© Australian Sugar Mill Council

Using bagasse to stabilise expansive soils

Queensland’s clay soils are prone to shrinking when dry and expanding when wet, which can create significant difficulties for infrastructure particularly highways. Until now, the Department of Transport and Main Roads (TMR) in Queensland has been reluctant to change its established methods for dealing with these soils, such as lime stabilisation. Through joint research with TMR, the project team challenged this tradition.  We investigated ways to stabilise the expansive clay soils using bagasse, a by-product of sugar cane.

The research, including laboratory testing, demonstrated significant reductions in shrinkage and swelling behaviour and increased strength in clay soil that has been mixed with bagasse fibre and bagasse ash. The increase in strength of bagasse-treated clay soils is likely to result from chemical reactions with certain clay minerals in the soil, particularly montmorillonite and illite.

Stabilisation of expansive clay soils is possible using bagasse fibre and bagasse ash.

After adding bagasse ash into the soil sample, linear shrinkage values decrease significantly.

The use of bagasse as stabilisation agent allows the quantity of hydrated lime used to be reduced by approximately 40%.

 

The findings of this research are positive for the agricultural sector in Queensland and in countries that have a sugar cane industry and expansive clay soils, provided that the clay mineralogy responds appropriately to bagasse.

An industrial application would be to blend bagasse fibre and bagasse ash into the subgrade layer of a road pavement, resulting in a product that provides more durable pavements to the benefit of the road network.

By partnering with the Queensland Department of Transport and Main Roads, we achieved substantial and innovative steps together. The project has generated proven technical results and developing a new solution for the stabilisation of expansive clay, reducing cost of road construction in areas with challenging ground conditions. Additionally, the new solution provides a commercial use and value for sugar cane waste products that could bring economic and sustainability benefits.

While this project was originally specific to Queensland, our findings can be applied in any location that is facing the challenge of expansive clay soil environments and there are sugar cane processing facilities present in the area.