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

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

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

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

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.

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.

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.

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.

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.

Various treatments of phosphogypsum samples extracted in Huelva, Spain, curing conditions and incorporation ratios were studied to evaluate the viability of being used as set regulator or as supplementary cementitious material to improve the mechanical behaviour of cement mortars. The physical-chemical properties, mechanical behaviour and environmental impact of these phosphogypsum-based cement mortars were determined. It was concluded that the phosphogypsum treatments and curing conditions influence the mineralogical transformations of mortars and therefore also the mechanical behaviour of the mortars tested. Furthermore, the heavy metal impurities in the phosphogypsum were immobilized in the cement matrix, leading to a clear improvement of the technical properties of cement mortars made with this waste compared to the traditional use of natural gypsum.

The aim of this paper is to improve the contribution of the Life Cycle Assessment (LCA) methodology to setting up a cradle to cradle (C2C) life cycle of building materials. For this, the rules included in the most recent European Standards for the environmental assessment of the waste flows in the life cycle of these materials were taken into account. The paper starts with the identification of the waste flows that can be generated or used throughout the life cycle of building materials. Standardized calculation rules for the evaluation of the environmental impacts and benefits of these flows are then described and analysed in detail. Finally, a summary of the information available in LCA databases related to the end-of-life of construction materials is presented, and selected case studies are examined to provide an overview of the contribution of the LCA approach described in European Standards to close the loop in the life cycle of building materials. This paper demonstrates that results achieved through the application of the most recent European standards on the environmental assessment of waste flows can be an important source of data for decision-making at the end-of-life of building materials, especially to ascertain whether the minimization of waste flows, the maximization of their reuse or recycling operations, or the increase of the recycled content maximizes their C2C environmental performance. This work's innovation lies mainly on the systemization, visual representation and analysis of the rules for environmental assessment of the waste flows in the life cycle of building materials, namely the ones defined in the most recent European Standards (EN 15804; FprEN 15978), and on the verification that the later can promote a C2C perspective in LCA of construction materials.

In the light of the ever-increasing need of circular economy in the construction industry and of the recent advances in research and development on the use of recycled aggregates, produced from construction and demolition waste, in new construction materials, this paper presents a compilation of representative case studies of several applications, namely recycled aggregates in unbound, hydraulically-bound and bitumen-bound applications, as well as in (non-)structural concrete in road and building construction. Experience has shown that, in spite of the positive outcomes and comprehensive know-how gained over the course of several years in those exploratory studies, there is a considerable underuse of recycled aggregates mostly due to lack of confidence in the material amongst contractors and designers. This paper, using a range of case studies undertaken in several countries worldwide, highlights the technical viability and appropriateness of using recycled aggregates in a broad range of construction applications.