Compressive Strength of Mortars Due to Pozzolanic Reaction of Fly Ash
R. Cheerarot, J. Tangpagasit, and C. Jaturapitakkul
Appears on pages(s):
compressive strength; fly ash; ground river sand; mortar; pozzolanic reaction
The objective of this research is to study the compressive strength of mortar due to pozzolanic reaction of fly ash with different particle sizes. Fly ash and river sand which were ground to have median particle sizes of 19.4, 13.8, 6.3 pm and 20.6, 11.7, 6.4 µm, were used to replace portland cement type I at the rate of 10, 20, 30, and 40% by weight of cementitious materials to cast mortar. The pozzolanic reaction, without packing effect, of fly ash mortar is obtained from the difference of compressive strength between ground fly ash mortar and ground river sand mortar which have approximately the same particle size (19.4 and 20.6 pm, 13.8 and 11.7 µm, 6.3 and 6.4 µm) and the same replacement. The results showed that the pozzolanic reaction of fly ash mortar in-creases with the increase of fly ash fineness, age of mortar, and percent replacement of fly ash. Ground fly ash with particle sizes between 6.3 to 19.4 µm have slight packing effect on compressive strength of mortar. At early ages, the contribution to compressive strength of fly ash mortar due to pozzolanic reaction is slight, but it significantly in-creases at later ages. With 40% replacement of 6.3 pm particle size of fly ash, the compressive strength of mortar due to pozzolanic reaction at the age of 90-day is more than 50% of the total compressive strength of mortar.