What is this blog post about?
In today's blog post, you will learn about the method of sampling of cement from bag at site (sampling of hydraulic cement).
Terminology Applied Here
1. Hydraulic Cement -: Hydraulic cement is the finely ground material which is capable of hardening by the chemical interaction of its constituents both under water and in air when the required quantity of water is added to it and is also capable of binding together appropriate materials.
2. Lot -: The quantity of cement from the same manufacturing unit and offered for inspection at one time (not exceeding 2000 tonnes).
3. Sub-Lot -: The quantity of cement in each of the parts into which a lot is divided for the purpose of sampling.
4. Increment -: The quantity of cement taken at a time by the sampling implement.
5. Gross Sample -: Sample as collected from a sub-lot, that is, the quantity of cement obtained by aggregating together all the increments from the same sub-lot.
6. Laboratory Sample -: The quantity of cement obtained by reducing the gross sample by following a specified procedure for laboratory testing.
7. Composite Sample -: The quantity of cement obtained by mixing together equal quantities of cement from each of the laboratory samples representing the sub-lots into which the lot has been divided.
Method of Sampling of Cement from Bag at Site | IS 3535
Materials used in construction projects should be of good quality and to check whether a material is standard or not, their sampling and testing are important. So learn about the method of sampling of cement from bag at site according to the standard IS 3535.
Cement Sampling IS Code
IS: 3535, this standard prescribes the methods for sampling of hydraulic cements of from bags, bulk storage (silos), ship’s hold, wagons and conveyors and also the criteria for it's conformity. Broad outlines with regard to the controls to be exercised during the manufacturing process have also been indicated.
Sampling of Cement from Bag at Site
For the purpose of sampling, the quantity of cement in the lot (consisting of a number of cement bags from the same manufacturing unit), should be divided into a number of sub-lots. The number of sub-lots into which a lot is to be divided is depends upon the weight of the lot, in accordance with following Table.
| Weight of Lot (in Tonnes) | Number of Sub-Lots |
|---|---|
| Up to 100 | 2 |
| 101 to 200 | 3 |
| 201 to 300 | 4 |
| 301 to 500 | 5 |
| 501 to 1000 | 6 |
| 1001 to 2000 | 7 |
The sub-lots should consist of approximately equal number of bags.
For drawing representative sample from a sub-lot, take sample from at least 2% of the bags subject to minimum of five. If fractional numbers are obtained, the number of bags to be selected is equal to the next higher integer.
Procedure for Random Sampling of Cement Bags from a Sub-Lot
The following procedure be followed for randomly selection of cement bag from the sub-lot.
- First of all, count the number of bags in a sub-lot. Let it be “N”.
- Then decide how many bags you need to sample (minimum 5 no. of bags should be selected).
- Divide the total no of bags (i.e. N) with the no of bags to be sampled (i.e. N/5). Let it be “n”.
- Now starting from any bag at random, count the bags in the sub-lot in one order as 1, 2, and 3 up to n and so on.
- Every nth bag so counted shall be removed.
In case the value of ‘n’ comes out to be a fractional number, its value shall be taken as equal to the integral part of it.
By the above method we shall get the number of bags from where cement samples needs to be collected for testing.
Taking Samples from Cement Bags
The procedure to collect the cement sample from the selected bags is described below.
- Choose the number of bags to be sampled from the stock in random manner (as described above).
- Samples should not be taken from broken bags.
- Insert the sampling tube diagonally into the valve of the bag and place your thumb over the air hole and then withdraw the sampling tube.
- The material may be drawn in two or three operations.
- Take approximately equal number of increments from each selected bags.
- Weight of each increment should not be less than 2 kg.
- Empty the contents of the sampling device into the container (read the procedure to store the sample described below).
- Repeat the procedure until the required quantity has been obtained.
- Close both the container and hole made by the sampling device in the mouth of the bag tightly so that no air or moisture gets into it.
- Mark each sample, showing clearly from which stock it was taken from, the date, sample number, and from where stock of the sample was taken.
Once the samples are collected by above procedure, it shall be thoroughly mixed, breaking the lumps and removing the foreign materials. It shall then be passed through 850-micron IS sieve. The foreign materials and hardened lumps that do not break on sieving or brushing, shall be discarded. Then the sample of cement has to be packed and sent to laboratory for testing. The packaging procedure is as follows.
Procedure to Store the Sample
- As increments are taken from the sub-lot, place them in a moisture proof, air-tight containers to avoid moisture absorption and aeration of the sample.
- If want to store the samples in cans, then completely fill the can and seal it immediately.
- The containers must carry suitable identification marks so that they can be related back to the particular sub-lot from which the gross sample has been taken.
Precautions to be Taken While Sampling
Following precaution to be taken while sampling of cement.
- The sampling instrument shall be clean and dry when used.
- Precautions shall be taken to protect the sample, the material being sampled, the sampling. implement and the containers for samples from adventitious contamination.
- The sample containers shall be of such a size that they are almost completely filled by the sample.
- The sample containers shall be sealed air-tight after filling and marked with full particulars of the material and the date of sampling.
- Samples shall be stored in such a manner that the temperature of the material does not vary unduly from the normal temperature.
- The place of sampling shall be clean and dry and free from draught.
FAQs
How to sample the cement at site?
Sampling of cement is done at site as per standard IS: 3535.
What is the method of sampling of cement?
The method of sampling of cement is described above in this blog post.
Why the sampling of cement is important?
Materials used in construction should be of good quality and to check whether a material is standard or not, sampling and testing is important.
