Thesis Open Access
ABEBE DEMEKE WOLDEGIORGIS
Mesay Daniel ( Dr)
This study assessed the effects of coffee husk ash (agricultural by-product) on the index and strength properties of expansive soil. Coffee Husk (CH) is the major by-product in the processing of coffee bean. Some of these wastes are left in open dumps while some are burn in the open space, and these two actions have been contributing to environmental pollution.
During construction, the removal of expansive soils and replacement with suitable fill material is an appropriate method in areas where abundant nearby suitable fill materials are available. However, at places where limited suitable fill material exists within economical distance and if large thickness of poor sub-grade soil are to be replaced, this method is not economical. To this effect, the most commonly used technique is chemical stabilization with cement and lime which are very expensive.
Disturbed expansive soil samples used for this research are collected from test pits located at Ayat (Bole sub city), Jemo (Nifas silk Lafto sub city) and Tulu Dimtu (Akaki kality sub city).The soils were initially classified based on index tests and found to be A-7-5 and CH according to AASHTO and USCS respectively. To determine the effects of CHA, the necessary laboratory tests such as index tests, strength test and swelling test are incorporated for the natural as well as the stabilized soil (expansive soil with 10%, 20% and 30% of CHA).
Analyses of the results show that, high improvement on the index properties and strength properties of soil stabilized with CHA. As the coffee husk ash content increases, plasticity index decreases 24% to 60%, liquid limit decreases from 13% to38%, maximum dry density (MDD) decreases from 5% to 13%, and swelling pressure are decreases by 48% to 64%. Whereas optimum moisture content (OMC) increases by 16% to 29%, California bearing ratio (CBR) values are increases by 84.7% to 90.7% with CHA content are increased.
In this study the use of coffee husk ash solves the problems comes with the expansive soil with less cost and easy of availability
EFFECTS OF COFFEE HUSK ASH ON INDEX AND STRENGTH PROPERTIES OF EXPANSIVE SOILS.pdf