(1) acceptance of sand and gravel
The acceptance of sand and gravel shall be carried out according to Quality Standard and Inspection Method of Sand for Ordinary Concrete (JGJ52-92) and Quality Standard and Inspection Method of Gravel or Pebble for Ordinary Concrete (JGJ53-92). Purchasing units should accept large tools (such as trains, cargo ships or cars) in batches according to the same origin and specifications, and accept small tools (such as carriages) in batches according to 400 cubic meters or 600 tons.
For sand, each acceptance batch should at least carry out particle grading silt content and silt content inspection. If it is sea sand, the chloride ion content should also be checked.
For stone materials, each acceptance batch shall at least carry out particle grading silt content, silt content and needle-like particle content inspection. For important projects or special projects, additional inspection items should be added according to the engineering requirements. When the quality is stable and the feed quantity is large, regular inspection can be carried out.
(2) Sampling regulations
The sampling method of each acceptance batch shall be implemented according to the following provisions:
1 When sampling on the material pile, the sampling parts should be evenly distributed. Before sampling, the surface of the sampling site should be removed, and then about equal 8 samples should be taken from each part of the sand, and about equal 15 samples should be taken from each part of the stone to form a group of samples (obtained from five different parts evenly distributed at the top, middle and bottom of the pile).
2 When sampling from the belt conveyor, it should be extracted from the tail discharge place with a feeder on a regular basis, with 4 parts of sand and 8 parts of stones respectively to form a set of samples.
3 When sampling from trains, cars and cargo ships, eight approximately equal parts of sand and 16 parts of stone should be taken at different positions and depths to form a group of samples.
4. If the inspection is unqualified, the unqualified items shall be re-sampled. If there is still a sample that can't meet the standard requirements, it will be treated as unqualified.
5 The sampling amount of sand is generally 30kg, and that of stone is 100 ~ 120kg.
6. The sampled samples should be properly packaged to avoid the loss and pollution of fine materials, and a sample card should be attached, indicating the sample number and name, sampling time, origin, specifications, sample quantity, sampling method of items to be inspected, etc.
(3) the method of sample reduction
1 Shrinkage method of sand
Using artificial quartering method, each group of samples is placed on a flat plate, mixed evenly in a wet state, and piled into a round cake with a thickness of about 200mm; Then divide the round cake into roughly equal quarters along two mutually perpendicular diameters, take two diagonal ones, mix them again, pile them into round cakes and repeat the above process until the amount of material after shrinkage is slightly more than the amount needed for the test.
For less sand samples (such as a single laboratory), dry raw sand samples can be used, but they should be carefully mixed before being divided.
Sand samples used to detect the bulk density, compaction density and moisture content of sand can be directly detected after mixing without shrinkage.
2 Shrinkage of stone
Put each group of samples on a flat plate, mix them evenly in the natural state, and pile them into a cone. Then divide the cone into roughly equal four parts along two mutually perpendicular diameters, take two diagonal parts and mix them again, then pile them into a cone, and repeat the above process until the amount of shrunk material is slightly more than the amount needed for the test. The sample package used for stone compactness inspection will not shrink, and the test will be carried out directly after mixing.
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