Abstract:
This paper presents an investigation of the development, evaluation and micro
morphological observations of synthetic light weight soil aggregates utilizing coal fly ash,
Okinawa mine clay and used paper as waste materials. In this study series of aggregates
have been produced by using several fly ash application percentages from 0 to 100 with
other waste materials as an alternative method of waste disposal. Relation-ship between
applied coal ash percentage and different aggregate parameters such as bulk density, water
holding capacity, permeability, aggregate strength, aggregate stability and mean weight
diameter were determined. The results of the study show that fly ash addition percentage
had a correlation co-efficient of 0.9107 with the bulk density of the aggregates. Moreover
coal ash addition percentage had correlation co-efficients o f0.8625,0.9519 and 0.9560 with
mean weight diameter difference, aggregate strength and loss percentage of finer fraction
less than 1mm respectively. Coal fly ash addition percentages below 40% showed low
aggregate strength values. Highest aggregate strength was given with 100% of ash
application. Bulk densities o f all aggregates were in between 0.68 -1.02 gem'3 which is in the
range of light weight aggregates. Permeability of all aggregates showed an average value of
2.7 x 10 "2cm/sec. Water holding capacities of all treatments showed high values in between
0.69 - 0.74 l/kg. PH values of aggregates were in the range o f 5.85 - 8.25 and nitrogen
percentages of all produced aggregates were in between 0.03% - 0.06%. Lowest loss
percentage of finer fraction (less than 1 mm) was given at 100% of ash application after
subjecting to mechanical shaking. Scanning electron microscopic (SEM) observations
indicated that coal fly ash and mine day particles are well enmeshed in the used paper
matrix with starch as the binder to form stable light weight soil aggregates. Low application
percentages of coal fly ash showed poor binding in SEM images. The study also revealed
that aggregates produced by coal fly ash, mine day and used paper with starch enhanced
the aggregation while improving aggregate performances with increasing percentages of
coal fly ash application.