Sieve analysis Flashcards
What is fineness modulus?
It is defined as the sum of the cumulative % retained on the sieves of the standard series, divided by 100.
Usually FM is calculated for fine aggr not coarse aggr.
Typical values range from 2.3 to 3, higher value indicate coarse GRADING.
What are the typical aggregate gradations?
Well-graded: Gradation near to maximum density.
Gap-graded: Gradation contains small % of aggr in the mid-size range. Curve is flat there. These mixes can be prone to segregation during placement.
Open-graded: Gradation contains small % of aggr in the small-size range. Results in more air voids as not enough small particles to fill air voids between larger particles. Curve is flat and near zero in the small-size range.
Uniformly graded: Contains most of the particles in a very narrow size range. In essence, all particles are the same size. Curve is steep and only occupies narrow size range specified.
What is mass retained?
It is the mass of the aggregates that were left on the individual sieves. So largest sieve at the top would usually have 0g.
What is % retained?
It is the % of mass of the aggregates that were left on the individual sieves. So largest sieve at the top would usually have 0%.
What is cumulative % passing?
It is the % of mass of TOTAL aggregates that has passed through all of the sieves. So the largest sieve at the top usually has 100%, and it scales down to 0% at the bottom.
The rest is calculated by 100% - cumulative % retained
What is cumulative % retained?
It is the % of mass of TOTAL aggregates that were left on all the sieves. So the largest sieve at the top usually has 0%, and it scales up to 100% at the bottom.
The rest is calculated by:
2nd sieve = 1st sieve % retained + 2nd sieve % retained
3rd sieve = 1st sieve % retained + 2nd sieve % retained + 3rd sieve % retained
etc.
What is fineness modulus?
It is defined as the sum of the cumulative % retained on the sieves of the standard series, divided by 100.
Higher FM values indicate coarse grading.
