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

However, POFA contribute to its long-term strength due to the continuous pozzolanic reaction because of the fine particle size, the greater glassy phase of SiO2 and the reduced composition of carbon (Zeyad et al., 2012). This is also proved by Altwair et al. (2011) using the strength activity index which is the ratio of the strength of SCM-cement mortar to cement mortar at specific curing time.

2.3 Ultrasonic Pulse Velocity (UPV) of Concrete with Replaced POFA
      According to Kanadasan & Razak, (2015), UPV has the relationship with the replacement level of the RePOFA. From the UPV result as the replacement level was increased from 0 % to 50 %. The positive relationship between UPV and replacement percentage was displayed from the replacement of 15 % to 30 % while the UPV was reduced as the replacement level continued to increase until 50 %. The result of the UPV against RePOFA is shown in Figure 2.4. The same result was retrieved from the experiment done by Awal & Shehu (2015). As the authors replaced the cement with 50 % to 70 % of RePOFA, the UPV seemed to reduce. Furthermore, the UPV value of 50 % to 70 % RePOFA cement concrete is also lower than the value obtained from the ordinary Portland cement. This also reflects the concept that the replacement ratio of the SCM should not exceed the satisfied limit. According to Hwang et al. (2012), the UPV result which falls between 3.66 km/s and 4.575 km/s indicates a good quality. Even though the UPV value decreased as the replacement ratio increased from 50 % to 70 %, the value of UPV still remained above 3.66 km/s. Meanwhile, the UPV value of above 4.5 km/s was obtained from 5 % to 50 % of RePOFA replacement level (Kanadasan & Razak, 2015; Awal & Shehu, 2015). Therefore, it can be concluded that the RePOFA can help to enhance the microstructure properties plus the compressive strength of the specimens as shown in Figure 2.4.