Price and classification of portland cement

Honeycomb is called the architectural art of the animal kingdom, and the art comes from the joint efforts of all bees. Before the hive is built, all the bees will go out to collect materials, and then they will be brought back again and again. Finally, with the joint efforts of everyone, there is a beehive. As an intelligent human being, whether it is a blue brick house in the south or a quadrangle in the north, building is of course an art in art.

The meaning of Portland cement:

Portland cement is a kind of 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, and it can be kept in the lowest range of cement for a long time, thus increasing the stability of cement, and buildings are not easy 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. In 1756, British engineer J. Smeaton found that in order to obtain hydraulic lime, limestone containing clay must be used for firing; The most ideal composition of masonry mortar used in 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 without any ingredients. It has good hydraulic and rapid solidification 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 shaft 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 excellent architectural performance and epoch-making significance in the history of cement. In 1907, French Bie used bauxite from aluminum mine instead of clay, and mixed limestone was burned to make 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, Tangshan City, Hebei Province, 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 Neihai of Japan invented Portland cement which is not afraid of seawater. In the 20th century, while continuously improving the properties 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 Portland cement. In 2007, the annual output of cement in China was about1/kloc-0 million tons.

The General Administration of Quality Supervision, Inspection and Quarantine and the National Standardization Committee jointly issued the standard of Ordinary Portland Cement on June 9, 2007.

The standard was completed on the basis of a large number of experiments and many times of soliciting opinions. It mainly combines the previous three national standards, namely GB 175- 1999, GB 1344- 1999 and GB 12958- 1999, and it is 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 containing CaO, SiO2 _ 2, Al _ 2O _ 3 and Fe _ 2O _ 3 are ground into fine powder according to a proper proportion, and then 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 62.5r. The strength grade of ordinary portland cement is divided into four grades: 42.5, 42.5R and 52. 5 and 52. 5 r

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.

The initial setting time of ordinary portland cement, slag portland cement, pozzolanic portland cement, fly ash portland cement and composite portland cement shall not be less than 45 minutes, and the final setting time shall not exceed 600 minutes.

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 as sieve residue, and the sieve residue of 80μm square hole sieve is not more than 10% or 45μm square hole sieve 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 of holes are broken by ants, and the quality of cement greatly affects the quality of houses. In the past ten years, China has developed rapidly, but there are also fatal problems. Some time ago, the collapse of many bridges and the pits on the ground showed that these buildings had serious quality problems.

That's all about Portland cement, I hope it can help you!