August 24, 2020 Thesis Open Access

Utilization of plastic waste & Bone Ash to Improve the Engineering properties of Expansive soils

Engidayu Labena Lachore

Thesis supervisor(s)

Argaw Asha ( PHD)

deals with an alternative local waste materials of cattle bone ash and plastic
bottle chips to improve the engineering properties of soil and minimize the environmental
impacts. Cattle bone was burnt in open air and cooled to get bone ash (BA) and plastic
waste bottles washed and cut into pieces to average size of 15mmx15mm. The soil sample
was collected from the southern part of Addis Ababa around ‘Koye feche’ and its index
and engineering properties was carried at natural state and when stabilized with 5, 7 and
10% of bone ash (BA) in dry weight. The California bearing ratio (CBR) test and CBR
swell was performed with optimum BA percentage and when plastic chips (PC) added at
0.4, 0.6 and 0.8% to the soil sample. Results of the tests showed that, the soil sample is A-
7-5(28) and MH as per AASHTO and USCS respectively. Due to addition of bone ash, the
plasticity index (PI), free swell, Linear shrinkage and CBR swell decreased from 45 to 27%
,122.2 to 44.4%, 23.3 to 19.5% and 9.02 to 0.87% respectively. This shows that the
improvement in swelling property of soil. The specific gravity of natural soil reduced from
2.63 to 2.46 at 10 % bone ash contents. This is due to the light weight of BA. The optimum
CBR value obtained at 7% of bone ash content, which increased 31% from the original
soil. The result also showed, 9.8% increment in CBR value at 0.6 % PC with optimum
bone ash content and 11.2% reduction in CBR swell at 10%PC. The improvements in CBR
of expansive soil is adequate to use as subgrade material as per Ehiopian Road Authority.
Both bone ash and plastic chips are a good stabilizer. Furthermore, utilizing wastes for
geotechnical purpose creates one of alternative solid waste management.