What is the percentage of the fine aggregate of fineness modulus 2.6 t...
To determine the percentage of fine aggregate of fineness modulus 2.6 to be combined with coarse aggregate of fineness modulus 6.8 for obtaining a combined aggregate of fineness modulus 5.4, we can use the concept of fineness modulus.
Fineness modulus is a measure of the fineness or coarseness of aggregates. It is calculated by dividing the sum of the cumulative percentages retained on a set of sieves by 100. The sieves used typically have openings of 4.75mm, 2.36mm, 1.18mm, 600μm, 300μm, 150μm, and 75μm.
Let's assume that the fine aggregate represents x% of the combined aggregate. Therefore, the coarse aggregate represents (100-x)% of the combined aggregate.
The fineness modulus of the combined aggregate can be calculated using the following formula:
(2.6 * x + 6.8 * (100-x))/100 = 5.4
Simplifying the equation:
2.6x + 680 - 6.8x = 540
-4.2x = -140
x = 140/4.2
x ≈ 33.33
This means that the fine aggregate should represent approximately 33.33% of the combined aggregate. Since the answer options are in terms of multiples of 10, we can round it to the nearest multiple of 10, which is 40%. Therefore, the correct answer is option C, 40%.
In summary:
- Assume fine aggregate represents x% of the combined aggregate.
- Use the given fineness modulus values and the formula to calculate the percentage.
- Solve the equation to find x.
- Round the result to the nearest multiple of 10.
- The correct answer is option C, 40%.
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