bottle | brick: waste glass aggregate replacement in bricks for Zanzibar

Master Graduation – This graduation project was initiated by the bottle-up foundation a, small scale company established on Zanzibar, East Africa. bottle-up was founded to tackle the waste glass problem on the island by repurposing and recycling. The outcome of the project was exhibited at the Dutch Design Week.

Through a collaboration with waste collection company Zanrec a monthly volume of 17 tons (15500 kg) of glass is brought to the bottle-up workshop. From this volume only 160 kg is used to make accessories that are sold to tourists visiting the island. For the remaining 15000+ kg a solution needed to be developed. Unfortunately the waste glass cannot be remelted in Zanzibar. The significant capital investment required to build a melting facility, paired with the lack of steady electricity supply, and the relatively small amount of glass waste on it island, make it unfeasible to develop in the short term of this project. The search for an alternative solution is the starting point of this project. Conducted context research led to the desire to transform waste glass bottles into cullet to serve as aggregate replacement in bricks. The bricks with glass aggregate should compete on durability, strength and price with the locally produced bricks. Material research was conducted to establish the feasibility of this idea. A lot of scientific research is found on the topic, mainly because of a risk-factor caused by using glass as an aggregate replacement. It causes the chemical alkali-silica reaction (ASR), an expansive reaction that occurs in the mixture when cement paste and reactive aggregate become humid. The expansion causes an increase in volume that generates internal pressures sufficient enough to disrupt and crack the fabric of the concrete. It can decrease strength down to 85% compared its initial strength.Luckily data reported in literature also shows success mitigating the potential risk of ASR. A fitting solution was found for Zanzibar. The usage of low-alkali cement lowers the pH value and does not trigger the reaction. With the use of this low-alkali cement different sample bricks are made on Zanzibar. These bricks were brought to the Netherlands to conduct compressive strength tests on. The results are compared those of local Zanzibari bricks to find the right balance between economical and mechanical feasibility. From this research the bottle | brick (bb) was born. The bb is made from the chupa (bottle) mix, containing 35% aggregate replacement with glass, which accounts for 42% of its weight and is at least twice as strong as the local brick. It is slightly more expensive to produce due to the complex set up. A production cost overview is provided outlining the required investments and costs. A business implementation and process plan was made with which bottle-up could take the bb into production. The initial bottleneck of the recycling process was glass cullet production. To improve the system a glass bottle crusher is created: The farasi machine. This low-tech and cheaply produced machine can process up to 10.000 bottles a day, which is 8 times as much as the current supply of bottles. The machine is designed, prototyped and built on Zanzibar. It is still being operated every day to process glass. bottle-up is considering to further develop the bb and the recycling process next year.