Special cement development report during the 13th Five-Year Plan period

The construction of these major engineering projects is faced with many extraordinary engineering construction environment and project scale, such as the harsh geological and environmental conditions along the Sichuan-Tibet high-speed railway, such as strong ultraviolet light, large temperature difference, strong wind and dry, high ground stress, high geothermal temperature, frequent freeze-thaw, complex media, etc. It is the most complex and challenging railway engineering project in human history so far. The safety risk of construction is very high, and the cracking resistance, freeze-thaw resistance and durability of construction concrete are very high. The deep depth, difficulty and high cost of oil collection in China, coupled with the extremely complex geological and geomorphic conditions in China, make the energy collection environment particularly harsh. Every 100 meters down, the ground temperature will increase by 2 ° C ~ 3 ° C, that is to say, when the well depth reaches 8882 meters (Tarim Oilfield Luntan 1 well), the oil well cement will be in a temperature environment of about 230 ° C ~ 240 ° C, in addition, it needs to withstand pressure hundreds of times higher than the ground. The oil well cement must maintain a series of complex conditions such as stable pressure, temperature, fluidity, viscosity, toughness and hardness after hardening in the huge temperature range of 0℃ ~ 240℃.

In the process of cement grouting, it is also necessary to strictly control the setting time of cement slurry, that is, to make the same cement achieve rapid solidification and forming under different temperature and pressure conditions in accordance with the specified time, the difficulty can be imagined. In addition to the difficulty of construction, the cement used in cementing needs to maintain a service life of 10 to 15 years. If there is a crack in the cement ring in the late cementing period and the crack is gradually expanded under the influence of underground pressure, it is very likely to lead to oil and gas leakage, and even lead to malignant events such as blowout. Marine concrete is directly confronted with complex conditions such as seawater erosion, lateral force driven by sea breeze and wind, ocean wave erosion, and adhesion of Marine microorganisms, and its structural durability is challenged, such as corrosion of steel bars inside concrete caused by high chlorine salts, expansion and cracking of concrete caused by sulfate, and enlargement of concrete pores under the action of dry and wet circulation. High requirements are put forward for crack resistance, erosion resistance, erosion resistance and durability of concrete used in Marine engineering structures. On the other hand, the amount of concrete poured is several hundred cubic meters, which is a typical large volume concrete, and puts forward extremely high requirements for temperature control and crack prevention of concrete.

These unprecedented engineering problems not only require a large number of high-quality special cement to ensure the smooth progress of the project and the quality of the project, but also require the variety and performance innovation of special cement to meet the comprehensive and comprehensive requirements of the project.

Third, the quality of special cement improvement

The high-quality development of special cement is not only the variety and performance innovation, but also the high level of large-scale and stable production to ensure the high quality of special cement products. With the improvement of the production equipment and production process level of the national cement industry, the attention and attention of various cement groups to special cement have increased, and the production scale and production level of special cement have also been greatly improved, especially during the "13th Five-Year Plan" period, not only the production scale of the single line/single plant of special cement production enterprises has changed. There has also been an increase in the number of specialty cement types capable of mass production.

3.1. Innovation of special cement varieties

In response to the engineering needs of national construction, the special cement industry continues to research and develop innovation, and has developed a number of new varieties, new materials and new technologies.

1) Preparation and application technology of high-strength and low-heat Portland cement:

The technical problem of C2S stable activation was solved, and the composition of low-heat Portland cement clinker with C2S as the dominant mineral was determined. The preparation technology of the pre-decomposition kiln was developed for the first time, and the cement properties of low heat, high strength and high durability were realized, which met the technical requirements of high performance concrete and hydraulic mass concrete. Results have achieved large-scale and stable production in Sichuan Jiahua, Huaxin Cement, Gezhouba Cement, Xinjiang Tianshan, Guangxi Yufeng and other large domestic cement enterprises. During the "13th Five-Year Plan" period, it was successfully applied to Wudongde and Baihetan hydropower Station, and it was the first time at home and abroad that the low-heat Portland cement dam was applied to 300-meter-level ultra-high arch dam.