C88 Soundness of FA

[fergie1133]

Hi,
I am researching a non-conformity from a recent fine aggregate proficiency sample. My lab has been getting a consistently higher %loss for the past 4 years (multiple technicians, virtually the same equipment). We only do this test once a year when we participate in the proficiency testing program.

Using magnesium sulfate (from the grocery store) to make the solution
Checking the SpG of the solution using a 100ml beaker and weighing it
Temperature of solution is maintained within the prescribed range
Sample fractions are held in #80 sieves, nested during soaking
Dried completely before the next soak
Nested sieves are washed with warm water after final drying period
Sieved over the same sieves at the end to determine %loss

I don't think that any of the sample is physically being lost out of the containers, I did wonder about the amount of free crystals in the solution but can't get the SpG high enough without them. Does anyone have experience with this test? Is there a variable I'm not thinking of?

 

[Ron]

Instead of using generic Epsom Salt, do a comparison with reagent grade magnesium sulphate. The grocery store variety is likely more variable