ASTM C127 submerged weight and SSD weight?

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Discussion Overview

The discussion revolves around the ASTM C127 aggregate test, specifically addressing the differences between the submerged weight of aggregates and their saturated surface dry (SSD) weight. Participants explore the implications of specific gravity and buoyancy in this context.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions why the SSD weight is higher than the submerged weight in the ASTM C127 test.
  • Another participant references the ASTM standard, suggesting that submerged weight does not account for mass held in the pores of SSD aggregates.
  • A participant explains that specific gravity (SG) must consider buoyancy, stating that if a rock has an SG of 3 and weighs 3 tonnes, its submerged weight would be 2 tonnes due to the displacement of water.
  • There is a reiteration of the previous point about buoyancy and the disappearance of the weight of water in the aggregate when submerged.
  • A participant discusses the sensation of lightness in water, relating it to the density of the human body and the effects of lung capacity on buoyancy.

Areas of Agreement / Disagreement

Participants present differing views on the implications of specific gravity and buoyancy, with some clarifying concepts while others question the initial premise. The discussion remains unresolved regarding the relationship between SSD weight and submerged weight.

Contextual Notes

There are assumptions regarding the definitions of submerged weight and SSD weight that may not be fully articulated. The discussion also touches on the physical principles of buoyancy without resolving the underlying mathematical relationships.

goldfish9776
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in ASTM C127 Aggregate test , why the weight of SSD is higher than water submerged weight?
 
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Specific gravity, SG, of rock must have the SG of water (= 1) subtracted when rock is submerged to account for buoyancy.
If rock SG=3 and weighs 3 tonne, then when submerged in water it will weigh 2 tonne.
The weight of any water in the aggregate dissapears when it is submerged as it becomes part of the water.
 
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Baluncore said:
Specific gravity, SG, of rock must have the SG of water (= 1) subtracted when rock is submerged to account for buoyancy.
If rock SG=3 and weighs 3 tonne, then when submerged in water it will weigh 2 tonne.
The weight of any water in the aggregate dissapears when it is submerged as it becomes part of the water.
tas why we will always feel that we will be lighter when we are in the water ?
 
goldfish9776 said:
will always feel that we will be lighter when we are in the water ?
Yes.
Our body is made mostly of water. But our lungs are lighter and our bones are heavier, so our bodies have a density very close to that of water.
When we breath in, with lungs full of air we float. When we breath out, the weight of our bones sinks us. More fat makes us float better because it has a density less than water.
 

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