From: Yeon, Hyeongil
Date: 06 Nov 1999
Time: 00:54:51
I am a civil engineer. We have a problem for the cement(Raw material, bulk material) used in the prestressed concrete piles(End product, n=10,000). We will do the concrete sampling (core sampling) for the chemical tests.
As you know well, many specifications for concrete are prescription-type specification rather than end-product specifications. For the cement, there are some chemical requirements (the amount of C3A shall be less than 8% of the total weight of cement, etc.). If the chemical test were performed for the hardened concrete, we can not tell the test results for C3A is correct because of the other sources such as aggregates containing the C3A. In other words, the analysis may be very precise (duplicates may have the same results) but not very accurate depending upon other sources such as fine aggregate and admixtures. >From the test results, the amount of C3A in hardened concrete can be expected indirectly and the information will be provided to determine the conformance with contract specification.
The consumer want to use the acceptance sampling method(MIL-STD-105D) using 95% probability of acceptance. I am not familiar with the quality control method. I can not make a decisioon about the lot size of the piles. We do not have any results and documents for the above tests because it is very special. I can not tell anything about it. If we do the random sampling with small size of them, how we can conform the test results.
I'd like to get your kind answers pretty soon.
Sincerely yours,
Yeon, Hyeongil Civil/Structural Team E-mail: hiyeon@cosmos.skec.co.kr