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The search for sustainable alternatives for waste disposition other than disposal and evaluation of the feasibility of a second life cycle for waste should be a priority in the research and characterisation of alternative materials. In civil engineering infrastructure applications (e.g. railway, pipe bending, or road construction), large volumes of aggregate are required, which necessitates the consumption of natural resources and significantly impacts soils and the environment in the surrounding area. Occasionally, when the in situ soil does not possess the appropriate mechanical properties or has low load bearing capacity for traffic or other loads, chemical stabilising agents are used to improve the soil characteristics. However, the development and implementation of sustainable alternatives must become a priority in economic, social, scientific, and technical strategies to address current environmental challenges. This study analyses the environmental viability of using eco-friendly agents instead of the chemical additives traditionally used in soil stabilisation. Based on the findings, it is affirmed that the bottom ashes from the combustion of an olive and grape waste biomass in cogeneration plants possess adequate properties as an eco-stabiliser, are not harmful to the environment, and are feasible as an eco-agent for expansive soils in civil engineering works.

For many decades, researchers have been working on finding innovative and sustainable solutions to address the enormous quantities of plastic waste that are produced every year which, after being collected, are transformed into energy, recycled, or sent to landfills. Giving a second life to plastic waste as a material to be incorporated, in the form of macro-fibres, into concrete, could be one such solution. The purpose of this study was to analyse the mechanical and physical behaviour of the hardened concrete reinforced with macro plastic fibres (RPFs) obtained from food packaging waste (FPW) discarded during the packaging phase. By varying the quantity of macro-fibres used, physical and mechanical properties such as compressive strength, modulus of elasticity, flexural strength, and toughness were evaluated. It was observed that, although the presence of macro plastic fibres reduced the mechanical resistance capacity compared to that of traditional concrete, their contribution proved to be of some importance in terms of toughness, bringing an improvement in the post-crack resistance of the composite material. This innovative mixture provides a further impulse to the circular economy.

In our modern, fast-paced life, plastic is a versatile material essential to our economy, daily life is unthinkable without it. However, there are serious downsides for the environment and health, which are becoming more and more stark in our society, and the recycling of plastic offers a partial solution to these widespread problems. The present work delves into the environmental assessment of fibre-reinforced concrete specimens, made with recycled plastic fibres from food packaging waste. Leaching tank tests for the evaluation of the long-term release of pollutant elements, identification of leaching mechanisms, and the diffusion process of contaminants into the environment were conducted on fibre reinforced concrete. The results showed that the incorporation of the recycled plastic fibres, classified as non-hazardous, did not release relevant levels of any potential harmful element incorporated in concrete. Moreover, low mobility was detected in the studied elements and different release mechanisms were identified through long-term diffusion leaching tests. Hence, the environmental feasibility of the incorporation of recycled plastic fibre in concrete was proven. This study strengthens the objectives set out by the Circular Economy Action Plan, which includes the European Strategy for Plastics and aims to, among other things, boost the market for recycled plastics.

La actual exigencia técnica del manejo de programas de diseño en el ámbito de la Ingeniería Civil y la Edificación lleva a plantear de forma indispensable la necesidad de formación de los futuros profesionales en la metodología BIM (Building Information Modeling).Mediante el presente Proyecto de Innovación Docente se ha desarrollado un modelo de implantación de esta metodología adaptándolo al programa actual de cada asignatura y a las competencias exigidas. La metodología y conocimientos teóricos y prácticos de las herramientas BIM han sido impartidos a 40 alumnos aproximadamente pertenecientes a tres títulos y niveles universitarios diferentes. Los resultados obtenidos muestran una evaluación satisfactoria por parte de los alumnos, respondiendo mediante la enseñanza de nuevas herramientas de diseño a las crecientes necesidades profesionales y enriqueciendo las habilidades de los estudiantes universitarios.

Construction and demolition recycling is regarded as an essential subject in the EU, as the target established by its policies to 2020 ratio is far from being achieved. The use of materials recycled from such waste has been widely deemed a contribution to the sustainability of the construction sector. Gypsum is one the limiting components of recycled aggregates used as a base layer in road construction. The aim of this research was to analyse the effect on mechanical properties, leaching behaviour and dimensional changes at long term in recycled aggregates with different gypsum contents. Load bearing capacity was conducted by California bearing ratio on prepared samples. Moreover, the compressive strength was conducted on samples prepared with a 3% cement addition. Both tests were studied long term. Dimensional changes were studied through swelling in California bearing ratio test mould under the modified Proctor conditions for 1 year and using an oedometer device for 5 months. Furthermore, environmental risk assessment was performed, classifying the material with gypsum addition as non-hazardous, given that sulphate anion was above the inert limit. Good mechanical behaviour in the long term and no significant dimensional changes were found regardless of gypsum content.

The identification of areas susceptible to gully formation is an objective that has important consequences for erosion control. It allows for the optimization of resources by focusing on prevention and control efforts on the most susceptible areas, avoiding the frequent evolution of ephemeral to permanent gullies. The issue is of great interest in Spanish olive groves, many of which are affected by serious problems of gully erosion.Gullies are formed in the swales, which allows the use of topography-based tools to predict their location.The Compound Topographic Index (CTI) proposed by Thorne et al. (1986) is calculated for each pixel as an estimate of the flow capacity to cause erosion, as it includes the product of the pixel draining area and its slope. Its application requires the identification of a critical value of the CTI (CTIc), above which the potential areas of gully occurrence will be located. Using historical orthophotos, the gullies observed were digitized for 2011 in the experimental areas called Morente (11 km2 of traditional olive groves on degraded and poor vertisols) and Matasanos (6 km2 of intensive olive groves also on vertisols) and nearby area, with cereal crops.The objectives of this work are: to identify CTIc values corresponding to cultivated areas in Cordoba, mainly olive groves; to develop and evaluate an application that allows a user without great technical skills to obtain the CTI; to evaluate the capacity of this CTIc to reproduce gullies observed in nearby areas or in different time periods (2005) to establish cause-effect relationships between changes in landuse in this type of phenomenon, using the aforementioned tool.Part of the digitized gullies, representative of olive grove areas, were used to obtain the CTIc of each gully, by modifying it until the best reproduction of the gullies observed was achieved, then their average value was taken as CTIc. To calculate the CTI, a 5m resolution DEM was used, obtained from LiDAR PNOA 2014.In the framework of the Innolivar project, a desktop GIS application has been developed in a free software environment such as QGIS, which allows the calculation of the CTI. The APET tool (AGNPS Potential Ephemeral Gully Evaluation Tool) recently implemented has helped in the development of this application.The CTI calculation by the application, after the determination of the CTIc threshold, serves to identify critical areas from a DEM, which is free and available in many countries. A first qualitative evaluation by visual verification indicates a very good characterization of the gullies. Subsequently, the goodness of fit of the gully position between the digitized gullies and the app-calculated gullies according to the CTIc is evaluated quantitatively by obtaining a binary confusion matrix by lengths. In the Morente area, an error of omission of 29% and of commission of 16% was obtained.It can be concluded that the application generated that allows the application of the CTI methodology makes identification of areas susceptible to gully formation possible in an efficient and relatively simple manner, helping to achieve a more sustainable agriculture.

The aim of this research work was the evaluation of the feasibility to utilize industrial by-products, such as electric arc furnace steel slags, for sustainable concrete production. The paper evaluated the environmental and mechanical properties of steel slags and concrete, respectively. Specifically, the release of contaminants from steel slags was investigated by leaching test and the properties of fresh and hardened concrete were evaluated for a concrete mixture designed with a partial substitution (30%) of natural coarse aggregates with electric arc furnace steel slags. The results show that the concentrations of pollutants were lower than the legal limits imposed by the Ministerial Decree 186/2006 and the addition of steel slag can enhance the mechanical performance of concrete. The compressive strength of cubic specimens was also measured after different cycles of alternate wetting&ndash, drying. The steel slag incorporation results in a stiffness comparable to that of a traditional concrete. Overall, the mechanical and leaching characterization has shown that the reuse of electric arc furnace steel slags for sustainable concrete production is feasible and reliable.

Construction and demolition wastes are widely recognized as the main waste stream in the EU, and their recycling and recovery is an important issue in sustainable building industry development. The composition of construction and demolition wastes is highly heterogeneous and is influenced by several factors, including the raw materials and construction products used. The environmental performance of these materials are therefore considerably variable and, in some cases, do not comply with the regulatory limits established to ensure the protection of the natural environment. In this context, this paper presents a data analysis on the environmental behavior of construction and demolition wastes and recycled aggregates in terms of both chemical composition and the release of contaminants according to a leaching test. Subsequently, the most critical parameters for recovery were identified and statistically evaluated. The leaching results showed that SO4, Cu, and COD are critical compounds for both CDWs and RAs.

The circular economy is an economic model of production and consumption that involves reusing, repairing, refurbishing, and recycling materials after their service life. The use of waste as secondary raw materials is one of the actions to establish this model. Construction and demolition waste (CDW) constitute one of the most important waste streams in Europe due to its high production rate per capita. Aggregates from these recycling operations are usually used in products with low mechanical requirements in the construction sector. In addition, the incorporation of photocatalytic materials in construction has emerged as a promising technology to develop products with special properties such as air decontamination. This research aims to study the decontaminating behavior of mortars manufactured with the maximum amount of mixed recycled sand without affecting their mechanical properties or durability. For this, two families of mortars were produced, one consisting of traditional Portland cement and the other of photocatalytic cement, each with four replacement rates of natural sand by mixed recycled sand from CDW. Mechanical and durability properties, as well as decontaminating capacity, were evaluated for these mortars. The results show adequate mechanical behavior, despite the incorporation of mixed recycled sand, and improved decontaminating capacity by means of NOx reduction capacity.

Electric arc furnace dust (EAFD) presents a pollution hazard due to its heavy metal leachability. Its characterization is essential for recovery or disposal in hazardous waste landfills. The present work discusses the results of encapsulating two electric arc furnace dust samples (EAFD1 and EAFD2) by means of the stabilization/solidification (S/S) technique in cement-based mortars. The pH influence on the leaching levels of Se, Mo, Cd, and Pb was evaluated using a pH dependence test as analytical support. In addition, the compressive strength of the S/S mortars was measured to verify its behaviour as a monolithic block. The leaching procedures for granular and monolithic mortars were carried out in order to classify the EAFD samples and the S/S mortars made with EAFD according to the legal limit values imposed by the EU Council Decision 2003/33/EC. Thus, the release levels of Se, Mo, Cd, Pb and chloride in the leachate form of EAFD exceeded the legal limit values, and both EAFDs were classified as hazardous wastes. Concerning the compliance test of S/S mortars after crushing, despite lower releases being registered, none of the S/S mortars in the granular state could be classified as non-hazardous waste due to the high Pb level registered. Finally, after analysing the release levels of S/S mortars of EAFD in the monolithic state, the S/S mortars of EAFD1 were classified as non-hazardous waste. Regarding the S/S mortars of EAFD2, despite the high reduction in the Pb release level after the S/S treatment, these mortars exceeded the hazardous legal limits.

This research aims to produce roller compacted concrete (RCC) using recycled aggregates (RAs) from construction and demolition waste (CDW) with low cement content. Previous research has confirmed t...

Green philosophy is gaining popularity worldwide. Recycling materials from building demolitions, reutilizing by-products from industrial facilities and exploring the potential uses of waste during a second life cycle are the objectives of this philosophy. In the present article, bottom ashes from electric power generation plants using biofuel combustion were evaluated to verify their potential use as expansive clay stabilizers. Two objectives are pursued: (1) finding a new use for waste that is typically landfilled despite its great potential arising from its technical properties and (2) improving the mechanical properties and reducing the expansive nature of the expansive clays identified during the construction of a motorway. Based on this framework, the present study demonstrated the potential of biomass bottom ashes to stabilize expansive clays. The optimum dosage to improve the properties of clays was determined based on performance parameters, such as plasticity, free swelling or soil collapse. Afterwards, the contaminating potential of ashes was evaluated, being classified as hazardous waste. However, the stabilized mixtures were classified as inert products, thus guaranteeing the environmental feasibility of their use. Finally, the technical application of the stabilized clays as filling materials for embankments and subgrade for light traffic roads was proved. Graphical abstract.

The use of wastes, recycled material and by-products in the construction sector requires technical and environmental validation of their application. The reduction of consumption of natural materials with the incorporation of recycled materials must be increasingly promoted by administrations and governments. Specifically, recycled aggregates from construction and demolition waste have been applied in the manufacture of concrete and mortar, as well as in road construction. These recycled materials and other waste or by-products which can be used in concrete manufacture, must be evaluated from an environmental point of view, through determination and analysis of the leachates that can be generated. The leaching of pollutant components from recycled materials such as metals, sulphates or organic components are influenced by the different chemical and physical properties of the material as well as environmental conditions. About the environmental characterisation of wastes, there are different standards that must be applied in the study of the leaching behaviour of eco-efficient concrete, such as CEN/TS 15862: 2012 which are explained in detail in this chapter.

Construction and Demolition Waste come from debris generated during construction, renovation and demolition of buildings, roads, and bridges. Recycling and reuse are essential in terms of sustainability, mainly from an environmental point of view. Although the recommendation of the use of these recycled aggregates is currently included in some technical specifications, its use is still not widespread due mainly to the lack of knowledge on their technical application. This work is a compilation of the recommendations proposed in the “Catalogue of road pavements with recycled aggregates”, supported by the construction of experimental stretches. It proposes different structural sections for road pavements by using recycled aggregates.

Twenty samples of recycled aggregates from construction and demolition waste (CDW) with different compositions collected at six recycling plants in the Andalusia region (south of Spain) were characterised according to the Landfill Directive criteria. Chromium and sulphate were identified as the most critical compounds in the leachates. To detect the sources of these two pollutant constituents in recycled aggregate, environmental assessments were performed on eight construction materials (five unused ceramic materials, two old crushed concretes and one new mortar manufactured in the laboratory). The results confirmed that leached sulphate and Cr were mainly released by the ceramic materials (bricks and tiles). To predict the toxicological consequences, the oxidation states of Cr (III) and Cr (VI) were measured in the leachates of recycled aggregates and ceramic materials classified as non-hazardous. The bricks and tiles mainly released total Cr as Cr (III). However, the recycled aggregates classified as non-hazardous according to the Landfill Directive criteria mainly released Cr (VI), which is highly leachable and extremely toxic. The obtained results highlight the need for legislation that distinguishes the oxidative state in which chromium is released into the environment. Leaching level regulations must not be based solely on total Cr, which can lead to inaccurate predictions.

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...

A focus on environmental sustainability during the last decade has led to greater use of recycled aggregates to reduce the exploitation of existing reserves. In addition, environmentally consciousness has led to an increased use of renewable energy. Biomass is an important source of energy, and it also leads to high generation of waste products from biomass combustion. Previous studies have investigated the use of recycled aggregates from construction and demolition in road bases and sub-bases with positive results. This paper aims to study the feasibility of incorporating biomass bottom ash produced in the combustion process mixed with natural aggregates and recycled aggregates for use in civil engineering. The analysis of the mechanical properties was positive, showing the ability to use biomass bottom ash mixed with natural or recycled aggregates in specified ratios. Valuing biomass bottom ash can reduce waste generation and may lead to economic and environmental benefits.

Extensive green roofs are urban construction systems that provide thermal regulation and sound proofing for the buildings involved, in addition to providing an urban heat island mitigation or water retention. On the other hand, policies towards reduction of energy consumption, a circular economy and sustainability are core in the European Union. Motivated by this, an experimental study was carried out to evaluate the environmental risk assessment according to release levels of polluting elements on leachates of different green roof substrate mixtures based on recycled aggregates from construction and demolition waste through (i) the performance in laboratory of two procedures: compliance and percolation tests and (ii) an upscaled experimental leaching test for long-term on-site prediction. Four plots were built on a building roof and covered with autochthonous Mediterranean plants in Cordoba, South of Spain. As growing substrate, four mixtures were used of a commercial growing substrate with different proportions of a fine mixed recycled aggregate ranging from 0 to 75% by volume. The results show that these mixtures were classified as non-hazardous materials according to legal limits of the Landfill Directive 2003/33/CE. The release levels registered in extensive green roofs were lower compared to the laboratory test data. This shows how laboratory conditions can overestimate the potential pollutant effect of these materials compared to actual conditions.

This research evaluates the short- and long-term properties of masonry mortar manufactured with different replacement ratios of natural sand by fine recycled concrete aggregates. The recycled materials were collected from a recycling plant and after passage through a 4 mm sieve, were directly used to make the mixtures, maintaining their original particle size distribution. A pozzolanic CEM-IV/A (V) 32.5 N, with 29% fly ash in its compositions, was used at a 1:7 volumetric cement-to-aggregate ratio. Five mortars with different replacement ratios by volume were tested: 0%, 5%, 10%, 20% and 40%. The data were analysed using one-way analysis of variance to determine whether the “replacement ratio” had a statistically significant effect on the different fresh and hardened properties. DRX and electron microscope techniques were used to examine the morphologies and evolution of the main mineral phases over time during a curing period of 180 days. The results proved that a replacement ratio of up to 40% is a viable alternative for producing environmentally friendly masonry mortar.

Urban solid waste from demolition and construction engineering sites has been demonstrated to be mechanically suitable for reuse in civil infrastructures. However, the application of recycled materials as a replacement for natural aggregates demands an assessment of the pollution potential of the material in its second life cycle. Actually, plant managers of construction wastes assess the materials according to concise leaching tests that do not consider the compaction stage of the materials when they are applied in civil infrastructures. For that reason, the aim of the present study is to evaluate the effect of compaction on the leaching behaviour of concrete and mixed recycled aggregates. A percolation test for materials under compaction conditions was designed. The release levels measured in the water percolated through the compacted aggregates were compared with a conventional percolation leaching test. Besides, the compliance test allowed identifying the most conflictive elements according to the measured concentrations in the leachate: chromium and sulphate. The results revealed that under compaction, the highest levels of release were obtained for the concrete material. It was due to its high susceptibility to compaction which increased the content of fine particles affecting to the leaching behaviour. The study also includes the formulation of an equation to determine the emission release time of pollutants. Calculations were developed for two common applications as granular material: embankments and structural road layers.

The present work discusses the results of an experimental study investigating the performance of cement-treated granular materials, which were prepared from natural aggregates, recycled concrete aggregates, crushed clay bricks and gypsum. Recycled aggregates can potentially contain large amounts of acid-soluble sulphates. High sulphate contents can lead to the formation of ettringite, which causes dimensional instability in cement-treated materials. The tested samples were manufactured with different types of cement (CEM II and Sulphate-Resistant Portland Cement) and different compositions of the recycled materials to observe the effects of the sulphate content on the mechanical behaviour and the dimensional stability. As a result, the influence of the amount of sulphates on the deformation was determined, which is an aspect that must be considered in applications of this recycled product in road layers.

Recycled aggregates from construction and demolition waste have previously been used to manufacture recycled concrete. Generally, these aggregates weaken the physical properties of concrete, such as the density, durability, compressive strength, flexural strength, water penetration, and chloride penetration. This is predominately attributed to the porosity of particles with adhered mortar or to ceramic particles. In other studies, cements with additions (fly ash, slag, silica fume …) were used to compensate for the effect of incorporation of recycled aggregates. In another, plasticizers were used to improve workability or mechanical properties of recycled concrete. However, the innovation of this research is the use of different amounts of cement according to replacement ratios of natural aggregates for recycled concrete aggregates to achieved structural concretes. Also, two different water/cement ratios were used to analyse if these reached compressive strength similar to control concrete manufactured with natural aggregates. The results revealed that a small increase in the volume of cement (12%) maintained the mechanical properties and reduced the loss of concrete durability. Therefore, increasing the amount of cement in recycled concretes is a feasible technique in works with low exposure to aggressive agents.

The production of energy from renewable resources, such as biomass, is increasing rapidly. Therefore, environmentally friendly and economic solutions to recycle the resulting by-products are essential. The present study was performed to search for possible applications of the biomass bottom ashes that result from biomass combustion at three biomass combustion plants located in the Andalusia region of southern Spain. The analysis of chemical parameters indicated the applicability of biomass bottom ashes as an alternative material in civil construction. Thus, the limiting chemical parameters were analysed according to Spanish regulations. According to the results, biomass bottom ashes could be used as filler in road embankments, cement-treated materials or non-structural concrete, depending on the replacement percentage. This study determined that a review of the chemical parameters specified by the limiting regulations is recommended to promote the use of biomass bottom ashes as a building material in applications that do not require high structural strength.

Biomass is a renewable energy source that is increasingly being used worldwide. However, because of recent increases in production, waste products from biomass combustion are becoming a relevant environmental and economic problem. In the present research, the technical feasibility of bottom ash from various Andalusian power plants is analysed to evaluate their potential use in civil engineering infrastructures. The physical, chemical and mechanical characteristics of this by-product is evaluated, and these parameters are compared to the technical specifications for roads imposed by Spanish regulation. It was determined that biomass bottom ash possesses acceptable properties to be used as a filler material in the core of road embankments over 5 m in height without additional precautionary measures, such as the construction of road shoulders.

The leaching behaviour of recycled materials from construction and demolition projects needs to be deemed acceptable before they are used for civil infrastructure. The study examines three leaching procedures for characterisation of the potential release of heavy metals and anions regulated by the EU Landfill Directive on seven recycled aggregates and two natural materials. The goal of the study is to relate the complex procedures designed for analysis of material leaching behaviour to quick leaching tests used for regulatory purposes. To integrate the data, results of the compliance test, availability test and percolation test were related to each other. The results revealed that two recycled aggregates (the asphaltic and a concrete material) could be classified as inert material and the remainder were categorised as non-hazardous. Finally, the statistical analysis conducted permitted the identification of the group of heavy metals which are close to their acceptance thresholds. Thus, the noticeable amounts of Ni, Cr, Sb, Zn and Cu warrant their consideration as relevant from an environmental point of view.

Social awareness aims to increase practical skills, such as sustainable development, which seeks to increase the use of different types of waste in construction activities. Although insufficient attention is sometimes given to these actions, it is essential to spread information regarding new studies in the field of waste recycling, which encourages and promotes waste use. Reusing and recycling construction waste in the creation of buildings and infrastructure are fundamental strategies to achieving sustainability in the construction and engineering sectors. In this context, the concept of waste would no longer exist, as waste would become a material resource. Therefore, this study analyses the behaviours of two unbound mixed recycled aggregates (MRA) in the structural layers of an unpaved rural road with low traffic (category T43). The sections were built on inappropriate soil (A-7-6) with a high degree of free swelling. The experimental road consisted of three sections: the first was made with natural aggregates (NA) that were used as a control, the second was composed of MRA in the subbase and NA in the base, and the third section was completely composed of MRA. The materials were characterised in the laboratory. The behaviours of the structural layers in the experimental road were determined by controlling compaction (“in situ” density and moisture) and measuring the deflections and load capacity (deflectometer) during the 18 months after construction. The results show that the sections made with recycled aggregates meet the technical specifications required by General Technical Specifications for Road and Bridge Works (PG-3). Therefore, the water-soluble sulphate content and Los Angeles abrasion coefficient limits can be increased for recycled aggregates without compromising the quality of this type of road with low traffic. To the best of our knowledge, this is the first study regarding the use of unbound MRA made from construction and demolition waste (CDW) in the construction of an unpaved rural road with low traffic on an expansive clay subgrade.

This research is focused on analyzing the environmental pollution potential of biomass bottom ashes as individual materials, as mixtures manufactured with biomass bottom ashes and granular construction aggregates, and these mixtures treated with cement. For the environmental assessment of all of the samples and materials mentioned, the following leaching procedures have been performed: the compliance batch test of UNE-EN 12457-3:2003 for aggregates and bottom ashes; the column test according to NEN 7343:1994 for the mixtures prepared in the laboratory; and the tank test by EA NEN 7375:2004 for analyzing the behavior of mixtures after their solidification/stabilization with 5% cement. After the discussion of the data, the reduction of the pollution load of the most hazardous biomass bottom ashes after their combination with different aggregates can be confirmed, which implies their possible application in civil infrastructures, such as filler embankments and road construction layers, without negatively impacting the environment. In addition, the positive effect of the stabilization/solidification of the cement-treated mixtures with a reduction of the heavy metals that were released at the highest levels, namely As, Hg Cr, Ni, Cu, Se and Mo, was proven

This paper evaluates the behaviour and the environmental impact of a mixed recycled aggregate from non-selected construction and demolition waste (CDW) in field conditions. For this purpose, one experimental unpaved rural road with two sections was built. Sections were formed with a poor subgrade (A-6) and two structural layers: the first section consisted of a base course and a surface built using a natural aggregate and a low quality mixed recycled aggregate, respectively, and the second section, which was used as a reference, consisted of a soft crushed limestone aggregate. The materials were previously characterised in the laboratory. Control compaction ensured that the materials were correctly set in place, and the bearing capacity of each fill layer was measured. The structural performance of the pavement was determined using a falling weight deflectometer, and the changes in the international roughness index and the bearing capacity over time were studied. The results show that the non-selected CDW can be recycled using a simple treatment to create low quality recycled material with a low embodied energy that can be used as an alternative to natural aggregates in unpaved rural roads. According to the technical specifications, the total sulphur compound (SO 3 ) and the soluble salts content can rise to 3.9% and 3.3%, respectively, without posing a sulphate leaching risk or a reduction in the quality of this type of work. This study is important for increasing recycling rates of non-selected CDW and will support sustainable development in the building sector.

In some recycled aggregates applications, such as component of new concrete or roads, the total content of soluble sulphates should be measured and controlled. Restrictions are usually motivated by the resistance or stability of the new structure, and in most cases, structural concerns can be remedied by the use of techniques such as sulphur-resistant cements. However, environmental risk assessment from recycling and reuse construction products is often forgotten. The purpose of this study is to analyse the content of soluble sulphate on eleven recycled aggregates and six samples prepared in laboratory by the addition of different gypsum percentages. As points of reference, two natural aggregates were tested. An analysis of the content of the leachable amount of heavy metals regulated by European regulation was included. As a result, the correlation between solubility and leachability data allow suggest a limiting gypsum amount of 4.4% on recycled aggregates. This limit satisfies EU Landfill Directive criteria, which is currently used as reference by public Spanish Government for recycled aggregates in construction works.

This article evaluates the behaviour and environmental impact of two recycled aggregates from selected construction and demolition waste (CDW) in field conditions. For this purpose, one experimental unpaved rural road with two sections was built in 2007. Sections were formed with an excellent subgrade (A-1-b) and two structural layers: the first section consisted of a base course and a surface built using a mixed recycled aggregate and a recycled concrete aggregate, respectively, and the second section consisted of crushed limestone aggregate as a reference. The materials were previously characterised in the laboratory. Control compaction ensured that the materials were correctly set in place, and the bearing capacity of each of the fill layers was measured. The structural performance of the pavement was determined using a Falling Weight Deflectometer, and changes over time in the International Roughness Index and the bearing capacity were studied. The results show that recycled aggregates from selected CDW can be used as an alternative to natural aggregates in unpaved rural road construction without risk of environmental impact. According to technical specifications, the soluble salt content can rise to 1.3% without reducing the quality of this type of road. This study is important for increasing recycling rates and creating a market for mixed recycled aggregates in Mediterranean countries such as Spain, which has one of the lowest recycling rates in Europe.

Each year, millions of tonnes of waste are generated worldwide, partially through the construction and demolition of buildings. Recycling the resulting waste could reduce the amount of materials that need to be manufactured. Accordingly, the present work has analysed the potential reuse of construction waste in concrete manufacturing by replacing the natural aggregate with recycled concrete coarse aggregate. However, incorporating alternative materials in concrete manufacturing may increase the pollutant potential of the product, presenting an environmental risk via ground water contamination. The present work has tested two types of concrete batches that were manufactured with different replacement percentages. The experimental procedure analyses not only the effect of the portion of recycled aggregate on the physical properties of concrete but also on the leaching behaviour as indicative of the contamination degree. Thus, parameters such as slump, density, porosity and absorption of hardened concrete, were studied. Leaching behaviour was evaluated based on the availability test performed to three aggregates (raw materials of the concrete batches) and on the diffusion test performed to all concrete. From an environmental point of view, the question of whether the cumulative amount of heavy metals that are released by diffusion reaches the availability threshold was answered. The analysis of concentration levels allowed the establishment of different groups of metals according to the observed behaviour, the analysis of the role of pH and the identification of the main release mechanisms. Finally, through a statistical analysis, physical parameters and diffusion data were interrelated. It allowed estimating the relevance of porosity, density and absorption of hardened concrete on diffusion release of the metals in study.

Construction and demolition wastes are suitable for use in road construction. However, leaching characterization of recycled materials is required to determine their pollutant potential and the consequence of their application in different scenarios. The motivation of this paper is derived from the increasing use of different leaching test methods. In Europe, the confusion resulting from the wide variety of tests used to evaluate environmental properties of construction materials implies that an evaluation of the current practices and the attempt to consolidate the approaches are required. Two equilibrium-based leaching tests (the Dutch test and the European standard) were conducted to assess the environmental impact of four recycled aggregates. Three natural limestone aggregates were used as controls. Both tests measure the potential release of hazardous elements under extreme conditions using different leaching parameters (L/S ratio, pH value and contact time). The results proved that pH is the most relevant factor on the assessment of the differences between leaching methods due to its strong control on the pollutant release. To classify the materials according to their environmental effects, the concentration limit values of the metals imposed by Council Decision 2003/33/EC were used as a reference. The comparison allowed the classification of the recycled aggregates as inert wastes, with the exception of the MR-2 aggregate, which was classified as non-hazardous material.