Development of synthetic light weight soil aggregates utilizing coal fly ash and mine day as waste materials

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.