INGENIEUR
Table 1 . Chemical composition of binder |
Chemical composition (%) |
SiO 2
|
Al 2
O 3
|
Fe 2
O 3
|
CaO |
K 2
O
|
MgO |
CO 2
|
SO 3
|
LOI |
Ordinary Portland Cement ( OPC ) |
16.40 |
4.24 |
3.53 |
68.30 |
0.22 |
2.39 |
0.10 |
4.39 |
2.40 |
Fly Ash |
46.7 |
35.9 |
5.0 |
3.9 |
0.5 |
0.8 |
- |
- |
0.11 |
coarse fine
Figure 1 . Coal bottom ash used in the research
Table 2 . Mix proportion of concrete mixes |
Mixes |
Binder ( kg / m 3 ) |
Coarse Aggregates ( kg / m 3 ) |
Fine Aggregates ( kg / m 3 ) |
|
Cement |
CFA |
Granite |
CBA |
Sand |
CBA |
Control |
440 |
- |
780 |
- |
881 |
- |
Coal Concrete |
308 |
132 |
- |
769 |
- |
881 |
* CBA – Coal Bottom Ash , CFA – Coal Fly Ash |
Test Methods The characterisation of coal waste was determined using a grading test , a bulk density test , a crushing index test and a water absorption test . Fresh and hardened state properties of the concrete with replacement of coal waste in it were determined . During the fresh state of the concrete , it was tested for workability by conducting a slump test while in the hardened state , it was tested for compressive strength at seven , 14 and 28 days .
RESULTS AND DISCUSSION
Physical Properties of Coal Bottom Ash ( CBA ) Table 3 shows the physical properties of the aggregates used . Since the density of coal bottom ash is less than sand and granite , adding a large amount of coal bottom ash reduces the density of concrete . Previous findings reported that the bulk density of coal bottom ash was in the range of 700 to 1400kg / m 3 depending on the size of aggregates [ 16 ]. The specific gravity for sand , granite and coal bottom ash are 2.62 , 2.7 and 1.22 , respectively . Similar findings reported that the range of specific gravity of coal bottom ash is between 1.39 and 2.8 [ 16 ]. The water absorption at 24 hours for sand , granite and coal bottom ash are 3.4 %, 1.8 % and 26.5 %, respectively . Coal bottom ash showed a higher water absorption due to its porous surface . Therefore , coal bottom ash needs to be in a saturated dry surface ( SDS ) condition before it can be used in the preparation of concrete .
58 VOL 83 JULY-SEPTEMBER 2020