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If I pour a sample of aggregate into a container full of water and measure the displacement of the water due to the sample, does this give me Bulk Volume or Solid Volume?

And what is the difference?

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Bulk volume is the total volume of void and solid material. Solid volume is the volume occupied by the solid material only, i.e. not including porosity. Phrased mathematically: $V_{bulk}=V_{void}+V_{solid}$. If an aggregate is poured into a container full of water, the displaced water reflects the solid volume only, since the space between the aggregate particles is filled with water.

As pointed out in the comments, for sufficiently fine aggregate or porous media, if air becomes trapped then the volume of liquid displaced may reflect a value between solid volume and bulk volume. Take care with how you measure.

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    $\begingroup$ This should work fine for coarse aggregate. For sand, you're going to have to pour slowly and carefully to avoid trapping air, which would lead to an incorrectly high solid volume. $\endgroup$ – Level River St Oct 26 '15 at 9:56
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    $\begingroup$ Note that this precise method works for aggregate (which was what the OP asked for) but not necessarily for concrete. Concrete once dry can create void pockets which are completely sealed from the surface, so that a part of the displaced volume measured would be due to $V_{sealed\, void}$. This usually isn't a significant portion of the volume, however. $\endgroup$ – Wasabi Oct 26 '15 at 10:04

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