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Strength grade of cement grade

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the new standard of general cement is general Portland cement (GB175-2007). Issued on November 9, 2007 and officially implemented on June 1, 2008. This standard replaces the three standards of gb175-1999 Portland cement, ordinary portland cement, gb1344-1999 slag Portland cement, pozzolanic Portland cement and fly ash Portland cement and gb12958-1999 composite Portland cement since the date of implementation
about cement grade
the strength grade of cement is the sign of cement strength. The measurement index is the compressive strength of cement, and the detection standard is mainly the strength of cement mortar after hardening for 28 days. For example, if the compressive strength after 28 days is 42.5mpa, the strength grade of cement is 42.5 or 42.5 R. Cement has eight strength grades: 32.5, 32.5R, 42.5, 42.5R, 52.5, 52.5r, 62.5 and 62.5r. The strength grade band r indicates that the cement is early strength cement. The strength grade of 32.5 and 32.5R can be used in some buildings. Those with strength grade above 42.5 can be used to build larger bridges or factories, as well as some important pavements and manufacture prefabricated components
in fact, there are no very detailed regulations on the use of cement strength grade. Generally speaking, clear regulations will be given in the design drawings
ordinary portland cement and slag Portland cement are commonly used in civil construction projects
the commonly used strength grades are P.O 42.5 and P.S 32.5 /42.5
250-300 yuan for strength grade 32.5 and 360-450 yuan for strength grade 42.5. Different brands and regions lead to different prices. Compared with gb175-1999, gb1344-1999 and gb12958-1999, the main changes of this standard are as follows:
— the full text is mandatory and the provisions are mandatory (preface of this edition)
— the definition of general Portland cement is added (Chapter 3 of this edition)
— cancel the definition of various types of cement (Chapter 3 of the original gb175-1999, gb1344-1999 and gb12958-1999)
— combine components and materials into one chapter (Chapter 4 of the original version of gb175-1999, gb1344-1999 and gb12958-1999 and Chapter 5 of this version)
— in ordinary portland cement, “when mixing active mixed materials, the maximum mixing amount shall not exceed 15%, in which kiln ash of no more than 5% of cement mass or inactive mixed materials of no more than 10% of cement mass are allowed to replace” is changed to “The addition amount of active mixed materials is & gt; 5% and ≤ 20%, in which it is allowed to be replaced by inactive mixed materials not exceeding 8% of cement mass and meeting article 5.2.4 of this standard or kiln ash not exceeding 5% of cement mass and meeting article 5.2.5 of this standard” (article 3.2 of the original version of gb175-1999 and Article 5.1 of this version)
— change the slag content in slag Portland cement from “20% ~ 70%” to “& gt; 20% and ≤ 70%”, and divide it into type A and type B. Type a slag content & gt; 20% and ≤ 50%, code p.s.a; Type B slag content & gt; 50% and ≤ 70%, code p.s.b (Article 3.1 in the original version of gb1344-1999 and Article 5.1 in this version)
— change the content of pozzolanic mixed material in pozzolanic Portland cement from “20% ~ 50%” to “& gt; 20% and ≤ 40%” (article 3.2 in the original version of gb1344-1999 and Article 5.1 in this version)
— change the total addition amount of mixed materials in composite Portland cement from “shall be greater than 15%, but not more than 50%” to “& gt; 20% and ≤ 50%” (Chapter 3 of the original gb12958-1999, Article 5.1 of this edition)
— granulated blast furnace slag powder is added to the material (articles 5.2.3 and 5.2.4 of this edition)
— the mixed materials such as granulated refined ferrochrome slag, granulated calcium increasing liquid slag, granulated carbon ferrochrome slag and granulated blast furnace titanium slag and the newly developed mixed materials in accordance with Appendix A are cancelled in the composite Portland cement, and Appendix A is cancelled (articles 4.2, 4.3 and Appendix A in the original gb12958-1999)
— class m mixed gypsum is added and class a anhydrite is cancelled (Chapter 3 of the original gb175-1999, gb1344-1999 and gb12958-1999, article 5.2.1.1 of this edition)
— the allowable mixing amount of grinding aid is changed from “no more than 1% of cement quality” to “no more than 0.5% of cement quality” (Article 4.5 in the original version of gb175-1999, gb1344-1999 and gb12958-1999 and article 5.2.6 in this version)
— 32.5 and 32.5R are cancelled from the strength grade of ordinary cement (Chapter 5 in the original gb175-1999 and Chapter 6 in this edition)
— change “magnesium oxide content in clinker” into “magnesium oxide content in cement” in slag Portland cement, pozzolanic Portland cement, fly ash Portland cement and composite Portland cement, in which the magnesium oxide content in p.s.a, P.P, P.f and P.C cement is required to be no more than 6.0%, and add B to explain that “if the magnesium oxide content in cement is more than 6.0%, cement autoclave test shall be carried out and qualified”; P. No requirement for S.B type. (Article 6.1 of original gb1344-1999 and gb12958-1999, Article 7.1 of this edition)
— the requirement of chloride ion limit is added, that is, the chloride ion content in cement is no more than 0.06% (Article 7.1 of this edition)—— Change the strength index of ordinary portland cement of each strength grade to be consistent with Portland cement, and change the strength index of composite Portland cement of each strength grade to be consistent with slag Portland cement, pozzolanic Portland cement and fly ash Portland cement (article 6.6 in the original version of gb12958-1999 and article 7.3.3 in this version)
— increased by 45 μ The sieve residue of m square hole sieve shall not be greater than 30% as the selectivity index (article 7.3.4 of this edition)
— the principle of selecting cement component test method and regular verification requirements are added (Article 8.1 of this edition)
— expand the applicable cement varieties specified in “water consumption shall be determined according to the water cement ratio of 0.50 and the fluidity of mortar not less than 180mm” to pozzolanic Portland cement, fly ash Portland cement, composite Portland cement and ordinary portland cement mixed with pozzolanic mixed materials (article 7.5 of the original version of gb1344-1999 and article 8.5 of this version)
— the annual production capacity “200” is added to the number and sampling × Above 104t “, i.e. 200 × More than 104t and no more than 4000t are a number; Replace “more than 1.2 million tons and no more than 1200 tons as a number” with “120” × 104t~200 × 104t, no more than 2400t is a number “(Article 8.1 in the original version of gb175-1999, gb1344-1999 and gb12958-1999, Article 9.1 in this version)
— replace “the ex factory cement shall ensure the ex factory strength grade, and other technical requirements shall meet the relevant requirements of this standard” with “the cement can be delivered only after it is confirmed that the technical indexes and packaging quality of the cement meet the requirements” (Article 8.2 in the original version of gb175-1999, gb1344-1999, gb12958-1999 and article 9.2 in this version))
— the waste judgment is cancelled (Article 9.3 of the original gb175-1999, gb1344-1999 and gb12958-1999)—— The provisions on fineness and mixing amount of mixed materials are cancelled in the determination of nonconforming products, The judgment rule is changed to “if the inspection results meet the technical requirements of articles 7.1, 7.3.1, 7.3.2 and 7.3.3 of this standard, they are qualified products. If the inspection results do not meet any of the technical requirements of articles 7.1, 7.3.1, 7.3.2 and 7.3.3 of this standard, they are unqualified products. (article 8.3.2 in the original version of gb175-1999, gb
1344-1999 and gb12958-1999, article 9.4.1 and 9.4.2 in this version);
— other technical requirements agreed in the contract are added to the inspection report.” (article 8.4 in the original version of gb175-1999, gb1344-1999 and gb12958-1999 and article 9.5 in this version)
— in delivery and acceptance, added “the stability arbitration inspection shall be completed within 10d from the date of sampling” (article 9.6.2 of this edition)—— In the packaging mark, “and shall not be less than 98% of the mark quality” is changed to “and shall not be less than 99% of the mark quality” (Article 9.1 in the original version of gb175-1999, gb1344-1999 and gb12958-1999 and article 10.1 in this version)
— in the packaging mark, “the two sides of pozzolanic Portland cement, fly ash Portland cement and composite Portland cement packaging bag are printed in black” is changed to “the two sides of pozzolanic Portland cement, fly ash Portland cement and composite Portland cement packaging bag are printed in black or blue” (article 9.2 of the original gb1344-1999 and gb12958-1999, article 10.2 of this edition). The equivalence between the strength grade of new cement and the grade of old cement is shown in the following table
cement grade
cement strength grade
gb175-1999
GB175-2007
725 (R)
62.5 (R)
625 (R)
52.5 (R)
525 (R)
42.5 (R)
425 (R)
32.5 (R)
the implementation of the new standard of cement not only improves the quality of cement, but also ensures the quality of construction projects

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