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Abrasion Test Results and Discussion
The compressive strengths were measured at ages 1, 3, 7, 28 and 91 days, and
are shown in Table 4-16. At early ages, fly ash concrete exhibited lower
compressive strength compared to the control mix. At the 28-day age, 30% fly
ash concrete showed peak compressive strength.
Beyond 30% cement replacement, the compressive strength decreased with an
increase in fly ash content. The compressive strength of concrete also
decreased with increasing air content. This is expected and has been reported
by earlier researchers.
Abrasion tests were performed at ages of 28 and 91 days. Abrasion
measurement using the modified method is a relative indicator of abrasion and
is reported in Tables 4-17 and 4-18. Abrasion wear decreased with an increase
in specimen age and resulting increased strength.
Concrete mixtures of up to 30% cement replacement by fly ash had abrasion
resistance similar to that for fly ash concrete produced without fly ash.
Beyond 30% cement replacement, abrasion resistance decreased. It can also
be said that with the decrease in compressive strength, abrasion resistance
decreased (abrasion wear increased).
The above work leads to the following key conclusions:
1. Concrete containing up to 30% cement replacement by fly ash exhibited
similar or better compressive strength when compared to concrete
produced without fly ash, at ages of three days and beyond
2. (See Figure 4-8).
3. Compressive strength is the key factor affecting abrasion resistance.
Stronger concrete mixtures exhibited higher resistance to abrasion
4. (See Figure 4-9).
5. Effect of air content on abrasion resistance of concrete was insignificant
within the tested range.
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Coal Combustion Products
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