The meaning of Portland cement:
Portland cement is a hydraulic cementing material made of silicon hydrochloric acid cement, molten limestone or blast furnace slag and gypsum. Usually, this kind of cement is ground with different kinds of calcium sulfate as additives, which is widely used in modern construction industry. This material has good air permeability, is very strong, and has good compressive and seismic properties and good stability.
Classification of Portland cement:
(1) can be divided into two types according to different components. Firstly, the purity of portland cement in the composition is higher without adding mixed materials; The other is a composite material containing limestone or blast furnace slag in portland cement, but the requirement for additives is that the content should not exceed 5% of the cement quality.
(2) According to the function of cement.
Ordinary Portland cement:? The hydration heat of this cement is about 70% of other cements, which can be kept in the lowest range of cement for a long time, thus increasing the stability of cement, and buildings are not prone to collapse or other safety accidents. Therefore, this cement will be used in the construction of large bridges, houses and entertainment equipment, and its sales account for more than 90% of the total portland cement. The price of this cement is relatively low, basically between 20 and 30 yuan.
Portland type II cement:? This kind of cement has little chemical change during use, and has strong resistance to corrosive chemical raw materials such as hydrochloric acid and sulfuric acid, but its strength is not very high. Generally used for dam construction, the price is about 100 yuan.
Portland cement history
Portland cement? -A brief history of cement development
The word "cement" is developed from the Latin caementum, which means crushed stone and flaky. The history of cement can be traced back to the mixture of lime and pozzolan used by ancient Romans in buildings, which is very similar to modern lime-pozzolan cement. After hardening, the concrete made of crushed stone cemented with it not only has high strength, but also can resist the erosion of fresh water or salt water. For a long time, as an important cementing material, it has been widely used in construction projects. 1756, British engineer J. Smeaton found that in order to obtain hydraulic lime, limestone containing clay must be used for firing; The ideal composition of masonry mortar for underwater structures is made of hydraulic lime and volcanic ash. This important discovery laid a theoretical foundation for the research and development of modern cement. 1796, an Englishman J. Parker burned a kind of cement with marl, which was brown in appearance, much like a mixture of lime and volcanic ash in ancient Rome, and named it Roman cement. It is also called natural cement because it is made of natural marl and contains no ingredients. It has good hydraulic and rapid setting characteristics, and is especially suitable for projects in contact with water. In 18 13, Gaby, a French civil engineer, found that the cement made by mixing lime and clay in a ratio of three to one has the best performance. 1824, British construction worker J. asp Ding obtained the patent right of portland cement. He used limestone and clay as raw materials, mixed them in a certain proportion, calcined the mature materials in a vertical kiln similar to lime burning, and then made cement by grinding. Because the color of hardened cement is similar to the stone used in construction in Portland, England, it is named Portland cement. It has outstanding architectural performance and epoch-making significance in the history of cement. 1907, France Bie used bauxite instead of clay and mixed limestone to burn cement. This kind of cement is called "bauxite cement" because it contains a lot of alumina.
187 1 year, Japan began to build cement plants. 1877, crampton of Britain invented rotary furnace. 1885, Langsam transformed it into a better rotary furnace. 1889, near Kaiping coal mine in Tangshan, Hebei, China, Tangshan "fine cotton soil" factory produced by shaft kiln was established. 1906 Qixin lime company was established on the basis of this factory, with an annual output of 40,000 tons of cement. 1893, Hideyoshi Endo and Sanzhen Inland Sea of Japan invented portland cement that is not afraid of seawater. In the 20th century, while continuously improving the performance of portland cement, people successfully developed a batch of cement suitable for special construction projects, such as high alumina cement and special cement. There are more than 100 kinds of cement in the world, and the annual output of cement in 2007 is about 2 billion tons. 1952, China formulated the first national unified standard, and determined that cement production should be based on the principle of multi-variety and multi-label. According to its main mineral composition, Portland cement was renamed Portland cement, and later renamed Portland cement, which is still in use today. In 2007, the annual output of cement in China was about1/kloc-0 million tons.
On June 9, 2007, the General Administration of Quality Supervision, Inspection and Quarantine and the National Standardization Committee jointly issued the standard of Ordinary Portland Cement.
The standard was completed on the basis of a large number of experiments and many times of soliciting opinions. Mainly combining the previous three national standards, namely GB 175- 1999, GB 1344- 1999, GB 12958- 1999, in terms of technical requirements.
Ordinary Portland cement is a kind of hydraulic cementing material made of Portland cement clinker, appropriate amount of gypsum and specific mixed materials.
Portland cement clinker
The raw materials, mainly CaO, SiO2 _ 2, Al _ 2O _ 3 and Fe _ 2O _ 3, are ground into fine powder in a proper proportion and burned to partial melting, thus obtaining the hydraulic cementing material with calcium silicate as the main mineral component. Wherein the calcium silicate mineral is not less than 66%, and the mass ratio of calcium oxide to silicon oxide is not less than 2.0.
Page (abbreviation of page) is called cement for short.
strength grade
The strength grade of portland cement is divided into six grades: 42.5, 42.5R, 52.5, 52.5R, 62.5R, and the strength grade of ordinary portland cement is divided into four grades: 42.5, 42.5R, 52.5r.
The strength grades of slag portland cement, pozzolanic portland cement, fly ash portland cement and composite portland cement are divided into six grades: 32.5, 32.5R, 42.5, 42.5R, 52.5R and 52.5r.
clotting time
Portland cement initial setting is not less than 45min and final setting is not more than 390min.
Ordinary portland cement, slag portland cement, pozzolanic portland cement, fly ash portland cement and composite portland cement shall have an initial setting of not less than 45min and a final setting of not more than 600min.
stability
The cooking method is qualified.
Fineness (selectivity index)
Portland cement and ordinary portland cement are expressed by specific surface area, which is not less than 300m2/kg; Slag portland cement, pozzolanic portland cement, fly ash portland cement and composite portland cement are expressed by sieve residue, and the sieve residue of 80μm square hole is not more than 10% or 45μm square hole is not more than 30%.
You may not know much about cement, because what we see is basically houses, and cement, as a semi-finished product, is basically ignored, but the ancients said it well: a thousand miles away, it collapses in an ant nest, and the quality of cement greatly affects the quality of the house. In the past ten years, China has developed rapidly, but there are also fatal problems. Some time ago, many bridges collapsed and pits appeared on the ground, which indicated that these buildings had serious quality problems.
That's all about Portland cement, I hope it can help you!