Recent studies have shown that crushed oyster shells can perform as a viable aggregate or grit in concrete and mortars. Not only that, oyster grit could do a great deal to help reduce CO2 emissions.
There is much that can be done to reduce CO2 emissions associated with construction. Concrete is a good point of departure partly because it is present in most buildings and accounts for 7-10% of global CO2 emissions, which is a vast amount. But more sustainable forms of concrete exist that use recycled materials in their mix. In particular, the increasing cost of transporting raw aggregate materials such as gravel has led researchers to begin investigating alternative sources for concrete aggregates.
In a study undertaken at the University of Florida, recycled oyster shells were used as an aggregate to form a permeable concrete tile. The shells came from local area restaurants which were sending around 10,000 oyster shells each week to the landfill. The test results showed that after drying, a concrete tile made with oyster shell aggregate had a similar colour, texture and strength to that of a commercial concrete tile. In the case of mortar, a South Korean university study found no significant reduction in the compressive strength of the mortars containing small oyster shell particles instead of sand.
Enormous amounts of oyster shells are discarded each year from oyster farms and restaurants. Oyster shells are non-biodegradable and pollute the land and water when discarded indiscriminately. Using these shells as raw materials for concrete products when they would otherwise go to waste could help to solve the problem of disposing of oyster shells. These changes aren’t radically transforming concrete yet. However, simply by using a material that would have otherwise gone to waste, the CO2 emissions associated with concrete are reduced. A little bit can go a long way!