USE OF FLY ASH FROM DIFFERENT SOURCES IN BITUMINOUS CONSTRUCTION

Abstract

Morphological as well as Mineralogical composition of fly ashes collected from 14 different sources was carried out through particle size distribution, particle shape and texture analysis, void content, clay content, X Ray Diffractometry, SEM and ICP-MS. Based on the common physical and chemical characteristics and predominantly from calcium oxide, iron oxide and silica oxide concentration, these fly ashes were grouped into four major groups Bhatinda Local City (Fly ash -1), Indraprasth (fly ash -2) Ghandinagar (Fly ash -3), Ramagundum (Fly ash — 4). Further tests on Bituminous Mastic and Bituminous Concrete were carried out with these fly ash groups as filler to understand the effect of change of source on properties of bituminous concrete. Conventional filler stone dust was also used for comparison. Particle size analysis showed that the different filler materials have varying particle size distribution (minus 75 micron size). Rigden voids are the highest in case of Fly ash — 4 (z44 %) and the lowest in case of stone dust (z31 %), indicating that the mastic of Fly ash — 4 would be very stiff as compared to that prepared with stone dust. Good correlation is obtained between the German filler test value and the Rigden voids, and hence these two tests can be used in complementary manner. Higher methylene blue values in case of stone dust and Fly ash — 2 indicate that these materials should be more susceptible to moisture induced damage, as compared to other fillers. SEM analysis reveals the presence of hollow particles like Perosphere and Cenosphere may be reason for low SG of Kalgaoon fly ash. Presence of higher calcium oxide in Fly ash — 4 makes this filler more resistant to stripping in bituminous mixes. Viscosity and viscosity ratios are found to increase with the percent bulk volume of fines in the mastic. An increase in softening point by 9°C or a viscosity ratio of 8 which corresponds to 60% bulk volume concentration of filler is suggested as a guideline to avoid excessive stiff mastic and finally the mix. Rutting resistance of fly ash mixes iii increases with the increase in filler/bitumen ratio and decreases with the increase in test temperature and found to be maximum for Fly ash — 4. It was found that the optimum binder content (OBC) of bituminous concrete decreases with the increase in fly ash content. Same trend for OBC was seen in case of stone dust. All the fly ash groups showed good resistance to moisture induced damage as compared to stone dust and they can be optimally used up to 7.0 % as filler in a bituminous mix. Among various fly ash groups Fly ash — 3 will prove to be very economical, as mixes with these fly ash group has the lowest OBC. The strength and moisture susceptibility parameters of mastic and bituminous mixed with Fly ash — 4 is highest among all fly ashes, which may be due to presence of comparatively higher calcium oxide content. The use of fly ash will reduce the environmental pollution and solve aggregate requirement to certain extent.