Influence of fly ash fineness and shape on the porosity and permeability of blended cement pastes |
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Authors: | Theerawat Sinsiri Prinya Chindaprasirt Chai Jaturapitakkul |
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Institution: | (1) Department of Civil Engineering, Thapar University, Patiala, 147004, India;(2) Structural Engineering, Center of Excellence for Concrete Research and Testing College of Engineering, King Saud University, Riyadh, 11421, Saudi Arabia; |
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Abstract: | The effects of the fineness and shape of fly ash on the porosity and air permeability of cement pastes were investigated.
Pulverized coal combustion (PCC) fly ash and fluidized bed coal combustion (FBC) fly ash classified into three different finenesses
were used. River sand with particle size distribution similar to that of fly ash was also used for comparison. Portland cement
was replaced with fly ash and ground sand at the dosages of 0, 20wt%, and 40wt%. A water-to-binder ratio (w/b) of 0.35 was
used throughout the experiment. The results show that the porosity and air permeability of the pastes are influenced by the
shape, fineness, and replacement level of fly ash. The porosity and air permeability of FBC fly ash pastes are higher than
those of PCC fly ash pastes. This is due to the higher irregular shape and surface of FBC fly ash compared to the spherical
shape and relatively smooth surface of PCC fly ash. The porosity increases with the increase in fly ash replacement level
and decreases with the increase in its fineness. The permeability of PCC fly ash pastes decreases with the increase in replacement
level and fineness, while for FBC fly ash, the permeability increases with the increase in replacement level. Decreases in
porosity and permeability are due to a combined effect of the packing of fine particles and the reaction of fly ash. |
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