The success has prompted them to think about other products they could manufacture, with planter boxes next on the agenda.
"We're trying to find quite bulky stuff, because if it weighs more, we're using more plastic," Finlayson said.
He said the concept was formed around March 2019, setting off a long research and development process:
"We wanted to have something that we could use as a building material, but also be environmentally-friendly."
Environcrete put together some trial blocks for strength testing using materials such as apple fibre and coconut husk.
But the best option proved to be plastic, as it didn't compromise the strength of the concrete at all, Finlayson said.
Hastings Mayor Sandra Hazlehurst said she first met the team when they presented their idea a couple of years ago.
"Their initiative and leadership in managing and minimising waste going to our landfill is truly inspirational to our council," she said.
"They have researched and developed this product over some time and created this outstanding piece of furniture which will sit proudly at our council for our community to enjoy."
The seat should be in place within the next few weeks after a concrete pad is installed.
By building the outdoor furniture with a cement mixture including 10 per cent plastic (about 1000 plastic bottles worth), the students hope to help tackle two environmental problems.
Reducing the amount of cement in the concrete mixture lessens the associated Co2 emissions, while using the plastic keeps it from going to a landfill.
The students acknowledged the help received from seat manufacturers Latteys Concrete, Jason Kendrick who gave support and technical advice, and suppliers Bridgeman Concrete and Alto Packaging.
