What the test tells you
- An asphalt mixture combines aggregates of different sizes, filler, and binder. Measuring their proportions helps check the mix formula and investigate deviations.
- Extraction separates binder from the mineral fraction; sieve analysis can then characterize the aggregate skeleton.
Main stages
- Homogenize and record the mass of a representative portion before testing; avoid losing fines during handling.
- Separate the binder using an extraction method validated for the material and applicable procedure.
- Separate and recover fines, dry and weigh the mineral fractions and, where the method allows, recover binder for further testing.
Reading the results
- Calculate binder content from the initial and final masses, applying the corrections required by the method.
- Plot the grading of the recovered aggregates and compare it with the job-mix formula or specified limits.
Good practice
- Control solvent recovery, sample losses, and moisture: each can bias the mass balance.
- Solvents can be hazardous. Follow their safety data sheets and laboratory procedure, including suitable extraction, protective equipment, and waste handling.
Mass balance and calculation
- Binder content: Pb = 100 · mb/M0, where M0 is initial dry mixture mass and mb is binder mass determined by the method’s mass balance, including moisture and fines corrections.
- Percent passing: P(d) = 100 − 100 · Mcum(d)/Mtotal; Mcum(d) is cumulative mass retained up to sieve d.
- Mass-balance closure: compare initial mass with the sum of recovered fractions and record the relative difference. A large loss may indicate unrecovered fines, material adhering to equipment, or incomplete corrections.
- The extraction procedure defines how to determine mb. Do not calculate binder content by simple difference when the method requires moisture, soluble mineral matter, or fines corrections.
Educational reference guide. Check the current standard, calculation assumptions, and project specification before applying a procedure or acceptance criterion.