant research on service life prediction of elements of the building envelope (exterior claddings in facades and pitched roofs, and window frames). A total of 107 publications are analysed and based on this systematic review, a database is created, highlighting the empirical evidence from the literature. A critical review is performed, to improve the awareness on the best experiences and practices, discussing the variance between the worst-case predictions and the real service life of the elements. This database can be used by researchers, end-users, or practitioners, aiding the creation of theoretical frameworks, to apply the extended past research in future projections and aid the management of the buildings and components’ life cycle.

In this paper, the mechanical behaviour of short rubberized concrete-filled steel tubular (RuCFST) columns with square cross-section under combined cyclic bending and (monotonic) compression is studied numerically. For this purpose, dynamic explicit analyses with kinetic energy control (for the quasi-static behavior to be obtained) using the commercial finite element modelling package ABAQUS were performed. Firstly, a brief introduction and literature review on the topic is made. Then, the numerical models are described in detail with emphasis on the modelling of the materials (natural aggregate concrete (NAC), rubberized concrete (RuC) and steel) under cyclic loading. An in-depth presentation of the numerical results is made afterwards. It includes firstly a verification of the models by comparison of the numerical results with their experimental counterparts, the latter previously obtained by the authors. Secondly, a numerical study on the effectiveness of RuC on the energy dissipation capacity of CFST columns under lateral cyclic loading is performed. It is concluded that the models yield similar results regarding stiffness, maximum loads, load–displacement curves and failure modes as those obtained experimentally, with RuC leading to a moderate reduction (of up to 2%) of the strength of the columns. Regarding the energy dissipation capacity of the columns, it is concluded that RuC generally leads to a reduction of this property (of circa 2.5% per each 5% of rubber aggregates replacement). The lower strength and stiffness of the RuC mixes designed for this study compared to NAC are found to generally offset the benefit of their lower brittleness in increasing the energy dissipation capacity of the columns.

In construction, there is a need to respond to environmental challenges and implement the Circular Economy as a strategy for the sustainable growth of the sector. To eliminate the lack of confidence in the application of the waste from this sector, it is necessary to carry out research in order to achieve an effective and integral management, as well as the reuse and recycling of these materials. In this work, a detailed study of Self-Compacting Concrete (SCC) was carried out, using as filler a waste from the drying process of the aggregate used in the manufacture of hot-mix asphalt. The results showed that it is possible to obtain a high-performance SCC in terms of durability by replacing a commercial siliceous filler (SF) with this dolomitic residual powder (RF), with high performance against the attack of aggressive agents (chloride, sulphate and carbonate ions) and shrinkage. In this study the analysis of the physical parameters of the materials (density, open porosity and pore size distribution as obtained from mercury intrusion porosimetry) and water absorption (by immersion and capillarity) was fundamental. The joint analysis of all the studied parameters allowed obtaining exhaustive results about the durability of the mixes and its interrelation with the properties of the constituents.

This work presents a comparative assessment of the sustainability, from a life cycle perspective, of a concrete filled square steel tubular (CFSST) column, using rubberized concrete (RuC), thus designated ‘RuCFSST’. RuCFSST columns are structural members that take advantage of the optimized structural performance of CFSST columns and of the improved ductility of RuC compared to that of natural aggregate concrete (NAC). Besides the two most obvious environmental advantages of using RuC instead of NAC in CFSST columns - reductions of tyre disposal into landfills and of extraction of natural aggregates - it is shown that a more complete assessment of the sustainability of RuC and RuCFSST columns is required. Hence, the embodied energy (EE), thermal performance, cost, expected durability and recycling potential of the RuCFSST column analyzed are assessed and compared with those of a CFSST column and a reinforced concrete (RC) column, all three having similar mechanical performance. It is shown that the analyzed RuCFSST column has a marginal higher EE and cost than those of the CFSST column - differences less than 1%. Conversely, the thermal transmittance coefficient of the former is lower than that of the latter, which improves its behaviour concerning thermal bridges. Compared to the composite solutions, the RC column possess circa 35% more EE but is about 25% less expensive. Overall, the RuCFSST and CFSST columns incorporate a similar total energy (includes the contribution of the EE and thermal performance during service life), which is 25% lower than that of the RC column.

This investigation intends to analyse the effects of the variation of different types of recycled concrete aggregates (RCA) on structural concrete. For this purpose, two source concrete (SC) mixes, one produced in the laboratory and another in a precasting plant, were considered. The experimental campaign included mechanical, durability and long-term tests: compressive strength in cubes; splitting tensile strength; modulus of elasticity; abrasion resistance; water absorption by immersion and by capillarity; resistance to carbonation; resistance to chloride ion penetration; shrinkage and creep. The recycled aggregate concrete (RAC) mixes were compared with a reference concrete (RC) produced solely with natural aggregates (NA). Concerning the replacement percentages for fine and coarse recycled concrete aggregates (FRCA/CRCA%), the following were considered: 25/25; 50/50; 100/0; 0/100 and 100/100%. The results show that it is possible to achieve similar performances using RCA from different SC but with similar compressive strengths. In fact, RAC mixes achieved results comparable to RC in several properties.

In this paper, a plane stress finite element model was developed to study the behaviour of a rubberized concrete (RuC) cubic specimen subjected to uniaxial compressive loading. To obtain the geometry of the given RuC section, specifically the heterogeneous distribution of rubber aggregates within the concrete matrix, MATLAB Image Processing is used. Then, to allow the initiation, opening and propagation of cracks in the concrete matrix upon loading, which ultimately lead to the failure of the RuC cube cross-section, a numerical model based on the eXtended Finite Element Method (XFEM) is implemented. The study motivation and the research significance are first presented. Then, the experimental programme conducted to characterize RuC’s main mechanical properties is described. Both the image-processing and the numerical analysis of the proposed mechanical model are described, with emphasis on the implementation and calibration of XFEM to allow for multiple cracks to develop in the RuC section. The numerical results are validated based on the experimental data and a detailed study on the post-cracked behaviour of the RuC section is presented and lastly, some conclusions are drawn.

This paper presents a literature review relating to the potential waste glass collection and processing as glass cullet for its use as raw material in secondary markets. Emphasis is given to the application of glass cullet in the construction industry, other than as construction aggregate, especially in ceramic-based products, including ceramic bricks, tiles and their glazing, glass-ceramics, foam glass-ceramics, and porcelain. These applications also include the use of glass cullet as a filtration medium, constituent in epoxy resins, in the production of glass fibres, elastomeric roof coatings, aesthetic finishing materials, abrasive material for surface cleaning, and paint filler. The analysis and evaluation of the vast amount of experimental research showed that glass cullet is a potentially valuable resource for the manufacture of ceramic-based products, where it can be used as substitute for expensive natural resources, improving the products’ physical, mechanical and environmental performance.

This paper presents a literature review on the incorporation of municipal solid waste incinerated bottom ash as raw material in several markets, other than those where it is conventionally used, such as geotechnical applications and road pavement construction. The main findings of an ample selection of experimental investigations on the use of the bottom ash as precursor of alkali-activated materials, as an adsorbent material for the removal of hazardous elements from wastewater and landfill gases, as soil replacement in agricultural activities, as partial or complete substitute of raw materials for the manufacture of ceramic-based products, as landfill cover and as biogas production enhancer, were gathered, collated and analysed.

The growth of the precast industry has led to the emergence of waste with enormous potential for recycling, given the strict quality control of these companies and the need of construction/demolition of structures with increasing strength capacities. In this investigation, an analysis of the mechanical behaviour of high-performance concrete (HPC) incorporating fine and coarse recycled aggregates (FRA and CRA) was made. The recycled aggregates (RA) originated from rejected precast elements with compressive strengths of 75 MPa and were used to replace natural aggregates (NA) in concrete mixes. The experimental campaign also included three families of concrete with proportions of densified silica fume (SF) of 0%, 5% and 10% (relative and in addition to cement). Each family comprised a reference concrete (RC) and three recycled aggregate concretes (RAC) with replacement ratios (FRA/CRA%) of 50/50, 0/100 and 100/100. The results obtained in the compressive strength, splitting tensile strength, modulus of elasticity, ultrasonic pulse velocity and bond strength tests showed that it is possible to produce high-performance concrete without NA. The silica fume led to a performance increase in the properties analysed with the creation of a new concrete mixing method that considered the specificities of RA and the difficulties of dispersing SF particles.

Most research on recycled aggregates concrete concern aggregates produced from concrete waste, rather than actual construction and demolition waste. Different investigations have assessed that sulfonated-based superplastizers are not as efficient in recycled aggregates concrete than on natural aggregates concrete, but no significant loss of polycarboxylic-based superplasticizer efficiency has been reported. This may not be valid when the aggregates are sourced from actual construction and demolition waste, due to the higher porosity, roughness, and weaker mechanical properties of aggregates produced from this source. This paper analyses the mechanical properties of superplasticized concrete with the incorporation of construction and demolition waste. Recycled aggregates produced from construction and demolition waste were taken directly from plants and used as aggregates without screening or treatment, emulating what would happen in a practical application by the concrete industry. The results of the tests and the superplasticizer’s efficiency are compared with results on natural aggregate concrete compositions and on analogue recycled concrete aggregate concrete compositions with and without superplasticizers. The composition of the different construction and demolition waste aggregates is considered during the analysis of results. Evidence was found that when recycled aggregates are sourced from construction and demolition waste, polycarboxylic-based superplasticizers perform satisfactorily but may not be as efficient as in natural aggregate concrete compositions.

This paper intends to evaluate the real influence of a commercial densified silica fume (SF) and of recycled concrete aggregates (RA) on the behaviour of high-performance concrete (HPC). For that purpose, three families of concrete with 0%, 5% and 10% silica fume (SF) of the binder’s mass were produced. In addition to the commercial silica fume, fly ash (FA) and superplasticizer (SP) were also incorporated in the concrete mixes. Each type of concrete comprises a reference concrete (RC) and three recycled aggregates concrete (RAC) mixes with replacement percentages (in volume) of fine natural aggregates (FNA) with fine recycled aggregates (FRA) and of coarse natural aggregates (CNA) with coarse recycled aggregates (CRA) of 50/50, 0/100 and 100/100, respectively. Considering the mechanical performance and durability of the concrete mixes, results show that it is possible to incorporate significant amounts of FRA and CRA. Regarding the silica fume, the densification process used in its manufacture seems to lead to the formation of agglomerates that change the real particle size of the SF, originating a loss of performance of the concrete made with them.

There is a growing awareness towards using materials with less social, economic and environmental impacts in the construction and rehabilitation of buildings. However, the evaluation of the sustainability of acoustic insulation materials in these three dimensions has not yet been presented in reference publications. This paper presents these results for the first time for materials used currently and alternative materials available in the construction market to control noise in buildings. An exhaustive review has been performed, focused on the most used insulation materials at the European level in construction and rehabilitation. The characterization at the level of embodied energy, acoustic behaviour and costs of these materials is presented, so that the most eco-efficient can be selected and applied. It is concluded that there are alternative materials that, from the acoustic behaviour, embodied energy and costs points of view, are perfectly viable to replace the currently used products.

The growing European interest on building sustainability has driven the establishment of the 2012/27/UE Directive. Mortars with thermal conductivity lower than 0.2 W/m·K (thermal mortars) can have an important role in the energy efficiency of buildings. The thermal conductivity is a fundamental parameter to characterize the hygrothermal performance of mortars. Nevertheless, its measurement is complex due to its large dependency on several factors and its dynamic behaviour. In the present paper, an experimental campaign is carried out to evaluate the influence of the moisture content on the thermal conductivity of 17 thermal mortars. Moreover, correlations between thermal conductivity analytically estimated from standards and experimentally measured are assessed. The results showed that the thermal conductivity is significantly dependent on the moisture content. However, most of the building standards use fixed conductivity values for normalized conditions. Therefore the discussion of relevant influence factors on thermal conductivity of thermal mortars can help designers and professionals to evaluate the hygrothermal performance of in-service buildings facades with thermal mortars, when subjected to real exposure conditions.

Currently, the scientific community has almost reached a consensus on the negative impacts of climate change. The causes of global warming are negative for sure, but are the impacts of these new climatic conditions negative and relevant? The answer is again probably yes, but not necessarily so. This study intends to evaluate the impacts of climate change on the functional deterioration of heritage buildings located in South Chile. For this purpose, an advanced artificial intelligence methodology, based on fuzzy logic, is used, and 79 heritage buildings, in five locations in South Chile, are analysed. The results obtained revealed that the predictions of climate change for this region, with an expected increase in temperature, associated with a reduction of the average annual precipitation, for the period 2045–2069, could actually benefit the functional performance of the heritage buildings analysed. Some lessons could be learned from the results, and the proposed model could be used for the prioritisation of maintenance activities, in heritage buildings, for the different locations analysed, considering the expected effect of climate changes, which in many other cases can be detrimental. © 2020 Elsevier Ltd

In this paper, the mechanical behaviour of short rubberized concrete filled steel tubular (RuCFST) columns with square cross-section under cyclic loading is studied numerically. For this purpose, quasi-static analyses using commercial the finite element modeling package Abaqus/Explicit are performed. Firstly, a brief introduction and literature review on concrete filled steel tubes and rubberized concrete (RuC) are made. Then, the numerical models are described in detail with emphasis on the modelling of standard and rubberized concrete and of the steel under cyclic loading. An in-depth presentation of the numerical results is made which firstly includes a validation of the models by comparison with experimental results previously obtained by the authors and secondly a study on the effect of using RuC on the maximum strength and ductility of the columns. Finally, the main conclusions of the work are put forward.

Indirect fastening is not yet a well-vetted method for attaching stone cladding from the point of view of designers and contractors, and a high incidence of failures has been observed in th...

The bias factor of the Eurocode 2 [CEN (European Committee for Standardization) (2008). Eurocode 2: Design of Concrete Structures–Part 1-1: General Rules and Rules for Buildings] and ACI 31...

Concrete carbonation is considered an important problem in both the Civil Engineering and Materials Science fields. Over time, the properties of concrete change because of the interaction between the material and the environment and, consequently, its durability is affected. Conventionally, concrete carbonation depth at a given time under steady-state conditions can reasonably be estimated using Fick's second law of diffusion. This study addresses the statistical modelling of the concrete carbonation phenomenon, using a large number of results (827 specimens or samples, i.e. 827 is the number of data concerning the measurement of the carbonation coefficient in concrete test specimens), collected in the literature. Artificial Neural Networks (ANNs) and Genetic Programming (GP) were the Soft Computing techniques used to predict the carbonation coefficient, as a function of a set of conditioning factors. These models allow the estimation of the carbonation coefficient and, accordingly, carbonation as a function of the variables considered statistically significant in explaining this phenomenon. The results obtained through Artificial Neural Networks and Genetic Programming were compared with those obtained through Multiple Linear Regression (MLR) (which has been previously used to model the carbonation coefficient of concrete). The results reveal that ANNs and GP models present a better performance when compared with MLR, being able to deal with the nonlinear influence of relative humidity on concrete carbonation, which was the main limitation of MLR in modelling the carbonation coefficient in previous study. ANNs are commonly seen as a black box; in this study, an attempt is made to address this issue through Knowledge Extraction (KE) from trained weights and biases. KE helps to understand the influence of each input on the output and the influences identified by the KE technique are in accordance with general knowledge.

This article reports on analytical research into water transport in concrete with 10%–25% ground recycled concrete (GRC) as partial Portland cement replacement and 0% or 50% mixed recycled aggregate (MRA). It included analyses of durability indicators associated with water transport: effective (or open) porosity, penetration depth of water under pressure, permeability coefficient, capillary water absorption and electrical resistivity. Shrinkage was also monitored in all concrete samples. The findings showed that replacing up to 25% OPC with GRC induced a linear rise in effective porosity of up 11.4% in concrete with 100% NA and 33% in mixes with 50% MRA, relative to conventional concrete. The outcome, a tightly interconnected pore structure, lowered electrical resistivity by 14% in NA and 23% in MRA GRC-additioned cement concrete. That pore structure was nonetheless sufficiently impermeable to ensure suitable concrete durability, with penetration depth of water under pressure below 30 mm, a permeability coefficient below 10−12 m/s and sorptivity below 1 mm/h0.5. The three-way ANOVA conducted revealed that adding GRC was the factor with the greatest impact on penetration depth of pressurised water, permeability coefficient and sorptivity. Curing time was the most statistically significant factor for electrical resistivity and shrinkage in both mix families (NA and GRC), inasmuch as it determined the degree of hydration of the anhydrous phase in GRC and in the residual mortar bound to MRA components. Further to the present findings, the use of GRC at a replacement ratio of up to 10% does not lower recycled material concrete's durability relative to the mixes made with ordinary Portland cement.

Considerable amounts of municipal solid waste incinerator bottom ashes are produced yearly without an adequate outlet. Given the established reactivity of the ash when subjected to an alkali medium, there is considerable scope to valorize it within the Construction industry in an alkali-activated material, thereby reducing the significant environmental pressure of the cement industry. This study assesses the optimization of alkali-activated mortars, using milled municipal solid waste incinerator bottom ash as a precursor, from mechanical and durability behaviour perspectives, many properties of which have never been analysed. The alkaline solution is comprised of either NaOH or Na2SiO3 (Na2O/precursor ratio varying between 9.1% and 24.2% and SiO2/Na2O ratios of 0 or 1.0); fly ash from a coal-fired power plant was also used as control precursor. X-ray fluorescence and powder X-ray diffraction analyses of cement, fly ash, bottom ash and of the resulting pastes were carried out. All specimens were evaluated in terms of their mechanical and durability-related performance (i.e. flexural and compressive strength, carbonation, water absorption by capillary action, and shrinkage). Considerable generation of H2 gas was observed during production, resulting from the reaction between the bottom ashes’ metallic aluminium fraction and the NaOH solution, leading to significant expansion and an overall increase in porosity and thus a strong decline in performance. Alkali-activated bottom ash specimens presented fast carbonation, resulting in a considerable strength increase. Despite the low performance of most of these mixes, the strength enhancement of specimens subjected to some conditions infers that there is significant scope for further mix design optimization (e.g. aluminium reduction, mixing time, Na2O/precursor and SiO2/Na2O ratios) that can lead to the manufacture of fit-for-industry construction materials.

Milled municipal solid waste incinerator bottom ash was used as a precursor in the production of alkali-activated mortars with recycled concrete aggregates as a sand substitute. Fly ash was used as control precursor and sodium hydroxide as an alkaline activator. Different thermal curing regimens were used: 24 h in ambient conditions; 24 h/70 °C; 48 h/70 °C; and 24 h/90 °C. Mechanical and durability-related performances were evaluated (i.e. flexural and compressive strength, modulus of elasticity, ultrasonic pulse velocity, carbonation, capillary water absorption, and shrinkage). The reaction between metallic aluminium from municipal solid waste incinerator bottom ash and OH− ions produced hydrogen gas, causing expansion, porosity increase and thus decline in performance. Low stability in high relative humidity settings due to leaching of highly soluble compounds was also observed. A further decline in performance was observed in mixes containing recycled aggregates. Alkali activated municipal solid waste incinerator bottom ash presented fast carbonation but also a considerable strength enhancement.

As a response to the great disparity in the recycled aggregates (RA) evaluated in most investigations and those sourced from recycling plants, this paper presents an overview on the subject and seeks to provide information on the present waste issue in the construction life cycle. Several factors related to the wider recognition and use of RA in construction are also described and analysed in this paper, including the main barriers to reuse and recycling, economic and environmental impacts, the choice of demolition methodology, the recycling procedure and certification of the final product. Increased governmental intervention, with ensuing strict legislation and comprehensive standardization, have been found to be key drivers for a greater pro-active engagement of construction and demolition related entities. Furthermore, with recent developments on the classification of RA, which can facilitate certification, it will become increasingly easy to increase the stakeholders confidence on the products' quality and resulting materials' predictable performance, consequently increasing demand for a technically feasible and potentially more economical substitute to their natural counterparts.

In the present world economic situation, the resources directed to the maintenance of buildings are very limited. Therefore, an increasing concern arises for the planning and prioritization of necessary maintenance works during buildings’ life cycle. The planning of maintenance action is achieved by predicting the moment when construction elements reach degradation levels that exceed acceptable standards. To be able to make such forecasts, crucial developments must be made regarding the methods to predict the serviceability of building materials and components. In this study, 444 facades located in the cities of Lisbon and Almada and the Algarve region (Portugal) are analysed based on in situ visual inspections. The approach proposed can be employed in various scopes of service life prediction and maintenance of constructions. This paper develops a priority hierarchy of maintenance actions for the claddings under analysis. The expertise acquired in buildings’ serviceability is very useful to support decision-making in the development of proactive maintenance strategies. The results reveal accurate outcomes in the correlation with the functionality and degradation parameters of facade claddings. The serviceability of the most common types of facades claddings (render, ceramic and paints) applied in Portugal is analysed. © 2017 Informa UK Limited, trading as Taylor & Francis Group.

The aim of this paper is to assess the feasibility of the use of a fine grain waste generated in hot-mix asphalt plants (HMA), namely recovery filler (RF), as filler materials in self-compacting concrete (SCC) production. A comparative study of two types of SCC was performed. The first concrete type was made incorporating recovery filler (SCC-RF) of a dolomitic nature and the second was made with commercial siliceous filler (SCC-SF), the latter used as reference. Good results of self-compatibility were obtained using RF. The thermogravimetric study showed that in SCC-SF the higher loss weight occurs in the dehydration zone (0–400 °C) and in SCC-RF it occurs in the decarbonation area (550–735 °C). The aging mechanism of both concrete types (SCC-SF and SCC-RF) was different. In the SCC-SF mixes, portlandite undergoes carbonation processes and pozzolanic reactions and in the SCC-RF mixes it only undergoes carbonation processes. The experimental results (splitting tensile strength, flexural strength and static modulus of elasticity) show the validity of using EHE-08, initially proposed for NVC (Normally Vibrated Concrete), in SCC. The ultrasonic pulse velocity values for SCC-SF was greater than for SCC-RF, which can be attributed to compacity and compressive strength. The shrinkage behaviour was better in SCC-RF than SCC-SF, mainly due to the greater particle size of recovery filler (RF), although the SCC-RF mixes showed lower density and mechanical strength than SCC-SF. In short, the SCC manufactured with recovery filler from plants manufacturing hot-mix asphalt (HMA) – SCC-RF – is expected to have better features than SCC-SF in relation to shrinkage and early appearance of cracks.

This research intends to determine an equivalent functional unit in concrete with recycled aggregates (RA) to conventional structural concrete in the context of Life-Cycle Assessment (LCA) analyses. The work intends to contribute to a better understanding and greater confidence in the use of concrete products with RA. The relationship between recycled aggregates concrete (RAC) and conventional concrete (RC) is expressed by fundamental parameters α , which describe the relevant equivalent properties of RAC in function of the same property of RC. Using those parameters, the study performs a thorough analysis according to Eurocode 2 (EC2): the various compliance checks with the limit states are performed in order to obtain the amount of recycled aggregates concrete required to reach the same performance as a given volume of conventional structural concrete. Conversion criteria for concrete structures with RA (concerning its structural performance) are established and the conversion formulas are tested in case studies. This study is developed particularly for slabs and beams, but remarks are made concerning other main structural elements, namely columns and footings. The results show that the method is valid for slabs and beams and that the conversion formulas yield good results.