According to United Nations demographic forecasts, by 2050 more than 70 per cent of the world’s population will live in cities. The urban heat island phenomenon, i.e. the increase in temperature in densely built-up urban areas compared to the surrounding suburban and rural ones, will affect the majority ofthe world’s population and its mitigation will be crucial to maintain acceptable living conditions, also in light of worsening climate change.
The AMSHI project aims at contributing to the effort to mitigate this phenomenon, by designing a self-locking paving block with a low degree of embodied energy for public spaces that, thanks to its porosity, composition and colour characteristics, can contribute to reduce the urban heat island effect.
The main stakeholders with whom we collaborated, in addition to the professors and tutors who assisted us during the research and development phases ofthe block, were the municipality of Savona, which chose to test the block in the area in front of the university, and two companies. The first, Ferrari BK, is specialised in the production of traditional out-door paving blocks for aver 50 years. The second, R3direct, is a Tuscan company specialised in 30 printing, with which we collaborated to work on the moulds for the finishing layer of the blocks. Our role, in addition to active design, was to mediate between the differ-ent parties. We have visited the companies two times to see their production methods up dose and to better understand the block engineering process that we later had to use.
To design a feasible solution from an economical and industrial point of view, the block that we have been called to design had to meet standards that not only concern thermal performance, but also ease of production, low cost, environmental sustainability, simplicity of installation and execution, and good aesthetic appearance that allows it to be used in central and prestigious urban contexts.
The objectives to be pursued, therefore, on which the preliminary research and design work was based, are listed below:
Thermal performance: the block must be able to guarantee a high level of porosity that contributes to maintain a good level! of thermo-hygrometric comfort. The albedo, i.e., the reflective power of the surface, is also important in order not to absorb energy from the solar radiation as it would later be released in the form of heat. To understand the effects of the urban heat island, we carried out a measurement campaign in Savona, supplemented by a questionnaire that we had some of the city’s inhabitants fili out, to understand their degree of dissatisfaction with the microclimatic conditions.
Sustainability: the block must have a low embodied energy level, i.e. a low impact in the use of limited resources of the environment.
The initial idea was to use geopolymer-based binders instead of traditional cement. However, the high costs ofthe materials and their hazardousness during production made us opt fora more traditional solution using a standard cement as a binder. The leve! of embodied energy compared to traditional concrete binders was achieved using recycled aggregates.
Mechanical strength: the ratios of recycled aggregate to primary aggregate were optimised through mechanical strength tests in the laboratories of the Politecnico di Torino. The block will be used for pavements operating under a limited flow oflight weight vehicles, and there-fore comply with specific mechanical characteristics.
Urban quality: the blocks, used for paving public spaces, should contribute to urban regeneration, not only from the point of view of thermo-hygrometric comfort, but also from the point of view of accessibility and quality of public spaces. We researched and studied some good examples of urban regeneration at ali scales to understand which elements and characteristics are the most relevant for urban regeneration in generai and for the specific design of the paving block. The choice of colours was based on a study of the recurring colours in the aesthetic identity of the city of Savona. Starting from a single block, thanks to its shape and the controlled randomisation of the colours, it was possible to obtain a great variety in the designs.
Industrialisation and scalability of the product: To mitigate the urban heat island effect, Iarge public surfaces need to be changed. It is therefore important that the blocks are produced through an industriai process as simplified as possible. For this reason, we had to make several adjustments to the originai design of the block to simplify the production process and make it possible, without failing to meet ali the above-mentioned objectives.
Once we had established the design and composition of the paving block (the main objective of the project), the possible colour combinations, and carried out the mechanical tests, we were carried out the masterplan design for the product test on the area indicated by the municipality of Savona. We had to maintain the number of parking spaces present for the university’s needs, but we optimised the composition of the routes and the position of vehicular traffic.
After that, we focused on better defining the first 200-square-meter area to be built, designing the colour composition of the individual blocks through computational design, which allowed us to efficiently and immediately produce multiple options that could be compared. This design method also made it possible to calculate in advance the exact number of blocks to be produced based on colour. Future developments in the project will involve industrial production of the 18,900 blocks and subsequent installation by operators. A new measurement campaign, this time carried out on the new paving, will be able to empirically demonstrate how the AMSHI paving block is a valid solution for urban heat island mitigation, as well as a potential more sustainable alternative to traditional asphalt pavements.