Below presents the proposal as submitted to NWO, July 2023

Grant received, December 2023

Candidate: ir. H. Alkisaei

Promotor: Prof.dr.ir. L.J. (Bert) Sluys

Co-promotor: Prof.dr.ir. P.C. (Christian) Louter

Affiliation: Delft University of Technology

Title: Waste and manufactured building blocks for a circular structural design methodology.

Abstract

This research proposal aims to investigate the integration of waste objects, like glass bottles or reclaimed structural elements, and innovative materials, like mechanical metamaterials, as building blocks for new structural elements in the context of circular construction applications. The main objective is to address the global challenges of waste production, resource depletion, and environmental degradation associated with traditional construction methods. Through the adaptation of circular economy principles, the research seeks to promote sustainable development and enhance resource efficiency within the built environment.

The investigation will be conducted through a combination of modelling and experimental techniques. Finite element modelling and structural analyses will optimise the force, shape, and structure of the unit building blocks, exploring various configurations to determine their optimal performance. Physical prototypes will be constructed, and experimental testing will be performed to evaluate the load-bearing capacity, structural behaviour, and deformation characteristics of the building blocks.

It is the aim of the research to provide practical guidelines and recommendations for the implementation of waste reduction strategies, reuse of structural elements, and circular materials and technologies. Additionally, the research expects to demonstrate the feasibility and effectiveness of using waste objects and innovative materials as building blocks by showcasing their mechanical performance, load-bearing capacity, and structural integrity.

This research is expected to have broad implications for the construction industry, architects, engineers, and policymakers. The research outcomes will contribute to the knowledge base on sustainable construction practices and circular economy principles. By promoting resource efficiency, waste reduction, and the adoption of innovative materials, this research will support the development of a more sustainable and environmentally responsible built environment. Ultimately, the research aims to accelerate the transition towards a circular construction paradigm that fosters sustainable development and a greener future.

Introduction and research questions

The built environment has always played a significant role in shaping our society and has always had a profound impact on the economy, the environment, and most importantly the wellbeing of human beings. The traditional model of construction and demolition results in extensive waste production, resource depletion and environmental degradation. In addition, with the rapid population growth and urbanisation, annual waste generation is expected to increase by 73% by 2050 (The World Bank, 2022).

To address these global and societal challenges and in order to promote sustainable development, there is a need to adopt circular economy principles within the built environment.

Traditional construction methods often lead to substantial waste generation. It is therefore paramount to investigate and implement innovative construction methods in order to significantly reduce waste production, enhance resource efficiency, and promote circularity within the built environment. 

One study suggests that the waste of construction could be reduced significantly by designing for standard materials size and by designing for modern methods of construction (Ajayi, 2018).

Another study suggests to reuse structural elements without transformation, in order to reduce the consumption of materials and lowering GHG emissions (Bertin, 2019).

A different research suggests that structural elements should be used as long as possible regardless of the limitation of the building service life, while satisfying high quality and strength, structural safety, stability and integrity requirements (Hradil, 2014).

Innovation in new materials and technologies is also an important aspect of enhancing circularity in the built environment. Innovative materials, like mechanical metamaterials, often produced through additive manufacturing, offer the possibility of designing material properties and functionalities that cannot be realised in conventional materials (Bertoldi, 2017). One may think of zero or negative values for familiar mechanical properties, like density, Poisson’s ratio or more recently, pattern and shape transformations, and reprogrammable stiffness or dissipation (Coulais, 2016), (Miniaci, 2016), (Findeisen, 2017).

Contemporary knowledge on waste reduction strategies, reuse of structural elements, and circular materials and technologies, pose several scientific discussions and research questions. For example, there is a major knowledge gap and lack of methodology on ways to effectively implement actual waste objects, reclaimed structural elements or innovative materials and technologies into construction projects, while taking structural integrity and safety into account.

There is also a major knowledge gap on the implementation of innovative materials, like mechanical metamaterials, on a large and macro-scale level. The method of implementation and scale will have a significant impact on the design and long-term durability and performances of the innovative materials. These knowledge gaps lead to the following main research question:

“What methodological, prediction or optimisation models can be developed for the implementation of actual waste objects, reclaimed structural elements or innovative materials and technologies into construction projects, while taking structural integrity, sustainability and safety into account?”

This research aims to explore the potential and applicability of using waste objects, like glass bottles (Maachi, 2022) or reclaimed structural elements, and/or innovative materials, like mechanical metamaterials, as ‘building blocks’ for the construction of new structural elements. These building blocks are assigned a certain ‘unit’ size and could be applied at several locations in a building. The aim is to develop building blocks that can be attached to other building blocks, be dismantled when necessary, and placed and attached at a different location and to a different building block in a building. This offers the possibility to create different structural elements using the same building blocks, but in different configurations. In one combination the building blocks could create a structural beam and in a different combination the same building blocks could create a structural column.

The following figure presents the different building blocks in different combinations and consistency.

The building blocks will need to be investigated and tested for their structural integrity, safety and capacity. Several research questions arise:

1. What actual waste object or reclaimed structural element is applicable for building blocks?

2. What material type of mechanical metamaterial is applicable for building blocks?

3. What internal and external design of building blocks is optimal for the application?

4. What are the optimal internal inertia properties of a building block?

5. What methodologies of connecting and attaching different building blocks to each other is of great importance in order to make adjacent building blocks collaborate in order to form a load-bearing structural element?

In conclusion, this research can pave the way for a more resource-efficient, environmentally responsible, and socially beneficial built environment.

Potential contribution of the proposed research to science

This research is highly relevant within the field of the built environment, where traditional construction and demolition methods have resulted in extensive waste production, resource depletion, and environmental degradation. By putting the focus on reducing waste, reusing materials, and developing circular materials and technologies, pressing global and societal issues related to sustainable development are addressed. This aligns with the scientific effort to move towards more resource-efficient and environmentally responsible methods within the construction industry.

In addition, this research adds to scientific knowledge by exploring and advancing the implementation of circularity methodologies in the built environment. This research proposes to generate empirical evidence and insights into the effectiveness and applicability of using waste objects or innovative materials, like mechanical metamaterials, as building blocks for structural elements. Consequently, it will enlarge the current knowledge of waste reduction, material reuse, and the environmental impact of construction. This will also contribute to the development of new theories and frameworks for circular construction practices. The examination of the design and assembly of unit building blocks explores novel approaches to the creation of structural elements. Moreover, it introduces the concept of adaptability and flexibility in construction and structural design, and it addresses the utilisation of waste objects or innovative materials in a modular and standardised manner.

This research carries significant potential for innovation within the built environment. The proposed methodology introduces a novel approach to material sourcing and utilisation. The concept of unit building blocks and their various combinations presents a novel approach of designing and constructing structural elements, which enable flexibility, efficiency, and resource optimisation. Also, this research approach explores the use of digital tools to facilitate the design, manufacturing, and assembly processes. The integration of advanced technology in the construction industry has the potential to enhance productivity, accuracy, and sustainability in the built environment.

Lastly, the innovative value of the research does not only focus on circular economy principles but also on the interdisciplinary nature of integrating concepts from materials science, structural engineering, sustainable design, and digital technologies.

Research design, research approach and methodology

This research aims to investigate the potential and the applicability of using building blocks, which consist of waste objects or innovative materials, for structural elements within the context of circular construction processes. The research design employs a mixed method approach that combines modelling and experimental techniques in order to obtain a comprehensive understanding of the mechanical properties and behaviour, the load-bearing capacity, and the structural performance of the unit building blocks.

This research captures both the theoretical insights and practical implications due the employment of a combination of modelling simulations and experimental testing. This ensures the effectiveness and reliability of the research findings. Consequently, this comprehensive approach enables a deeper understanding of the performance of the unit building blocks and their potential as sustainable alternatives in the construction industry.

Numerical modelling:

The numerical modelling component of the research is a crucial part for the optimisation of the force, shape, and the structure of the unit building blocks. The Finite Element Method (FEM) and structural analyses will be carried out in order to simulate the behaviour of the building blocks under different loading and configuration conditions. The modelling process assesses the mechanical behaviour, force and stress flows, and overall structural integrity of the building block(s).

For numerical modelling, advanced software packages, like Abaqus, ANSYS, and DIANA FEA, will be used to perform FEM analyses and structural simulations. These software tools provide robust capabilities for modelling complex geometries and configurations, analysing material and mechanical properties, and predicting the structural response under different loads and boundary conditions. In addition, the simulations will be able to highlight the optimal configurations and structural arrangements that can maximise the performance of a unit building block.

Moreover, this research will compare and analyse the mechanical properties and behaviour of a single unit building block versus the complete and whole structural element. By finite element modelling and analysis, the stress and strain distribution which form within the building blocks and the structural elements can be evaluated. This approach provides insights into the load-bearing capacity, stability, and the structural performance of the building blocks in different configurations.

During the modelling process, this research will consider the mechanical properties of the materials used for the unit building blocks, i.e. waste objects or innovative materials. Material properties and data, including elastic moduli, Poisson’s ratio, and strength properties, will be taken into account during simulations in order to accurately represent the mechanical behaviour of the building blocks.

Physical experiments:

Physical experiments need to be carried out in order to validate the findings from the numerical modelling phase and provide practical evidence of the performance of the unit building blocks. For the application of building blocks with waste objects, actual waste objects are used to create a physical prototype for practical experiments. For building blocks with innovative materials, 3D printing techniques or other additive manufacturing methodologies will be utilised to construct physical prototypes for practical experiments. 3D printing methods have the advantage of ensuring accurate reproduction of unit building blocks, whereas building blocks with actual waste objects are more prone to imperfections and errors.

In order to evaluate the performance of the unit building blocks, various tests will be carried out on different sizes of physical prototypes. Compressive tests will be carried out to assess the load-bearing capacity and resistance to compressive forces and buckling behaviour. Three-point bending tests will be conducted in order to measure the bending stiffness and overall strength of the building blocks under different loading conditions. From these tests are important data on the structural behaviour, deformation characteristics, and failure modes of the building blocks obtained.

By implementing the appropriate instrumentation techniques accurate stress and strain measurements during experimental testing are ensured. For example, strain gauges or displacement sensors will be strategically placed on several locations on the building blocks in order to register the deformations and response to applied loads. Afterwards, the collected data will enable the calculation of stress and strain distributions, providing more insights into the structural performance and behaviour of the unit building blocks.

The results obtained from the experiments will be compared with the outcomes of the numerical modelling simulations in order to validate the accuracy and reliability of the numerical modelling approach. Any inconsistencies or variations between the experimental and simulated results will be thoroughly analysed, investigated and discussed through an iterative process in order to improve the modelling methodology and its alignment with the real world.

By integrating the numerical modelling and the experimental data a comprehensive understanding of the performance of the unit building blocks and their potential and applicability for structural applications are formed. The results from the numerical modelling simulations will inform the design and configuration of the physical prototypes for the experimental testing, whereas the experimental data, in turn, will provide empirical data to validate and improve the numerical modelling approach. This iterative process will ensure that the numerical modelling simulations accurately register the mechanical behaviour and structural response of the unit building blocks. Ultimately, the theoretical insights are aligned with the practical implementation.

Potential contribution of the proposed research to society

This research focuses on waste reduction strategies, reuse of structural elements, and circular materials and technologies. This approach has the potential to contribute significantly to society by addressing the pressing global challenges in the construction industry and promoting sustainable development. It aligns with the broader societal goals of resource efficiency, environmental preservation, and social well-being.

Researching the use of waste objects, like glass bottles or reclaimed structural elements, or innovative materials, like mechanical metamaterials, as building blocks for new structural elements will lead to minimising waste generation, optimising resource utilisation, and promoting circular economy principles. This has a direct impact on the reduction of environmental pollution, the conservation of natural resources, and the mitigation of negative impacts of construction activities on ecosystems. 

Whether it is reusing structural elements, implementing waste objects or applying innovative materials, these approaches make sure that materials are kept in use for as long as possible and reduces the need for the extraction and manufacturing of new materials. In addition, innovative materials may offer enhanced performance characteristics, like the increase in strength, durability, and energy efficiency. This can contribute to the development of more resilient and sustainable built environments.

The societal impact of this research also extends beyond the construction and building industry. It can have a positive socio-economic impact by creating job opportunities in waste management and construction industries. In addition, it can also contribute significantly to the global efforts towards mitigating climate change and achieving the United Nations Sustainable Development Goals.

Literature references

Ajayi, S. O., & Oyedele, L. O. (2018). Critical design factors for minimising waste in construction projects: A structural equation modelling approach. Resources Conservation and Recycling, 137, 302–313. https://doi.org/10.1016/j.resconrec.2018.06.005 

Bertin, I., Lebrun, F., Braham, N., & Roy, R. L. (2019). Construction, deconstruction, reuse of the structural elements: the circular economy to reach zero carbon. IOP Conference Series, 323(1), 012020. https://doi.org/10.1088/1755-1315/323/1/012020 

Bertoldi, K., Vitelli, V., Christensen, J., & Van Hecke, M. (2017). Flexible mechanical metamaterials. Nature Reviews Materials, 2(11). https://doi.org/10.1038/natrevmats.2017.66 

Coulais, C., Teomy, E., De Reus, K., Shokef, Y., & Van Hecke, M. (2016). Combinatorial design of textured mechanical metamaterials. Nature, 535(7613), 529–532. https://doi.org/10.1038/nature18960 

Findeisen, C., Hohe, J., Kadic, M., & Gumbsch, P. (2017). Characteristics of mechanical metamaterials based on buckling elements. Journal of the Mechanics and Physics of Solids, 102, 151–164. https://doi.org/10.1016/j.jmps.2017.02.011 

Hradil, P. (2014). Re-use of structural elements: Environmentally efficient recovery of building components. VTT’s Research Information Portal. https://cris.vtt.fi/en/publications/re-use-of-structural-elements-environmentally-efficient-recovery- 

Maachi, Y. (2022). Exploring the potential reuse of glass bottles in structural columns: Investigating the Structural Behaviour of Glass Columns Containing Glass Bottles through FE-modelling and Physical testing. https://repository.tudelft.nl/islandora/object/uuid%3Aeb8529e3-b118-46c1-bc4b-350bf286eb38?collection=education 

Miniaci, M., Krushynska, A., Bosia, F., & Pugno, N. M. (2016). Large scale mechanical metamaterials as seismic shields. New Journal of Physics, 18(8), 083041. https://doi.org/10.1088/1367-2630/18/8/083041 

World Bank Group. (2022). Solid Waste Management. In World Bank. https://www.worldbank.org/en/topic/urbandevelopment/brief/solid-waste-management