Density vs specific gravity 3

[Geokhan]

What is the main difference and purpose of density and specific gravity of material in civil lab work.why not just one of them..please put some light on it other then general difinition of both..i need some extra information..advance thanks

 

[IRstuff]

Density is the mass/unit volume; as such, it's an intrinsic property of the pure material.
Specific gravity is catchall; it identifies materials that are denser than water, and it's often used as an indication of the degree of dilution of a solute, ala battery acid specific gravity.

It's all in Wikipedia

https://en.wikipedia.org/wiki/Density

https://en.wikipedia.org/wiki/Relative_density

https://www.electrical4u.com/mainte...gravity of pure,solution becomes 1.2 to 1.23.

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[GeoEnvGuy]

Soil is comprised of three things a solid, water, and air. Knowing the relationships and density of the various combinations of the three is in every geotechnical and soil mechanics textbook. The specific gravity is usually assumed by each regions geotechnical engineers and doesn't vary much between local firms. This is not usually important to measure, the exceptions to this are made fill products or tailings. The dry density and wet density are typically what is measured to determine the void ratio and relative density of materials used in construction. There is also the saturated or zero air voids density which would only apply in materials under a body of water.

As an example
A single solid sand grain has density of 2.70 t/m3 (Specific Gravity)
Granular A road base has a 100% standard proctor maximum dry density of 2.20 t/m3 (density of the solid and air only).
If measured at 5% moisture it has a wet density of (2.20 + 5%) 2.31 t/m3 (density of the soild, water, and air)
You can also determine the zero air voids density at 5% as 2.38 t/m3 (density of solid and water only)

 

[BigH]

One of the saddest experiences of my engineering career was when, in India, the government client asked the Contractor's lab manager what the specific gravity of the sand being used as fill was. He rightfully answered "just about 2.7." The client blew his top with this answer. "No, No, No. It can't be much more than 1.57!" and with that, the Lab Manager was removed from the project. The right answer to the question asked but the wrong answer to what the government client thought he asked.

 

[geotechguy1]

BigH - this reminds of the time Suncor's Engineer of Record tried to throw me off site because the impermeable fill material that was supposed to make up a water retention dam wasn't continuous. The only problem was the part it wasn't continuous was the chimney drain and I had to send a follow up email confirming that they wanted us to fill the chimney drain with clay instead of sand

 

[Geokhan]

Thanks every one

 

[BigH]

Geotechguy - crazy eh? Another India one was the use of wick drains. Usually they cut them off 300 mm or so above ground so they can"flop" - for sitting into the sand blanket. They Indian Government Client complained that he thought the wick drains were to be vertical! Perhaps someone should write an engineering comedy book on such things . . .