Aggregate Fineness Modulus (ASTM C136)

FM = the sum of the cumulative percent retained on the #4, #8, #16, #30, #50, and #100 sieves, divided by 100. Cumulative retained of 2/12/32/57/82/95 sums to 280 -> FM 2.80, within the ASTM C33 concrete-sand band of 2.3-3.1. A higher FM is coarser (needs less paste); a finer sand needs more water for the same slump, and a mix's sand should not drift more than 0.20 FM without a mix adjustment. A gradation summary, not the full sieve check -- two different gradations can share an FM. A QC / mix-proportioning aid; the sieve analysis and mix design govern.

FM = (cumulative % retained on #4 + #8 + #16 + #30 + #50 + #100) / 100.

Aggregate fineness modulus (ASTM C136 sieve analysis; ASTM C125 definition; ASTM C33 concrete-sand limits), by name; the sieve analysis and the mix design govern.

FM is a defined sum of published standard-sieve retained percentages; the values come from the C136 sieve analysis of the sample.

Estimate. AHJ and licensed professional govern.

Field names used by the API: r4, r8, r16, r30, r50, r100, fm

• Contributing sieves fine-aggregate FM sums the cumulative % retained on #4, #8, #16, #30, #50, #100 (coarser sieves add 0 for a sand)ASTM C125
• C33 band concrete sand FM 2.3-3.1; drift limited to 0.20 without a mix adjustmentASTM C33