Sand Smpling Protocol 3

[nyuma704]

I am supposed to write up a sand sampling protocol, on how the sand should be checked when it gets to site. What tests need to be done (sieve analysis). What i need to state out clearly who is responsible for what?

 

[msucog]

i suppose it depends on what you're attempting to do and how critical it is to test. why are you testing (what is the purpose)?

astm would be a good place to start. keep in mind that a test is just that...it's NOT an "absolute" of what is there. if you need higher confidence that the results are representative of what is there, then increase the testing frequency. yes, state who should deliver the material, perform the testing, and who is responsible for the end result. the testing firm is responsible for performing the testing and will provide test results. the contractor is typically responsible for the "end product" and it's performance. the engineer does the design.

 

[concretemasonry]

Definitely follow the ASTM standards for testing referenced in the ASTM material standard. Depending on the use, moisture can be a major factor since sand can carry a significant amount of water (1% to 10%, depending on gradation and previous exposure)and it and will lead to changes in batching weights. Aggregate sampling can be tricky. Much depends on the the methods of landling and stockpling.

If it is bulk onsite, avoid the bottom or outside of a pile. Dig into the pile up a ways so you get sample with a typical representative sand. The outside and top of the piles dry out and can seggregate more. If the sand will be used for concrete, the bottom and ouside will give you false moisture content and batch weights. Take a good sized sample and split/quarter it.

If it is on a conveyor (like a permanent or on-site concrete batch plant), it is much easier to get a representative sample. There are sample cutters to cut to get a cross esction on a belt when you stop it for a few seconds. Avoid sampling directly out of a bin where sand has been stored for a period of time since the moisture drains down and gives a false reading (like the first load of concrete in the morning).

In the dark ages,when I was sampling aggregate (stored in covered bins) for concrete, we would always take sand samples late the previous day to avoid the false samples from the bottom early in the morning. When you have an 800 yard pour starting at 5:00 AM, it also provides a better start.

I assume you are looking mainly at gradation variation for uniformity control. If you are looking at prliminary acceptance there are other tests that must be done before you get going.

Dick

 

[BigH]

I think a lot depends on what you are using the sand for - this will determine the testing that you might need to do. Such required testing that comes to mind - sieve analysis, moisture content, absorption (if used for concrete, along with clay lumps, organic impurities, specific gravity, and other tests specified for fine aggregate). If using the sand for backfill to MSE walls, you might require testing for resistivity. You might wish to search the web for construction specifications from various State DOTs, or other agencies (depending on country) to see what testing that they require for the sand being used in similar circumstances.
While ASTM certainly has all the various testing procedures you would use once you have decided on the types of testing (based on specified properties), you might not be in the United States and other codes for the actually testing procedures might need to be followed (i.e., Eurocode, Indian Standards, etc.). As an international forum, keep in mind that it isn't always ASTM.

 

[nyuma704]

Thank you all for your prompt responses. Just to give you a bit of more background on my problem.

My firm designed a hazardous landfill site (larox - a manganese by product) and it was constructed late 2005 and came in operation in 2006. However it was later discovered that the leakage flow rates reporting to the manholes were very high. It was caused by the fact that the sand layer that is supposed to act as a filter layer on top of the liner system was not to the design spec. We then had some of this sand removed on 2 of the cells, and started to look for the proper sand again that fits the design spec. We have found it, however it was suggested that we use it with a geotextile to achieve the right filtration.
I am then tasked to write up a quality assurance protocol on how the sand should be tested (which will be sieve analysis only), how much per load truck i should sample, and when exactly to take the samples, before or after placing on liners, what to do in an event of failure, i.e the sand does not fit the design spec, how much sensivity analysis can i allow etc

I hope this is much clearer. Your help will be greatly appreciated.

 

[muuddfun]

Filters are always tricky to maintain the right gradations. Specify the gradation band you want and test both the material at the source and at the cell after placement. It is very hard to get out once you have placed sand that is out of spec. Do not forget that the sand will break down in the trucks as it is transported to the site and as it is compacted in place. So you will have to figure out what your taget gradation is at the source to end up with the specified sand in place after all work is accomplished. Depending on the source and type of material that makes up your sand you can loose 1 to 2 percent of the sieve size on a number of the sieves from transportation and handling (i.e. you start with 30 percent passing the no. 40 and you end up with 32 percent passing the no. 40).