Cement production requires non-renewable natural resources that will be depleted in
coming years. An alternative needs to be found to promote sustainable development
for the construction industry. Therefore, this study introduced Pennisetum Purpureum
ash (PPA) as a natural pozzolan. Limited information was published on the influence
of PPA particle size in cement products. Therefore, this study investigated the
physical and chemical properties of PPA as a cement replacement material and the
effects of particle sizes of PPA with different replacement percentages on
compressive strength and water absorption of cement mortar. The morphology of
mortar containing PPA was also analysed. The PPA was prepared through controlled
burning and grinding process before going through particle size analysis, XRF and
SEM. The PPA used were ground for 1 hour (1H-PPA), 3 hours (3H-PPA) and 6
hours (6H-PPA) while the percentage of replacement in mortar were 5%, 10%, 15%,
and 20%. The mortar was cured for 3, 7 and 28 days for mechanical properties
characterisation. It was found that the particle size of PPA decreased as the time of
grinding increased, which also increased the surface area. The particle size for 1HPPA,
3H-PPA and 6H-PPA were 9.30μm, 10.25μm and 10.58μm respectively. The
total reactive oxides for 1H-PPA, 3H-PPA and 6H-PPA were 38%, 37% and 41.1%
respectively while the loss on ignition were above 5%. As a conclusion, the grinding
process degraded the honeycomb-like PPA structure into smaller particle size with
highly irregular shape but in better dispersion. The 15% replacement of 6H-PPA
mortar at 28 days showed the significant performance (30.07 N/mm2 of strength) with
increment strength by 43.74% compared to control mortar with the lowest water
absorption rate of 8.2%