Evaluation Of Mechanical Properties Of Palm Oil Fuel Ash (pofa) Blended – Granite - Gravel Concrete

2.2 Compressive Strength of Concrete with Replaced POFA
      According to Jaturapitakkul et al. (2011), the compressive strength of mortar which used 40 % of POFA replacement shows he lowest strength compared to the ordinary mortar without the addition of POFA. The case also remained similar when compared to the result obtained by Kroehong et al. (2011), which utilized 20 % replacement of POFA but slightly higher than 40% replacement in terms of compressive strength. In the research, the author also discovered that the paste with the replacement of 40 % POFA had the weakest strength. The compressive strength of the paste was found around 20 MPa lower than the paste with 20 % POFA replacement. From the result published by Sata et al. (2004), the concrete which used 30 % of POFA as Supplementary Cementing Materials (SCM) shows a drop in compressive strength compared to the concrete with 20 % of POFA even though all of the POFA concrete showed the higher compressive strength than the control concrete. From the research mentioned, it was observed that the water/binder ratio was fixed at 0.40 and this provides a meaning that 30 % to 40 % of the replacement percentage might be the limit for the POFA replacement ratio. According to the research above, the trend of the compressive strength of concrete or mortar regarding the factor of the POFA replacement ratio is obtained.            RePOFA can be utilized as SCM for self-compacting concrete with the replacement percentage of 70 %. However, Safiuddin et al. (2012) suggested that the replacement level of POFA should be limited to 30 % maximum as the replacement ratio more than that will cause the decrement of workability and then result in low compressive strength. In short, the trend of the compressive strength of either POFA or RePOFA regarding the replacement ratio is displayed as in Figure 2.2.