The "General Portland Cement" standard was jointly issued by the General Administration of Quality Supervision, Inspection and Quarantine and the National Standardization Committee on November 9, 2007. This update marked a significant step in modernizing cement specifications in China.
Developed through extensive research, testing, and public consultation, the standard integrated and improved upon three previous national standards: GB175-1999, GB1344-1999, and GB12958-1999. Key changes included adjustments to technical requirements, types and quantities of mixed materials, and the criteria for quality evaluation. Notably, the classification of cements was revised, certain types of mixed materials were introduced, and the P.O32.5 grade was removed. Additionally, the content of factory certificates was expanded to ensure better traceability and quality control.
The standard was further revised in 2009 as GB 175-2007/XG1-2009, which updated the original data and classifications from GB175-2007. Today, the "General Portland Cement" standard is based on this latest revision, ensuring it reflects current industry practices and technological advancements.
General Purpose Portland Cement
Common Portland Cement
A hydraulic cementitious material composed of Portland cement clinker, an appropriate amount of gypsum, and a specified type of mineral admixture. It is widely used in construction due to its high strength and durability.
Portland Cement Clinker
This is a finely ground material containing calcium oxide (CaO), silicon dioxide (SiO₂), aluminum oxide (Al₂O₃), and iron oxide (Fe₂O₃). It is partially melted to form a hydraulic binding substance with calcium silicates as the main component. The calcium silicate content must be at least 66%, and the mass ratio of calcium oxide to silicon dioxide should not be less than 2.0.
PO Cement
Strength Grades
Portland cement is available in six strength grades: 42.5, 42.5R, 52.5, 52.5R, 62.5, and 62.5R. Ordinary Portland cement has four grades: 42.5, 42.5R, 52.5, and 52.5R. Other types such as slag, pozzolanic, fly ash, and composite cements are categorized into three groups: 32.5, 32.5R, 42.5, 42.5R, 52.5, and 52.5R.
Setting Time
For Portland cement, the initial setting time should be no less than 45 minutes, and the final setting time should not exceed 390 minutes. For other types like ordinary, slag, pozzolanic, fly ash, and composite cements, the initial setting time is also no less than 45 minutes, but the final setting time can go up to 600 minutes.
Soundness
It must pass the boiling test, ensuring that the cement does not expand or crack after hydration.
Fineness
(Optional indicator)
Portland and ordinary Portland cements are measured by specific surface area, which should be at least 300 m²/kg. For slag, pozzolanic, fly ash, and composite cements, fineness is determined using an 80μm square sieve with a residue of no more than 10%, or a 45μm sieve with a residue of no more than 30%.
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