The increasing demand for sustainable and high-rise buildings has led to the development of hybrid concrete-timber structures. These buildings incorporate a concrete core and columns for stability, combined with timber and concrete floor systems, providing an opportunity to balance sustainability, structural efficiency, and cost-effectiveness. While this approach presents opportunities, it also introduces several challenges related to structural dynamics, fire safety, environmental impact, and construction costs.

A key issue in concrete-timber hybrid buildings is their lower weight due to timber floors that are lighter than concrete floors, which makes them more susceptible to wind-induced vibrations. Additionally, the irregular mass distribution caused by alternating timber and concrete floors over the height of the building influences the dynamic response of the building. From an environmental perspective, timber is often regarded as a sustainable material due to its carbon storage capability. However, the extent to which hybrid systems reduce overall carbon emissions compared to concrete buildings remains uncertain. Furthermore, construction costs are closely tied to structural and environmental performance, impacting the feasibility of such buildings.

Despite growing interest in hybrid concrete-timber high-rises, existing research lacks an integrated approach that examines the relationships between dynamic behavior, environmental impact, and construction cost. Although individual aspects have been studied, the correlation between these design factors remains unclear. Additionally, the influence of parameters such as building height, floor type, and concrete-timber distribution on these design aspects has not been extensively explored.

This research aims to support the integral design of hybrid concrete-timber high-rises by offering a structured approach to evaluating key design choices and their implications. The findings contribute to a more holistic approach to hybrid building design, supporting designers, policymakers, and researchers in optimizing hybrid systems.

This thesis explores the influence of key building parameters on the design aspects of tall concrete-timber buildings during the early design phase. The goal is to identify relationships between dynamic behavior, environmental performance, and building cost by analyzing various building variants. The studied parameters include building height, floor plan, floor type, and the percentage of concrete floors. To achieve this, three hypotheses are formulated that connect the design aspects with the percentage of concrete floors. By analyzing different percentage of concrete in the floor systems, the study aims to provide insights into the complex interactions between these aspects.

The methodology consists of three parts. First, building variants are designed based on predefined parameters, using structural calculations for floor systems, concrete cores, and foundations. Second, models are developed to determine the dependent variables: dynamic behavior (first natural frequency), environmental performance (Environmental Cost Index through Life Cycle Assessment), and construction cost. Based on the results of the models relationships between independent and dependent variables are analyzed to identify trends and interactions. Finally, correlations between the three design aspects are examined to provide insights into their interdependencies.

The results indicate that building height is the most significant factor influencing dynamic behavior, environmental performance, and construction cost. This is evident from the distinct scatter plots for each building height. The ECI value for buildings between 70 and 90m ranges from 12 to 28 €/m², while for buildings of 110m, it ranges from 20 to 33 €/m². Construction costs for buildings between 70 and 90m range from 735 to 875 €/m², and between 850 and 1000 €/m² for buildings of 110m. By analyzing the results, no significant correlation between construction cost and other parameters was found, as the effect ranges of the parameters are similar. Moreover, the dynamic behavior of the buildings remains within safe limits. Additionally, variations in foundation piles and core dimensions significantly impact the environmental cost index (ECI) and construction cost, making their inclusion essential for accurate comparisons. Finally, the model effectively analyzes specific parameters, thereby providing clear insights into their influence on design aspects.

The construction sector aims to reduce its environmental footprint to address climate change and material depletion, with an increasing focus on reducing embodied carbon. Simultaneously, there is a growing demand for affordable housing in the Netherlands. A significant part of the new housing stock needs to be mid-rise residential, efficient in both material and land use. Bio-based materials, such as timber, which are renewable and have relatively low carbon emissions, could play a key role in reducing embodied carbon for these types of buildings. Since structural systems often account for the majority of a building’s embodied carbon, using timber here can offer significant advantages. However, its application in practice remains relatively uncommon in the Netherlands.

Although existing research highlights the potential of timber in structural systems, challenges such as limited knowledge, lack of incentive and financial barriers are often cited as key reasons for its limited adoption. This research aims to address these challenges by exploring and quantifying to what extent a shift toward timber-based structural systems can reduce the environmental footprint of mid-rise residential buildings in the Netherlands, while maintaining economic feasibility. By doing so, this research aims to offer practical insights into the use of timber in construction, addressing knowledge gaps and identifying the conditions for its application in practice.

A comprehensive literature review was conducted on environmental regulations, assessment methods, structural systems, and suitable compositions of structural elements using timber. The insights gathered were applied to a case study, where various redesigns were developed and optimised under different boundary conditions. The environmental impact was quantified by a life cycle assessment using the Paris Proof Indicator (PPI, measured in GWP-GHG). Simultaneously, economic feasibility was quantified by an evaluation of construction costs. The scope of the assessments is limited to the life cycle stages from cradle to practical completion, emphasising the importance of direct impact.

As a result of the assessment of the case-study redesigns, several building concepts provided significant reductions in environmental footprint while being economically feasible. Compared to the original design, hybrid redesign concepts with calcium silicate brick walls and CLT-concrete composite floors can achieve PPI reductions up to 42% while being of equal or lower costs. Concepts with CLT walls and hollow core timber floors can even lead to reductions of PPI up to 55%. Within a 10% increase in costs, a wider range of concepts can lead to similar PPI reductions. All concepts with both CLT walls and CLT floors proved to be economically unfeasible within the stated cost thresholds.

The associated PPI values were found within the range of 82 and 114 kg CO2-eq./m², depending on the building concept. Accounting for design variations between mid-rise residential buildings, research uncertainties, and potential design optimisations, the building concepts researched could align with the Paris Agreement targets up to 2035. As the targets for 2050 are roughly twice as strict, it is unlikely that these are achievable within the researched design strategies. Incorporating reused or recycled materials and/or accounting for the benefits of temporary carbon storage in bio-based materials will likely be necessary to achieve these targets.

To achieve sustainability goals, the Dutch government is striving toward a circular economy, which necessitates changes in the building and construction sector—responsible for 34% of global carbon dioxide emissions in 2022. Steel production contributes significantly, accounting for 7.2% of global greenhouse gas emissions. Reuse, a key strategy within the circular economy, holds great potential but remains underutilized in infrastructure projects. This research investigates the feasibility and environmental impact of reusing a Rijkswaterstaat bridge, addressing the central question: What are the feasibility and environmental implications of reusing the Keizersveerbrug, a steel truss bridge, on an object-level basis, as assessed through a comprehensive case study design process?

A donor structure file, following the technical guideline NTA 8713 for the reuse of steel elements, is developed to assess the feasibility of reusing the Keizersveerbrug. A visual inspection confirms that the bridge is in good condition, with minimal corrosion and damage. The truss bridge aligns well with the design criteria of the new application, allowing for multiple feasible design options for both the approach ramps and the main span. An evaluation based on environmental impact, user comfort, and integration into the surroundings leads to a preliminary design. This design incorporates three 100-meter truss bridge elements from the donor structure, with adaptations including a new deck and a fresh paint layer.

An environmental impact assessment, conducted using Environmental Product Declarations and in accordance with NEN-EN 15804+A2, demonstrates significant environmental cost savings. When considering all life cycle stages, a reduction of 0–66% is observed, while excluding life cycle stage D results in a 25–60% reduction compared to variants constructed from other materials. Additionally, this research adapts the traditional design cycle to integrate reuse considerations, providing a structured approach for engineers addressing the challenges of reusing steel bridges. These findings underscore the potential of reuse to contribute to sustainable infrastructure that aligns with the principles of a circular economy.

Urbanization has led to environmental challenges such as the Urban Heat Island effect and the reduction of green spaces, resulting in lower carbon dioxide absorption, increased air pollution, and higher noise levels. Incorporating vegetation into buildings through vertical or horizontal greening systems can address these issues. However, these systems face challenges like high irrigation costs, artificial substrates, low integration, and short lifespans compared to building infrastructure. Bioreceptive materials offer a promising alternative by allowing greenery to grow directly on the material, bypassing these limitations. This research focuses on enhancing the bioreceptivity of concrete while evaluating its sustainability performance and structural integrity in terms of compressive strength (CS), and freeze-thaw resistance (FT).

The type of concrete being evaluated is porous concrete, designed to include a growing substrate for hosting plants. A multi-criteria analysis is used to determine the optimal concrete mix, considering three design criteria: bioreceptivity, sustainability, and structural integrity (including compressive strength and freeze-thaw resistance). Three mix designs are developed: a reference mix with Ordinary Portland Cement (OPC) and limestone aggregates, and two mixes using a low-carbon Calcined Clay (C$^3$) binder—one with lava stone (Mix 1) and the other with recycled concrete aggregates (Mix 2). An iterative process is employed to adjust the binder and water content, evaluating workability, compressive strength after 5 days, and interconnected porosity. Once suitable proportions are achieved, the concrete samples are tested for their mechanical, bioreceptive, and sustainable properties. The incorporation of the substrate has also been tested, addressing a gap in the existing literature.

The compressive strength after 28 days was comparatively low for all tested mix designs due to high porosity, with achieved values as follows: Mix 1 (2.5 MPa), Mix 2 (3 MPa), and the reference mix (10 MPa). A decrease in compressive strength was observed when incorporating the growing substrate and after drying. Despite low compressive strength, all samples demonstrated resilience in freeze-thaw resistance, withstanding 28 FT cycles with low mass loss. However, Mix 1 and Mix 2 showed loosening of aggregates when pressed by hand after the standard testing process, indicating a need for further testing of CS after different FT cycles.

Various methods of substrate incorporation were evaluated, showing that the substrate did not penetrate the concrete pores but remained on the surface of the cubes. This did not negatively affect the bioreceptivity for plant growth. The volume of substrate incorporated per sample and mix design varied due to manual application and the surface connectivity of the aggregates for each concrete product. This variability in substrate volume affected the water absorption and retention results, suggesting that these outcomes do not consistently characterize the mix design but rather are variable. However, Mix 1 and Mix 2 exhibited high water absorption rates when considering the concrete product itself (Mix 1 = 164.4 g/L, Mix 2 = 134.1 g/L, Ref mix = 82.4 g/L). Lastly, leaching of elements from the concrete layer occurred, leading to an increase in the pH of the incorporated growing substrate. All samples showed germination after one month of testing, with Mix 1 displaying the highest average germination rate and dry biomass. However, Mix 2 and the reference mix exhibited high variance in plant growth results, likely due to varying outdoor conditions such as moisture and temperature. Further testing is recommended to better isolate the impact of these outdoor conditions, which could have contributed to the high variance in plant growth outcomes.

Finally, in terms of sustainability performance, Mix 1 and Mix 2 positively impact the environmental burden of the concrete product by reducing the ECI and CO$_2$ emissions by an average of 50\% per 1m$^3$ of concrete, considering LCA stages A1-A3. At the same time, the use of C$^3$ binder reduces the ECI and CO$_2$ emissions from the binder material extraction stage by 60\% compared to OPC binder, further demonstrating that this binder is a low-carbon alternative.

This research demonstrates that the tested mix designs, evaluated for bioreceptivity, sustainability, and structural integrity (in terms of compressive strength and freeze-thaw resistance), have great potential for use in vertical greening systems with Mix 1 identified as the most optimal concrete mix design. This finding is significant for urban environments, especially as urbanization is expected to increase in the coming years. Bioreceptive vertical greening systems made with sustainable materials can address environmental challenges in cities and align with the Sustainable Development Goals.

The rapid development of infrastructure has led to various environmental, economic, and societal challenges. The pavement industry, in particular, is known for its high energy consumption, resource utilization, and pollution generation. Despite recent efforts to augment the sustainability and circularity of pavement infrastructure, there remains a lack of comprehensive assessment methods to evaluate the existing practices and technological advancements, which makes the implementation of innovations challenging. This study reviewed twelve existing circular economy indicators and frameworks to understand the challenges associated with their use in evaluating pavement infrastructure. The indicators included Material Circularity Indicator (MCI), Circular Economy Index (CEI), CB’23 framework, Environmental Sustainability and Circularity Indicator (ESCi), Circular Economy Indicator Prototype (CEIP), Material Reutilization Score (MRS), Value-based Resource Efficiency (VRE), Circular Economy Performance Indicator (CPI), Recyclability Benefit Rate (RBR), Reuse Potential Indicator (RPI), Product-level Circularity Metric (PLCM), and Building Circularity Indicator (BCI). These indicators cover different aspects of circularity and sustainability, such as resource efficiency, material circularity, product’s lifetime, preservation of product’s functions, and environmental and economic impacts. However, none of the indicators provide a comprehensive assessment tailored for pavements, encompassing circularity and all three aspects of sustainability. Considering factors such as data availability, overlap of conceptual and methodological approach, and the scope covered, six of the twelve circularity indicators were evaluated in this study, namely, MCI, CEI, CB’23, ESCi, CEIP, and MRS. Since these indicators were not originally developed to assess pavements, appropriate methodological modifications were proposed and validated using three different pavement construction and maintenance methods that are commonly adopted in the Netherlands. In order to map the road to sustainability, the analysis was complemented with the Environmental Cost Indicator (ECI, or in Dutch, MKI) and Net Present Value (NPV). The three case studies adopted in this study included: (a) resurfacing the pavement once in every 12 years with 25% Reclaimed Asphalt Pavement (RAP), hereafter referred as Business As Usual (BAU) scenario, (b) life-extension maintenance by rejuvenating the pavement in years 5 and 10 since construction followed by resurfacing, and (c) use of low-emission technology, i.e., Warm-Mix Asphalt (WMA) with higher RAP 3 percentage (50% by mass) in the mix. An analysis period of 36 years was chosen as per the Federal Highway Administration guidelines and the foreground data was collected from roadway stakeholders. Additional missing information was also gathered from Dutch asphalt product category rule, international databases, and existing literature. The results revealed the strengths and limitations of each indicator. MCI being a mass- based indicator captured the material circularity and product’s service life but failed to represent the environmental and economic impacts. Although CEI indirectly captures the environmental impacts as it is governed by market prices, which takes into consideration the societal and environmental taxes, it is volatile as it is can also be influenced by the supply and demand of raw materials and material quality, potentially overlooking the benefits of using higher percentages of recycled materials. CB’23 provides detailed information by classifying pavement components across different circular economy principles, which aids in targeted improvements but complicates the comparison of alternatives as a whole. ESCi combines MCI and MKI to incorporate circularity and environmental sustainability but requires extensive modelling and lacks economic and social considerations. CEIP, as a questionnaire-based indicator, covers a wide range of circularity principles, but the weighting and scoring of questions is subjective as it is based on the expert opinion leading to concerns of bias in decision making. MRS involves simplified mathematical computations, thereby serving as an attractive choice for quick decision-making. However, it is fundamentally biased to cover only the recycling strategy, and ignores the aspect of lifecycle use, thereby not accounting for durability of the asset. With regards to the case studies, MKI, MCI, ESCi, and MRS indicate that the WMA alternative was the most circular strategy. LCCA, CEI, and CEIP favour the rejuvenation alternative, while CB’23 may favour one alternative when the result of one sub-indicator is designated to be the criterion for decision making. However, since all the indicators cover different aspects of circularity, it is important to complement the results with environmental, economic, and social sustainability indicators for comprehensive and robust assessments. In practice, choosing different alternatives based on the selected indicators can lead to varying end result. Therefore, it is essential to handle these implications carefully and the scope, boundaries, methods, assumptions and any limitations must be clearly stated for transparent decision-making. Future research should focus on improving data quality and developing methods to integrate social sustainability, wherever feasible.

Reusing construction materials has become increasingly significant in the context of the Netherlands’s goal to achieve a fully circular economy by 2050. This thesis provides a guideline for the reuse of masonry, emphasising the transition from traditional demolition methods into techniques that facilitate the reuse of masonry elements. The research explores the development of masonry, current practices, and future perspectives, highlighting the environmental gain and durability proceedings.

Masonry, a cornerstone of Dutch residential construction, offers significant potential for reuse due to its durability and historical prevalence. Despite innovations like drystacking and prefabrication, traditional masonry remains dominant. This study underlines the urgency of enhancing masonry reuse in light of the projected increase in new housing construction and subsequent demolitions. The research identifies a gap in the reuse methods of masonry, proposing an approach of cutting out panels from exiting walls for incorporation into new projects.

The thesis begins with a historical overview of masonry and its separate elements, mortar and brick. It traces its development from Roman times to the present. Early masonry in the Netherlands saw the use of tuff stone and brick, evolving through various phases influenced by technological advancements and changes in construction methods. The introduction of cavity walls, the development of different brick bonds, and the use of various mortars are detailed, highlighting the transition from masonry as a structural element to its current role as a (decorative) façade.

Innovations in masonry construction are examined, focussing on drystacking, robotics, and prefabrication. Drystacking allows erecting masonry facades without mortar, facilitating easy disassembly and reuse. While promising, Robotics in masonry construction face challenges in widespread adoption due to the complexity and precision required. Prefabrication, though historically significant, remains underutilised in modern construction.

The thesis analyses the current stock of buildings in the Netherlands, emphasising the potential of masonry reuse. It discusses the materials flow, highlighting the substantial use of bricks and concrete in new construction. The research outlines the demolition trends, noting that older buildings, particularly those from the post-war period, are prime candidates for material recovery.

A significant portion of the thesis is dedicated to the practical aspects of masonry reuse. It describes the process of removing masonry elements, including desk research, visual inspection, and destructive tests. Techniques for sawing, hoisting and transporting masonry panels are discussed, providing a step-by-step guide for practitioners. The study also addresses storage and implementation, emphasising the need for proper handling to maintain the integrity of the reused material.

Durability is a critical concern in masonry reuse. The thesis evaluates structural and climate durability, assessing the properties of masonry elements under various conditions. It explores the impact of frost/thaw cycles, improper joint application, and strategies on the longevity of reused masonry. The research employs DIANA modelling to simulate the structural behaviour of masonry panels, providing insight into their performance during non-conventional boundary conditions of lifting the element from the existing structure.

The environmental impact of masonry reuse is quantified through a life cycle assessment (LCA). The study compares the environmental burdens of reused masonry elements with traditional buildings and reusing masonry bricks. It highlights significant reductions in CO2 emissions and total MKI value in both comparisons.

The thesis concludes with practical recommendations in the form of a guideline, encouraging a shift towards more sustainable building practices. The research emphasises the importance of quality control and standardisation in reusing, ensuring that reused material meets current regulations and performance standards.

By addressing the technical, environmental, and practical aspects of masonry reuse, this thesis contributes to the broader discourse on sustainable construction. It provides a valuable framework to enhance masonry reuse, aligning with the Netherlands' ambition for a circular economy. The guideline presented in this thesis research aims to facilitate the adoption of masonry reuse practices, promoting environmental conservation and resource efficiency in the construction sector.

Vertical Greenery Systems (VGS) show numerous advantages in terms of sustainability and a healthy living environment. Unfortunately it is found that current knowledge on the fire safety of these systems is lacking and can pose as a barrier for implementing the systems or can cause situations in which they are implemented which are unsafe. The current research aims to put a step forward into filling this knowledge gap. By literature research, interviews with different parties and a risk analysis on case-studies relevant parameters influencing the fire safety of VGS have been identified. A tool was developed which can analyse a façade design with VGS on its fire safety risks. The tool was tested on case-studies and evaluated by interviewees. The tool is to guide designers and raise awareness and understanding of what parameters in a design influence the risk. By raising the understanding on the topic of fire safety of designers, better informed and safer decisions can be made. During the research numerous mitigating measures have been found which can be used in a design to minimize the risk of using VGS. It was found that the type and amount of materials used in the system are of great influence of its fire safety performance, more so than the vegetation used. Furthermore the location of where on the façade the system is applied is of great impact on the risk the VGS causes. Concerns about fire safety of VGS are valid but there are plenty solutions and design considerations identified which help minimize the risks. A risk analysis tool can be helpful for designers to determine the fire risks of a design, increasing the understanding and awareness on the topic which empowers designers to make safe designs with VGS, thus enabling the safely greening of the building envelope.

Urbanisation has increased the worlds' cities populations and influenced the living conditions within these cities. Temperatures rise, the air becomes more polluted and noise levels increase. It has been proven that types of vegetation such as plants and trees can reduce the negative effects of urbanisation by for instance cooling cities, filtering the air or damping out noise. Due to the limited space in urban areas, placing vegetation on building façades and roofs can be a practical solution to gain the benefits of natural elements without the need for large pieces of land. A total of seven benefits provided by greenery systems can be distinguished which were researched intensively, however it is unknown how these benefits compare to the downsides of adding extra loads to a structure, which come in the form of extra material use and lead to an increased environmental impact for the building. In this research these benefits and downsides were compared to determine whether the application of greenery systems actually makes the building more sustainable or not. In this research the effect of six horizontal greenery systems (also known as green roofs) and eight vertical greenery systems (also known as green façades) on the sustainability of the building was assessed.
The effects of the benefits of the greenery systems on the sustainability of the building were determined using three different certification methods: BREEAM, LEED and WELL. In these certification methods credits related to one of the seven benefits can award the building a preset number of points, thereby increasing the overall amount of points awarded to the building. The impact of extra material use was determined using the environmental cost indicator (ECI), after determining the needed element sizes. The percentage increase of the sustainability certification score and the ECI were compared to determine which of the two has a higher percentage increase. When the increase in the sustainability certification score is larger than the increase in ECI, the greenery system receives a 'positive score' meaning the building has become more sustainable. If this is the other way around, the greenery system has a 'negative score' meaning application of the greenery system has made the building less sustainable. When both are equal the system has a 'neutral score'.
This research has shown that it is currently not possible to value all aspects of greenery systems in the certification methods used. Nonetheless, greenery systems lead to an increased sustainability of a building in 52% of the tested cases. The nature roof always receives a positive score and application of a direct green façade can result in a positive or neutral score but never a negative score. These two systems can thus always be applied to a building without having a negative effect on the building's sustainability. There is potential for modification of the existing certification methods so they can score all benefits provided by the greenery systems properly, giving more insight into the impact of these greenery systems on a building's sustainability and potentially affecting the number of cases with a positive score.

The building sector is increasingly acknowledging the necessity to mitigate its environmental impact in response to the challenges posed by climate change. Adaptive facades specifically are used to develop a dynamic control of the envelope’s properties, modifying their behaviour in response to outdoor conditions and indoor stimuli. Thermochromic and photochromic technologies, also known as Passive Smart Windows (PSW) are passive solutions that aim to regulate solar gains through the integration of an Auto-Responsive (AR) layer, particularly for cooling purposes, to reduce energy consumption and minimize the operational impact of buildings.
Existing literature predominantly concentrates on the performance aspects of these technologies, mainly due to their early development stages. However, there remains a gap in assessing the overall environmental impact, both in terms of impact perspective, thus considering several possible effects
on the environment, and from a life cycle perspective, thus including both embodied and operational dimensions. The embodied impact, in particular, lacks comprehensive examination beyond considerations of Global Warming Potential (GWP). Furthermore, the dynamic landscape of materials and principles utilized in these technologies adds complexity to their evaluation.
This thesis project aims to bridge these gaps by establishing a comprehensive framework for evaluating the total impact of PSW, encompassing both embodied and operational stages. Through comparative analysis with alternative Dynamic Window Systems (DWS), comprising static windows paired with dynamic shading devices, the framework facilitates a thorough examination. Operational energy calculations are grounded in energy simulations of a standard office space with an exposed facade, while the description of the embodied stages gives an overview of the life cycle of PSW, with focus on different possibilities integrating the AR layer and their consequences.
The application of the framework in a case study reveals nuanced findings. While the GWP of PSW decreases of 1,1%, most of the other impact of PSW increase, including a growth of 0,1% of the Single Score. PSW has a lower impact compared to DWS due to the increased energy demand of the latter but, contrary to the initial expectations, the PSW does not consistently outperform static glazing due to conservative assumptions in energy simulation and a higher replacement rate, which significantly escalates embodied impact. Notably, challenges arise in defining materials for the AR layer, necessitating collaboration with manufacturers to improve data availability.
The study identifies replacement as a critical factor in determining overall impact, underscoring the importance of extending the lifespan of PSW or to consider a detachable layer to enhance its environmental sustainability. However, criticisms regarding the partial nature of the analysis emerge, particularly in neglecting user comfort and control over the facade, as well as the temporal flexibility of the technology. Future research directions should incorporate these aspects for a more comprehensive evaluation.
Ultimately, this thesis emphasizes the interdependency between the LCA approach, the energy simulation and the context of the PSW’s application. This highlights that the environmental impact assessment of such building elements can not leave the contextual application out of consideration in order to provide a sufficiently reliable result, thus limiting the use of this framework mainly to defined projects rather than to the estimation of generic impact for a PSW product.

Vertical greening systems (VGS), i.e. vegetated building facades, can harness the benefits of nature to contribute to resilient and healthy cities. A lack of guidelines for the early selection and design of VGS currently limits implementation. Based on a literature study and expert interviews, this thesis proposes a multi-criteria framework and tool to assist architects and engineers in the holistic selection of multi-purpose VGS. The research compares the performance of different system types on 18 impact criteria, ranging from urban noise reduction to installation costs. Depending on project-specific input about environmental conditions and building project objectives, the framework provides a ranking of the most suitable VGS. Design recommendations ensure a VGS that is fit for purpose. Subsequently,
sensitivity analyses, a case study and testing on sample projects validate the usability and results of the tool. The thesis extends current perspectives on evaluating the impact of VGS on the built environment. The tool enables users to make holistic and justified decisions on the application of a VGS.

This research is about the problems related to the maintenance of living wall systems. The literature review and interviews with living wall manufacturers have shown that the irrigation system is the source of many problems. The irrigation system is an essential part of a living wall system. This ensures that the plants get water and are provided with sufficient nutrients. Nowadays there are advanced irrigation systems where you can set exactly how much water is supplied and what the total water use is. However, it has been found that this does not mean that the water actually reaches every plant. Which can lead to plants getting too much or too little water. In both cases this has a negative effect on the health of the plant and can lead to maintenance of the living wall. The problem lies in the method of assessing whether the water content and water distribution of the living wall is in order. At the moment there are no reliable assessment methods for this and these inspections are based on observations. For this purpose, an answer is given to the main question "What is the best strategy for monitoring the water distribution of the irrigation system on a living wall system that ultimately leads to more effective maintenance?". To answer this question, various monitoring methods have been tested. For the monitoring methods, an NDVI camera is used to measure plant quality. Furthermore, moisture sensors and a thermal camera are used to measure the water distribution and water content. In addition to this, the run-off water is measured. The results show that the reliability of the results strongly depends on various factors such as the presence of plants and climatic factors. This report describes the correct way to carry out these methods in order to obtain reliable results. A key factor here is that the monitoring methods must be applied together so that they compensate for each other's limitation.

This research aimed to design a modern-day quay wall that can host ecologically valuable species by using pervious concrete, which offers a suitable growing layer for plants due to its high interconnected porosity. The study investigated which vascular plant species are dependent on quay wall ecosystems in the Netherlands and determined the ecological requirements that contribute to their growth. The experimental research optimized the water retention of pervious concrete by using two types of coarse aggregates and different water-to-cement ratios. The results showed that pervious concrete can be optimized by adjusting the aggregate type for a water-to-cement ratio between 0.4 and 0.6, and that the use of pumice stone enhanced the water absorption of pervious concrete by a factor of approximately 2.5. Additional testing is needed to determine if a mix design with pumice stone aggregate can fulfil the technical requirements. An inflow-outflow model is utilized to predict if the current design variant, consisting of substrate layer made of pervious concrete and soil in combination with a reservoir in the capping stone, can provide sufficient moisture to the vegetation. The findings indicate that the proposed quay wall can host ecologically valued species to a certain extent, but optimizing the design by investigating the potential of pumice stone as coarse aggregate is recommended. Furthermore, the capillary effect in the substrate layer should be investigated as sufficient rise is needed to prevent the need for a minimum form of maintenance.

The building and construction industry is one of the main polluting sectors contributing to climate change, and is responsible for around 37% of global CO2 emissions. A circular approach is needed to address the global demand for construction materials and resources in a sustainable way. Steel is a commonly used material in construction and fully recyclable. Recycled steel has to be melted in a furnace, which is a polluting process. For reuse of steel only disassembly and transport is necessary. The general shift from recycling to reusing steel can offer environmental benefits.
A number of steel bridges in the Netherlands are being renovated or replaced by Rijkswaterstaat in the coming years. Rijkswaterstaat has been investigating the reuse of its bridges on object level, i.e. reusing the complete structure. This has proven to be difficult. Disassembling the bridge and reusing the structure on an element-level has not been thoroughly investigated. As reuse of construction elements in general is relatively novel practice, not much is known about how to determine the reuse potential of structural bridge elements. This thesis aim to identify current knowledge gaps and provide research results that encourages future reuse of steel bridges. As a case study the eastern Van Brienenoord bride is investigated. This bridge is scheduled to be replaced in 2026-2028 and there currently are no plans for reuse.
The goal of this thesis is to examine the reuse potential of steel bridges on element-level, focusing on two critical factors: fatigue and corrosion. Fatigue and corrosion are two of the most deteriorating processes for steel bridges. The reuse potential can be evaluated using the remaining service life of the elements. The remaining service life based on both fatigue and corrosion can be determined by implementing the corrosion assessment in the fatigue calculation. Fatigue assessments are based on stress ranges in structural members. Corrosion leads to a reduction in the cross sectional area, increasing the stress and thus stress ranges occurring in the critical structural details.
The design, decomposition, loading history and technical condition of the eastern Van Brienenoord are analysed. After critical review of the Van Brienenoord the structural elements of the bridge deck are selected to investigate further. Inspection reports by Rijkswaterstaat and Nebest are used to locate corrosion damage on the Van Brienenoord. The corrosion damage is determined using functions for uniform surface corrosion for steel. The critical structural details of the selected elements in the bridge deck are identified. Using the fatigue assessment procedure described in the Eurocode in combination with the reduced cross section the remaining service life of the structural elements is determined.
According to the results of the proposed assessment method in this research, all structural elements of the eastern Van Brienenoord bridge deck have significant service life left and are therefore suitable for reuse after disassembly. However, certain specific details that have a higher calculated fatigue damage may need to be repaired or removed.

In the last decades, climate change is causing our environment to change rapidly, unprecedented in recent history. Civil engineering structures are dependent on the deteriorating environment they are situated in. Changes can cause an increase in loading due to, for example, extreme weather events or alter the structure’s resistance by, for instance, accelerated corrosion or an increase in the number of frost days. However, planning for such events depends significantly on the state of climate change, which is not considered in the sequential decision-making optimization for inspecting and maintaining our infrastructures.

Sequential decision-making optimization refers to the process of finding an optimal sequence of actions to be performed to keep the structure safe. Optimality often refers to the plan with the lowest costs. Traditional inspection and maintenance plans seek a solution by applying heuristic-decision rules on, for instance, time- or condition constraints and fail to find an optimal solution. During the last decade, a new method called Deep Reinforcement Learning (DRL) has been applied and proven to find an optimal strategy to beat traditional approaches. Especially the ability of DRL to find an optimal solution for partially observable environments makes it a perfect candidate for the problem at hand.

This thesis has developed a framework that incorporates partial observability over possible climate scenarios in the decision-making of engineering structures’ inspection and maintenance planning. The framework explains the steps required to translate a physical system towards a Partially Observable Markov Decision Process (POMDP), as the mathematical framework needed to seek an optimal se- quence of inspection and maintenance actions for. Then, it is explained how the POMDP can be used to find an optimal policy with a DRL algorithm, which includes benchmarking and testing the policy. A belief state has been incorporated over the climate scenarios to simulate the partial observability of the climate. Updating over the scenarios is provided by Bayesian Inference, using a climate parameter, such as temperature.

The framework has been applied to a case study in the second part of the thesis. The case study con- figures a stochastic deterioration process for different climate scenarios. An optimal policy has been found by applying Proximal Policy Optimization (PPO) with a decentralized policy for the various com- ponents. Two well-established heuristic-based maintenance policies, time-based maintenance (TBM) and condition-based maintenance (CBM) have been configured as benchmarks for the framework. The framework is compared against the benchmarks using lifecycle costs and safety as metrics. The policy provided by the framework has outperformed both benchmarks in terms of costs while maintaining the same safety. The policy beat TBM with 5% and CBM with 1% in terms of lifecycle costs. Another important distinction is that the benchmarks are optimized for the climate scenarios, while the frame- work finds this distinction without prior knowledge. It is therefore concluded that the framework can find an optimal policy under the uncertainties related to climate change. The case study, however, does not fully capture the complexity of engineering structures that the framework can catch. It is therefore recommended to use the framework for a more complex structure in the future.

Over the last few years, the construction sector has experienced increasing demand for raw materials due to the rapid growth of the urban population. At the same time, most of the post-war buildings in Europe have reached the end of their service life. As a consequence, a period of intense demolition activities with
significant waste generation is expected in the upcoming years. Both situations are eventually translated into significant environmental pressure. Concrete is the main component in construction and demolition waste (C&DW). Due to the high environmental footprint of this material, it is crucial to eliminate its consumption
through recycling and re-use. Currently, concrete rubbles are crushed with regular crushers and used mainly for low-grade applications (down-cycling) such as road foundations. Despite the environmental and financial benefits, this practice is still not at a sustainable level since raw materials are still needed for new structures, while the demand for low-quality secondary materials in the construction sector has already declined.

Two innovative recycling technologies called C2CA and Smart crushing (SC) developed recently in the Netherlands, aiming to close the material loop in the construction sector. These technologies recover most of the original concrete materials at high-quality, which can be use in the production of new concrete at
higher rates than traditionally. This research focuses on the environmental and financial implications of the novel C2CA and SC recycling systems as alternative solutions to the Traditional crushing (TC) method. The evaluation was conducted based on an integrated LCA&LCC analysis framework in which the monetised
environmental impacts (shadow costs) were internalised in the actual costs occurred within the supply chain of recycled concrete (production of primary materials, recycling, transports). On this basis, the recycling systems were compared from two different perspectives. First, the recycled materials produced were used for concrete production according to the current European standards. In this case, the traditional recycled coarse aggregates (TRCAs) were used to replace 50% of the primary gravel, while the innovative coarse (IRCAs) and fine (IRFAs) aggregates from the innovative systems replaced 100% of primary gravel and 60% of primary sand respectively. The maximum potentials of the innovative systems were investigated in a second scenario in which IRCAs and IRFAs completely replaced the primary concrete aggregates. In addition to that, the produced recycled concrete powder (RCP) was used as supplementary cementitious material (SCM) to replace 20% of the primary cement. In this study, the innovative recycling systems were considered mobile units located at the demolition site. In contrast, the TC recycling was executed off-site at a stationary plant to secure the sufficient quality of TRCAs.

The results of the integrated LCA&LCC study revealed that both C2CA and SC systems were financially better options than the traditional recycling route. Especially when the SC system was used to replace higher quantities of primary materials, the total cost was reduced by up to 19% relative to the TC method. On the other hand, the C2CA technology showed better performance when following the current standards, where about an 8% cost reduction was achieved. However, environmental improvements were reported only for maximum utilisation of the SC products, resulting in about 17% lower shadow cost than the traditional method. In the case of the C2CA system, the environmental impact was found 5% increase for both scenarios. Both innovative systems displayed overall benefits over the TC method regarding social cost (internalised environmental impacts), with the SC system exhibiting the best overall performance for maximum use of its products. In this case, the overall benefits reached almost 19%, while the rest scenarios were not higher than 5%.

The sensitivity analysis emerged that the innovative recycling systems presented benefits only when they were located close to the demolition site due to increased transportation of EoL concrete. For the same locations and up to 23 km away from the demolition site, only the SC2 scenario (maximum use of SC products) was more efficient than the traditional recycling route. The rest scenarios became more effective as the traditional plant was placed away from the demolition site. On the other hand, changes in the recycling phase, such as energy consumption and equipment operating costs, had a negligible impact on the results. Even if renewable energy sources would power the recycling plants, the environmental and cost benefits throughout the supply chain were not higher than 5% and 2.5%, respectively

Urbanization has led to the accumulation of heat in urban areas. In other words, cities demonstrate higher temperatures than surrounding rural suburbs, known as the Urban Heat Island effect (UHI). This phenomenon has substantial consequences on energy consumption for cooling purposes, air quality, and human health.
As a metropolitan city, Damascus experiences a high urban heat island effect due to many factors. The intensity of UHI in Damascus is high and could reach 10˚C. Therefore, a mitigation strategy is a necessity.
A possible solution could be integrating the Living wall system (LWS) into the built environment. However, the living wall system’s implementation is still limited due to different factors such as the high initial cost, the complexity of the system, and technical difficulties. Furthermore, the efficiency of this system in mitigating the urban heat island still needs to be further investigated.
Thus, this research focuses on analyzing the UHI effect, designing LWS for Damascus’s context, and then investigating the proposed design’s efficiency as a UHI mitigation strategy

Amsterdam city is currently facing problems of old quay walls and bridges renovation, followed by insufficient greening in the city. This study aims to propose a method to increase Amsterdam's greenery that will add social and environmental value through the renovation work of quay walls. The main objective is investigating how the quay walls can be redesigned to gain improved moss colonization as the primary greening method. The research question is: “How can quay wall elements be designed with improved bio receptivity to stimulate high moss growth coverage that will add social and environmental values to Amsterdam citizens’ wellbeing?”. It is further divided into six sub-questions to gain knowledge of bio receptive definitions and concepts first, followed by the study of bio receptive construction materials properties in the second part. The third part aims to gain fundamental moss knowledge. Afterward, a moss field survey is conducted on construction materials in The Netherlands as the fourth part. The fifth part consists of the moss cultivation technique and experiment to gain more practical knowledge of the construction materials. Finally, with the acquired results, a bio receptive quay wall design with other practical considerations is proposed in the last part. Initiated with fundamental literature research on existing bio colonization works, followed by more specific building materials properties and moss knowledge studies on the first three parts. Afterward, a simple field survey on twelve sites has been conducted to determine moss growth conditions on building materials related to quay walls. Later on, an indoor moss cultivation method through the use of terrarium has been done to gain insights into material properties, ideal growing condition for mosses and moss cultivation technique. Based on the acquired knowledge, a simple quay walls element is redesigned to promote moss growth, keeping the site orientation in mind and moss cultivation practicalities. The first three parts' results will not be described since these are basic definitions and knowledge needed for the following three parts. During the field survey, the importance of moisture for moss growth on building materials is crucial. Therefore, not one specific material property value margin is needed, but a set of material properties and environmental conditions should be satisfied to gain successful moss growth. The duration of direct sunlight exposure will influence the site's moisture condition, which will further affect moss growth. Only twelve moss species were found and identified that are able to grow on construction materials, which is used for the moss cultivation method on the construction materials during the experiments. The use of a terrarium to test moss growth on construction materials followed by a moss cultivation idea gained interesting moss growth results. It turns out that the mosses' growing temperature should be below 25 degrees Celsius at all times, especially during the germination phase, followed by a humidity level above 80 percent. For this reason, significant moss growth results on the terrarium test samples are only gained during the end of the fall season and the winter season when the temperature is below 25 degrees Celsius. Sadly, this method is still uncommon, therefore, not fully understood and controllable; improvement on the temperature and lighting control of the terrarium test method is needed to further develop the terrarium test method into a moss receptivity testing method. Finally, the redesign of the quay wall element focus is to increase moisture gain through capillary action on the masonry finish of the quay walls. This can be achieved by using bricks with an Initial rate of absorption value above 3.0 kg/m2*minute and pointing made of either trass lime or lime 4 | P a g e mortar to promote capillary absorption of the masonry finish. Site consideration regarding quay wall orientation should be taken into account since this will influence the moisture condition and the moss cultivation technique time of application during winter and protection against external factor that prevents moss germination. It is concluded that moss growth on quay walls can be stimulated by particularly improving the moisture condition on the quay walls exterior finish, as moisture was found to be the key parameter that determines the presence or absence of mosses on concrete structures such as quay walls. Resulting in an increase in greenery in Amsterdam city, which can be further translated into social and environmental values such as better air quality by filtering airborne dust, stimulating the ecosystem by producing food for the primary consumer and followed by an increase in the benefits of access to nature to human health. How citizens will perceive the green moss quay walls is unknown, especially since the moss growth comes with other organisms' growth and is not evergreen throughout the whole year and how will the moss growth influence the durability of the material over a long period. Therefore, more studies and experiments regarding moss greening should be conducted to understand this greening method better.

The changing climate and the need for a new purpose for End-of-Life concrete increased the importance and interest of concrete recycling. To decrease the environmental footprint of concrete, in which cement has the highest contribution, it would be of great importance to be able to recycle cement, which would positively affect the environment. The separation efficiency plays an important role in the cement properties. The Smart Crusher is a novel concrete crushing- and separation technology developed to optimize the separation efficiency of the concrete. This study investigates the recycling potential of the cementitious fractions obtained from the Smart Crusher. The aim of this research is to evaluate the reactivity of the cementitious binder retrieved from recycled cement stone to obtain a fully functional binder that can replace primary cement in constructions and structural elements. To gain more insight in the reactivity of cementitious binder retrieved from recycled cement stone, the Smart Crusher cement fractions, which in this study had an unknown origin, are compared with non-hydrated and hydrated reference cements CEM I 52.5 R and CEM III/B 42.5 N. Therefore, the different materials are characterized, using TGA, DSC, MS, XRF and XRD. Analysis of the chemical and mineralogical composition showed the presence of hydration products in the hydrated Smart Crusher, CEM I 52.5 R and CEM III/B 42.5 N samples. Additionally, quartz is found in the cementitious fractions of the Smart Crusher, which indicates the presence of aggregate particles such as sand in these samples. Furthermore, the absence of P2O5 in the cementitious Smart Crusher fractions proved that there is no or a not measurable amount of fly ash present in the cementitious Smart Crusher fractions. Upcycling of the hydrated Smart Crusher, CEM I 52.5 R and CEM III/B 42.5 N materials is done by thermal treatment. To assess the upcycling, again the chemical and mineralogical composition is analysed. Red colouration (500 °C and 800 °C) and melting (1400 °C) of the cementitious Smart Crusher fractions again show the presence of aggregate particles in the material. During thermal treatments of the Smart Crusher, CEM I 52.5 R and CEM III/B 42.5 N materials, the decomposition of hydration products and calcite are monitored, using TGA, DSC and MS. The thermal treatment at 800 °C showed the formation of alite and belite phases in all the samples and was therefore seen as the treatment with the most potential in this research. The only material that shows the formation of alite and belite during other thermal treatments was CEM I. After the thermal treatments the composition and crystalline phases were determined, using XRD and XRF. Insight in the mechanical performance of the different binders was obtained by flexural and compressive strength tests. Mortar prisms were made, containing CEM I and CEM III/B as reference cement and thermally treated CEM I, CEM III/B, 0.0 – 0.063 mm and 0.063 – 0.125 mm cementitious Smart Crusher fractions. The mortar mixtures with the thermally treated binders were observed to be rather dry as a result of an increasing water demand. Compared to new cement, the increase in water demand led to a low degree of compaction, resulting in return to strength properties that were practically unmeasurable. The reference cement showed a lower early strength for CEM III/B compared to CEM I and comparable strength after 28 days due to the higher gain of strength of CEM III/B. Especially the flexural and compressive mechanical tests showed that more research is necessary. To conclude, this study showed that a certain reactivity can be expected in the secondary binders after upcycling, but that the unmeasurable strength properties of the upcycled materials showed the need for more research to make a better estimation of that reactivity.

The world population will continue to grow, resulting in an overpopulated planet and increased urbanization. This creates several problems, such as heat stress in cities, reduced biodiversity and the disappearance of greenery in cities. The World Health Organization has made a list of indicators based on which the sustainability of cities can be assessed. One of these indicators is a minimum amount of 9 m2 green space per capita. Currently, few cities meet this requirement, which threatens the quality of life for city dwellers. A possible solution to obtain more green area in urban regions can be to have more green surfaces on buildings and structures. To realize this in an efficient, low maintenance, and cheap way, concrete could be designed to stimulate the growth of mosses. Spontaneous abundant moss growth on young concrete structures can actually already be observed in the build environment, however this is often unintentional and unwanted, and is seen as degradation of the concrete. A better understanding of why spontaneous moss growth occurs on some constructions while it does not on others can help to intentionally design green concrete structures, and eliminate unwanted spontaneous moss growth on concrete. It has been found in this research that the curing conditions and the cement type being used are two major influencing factors that can contribute to the presence or absence of abundant moss growth on current relative young concrete constructions. A hospitable concrete surface is needed to support the growth of a biofilm, that can subsequently develop in moss. This hospitable concrete surface is provided by the concrete microstructure, a lowered pH, and a sufficient surface roughness. To obtain concrete that is bioreceptive and will enable mosses to grow on its surface, a low-clinker content concrete must be used that is insufficiently cured. This will cause a porous and permeable outer layer of the concrete, that has been related to moss growth on concrete. Due to the low buffering capacity towards alkalinity, the pH at the cover zone of the concrete will be lower, thereby making the surface more attractive for micro-organisms to settle on. Another effect of insufficient curing is an increase in carbonation, which also leads to a more porous and permeable cover zone for low-clinker concrete. To prevent moss growth on concrete, a dense microstructure and a high pH at the outer layer of the concrete must be created. This can be obtained by using a high-clinker content concrete. From this research it can be concluded that a high-clinker mix is relatively not very vulnerable for the curing conditions. A high-clinker content concrete will provide a dense microstructure and high buffer capacity towards alkalinity, even though it has been cured insufficiently.

Rapidly expanding urban developments are having an inverse relationship on the surrounding urban environment. Facades and the materials that they are composed of can have a large impact on the warming of urban microclimates. By reducing or cooling the external surfaces of a facade a building maybe able to offset its contribution to the urban heat island effect. The thesis will help quantify the theoretical impact that this new living facade system can have on external surface temperatures. However, because this is a new facade technique, developing the facade design will also generate the guidelines needed to achieve a bioreceptive urban facade. The resulting facade design will reveal insights and discover the limitations of such an application into urban environments.