As shown in Figure 26, in this chapter the finalizing phase of the research is concluded.
Figure 26: Research design: Chapter 7 & 8
In this chapter two types of recommendations are given. First, recommendations for further research are given, and secondly, recommendations for Witteveen+Bos are given.
8.1
Recommendations for further research
During the research on circular indicators, it became clear that for the connections, retrieval and dimensions indicators it was harder to find information on how they influence 1 on 1 reuse, than for the toxicity, condition and residual lifespan indicators. There hardly exists any theoretical research on these indicators, therefore more knowledge about these indicators should be collected by reusing more components and therefore gaining more experience.
Additionally, it is recommended to further develop this method. It could be developed further by including more design cycles and test cases which would improve the validation of the method. This method could also be furtherly developed by taking a better look at the relative weights of the functional requirements. In this research, it is assumed that all the questions are of equal importance in order to score the categories, but more research could be performed to establish weights for the specific assessment questions.
Furthermore, this method only applies to a specific material, scale and circular loop. Therefore more efforts could be invested in including a broader scope. There are multiple ways to achieve this:
- First, this research only focusses on concrete components. Such a method as is developed in this research could also be developed for other materials such as steel or wooden components, which are also commonly used in infrastructure assets. While some of the functional requirements that are also used for the design of this method could also be used for the assessment of other materials, also new functional requirements need to be investigated. Each material has specific damage mechanisms that could influence the ability for a component to be reused. I.e., ASR is a damage mechanism that only occurs for concrete components.
89 - Second, this method only focusses on assessing single components, while it could be the case that certain components are more suitable for 1 on 1 reuse if they are reused together as a whole. I.e., a whole bridge deck could be more suitable for 1 on 1 reuse than all the individual components separately. Probably there is not much adjustment needed to design a method that takes into account multiple components. However, there is the problem that if multiple components are assessed at the same time, it is also likely that multiple types of materials need to be assessed. Therefore research should first focus on how to assess other types of materials. What also possibly needs to be taken into account when assessing a combination of components is the constructive part. Does the combination of components still meet the design requirements regarding the distribution of forces?
- Third, the method only focusses on the 1 on 1 reuse loop of the circular economy and does not focus on other loops such as recycling or refurbishing concrete. This method could be used as a starting point to develop these methods, but probably not all the functional requirements for this method would apply to these other focus points. I.e., cracks in the concrete can negatively influence a components ability to be reused 1 on 1, but when a concrete component is being recycled through a crusher in order to make new concrete out of it, it does not matter if there are cracks in the component. The other way around, there are certain materials that do no harm if they are already inside the concrete, but they could negatively influence the concrete if the concrete is crushed to make new concrete out of it.
8.2
Recommendations for Witteveen+Bos
It is recommended for the asset management division of Witteveen+Bos to integrate this new inspection and assessment method into the regular condition inspections according to the NEN 2767, which are performed by the asset management division. The new method can help Witteveen+Bos and their clients to assess 1 on 1 reuse and consequently helps them with achieving the circular goals which are drawn up by the Dutch government.
It is easy for Witteveen+Bos to integrate the new method into the regular NEN 2767 inspections, because the new method uses the decomposition according to the NEN 2767 as a basis, and because the NEN 2767 is an important input for the new method. It would save more time to integrate this method within the NEN 2767 inspections than to perform both separately. However, if a NEN 2767 condition inspection has already been performed on an asset, this method can also be executed on its own.
Furthermore, there are some practical recommendations for the implementation of the method. The new method should be discussed with clients that could benefit from reusable components in their assets. By discussing this with the client, it forces the client to think about 1 on 1 reuse of components while they otherwise might not have considered it. If the clients are interested, they should be offered the assessment according to the new method as an extra service. By frequently applying the method next to regular inspections, a frame of reference is created.
90 The results of the method could be stored in a materials passport, which could be helpful to create a long-term construction planning based on reused materials. The Material Quality category is time- dependent, which means that the assessment should be updated once in a while. This can be updated with the same frequency as the NEN 2767 condition inspection is being performed. The other two categories (Disassembly and Applicability) are not time dependent. If these categories have been assessed once, the score does not change over time. Therefore, if a reassessment is taking place, only the Material Quality assessment questions need to be reassessed.
For the circular economy group of Witteveen+Bos, it is recommended to use this method as a baseline for further developments of assessment tools for circular performance in the infrastructure. The method is in line with the 3rd circular design principle of Witteveen+Bos; ‘Make sustainable use of existing objects, materials, resources and natural processes’. Therefore, it could help in the development of the circular design tool which the circular economy group of Witteveen+Bos is developing.
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