Marshall Corrected Flow Calculation

Summary

This article will describe how the Marshall correction for Flow are achieved.  Calculations are based on ASTM D6927.

Solution

1. Draw the tangent line if required on the Stability Flow graph.  Note the X value where Y is zero [X1].
2. Draw a second tangent line that is 1.5 mm shifted to the right of the tangent line drawn in step 1. (See section 4.13 of the ASTM).
3. Find where the second tangent line intercepts the Stability Flow curve.  Note where the X value where the second tangent line intercepts the curve [X2].
4. The corrected flow is X2 - X1 = CF.
5. The final flow is displayed via section 8.1.6 of ASTM.
   • Flow Units in INCHES:  Reported Flow (0.01\" units) = CF * 100
   • Flow Units in CM:  Reported Flow (cm) = CF * (1 / 0.0254)
   • Flow Units in MM:  Reported Flow (mm) = CF * (1 / 0.254)

Example

From the above image the CF is 6.8338 mm.

The reported from Step 5 of the solution would be to multiply the flow by 1 / 0.254.  The flow results are 26.9 mm.

Example files where this data has been pulled from are attached.  Please note example image of data has been simplified with minimal significant digits to show how calculations work.

Example files can be opened with HM Data Download software.