Sand Characteristics

[sowhatso]

Dear All ,

I am working in a water project at which we have to install water transmission ductile line and steel pipeline , in the drawings we have details for the pipe trenches , it is indicated that the bedding material is soft backfill , and it is verified in the technical specification that the soft backfill is SAND , the contractor is proposing to use the fine crushed stones or the remaining powder from the crushed stones to use it as SAND , the contactor is saying that according to the particles size the fine crushed stones can be considered as SAND. the contrcator is trying to bring the powder of the fine crushed stone because it is cheaper comparing to the SAND . From our experience the fine crushed stone can absorb water during the rain and may cause settlement and lower in the asphalt ground level.

I need to know if this fine crushed stones (powder) can be considered as SAND , and what technical information can I use to tell the contrcator that this material does not match the SAND charactersitics ???????

I know that The most common constituent of sand, is silica (silicon dioxide, or SiO2 ) and I dont think that the fine crushed stones has this material.

I need a technical help from you to know how can I reject THE fine crushed material by showing the difference between it and the SAND ...

Thanks in advance for all your inputs ...

 

[fattdad]

If you specify sand, the contractor has to give you sand. That said, you should have also specified what you mean by sand. There are ASTM Standards to define aggregates, including whether you want fine sand, coarse sand, well-graded sand, poorly-graded sand, silica sand or other. If you fail to define these parameters, it would not surprise me for a contractor to say he will provide sand-sized materials that will perform as required by the specifications.

f-d

¡papá gordo ain’t no madre flaca!

 

[cvg]

ask for the sand equivalent value for the material and ask if the sand has been washed. clean sand should be used. Cleaner aggregates will have higher sand equivalent values. Agencies often specify a minimum sand equivalent around 25 to 35 (Roberts et al., 1996).

http://www.astm.org/Standards/D2419.htm

http://www3.ntu.edu.sg/cts/tlab/005.pdf

http://training.ce.washington.edu/wsdot/modules/03_materials/03-2_body.htm

 

[BigH]

Does you spec say natural sand and deny the use of crushed sand? I would read the spec - "sand" as being material in the sand size category. Unless specifically denied, crushed sand would be permissible. Now if you don't want to permit it - after the tender and clarification meetings, etc., it is the Engineer's/Owner's right to do so - but be prepared to pay the difference. BTW, what does your spec say about compaction of the sand? (and, I am surprised that an Engineer specified "soft" sand - ouch, that hurt!!).

 

[escrowe]

SAND? Not Sand or sand?

Does your spec cite any particular classification system?

SAND sounds like the USDA textural classification for sand,
which I believe specifies 85 percent of the material falling between the #10 and #270 US Standard sieves,
and anticipates a minimum infiltration rate on the order of 8 inches per hour (confirm this!).
Requiring that could certainly impact the contractor's choice of material.
Even so, most classification systems define a SAND as predominantly sand-sized particles
falling between the #4 and #200 US Standard sieves, with less than 10% fines.

 

[sowhatso]

The specifications call for " Type C ( Sand Backfill) : Sand with 100 percent passing a 9mm sieve , at least 90 percent passing a Number 4 sieve, and a sand equivalent value not less than 30 " .

The material that contractor proposed to use as SAND is fine crushed limestone , and it is the remaining fine powder that left after crushing the stones and rockes to produce aggregates of different sizes , if you mix it with water it will be like MILK , and it is completely different when you mix the SAND with water , SAND has hard particles like silica (silicon dioxide, or SiO2 ) that keep sand with the same properties when it mixed with water.

According to specifications , maybe the fine crushed limestone will comply with the sieve size , but as amaterial , strength of material , and the chemical composition , is it enough to REFER TO the SAND EQUIVALENT VALUE to reject the proposed material?????

Is there are any technical information ( chemical and physical properties) that make the fine crushed limestone not to match the SAND properties ?????? or What is the main difference ????? if I look through the ASTM Stanbdards D422 for particle size analysis ,ASTM D2419 for stand equivilant value, and ASTM D2487 for soil clasification , can I fine something that can help in showing any major difference ?????



It was a mistake in the specification that we did not put SEA SAND instead of SAND only ......

 

[woofar]

<is it enough to REFER TO the SAND EQUIVALENT VALUE to reject the proposed material????? >

Yes!! If it fails that specification then you are out.

A few other points to consider.

Crusher dust is a wonderful product, it makes a very good bedding for pavers and concrete slabs. It can be used to make driveways and other hardstands. It can be used in many various conrete mix designs. It can also be sprinkled over your lawn as a leveller and the mineral content will give your grass a massive supercharge and green it up. However, it is generally not a good choice for pipeline bedding.

One out you may consider is the Unified Soil Classification system. Crusher dust will usually classify as a silty SAND, a silty gravelly SAND or if you are really lucky a sandy gravelly SILT. If the latter then you are out. If it is either of the other two then you could still claim that it is classifies as a silty SAND and not a SAND. You certainly wouldn't win that one in court but with a bit of bluff you might pull it off.

Of course, the best solution is to specify correctly in the first place, specify a natural sand and add a statement that manufactured sands will not be acceptable.

All up I think your best course of action would be to have it tested by a good laboratory and then put your heads together with the specification and look for possibilities.

Don't forget the possibility that it may well be servicable for your needs.

HTH
Michael

 

[Drumchaser]

It is always about money. Your contractor bid the h2o line to be bedded with sand.

is it enough to REFER TO the SAND EQUIVALENT VALUE to reject the proposed material?????

You bet!!!!!!!!!!




If this dude is trying to slip you a greasy weenie on the bedding, I would be on high alert as to his backfilling capabilities (compaction) your spec.s should require certain max thickness of lift. We spec. "to be backfilled to a density comparable to undisturbed adjacent soil."

 

[DRC1]

Sand is defined by grain size. Your specification defines sand soley by grain size. Sand does not need to be silca based. Sand is simply an errosional product of stone.Quartz sand is silica sand. Manufactured sand is common. If you need the sand to have certian properties, and yes certian sand is better than other sand for structural applications, it should be so specified. If you do not like the crushed limestone, you need to issue a change order for the material you do want.
As for Sea sand, I am not sure what that is, but if it from a marine enviornment, I would be concerned about high chloride content and effect on your pipe material

 

[dirtsqueezer]

Yeah, your spec doesn't give a lower limit for the screen size, so it could as well be clay, right? I would do as above and issue the change order. The spec is a contract to work, so your supplier might ask for a lot more money for the change, but I think it's definitely worth it in the end. Good luck!