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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...

This paper presents a complete and updated literature review on the properties of self-compacting concrete with fine and coarse recycled aggregates. The subject of self-compacting concrete with recycled aggregates (RASCC) is greatly relevant to Society, since there is an increasing demand from the construction industry to adopt new processes to minimize its negative impacts on the environment. The use of recycled aggregates in concrete production presents a great environmental benefit through savings from the extraction of natural aggregates and the reduction of dumped material. The advantages associated to the use of both concrete with recycled aggregates and self-compacting concrete have boosted an increase in research and a consequent publication of literature in the last few years. Combining these two themes has allowed allying the environmental and economic advantages of each of the materials, leading to an innovative material of great interest to the construction industry in general. Even though RASCC is a relatively recent scientific area, studies on this material have demonstrated its viability, to produce both traditional and non-complex structural elements and highly complex and densely reinforced elements, which hinder the vibration procedures and may influence the final quality.

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.

This paper presents a numerical investigation on the ductility and strength of short steel tubes filled with Rubberized Concrete (RuC), which is a composite material that mixes concrete with rubber particles. This research concerns the enhancement of both ductility and energy absorption of CFST by considering a core of RuC instead of normal concrete (NC). First, a brief literature review on the topic is presented. Then, based on an experimental programme conducted by the authors, numerical models of CFST and RuCFST columns are developed. The results of non-linear analyses (ultimate strengths, load-shortening curves and failure modes) are validated using experimental data, and good agreement is shown. Finally, a numerical study on the properties of confined NC and RuC is conducted. It is concluded that the concrete damaged plasticity model can be used to simulate RuC. The dilation angle plays a key role in RuC and its lower value (compared to that of NC) influences the concrete confinement. Taking into account the RuC dilation angle, steel yield stress and tube local slenderness, a new formula is proposed to predict the concrete core confinement of the studied CFST and RuCFST columns with circular sections.

Sustainability is a pressing concern of the 21st century. Social development in most countries is raising awareness of the needs of future generations and legislation to protect the present and future quality of life. These needs are compelling various sectors, including construction, to find sustainable solutions. This paper investigates the feasibility of incorporating high-quality recycled concrete aggregates in new concrete, providing a recycling option for precast rejects. The massification of recycled aggregate incorporation would decrease the environmental impacts of the concrete industry, for instance due to reduced landfill disposals, less quarry mining and shortened transport distances. The study presented in this paper concerns the material, mechanical, durability and short-term structural behaviour of concrete specimens and structures made with recycled aggregates sourced from high-quality concrete elements. This paper intends to provide a holistic view of the study, from the procurement and crushing process that generated the aggregates to the conclusions of the different experiments performed. The results of this experimental campaign are benchmarked with other investigations and the importance of the quality of the RA is evaluated. This paper concerns the first full-scale experiments made on recycled aggregates concrete structures. Also, some of the tests performed were the first of their type made on recycled aggregates concrete.

The water vapour permeability of renders is related with the greater or lesser drying ability of this coating mortar system. Easy drying of an applied render allows a better water resistance and consequently its greater durability versus the physical degradation mechanisms in real in-service conditions. Presently this standard characteristic is not measured on site, and neither are there consensual in situ methods that allow an indirect relationship with this property. This paper presents two experimental programs, in laboratory and in situ, which studied various drying parameters (drying rate and drying resistance index) and the corresponding relationships with hardened physical characteristics (water vapour permeability, open porosity and bulk density) relevant to characterize the in-service performance of mortars. Based on the experimental results, it is concluded that the drying resistance index (D i ) is a good indirect measure of the in-service water vapour permeability of renders applied on building facades.

Even though in several countries there are regulations allowing, even at a small scale, the use of recycled aggregates in concrete production, practice shows that the cases in which this solution is implemented are still rare. However, in most of these countries the use of the fine Fraction of the Recycled Aggregates (FRA) from general Construction and Demolition Waste (CDW) is restricted or even banned. More recent studies have shown that the use of FRA is feasible and that the resulting mechanical performance is perfectly acceptable. This paper presents the flexural tests performed on reinforced concrete beams made with replacement of natural by recycled fine aggregates, comparing the results obtained in terms of ultimate load and deformation, ductility, bearing capacity and cracking with those from a reference beam, made with conventional concrete.

Ultrasound has been widely used for the diagnostic testing of structural elements, but little research has been done and no specific standard exists for its application to nonstructural materials such as mortars. These mortar coatings are usually applied on walls with more than one layer; therefore, the ultrasound technique needs more investigation to better understand the results for rendered walls and in-service conditions. This study discusses the use of this technique, using the indirect method, in assessing the performance of cement-based mortars. Experimental work was carried out in the laboratory and in situ for this purpose. It was possible to relate the pulse velocity to the mechanical properties of the mortars, proposing criteria to support the in-service performance. It was also possible to characterize the presence and severity of various anomalies, mainly discontinuities. Finally, when this technique was combined with others (on rendered walls or on extracted samples), the in-service diagnostic testing under real in-service conditions was less susceptible to subjectivity. The results showed that this technique has a great potential to characterize the in-service performance of renders and to help the diagnosis of degradation. The specific factors influencing this technique for renders should be emphasized and separated from applications in concrete.

Whilst systems have been developed for bridge management, when it comes to buildings a much larger variety of maintenance problems and a small number of buildings per owner means that building management systems are still quite rare. Indeed, efficient approaches to the management of building maintenance still need to be developed. This study addresses the application of a recently developed Building Management System (BdMS) – BuildingsLife . This software uses a genetic algorithm applied to Markov Chains to estimate the best maintenance plan. This simulation compares different maintenance plans actions. Each one considers different material properties in a building facade and consequently the building's performance varies during its service life. The varying durability is given by the transition probability of the Markov Chain method. This method proved to be very accurate in the description of the uncertainty of degradation laws, leading to good results in the service life estimation of the facades analysed. The best maintenance plan can be characterized as the plan offering the lowest global cost over a certain analysis period which allows an acceptable degradation level, as established by the building manager. The genetic algorithm was used to generate multiple combinations of adequately-performing maintenance actions in order to obtain the best result. The application of the proposed method is demonstrated with a case study, leading to coherent results.

While onsite measurement of air permeability provides a useful approach to assess the service life of concrete structures, the combined use of onsite and laboratory measurement of air permeability is useful to anticipate whether the target service life is to be achieved. This investigation was developed within the aim of founding the application of an air permeability test (Torrent method), based on the experimental observation of specimen geometry and surface influence on air permeability results. An experimental program was developed considering three specimen geometries, two types of surface, and twelve concrete mixes. The results were analysed and no significant influence of the tested specimens geometry and surfaces was detected. Therefore, the use of any of the surfaces or specimens geometry in mix approval or in compliance control processes is possible without correction of the results. This work constitutes a contribution to further understanding of the test method in particular and of concrete air permeability assessment in general.

The main goal of this study was to characterize, using the slant shear test, the bond strength of the interface between recycled aggregates concrete (RAC) and natural aggregates concrete (NAC). This can be relevant in the case of new construction, if precast NAC members with cast-in-place RAC parts are adopted, as well as in the case of rehabilitation of existing NAC structures if strengthened using an RAC overlay. Four replacement rates of natural coarse aggregates by recycled coarse aggregates obtained from concrete blocks, 0% (NAC, to serve as reference), 20%, 50% and 100%, were considered. The following substrate roughness conditions were produced: smooth interface – cast against wood formwork (CAW) without any further treatment; slightly rough interface – produced with a steel brush (SB); and rough surface – treated with a needle gun (NG). A total of 12 tests were performed regarding the four replacement rates and the three substrate roughness conditions. The assessment of the roughness parameters was performed using the 2D-LRA method. It was concluded that RAC exhibits adequate mechanical properties for structural use, although declining with the increase of the replacement rate. Regarding roughness, results corroborated previous studies, since an increase of strength for rougher substrates was observed. Finally, it is found that the values obtained by the codes are very conservative for all types of tested concrete, including for RAC100 despite their low concrete strengths.

An experimental investigation on the strength and ductility of short steel tubes filled with rubberised concrete (RuC), sourced from recycled scrap tyres, is presented in this paper. Firstly, a brief literature review on (i) concrete-filled steel tubes (CFST) and (ii) mechanical characterisation of rubberised concrete is presented. Then, the experimental investigation is described and test results are shown and discussed, namely, the assessment of (i) RuC and steel mechanical properties and (ii) RuCFST column structural properties. The influence of various parameters, such as the cross-section shape (square, rectangular, circular), steel grade, and concrete mix (standard concrete versus RuC), on the short column strength and ductility is analysed and discussed. Eurocode 4 is considered (i) to determine the strength of the tested columns and, in particular, (ii) to assess its applicability to RuCFST columns based on a comparison with the experimental results. The main conclusion of this research is that RuCFST short columns present higher ductility than those made of standard concrete, even though they also show lower strength. This improved ductility is noticeable in columns with circular sections, rather than in square and rectangular sections. From a practical viewpoint, this could be a major benefit for structures in seismic areas where energy dissipation is needed.

Due to their outstanding mechanical, thermal, and durability properties, polymer matrix nanocomposites (PMCs) are currently a prominent area of research. The opportunity of applying PMCs in structural reinforcement and rehabilitation of damaged infrastructures, as well as working as a new structural material, justifies the increasing number of recent studies. In this review article, the effect of adding different reinforcements at nano-scale, such as carbon nanotubes, nanoclay, graphene, or nanosilica to polymer matrices, is discussed and the improvement in mechanical properties of PMCs is evaluated. Some concluding remarks and new perspectives on the use of PMCs in structures are given.

This paper's aim is to characterize the freeze–thaw resistance of normal strength and high-strength concrete with partial or total replacement of fine natural aggregate (FNA) by fine recycled concrete aggregate (FRCA). The surface scaling, mass loss, length change, residual ultrasound pulse velocity and residual compressive strength were monitored for different FRCA replacement ratios (0%, 20%, 50% and 100%) subjected to 300 freeze–thaw cycles according to ASTM C666 – Proc. A. In general, the mechanical strength decreases with the incorporation of FRCA, especially in high-strength concrete. Contrary to high-strength concrete, normal strength concrete was not frost resistant, regardless the type of aggregate used. The w/c ratio had a greater influence on the freeze–thaw resistance than the type of aggregate. The air entraining had a slightly beneficial effect on high-strength concrete. Generally, it is concluded that the incorporation of FRCA is not detrimental to the freeze–thaw resistance of concrete. Only the total replacement of FNA by FRCA led to lower residual mechanical strengths after freeze–thaw action than those obtained in reference mixes. However, surface scaling tends to be more severe in concrete with FRCA if it can be saturated near the concrete surface.

The environmental impact reduction has a growing prominence in building constructions. One of the solutions to that is external wall coating mortars with improved thermal performance, which can be produced with incorporation of lightweight aggregates. To obtain a mortar with the demanded hardened characteristics (physical and mechanical), their fresh properties must be acceptable. This study is focused on the fresh state properties of mortars with improved thermal performance. The mixes were produced with incorporation of different lightweight aggregates (expanded clay, expanded cork granules), a main binder (cement), supplementary materials as partial replacement of cement (fly ash, air lime) and admixtures (air entraining agent, water retaining agent). In this paper, the selected mortars with acceptable workability were tested for fresh density, flow, air content, and water retention. Lastly, the relationship between the fresh and hardened properties (obtained from a previous study) was assessed to highlight the importance of fresh properties. In conclusion, the mortars’ fresh behaviour was mainly influenced by the incorporation of different lightweight aggregates and admixtures. In addition, an optimization was carried out to select the most adequate thermal mortars for the external wall coatings from two perspectives, namely the overall performance (fresh properties, compressive strength, capillary water absorption, thermal conductivity) and the individual thermal performance.

Nowadays, the degradation of the built environment is becoming a serious economic, cultural and environmental problem in several developed countries, after several decades of adopting an attitude of “built and let decay”. The lack of maintenance policies led to additional costs and risks for owners and increased the aesthetic degradation of our cities. In this study, a condition-based maintenance model, based on Petri nets, is used to analyse the influence of alternative maintenance strategies on the overall degradation of natural stone claddings. For this purpose, three maintenance strategies are considered: i) total replacement; ii) combination of minor intervention and total replacement; and iii) combination of cleaning operations, minor intervention and total replacement. The impact of the alternative maintenance strategies on the future performance and remaining service life of natural stone claddings is discussed. In this study, a sample of 203 natural stone claddings, located in Portugal, is analysed and the degradation of these claddings in-service condition is evaluated through in-situ inspections. Furthermore, a simplified multi-criteria analysis is carried out to evaluate the economic impact of each maintenance strategy in comparison with the increased durability achieved through its adoption. The results reveal that the adoption of other maintenance activities (minor interventions or cleaning operations) increases the operational costs, as expected, but promotes the durability of the claddings. The adoption of maintenance actions allows increasing the predicted service life of NSC (148 years for MS2 and 177 years for MS3), when compared with NSC that are not subjected to any kind of preventive maintenance (70 years).

Usually, maintenance models consider maintenance actions as perfect, i.e. these interventions can restore the components to the “as good as new” state. However, in many situations, this assumption is too simplistic, and moreover it is not true. In this study, imperfect maintenance actions are considered. For that purpose, a new methodology is developed to quantify the impact of maintenance actions on buildings' envelope components. This methodology is based on a probabilistic approach, implemented through a stochastic maintenance model based on Petri Nets (PN). The quantification of the impact of maintenance actions on building components is estimated by assessing the impact of these actions on the overall degradation condition of the component, which is expressed by a numerical index called severity of degradation index, Sw. This is a conceptual study, in which the maintenance plans are composed of condition-based maintenance actions, and the schedule of the actions is carried out based on the condition of the components. In the definition of the maintenance plans, four levels of interventions were considered: inspections; cleaning operations; minor interventions; and total replacement. The results reveal that the adoption of minor interventions or cleaning operations increases the operational costs but, when performed with an adequate periodicity, allows maintaining the components’ performance at high standards for most of their service life, thus promoting their durability.

This article analyses the combined effect of valorising ground recycled concrete (GRC) as 10% or 25% cement replacement and 0% or 50% mixed recycled construction and demolition waste aggregate (RA-CDW) in structural concrete. An exhaustive experimental programme was designed to assess the variation in compressive and tensile strength, modulus of elasticity and hardened concrete density. Non-destructive ultrasonic pulse velocity and electrical resistivity tests were also conducted. The concrete mixes prepared with GRC and RA-CDW exhibited lower mechanical performance than those manufactured with natural aggregate and cement only (although the difference was smaller than the respective replacement ratios). These findings were attributed to: a higher water/binder (cement + GRC) ratio, the dilution effect resulting from a lower cement content in the new mixes and the intrinsic properties (water absorption and abrasion resistance) of the new recycled components. The mixes with 10% GRC and 50% RA-CDW, however, showed similar mechanical performance and remained in the same strength class as those with 50% RA-CDW and 100% Portland cement. In terms of the electrical resistivity and ultrasonic pulse velocity tests, the effect of replacing OPC with GRC was below 14%, irrespective of whether natural or recycled aggregates were used. Such promising findings pave the way for more efficient and global C&DW management with a view to steering the construction industry toward the circular economy.

In the past few decades, the construction industry has been increasingly using fibre reinforced polymer (FRP) materials, due to their advantages in comparison with traditional materials, especially in aggressive environments. However, the information regarding the long-term behaviour of FRP constructions under real service conditions is limited and scattered. In this paper, a system for the inspection, diagnosis and rehabilitation of FRP constructions is presented and validated, providing a standardized and systematic tool for the maintenance of these constructions during their service life. A classification system for the anomalies and most probable causes is first presented. To assist the diagnosis of the anomalies, several in situ non-destructive methods are included in the system, as well as various rehabilitation techniques, able to maintain and/or restore the functionality of FRP elements. Several correlation matrices are proposed, interrelating different anomalies, and relating them with probable causes, and diagnosis and rehabilitation techniques. The system is validated and calibrated through an extensive field campaign of inspections of 410 substructures in 31 facilities. Although developed for FRP profiles and moulded gratings of all-FRP constructions, the system can also be used to inspect FRP components of sandwich or hybrid structures. The implementation of this system supports the inspection activities of a proactive maintenance strategy and, at the same time, the standardization of inspections, resulting in an increase of the effectiveness and objectivity of the actions to be taken upon the occurrence of anomalies in FRP constructions.

Knowing the aggregates' properties is fundamental for the correct design and performance prediction of concrete. The incorporation of coarse recycled aggregate (CRA) in concrete requires a deep understanding of CRA's capacity and limitations. CRA properties are mainly conditioned by the type of natural aggregates (NA), the interstitial transition zone (ITZ), and the adhered mortar's quality. All these conditions are restricted by the chemical, physical, and mechanical properties of the source concrete (SC). The potential alkali reactivity of CRA raises the alkali-silica reaction (ASR) issue when CRA incorporation in concrete is an option. The heterogeneity of CRA affects the reactive silica and alkali content present in NA and in the adhered mortar, respectively, depending on the characteristics of the SC. This makes it difficult to analyse the influence of CRA's heterogeneity when ASR-effected SC is used. This work intends to investigate modifications of CRA properties due to ASR level in the SC. For this purpose, several tests including ASR evaluation, particle size distribution, density and bulk density, water absorption, shape index, flatness index and fragmentation resistance were performed on NA (fine and coarse) and CRA under natural and accelerated aging conditions. The results shown that the use of ASR-effected CRA does not change its mechanical and physical properties. In fact, these properties are more dependent on the corresponding characteristics of NA, ITZ, and the adhered mortar than on the ASR level in the SC.

This paper presents the data collected from the inspection of 105 Portuguese flat roofs. The inspections were based on a system of inspection, diagnosis, and rehabilitation created and vali...

The construction sector consumes 95% of the total production of gypsum due to its multiple applications. Gypsum plaster is one of the most common indoor coating material (pastes and mortars), but it can also be used in prefabricated products like plasterboards, blocks and decorative elements. Gypsum waste recycling provides a solution to an important environmental problem from the use of gypsum plaster, which is the generation of large amounts of wastes at different phases (production, construction, rehabilitation and demolition). This paper studies two different replacement alternatives of natural gypsum: Flue Gas Desulphurization (FGD) gypsum and gypsum waste obtained from industrial plasterboard production. The influence of the previous types, amounts of waste (25, 50, 75 and 100 wt%) and different heating temperatures (100 °C, 150 °C and 180 °C) and processes on the workability of gypsum plasters is evaluated and discussed, based on a microstructure analysis using XRD and SEM techniques. This research highlights the feasibility, in terms of workability, of using Gypsum Plasterboard Waste (GPW), without any heating process, as a replacement gypsum in plasters. Despite the fact that a higher amount of water was necessary in the production of the mixes, a good workability was achieved. On the other hand, the unfeasibility of using unheated FGD as a constituent of plasters was demonstrated. However, a good performance, in terms of workability, of the FGD was obtained when the powder was subjected to a heating process at 180 °C during 6 h.

Society is becoming aware of the environment and progressively using more recycled aggregates to produce recycled structural aggregate concrete. In addition, many researches have analysed the properties of hardened recycled aggregate concrete, but few of them have focused on the mixing method and the consequences that it has on the properties of concrete. In this research, recycled aggregate concrete using dry, with extra water supply, and saturated recycled aggregate has been prepared. The different mixing conditions induce differences the micro and macroporosity of concrete that have been evaluated by computerized axial tomography, scanning electron microscopy and a new developed methodology, based on digital image analysis, developed to analyse the distribution and size of macroporosity. The software has been implemented in Matlab© and is available to the readers of the journal for downloading and use. The results show that the dry and saturated recycled aggregate lead to very different concrete properties. On the one hand, the use of dry aggregate causes a local reduction of the w/c ratio, increasing heterogeneity and decreasing workability. On the other hand, the saturated aggregate incorporates extra water by adsorption that causes an increase in the water/cement ratio, thus increasing the porosity volume and size of the new mortar of the recycled aggregate concrete.

The construction sector is a major contributor to global environmental impacts. This is one of the reasons why there is a political trend towards a ?greener? sector. One indicator of this trend is the progressive application of life cycle thinking approaches and life cycle assessment of products, assemblies and buildings. The digitalization of construction projects, namely the use Building Information Modelling (BIM), can constitute a support to the automation of the application of Life Cycle Assessment (LCA) at the building?s design stage. However, besides the complexity of LCA model and results interpretation, BIM models usually lack LCA data that allow environmental impacts calculation. Currently, few publications explicitly relate the integration of LCA and BIM with the specificities of distinct development stages in the design and construction process or Levels of Development (LOD) of BIM objects. This paper summarizes the possible sources of LCA information to include in BIM models and discusses the complexity of LCA information needed for distinct BIM objects? LOD. A parametrization of environmental information is proposed, to be included in BIM objects, based on an evolutionary level of detail in LCA information for increasing LODs., This work was supported by FCT - Fundação para a Ciência e Tecnologia [grant number PD/BD/127850/2016] under the Doctoral Program EcoCoRe - Eco-Construction and Rehabilitation. Support from CERIS and Instituto Superior Técnico is also acknowledged., info:eu-repo/semantics/publishedVersion

This paper presents a classification system for the inspection, diagnosis, and rehabilitation of vinyl and linoleum floorings in healthcare infrastructures. First, the identification of the...

The need to reduce the world’s ecological footprint has encouraged the construction sector to look for more innovative solutions to reuse its waste production. Since concrete waste is one o...

This study intends to analyse the effects of the incorporation of recycled aggregates (RA) and densified silica fume (SF) on the durability of high performance concrete (HPC). Considering that the mortar adhered to the RA strongly influences the behaviour of the concrete made with it, the source of these aggregates was restricted to precast mixes with target compressive strengths of 75 MPa and subjected to a primary plus a secondary crushing process. With regard to SF, a certified commercial product was used, which was incorporated in the concrete as an additional material to cement. The experimental campaign included the production of 12 types of concrete, which were evaluated by means of water absorption by immersion, water absorption by capillarity, resistance to carbonation, resistance to chloride penetration and permeability to oxygen tests. The results show that it is possible to produce HPC with significant quantities of fine and coarse recycled aggregates (FRA and CRA) as replacement of traditional fine and coarse natural aggregates (FNA and CNA). Ultimately, considering the properties analysed, it seems possible to produce HPC without incorporating natural aggregates (NA). The incorporation of densified silica fume contributed to an increase of concrete's performance through the use of a mixing process developed by the authors that minimized the previously endured dispersion difficulties associated with this product.

A stochastic Petri-net formalism is proposed to predict the degradation of ceramic claddings over time in order to understand how different environmental exposure conditions contribute to the overall degradation of these claddings. For that purpose, the degradation condition of 195 ceramic claddings located in Lisbon, Portugal, is evaluated through in situ visual inspections. In the first part of the study, a stochastic deterioration Petri-net model is proposed for the entire sample. In the second part, the original sample is divided according to the environmental exposure conditions, evaluating the influence of these conditions on the deterioration process of ceramic claddings. Four main degradation agents are analyzed: exposure to moisture; distance from the sea; orientation; and wind–rain action. The results reveal that Petri nets can accurately describe the deterioration process of ceramic claddings, providing relevant information regarding the performance of these claddings through their life cycle and according to the environmental exposure conditions to which they are subject. These results are extremely relevant for different practitioners: the approach allows the adoption of more sustainable and durable solutions at the design stage, as well as improving the durability of the ceramic claddings by performing optimized maintenance plans and strategies.

The construction field has contributed to environmental degradation, producing a high amount of construction and demolition waste (C&D waste) and consuming large volumes of natural resources. In this context, recycled concrete (RC) has been recognised as a means to preserve natural resources and reduce space for waste storage. During the last decades, many researchers have developed works studying different recycled concrete properties. This review focuses on structural RC made with coarse recycled aggregate from concrete waste. The main objective is to provide a state of the art report on RC’s properties and an analysis on how to predict them taking into account relevant research works. Moreover, the study tries to collect and update RC findings, proposing equations to define RC’s performance, in terms of mechanical strength, modulus of elasticity, stress-strain, creep and shrinkage. El campo de la construcción ha contribuido a la degradación del medio ambiente, produciendo gran cantidad de residuos de construcción y demolición y consumiendo grandes volúmenes de recursos naturales. En este contexto, el hormigón reciclado se ha presentado como una opción para preservar los recursos naturales y reducir el espacio destinado a vertedero. Así, durante las últimas décadas, muchos investigadores han desarrollado trabajos para estudiar las propiedades del hormigón reciclado. Este artículo se centra en el hormigón estructural fabricado con árido reciclado grueso procedente de residuos de hormigón. El principal objetivo es desarrollar un estado del arte que recoja las principales propiedades del hormigón reciclado y un análisis de cómo calcularlas teniendo en cuenta un gran número de trabajos relevantes en este ámbito. Adicionalmente, el estudio recopila y actualiza el conocimiento sobre estos hormigones, proponiendo ecuaciones que permitan definir sus resistencias mecánicas, módulo de elasticidad, tensión-deformación, fluencia y retracción.

In this study, a methodology to model and predict the life-cycle performance of building facades based on Stochastic Petri Nets is proposed. The proposed model evaluates the performance of rendered facades over time, evaluating the uncertainty of the future performance of these coatings. The performance of rendered facades is evaluated based on a discrete qualitative scale composed of five condition levels, established according to the physical and visual degradation of these elements. In this study, the deterioration is modelled considering that the transition times between these condition states can be modelled as a random variable with different distributions. For that purpose, a Stochastic Petri Nets model is used, as a formal framework to describe this problem. The model's validation is based on probabilistic indicators of performance, computed using Monte-Carlo simulation and the probability distribution parameters leading to better fit are defined as those maximizing the likelihood, computed using Genetic Algorithm. In this study, a sample of 99 rendered facades, located in Portugal, is analysed, and the degradation condition of each case study is evaluated through in-situ visual inspections. The model proposed allows evaluating: i) the transition rate between degradation conditions; ii) the probability of belonging to a given degradation condition over time; and iii) the mean time of permanence in each degradation condition. The use of Petri Nets shows to be more accurate than a more traditional approach based on Markov Chains, but also allows developing future research to consider different environmental conditions, maintenance actions or inspections, amongst other aspects of life-cycle analysis of existing assets.

The shrinkage and durability properties of a total of 34 concrete mixes with recycled aggregates produced from different untreated construction and demolition waste (CDW) were tested. The effect of a polycarboxylic superplasticizer on the enhancement of these properties is presented, discussed, and compared with the findings of studies on concrete whose recycled aggregates are sourced from concrete. All properties were significantly affected by recycled aggregate incorporation and this effect was strongly dependent on the properties of the recycled aggregates of each specific source. The superplasticizer was less efficient in mixes with CDW than when the recycled aggregates were produced from concrete, the most common source of recycled aggregates in experimental works, despite untreated CDW being more practical and desirable from an industrial and environmental perspective.

This paper presents a novel technique used to analyse the volume of adhered mortar to the recycled aggregate. A computerized microtomograph (?CT) device was used to evaluate the volume of the aggregate, the volume of natural aggregate and the volume of adhered mortar. To this end, a natural aggregate has been characterized, using the ?CT, with which a source concrete has been produced. Subsequently, the source concrete has been crushed to obtain a first cycle recycled aggregate. After the characterization of the first-generation of recycled aggregate, a new source concrete has been made with it to be subsequently crushed again obtaining a second-generation recycled aggregates. In the same way a third-generation recycled aggregate has been obtained and has been equally characterized. The results show that the compaction capacity of the aggregate is reduced after successive recycling. It has been possible to quantify how much the closed porosity of the recycled aggregate decreases with the number of times it is recycled. The loss of natural aggregate and increase of the volume of adhered mortar have also been evaluated using this technique. The Erasmus+Program, founded by the Staff Mobility for Teaching Program of the European Council 2016/217, between Instituto Superior Técnico - University of Lisbon and the LADICIM - University of Cantabria. CERIS and the Foundation for Science and Technology (FCT) for funding this research.

The effect of the incorporation of recycled ceramic aggregates from crushed sanitary ware, in coating mortars, as replacement of sand, is evaluated. Using these recycled aggregates allows the integration of a non-biodegradable waste in mortars. This brings considerable environmental benefits, both by reducing the extraction of natural sand and the deposits in landfills.To evaluate the performance of the mortars with sanitary ware waste a wide experimental campaign was developed, comprising a series of tests to characterize the behaviour of formulated mortars in terms of mechanical strength, water-related behaviour, durability and other properties. Four replacement ratios were tested (0%, 20%, 50% and 100%) of sand by aggregates from crushing sanitary ware waste keeping the grain size distribution constant.This research reveals that sanitary ware waste can be used as aggregates without affecting the mortars' performance. Many of the properties of the modified mortars (with sanitary ware incorporation) had a similar performance to that of conventional mortar. Furthermore, they showed improvements in terms of mechanical behaviour, in particular of flexural strength, and permeability to water vapour. Thus, the incorporation of a non-biodegradable material as substitute of natural sand is possible and advantageous for the environment and in terms of mechanical performance. Keywords: Recycling, Replacement, Mortar, Natural sand, Sanitary ware waste, Alternative aggregates

This paper presents a step-by-step design of a structural concrete element containing recycled aggregates in accordance with Eurocode 2 (EC2). The design of a reinforced concrete beam was made as one would normally do for conventional concrete, by using practical performance-based rules based on a wide literature review to predict the mechanical and durability-related performance of recycled aggregate concrete. This design is based on adjusting the cross-section’s geometry of the reinforced recycled aggregate concrete beam in a way that it is capable of withstanding the same durability-related service life, similar load bearing capacity and within the same limits for deflection according to the serviceability limit state as per EC2. In most of the scenarios considered in this study, the results showed that a slight increase to the nominal cover of reinforced recycled aggregate concrete was required to exhibit the same service-life as that of a conventional concrete beam subjected to the same environment. Furthermore, although no fundamental alterations were required to the amount of reinforcement, the cross-section’s height was increased to maintain the maximum deflection within the limitations imposed by EC2.

This paper presents an experimental investigation on the cyclic behaviour of short steel tubes filled with rubberized concrete (RuC), a composite material that mixes concrete with rubber particles. A brief literature review on the cyclic behaviour of CFST columns, the mechanical properties of RuC and recent research on RuC-filled steel tubes (RuCFSTs) is presented. Then, the tested specimens are characterized, comprising three cross-section shapes (square, rectangular, circular), three steel grades (S235, S275, S355), three concrete mixes (0%, 5%, 15% of rubber particles content) and two axial load levels (10%, 20% of axial plastic load). After that, the loading protocol, test rig and experimental procedure are described in detail. The experimental results are extensively discussed, focusing on the columns’ cyclic strength, failure modes, hysteretic and envelope curves, as well as on the energy-based ductility factors. Finally, conclusions are drawn regarding all these parameters. The most relevant achievement is that a concrete mix with a low content (5%) of rubber particles leads simultaneously to the lowest decrease (5%) in the cyclic strength and the highest increase (52%) in the ductility of RuCFST columns, thus being the most suitable mix to use in seismic areas, where ductility and energy dissipation requirements are mandatory.

This paper presents a systematic literature review of 114 publications published over a period of 39 years from 1977 to 2015, alongside a meta-analysis of collated data sourced from publications concerning the effect of incorporating recycled aggregates, from treated construction and demolition wastes, on the performance of cementitious renderings and masonry mortars. Several of the most relevant properties were evaluated regarding the mortars’ fresh state and their mechanical, physical and durability-related performance. The results suggest that an increasing content of recycled aggregates may reduce the performance of some of the masonry mortars, which can nonetheless be easily compensated, but most recycled aggregates mortars for rendering applications have shown comparable performance to that of conventional mortars and complied with the requirements of the European Standardization.

Information on the effects of incorporating fine recycled ceramic aggregates on concrete's durability is very scarce. This paper presents an experimental study using aggregates sourced from crushed red clay ceramic bricks (CBAs) and sanitary ware (SWA). Different concrete mixes were produced where the fine natural aggregate fraction was partially or fully replaced (20%, 50% and 100%, by volume) by each of these materials. Shrinkage, water absorption by immersion, water absorption by capillary action, carbonation and chloride ion penetration tests were carried out. Results show that using fine CBA provides better performance in terms of water absorption by capillarity and chloride ion penetration, contrarily to shrinkage, water absorption by immersion and carbonation penetration. Using fine SWA leads to a similar performance in terms of shrinkage, but all other properties are significantly and detrimentally affected. Notwithstanding the increased water requirement due to the high absorption capacity of CBA and the formation of agglomerated particles with SWA, this paper shows that a judicious use of these materials may allow the production of adequate structural concrete; in mixes with SWA the use of superplasticizers is a very effective approach in preventing the formation of clusters, even providing a better performance than the control concrete. Keywords: Construction and demolition waste, Recycled aggregates, Concrete, Crushed bricks, Sanitary ware, Durability

In order to study the behaviour of concrete structures made with coarse crushed concrete aggregates recycled from discarded elements from the precasting industry, extensive testing was performed in four full-scale structures with varying recycled aggregate (RA) ratios. This paper describes and analyses the results of vertical load tests on each slab of these double-floor structures. The Young’s modulus ( E ) of the concrete mixes was estimated by finite element model calibration using deflection data from the tests. The response pattern of the various structures was the same and the aggregates used had a small influence on E , even smaller than the execution conditions. One of the concrete mixes included a superplasticizer (SP) and this product more than offset the loss of stiffness due to RA use. To the authors’ best knowledge this is the first study ever concerning the behaviour of full-scale recycled aggregate concrete (RAC) structures subjected to vertical loading and the behaviour of slabs with significant replacement of conventional aggregates by RA.

Recently, both nationally and internationally, cement-treated granular materials (CTGMs) have been widely used as road base layer. However, all the researches on CTGM with recycled aggregates (RA) are limited to the coarse fraction, with a size range of 0–40 mm. In Spain, one of the recycled materials most commonly produced in construction and demolition waste (CDW) treatment plants is a mixture with around 75% of fine recycled aggregates (hereby called FRA), with 5–8 mm nominal maximum size. This material is commonly used in pipe bedding, an application that provides little or no added-value. The intent of this paper is to study the feasibility of using CTGM made with FRA as road base layer. For this purpose, six mixtures have been produced, comprising 0–8 mm FRA and 0–40 mm coarse aggregates, made of mixed recycled aggregates and recycled concrete aggregate. The main mechanical (unconfined compressive strength and modulus of elasticity) and durability (dimensional changes) properties were studied and th...

This paper provides a systematic literature review, based on the identification, appraisal, selection and synthesis of publications relating to the effect of incorporating recycled aggregates sourced from construction and demolition wastes, on the creep behaviour of concrete. It identifies various influencing aspects related to the use of recycled aggregates such as replacement level, size and origin, as well as mixing procedure, exposure to different environmental conditions, use of chemical admixtures and additions, and creep of recycled aggregate concrete after unloading. A statistical analysis on the collated data is also presented with the purpose of understanding the creep behaviour of concrete, based on the replacement level of recycled aggregates. The evidence gathered was also compared to a model for compliance prediction. Correction factors of the creep coefficient of concrete with varying recycled aggregate content are presented in this paper. Some of the prediction models are feasible for use in recycled aggregate concrete.

Europe is a consolidated continent, characterized by a wide range of ancient buildings that urgently need refurbishments, especially in seismic zones such as Portugal, where structural reinforcement is imperative. However, demolishing and reconstructing also contributes to real estate renovation. In these cases it is simpler to build earthquake safe buildings that comply with current standards of comfort and quality. The question now is whether refurbishment (and what type) is environmentally and/or economically profitable or needed compared with new construction. To answer this question, this work used the life cycle approach in two complementary approaches: a literature review that theoretically compares different LCA works for refurbished and new buildings; and a real LCA and LCC case study for a classified ancient Portuguese building located in Lisbon, where real refurbishment is compared with hypothetical demolition, followed by complete reconstruction on the same site, respecting the same architecture, constraints and demands, and using reinforced concrete and clay brick walls. This issue is very urgent in Portugal, because of its extensive stock of ancient buildings needing refurbishment works. Moreover, there are few studies reporting whether the refurbishment can be economically and environmentally more efficient, according to the Portuguese economic environment. Thus, this study mostly contributes to this debate, first at a national level, and then as a new case study reporting this kind of benchmarking, and its significance is related to the actual results measured at the construction site for the traditional refurbishment works made in Portugal. This comparison showed that structural refurbishment seems to be environmentally more positive. Nevertheless, in the case-study gains were not as high as commonly suggested, mainly because of the massive use of structural steel and shotcrete required for the seismic and structural strengthening of the ancient building. Finally, as far as the economic approach is concerned, this paper concludes that in those conditions rebuilding would make more economic sense than refurbishing. These conclusions indicate that an integrated decision-making process is needed and also stress the development of new financial facilities for refurbishment and, especially, the development of less costly solutions that could save scarce resources and incentives.