Remediation of Expansive Soils Using Agricultural Waste Bagasse Ash

Abstract

Bagasse is a fibrous material remaining after crushing sugarcane to extract its juice; and bagasse ash is produced after burning bagasse. Improper disposal of this material can create environmental problems around sugar manufacturing plants. Bagasse ash, comprising a high percentage of silica (SiO2), is considered as a sensible pozzolanic material with non-reactive behaviour and has potential to be used in road subgrade stabilisation. One of the main challenges for transportation organisations in Australia is to treat subgrades including expansive soils. Expansive soils exhibit significant movements when the moisture content changes, and hence it causes substantial damage to road pavements constructed over these type of soils. Road engineers need to employ materials having acceptable strength, relatively low price and being eco-friendly. In order to demonstrate the potential ability of bagasse ash in curtailing the adverse effects of expansive soils on roads, an array of experimental tests using bagasse ash have been conducted. In this study to activate and improve the effectiveness of bagasse ash, hydrated lime was used and mixed with black soil samples, collected from Queensland Australia. Samples were prepared using different contents of bagasse ash and hydrated lime (0%, 6%, 10%, 18% and 25% by the dry mass of soil), at a ratio of 3:1, respectively. The results of free swell ratio (FSR) test, unconfined compression strength (UCS) and California bearing ratio (CBR) tests are presented for untreated and treated samples after various curing time periods of 3, 7 and 28 days. The outcomes of these tests clearly demonstrate that stabilisation of expansive soils using bagasse ash and hydrated lime not only improves the strength, but also facilitates to cope with environmental concerns through reduction of sugar industry waste material.