This study presents a multi-target particle swarm optimization (MT-PSO) approach for efficient concrete mix design. It simultaneously designs mixes with multiple predefined strengths under a constant water-cement ratio. A gradient boosting-based surrogate model, trained on experimental mix data, predicts compressive strength. The modified particle swarm optimization (PSO) algorithm accommodates multiple targets in parallel, allowing solution sharing across target groups. MT-PSO is compared with a repeated PSO (R-PSO) strategy that optimizes each target separately, both minimizing the absolute error between predicted and desired strengths. Across 30 independent trials, MT-PSO consistently achieves lower mean errors, smaller deviations, and faster convergence, often reaching R-PSO's final accuracy within only a few iterations. Moreover, MT-PSO requires over 85% fewer fitness evaluations. These results demonstrate the superior accuracy, robustness, and computational efficiency of MT-PSO for multi-target optimization problems.

In seismic structural engineering, different methods are used to evaluate performance. Simplified approaches provide conservative estimates, while advanced analyses achieve higher precision at the cost of significant computational effort. Nonlinear Time History Analysis (NTHA) remains the most reliable method, but its high computational demand has led many researchers to propose simplified models, often resulting in conservative outcomes. This study proposes an Artificial Intelligence (AI)-based method to approximate NTHA. An Autoregressive Neural Network (ARNN) is developed to generate complete time-history responses of structures with minimal error relative to NTHA. Using ground motion data and the first three fundamental periods as inputs, the ARNN replicates NTHA responses with high accuracy. Unlike conventional surrogate models that predict only peak responses, the ARNN produces the entire response history. The ARNN is further integrated with a moment-based reliability framework employing the four-moment Pearson distribution (4M-Pearson), enabling efficient and accurate seismic reliability assessment. A three-story base-isolated steel structure is analyzed as a case study. Results demonstrate that the proposed ARNN achieves high precision in predicting both structural time-history responses and seismic reliability.

Moss-covered bioreceptive concrete is a novel green vertical structure which can be applied to a wide variety of structures due to its low structural and maintenance requirements. One of the potential benefits of using moss-covered concrete is its ability to absorb sound, the extent of which is currently unknown. Therefore, the effectiveness in attenuating (urban) noise of six moss species in different hydration states was assessed and compared to bare concrete and other vertical green structures. Results show that using moss-covered concrete increases sound absorption compared to bare concrete in nearly all situations. The best-performing mosses overall were acrocarp species, particularly P. capillare, which reached a peak sound absorption coefficient of 0.86 and an average of up to 0.48 (50–6400 Hz). Its results are also relatively constant across hydration states. On the other hand, G. pulvinata outperformed P. capillare when dry, but not when hydrated or wet. The pleurocarp species showed the lowest sound absorption. Finally, the thickness of the moss layer has a minor impact on absorption. The acrocarp moss species compare favourably to (in)direct vertical green structures using climbing plants, whereas the sound absorption of the pleurocarp species is slightly lower. However, the sound absorption of moss-covered concrete is significantly lower than that of vertical green structures using a growing substrate (Living Wall Systems), as the substrate provides the bulk of the absorption in this case. In conclusion, the moss-covered bioreceptive concrete presents a viable alternative to (in)direct green structures, although benefits are mostly limited to frequencies above 1000 Hz.

Reducing CO2 emissions from concrete production requires effective recycling of cement, particularly its clinker component. Significant emission reductions depend on innovative techniques that extract high-quality cement fractions from recycled concrete, beginning with source separation strategies before demolition. This study developed a practical measurement approach using handheld X-ray fluorescence (HXRF) to identify cement types (i.e. cement classifications such as CEM I, CEM II/B-V, CEM III/B) in End-of-Life concrete. The research was conducted in two phases: First, laboratory testing of seven powder samples (milled river gravel and sand, three cement types: CEM I, CEM II/B-V and CEM III/B along with blast furnace slag and fly ash) and three cement paste prism types containing the three cement types established optimal measurement parameters and assessed moisture influence. Second, field measurements were taken on outdoor concrete blocks, containing the three cement types, after one year of weather exposure. Measurements were conducted on both the exposed surface and subsurface layers (after removing 0.1–5 mm of material). Results showed that powder samples can be accurately characterized with 10-second measurements, while concrete blocks require at least 20 s. HXRF measurements demonstrated good reproducibility with low coefficients of variation (CV) values, ensuring reliable cement type identification. Surface measurements are reliable only when the concrete is unaltered: coatings, paint, or weathering negatively affect accuracy, necessitating removal of the surface layer. Cement types were successfully distinguished using oxide concentrations (Al₂O₃, Fe₂O₃, P₂O₅, MgO) and their ratios (CEM III/B: Al2O3/Fe2O3 > 9.0, MgO/Fe2O3 > 3.0, MgO/CaO > 0.11, Fe2O3/Al2O3 < 0.11 and Fe2O3/CaO < 0.04; CEM II/B-V: P2O5/CaO > 0.005 and P2O5/Fe2O3 > 0.1; CEM I: P2O5/CaO < 0.005 and P2O5/Fe2O3 < 0.1). This study demonstrates that handheld XRF enables fast and reliable in-situ identification of the three studied cement types, supporting improved source separation and cement recycling strategies.

Bioreceptive concrete supports biological growth on its surface, but natural colonisation takes years, and indoor cultivation followed by outdoor translocation often results in poor long-term survival. This research aimed to develop a method for rapidly establishing a moss layer on bioreceptive concrete while ensuring long-term persistence and survival. The developed method comprised a two-step approach. First is the rapid establishment of moss on bioreceptive concrete indoors. Then, it is hardened and translocated outdoors. Findings indicate that the most effective method for growing moss on concrete indoors is to grow them at low light intensity (70 μmol m−2 s−1 full-spectrum), while watering daily for the first six weeks. Subsequently, watering can be gradually reduced to once every 4 days, inducing drought hardening. This resulted in significant coverage and growth for both acrocarp (Mcoverage = 15.1 %; Mgrowth = 11.2 mm) and pleurocarp species (Mcoverage = 51.7 %; Mgrowth = 15.5 mm). Finally, after outdoor translocation, the moss should be covered with a light-blocking cloth for a 3-month period to allow for adaptation to UV and high light intensity conditions. When applying this method to moss species (mixtures), it was found that T. muralis showed slow indoor growth but the best adaptation to outdoor conditions on both north- and south-facing surfaces. Contrarily, both P. capillare and B. rutabulum displayed faster growth under indoor conditions but showed poor surface adhesion when translocated outdoors, which can, in some cases, be improved by using species mixtures. This research is a first step towards identifying the factors influencing moss growth and survival on bioreceptive concrete in the built environment.

Vertical greenery systems (VGS) are recognized for providing a range of ecosystem services (ESS), including biodiversity enhancement, property value increase, and stormwater management. However, there are significant challenges in comparing VGS designs due to the lack of standardized metrics and the limited understanding of their integrated performance across multiple ESS. This study introduces a multi-criteria decision-making (MCDM) model to assess and compare the full spectrum of ESS provided by VGS. Through an extensive literature search, VGS typologies, system components, and performance metrics were identified for ESS and synthesized. The application of the MCDM model was tested in a case study, showcasing its potential for improving decision-making and selection of VGS designs. Findings from the literature review stress a need for standardizing research methods, improving data quantification, and explaining and modelling ESS interactions. The study concludes that the MCDM framework supports context-specific evaluations, while further refinement is needed to reduce subjectivity and to include emerging ESS. These approaches are critical for advancing both research and practical applications in green infrastructure.

Recycled Aggregate Concrete (RAC) represents a significant innovation aimed at reducing the carbon footprint in the construction industry. Over the past few decades, numerous investigations and experiments have confirmed the viability of RAC as a construction material when the optimal combination of recycled and natural aggregates is used. This study seeks to further enhance the application of RAC by providing a robust framework for determining the optimal RAC mixture. To achieve this, machine learning is developed to predict the compressive strength of RAC by considering various mixture properties. To improve the accuracy of these predictions, the Symbiotic Organism Search (SOS) metaheuristic algorithm is employed, not only to fine-tune the machine learning hyperparameters but also to select the most suitable model. In this study, the SOS algorithm is tasked with choosing between Artificial Neural Networks (ANN), Support Vector Machines (SVM), or Random Forests (RF), based on predefined upper and lower bounds for their hyperparameters. The resulting machine learning model is then integrated with the novel Pareto Front Symbiotic Organism Search (PF-SOS) to generate a Pareto front of optimal mixtures, with compressive strength and production cost as the objectives. To validate the efficiency of the proposed method, the PF-SOS results are compared with those from other well-known multi-objective optimization algorithms. The findings demonstrate that PF-SOS offers faster convergence and a broader range of mixture options within the same function evaluation limit.

This paper draws attention to the environmental impact of passive smart windows, a novel high-performance glazing technologies that can change their solar transmittance to control the amount of solar gain, thus reducing cooling energy demand. Despite the large influence of building envelope technologies on overall embodied carbon in buildings, the environmental impact of passive smart windows has been inadequately addressed, with a dearth of numerical data on various impact categories beyond energy consumption and Global Warming Potential (GWP). While current literature focuses on the advantages of these technologies in terms of operational energy savings, other critical environmental considerations are currently missing. This paper aims to bridge the existing gap by introducing a novel framework for evaluating the broader environmental impact of passive smart windows through a multi-category LCA method. By analysing the life cycle of these technologies, including production, usage, and disposal, the research seeks to provide a holistic understanding of their contribution to sustainability. The framework is based on systematic literature review on current state-of-art approaches and Interviews with key stakeholders in the dynamic glazing value chain. Literature review and interview results are presented, and then the framework is demonstrated through a case study of a thermochromic technologies for an office building in the Netherlands. Preliminary results show the critical areas where improvements on the methods or on the performance of the technology are required for the achievement of holistically sustainable high-performing glazing.

The technical (service) lifespan of concrete is a crucial element in the construction sector, where the quality of the concrete mix and execution technology plays a decisive role in the performance throughout the entire functional life of structures. This presentation explores the importance of a well-designed concrete mix and how it contributes to the sustainability (overall environmental impact) and longevity of structures. We will examine the influence of reducing the environmental impact of concrete, resistance to environmental exposure conditions, and maintenance needs of concrete structures. By providing insights into the relationships between mix composition and lifespan performance, we emphasize the necessity of careful material selection and precise execution technology as the foundation for sustainable construction practices. The presentation will offer practical recommendations for improving the technical lifespan and reducing the environmental impact of concrete by focusing on the quality of the concrete mix and execution technology.

The clinker in cement largely determines the environmental footprint of concrete. Therefore, concrete recycling should focus on retrieving high-quality cementitious fractions to replace clinker. This requires a shift from current traditional recycling techniques towards innovative recycling methods, enabling recovery of not only clean secondary aggregates, but also residual cementitious fines (RCF), potentially eliminating the carbon dioxide emissions associated with them. The production and upcycling of RCF offer new implementation routes that were previously deemed unfeasible. However, the properties of RCF may vary based on their origin, affecting their replacement and upcycling potential. Consequently, assessing the original concrete quality, with a focus on the binder type, before demolition is important. A handheld x-ray fluorescence technique appears promising for this purpose. To achieve effective separation of clean secondary aggregates from the original cementitious content, innovative crushing and separation techniques are needed. Additionally, electrostatic separation shows significant research potential for further optimizing RCF.

Changing outdoor conditions, i.e. higher outdoor air temperature, higher occurrence of heatwaves and outdoor air pollution, increase the risk of overheating and accumulation of air pollution in homes. Previous studies showed that high indoor air temperatures and air pollution affect occupants’ health, resulting in cardio-vascular and respiratory diseases, eyes and skin symptoms, and mortality. Measures to increase energy efficiency of renovated and newly built homes can further increase health risks during extreme weather events and can increase the outdoor temperature. Moreover, the rise of the outdoor air temperature in Europe is higher than the global average.

Therefore, understanding of the extent of current overheating and indoor air pollution and of the contributing factors is necessary to identify the required adaptability of dwellings in Europe to changing outdoor conditions. The objective of this study is to systematically review consequences of changing outdoor conditions, building characteristics, and technology on the indoor environment and occupants’ health in homes in European countries during summer.

This review focuses on empirical studies, as these enable to capture real world interactions of occupants and buildings in relation to outdoor conditions. Varying outdoor conditions, building-, and occupant-related aspects in different European climate zones are discussed. Main findings are that overheating already occurs in normal summers in temperate and northern European countries, while variation in overheating is related to occupants’ adaptative behaviour and building-related aspects. Based on the review, it is suggested to investigate adaptability of dwellings to changing occupants’ needs, new energy efficient technologies, and changing outdoor conditions.

The environmental footprint of concrete is largely influenced by the binder. It is therefore of high interest to investigate the potential reuse of the binder retrieved by modern separation techniques. However, studies found that the recycled cement fraction (RCF) still contained a certain amount of siliceous concrete aggregates, which forms an obstacle in the upcycling of RCF. In this study, the potential of electrostatic separation as a method to separate cementitious binder (hydrated and unhydrated) and sand (silica) is evaluated. Different cementitious powders and silica (sand) were prepared, resulting in a total of 9 powders and 8 mixtures. The mixtures consisted of a combination of silica and one of the cementitious powders (50/50 wt%) with a particle size of the components <125 μm. The potential of the studied technique was evaluated through charging measurements and x-ray fluorescence (XRF). Silica was assumed to contain no CaO and the detected CaO was therefore assigned to the cementitious powders. Results showed that silica and silica-rich fly ash (FA) particles became negatively charged, blast furnace slag (BFS) particles remained largely charge neutral and all other cementitious particles obtained a positive charge. Through electrostatic separation an enrichment of the cementitious binder fraction for all mixtures was obtained at the negative electrode. FA-Silica achieved the highest enrichment (89.9%), CEM III/B-Silica the lowest (4.7%) and the hydrates were enriched ranging from 28.0 to 31.8%.

Research into bioreceptive materials is gaining increased interest. However, while advances are being made on the material side of bioreceptivity, the underlying ecology of urban mosses is still underexposed. This research aimed to determine how the local environment affects the species composition of urban epilithic moss communities and assess which moss species are most suitable for the colonisation of pristine (bioreceptive) concrete surfaces, leading to recommendations for moss species selection to designers and engineers of bioreceptive structures. We conducted a field survey of 137 moss communities on concrete in the Dutch cities of Amsterdam, Rotterdam and The Hague. A total of 26 different species were found, of which the acrocarp species Tortula muralis, Grimmia pulvinata, Ptychostomum capillare, and Orthotrichum diaphanum and the pleurocarp species Brachythecium rutabulum, Hypnum cupressiforme, and Rhynchostegium confertum acted as most common pioneers and also formed a part of the climax community. We found some positive associations between acrocarp species but negative associations between acrocarp and pleurocarp species. Local environmental factors only played a small role in the community composition at a species level; however, when comparing acrocarp and pleurocarp species, the former preferred more exposed sites, whereas the latter preferred more shaded habitats. As such, we recommend that bioreceptive concrete structures use acrocarp pioneers for exposed locations and pleurocarp pioneers for more shaded locations.

Sensitivity analysis is a decisive step in experimental and numerical structural mechanics. The analysis of structural model quantifies the importance of each input parameter, potential interaction and effects on structural response. Therefore, this study aimed to help reduce the uncertainty surrounding major variables, providing valuable guidance for conducting future experiments. During the investigation, numerically deterministic sensitivity analysis based on multicriteria model evaluations of load-displacement curves representing actual behavior of the member correctly, were reviewed. Multicriteria model combined the evaluation of peak load, energy dissipation before ultimate loading, and toughness of load-displacement response. The methodology led to a strong sensitivity analysis method, generating an agreement between numerical and experimental responses. Moreover, an investigation of the method was presented for a geopolymer haunch, the numerical model was based on rigid body spring model (RBSM), which enabled precise behavior simulation of reinforced concrete structures. RBSM was refined, enabling in-depth evaluation of stress-strain contours, plasticity index, initial crack formation and crack propagation, as well as RBSM-spring failure modes. The proposed multicriteria sensitivity analysis can be implemented with other simulation methods, such as finite element analysis (FEA) and structural simulation software. The recommended method is applicable to any structural member, where laboratory-tested full-scale specimens were functioning as validation tools. Following the proposed multicriteria sensitivity analysis, experimental load-displacement curves of this study supported the results of numerical RBSM in an acceptable range of error predictions.

Given the ongoing global urbanization and the rise of heat, flooding, and drought in cities, the integration of climate adaptive measures based on “ecosystem functions and services” becomes imperative in design. This study details the implementation process of a microclimate design model in the design and retrofitting of the housing project Ecohof Noorderveer in Wormerveer, the Netherlands. The model, which quantifies local urban heat and mitigating measures through ecosystem functionalities, was incorporated into the program of requirements. The design process followed a research-by-design trajectory, involving iterative creative collaboration among all stakeholders, including future residents, the municipality, the water board, and the architect. The research employed the CFIR method to compare anticipated implementation outcomes with actual results. The findings suggest that introducing the microclimate design model into the program of requirements proved beneficial for the implementation process in the early design stage. The research-by-design approach was also deemed helpful, contingent on careful involvement of all participants in the knowledge-sharing process. This implementation method demonstrates significant potential for scaling up to standard urban development projects.

De essentie van het goed nabehandelen van beton is al vaak besproken. Nabehandeling is noodzakelijk voor beton met een lange levensduur en een mooi uiterlijk. Een CROW-onderzoek naar betonaantasting in combinatie met mosgroei was aanleiding het thema nogmaals te bestuderen. Resultaat is een nieuw studierapport van Stutech-studiegroep 68 ‘Nabehandeling’.

Implementing nature in cities has great potential to improve urban liveability by providing ecosystem services, which can help mitigate heat stress, improve air quality, attenuate noise, and reduce rainwater run-off. However, widespread adoption of urban nature and green building typologies is still limited due to their costs, environmental impact, and space constraints. Bioreceptive concrete can form the basis of a new green building typology, where the concrete mixture is adjusted to allow for biological growth, specifically mosses, to occur on its surface.

This literature review aims to give an overview of the current state of the art on bioreceptive concrete as a material in general and specifically the (potential) ecosystem services provided by the mosses growing on this bioreceptive concrete.

This review shows that bioreceptivity can be achieved in concrete in several ways, including minor adjustments to standard concrete recipes. While quantitative data on the ecosystem services provided by mosses in an urban context is still limited, potential gains appear significant. The main challenges lie in the durable long-term development of mosses on the bioreceptive concrete and the valuation through quantification of the ecosystem services they provide. However, moss-receptive concrete shows promise as a new green building typology if these challenges are bridged.

Asphalt pavement consists of aggregates resulting in a waste material at end of its life. The aggregates can be reused as basic material for asphalt or cementitious binding agents. In both scenarios, the recycled aggregates should provide a good bond with the binder to achieve strength. This study focuses on reusing recycled asphalt aggregates (RAA) in mortar. The major weakness of RAA is the thin oily film originating from the asphalt residue, weakening the bond with cement. The pyrolysis method is accessed in an attempt to overcome this weakness. Three scenarios were investigated; the use of virgin aggregates (VA), RAA, and pyrolysis recycled asphalt aggregate (PRAA) as constituent in mortar. All variables were set a constant except for the aggregate type, the VA mortar function as controlling element. This research is methodologically based on experimental data conducted in the laboratory, while aggregate samples were taken from the field. To analyze the influence of pyrolysis to the aggregate-to-cement bond behaviour, qualitative and quantitative data were collected. The quantitative data were the mechanical properties, the mortar tensile, and compression strength. The qualitative data were obtained from scanning electron microscope readings to visually observe the aggregate surface roughness and voids, including the aggregates cross-section and pre-existing micro-cracks in the aggregate-to-cement interface. Supporting data were the aggregates‘ abrasion rate and absorption. The RAA resulted in a significant mortar strength decrease. This conclusion was supported by the findings of pre-existing cracks in the interfacial transition zone. The pyrolysis method improved the compression strength but negligibly affected the tensile behavior. The compression and tensile strength increased as a function of time for both RAA and PRAA, and a strength convergence was reached at 28 days. The PRAA is considered an option for reuse in mortar, supporting nature conservation.

Kansen in de circulaire economie zijn er voor beton volop. Hoewel de winst het grootste is door hergebruik van gebouwen of constructies is het bekendste voorbeeld nog altijd het hergebruik van betonpuin als granulaat in nieuw beton. Maar dat laatste levert lang niet altijd een reductie op van de CO₂-uitstoot. Door nieuwe recyclingmethoden kunnen de kwaliteit en vervangingspercentage van het granulaat echter flink worden verhoogd en ontstaan meer kansen met betrekking tot CO₂-reductie.

The urban heat island, is a serious threat for the urban well-being, and can be determined by the local energy balance. The surface energy balance, with respect to incoming radiative energy and subsequent partitioning into reflected energy (albedo), absorbed energy and further partitioning of latter into convectional heat (QH), radiative heat (QR) and latent heat (QE) by using commonly applied urban materials and vegetation types, was therefore experimentally quantified in this study. In agreement with previous studies it was found that materials convert most of absorbed energy into convectional heat (>92%) while vegetation channels a substantial part of absorbed radiative energy into latent heat (27–50%). It is for the first time experimentally demonstrated that significant differences in thermal behaviour between different types of urban vegetation surfaces occur. Of the investigated vegetation types ivy and moss showed respectively the highest (0.10) and lowest (0.07) albedo, but sedum and moss channelled respectively lowest (27%) and highest (50%) percentage of the absorbed radiative energy into latent heat production. Of the four investigated plant types, moss appeared most effective in preventing UHI, converting only 50% of incoming radiative energy into convectional heat, while sedum was least effective converting 73% of incoming radiative energy into convectional heat. These quantitative measurements show that strategic use of specific types of urban vegetation surfaces, instead of commonly applied building materials, can be an effective measure for mitigation of UHI leading to improved climate resilient cities.