Geotechnical Assessment and Stabilisation of Lateritic Soils in Tarkwa Using Rice Husk Ash for Road Construction Purpose

Abstract

The cost effectiveness of upgrading gravel roads to a sealed standard has challenged road authorities to make optimum use of naturally occurring materials such as laterites as sub-base and base materials. Untreated laterites have presented problems such as pavement swelling and depression in road construction. This research seeks to assess and stabilise the geotechnical properties of some lateritic soils in Tarkwa using Rice Husk Ash for road construction purposes. Lateritic soils obtained from Akoon and Kwabedu are labelled AK and KW respectively. Rice husk was obtained from Ejisu in the Ashanti Region of Ghana and burnt to ashes. The lateritic soils were subjected to Atterberg limits, compaction and California Bearing Ratio tests. The lateritic soils were subsequently mixed with Rice Husk Ash in varying percentages of 5 % and 10 % and the influence of Rice Husk Ash on the soils was determined for Atterberg limits, compaction and California Bearing Ratio tests. The Plasticity Index of sample AK and KW were 20.18 % and 11.3 % respectively. At 10 % addition of Rice Husk Ash, the Plasticity Index of AK reduced to 8.02 % and KW to 5.22 %. The Maximum Dry Density of sample AK reduced from 2.22 Mg/m³ at 0 % Rice Husk Ash to 1.88 Mg/m³ at 10 % Rice Husk Ash. The Optimum Moisture Content of AK increased from 13.72 % to 19.9 %. The Maximum Dry Density of sample KW reduced from 1.88 Mg/m³ at 0 % Rice Husk Ash to 1.73 Mg/m³ at 10 % Rice Husk Ash whiles the Optimum Moisture Content increased from 14.72 % at 0 % Rice Husk Ash to 19.9 % at 10 % Rice Husk Ash. The California Bearing Ratio value for sample AK is 24 % and for sample KW is 43 %. At 10 % addition of Rice Husk Ash, the California Bearing Ratio for AK and KW increased to 61 % and 78 % respectively. The lateritic soils from Kwabedu are adjudged suitable for sub-base and lateritic soils from Akoon are not suitable for sub-base. Rice Husk Ash effectively stabilised the lateritic soils for base course for low traffic roads.