100X
300X
Source: http://iopscience.iop.org/1757-899X/160/1/012056
Figure 2: SEM Images of Coal Bottom Ash Particles Size under 100X Magnification
and 300X Magnification
Further analysis of BA was performed using
a Scanning Electron Microscope (SEM) with
magnifying power of 100X and 300X to determine
the microstructure of BA (Figure 2). The SEM
results show that BA has a porous structure,
consisting of pores with an angular and irregular
shape and possesses a rough texture. Some
BA particles have a spherical and popcorn type
features similar to the findings reported earlier by
Novell et. al. The smallest size of BA obtained was
10.05μm while river sand was bigger at 31.25μm.
Thus, making BA more suitable for concrete mix
applications, where fine particle size is essential.
X-ray Fluorescence (XRF) analysis was
performed to determine the chemical composition
of BA and natural river sand. Results of XRF (Table
3) showed significant amount of silicon oxide and
aluminium oxide in both samples. Silicon oxide is
an important element required during concrete
mixing. The chemical composition ratio of BA and
river sand are similar; encouraging the use of BA
as a replacement for sand in the construction
industry, mainly where sand mining is problematic
due to environmental, political and economic
issues. A detailed physical chemical analysis of
BA provides vital morphology of the material
and important information such as content,
compatibility and stability.
Table 4 lists the elemental analysis results of
BA from Malaysia, and a Westfalen power plant
based in Germany. Most of the elements detected
were similar, except manganese was not found
in the samples from the Malaysian plant. This
Table 3: Chemical Composition of Bottom Ash
and Natural River Sand
Formula
Natural
River Sand
(%)
Bottom Ash (BA) (%)
SiO 2
51.00 33.70
Al 2
O 3
6.83 12.90
Fe 2
O 3
0.32 6.98
CaO 0.48 6.34
K 2
O 0.40 1.19
TiO 2
0.58 0.89
MgO ND 0.65
SO 2
ND 0.90
Na 2
O 3
ND 0.59
P 2
O 5
ND 0.30
BaO ND 0.22
Source: https://iopscience.iop.org/
article/10.1088/1757-899X/160/1/012056/pdf
may be due to an ultra-low concentration below
detection limits or the element was not present
at the source. All the reported elements were
below the permissible level, including mercury
and arsenic, which are classified as poisonous
under the Malaysian Poisons Act 1952. Trace
amounts of heavy metals leaching were tested
using Toxicity Characteristic Leaching Procedure
(TCLP) analysis. The results indicated that the
leaching effects of BA were below the permissible
65