There are several methods to test the fineness of cement.

Cement fineness test (1) The experimental purpose passed 80? M or 45? M sieve analysis method is used to determine whether the sieve margin and fineness of cement meet the standard requirements. If it does not meet the standard requirements, the cement is considered unqualified. There are three kinds of fineness testing methods: negative pressure screening method, water screening method and dry screening method. When the results of the three tests are controversial, the negative pressure screening method shall prevail. (2) experimental instruments and equipment? Test screen: consists of a circular screen frame and a screen bottom. ? Negative pressure sieve analyzer: the negative pressure sieve analyzer consists of a sieve bottom, a negative pressure source of the negative pressure sieve and a dust collector. The sieve bottom consists of an air nozzle with a rotating speed of 30 2r/min, a negative pressure meter, a control panel, a micro motor and a housing. The adjustable range of negative pressure of sieve analyzer is 4000-6000Pa. ? Balance: the measuring range is 100g, and the sensitivity is not more than 0.01g. (3) Experimental steps 1. The test screen used in the test should be kept clean and the negative pressure screen should be kept dry. 2. Before the sieve analysis test, put the negative pressure sieve on the sieve base, cover the sieve cover, turn on the power supply, check the control system, and adjust the negative pressure to 4000-6000Pa. 3. Weight 25g(80? M sieve) or sample 10g(45? M sieve), put it into a clean negative pressure sieve, cover the sieve cover, put it on the sieve seat, and start the sieve analyzer for continuous sieve analysis for 2min. In the meantime, if the sample is attached to the screen cover, it can be tapped lightly to make the sample fall. After screening, weigh all residues with a balance. 4. When the working negative pressure is less than 4000Pa, clean the cement in the vacuum cleaner to make the negative pressure return to normal. (4) The test result is evaluated as 1, and the percentage of sieve residue of cement samples is calculated according to the following formula, and the result is accurate to 0. 1%. Where: F—— the percentage of sieve residue of cement sample (%); R quality of cement residue (g); M mass of cement sample (g). 2. Each sample should weigh two samples respectively and sieve them, and take the average value of sieve residue as the sieving result. If the absolute error of the two screening results is greater than 0.5%, the test should be repeated and the average of the two similar results should be taken as the final result. 3. When using 80? M sieve, cement sieve percentage F≤ 10% is considered as fineness qualified; When using 45? M-sieve: cement sieving percentage F≤30% means fineness is qualified.