Natural fibres and waste materials boost concrete sustainability

Natural fibres and waste products can replace synthetic reinforcement materials to make a more sustainable type of concrete, researchers have said.

The team from Flinders University in Australia, working with experts in the US and Turkey, said that geopolymers reinforced with renewable natural fibres and made with industrial by-products and waste-based sands from lead smelting or glass-making can match the strength and durability of those containing natural sand, which consume more raw resources and generate more emissions.

Conventional concrete is the most widely used construction material, with 25bn tonnes used every year. It consumes about 30% of non-renewable natural resources, emitting about 8% of atmospheric greenhouse gases and comprising up to 50% of landfill.

The “promising findings” have significant potential for the use of natural fibres in the development of structural-grade construction materials, lead researcher Dr Aliakbar Gholampour said.

Geopolymers using waste glass sand have superior strength and lower water absorption than those containing natural river sand, tests found. Lead smelter slag-based geopolymers have lower drying shrinkage compared to geopolymers prepared with natural river sand.

Natural fibres such as ramie, sisal, hemp, coir, jute and bamboo were incorporated in experiments. The geopolymers containing 1% ramie, hemp and bamboo fibre, and 2% ramie fibre, exhibited higher compressive and tensile strength and a lower drying shrinkage than unreinforced geopolymers, the researchers said. 1% ramie fibre had the highest strength and lowest drying shrinkage.

The study adds to global efforts tackling the environmental impact of producing conventional building materials and landfill volumes, the team said.

“With concrete, we can not only recycle huge volumes of industrial by-products and waste materials, including concrete aggregates, to improve the mechanical and durability properties of concrete, but also use alternative eco-friendly natural fibres which otherwise would not be used constructively,” said Dr Gholampour.    

“This research will also look to design mixes of recycled coarse aggregates and other types of cellulosic fibres including water paper, for different construction and building applications. We also plan to investigate their application in construction 3D printing for the future.”

The work was published in the Construction and Building Materials journal.