Self-healing concrete technology has been widely investigated in the past decade as a solution against degradation and/or loss of functionality in cracked concrete elements. Many self-healing mechanisms have been proposed and proven to work experimentally in the literature. Among these systems, the use of encapsulated mineral-producing healing agents seems to be the best working combination of components to successfully heal the cracks. The involved triggering-healing mechanisms usually consist of complex physical phenomena. Hence proper optimization of the proposed self-healing material is not possible through often resource- and time-consuming experimental campaigns. Instead, numerical modelling could be a useful tool for timely and exhaustive investigation of the self-healing mechanisms, as well as the design of appropriate experimental setups. Yet, while research on self-healing concrete seems to keep growing, comparatively the amount of modelling work devoted to the optimized design of the material has not advanced.
This thesis aims to provide a modelling framework for the study of the main aspects of a capsule-based self-healing cement-based system, namely the mechanical triggering of the self-healing system, the healing process itself and the assessment of the recovered property.
For the self-healing mechanism to work, the triggering of enough capsules along the crack is desired. Notwithstanding, this crack steering optimization comes at the expense of proper mechanical behaviour of the composite. Whereas the earlier aspect has been studied in the past, in this thesis a numerical optimization of the triggering of capsules is carried out taking into account also the achievement of acceptable mechanical performance of the material. To illustrate this, the case of self-healing cement paste with bacteria-embedded polylactic acid (PLA) capsules was selected. A 3D mesoscale lattice model was implemented herein to simulate a uniaxial tensile test on the system composed of cement paste, PLA capsule and their interface. Previous studies on the mechanical behaviour of cement paste with inclusions (i.e. capsules) have shown that the interface transition zone around the inclusion presents microstructural and mechanical properties that are totally different from those of the matrix. Therefore, a meticulous study was first conducted to obtain the mechanical properties of the interface of various types of PLA capsules with respect to bulk cement paste. Nanoindentation was performed to obtain maps of hardness and elastic modulus in the interfaces. 2D microscale lattice modelling of uniaxial tensile test on the mapped locations was performed then to obtain the overall tensile strength and stiffness of the interface. Moreover, hydrates assemblage and chemical composition around the PLA particles were studied through Backscattering Electron images and Energy Dispersive X-ray Spectroscopy. The ratios between resulting tensile strength and elastic modulus of the interface with respect to bulk paste were obtained for each PLA type which were then used as input for the mesoscale model. Cement paste samples with PLA capsules were imaged through X-ray micro Computed Tomography before and after fracture to obtain the capsules distribution to input in the mesoscale model and the fracture surface for validation, respectively. The experimental and simulated stress-strain curves showed excellent correspondence, especially on the elastic phase, hence validating the proposed model. An exhaustive numerical investigation of the material was performed then to analyse the influence of dosage, size and shape of the PLA capsules, as well as of the interface properties on the mechanical behaviour of the composite and the triggering of the PLA capsules. The results show that interface properties close to but lower than the cement matrix do not entail substantial losses of tensile strength and elastic modulus, whereas the amount of triggered capsules is maximized. Optimum dosage, shape and size of the PLA capsules were also obtained.
To illustrate the healing process and the recovery of the functional property within the proposed modelling framework, the case of crack self-sealing in cement mortar with superabsorbent polymers (SAP) was investigated. These healing admixtures steer the crack propagation and become exposed along the fracture surface. Upon contact with ingress water they immediately absorb water and swell, thus providing a water-blocking effect and preventing harming species to further penetrate into the mortar matrix from the crack surfaces. In order to design such self-sealing systems in an efficient way, a three-dimensional mesoscale lattice model is proposed to simulate capillary absorption of water in sound and cracked cement-based materials containing SAP. The numerical results yield the moisture content distribution in cracked and sound domain, as well as the absorption and swelling of SAP embedded in the matrix and in the crack. In a first instance, the model was validated for mortar without SAP, by means of time-resolved X-ray micro Computed Tomography. Additionally, the water absorption and swelling of SAP embedded within the mortar were imaged and quantified over time to better model their role during capillary water absorption in such composite materials. The performance of the model with the presence of SAP was validated by using experimental data from the literature, as well as experimentally-informed input parameters. The validated model was then used to investigate the role of SAP properties and dosage in cementitious mixtures, on the water penetration into the material from cracks. Furthermore different crack widths were considered in the simulations. The model shows good agreement with experimental results. The obtained results show that increasing the SAP water absorption capacity, while reducing their cement solution absorption capacity improves the crack self-sealing effect more efficiently than increasing their dosage. Other guidelines for the selection of appropriate SAP are given for different crack widths. Moreover, it is suggested that capillary water absorption test in cracked concrete is sensitive enough to detect small localized changes in crack width due to the healing of the cracks.

Addis Ababa is experiencing a high rate of urbanization coupled with a decades-old housing crisis. This study problematizes the current housing problem not only in the frame of housing shortage but also as a ‘housing mismatch’, with the underlying dwelling typologies rooted in modernist design ideals not responding to context. These dwelling solutions, as seen in the recent condominium projects, do not fulfil the social and spatial requirements of dwellers. This problem calls for a thorough inquiry into tracing the roots of the ‘housing mismatch’. Since dweller-initiated housing transformations are a common phenomenon in most housing conditions in Addis Ababa, the study proceeded to analyze these transformations to understand the housing mismatch in its qualitative and spatial aspects. One of the reasons for dweller-initiated transformations is to finetune living habitats to cultural parameters. In line with this, transformations were observed during the test run of the fieldwork conducted on three households in 2020. Furthermore, the fieldwork revealed that dwellers used local conceptions of space such as the gibi, the gwaro and the gwada to explain the socio-spatial phenomena of transformations....

Uncontrolled cracking in reinforced concrete structures accelerates durability issues by creating pathways for external agents to penetrate the matrix, often leading to costly repairs and reduced service life. This dissertation addresses these challenges through the development of a self-healing strain-hardening cementitious composite (SHCC) designed specifically for application in the concrete cover zone.

This thesis adopted a multi-faceted methodology. First, a self-healing SHCC material was developed, featuring bacteria-embedded polylactic acid (PLA) capsules to realize controlled microcracking and robust healing. Next, the research introduced a localized application strategy to address the cost-effectiveness of this material. By applying the self-healing SHCC exclusively to the concrete cover zone, the region most critical to durability, this approach minimizes unnecessary use of healing agents, balancing performance with economic viability. To validate the concept, experimental and numerical analyses were conducted to evaluate the performance of hybrid beams with self-healing SHCC covers. Furthermore, different manufacturing methods, including prefabrication and 3d printing, were explored. Lastly, design strategies were proposed to incorporate the self-healing benefits into structural service life models. The feasibility of the developed system was demonstrated at full scale by applying it in the construction of a tramline.

The study revealed that the incorporation of PLA capsules into SHCC significantly improved crack-healing efficiency while maintaining critical tensile properties. It was found that the fibre/matrix bond properties were enhanced by the addition of the HA. As a result, the addition of healing agents reduced residual crack widths by up to 70%, ensuring faster and more robust healing under varied conditions.

At the structural level, hybrid beams with SHCC covers exhibited enhanced performance. Beams with SHCC applied in the bottom cover zone demonstrated improved flexural behaviour, with controlled crack patterns and reduced crack widths, attributed to the optimized interface condition between the SHCC cover and concrete core. A novel type of SHCC/concrete interface that features a weakened chemical adhesion, but an enhanced mechanical interlock bonding was developed to facilitate the activation of SHCC. Similarly, hybrid beams with lateral SHCC layers showed a notable increase in shear resistance under critical loading conditions. Numerical simulations supported these experimental findings, revealing the importance of the interface condition between SHCC cover and concrete core.

For the developed self-healing cover system to be applied in structures, it is necessary to consider the implications of healing during the design process. Analysis of this thesis shows that, by refining existing engineering models to include the impact of cracks, it becomes possible to predict and design the healing effects under specific scenarios.
To further demonstrate the self-healing cover concept, the developed self-healing SHCC was applied in a full-scale construction project where stringent requirements for tensile performance and crack healing properties are essential. The project showcased the feasibility of large-scale mixing, pumping, and application of the self-healing SHCC system.

This thesis contributes to the field of self-healing concrete by advancing material performance, structural application techniques, and design integration. By focusing on localized and practical implementations, the research bridges the gap between experimental advancements and full-scale applications where traditional solutions do not meet demands. The findings underscore the potential of self-healing concrete to extend the service life of structures without imposing substantial additional costs.

Since more than a decade, TU Delft has been working on the development of bacteria
based self-healing concrete. The self-healing ability of the material is based on a
biological mechanism in which a limestone producing bacteria is added to the material
to repair cracks.
The purpose of this study was to understand and compare the efficiency of different
methods and materials used for incorporating bacteria into mortar. The aim of the study
was to create a self-healing mortar mix for practical applications.
Concrete is a widely used construction material. Most structural elements are made
using concrete and covered by a protective layer of mortar, called plaster. Cracks
usually propagate from the surface to the inside, which means that the plaster is the
first to crack. If the mortar is made self-healing, then the concrete underneath can be
better protected from the elements, and this could effectively increase the lifespan of
the structure.
For this project, fibre reinforced mortar is healed using bacteria (Bacillus Cohnii) which
is applied to the concrete using internal (different types of embedded capsules) and
external methods (paste applied to the cracks).
This is done to check the effectiveness of the bacteria in repairing damaged concrete
and to observe which method of application works best. The effectiveness is analysed
using optical and electron (BSE) microscopy and a permeability test to observe the
water tightness of the sample after cracking.
Additionally, characterization tests are performed on the capsules and performance
tests are carried on the mortar samples, to better understand their behaviour.
This study would help in making concrete structures more durable which would make
them more sustainable and cheaper in the long term.
This study found that crack healing is dependent on the crack width and the number of
capsules present in the material near the crack. The compressive and flexural strength
at 28 and 84 days was found to be higher in samples embedded with alginate capsules
and PLA capsules. External healing was found to be a good method for healing existing
materials but the healing was found to be dependent on the amount of paste that
adhered to the crack wall

This thesis investigates the optimization of steel weight and the Environmental Cost Indicator (ECI) in steel structures, addressing the significant contribution of materials and construction to global carbon emissions. Focusing on European office structures, which face high vacancy rates and substantial environmental impact, a parametric study is conducted on a 5-story, 30x30m steel office building. The study evaluates design choices, including column, beam, and composite beam spacings, cross-section selection, connection design, and stability systems.
A preliminary building is designed under consistent load conditions, followed by over 50 variants incorporating different stability systems, frame designs, and composite beam spacings. Analysis indicates that smaller column and beam spacings, along with larger composite beam spacings, optimize steel use and ECI costs. HEA sections for columns, IPE sections for beams, and CHS sections for diagrid braces and angled columns are identified as the most efficient.
The study also highlights that material use does not always correlate with ECI costs. Designs incorporating demountability initially increase steel use due to elastic design requirements but result in lower ECI costs over multiple lifecycles by enabling reuse of materials. Several diagrid designs, benefiting from lower ECI costs per kilogram of CHS sections, perform better than conventional and braced structures despite higher initial material use.
Demountability was a key focus, with bolted connections identified as essential for achieving demountability standards. The reuse potential of stability members varies significantly; unlike conventional designs, diagrid structures are tailor-made, making their reuse challenging for subsequent applications.
The findings are consolidated into a final design framework to guide engineers in optimizing steel use and ECI costs, providing a practical tool that reduces the need for extensive modelling. This research fills gaps in the literature by focusing on short structures and offering insights into efficient structural design practices.

Water levels in the river Meuse drop during periods of low river discharges, making it unnavigable for shipping. To maintain navigability in the Dutch part of the river Meuse, seven weir complexes were constructed in the river. These complexes regulate the river and maintain target water levels to allow for shipping throughout the entire year. The complexes were constructed in the early 20th century and are all reaching the end of their technical lifetime. Therefore, they require replacement or renovation. This provides the opportunity to explore ecosystem restoration at these complexes.
The seven weir complexes are located at Borgharen, Linne, Roermond, Belfeld, Sambeek, Grave, and Lith. Each complex consists of weirs, locks, and fish ladders. These complexes act as barriers to fish migration, the river’s sediment transport, and reduce the lotic habitats in the river (in Dutch: ‘Stromende habitats’). The reduction of lotic habitats leads to a decline in species that depend on these environments.
The objective of this report is to study the possibility of creating an optimized ecological route at conceptual level for the weir complexes in the Dutch part of the river Meuse to create environmental conditions for the formation of lotic habitats. This optimized ecological route is referred to as an ecological channel. The channel was designed to support specific endangered river species, referred to as the target river species.
The channel was initially designed for weir complex Sambeek, which serves as the case study location. This complex was selected as it has the most available space, which provides more flexibility for the channel’s design. Subsequently, an assessment was conducted to determine whether the channel could be applied to the other complex locations. To form lotic habitats, the channel must meet certain environmental conditions that are based on the needs of the target river species. These conditions must be achieved during the critical reproductive months of these species. The environmental conditions primarily consist of varying flow conditions, which are achieved by varying inflow rates, indicating the need of an intake structure.
The ecological channel was designed through an iterative process, as its dimensions and flow conditions have interdependent relationships. These parameters had to be iteratively adjusted until a suitable combination was found that met the required conditions. To streamline the process and reduce the number of possible combinations, the design of the channel’s intake structure and the channel’s dimensions were done separately.
The final ecological channel design includes an intake structure consisting of a flap gate and vertical-slot fish passage. An impression of the final channel design at weir complex Sambeek is shown in the figure on the following page. The channel design meets the required environmental conditions for habitat formation for river discharges up to 500 m3/s for weir complex Sambeek, Linne, Roermond, and Grave, and for discharges up to 250 m3/s at complex Borgharen, Belfeld, and Lith. Both discharge ranges include the critical reproductive months of the target river species, as was required. The final design shows that the required environmental conditions for lotic habitat formation can be achieved at the weir complexes in the Dutch part of river Meuse, potentially leading to an increase in the populations of the target river species.
The channel design may not accurately represent reality due to uncertainties in the estimations and limitations of the channel’s boundary conditions, available space, and simplifications of its hydraulic processes. In addition, even if the required environmental conditions are achieved, it does not guarantee that the river species will utilize the channel, as their behaviours can be unpredictable, and their response may not be as anticipated. To develop a more realistic and detailed design, it is recommended to construct a hydraulic model and conduct further research on the behaviours of the river species.

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.

This study investigates the development of sustainable offshore fish farms in Sisal, Yucatán. Local fishermen face seasonal restrictions on fishing due to environmental regulations. Given the socioeconomic dependence of the region on fishing, the community of Sisal has been experiencing increasing instability of livelihoods. Offshore fish farming has emerged as a potential solution to this challenge, offering an alternative income source outside the traditional fishing season. However, previous industrial attempts to introduce fish cages failed due to a lack of local engagement and inadequate design, leaving Sisal residents sceptical. To address these past issues, this research seeks to design affordable, durable, and locally accepted fish cages that meet the unique environmental and social conditions of Sisal. Valuable insights were gained from fish farms in Celestún, a nearby village with successful communityled offshore aquaculture. Celestún’s approach, using smaller, manageable, and collectively funded cage, has proven to be both economically and socially beneficial. This makes it a relevant model for Sisal, though Sisal’s steeper coastal gradients and greater exposure to maritime forces require adaptations to ensure durability and long-term success. The research follows a multi-step methodology, beginning with interviews with local fishermen and experts to understand their needs and preferences for cage design and placement. These insights were integrated with environmental data on wave height, wave period, and current speeds collected through field measurements and the ERA5 reanalysis dataset. Using this input, an Multi-Criteria-Analysis (MCA) was conducted to determine the optimal offshore location for the fish farms. To determine the structural needs for fish cages under Sisal’s conditions, the research used ProteusDS simulation software [14] to model various cage dimensions, mooring tensions, and layout configurations. Key findings indicate that positioning the fish farms at 8 kilometres offshore is optimal for long term success. At closer distances to the coast, water quality decreases, resulting in higher maintenance requirements and compromised fish health. Greater distances increase installation costs and operational costs due to higher fuel demands. With the optimal location established, the research follows with the determination of key design parameters essential for the structural integrity of the fish cages near Sisal. An extreme value analysis of an ERA5 dataset was performed to estimate the 20-year return level for the wave height, resulting in a design wave height of 4.19 metres. This value was adjusted for local conditions using a scaling factor derived from the comparison between local and ERA5 data, resulting in an adjusted design wave height of 3.40 metres. A power-law regression was then applied to establish the relationship between wave height and wave period, estimating a design wave period of approximately 8.01 seconds corresponding to the adjusted wave height. For the current analysis, the 95th percentile of current speeds was examined, determining a maximum design current speed of 0.50 m/s near the surface. Furthermore, analysis of wave and current directions revealed that extreme waves predominantly come from the north to north-east directions (340° to 20°), while the strongest currents flow toward 70° and 250°, indicating eastward and westward flows. The optimal cage design determined through simulations includes a cage diameter of 12 metres and a net depth of 4.7 metres to withstand Sisal’s environmental forces. Additionally, distinct mooring-tension configurations were tested in the ProteusDS software, including Concept 1 (a single-cage setup), Concept 2 (a two-cage configuration with four mooring anchors), and Concept 3 (a three-cage arrangement with three anchors). Each concept required specific anchor weights and dimensions to endure the high wave and current forces at this location. Orientation adjustments were also incorporated to reduce tension, aligning each cage setup with different wave and current directions, thereby optimizing structural reliability. Future fish cage designs should include adaptive anchoring and precise orientation to enhance stability and involve the local community for sustainable, long-term success. The study concludes that, to achieve long-term viability, fish cages in Sisal must be affordable, easy to maintain, and capable of withstanding local environmental conditions. Future recommendations include deepening community involvement, implementing enhanced safety and resilience measures, and refining cost analysis to foster broad acceptance among local fishermen. By ensuring that the fish cages are both economically viable and environmentally sustainable, this project aims to secure a stable income for Sisal’s fishing community, thereby improving their quality of life while reducing pressure on marine ecosystems

This research investigates the integration of environmental costs into the cost-benefit analysis (CBA) framework for constructing circular viaducts. Circular viaducts offer environmental benefits but face challenges due to their higher initial construction costs. The traditional CBA framework focuses solely on economic costs, hindering the adoption of circular construction. This research proposes a methodology to monetize environmental costs and integrate them into the CBA framework to make informed decisions about circular viaduct construction.
The methodology involves analysing the environmental impact of circular viaducts and traditional viaducts using Life Cycle Assessment (LCA) and Environmental Product Declarations (EPDs). The environmental impact is then monetized using agreed-upon values from various stakeholders. The monetized environmental costs are incorporated into the CBA framework using cash flows and the net present value (NPV) method.
The research findings indicate that the implementation of circular viaducts is most viable in scenarios with longer lifespans. In these scenarios, the overall environmental costs of the circular viaduct are lower than those of the traditional viaduct due to the lower frequency of replacement. However, the NPV analysis reveals that the traditional viaduct has lower present value environmental costs in all three scenarios. This is due to the difficulty of accurately predicting future material prices, which could significantly impact the economic benefits of material reuse in the circular viaduct.
Results show that while the circular viaduct exhibits higher environmental costs in some scenarios, its economic benefits through material reuse, particularly in scenarios two and three, make it a more viable option. However, further research and development are needed to reduce the initial environmental and economic costs of circular viaducts to achieve a wider and faster adoption of this sustainable construction method.

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 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.

An extensive Life Cycle Analysis (LCA) is used to determine the efficiency in reducing the carbon footprint of a graving dock. Firstly by identifying the hotspots in a base design, and then by comparing the various design alternatives. The focus is on reducing the amount of reinforced concrete used in the design of the dock floor by adding fibres to the concrete mixture and on prevention of having to dispose of in-flowing sediment after every docking procedure. Other evaluation methods such as a Cost Benefit Analysis (CBA) that compares the economic viability and a Multi Criteria Analysis that combines the results of the LCA and CBA and assesses the design alternatives on other criteria such as ease of operation and maintenance are used to determine the optimal dock configuration for Damen Shipyard and Conversion B.V. in Harlingen.

The Dutch construction sector has the task in the coming years, to build around 1 million new houses in the Netherlands, most of which will have to be built in urban areas. Together with existing (inter)national crises such as the climate change crisis and biodiversity loss crisis, this means the sector will have to think differently to not jeopardise the liveability of our cities. One way of doing this is to create more Nature-based Solutions in these urban areas, but the perception is that this is an expensive solution. By using the framework from Ecosystem Accounting, the benefits these Nature-based Solutions can give us, are monetised to show that the perception of it being expensive is wrong. The aim for this research was to see how Ecosystem Accounting can be used in procurement procedures to create more Nature-based Solutions.

With the double diamond approach, this study was split into two sections. In the first section of the research, a literature study and stakeholder interviews were used to find the most important themes for clients and contractors to have an ambition for Nature-based Solution. These themes were: biodiversity, climate adaptation, health & wellbeing and aesthetic value. In the second section, a new literature research combined with key informant interviews indicators for these themes were found. A total of four indicators (Vegetation layer score, shadow cover, air quality and soil quality) and five services (rainwater regulation service, local climate regulation service, health service of nature, visual amenity service of nature and visual amenity service of water) were found.

For effective use of the framework, three moments in time are important. In the ambition phase Ecosystem Accounting can be used to formulate the ambition of a project. In the tender phase (depending on the amount of design freedom in the contract) EA can be used as a requirement or as a MEAT-criterium. To assure that the plans are realised, the control phase should not be forgotten either.

This study addresses the critical need for specialized risk identification practices in green retrofit projects within the construction industry, particularly under the increasing pressure to meet the EU's net-zero emissions target by 2050. Focusing on the Netherlands, it investigates how companies navigate the unique challenges posed by updating existing infrastructure to be more sustainable and energy-efficient. Through a mixed-method approach comprising a literature review, field study in Voorburg, and semi-structured interviews with experts, the research identifies distinct risks such as performance risks, supply chain disruptions, and uncertainties in returns on investment. Royal Haskoning DHV's approach, including their Fast-Lane Method, is examined for its effectiveness in predicting energy use but noted for its limitations in estimating carbon emissions and broader retrofit tasks.

The study advocates for an integrated approach utilizing Building Information Modelling (BIM) to enhance risk management and project outcomes. It highlights the gap in current risk management practices that fail to fully address sustainability challenges in retrofits and suggests future research directions, including broader studies involving multiple companies and technologies, to develop more comprehensive risk management strategies for green retrofit projects.

Green roofs can play an important role in reducing problems in urban areas by being flexible, multifunctional and adaptable. These features of nature have proven effective in combating climate change and contribute to human well-being. Previous research has shown that green roofs can sometimes be cost-effective, but the benefits included in cost-benefit analyses are fragmented and an absence of a learning curve in the literature regarding green roofs is discernible. This research focuses on how to determine the economic value of the benefits of green roofs and what methodologies are used to do so. There is also a need to bridge the gap between research on costs and benefits and research on external costs of production materials. This research contributes to bridging this gap by creating a full life-cycle cost-benefit analysis of a green roof by mapping and analysing current methodologies. This research contributes to sustainable development and in it serves as a starting point to determine the utilisation of green roofs with the pursuit of sustainable urban development.

The construction industry in the Netherlands is taking numerous measures throughout the industry to achieve the possible reduction of CO2 emission or GHG emissions by 2050 to become carbon neutral. Based on the current situation the major focus is usually on the production and construction phase of a building or a civil infrastructure. To meet the requirements to minimize CO2 emissions, the municipalities and the stakeholders involved in the maintenance phase of civil structures have to improve the emission reduction process. This can be made possible if the quantification of the CO2 emission is improvised from the current status and focuses only on the maintenance activities alone.

The results of the research are obtained from the developed information model. The information model allows the user to estimate the CO2 emissions from the maintenance activities of the assets located in a municipality. The data obtained from the estimation of CO2 is used in the dashboard of the information model to visualize and compare the data in terms of different criteria like building materials, size of the assets, location of the assets, heavy machinery usage, etc. This way, the decisions can be made by the involved stakeholders in asset management in the strategies of the maintenance planning of the assets or the overall municipality.

This information model can add value to the existing life cycle applications since the maintenance or the usage phase emission is redefined and the necessary scope for maintenance is added to the existing scope. The consultants, asset owners/managers can monitor the CO2 emission from the maintenance activities specifically and can take any measures with the output data available from the information model. This information model currently quantifies the CO2 emission from the minor maintenance activities of the assets in a municipality. With this information, the next step can lead to optimizing the CO2 emission with other criteria like time and cost for the entire Municipality.

The application of vertical greening systems (VGS) onto building envelopes constitutes an innovative way to implement more green in the living environment. Especially in dense urban areas, where only limited space is available to integrate more horizontal greening at ground level, VGS have the potential to contribute towards creating a greener, healthier, more nature-inclusive and climate resilient urban environment. This by facilitating and contributing to natural ecosystem functioning, hence providing ecosystem services and through those, benefits for society. These benefits include among others an enhanced microclimate, biodiversity and aesthetic appeal, as well as improved physical and mental health, thermal performance, energy efficiency and air quality, and reduction of urban heat island effect and noise disturbance.

In order to substantiate the total set of costs and benefits associated with VGS implementation and enhance rational decision-making, in present research the development of a standardised framework and interactive economic valuation tool is proposed.

In the end, an economic valuation framework and tool were developed which can support the decision-making process regarding VGS application. The framework is based on Life Cycle Cost Analysis (LCCA) and Social Cost Benefit Analysis (SCBA). These analyses relate to real estate investors and society (resident focus) respectively. To assess and report on the values of the costs and benefits of these innovative systems, distinct themes were established. The cost themes entail financial costs, environmental costs and potential Ecosystem Disservices. Benefits are distributed over the themes health & well-being, climate adaptation & mitigation, real estate, social & recreational & commercial and biodiversity.

The current version of the tool is able to perform quantification and monetisation for financial costs, large parts of the environmental costs, reduction of airborne PM10, increased rental incomes (investors) and rental costs (residents), reduced energy usage for heating and MIA & Vamil tax incentives. Based on implemented valuation methods, the case study delivers project specific results. Though, it is explicitly noted that these results do not yet provide a complete representation of all costs and benefits, due to a limited number of (benefit) indicators that are monetised. Hence, this version of the tool should be regarded as initial impetus for further development. This in order to ultimately obtain an all-encompassing VGS Valuation Tool, fit for project specific economic valuation of costs and benefits of VGS.
The result dashboard visualises the valuation outcomes and results in clear tables and graphs, generating insights into the contribution of different themes towards the total costs and benefits of VGS. This can initiate further recommendations for a research agenda into distinct aspects of certain VGS.

Hence, the VGS Valuation tool could become a conversational mechanism or steering instrument, to stimulate or justify choices for specific types of VGS at given locations. The test panel of anticipated end users was enthusiastic about the comprehensiveness and user experience of the tool and acknowledged its future practical value.

The climate emergency calls for a global shift towards a low-carbon economy, to preserve natural resources and biodiversity, while limiting global warming and its consequences. This project focuses on the impact of distribution centres, intended for the storage of commercial goods. Warehouses are characterised by large flexible spaces and simple structural systems, most often with steel or concrete frames aiming at efficiency and low costs. The aim of this research is to create a sustainable single-storey warehouse with a significantly lower environmental impact compared to reference designs with steel and concrete frames. Considering a new-build project with no reuse of existing elements, a meaningful target for embodied carbon reduction is set to 50% of the environmental impact score of reference steel and concrete warehouse designs.
A selection of sustainable design strategies are investigated, giving insight into which actions designers shall take in priority to effectively reduce the embodied carbon of a warehouse. Reducing upfront emissions (LCA modules A1-A3) requires looking into short-term sustainability measures like reducing material use or using low carbon alternatives wherever possible. Replacing fossil-based products by renewable carbon sequestering materials like timber or other biobased alternatives contributes to lowering the impact of a building, by storing biogenic carbon for the lifespan of these elements. A sustainable use of wood presumes that its design lifespan is at least equal to forest rotation periods to maintain or increase the forest timber stock, combined with sustainable forest management practices. Biogenic carbon storage may be extended by designing for long-term reuse or recycling. Greening the envelope of a building takes advantage of ecosystem services provided by vegetation, like improving air quality, enhancing thermal performance or supporting biodiversity. Many systems can be applied on facades and roofs, depending on project-specific requirements (plant species, layout, load-bearing capacity), to effectively introduce vegetation in the built environment.
The first design step investigates the embodied carbon reduction potential of substituting steel or concrete by timber in the load-bearing frame of a warehouse. Reference steel and concrete structures are selected, and baseline timber designs are created with similar geometrical characteristics and stability systems, to compare their environmental impact on a fair basis. The second design step of the research aims at further reducing the impact of not only the frame, but also other parts of the timber warehouse (foundation pads, floor slab, envelope). Big ticket items responsible for the most impact are identified and tackled in priority: in both timber designs, the floor slab and envelope are responsible for the largest share of embodied carbon. Based on the results of design steps 1 and 2, the 50% embodied carbon reduction target can be achieved by substituting steel or concrete in the frame by timber (-31%), replacing sandwich panels on steel supports by biobased materials in the envelope (-13%), and reducing the floor slab thickness by 50mm (-7%), when considering only fossil emissions. If biogenic carbon storage is accounted for, using biobased materials in the frame (-65%) and in the envelope (-58%), without modifying the floor slab, results in a carbon positive warehouse design. These results are only valid assuming long-term carbon storage in biobased materials, supported by circular design measures. Greening the envelope also contributes to making warehouses more sustainable, provided that benefits from ecosystem services outweigh environmental costs from additional materials.

Under service conditions and because of environmental and climate changes, the concrete is at risk due to crack-induced durability problems. The consequences can be even more pronounced when concrete is exposed to specifically aggressive environmental conditions. This has been portrayed by rapid deterioration of relatively young concrete structures such as the ones no older than fifteen years, which obviously are much shorter than their estimated service life. As such, crack-closing ability is needed in these concrete constructions to prolong their service life.
Numerous studies have been reporting on the autogenous healing of cracks in cement-based materials. However, an active or rapid micro-crack healing is not always the case in the most critical parts of exposed structures. In this thesis, a new formulation of cement-based materials, by integrating selected bacteria and suitable organic mineral precursor compounds, was used to investigate its potential for enabling multiple crack healing events on load-induced cracked and pre-cracked concrete samples. For this purpose, chloride ingress in concrete subjected to compressive loading was investigated through laboratory experiments. Furthermore, investigation was also carried out on cracked mortar under chloride and carbon dioxide environments for healing-potential evaluation....

Waste generation is one of the main environmental problems and is a result of the current linear economy. Materials/elements are used whereafter they are wasted which is a problem considering the finite material supply on earth. Therefore, the current linear economy needs to move towards a circular one in which materials are reused and thus kept in the circle. However, reuse is still not a common practise. This is due to the fact that there are no insights in the structural feasibility, potential savings on environmental impact, and costs related to reuse. Besides the lacking knowledge about the different aspects there is no clear image where the potentials for reuse are located within the sector.
The goal of this research is to give insights in the reuse potentials and to find opportunities within the sector. This research started with a material flow analysis to find promising material flows in the sector. In this material flow analysis it was found that the demolition of office buildings is responsible for a big portion of the outgoing material flow and the majority of the ingoing material flow is related to the new construction of serial houses. In the analysis it was found that the elements with the highest ECI and mass are floor elements. Next the available floor elements coming from office buildings and the floor elements needed for the construction of serial houses were examined to check possible matches. It was found that new plank- and hollow core slab floors used in serial houses can potentially be substituted for reused monolithic- and hollow core slab floors out of office buildings.
Thereafter, two different tools were developed. One related to the reuse of monolithic floors and one related to the reuse of hollow core slab floors. These tools are means to give insights in the reuse potentials considering the structural feasibility, potential savings on environmental impact, and costs. Different cases were checked using the tools and the following results were found:
-In all cases it was structurally feasible to use reused floors coming from office buildings in the new construction of serial houses.
-When reused floor elements are used it is possible to save 40-90% on environmental impact.
-Reused floor elements can be cheaper or more expensive as new floor elements.
These results are promising and hopefully contribute to an acceleration of reuse in practise. The research states where the potentials for reuse are located in the sector and presents two tools which check the reuse potentials considering structural feasibility, environmental impact, and costs.