What are the properties of cement?

Cement Classification 1. Cement is classified according to its purpose and properties as follows: (1) General-purpose cement: The type of cement commonly used in general civil engineering projects. General-purpose cement mainly refers to the six types of cement specified in GB175—1999, GB1344—1999, and GB12958—1999, namely Portland cement, ordinary Portland cement, slag Portland cement, pozzolanic Portland cement, fly ash Portland cement, and composite Portland cement. 　　(2) Special-purpose cement: Cement designed for specific uses. For example: Grade G oil well cement, road Portland cement. 　　(3) Special-purpose cement: A type of cement with relatively outstanding properties. Such as: rapid-hardening silicate cement, low-heat slag silicate cement, expansive sulphoaluminate cement. 　　2.2 Cement is classified according to the name of its main hydraulic substance as follows: (1) Silicate cement, also known as Portland cement in foreign countries ； 　　(2) Aluminate cement ； 　　(3) Sulphoaluminate cement ； 　　(4) Ferraluminate cement ； 　　(5) Fluoroaluminate cement ； 　　(6) Cement whose main components are volcanic ash or potential hydraulic materials and other active materials. 　　3. The main technical characteristics are as follows: 　　(1) Setting speed: divided into fast-setting and ultra-fast-setting categories ； 　　(2) Heat of hydration: divided into medium and low heat categories ； 　　(3) Sulfate resistance: divided into medium sulfate corrosion resistance and high sulfate corrosion resistance ； 　　(4) Expansion property: divided into expansion and self-stress types ； 　　(5) High-temperature resistance: The high-temperature resistance of aluminate cement is classified according to the alumina content in the cement. 　　4. Principles for naming cement: Cement is named according to different categories, based on its main hydraulic minerals, supplementary materials, applications, and key characteristics; the names are intended to be concise and accurate, and abbreviations are allowed when the names are too long. 　　General-purpose cement is named by combining the name of the main hydraulic mineral in cement with the name of the supplementary material or some other appropriate name. 　　Special-purpose cement is named according to its specific use and can come in different grades. 　　Special cements are named after the main hydraulic mineral in cement, along with its key characteristics; they may also be designated by different grades or the names of mixed materials. 　　Cement whose main components are pozzolanic or potentially hydraulic materials as well as other active materials is named by combining the name of the main component with the name of the active material; it may also be accompanied by a descriptive term, such as gypsum slag cement or lime pozzolanic cement. 　　5. Definition of cement types (1) Cement: A powdery hydraulic binding material that, when mixed with water to form a plastic paste, can bind materials such as sand and stones; it can harden both in air and in water. 　　(2) Portland cement: A hydraulic binding material made by grinding Portland cement clinker, 0%~5% limestone or granulated blast furnace slag, and an appropriate amount of gypsum; it is known as Portland cement and is classified into P.I and P.II, which are the terms commonly used abroad for Portland cement. 　　(3) Ordinary Portland cement: A hydraulic cementing material made by grinding Portland cement clinker, 6%~15% supplementary materials, and an appropriate amount of gypsum; it is known as ordinary Portland cement (abbreviated as ordinary cement), with the code P.O. 　　(4) Slag Portland cement: A hydraulic cementing material made by grinding Portland cement clinker, granulated blast furnace slag, and an appropriate amount of gypsum, is known as slag Portland cement, with the code P.S. 　　(5) Pozzolanic silicate cement: A hydraulic cementing material made by grinding silicate cement clinker, pozzolanic admixtures, and an appropriate amount of gypsum. It is called pozzolanic silicate cement, code: P.P. 　　(6) Fly ash Portland cement: A hydraulic binding material made by grinding Portland cement clinker, fly ash, and an appropriate amount of gypsum, is known as fly ash Portland cement, with the code: P.F. 　　(7) Composite Portland cement: A hydraulic cementing material made by grinding Portland cement clinker, two or more specified admixtures, and an appropriate amount of gypsum, is called composite Portland cement (abbreviated as composite cement), with the code P.C. 　　(8) Moderate-heat Portland cement: a hydraulic binding material with moderate hydration heat, produced by grinding Portland cement clinker of appropriate composition along with an appropriate amount of gypsum. 　　(9) Low-heat slag silicate cement: A hydraulic binding material with low hydration heat, produced by grinding silicate cement clinker of appropriate composition along with an appropriate amount of gypsum. 　　(10) Rapid-hardening silicate cement: A cement with high early strength, made by adding an appropriate amount of gypsum to silicate cement clinker and grinding it, with its grade indicated by the 3-day compressive strength. 　　(11) Sulfate-resistant silicate cement: A cement with good resistance to sulfate corrosion, produced by grinding silicate cement clinker along with an appropriate amount of gypsum. 　　(12) White Portland cement: A white cement produced by adding an appropriate amount of gypsum to Portland cement clinker with low iron oxide content and then grinding it. 　　(13) Road Portland cement: A hydraulic cementitious material made by grinding skilled road Portland cement, 0%~10% of reactive admixtures, and an appropriate amount of gypsum, is known as road Portland cement (abbreviated as road cement). 　　(14) Masonry cement: A low-grade cement made by grinding active mixed materials along with an appropriate amount of Portland cement clinker and gypsum, and is mainly used in masonry mortar. 　　(15) Well cement: A cement suitable for use in the cementing of oil and gas wells under certain well temperature conditions, prepared by grinding silicate cement clinker composed of appropriate minerals, an appropriate amount of gypsum, and supplementary materials. 　　(16) Gypsum slag cement: A type of cement made with granulated blast furnace slag as the main component, to which an appropriate amount of gypsum, portland cement clinker, or lime has been added and ground together.

1# tristoneliu 1 Cement Grade: The cement grade is determined based on the compressive strength and flexural strength at specified ages, with the strength values expressed in kgf/cm2. The strength ages for Portland cement and ordinary cement are 3 days and 28 days, while those for slag cement, pozzolanic cement, fly ash cement, and composite cement are 3 days, 7 days, and 28 days respectively. The method for testing strength is in accordance with the \"Method for Testing the Strength of Cement Mortar\" (GB17785) (referred to as the GB method; this standard was repealed on May 1, 1999). The strengths of various types of cement are specified in nine grades: 275, 325, 425, 425R, 525, 525R, 625, 625R, and 725R. Strength grade: The strength grade of cement is also determined based on the compressive strength and flexural strength at specified ages, with the strength values expressed in MPa. The strength ages for all types of cement are uniformly set at 3 days and 28 days. The method for testing strength is carried out in accordance with the \"Method for Testing the Strength of Cement Mortar (ISO Method)\\" (GB/T 17671-1999) (referred to as the ISO method; this standard came into effect on May 1, 1999). The strengths of various commonly used cements are specified in eight grades: 32.5, 32.5R, 42.5, 42.5R, 52.5, 52.5R, 62.5, and 62.5R. The corresponding new product standards are \"Silicate Cement, Ordinary Silicate Cement\" (GB175 1999), \"Slag Silicate Cement, Pozzolanic Silicate Cement and Fly Ash Silicate Cement\" (GB1344 1999), and \"Composite Silicate Cement\" (GB12958 1999). These three standards came into effect on December 1, 1999. Taking into account the actual conditions in cement production, testing, and use, a one-year transition period has been designated. During the transition period, cement produced under both the old and new standards is used side by side, thereby ensuring a smooth transition. Designation and strength grade: The change in cement strength from designation to strength grade is mainly due to the adoption of different strength testing methods, that is, the shift from the GB method to the ISO method. This is a significant modification made to our country’s cement standards in order to bring them in line with international standards and ensure consistency with them. The two testing methods differ significantly in terms of mortar composition (standard sand, ratio of ash to sand, water-cement ratio), mixing method, compaction method, curing, loading speed, control of test conditions, and instrumentation. Through comparative testing, the test results for old-standard cement using the GB method and the ISO method showed that there was little difference in flexural strength, and the impact on the cement strength parameters was negligible ； The compressive strength tested using the ISO method is generally about one strength grade lower than that tested using the GB method. Cement labeled 425 has a strength grade equivalent to 32.5. On average, the relationship between the grade number and the strength grade is roughly 425 → Grade 32.5, 525 → Grade 42.5, and 625 → Grade 52.5. 2 Concrete grade: The concrete grade refers to the ultimate compressive strength, measured using standard testing methods after 28 days of curing, of standard test cubes with a side length of 20 cm that are prepared and cured according to standard methods; this strength is expressed in kgf/cm2. For example, in the case of concrete No. 500, the ultimate compressive strength of its test specimens is 500 kgf/cm2. When non-standard-sized specimens are used, their strength should be converted to that of standard specimens; the conversion factors are 0.95 for cubic specimens with an edge length of 15 cm, and 0.90 for those with an edge length of 10 cm. The grades of concrete are usually 150, 200, 250, 300, 350, 400, 450, 500, 550, 600. The \"Code for Construction of Railway Concrete and Masonry Structures\" (TBJ210 86) (this standard was repealed on July 1, 1997) and the \"Code for Design of Railway Bridges and Culverts\" (TBJ2 85) (this standard was repealed on February 1, 2000) both stipulate as such. Strength grade: The strength grade of concrete is determined based on the standard value of compressive strength of cubic test specimens. The standard value of the compressive strength for cubic specimens refers to a value within the overall distribution of compressive strengths measured using standard testing methods on standard cubic specimens with an edge length of 150 mm, which are manufactured and cured according to standard procedures at 28 days of age. The percentage of specimens with strengths below this value shall not exceed 5%, meaning that the guarantee level is 95%. The strength grade of concrete is indicated by the code C for concrete, along with the standard value in megapascals of the compressive strength of its cubic specimens; for example, concrete with a standard compressive strength of 50 MPa has a strength grade of “C50”. When non-standard-sized specimens are used, their strength should be converted to that of standard specimens; the conversion factors are 1.05 for cubic specimens with an edge length of 200 mm, and 0.95 for those with an edge length of 100 mm. The provisions regarding strength classification in the \"Standard for Inspection and Evaluation of Concrete Strength in Railways\" (TB10425 94) – which came into effect on April 1, 1994 – are as follows. This standard is consistent with the **\"Standard for Inspection and Evaluation of Concrete Strength\" (GBJ107 87) and the international standard \"Concrete – Classification by Strength\" (ISO3893). The strength grades of concrete are usually C15, C20, C25, C30, C35, C40, C45, C50, C55, and C60. Concrete with a strength grade of C60 and above is considered high-strength concrete. Designation and strength grade: The main differences between the two lie in two aspects. First, the sizes of the standard test specimens used are different; the side length of the cubic specimens for designations and strength grades is 200 mm and 150 mm respectively ； Secondly, there is a difference in the methods used for determining values. Strength grades have a clear statistical concept: the strength standard value is the mean value of the overall strength distribution minus 1.645 times the standard deviation (so as to ensure a confidence level of 95%). In contrast, designations do not have a clear statistical concept; it is estimated that their confidence level is around 85%. Considering the variations in standard specimen sizes and the mathematical statistical definition of strength grades, concrete grades can be approximately converted into the strength grades shown in Table 1. 3 Masonry: The masonry structures used in railway engineering buildings are mainly stone masonry and concrete block masonry. They consist of building materials such as stone (slabs, blocks, rough-hewn stones), concrete blocks and other masonry units (denoted as MU), as well as mortar used for construction (denoted as M). 3. 1 Block grade: The grade of stone is expressed as the ultimate compressive strength of a cubic specimen with an edge length of 20 cm when saturated with water, measured in kgf/cm2. For example, for stone No. 200, the ultimate compressive strength of its specimen is 200 kgf/cm2. When cubic specimens with side lengths of 7.07 cm or 5 cm are used, their ultimate compressive strength should be multiplied by conversion factors of 0.85 or 0.80, respectively. The “Code for Construction of Railway Concrete and Masonry Works” (TBJ210 86) stipulates this. Due to the lack of systematic data on the mechanical properties of stone, the conversion factors specified in relevant standards vary greatly. As specified in the **Standard for Design of Masonry Structures (GBJ373)**, when a cube specimen with an edge length of 20 cm is used as the standard specimen, the conversion factors for cubes with edge lengths of 0.7 cm or 0.5 cm are approximately 0.7 or 0.6 respectively. The common stone grades used in railway engineering are 200, 300, 400, 500, 600, 700, and 800. The grade of concrete blocks has the same meaning as that of concrete; the grades commonly used for concrete blocks in railway projects are 150, 200, 250, and 300. Strength grade: The strength grade of stone is expressed as the ultimate compressive strength, in MPa, of cube specimens with an edge length of 70 mm when saturated with water, and is denoted by the code MU. For example, in the case of MU40 stone, the ultimate compressive strength of its test specimens is 40 MPa. When using non-standard cubic specimens with side lengths of 200 mm, 150 mm, 100 mm, or 50 mm, their ultimate compressive strength shall be multiplied by the conversion factors of 1.43, 1.28, 1.14, or 0.86, respectively. The \"Code for Construction and Acceptance of Railway Concrete and Masonry Works\" (TB10210 97) stipulates this. This is also in line with the current **standard, the Code for Design of Masonry Structures (GBJ388)**. The common strength grades of stones used in railway engineering are MU30, MU40, MU50, MU60, MU70, MU80, and MU100. The strength of concrete blocks has the same meaning as the strength of concrete, but the symbol used to denote its strength should be the code for blocks, “MU”, rather than the code for concrete, “C”. The strength grades of concrete masonry commonly used in railway engineering should be MU15, MU20, MU25, and MU30. Designation and strength grade: The ultimate compressive strength measured using cubic specimens with an edge length of 200 mm represents the stone’s designation; when this value is converted to the ultimate compressive strength of cubic specimens with an edge length of 70 mm (this can be done by multiplying by the conversion factor of 1.43), it gives the stone’s strength grade. Therefore, it can be approximated as: stone grade × 1.43 = strength class. If the ultimate compressive strength of the stone, as determined using cubic specimens with an edge length of 200 mm, is 200 kgf/cm2, then the grade of this stone is 200 ； Its strength grade needs to be converted into the ultimate compressive strength of a cube specimen with an edge length of 70 mm, that is, 200 kgf/cm2 (20 MPa) × 1.43 = 28.6 MPa; thus, the strength grade is MU28.6. In practical work, when selecting the minimum strength of stone, it can be approximated that grade 200 is equivalent to MU30, and grade 400 is equivalent to MU60 ； If MU30 is used to replace No. 300, its stone strength is clearly insufficient. Although the strength of masonry structures is not in a linear proportion to the strength of the bricks, and it is also related to the strength of the mortar, sufficient attention should still be paid to this. In summary, the ratio of the stone grade to its strength class can be considered as 1:1.43. 3.2 Cement mortar grade: The grade of cement mortar is expressed as the ultimate compressive strength of cubic test pieces with an edge length of 7.07 cm, after being cured under standard conditions for 28 days, and is given in kgf/cm2. For example, in the case of cement mortar No. 200, the ultimate compressive strength of its test specimens is 200 kgf/cm2. The grades of cement mortar commonly used in railway engineering are 50, 75, 100, 150, and 200. The \"Code for Construction of Railway Concrete and Masonry Works\" (TBJ210 86) stipulates this. Strength grade: The strength grade of cement mortar is expressed as the ultimate compressive strength, in MPa, of cube specimens with an edge length of 70.7 mm after being cured under standard conditions for 28 days, and is denoted by the code M. For example, in the case of M20 cement mortar, the ultimate compressive strength of its test specimens is 20 MPa. The strength grades of cement mortar commonly used in railway engineering are M5, M7.5, M10, M15, and M20. The \"Code for Construction and Acceptance of Railway Concrete and Masonry Works\" (TB10210 97) stipulates this, in line with the provisions of relevant **standards. The required strength grade for the mortar used in railway masonry work is: M10 for main structures, and M5 for ordinary structures. Designation and strength grade: Since cement mortar is used as a bonding material in masonry work, its actual strength values exhibit considerable variability, and there is a lack of statistical data on them. Moreover, since the methods for conducting strength tests, including the dimensions of the test specimens, remain unchanged, it can generally be assumed that grade 50 corresponds to M5, grade 75 corresponds to M7.5, and so on; there is a one-to-one correspondence between the two