Equipment foundation

Please refer to the Ministry of Chemical Industry standard HG/T20643 \"Specifications for the Basic Design of Chemical Equipment\"

This is an issue that civil engineering professionals need to consider.

Regarding cement grades: The new standards for general-purpose cement are GB175-1999 \"Silicate Cement, Ordinary Silicate Cement\", GB1344-1999 \"Slag Silicate Cement, Pozzolanic Silicate Cement, and Fly Ash Silicate Cement\", and GB12958-1999 \"Composite Silicate Cement\". It was officially put into effect on April 1, 2001. 　　The main revisions in the new cement standards compared to the old ones are as follows: (1) All six cement product standards adopt the method specified in GB/T17671－1999 as the method for testing strength, and the GB177－85 method is no longer used. 　　(2) The cement grade has been changed to a strength class. The six major cement standards now use strength classes expressed in MPa, such as 32.5, 32.5R, 42.5, 42.5R, etc., so that the value of the strength class corresponds to the minimum value of the cement’s 28-day compressive strength. The new standards also standardize the strength grades of cement in China. Portland cement is classified into 3 strength grades and 6 types, namely 42.5, 42.5R, 52.5, 52.5R, 62.5, and 62.5R. The other five major cement grades are also divided into 3 categories and 6 types, namely 32.5, 32.5R, 42.5, 42.5R, 52.5, and 52.5R. 　　(3) Strength age and setting of strength indicators at various ages The revisions to the six general cement standards also cover the strength age and the setting of strength indicators at different ages. The new standards for the six common types of cement specify two strength ages: 3 days and 28 days, with requirements for flexural and compressive strength at each age. (4) Other revisions: In numbering and sampling, the rule that 40,000 to 100,000 tons was classified as one code with a limit of 200 tons, and less than 10,000 tons was classified as one code with a limit of 100 tons, has been removed; instead, any amount below 100,000 tons with a limit of 200 tons is now classified as one code. Among the terms that should be clearly indicated on cement bags, the phrase “vertical kilns and rotary kilns” has been removed; the first amendment to the six new general cement standards incorporates the provisions related to “delivery and acceptance” into the main text of the standards. 　　The method for testing cement strength is an effective way to assess the mechanical properties of cement. The new standard, GB/T17671‑1999, replaces GB177‑85, and it will have a profound impact on cement manufacturers in China. It should be noted that although GB/T17671－1999 is a recommended method, it came into effect prior to May 1, 1999. Since the new mandatory standards for the six common types of cement adopt it as the method for testing cement strength, once these new standards come into effect, the GB/T17671‑1999 method becomes a mandatory one that must be followed. The implementation of the new cement standards improves the quality of cement and, at the same time, ensures the quality of construction projects. What does the grade of cement represent? 　 　　Today, cement has become an essential primary material in any construction work. If you look closely at the packaging of cement, you will see numbers such as 400, 500, 600, etc. Don’t underestimate these numbers; they each have a different meaning. 　　To build large bridges, we need high-strength cement, whereas for constructing ordinary houses, warehouses, etc., cement of higher strength is not required. Depending on different needs, products of various grades and qualities are produced. The grade of cement is its indicator of quality, and it includes the following details: 1. The strength after setting; the higher the grade, the greater the strength. Including compressive and tensile strength. 　　2. Setting speed: Types 700 and 800 are rapid-setting cements with a short setting time, used for emergency projects and underwater constructions. 　　Cement strength testing generally involves inspections at 3 days, 7 days, and 28 days of age, with different testing standards for each age period. Cement is a hydraulic cementing material; its strength increases over time, and this increase ceases after a certain period – generally, the growth in strength stops after one year. 　　In addition to being classified by various grades, cement is also distinguished by its raw materials and properties, such as slag Portland cement, pozzolanic Portland cement, and ordinary Portland cement. There are also special cements, such as acid-resistant cement, hot-water resistant cement, silicate-resistant cement, expansion cement, etc., which are named according to their properties.