The overconsumption and depletion of raw materials have increased pressure on the EU and the Netherlands to adopt policies aimed at achieving a fully circular economy by 2050. This transition has increased the demand for material reuse, and consequently the need for retrofitting technologies. End-of-life (EoL) steel elements experience damage that new elements do not, such as corrosion, cross-sectional loss, and fatigue cracking at riveted connections. The potential for lifetime extension of EoL structural steel elements through cold spray additive manufacturing (CSAM), particularly in bridges with riveted connections, was investigated using finite element modelling in ABAQUS.

First, the composite behaviour of an S235 steel substrate retrofitted with annealed 316L CSAM powder was studied, followed by an investigation into the effects of full bonding and no bonding between the two materials. The parametric analysis showed that structural performance is governed by the mechanical properties of the substrate, the retrofit volume, and the bonding quality at the interface. Retrofitted cracked specimens exhibited a 935% increase in allowable uniaxial load before fast fracture. However, ductile damage simulations revealed that mismatched material strengths can lead to premature debonding when loading is applied perpendicular to the interface, even when full shear interaction is assumed.

A life cycle assessment demonstrated that, due to the additional maintenance requirements of CSAM-retrofitted elements, replacing a fatigue-damaged steel connection with recycled steel is the most favourable solution. When rivets are used, the global warming potential (GWP) is lowest at 6.72 kg CO₂, without compromising structural stability. The CSAM-retrofitted connection only achieves the lowest CO₂ emissions (1.35 kg CO₂) when reusable bolts are used instead of rivets. Regardless of the bolt type, several assumptions must be validated or challenged before CSAM can be considered a structurally reliable solution.

The growing demand for sustainable construction materials has prompted interest in reusing dredged sediments as an alternative to traditional raw materials in dike construction. Before they can be reused, sediments must undergo the lengthy ripening process, during which they are transformed into stable soil. Accelerating this transformation could significantly improve the feasibility of sediment reuse. This study investigates whether biochar amendment can enhance the biophysicochemical ripening of dredged sediments, focusing on the influence of biochar application rate and particle size.

Dredged material from the port of Hamburg, Germany, that was dewatered and processed at the METHA plant, was mixed with biochar produced by Bio Energy Netherlands from the gasification of wood waste at 800-1000°C for 90-120 minutes. The mixtures contained biochar with varying application rates (2%, 4%, 6%) and particle sizes (<2 mm, 2-5 mm, >5 mm). Over the course of 15 weeks of field ripening, the sediment-biochar mixtures were exposed to natural weather conditions and turned weekly. Biochar amendment introduced additional porosity which increased water holding capacity by 33-72% compared to the control after 15 weeks of ripening, resulting in values of 24-72% DW. The oven-dried COLE, ranged from of 2.2 to 5.4% which represents a decrease of up to 54% relative to the unamended sediments. This improvement can be attributed to the non-plastic behavior of biochar and explains the decreasing shrinkage observed with an increasing application rate. Increasing particle size was correlated to decreasing shrinkage (p <0.05) which could be due to the interrupting effect of coarse biochar particles on tensile load propagation in the rods. A qualitative assessment of the structure development of the experimental variants suggests an acceleration of structure formation with higher biochar application rate and larger particle size when combined with weekly turning. This resulted in a faster breakdown of the dense and platy METHA material into smaller and more aerated aggregates. Overall, the physical ripening of the dredged material was improved with the addition of biochar at increasing application rates and particle size, which promoted a faster stabilization of sediment aggregates and enhanced physical properties beneficial for construction applications.

The occurrence of sulfur oxidation, the main chemical ripening reaction, was evidenced by a loss in the total sulfur content of samples and an increasing electrical conductivity during dry periods. The pH was expected to decrease as a result of the release of protons from this reaction, however this was not observed. Instead, increasing biochar application rates was correlated to a higher pH (p <0.05) and was evidence of the material's buffering capacity which can be attributed to its high functional group and mineral content. The total sulfur content reduced on average by 5% and 22% in the amended samples and the control, and this smaller decrease compared to the control could be explained either by a slower chemical ripening in amended sediments or by measurement limitations. Furthermore, the evolution of electrical conductivity over the 15 weeks of field ripening evidenced the accumulation of chemical reaction products in dry periods.

The influence of biochar on sediment physical and chemical properties, including the increased pore structure, water holding capacity, aeration and buffering capacity, all contributed to creating conditions favorable to microbial activity. A priming effect of biochar application could be observed in the first six weeks of ripening, with high respiration rates, high decomposition rates, and decreasing stabilization of organic matter. In this period, total organic carbon content decreased on average by 30\% in amended samples, compared to only 6% in the control. At the same time, nitrogen content decreased on average by 13% in the samples with biochar, further confirming the high microbial activity. This was followed by a period of decreasing microbial activity until the end of the experiment, which was marked by 14-32% lower respiratory carbon release of the amended samples compared to the control, decreasing decomposition rates and increasing stabilization of organic matter. Thus, biochar application accelerated the decomposition of labile carbon and enhanced the biological stabilization of organic matter in sediments.

These findings suggest that biochar amendment can significantly improve sediment ripening processes and can result in a material with properties desirable for dike construction.

Magnetic Density Separation (MDS) is a novel method for the separation of shredded complex wastes [7, 8]. It uses a magnetically induced density gradient in a ferrofluid, which allows particles with different densities to follow different trajectories. Small variations in feeding direction, spread, and velocity can significantly affect the quality and purity of the separation. The MDS-based machine (MDX) studied in this research was developed by the Technical University of Delft and Myne Circular Metals B.V. After research on magnet configurations [9], fluid stabilization [10], fluid dynamics [11, 12], and the particle sliding phenomenon [8]. This thesis investigates how feeder geometry, vibration parameters, and material properties influence feeding performance and how this affects the separation. A Discrete Element Method (DEM) model was developed to simulate the behaviour of shredded copper cable feed as it is fed to the MDX by a vibratory feeder. The feed was modelled as a mixture of copper, aluminium, PVC, and PP/PE, represented by superquadric particles. Material properties and interaction properties were calibrated using literature and a Bulk Calibration Approach (BCA). A Design of Experiment (DoE), including a Definitive Screening Design (DSD), was used to calibrate sliding friction and restitution coefficients for all interaction parameters against three Key Performance Indicators (KPIs): discharge time, heap height, and angle of repose. The best-performing parameter set used a sliding friction of 0.8 and a restitution of 0.1, uniformly applied across all material types. The DEM simulations were validated against experimental tests, showing good agreement in mass flow but some deviation in feeding profiles. This calibrated DEM model was then used to test 20 feeder design variations across six base concepts, including straight and arced ends, varied feeder angles, the addition of particle-guiding walls, and different feeding bed interaction parameters. Feeding performance was quantified using four output parameters: horizontal and vertical insertion velocity, horizontal spread (modelled as a Gumbel distribution), and mass throughput. These were selected based on their known influence on separation purity in MDX. The results showed that higher vibration frequencies increased both feeding speed and particle spread. Arced feeder ends tended to increase forward particle velocity and spread, especially at larger radii, while the straight-ended design minimised these effects. The addition of a guiding wall helped reduce horizontal spread without sacrificing throughput. Ultimately, the best concept uses a straight end with a guiding wall to achieve low particle speeds and a narrow horizontal spread, with a throughput of 0.5 kg/s.

In the coming decades, Rijkswaterstaat faces the challenge of replacing and renovating a large number of Dutch highway bridges built in the 1950’s and 1960’s. These structures must be renewed in a sustainable, cost-efficient manner while minimizing traffic disruption. The objective is to retain the existing substructure and replace only the superstructure of the bridges, which are in need of replacement. This study investigates the competitiveness of weathering steel concrete composite bridges in the Netherlands, for small-span bridges (15–30 m). Hereby the following bridge variants will be considered for determining the competitiveness:

Variant 1: Existing full reinforced concrete superstructure
Variant 2: conventional painted steel–concrete composite superstructure
Variant 3 : weathering steel–concrete composite superstructure

The research is structured into four phases: (1) a literature review on material behavior, corrosion performance, and durability of unpainted weathering steel under Dutch environmental conditions; (2) structural verification using a real bridge case study to assess Eurocode compliance; (3) a sustainability assessment using Life Cycle Assessment (LCA) and Environmental Cost Indicator (MKI) values for life-cycle stages A1–A5; and (4) an economic evaluation of construction, maintenance, and lifecycle costs.
The literature review highlighted that weathering steel offers substantial maintenance and sustainability advantages but faces environmental constraints in the Netherlands due to high humidity (≥76%) and frequent de-icing salt exposure. The standard Dutch vertical clearance of approximately 4.5 m is below the 6.1 m recommended in international guidelines (ASTM and ECCS) to prevent chloride spray contamination. Effective use of weathering steel thus requires sacrificial thicknesses, optimized detailing, and preventive maintenance to ensure long-term durability. Mechanically, weathering steel behaves comparably to conventional painted steel.
Structural verifications confirmed that variant 2 and variant 3 satisfy Eurocode requirements for bending moment, shear force, and deflection, considering different configurations of the superstructure. Accounting for a 1 mm sacrificial thickness in weathering steel reduces bending moment resistance by 3.5–6%, a small but measurable effect.
The sustainability assessment showed that Variant 3 achieved the lowest environmental impact for A1–A5 stages. The use of low-carbon XCarb® steel reduced total MKI by 50–55% compared to conventional NMD steel in Variant 2, and the elimination of paint provided an additional ~9% reduction. Variant 2 performed better than Variant 1, but worse than Variant 3, while Variant 1 (full concrete) had the highest MKI.
Life-cycle cost analysis indicated up to 30% savings over 100 years for Variant 3 compared to variant 2, mainly due to reduced maintenance and minimized traffic disruptions. Structural mass comparisons showed that Variants 2 and 3 are 53–56% lighter than Variant 1, reducing loads on existing abutments and facilitating replacement while preserving substructures.
Overall, weathering steel–concrete composite bridges are technically feasible, sustainable advantageous, and economically competitive for small-span superstructure replacement in the Netherlands. These findings support the potential of integrating weathering steel into Rijkswaterstaat’s sustainable bridge renewal strategy, offering a robust pathway toward low-maintenance, low-impact, and long-lasting infrastructure.

 Rising global temperatures, combined with increasingly dense urban environments, raise concerns regarding outdoor thermal comfort and indoor liveability. As cities become warmer, both energy demand and health risks increase, urging the need for effective climate adaptation strategies. This thesis investigates how different green interventions affect outdoor and indoor temperatures in the Netherlands, and how these measures influence building cooling loads during heatwaves. Green interventions used in this study are trees, green roofs, green walls, shrubs, and grass. Within 10 m of the buildings, green is implemented to represent realistic opportunities for greening in private gardens and immediate surroundings. As a result, the simulated cooling effects reflect local-scale interventions rather than district-wide greening strategies. The Dutch heatwave from 23–27 August 2019 served as a reference event to assess three representative Dutch building typologies: low-rise, mid-rise, and high-rise.

A one-way coupled approach between an urban climate model (UCM) and a building energy model (BEM) is applied. For both the UCM and BEM, different model options were considered and compared. The selected models were then further evaluated against findings from literature to assess their suitability and accuracy. The outdoor microclimate was simulated with the ENVI-met model, which provides detailed outputs of air temperature, wind speed, and Physiological Equivalent Temperature (PET) at pedestrian height (1.5 m). Indoor thermal conditions and cooling energy demand were then evaluated using the building energy model IES-VE, with the microclimatic outputs from ENVI-met serving as boundary conditions. This coupling provides a more realistic estimation of the benefits of green infrastructure compared to building energy modelling that relies on standardised weather data.

The results show that the coupled ENVI-met–IES-VE framework successfully reproduced outdoor and indoor temperature reductions within the range reported in the literature, though typically at the lower end. This is expected, as the relatively small amount of greenery applied was intentionally chosen to isolate and quantify the local effect of greening around buildings. Among all interventions, trees produced the strongest cooling effect due to their shading capacity and evapotranspiration, with the largest impact observed when trees were combined with other types of greenery. Across all typologies, reductions of up to 1.17 °C in average outdoor air temperature, 3.92 °C in local maximum air temperature, and 13.45 °C in maximum PET were observed. Indoors, green interventions reduced peak air temperatures by up to 1.20 °C and cooling loads by as much as 32%. The relative effectiveness differed across building typologies: low-rise dwellings benefited most due to their closer interaction with the modified microclimate, whereas high-rise buildings showed more limited improvements.

This thesis provides a coupled UCM–BEM framework applicable to multiple Dutch building typologies, offering new insights into the role of vegetation in a temperate maritime climate. The modelling approach can be used to test different greening scenarios across building typologies. Future research should validate this framework with on-site measurements to further improve accuracy. Furthermore, combinations with shading devices and adaptive occupant behaviour should be explored in future research. The insights gained can guide municipalities, urban planners, and property owners in designing greener, more comfortable, and energy-efficient urban environments.

Urbanization has significantly altered the built environment, leading to increased urban heat and the loss of green spaces, which are being replaced by buildings, which in its turn retain more heat inside the city. Climate change causes extremer weather, resulting in heavier rainfall and urban floodings, for which cities are often unprepared. Incorporation of nature into the vertical buildings surfaces has the potential to address these challenges. A promising solution for creating these vertical green areas are porous concrete façades. Although research into this application has been performed for several years, a widespread implementation remains limited. A demountable, quick-to-install solution could assist the broader implementation of green solutions in urban areas. This research investigates the feasibility of such a demountable system.

The issue of climate change has become highly important over the last decades. All sectors need to find solutions in order to reduce the carbon footprint and the built environment sector is definitely not an exception to this. One of the solutions is to use more biobased materials, such as timber. The use in timber is not only limited to low-rise buildings, more mid- and high-rise buildings are being built as well. The number of buildings including timber with at least six stories was increased from 32 in 2015 to 115 in 2023.

Even though the number of timber buildings is increasing, the actual environmental impact is largely unknown. This is because there is no commonly-used method to calculate the carbon footprint of a building which is complete and correct. Currently, the MPG (MilieuPrestatie Gebouwen) and the method described in the Paris Proof Agreement are mainly used in the Netherlands. The MPG uses the Environmental Product Declarations (EPDs) from the database from the NMD viewer, but this viewer does not provide the essential information for the user to choose the proper EPD. The Paris Proof Agreement disregards the end-of-life phases, which leads to incomplete results. Therefore, another method was developed to calculate the carbon footprint and to determine the difference in carbon footprint between a concrete and/or steel structure with a timber-hybrid structure. This method uses two sets of phases: phases A-C and phases A1-A5. The former uses all relevant LCA phases and will provide the most accurate results, while the latter can be used to compare the results to the Paris Proof Agreement limits. Phases A4 and C2 (transport to and from the building site) and modified to fit the current projects.

Two case studies were used for this research. The first case study is KasseNova aan de Vaart, a seven-story residential building made of concrete. The carbon footprint is calculated for this concrete design, as well as three design variants including CLT floors, CLT walls and a combination of the two. The second case study is Apollolaan 171, a six-storey office building made of steel and concrete. The design variants include glulam columns, CLT floors and beams and a combination. For all variants, design calculations of the timber elements were performed. For CLT elements, two end-of-life scenarios were considered: 100% recycling and 100% incineration. The current design of KasseNova aan de Vaart has a carbon footprint of 3,145 ton CO2-eq. when phases A-C are considered. In the scenario that the floors and walls are replaced by CLT, the carbon footprint is decreased by 63.1% when the CLT is recycled, while this is decrease is 12.7% when the CLT is incinerated. When phases A1-A5 are considered, the current design has a carbon footprint of 222.46 kg CO2-eq./m² (above the 2021 Paris Proof limit of 220 kg/m2) and the CLT floor and wall design variant has a carbon footprint of 35.12 kg CO2-eq./m² (below the 2050 limit of 50 kg/m2), including biogenic carbon uptake. The current design of Apollolaan 171 has a carbon footprint of 1,671 ton CO2-eq. (phases A-C). For the scenario in which the floors, beams and columns are replaced by CLT and glulam, the carbon footprint is reduced by 89.2% (CLT recycled) and 49.8% (CLT incinerated). Considering phases A1-A5, the carbon footprint of the current structure is 255.17 kg CO2-eq./m2 (above the 2021 limit of 250 kg/m²), while the carbon footprint of the structure including CLT and glulam elements is -44.93 kg CO2-eq./m² (below the 2050 of 50 kg/m²).

These results show that an increase in timber in the structure leads to a reduction in carbon footprint. This is because timber takes up carbon in the product stage. However, the amount of reduction depends on several factors. If the CLT is recycled at the end of its lifetime, the reduction will be more significant than if the CLT is incinerated. When the structure includes concrete, the carbon footprint depends on the type of cement being used in the concrete. CEM I will lead to a higher carbon footprint than CEM III. For structures including steel, a higher percentage of recycled steel leads to a lower carbon footprint. Also, in general, the country of production influences the carbon footprint. If a country has a high percentage of coal in its energy mix, the carbon footprint will be higher.

Transitioning towards a more circular construction industry is crucial for achieving climate-neutral and fully circular operations by 2030. One significant contribution to this goal is fully utilising the reuse potential of prefabricated inverted T-girders. The primary challenge lies in adapting the inverted T-girder system to enhance the circularity of the girders. To address this, a comprehensive literature review is conducted to understand the structural response and disassembly challenges associated with the system, providing valuable insights into potential improvements. This study employs a numerical model based on the Finite Element Method using DIANA FEA to assess the impact of various design adjustments, specifically the removal of end transverse diaphragms and increasing deck slab thickness. The numerical model uses horizontal and vertical curved shell elements and is subjected to several critical load cases to determine the maximum stresses for different design parameters. The results indicate that eliminating the end transverse diaphragms has minimal impact on the distribution of longitudinal bending moments and shear forces. However, it causes a localised increase in support forces by 17\%. Additionally, significant differences are observed in the deck slab, necessitating an additional capacity of 16\% for transverse bending moments and 17\% for twisting moments. The study also examines the effect of skew angles to evaluate the applicability of orthogonal system findings to skewed systems. As the skew angle decreases, a greater proportion of forces and moments is absorbed by the deck slab rather than the composite girders. However, the mutual differences between systems with and without end transverse diaphragms generally vary by up to 2.6\%, indicating that the findings for the orthogonal system are broadly applicable to skewed systems as well.

The construction industry is a major contributor to waste generation, with construction and demolition waste (CDW) constituting a significant portion of it. This research is centered on developing a technology to separate and recycle two types of plastics, EPS and PU, from cement matrices, along with recycling the cement itself. The goal is to recover high-quality materials for reuse within the construction sector, thereby promoting sustainable practices and enhancing the circularity of construction materials.
The research involved two classes of samples: samples containing cement and PU foam (Class
A) and samples containing cement and EPS foam beads (Class B). Different separation methodologies were employed for each class.
Class A samples underwent mechanical crushing and sieving, followed by electrostatic separation using a vertical triboelectrostatic separator.
Class B samples were successfully separated using mechanical milling and sieving.
The separated PU foam, due to a reduction in particle size during separation, could not be directly reused as insulation. Therefore, it was analyzed using Fourier-transform infrared spectroscopy (FTIR) to assess its quality for recycling into new polyurethane foam products. The FTIR results confirmed the effectiveness of the separation process, yielding clean polymer suitable for reintroduction into the market as a secondary raw material, particularly for particles smaller than 500 μm.
The separated EPS foam beads were reused to cast new insulating cement, and its thermal conductivity was tested. The results demonstrated that the separation process did not compromise the insulation properties of the EPS beads, allowing for their reuse in their original application.
The recycling potential of the separated cement powder was also analyzed. Chemical composition analysis, particle size distribution, and loss on ignition tests indicated its suitability for reuse as a partial cement replacement in new mortar samples. Mechanical tests on mortar samples with varying percentages of recycled cement powder (15% and 30%) and different reactivation temperatures (650°C and 750°C) showed a slight decrease in compressive and flexural strength compared to the reference mortar, particularly for the 650°C reactivation temperature. However, the recycled cement powder reactivated at 750°C and used at a 15% replacement ratio resulted in a 2.75% increase in compressive strength, highlighting the potential for optimizing the recycling process to achieve comparable or even enhanced performance in construction applications.

To limit the need for clinker in cement, CEM III/B is being used more and more in infrastructure. This cement mixture uses significantly less clinker, but instead uses blast furnace slag. Since this is a waste product of the steel industry, CEM III is supposedly much more sustainable than CEM I. However, its mechanical properties are different as well. There has been plenty of research comparing the mechanical properties of CEM I and CEM III concretes, and CEM III concrete seems better in many ways. However, for these experiments only perfect curing conditions had been used. The conditions on the building site are often far from perfect, and affect the integrity of the concrete.

This research has compared the mechanical properties of CEM I 42.5N and CEM III/B 42.5N concrete mixtures in a relative humidity of 55%, which is a realistic value for the building site. This low humidity has a major effect on the hydration, which also affects all mechanical properties. With the help of an experimental campaign, these mechanical properties were tested.

To conclude the findings of this research, it can be stated that sub-optimal curing conditions affect CEM III significantly more than CEM I. Not only are the mechanical
properties lower, but there is a higher uncertainty in the CEM III mechanical properties as well. Applying CEM III in sub-optimal conditions would require extra careful
considerations in the treatment. In the given building site conditions, applying CEM I
would be significantly more durable, cheaper, and especially safer.

Concrete is the second most used material in the world after water and recent trends show no slowing down of the concrete use around the world. Concrete is also a huge contributor to CO2 emissions as it makes up 8% of emissions. This study investigates the optimization of concrete structures to reduce environmental impact while maintaining structural integrity and cost-effectiveness, e.g. how to make a concrete structure more sustainable. A previous report where quay wall designs of different materials were compared in regard to the CO2-emissions and life cycle assessment found that a concrete quay wall had 43% more emissions than a steel quay wall. The goal of this study is to reduce the overall CO2 equivalent emissions related to a concrete structure by 50% and make the design more sustainable.
A concrete ship lock chamber as part of the Delta21 project is used as a case study. To measure the positive effect of sustainability two chambers are designed; a base case chamber designed based on what is most commonly done in practice in the structural engineering field, and an alternative chamber design with the aim of making the concrete lock chamber more sustainable. A partial life cycle assessment (LCA) is performed on both of the two design alternatives. The optimization of the alternative chamber design focused on minimizing global warming potential (GWP) by adjusting the reinforcement-to-concrete ratio and incorporating structural elements such as plated steel anchors. The two alternatives are analysed comparably as they are designed under the exact same conditions, in the same environment and with the same functionality aspects.
The base case structure is a U-basin concrete chamber with tapered walls. The alternative optimised structure enhances the structural behaviour of the chamber wall by adding anchors. This reduces the moments by 88% and the shear force by 56% compared to the base case design. By changing the structural wall type in the chamber by adding anchors, the concrete volume could be reduced by 47% between the base case design and the optimised design. This also allows for a reduction of concrete strength class, reinforcement volume, underwater concrete floor thickness and the number of tension piles for the construction pit. The LCA reveals a 55% reduction in the GWP for the alternative concrete chamber design, compared to the base case design. An optimum reinforcement ratio for the alternative concrete chamber anchored wall of 2.3% is identified, resulting in a balance between structural performance and environmental sustainability without increasing material costs. This ratio doesn’t incorporate labour cost which might affect this optimum ratio by lowering it. This demonstrates the potential for achieving environmentally responsible solutions without compromising the structural integrity of a structure or incurring additional costs.
The study highlights the potential for integrating sustainability objectives into concrete structure design, with recommendations for further research including exploring alternative materials and advanced optimization techniques.

To align with the objective of the European Green Deal [46] policy of achieving net-zero greenhouse gas emissions by 2050, the construction sector must transition to a circular built environment. Most of the waste in the Netherlands is related to construction and demolition waste, with the industry accounting for approximately 35% of CO₂ emissions [89]. The goal of the circular built environment is to minimise waste by reducing, reusing, recycling, and recovering materials throughout the life cycle of a product [66]. Therefore, making an impact in the construction industry can lead to a significant reduction in CO₂ emissions and contribute to the achievement of the European Green Deal [46].

This research contributes to the "reuse" component of the aforementioned circular built environment goals. Specifically, the focus is on developing a reusable connection between hollow core slabs and steel frames by implementing increased execution tolerances. Increased tolerances are necessary to allow reuse, as alignment-related problems often occur. The research consists of several parts: the design process, structural verification, experimental research on demountability, and environmental impact assessment. The design process comprises a tolerance analysis supported by a Monte Carlo simulation, variant studies, and a comprehensive qualitative trade-off analysis. After the best scoring alternative is determined, the verification part assesses the structural behaviour of the connection in terms of strength and stiffness. This is done using a combination of analytical and numerical calculations. The purpose of the experimental research is to investigate the demountability potential of the reusable connection. The final part of the research investigates the impact of the reusable connection compared to conventional connections for different lifecycle scenarios.

The research demonstrated that incorporating additional tolerances in the connection between the hollow core slab and steel frame is crucial to achieve a reusable construction. Three connection alternatives were generated that can incorporate these tolerances based on a literature review and meetings with experts in the field of building construction. The alternatives were weighted on tolerance inclusion, ease of installation, demountability potential, and costs. The best option was identified as a connection consisting of a square hollow section and a bolted shear stud encased in mortar. This alternative outperformed competitors in terms of tolerances, installation, and costs. However, the demountability potential was identified as a critical part of the connection and, therefore, was further investigated experimentally. The experiments showed an increased demountability potential in situations that include pre-treatment. Vaseline-treated specimens showed no signs of chemical bonding and better lubrication compared to oil-treated specimens, resulting in the lowest resistance and, therefore, the best demountability. The last step of the research investigated the environmental impact of the reusable connection and compared it with the conventional construction technique. Results showed that a marginal addition of 1.3% to the initial environmental impact of the superstructure results in a significant reduction over the full lifespan of the structural elements. This was attributed to the reusability of the connection and the ability to reuse structural elements in another building in a second life cycle.

From the results, it is concluded that a reusable and structurally feasible connection between hollow core slabs and integrated steel beams can be created with a small additional investment upfront, resulting in a substantially reduced environmental impact. The purpose of this study is to provide guidance and persuade decision makers, such as project developers, building owners, and government organisations, to consider implementing reusable construction methods in their real estate projects. By doing so, they can contribute to the objective of the European Green Deal [46] policies and the goal of achieving net-zero greenhouse gas emissions by 2050.

The building industry is the largest global contributor to carbon emissions. At the current rate of carbon emissions within this sector, the targets set by the Paris Agreement will not be achieved. Consequently, significant reductions in carbon emissions from the building industry are needed to align with global climate goals.

When discussing the carbon emission of a building two major type of carbon emissions can be distinguished: 1)operational 2)embodied. Operational carbon is all the CO_2 that is emitted during the use of the building and refers to the energy-related carbon emissions. Embodied carbon is all the CO_2 that was emitted to realize the construction of the building.

Historically, sustainable building design has focused on reducing operational carbon. However, as improvement in low-energy buildings continue to decrease operational emissions, the significance of Embodied Carbon has grown. Despite this, Embodied Carbon remains underrepresented in the design process, often addressed reactively at the end of the design, leading to unnecessarily high levels. Embodied Carbon must be integrated in the early design stages to create buildings with a low Embodied Carbon content, improving the sustainability of the building industry.

This master thesis introduces a parametric framework designed to embed Embodied Carbon assessment into the early building design process. Recognizing the uncertainties inherent in early design phases the framework prioritizes delivering ranges of values rather than precise figures, befitting of the dynamic and flexible nature of design exploration. By offering quick, clear results and transparent methodologies, the framework stimulates a multidisciplinary workflows, enabling accessible, efficient, and informed decision-making without requiring specialized expertise.

The framework consists of three tools; 1)Structure Generator Tool: Translates design parameters into structural systems and material quantities without requiring specialized engineering knowledge. 2)Embodied Carbon Material Factor Determination Tool: Converts material quantities into Embodied Carbon values using databases, with the flexibility to include or exclude biogenic carbon storage. 3)Iterator and Data Evaluation Tool: Supports iterative design exploration, comparing design alternatives and facilitating clear visualization and communication of results through tools like DesignExplorer.

The developed framework effectively supports the early design stage by providing actionable insights, enabling designers to quantify the impact of their choices with ease and efficiency. By integrating multidisciplinary variables, default settings, and automated element generation, the framework stimulates a multidisciplinary collaboration without requiring, but allowing the application of, specialist expertise. A range-based approach accounts for uncertainties in Environmental Product Declaration (EPD) selection, while sensitivity analyses helps distinguish robust conclusions from those sensitive to design changes and allowing the converging of the carbon assessment throughout the design process. Although future refinements,such as improved connection design and substructure integration, could enhance accuracy, the framework already delivers reliable estimates for Embodied Carbon assessment. Comparisons of databases show slightly conservative results for the Dutch building industry when using ICE V3.0 instead of NMD. Overall, the framework lays a strong foundation for integrating Embodied Carbon considerations into early design, proving its potential to significantly reduce carbon emissions in building practices.

The pressing challenges of climate change and the increasing surplus of concrete waste is making it increasingly important to fully recycle concrete in a sustainable way. Since cement is by far the component that contributes most to the environmental footprint of concrete, it is of great importance to investigate the potential of upcycling secondary cementitious materials. Modern recycling techniques such as the Smart Liberator make it possible to efficiently separate the coarse and fine fractions in concrete waste. It also makes is possible to produce a fine powder fraction that shows potential to replace primary cement, which helps to mitigate CO2 emissions. This study explores to which extent recycled concrete fines (RCF), obtained from advanced recycling technologies such as the Smart Liberator, can replace ordinary Portland cement (OPC) in mortar mixtures. It is assumed that the RCF consist mostly of cementitious materials. The aim of this study is to assess the performance of RCF when replacing OPC in different mortar mixtures. Several treatment methods were applied to enhance the reactivity of the RCF.
To be able to assess the performance of the RCF as replacement of ordinary Portland cement at mortar level, three reference mortar mixtures, made from CEM I, CEM II/B-V and CEM III/B, were prepared for comparison. Portland cement with strength class 52.5 R was used in for preparation of the reference mixtures. The used RCF were the 0-63 μm fraction obtained from the Smart Liberator. It is expected that the RCF are from CEM III origin based on documentation from the company Rutte Groep. However, due to limited stock, some of the mortar mixtures had to be prepared with a different type of RCF, consisting of RCF with a CEM I and CEM III origin that were mixed in a 1:1 ratio. The OPC in the reference mixtures was replaced with RCF at 50%, 75% and 100% ratios.
Grinding, carbonation, conventional heating and flash calcination were applied as treatments to enhance the reactivity of the RCF. Thermogravimetric analyses were used to assess the effects of the treatments on the decomposition of the compounds of the RCF. Mortar prisms made with treated and untreated RCF were tested for flexural and compressive strength after 28 days of curing, and their performance was compared to the reference mortars.
The results showed that the untreated RCF performed best when used in combination with blast furnace slag. This combination was the only one in which a 100% replacement resulted in measurable strengths and the measured strengths at the other replacement ratios were the highest, reaching up to 70% of the compressive strength of the reference prisms at 50% replacement. This indicates that the RCF are a suitable activator for blast furnace slag.
The effects of the treatments differed in the different mixtures and also varied across the replacement ratios. Grinding of the RCF improved their performance at the 50% and 75% replacement ratios in the CEM I variant, while their performance in the CEM II and CEM III variants was similar to or lower than the untreated RCF. The same conclusions are drawn from the results after carbonation. Heating of the RCF up to 900 °C for 30 minutes in a regular chamber furnace resulted in better results for the CEM I variants at all replacement ratios, while no significant improvements were measured for the CEM II variants. For the CEM III variants, only the 75% replacement ratio had a significant improvement. Lastly, flash calcination resulted in the most significant improvements for the CEM I and CEM II variants at all replacement ratios. For the CEM III variants, flash calcination significantly improved the strengths at the 100% and 75% replacement ratio, but not at the 50% replacement ratio. Since this does not align with each other, it is necessary to reconfirm these results.
As a conclusion, this study demonstrated that untreated RCF shows potential to BFS, while flash calcination is the most promising treatment for boosting RCF reactivity across most mixtures. Conventional heating also showed potential, especially for CEM I. However, grinding and carbonation had mixed results, with limited benefits for BFS combinations due to carbonation effects. Future research should confirm these findings and explore ways to optimize the treatment methods.

S. Alveolata is a tube-dwelling polychaete which can be found all the way from the coast of Norway all the way down to Dakhla in the Western Sahara. It is able to build large reefs structures from sand filtered from the water column. It is known to have importance for biodiversity from animals feeding on the animal to its reefs providing a safe haven for fish. At the same time, a move is happening to using habitat protection and recreation for coastal protection. Several soft habitats such as mangroves, saltmarshes and seagrasses have been studied for their wave damping potential and S. Alveolata holds promise in this aspect. Given these functions, the S. Alveolata biogenic reefs need to be protected from outside influences, but little is known about their (mechanical) behaviour. As such, this study investigates the reef structure, erodibility, compressive and shear strengths of these reef materials and compares these to the commonly encountered loads from walking humans and wave loading. The static load from a person can reach up to 150 kPa while loading from 1.8 m waves can exert 36 kPa.  In agreement with Fournier-Sowinski (2013) and Vovelle (1965) but in contrast to Sanfilippo et al. (2019), the structure of the reefs to consist of three-layered tubes, with an organic sheath which partly contains a layer of flat grains placed next to each other on the inside and a scale-like layer of generally flat grains. These grains are glued together with proteinaceous glue spots showing a particular, bubbly structure. New is the description of bubbles radiating from the center of the glue spots. The grain size distribution shows a bi- or trimodal distribution, which has not been described before. S. Alveolata favours flat grains (in contrast to (Gruet & Bodeur, 1994; Lisco et al., 2020)) of about 1.0 mm size to build their reefs, which is a larger grain size than previously found (Gruet & Bodeur, 1994; Lisco et al., 2020; Naylor & Viles, 2000). As previously observed (Gruet, 1972), the reefs are made up of many tubes curving upward from a solid substrate. However, the first 3D mCT-scans of a whole reef block show enough voids so that small tubes wind their way through the reefs, probably made by juvenile worms. The grain size and mCT data suggest that tubes are reconstructed during the year.  The mechanical properties of these reefs show a very high compressibility with total strains between 10-20% under loads of 604 kPa. The reefs show a yield stress varying from 80-185 kPa. This is about the same stress as a person exerts while standing, the dynamic loads of walking are much higher but the limited time these loads are applied means little damage is done. Even though these yield stresses are far exceeded during testing, the samples hold some amount of cohesion due to interlocking and some unbroken bonds. Loose tubes weather from all sides at the same rate during slake durability tests. Shear box testing was conducted in a stepped manner with four loading steps from 48-380 kPa normal pressure, such that the first two steps are below yield stress at 48 and 96 kPa normal load. These show that the reefs have a cohesion of at least 23 kPa and a friction angle of 21.3°, explaining their resistance to waves. During testing, the reef samples compress strongly with their void ratios decreasing from 1.01 to 0.85. As a result of shearing, the internal tube structure of the sample was strongly deformed and shear bands or planes were formed during shearing. Some voids are also opened up in this process. After shearing samples show an apparent cohesion due deformed tube parts in which some bonds remain intact interlocking with each other. Compared to other cemented sands the S. Alveolata reefs exhibit many of the same features as these sands, such as the applicability of the Mohr-Coulomb criteria and high compressibility. However, unlike other cemented sands their open, tubular structure showed lower friction angles due to the alignment of sand particles in the linings. Also, the S. Alveolata lack the filling of void spaces often found on cemented sands leading to compressive behaviour.  Compared to the pressures to which the reefs are subjected in nature, the reef materials probably hold up well. The results provide a basis for more detailed investigation and testing and highlight key behavioural aspects of the material. It shows the response of the material to mechanical stresses and provides a starting point for using these reefs or solutions inspired upon them in different ways.

The challenge of global warming is an increasing concern of the 21st century. The concept of sustainability is therefore considered of high importance. A major problem of the Dutch government is the growing housing demand. Also after the WWII, the Netherlands faced a housing crisis, resulting in about 847,000 council houses. The massive number of flats combined with the aforementioned deficiency of houses and the climate problem prohibit large scale demolition and reconstruction, as this would lead to both a further short-term deficit of houses and emission of greenhouse gasses. A timber top-up on council estates constitutes a sustainable approach, which accounts for densification and the huge building stock in city centres. Therefore, this research is aimed to develop a method to optimize timber top-up designs for council estates, considering structural limits and environmental impact.

It is found that the building period impacts the structural variety in council estates. Hence unfortunately no universal structural lay-out can be defined. Based on a norm comparison, two flowcharts are produced to predict the overcapacity of distinct council estates. A modular cross laminated timber (CLT) unit and a non-modular timber frame extension (Dutch: houtskeletbouw) are considered. Material minimalization formed the decisive criterion to determine the most effective variant. Therefore, a 3-step method is developed, which considers the flat characteristics, structural overcapacity and minimalization of material use.

To conclude, it is generally not possible to tell a priori which of the two considered timber top-up methods is the most effective for a particular case. Further, it can be concluded that timber top-ups form a sustainable replacement for combined demolition and reconstruction of buildings. Moreover, these facilitate the realization of a substantial number of houses. Therefore, a vertical extension of council estates forms a sustainable solution to the current housing demand in the Netherlands.

The urban heat island effect is a well-known and pressing problem in cities today related to urbanisation. It is the phenomenon of an increased ambient air temperature in cities compared to the surrounding rural areas. The use of nature-based solutions has been proposed as a way to help solve this problem. These interventions use nature and biodiversity to improve urban sustainability. By replacing materials that accumulate a lot of heat, the urban heat island effect is tackled. One way of doing this is by making use of so-called bioreceptive concrete on our facades, which allows for the biological growth of mosses to take place on the concrete substrate itself, without requiring any additional systems or maintenance.
This master thesis aimed to quantify the evaporative cooling effect of these moss-covered concrete facades on the urban environment. The research objective was to measure and model the amount of cooling resulting from the evapotranspiration of moss, by analysing water uptake and release, as well as the temperature decrease of a façade surface as a result of evaporation.
Laboratory experiments were conducted to examine the evaporation rates of various moss species under controlled ambient conditions. Bryum capillare displayed the highest water uptake, water retention, and drying time, with the ability to take up 32.4 g of water per 83 x 83 mm surface area. This is equivalent to 4703 g of water per square meter or 470 kg/m3 volumetric weight. Pleurocarpous mosses showed a range of 27 to 27.4 g of water uptake, corresponding to 3919 to 3977 g of water per square meter or 392 to 398 kg/m3. The concrete itself absorbed 21.1 g of water, which is equal to 3063 g of water per square meter or 204 kg/m3 for the 15 mm thick sample that was tested.
Evaporation rates were found to be higher immediately after a watering event, with variability observed between different moss species. Highest variability was 5.56 g/h for Eurhynchium striatum versus 1.86 g/h for Syntrichia ruralis. However, after a certain time, most mosses exhibited similar evaporation rates. The exception was Bryum capillare, which consistently maintained a higher evaporation rate. This moss, growing in cushion form, demonstrated enhanced drought avoidance due to a reduced surface-to-volume ratio and additional capillary spaces for water retention. The highest levels of evaporation were observed in all moss species under conditions of high temperature (25°C) and low relative humidity (50% RH).
Field testing involved monitoring the temperature of two bioreceptive concrete façade panels, one covered in moss and the other left bare. On sunny days, when panel temperatures exceeded 15 to 20 °C, and the panels were dry, the moss panel temperature was 0 to 5 °C lower compared to the bare concrete panel. This temperature difference was attributed to the lower albedo of the moss (0.07 – 0.11) compared to the concrete (0.10 – 0.40). The moss absorbs more solar radiation and prevents it from reaching the surface beneath it. Infrared camera measurements confirmed that the dry moss surface temperature was about 2 to 3 °C warmer than the concrete panel surface due to lower albedo of the moss. On rainy or cloudy days minimal temperature differences were observed between the panels. Additionally, the moss acts as an insulation layer, trapping the air between its leaves, keeping the material behind it cooler. The potential implications of this additional insulation layer on top of the facade remain to be investigated. Based on its specific heat capacity and heat conductivity, it could help with heat gain in winter and cooling gain in summer. It is hypothesised that moss has a lower thermal mass than concrete, potentially facilitating quicker heat dissipation at night and contributing to reduced building surface temperatures.
Watering the panels significantly reduced surface temperatures, with the moss panel being 2 to 5 °C cooler than the concrete panel when wet. The moss exhibited higher water absorption and longer water retention compared to the porous concrete, enabling more evaporation resulting in lower façade temperatures. This cooling effect persisted for approximately two and a half hours after a 40 ml watering event, equivalent to a 1 mm rain event at low wind speeds. These findings indicate that applying moss on a concrete facade cools the surface temperature of a façade compared to a bare concrete façade.
A non-stationary model based on the energy balance of the facade system was calibrated using field testing data. This model provides accurate temperature profiles under different weather conditions. Evaporation modelling was calibrated using water events but could be improved by implementing a water balance. By computing the irrigation, precipitation, evaporation, throughflow and runoff in a dynamic balance, the evaporation and temperature profiles would become more accurate.
The model is used to simulate a heat wave and the thermal behaviour of the façade after rain events with different intensities. A 1 mm rain event decreases the surface temperature of the façade with a few degrees but the effect does not last for a very long time. A 10 mm rain event decreases concrete surface temperature up to 10 °C initially, and the effect lasts for a few hours. The length and intensity of cooling can be extended through the application of moss on a façade. Then, for a 10 mm rain event, the initial temperature reduction is equal to 15 °C. To increase this effect, the pore volume of the concrete could be increased. Also, a moss species should be cultivated on the concrete which grows in cushion form, is desiccation tolerant, and has natural protection against UV light.
The thesis concludes that applying bioreceptive concrete on facades has the potential to mitigate the urban heat island effect by maintaining cooler temperatures for an extended time following rain events depending on their severity. This approach replaces materials that accumulate and radiate excessive heat. To quantify the effect of bioreceptive concrete as a mitigation strategy more accurately, a computational fluid dynamics (CFD) model could be made to predict the ambient temperature decrease of the air in front of a bioreceptive facade.
By investigating and quantifying the evaporative cooling effect of moss-covered concrete facades, this thesis contributes to the understanding of nature-based solutions. The findings highlight the potential benefits of incorporating bioreceptive concrete in building facades to mitigate the urban heat island effect and improve thermal comfort in urban areas.

Rijkswaterstaat aims to build circularly from 2030 onward, with the purpose of having a fully circular economy by 2050. Therefore, the aim of this study is to design a reusable modular superstructure, with a small span, which can replace an existing so-called volstortligger superstructure. This is a structure that Dura Vermeer often uses and it regularly happens that these constructions are demolished after a lifespan of, for example, 10 years. This is a waste of materials and therefore an alternative will be investigated in this research. The following research question guides this study:

What is the optimal structure, in terms of shadow costs, mass and financial costs, for a modular superstructure?

In order to answer this question, a parametric study is performed using the software Grasshopper, using the Finite Element Model plug-in Karamba3D. In this way, quick structural analyses were performed, to explore multiple options. In total, more than 11.000 bridge design variants have been generated, divided over 12 different runs. The model allowed targeted optimization of shadow costs, weight and financial costs. Optimization is achieved by varying the following input parameters: number of steel girders, steel profile girders, outrigger deck, concrete deck thickness, concrete class, outrigger deck, FRP sandwich panel height, facing thickness, web thickness, and fibre volume.

In total, 6 different variants would be developed in this way, 3 with a concrete deck and 3 with an FRP deck. However, the optimization results in only 4 different variants, 3 with a concrete deck and just one with an FRP deck. The results show that the variant with the FRP deck is indicative for Shadow costs, Financial costs and weight.

After the four pre-designs had been developed, these variants were weighed against each other by means of a Trade-Off Matrix (TOM). Using this method, a distinction is made between the variants based on the pre-chosen performance indicators. All performance indicators have a weighting that adds up to a total of 100.

This study concludes that it can be advantageous to replace the traditional design with a demountable design, with the assumed boundary conditions of this study. All developed variants have an advantage with regard to environmental impact and financial costs compared to the traditional design, assuming a lifespan of 100 years in which it is moved 10 times.

Equalized involvement of stakeholders in decision-making processes (DMP) allows them to achieve a balanced outcome, when aiming to create value for each participant. However, as the number of stakeholders increases, traditional methods of interactive engagement become more complex, often leading to unbalanced solutions. Identifying such balanced outcomes also becomes more challenging and time-consuming, considering the wide range of potential outcomes. To address this complexity, this thesis introduces a new approach, Preference-based Goal Attainment (PBGA), and develops a tool for its application in DMPs. The PBGA tool facilitates transparent communication of stakeholders' needs, desires, and values within the DMP, helping to bridge satisfaction gaps among various stakeholders and yield an equitable and optimal outcome.

For the development of this tool, a multi-objective optimization framework is proposed. This framework allows stakeholders to integrate their needs, desires, and values as objective functions, with decision parameters represented as variables, in the tool. Crucially, it enables stakeholders to specify preferred states within their objectives, known as preferences. The framework also considers the varying influence of stakeholders by incorporating a weighted goal attainment method. This method focuses on improving the objective with the largest weighted preference deficit in each iteration of the genetic algorithms used in the optimization process.

For testing and validation, the approach is applied to a DMP in a selected case study. Data, including objectives, variables, and stakeholder preferences, are collected through semi-structured interviews, and transformed into a computational format for MATLAB® implementation. The outcomes are verified using the Kolmogorov-Smirnov and Chi-Square comparative methods. Additionally, the tool and its results are validated by stakeholders, ensuring the tool's practicality and acceptance of the new design.

With the PBGA tool, stakeholders can transparently communicate their needs and desires in the DMP and achieve an outcome that involves equal participation from each stakeholder. The thesis concludes with a comprehensive discussion on the practical applications, limitations, and assumptions of the tool, highlighting its potential to improve stakeholder collaboration and decision-making in project management.

This research addresses the environmental impact of foundations in lightweight housing units, focusing on BAM's timber house concept, FLOW. While the engineered timber superstructure is environmentally conscious, the foundation's contribution is often overlooked. The study aims to minimise the Environmental Cost Indicator (ECI) of FLOW houses by investigating three foundation variants through a Life Cycle Assessment (LCA). The LCA compares three foundation variants: prestressed prefab concrete piles, timber foundation piles with concrete caps, and shallow concrete strip foundations, considering soil profiles in Zwolle and Delft. Results show that the timber foundation has the lowest ECI, driven by CO2 storage in the spruce timber part. Sustainable options, such as Blast Furnace Slag cement, a reduced concrete strength, and optimised processes, significantly reduce ECIs. Timber foundation piles with concrete caps emerge as the most environmentally promising. Further technical implications and feasibility research are recommended for integrating timber foundations into lightweight structures like FLOW.