Abstract:
The success of preplaced aggregate concrete technology depends on two main
factors which are potential grout and coarse aggregate. This research was conducted
experimentally to determine the effect of using two different fly ash sources as an alternative
for the partial replacement of cement and several size and shapes of coarse aggregate on the
compressive and tensile strength of PAC specimens. This involved the use of seven concrete
mixes with a low water-cement ratio of 0.4 and cement to sand ratio of 1:0.75 to produce
standard cylinder specimens of concrete containing rounded and crush aggregate. Moreover,
fly ash was added at a dosage of 5% and 10% of cement weight while three shapes and sizes of
a rounded and crushed aggregate at 20 mm, 30 mm, and a mixture of the two were also
applied. The results showed the compressive strength of specimens with different sizes or a
mix of rounded aggregate in PAC exhibited a similar performance with 30 mm of crushed
coarse aggregate. Furthermore, the specimen with a higher content of calcium fly ash
demonstrated a more rapid strength at an early age of seven days than those with lower content.
Therefore, the partial replacement of cement with industrial waste material in the form of fly
ash in preplaced aggregate concrete has the ability to save up to 10% of cement and also
produce certain environmental benefits.
