Abstract According to Global Cement and Concrete Association (GCCA), the cement industry is responsible for about 7–8% of all anthropogenic CO2 emissions released into the atmosphere as reported by GCCA et al. (CCUS in the Indian Cement Industry: A Review of CO2 Hubs and Storage Facilities, 2024). Clinker production results in high energy costs and the release of CO2 due to the calcination or decarbonation of its main raw material, limestone. In addition, energy is consumed to heat and maintain the temperature inside the rotary kiln, involving another significant CO2 release. This work presents a review of mitigation processes in seven Ibero-American countries (Argentina, Brazil, Chile, Colombia, Peru, Portugal and Spain) that guide the cement industry toward carbon-neutral production by 2030 and 2050. The mitigation parameters are analysed based on the global roadmap published by GCCA (Global Cement and Concrete Association), FICEM (Inter-American Cement Federation) and CEMBUREAU (European Cement Association), as well as the national roadmaps. The six main parameters identified across the countries’ roadmaps were the reduction of total direct CO2 emissions in cement production, thermal efficiency, electrical efficiency, the clinker factor, the use of alternative fuels and (re)carbonation. The adoption of biomass as an alternative fuel and the reduction of the clinker factor through the use of SCM were identified as the main strategies for lowering CO2 emissions from Portland cement production in all seven countries analysed. Despite current efforts, CO2 mitigation in the cement industry has limits. Achieving carbon neutrality by 2050 will require substantial investment in CO2 capture, storage and utilization technologies.

Sun coral (Tubastraea spp.) is an invasive marine coral species responsible for severe ecological disturbances in marine ecosystems, resulting in high removal and monitoring costs in coastal infrastructure. Although previous studies have explored the use of this material in cementitious composites, the main novelty of this research lies in investigating the incorporation of sun coral waste as a supplementary cementitious material (SCM) in clinker-based systems. In this study, clinker was partially replaced at levels of 0%, 5%, 10%, 15% and 25% (by mass). Physicochemical properties, dimensional and mass variations of these innovative cementitious composites were explained based on calorimetry, X-ray diffraction (XRD), thermogravimetric (TG), derivative thermogravimetry (DTG) and mercury intrusion porosimetry (MIP) analyses. The results demonstrated that the sun coral waste affects cementitious systems mainly through physical mechanisms, nucleation effects, improved water redistribution, and pore refinement. Furthermore, calcium carbonate (CaCO3) contributes to monosulphate (AFm) phase transformations, leading to the formation of ettringite (AFt) and monocarbonate (Mc) phases, which are associated with enhanced phase stability and improved microstructural integrity. The observed effects were strongly dependent on the replacement level and application conditions. These findings indicate that sun coral waste presents potential as a novel supplementary cementitious material, provided that its use is technically controlled, contributing to the valorisation of marine waste and the development of more sustainable cement-based materials.

This study describes an environmental life cycle assessment (LCA), including an ecotoxicity analysis, of municipal solid waste incinerator bottom ash produced by a Portuguese waste-to-energy power plant. The LCA followed a “cradle-to-gate” (A1-A3) approach of the bottom ash production process itself and compares concrete mixes containing it with those using fly ash or Portland cement. The study uses site-specific data as input in the SimaPro software to evaluate the impacts associated with producing 1 tonne of bulk bottom ash at the plant’s exit gate. The results infer positive outcomes in all categories except natural resources depletion and renewable energy consumption: global warming potential decreased by 20% (–0.18 kg CO 2 eq) and non-renewable energy demand also improved with a 1 724 MJ reduction. These were attributed to waste treatment, especially recycling steel, aluminium, and ferrous and non-ferrous metals following sorting, which is a prerequisite for bottom ash processing. Applying these results to alkali-activated concrete mixes highlighted a 59% reduction in acidification potential and a 57% reduction in non-renewable energy use, despite a 442% increase in global warming potential compared with mixes using alternative binding agents. In the second part of the study, detailed chemical and biological analyses compared binders in bound and unbound forms. Ecotoxicity-related trials showed a shift from Class IV to Class III, with toxicity units for Daphnia magna decreasing by 89% when substituting cement with alkali-activated bottom ash, thereby demonstrating the material’s technical viability from an environmental hazard perspective.

Concrete is one of the most widely used construction materials, yet its production is associated with significant environmental impacts. One approach to mitigate such impacts is to use alternative aggregates. However, the limited knowledge about the availability and benefits of these unconventional materials, as well as concerns about their quality and performance, have hindered their adoption. This paper aims to analyse the potential benefits and limitations of using alternative aggregates in concrete by reviewing examples from three primary sources: construction and demolition waste (CDW), end-of-life materials (i.e., tyre rubber, glass, and plastic), and forest and agricultural waste (i.e., rice husk, wood, and hemp). First, the main sources and treatment needs are analysed. Then, a comprehensive macro analysis is provided on the physical and mechanical properties of concrete materials, discussing the results in terms of the aggregate nature and substitution ranges. The collected experimental data are also compared with estimations based on different models from two published codes, suggesting that more specific design-oriented models need to be developed to relate concrete’s physical and mechanical properties using different waste-type aggregate replacements. Selected data analyses are presented to help the readers obtain the optimum content for specific structural or non-structural applications. Examples of successful application of alternative aggregates in construction projects and products are also provided and discussed.

In the European Union, when sawn timber has a structural use, it must be classified in strength classes according to the standard EN 14081-1. Strength classes classify each sawn timber element according to its strength, stiffness and density properties. The environmental impacts of sawn timber for structural use have been calculated in several life cycle assessment studies, however, these studies use 1 m3 of sawn timber as functional unit, without specifying the strength class. This means that the environmental impacts calculated for one cubic meter of sawn timber do not take into account its structural use. The structural use of sawn timber products should be taken into account when calculating environmental impacts because in the process of design a timber-based structure, the structural class is essential to determine the volume of timber required. Thus, the main goal of this study is to develop and present a methodology to quantify the environmental impacts of various strength classes by using the results of mechanical grading for a sample of sawn timber of a given wood species from a specific region of origin. This methodology consists of two steps: i) data collection (identification and collection of existing data for combinations of wood species and regions of origin – allocation yields), and ii) allocation of environmental impacts to the various strength classes. In this study, the methodology is applied to a case study of Maritime pine wood from Portugal.

The present work intends to encourage a more widespread application of concrete mixes containing wood waste by investigating the steel-concrete bond of ordinary steel reinforcement bars and prestressed strands to assess the feasibility of using these composites in structural applications. After a set of preliminary tests, two mixes were selected in which aggregate was partially replaced by wood chip and sawdust. The effect of the steel-concrete bond length and reinforcement diameter on the shear strength was evaluated for steel bars and two-wire strands. The incorporation of wood appears to create a better mechanical interaction by increasing the component of friction as a resistance mechanism. In the case of the strands, the bond resistance is significantly higher (above 2.3 MPa) than the reference (0.9 MPa), regardless of the wood-concrete composites and the bond length. Additional tests have been performed to evaluate a possible creep effect. The specimens were subjected for 120 h to a constant tensile load corresponding to 50% of the mean results of the pull-out test. Results show that incorporating wood does not enhance the creep for this load level. Full-scale structural elements were also constructed to assess the feasibility of using these composites in structural applications. Bending and bending plus fatigue tests were performed to determine the behaviour under static and dynamic loads. It was concluded that the reference concrete without wood incorporation cracked for lower loads (26.0 kN) than the composites with wood (above 38.8 kN) and presented much higher bending stiffness (27835 kN.m2) than the wood-concrete composites (below 8544 kN.m2). The wood concrete with sawdust resisted fatigue tests without cracking.

Climate change could have a significant impact on buildings if its effects are not properly recognized. The consequences of climate action should be considered at the design and maintenance planning stage, with the objective of promoting the overall durability of constructions. Portugal, being part of the Mediterranean region, Southern Europe, and the Iberian Peninsula, and sometimes highlighted in projections as a critical area, is an example of a country considerably vulnerable to climate change impacts. The climate is expected to become warmer and drier, with a substantial rise in temperature and fall in precipitation by the end of the century. What implications will these changes have on the degradation of façades? Climate agents, such as temperature, solar radiation, humidity, precipitation, and wind, directly influence the performance of external claddings that protect internal building components. Cement render is the prevalent façade cladding in Portugal and Europe. Research to assess the risks of future climate-induced degradation on rendered façades is relevant in the context of buildings’ durability and adaptation to climate change. The objective of the present research was to define expectations about the impact of a progressively warmer and drier climate on the degradation of exterior cement renders, based on an analysis of related literature. Generally, less staining and more cracking are expected. Expectations about salt weathering and loss of adhesion are more uncertain and need further research.

In this research, the durability performance of sustainable concrete with the incorporation of reactive magnesium oxide (MgO) and fly ash (FA) was evaluated. The partial replacement of cement with these two materials is an appealing solution for the construction sector due to sustainability benefits and shrinkage reduction. The incorporation of FA by partial replacement of cement was carried out at 0%, 15% and 30%. The incorporation of MgO in concrete was carried out at 0%, 5%, 10% and 20%. Two types of MgO were used, one from Australia and another of Spanish origin. These two materials were evaluated in terms of their individual incorporation, and then an evaluation was carried out when the two were simultaneously used. In terms of durability, performance losses between 3% and 95% were obtained in all tests (water absorption by capillarity and immersion, carbonation depth and resistance to chloride penetration). However, over time, the difference in performance relative to the reference concrete tends to decrease due to the slow hydration that characterizes these two alternative materials. It was found that, in most of the tests, no overlapping of the negative effects occurred. In other words, the simultaneous incorporation of MgO and FA caused performance losses lower than the sum of the losses of their individual incorporation.

This study compares the environmental impacts of various durability scenarios of a case-study wood structure, including variations on wood species, preservative products and treatment methods. The method applied in this study compared the environmental impacts of various durability scenarios exposed to use class 3.1 during 30 years. Durability scenarios vary in terms of wood species (Softwoods - Cryptomeria, Spruce and Maritime pine; and Hardwoods - Eucalyptus), treatment methods (superficial (ST) and pressurized (PT)), arid preservative products (solvent-based insecticide and fungicide - used for ST, and water-based biocide - used for PT). The system boundary included: preservatives production, sawn wood production, application of preservative treatment, use and end-of-life. The environmental impacts were calculated with the methodology given by EN 15804+A2. Eucalyptus and Spruce species do not have enough durability for the defined use class even when treated with pressurized methods. The results show that softwoods treated with ST have the lowest impacts on the majority of impact categories, followed by Maritime pine treated with PT. The majority of impacts categories are mainly influenced by treatment and wood production. The emissions during the use and end-of-life stages have a high influence on "Eco-toxicity (freshwater)" and "Human toxicity, cancer effects" categories, respectively.

The main factor that alters the quality of recycled concrete aggregate (RCA) is the paste adhered to the natural aggregate (NA). Since it causes weakening of the interfacial transition zone (ITZ) between the aggregate and the cementitious paste, it becomes a determining factor for the mechanical behavior of concrete. It turns out that it is critical to enhance this interface by improving the surface of the aggregate or by removing the paste adhered to the NA. Considering the variety of methods for removing paste adhered to RCA-namely using acids such as hydrochloric acid (HCl), sulfuric acid (H2SO4), and phosphoric acid (H3PO4), among others-this paper presents a review of treatments for the removal of adhered paste using acidic solutions on the RCA, and their influence on the mechanical properties and durability of concrete produced with RCA. Pearson's correlation was used in the statistical analysis to determine the linear relationship of the main factors-for instance, immersion time, acidic solution, and aggregate size-involved in the removal of the paste in the RCA.

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

Concrete resistance to chloride ion penetration is an important parameter against the corrosion of rebars. The rapid chloride permeability test has already been used to predict UHPC’s resistance at ages up to 28 days under different curing regimes. However, the simple and non-destructive surface electrical resistivity (ER) method, standard specimens, for longer than 28 days and the effects of sulphate and chloride have seldom been considered in UHPC. Here, the ER and compressive strength (CS) tests were performed on 45 UHPC cylindrical specimen with a diameter of 10 cm and a height of 20 cm cured in water,10% magnesium sulphate and 3.5% sodium chloride solutions for 7, 14, 28, 56 and 90 days. The ER, CS and density increase with age. However, concerning the reduction in ER, the chloride environment was more damaging than the sulphate one. In addition, sulphate had a more destructive effect than chloride on the 90-day CS, so that 3.5% sodium chloride and 10% magnesium sulphate solutions resulted in a decrease after 90 days of 8.73% and 25.5% compared to the control sample, respectively. Furthermore, the curing process affected density’s evolution. Chloride ion penetration was negligible in the specimens cured in water and very low in those cured in the sodium chloride and magnesium sulphate solutions. The results were interpreted by XRD, EDS and SEM. A correlation between ER and CS is proposed.

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

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

Alkali-silica reaction (ASR) is considered one of the most concrete degrading agents causing expansion due to a gel formation that swells in contact with water. In this regard, this study investigates ASR through an expansion test of mortars produced with recycled aggregates (RA). The RA were prepared by crushing source concrete (SC) mixes that were previously produced with alkali reactive natural aggregates (NA). SC mixes were exposed to different environments to accelerate ASR. The mortars were tested using the ASTM C1260 accelerated mortar bar test (AMBT). For comparison purposes, the aggregates were also tested using the RILEM AAR-3 concrete prism test (CPT). As for mortars with NA, changes were needed to optimize the mix production procedure to obtain a mouldable mortar and more trustworthy values. For this purpose, RA-mortars were produced with RA obtained from primary or secondary crushing, different water adjustment types, including the addition of constant volumes of water to maintain a mouldable slump, the addition of 50% of the total absorption water, and pre-saturation of RA. The results showed that the adjustment type of RA absorption water in the mix highly influenced the expansion results. The addition of constant volumes of water to maintain a mouldable slump led to the more trustworthy values. The expansion limits of ASTM C1260 seems be too high for fine RA's evaluation.

In the field of building inspection and diagnosis, uncertainty is common and surveyors are aware of it, although it is not easily measured. This research proposes a model to quantify uncertainty based on the inspection of rendered façades. A Bayesian network is developed, considering three levels of variables: characteristics of the building, façade and exposure conditions; causes of defects; and defects. To compute conditional probabilities, the results of an inspection campaign from the literature are used. Then, the proposed model is validated and verified using inspection results from another sample, the combination of a strength-of-influence diagram and sensitivity analysis and the application of the model to a case study. Results show that the probabilities computed by the model are a reasonable representation of the hesitancy in decision making during the diagnosis process based only on visual observation. For instance, design and execution errors show lower probabilities due to not being verifiable a posteriori without detailed documentation. The proposed model may be extended and replicated for other building materials in the future, as it may be a useful tool to improve the perception of uncertainty in a key stage of building maintenance or rehabilitation.

This paper intends to analyze the performance of mortars with reactive MgO, as a sustainable alternative to cement. Six different MgOs from Australia, Canada, and Spain were used in the production of mortars as partial substitutes for cement, namely 5%, 10%, 15%, 20%, and 25% (by weight). MgOs with different levels of reactivity were used to analyze its influence on the performance of MgO mortars. In order to evaluate the mechanical performance of these mortars, compressive strength, flexural strength, dynamic modulus of elasticity, and ultrasonic pulse velocity tests were performed. Compressive strength tests showed that the use of 25% reactive MgO can cause a decrease of this property of between 28% and 49%. The use of reactive MgO affected the other mechanical properties less. This paper also intends to analyze the durability performance of mortars with reactive MgO. To that effect, water absorption by capillarity was assessed. In this research, the effect of using MgO on the shrinkage was also analyzed. It was found that shrinkage may decrease by more than a half in some cases.

In this paper, the process of design and evaluation of compatible materials to partially or completely substitute damaged interior walls and ceilings coatings made of gypsum-based plasters is presented and the results obtained are discussed. The methodology used comprised the definition of quantitative requirements to be accomplished by the new materials, based on previous works of the authors with characterization of an extensive set of samples of historic buildings. It was concluded that there is need to develop three different restoration materials, one for each family of plaster elements: thin-layer finishing plasters (L), elements moulded on site (M) and precast decorative elements (P). The physical and mechanical properties of seven mixes based on gypsum and lime, with addition of other components, were determined and allowed concluding that the binder proportions (gypsum: lime) is the most influential factor. Higher gypsum content leads to stiffer materials, less shrinkage and higher absorption coefficients than in lime-based mixes. The formation of micro cracks was pointed out as a possible cause for the decrease of flexural strength and water vapour permeability values of the M mixes. The comparison of the results obtained with the compatibility requirements allowed finding well-suited restoration materials for thin-layer coatings and precast elements. The mixes for moulded on site elements revealed to be the less balanced, and some adjustments are advised.

The use of mixed recycled aggregates (MRA) for the production of cementitious materials is still limited due to the high heterogeneity of the rubble sources and the lack of specific regulations, which contributes to maintaining the problems associated with the management of construction and demolition waste (CDW) in recycling plants. Therefore, this paper investigates the influence and effects of the use of MRA, collected over time, on the physical and mechanical properties of cement and lime-based mortars, based on a statistical modelling using Machine Learning algorithms. For this purpose, an extensive experimental programme with three stages was developed, intending to evaluate the variability of the MRA produced. The first phase consisted of the physical characterization tests of 36 samples of MRA. The second phase intended to perform technological tests to select the best volumetric ratio of cement: hydrated-lime: MRA (1:1:6, 1:1:7 or 1:2:9) to be used with 100% MRA (modified mortars). Finally, the third experimental phase investigated the physical and mechanical properties of the modified mortars produced with the volume ratio selected in the previous phase and using MRA collected at different periods of time. The results obtained were analysed using a T hypothesis test, a joint analysis of all variables using a Robust Principal Components Analysis (ROBPCA) and a partner recognition model based on data driven and ROBPCA (Data Driven Soft Independent Modelling of Class Analogy - DD-SIMCA). From the results, it was noticed that MRA 1:1:6 mortars presented a better performance in terms of mechanical strengths and water absorption by capillary, due to the filler effect of the MRA. As a matter of fact, the statistical tests have proven that no statistically significant differences were found in the physical properties of the 36 MRA samples and among the physical and mechanical properties of mortars in these periods investigated, which demonstrates the potentially reproducibility of CDW. Therefore, it was found that a proper selection and processing of CDW, as well as a definition of efficient mixing ratios can minimize the effects from the high heterogeneity of these wastes and enable the effective use of MRA in mortars. (C) 2020 Elsevier Ltd. All rights reserved.

Construction and demolition wastes (CDW) are generated at a large scale and have a diversified potential in the construction sector. The replacement of natural aggregates (NA) with CDW recycled aggregates (RA) in construction materials, such as mortars, has several environmental benefits, such as the reduction in the natural resources used in these products and simultaneous prevention of waste landfill. Complementarily, CDW have the potential to capture CO2 since some of their components may carbonate, which also contributes to a decrease in global warming potential. The main objective of this research is to evaluate the influence of the exposure of CDW RA to CO2 produced in cement factories and its effect on mortars. Several mortars were developed with a volumetric ratio of 1:4 (cement: aggregate), with NA (reference mortar), CDW RA and CDW RA exposed to high levels of CO2 (CRA). The two types of waste aggregate were incorporated, replacing NA at 50% and 100% (in volume). The mortars with NA and non-carbonated RA and CRA from CDW were analysed, accounting for their performance in the fresh and hardened states in terms of workability, mechanical behaviour and water absorption by capillarity. It was concluded that mortars with CDW (both CRA and non-carbonated RA) generally present a good performance for non-structural purposes, although they suffer a moderate decrease in mechanical performance when NA is replaced with RA. Additionally, small improvements were found in the performance of the aggregates and mortars with CRA subjected to a CO2 curing for a short period (5 h), while a long carbonation period (5 d) led to a decrease in performance, contrary to the results obtained in the literature that indicate a significant increase in such characteristics. This difference could be because the literature focused on made-in-laboratory CDW aggregates, while, in this research, the wastes came from real demolition activities, and were thus older and more heterogeneous.