3. Results and discussion
3.1. Fresh concrete properties
Fig. 2 shows the effect of utilizing ground POFA as partial cement
replacement in OPSC on the slump values. It was observed that 10%
POFA replacement level produced the highest slump value for the
OPSC. This could be due to the greater binder volume as the specific
gravity of POFA is lower than cement, and the excess binder volume
could have provided better coating, lubrication and filling of gaps of
the aggregates (Johari et al., 2012). However, when the POFA content
was increased further up to 25%, the slump values were
reduced. As increased amount of POFA was used, the greater effect
of the increased water demand by POFA could have resulted in the
reduction in the workability of the concrete. The results were in
contrast to the experimental investigation carried out by Johari
et al. (2012) in which when the POFA was used up to 60%
replacement level, there was increased in slump values. One of the
reasons for this occurrence could be the higher LOI of the POFA used
in this study, which is about 3 times higher compared to that used
in the investigation by Johari et al. (2012). The higher LOI of the
POFA used in this study indicates the higher porous nature of the
POFA which increased the water demand of the fresh concrete to a
Table 1
Chemical properties of POFA and OPC.
Binder Chemical composition (%)
CaO Al2O3 MgO SiO2 Na2O SO3 P2O5 K2O TiO2 MnO Fe2O3 Cl LOI
POFA 4.35 5.51 3.78 63.4 0.15 0.93 3.75 6.35 0.34 0.16 4.2 0.46 6.19
OPC 64.2 4.6 3.4 22.7 0.1 2.5 0.2 0.8 0.2 0.9 1.4