Abstract:
Earth as a building material has been used over the years in the construction
industry. However its strength characteristics have been inadequate. Therefore,
stabilizers are used to enhance its strength. Where conventional stabilizing agents
like cement and lime have been used, they have considerably increased the cost of
construction. It is with this backdrop that this paper describes the pozzolanic
characteristics of municipal solid waste ash (MSWA) and its use as a stabilizing
agent. The total elemental concentration in the MSWA was determined by use of
Total X‐ray Florescence method, while the laser particle analysis method was used
to determine the particle size distribution of the ash. X‐ray Diffractometer method
was used to measure the level of molecular compounds including the oxides of
silicon, aluminium and iron. The Total X‐Ray Florescence (TXRF) analysis indicated
that the ash contained high levels of calcium (220,240 mg/kg) and mercury (23.76
mg/kg). According to the Canadian Public Health guidelines, this concentration of
mercury exceeded the acceptable limit of 23 mg/kg. Calcite was the main oxide
(57.6%) with its glass halos occurring between 20° to 50° two‐theta. The total
amounts of SiO2, Al2O3, and Fe2O3 were less than 70%, categorising the ash as Class
F pozzolana meaning that MSWA was not self‐cementing. Laser diffraction particle
size analysis showed that the ash was mainly composed of particles finer than
0.002 mm (55.82%), with its probability distribution function depicting a bimodal
curve. The municipal solid waste (MSW) had a high loss of ignition (83.49%), an
indication that it contained high amounts of un‐burnt carbon. Despite the low
quartz (SiO2) content as compared to that of pozzolana cement, MSWA had high
calcite (CaCO3) content enabling it to contribute to bonding effect of the ash. From
the study, it is recommended that MSWA has to be used as a bonding agent and
not as a cementing ash. Also the ash has to be finely ground prior to use as a
pozzolanic material in soil stabilization, so as to increase both its filler and bonding
effect.
