If a 6"x4" asphalt sample is cut down to smaller dimensions (let's say to prepare a DCT testing specimen), does the Gmb value change from the original bigger sample? If it does change during testing, then what might be the factors affecting this change?

  • $\begingroup$ Is it perfectly homogeneous? $\endgroup$ – Solar Mike Dec 7 '20 at 17:17
  • $\begingroup$ The sample is superpave gyratory compacted; just a routine mix design sample prepared in the lab. I don't think it is supposed to be perfectly homogeneous, in which case Gmb should be similar across different dimensions. I am curious if pavement engineers consider a different Gmb value if they cut down the sample to smaller dimensions for different testing methods. $\endgroup$ – Hanna C. Dec 7 '20 at 17:57
  • $\begingroup$ A bituminous concrete has typically 6 weight percent asphaltenes + resins + oils , so the aggregate will determine 94 % of any change . Maybe you should look into that. $\endgroup$ – blacksmith37 Dec 7 '20 at 21:03

Bituminous Materials and binders specific gravity is much less than the gravel/sand aggregate and is sensitive to ambient temperature. ( AASHTO T 228 and ASTM D 70: Specific Gravity and Density of Semi-Solid Bituminous Materials-) roughly around 1.03 versus 2.6 to 2.65 of aggregate.

So depending on the mixture of these two components that are not uniform due to the random space filled with the binders the specific gravity of smaller samples is expected to vary.

  • $\begingroup$ Thank you. Are the smaller samples expected to have lower Gmb values in comparison to the bigger sample? $\endgroup$ – Hanna C. Dec 7 '20 at 21:34
  • $\begingroup$ @HannaC. not necessarily, just bigger standard of deviation from average. they can randomly be above or below. $\endgroup$ – kamran Dec 7 '20 at 22:10
  • $\begingroup$ That explanation helps a lot. Thanks! $\endgroup$ – Hanna C. Dec 8 '20 at 2:21
  • $\begingroup$ glad I could help. please accept my answer so others can benefit from it. $\endgroup$ – kamran Dec 8 '20 at 4:56

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