Abstract:
The objective of this study is to assess the quality of the available aggregate material in Jimma
zone. This study focused on the determination of the physical and mechanical properties of
aggregate. To achieve the objective nine representative samples were collected from different
crusher site of the zone for laboratory tests.
Five towns are found with crusher site in the zone; Jimma, Agaro, Haro, Offole and Seka. The
laboratory tests were performed on aggregate samples through: moisture content, unit weight,
specific gravity, Los Angeles abrasion resistance test, water absorption capacity test, impact
value, sieve analysis and flakiness index.
Based on the results of this study, the specific gravity of the rock ranges from 2.67 to 2.87. The
study shows that the natural moisture content varies from 0.79% to 1.83% and the water
absorption value 0.64% to 2.1%. The water absorption and the moisture content are the
nearest 1% that means very small void on a rock sample. While unit weight tests results range
from 1.51-1.67KN/m3
. The bulk density and the Voids between aggregate mixes are inversely
proportional. Maximum Bulk density will make minimum voids so that there won’t be much
space for the cement paste. One way of identifying the strength of the rock sample is crushed
value ranges from 11.61-16.83% according to crushed value the crushed value for cement
concrete pavement shall not exceed 30% and the aggregate crushing value for wearing surface
shall not exceed 45% so, the samples are compatible for both works. Identifying the hardness
of the aggregate sample is Los Angeles abrasion value ranges from 15.67-21.8% and
Aggregate impact value test correspond to the aggregate’s toughness and its values below 10
are regarded as strong, and good for use in road surfaces. Results of impact value tests show
that rocks of Jimma zone have ranges from 6.3-8.5%Comparison was made for standard
specification in this study with laboratory test results. The comparison shows that the
engineering performance of these rocks from the study area lie within the range given by
different international standards and additional tests should be made on chemical property of
aggregate to obtain more data points.
