Recycling of palm oil fuel ash and rice husk ash in the cleaner production of concrete

Disposal of agricultural waste ashes is significantly increased worldwide due to the rapid implementation of biomass based power plants and leads to severe pollution. Instead of disposal, agro-waste ashes can be efficiently used as an alternative material to conventional cement. However, the reuse of locally available agricultural waste ashes is highly limited in the construction sector because of inadequate understating of their performance in concrete. Hence, a comprehensive review on the performance of two widely available agro-waste ashes, palm oil fuel ash and rice husk ash in concrete is attempted. Physical, chemical, microstructural, and pozzolanic characteristics of palm oil fuel ash and rice husk ash are systematically reviewed. Besides, fresh, mechanical and durability properties of the palm oil fuel ash blended concrete is critically compared with rice husk ash blended concrete. From the literature, it was observed that the inclusion of rice husk ash reduces the workability of concrete significantly, whereas the increase in the workability is reported for the palm oil fuel ash blended concrete. The optimal calcination temperature for palm oil fuel ash and rice husk ash has been reported to be 600-700 degrees C. Higher silica content is observed in rice husk ash compared to palm oil fuel ash and causes enhanced reactivity. An optimum replacement level of 10-20% is recommended for both rice husk ash and palm oil fuel ash incorporated concretes. Superior performance against chloride ion penetration, acid and sulphate attack is observed for palm oil fuel ash, and rice husk ash blended concretes compared with conventional concrete.

Automated summary

The disposal of agricultural waste ashes has caused severe pollution worldwide due to the rapid implementation of biomass-based power plants. However, these ashes can be effectively used as an alternative material to conventional cement. A comprehensive review on the performance of two widely available agricultural waste ashes, palm oil fuel ash and rice husk ash, in concrete is attempted. The physical, chemical, microstructural, and pozzolanic characteristics of the ashes are systematically reviewed. The optimal replacement level for both ashes in concrete is recommended. Superior performance in terms of workability and resistance against chloride ion penetration, acid, and sulphate attack is observed for the palm oil fuel ash and rice husk ash blended concretes compared to conventional concrete.