Conventional concrete is the most widely used construction material. It consumes about 30% of non-renewable natural resources, emitting about 8% of atmospheric greenhouse gases and comprising up to 50% of landfill.
A team of researchers from Flinders University in Australia, working with experts in the US and Turkey, is building a case for more sustainable concrete by replacing synthetic reinforcement materials with natural fibers and materials from different waste streams.
The study demonstrates how geopolymers reinforced with renewable natural fibers and waste-based sands from lead smelting or glass-making can match the strength, durability, and drying shrinkage qualities of those containing natural sand, which in turn consumes more raw resources and generates extra emissions in its processing. According to the researchers, the findings have significant potential for the use of natural fibers in the development of structural-grade construction materials, in which binder and aggregate are replaced by industrial by-products and waste-based materials.
The test results showed that geopolymers using waste glass sand exhibit superior strength and lower water absorption than those containing natural river sand – while lead smelter slag (LSS)-based geopolymers have lower drying shrinkage compared to geopolymers prepared with natural river sand.
Natural fibers such as ramie, sisal, hemp, coir, jute, and bamboo were incorporated in testing experiments. The geopolymers – containing 1% ramie, hemp, and bamboo fiber and 2% ramie fiber – exhibit higher compressive and tensile strength and a lower drying shrinkage than unreinforced geopolymers. Those containing 1% ramie fiber have the highest strength and lowest drying shrinkage.
“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 fibers which otherwise would not be used constructively,” said the lead researcher Dr. Aliakbar Gholampour.
“This research will also look to design mixes of recycled coarse aggregates and other types of cellulosic fibers, including water paper, for different construction and building applications. We also plan to investigate their application in construction 3D printing for the future.”
The team said the study adds to global efforts to tackle the environmental impact of producing conventional building materials and landfill volumes.
- Aliakbar Gholampour, Aamar Danish, Togay Ozbakkaloglu, Jung Heum Yeon, and Osman Gencel. Mechanical and durability properties of natural fiber-reinforced geopolymers containing lead smelter slag and waste glass sand. Construction and Building Materials, 2022; DOI: 10.1016/j.conbuildmat.2022.129043