Special cement refers to cement that has some special properties or special functions compared with general cement to meet the special needs of engineering construction in various industries. It is called the "jewel in the crown" of cement. Its birth has greatly expanded the application scope and level of cement products, and it is an indispensable basic material for major domestic projects. The development of special cement is also an important manifestation of China's cement industry to promote the supply-side structural reform, achieve high-quality development goals, cultivate new momentum for industry development, and improve the level of technological innovation in the industry. The application of multiple varieties of high-quality special cement has helped the construction of major national projects, and provided a strong support for ensuring the progress and quality of the project.

According to the "Outline of the Thirteenth Five-Year Plan for National Economic and Social Development" released in 2016, all ministries, commissions and regions across the country have put forward corresponding "Thirteenth Five-Year" plans, such as "Thirteenth Five-Year Plan". "National Science and Technology Innovation Plan", "National Marine Economy "Thirteenth Five-Year Plan", "Western Development "Thirteenth Five-Year Plan", "Thirteenth Five-Year" National Strategic Emerging Industry Development "Plan", "Energy Development "Thirteenth Five-Year Plan", "Thirteenth Five-Year" Modern Comprehensive Transportation System Development Plan, etc.

The "13th Five-Year" Development Plan for the Cement Industry issued by the China Cement Association in June 2017 also clearly stated that it is necessary to speed up product upgrades and extend the cement industry chain. Mainly include: 1) Eliminate composite 32.5 cement, encourage the production and use of 42.5 and above grade cement, and give priority to the development of special special cement (ocean, port, nuclear power, road and other projects). 2) Promote chromium-free refractories, new long-life refractories, and high-efficiency thermal insulation materials with microporous structures. 3) Accelerate the development of sand and gravel aggregates, high-performance mixed concrete, ready-mixed mortar and concrete products and other industries, and extend the cement industry chain.

These policies lead the innovation of special cement varieties, promote the high-quality development of special cement, accelerate the implementation of major engineering projects, implement new development concepts, promote supply-side structural reform, and achieve stable growth and adjustment of special cement. The structure and the short board play an important role.

The definition of special cement is classified according to the outstanding performance or use of special cement. Therefore, due to the lack of understanding of the performance of special cement in market application, the application of special cement is limited to a certain extent. The "Thirteenth Five-Year Plan" involves a number of major projects, such as: the operating mileage of high-speed railways reaches 30,000 kilometers, covering more than 80% of large cities; the mileage of newly built and renovated expressways is about 30,000 kilometers; the construction of Sichuan-Tibet railway, etc. Railway along the border; build a new airport in Beijing, and add more than 50 civil transport airports; rebuild and construct millions of kilometers of rural roads. Vigorously promote the construction of Shanghai, Tianjin, Dalian, Xiamen and other international shipping centers; improve the level of port intelligence. Build urban agglomeration traffic circles, and add about 3,000 kilometers of urban rail transit operating mileage. Start construction of 60 million kilowatts of conventional hydropower; nuclear power operating installed capacity reaches 58 million kilowatts, and over 30 million kilowatts under construction; promote the exploration and development of tight oil, oil sands, deep-sea oil, and comprehensive development and utilization of oil shale; build hydropower bases and large coal mines Electricity transmission channel outside the electric base. Construct a number of major water diversion projects, such as diverting the Yellow River to Jibudian, the Yangtze River to the Huaihe River, the Han to Wei, the Central Yunnan, the Dajihuang, and the Chuo to the Liaoning; , Zhejiang Zhuxi, Fujian Huokou, Heilongjiang struggle, Hunan Mangshan, Yunnan Agang and other large reservoirs; construction of Xijiang Datengxia, Huaihe Chushandian, Xinjiang Altash and other river basin control hub projects; basically completed the basin area of ​​3,000 square kilometers and the management of 244 important rivers above. 50 industrial bases for comprehensive utilization of industrial waste will be built, and industrial pollution sources will fully meet the emission standards.

The construction of these major engineering projects faces many unconventional engineering construction environments and engineering scales. For example, the Sichuan-Tibet high-speed railway is located in strong ultraviolet rays, large temperature difference, strong wind and dryness, high geostress, high geothermal, frequent freezing and thawing, and complex media. It is the most complex and challenging railway engineering project in human history so far, and the construction safety risk is extremely high. The crack resistance, freeze-thaw resistance and durability of construction concrete are proposed. Extremely demanding. The depth, difficulty and high cost of oil collection in my country, coupled with the extremely complex geological and geomorphological conditions in China, make the energy collection environment particularly harsh. For every 100 meters of digging, the ground temperature will increase by 2°C to 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 to 240°C. It needs to withstand pressures hundreds of times higher than the ground. The oil well cement used for cementing and pouring 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 °C to 240 °C. In the process of cement slurry pouring, it is also necessary to strictly control the setting time of the cement slurry. 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 sheath in the later stage, and the crack is gradually enlarged by the influence of the underground pressure, it is very likely to cause oil and gas leakage, and even worse, it may even cause the occurrence of malignant events such as blowout. Marine concrete is directly faced with complex conditions such as seawater erosion, lateral force driven by sea wind and wind, ocean wave scouring, marine microorganism attachment and other complex conditions, and its structural durability is challenged, such as corrosion of steel bars in concrete caused by high chloride, and expansion and cracking of concrete caused by sulfate. , the increase of concrete pores under the action of dry and wet cycles, etc., put forward extremely high requirements on the crack resistance, erosion resistance, erosion resistance and durability of concrete used in marine engineering structures; on the other hand, the concrete pouring volume reaches hundreds of cubic meters. It is a typical mass concrete, which puts forward extremely high requirements on the temperature control and crack prevention of concrete.

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

The high-quality development of special cement is not only about variety and performance innovation, but also capable of high-level large-scale and stable production to ensure the high quality of special cement products. With the improvement of production equipment and production technology level in the national cement industry, the attention and importance 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 in " During the "Thirteenth Five-Year Plan" period, not only the production scale of the single line/single plant of the special cement production enterprises has changed, but the varieties of special cement with large-scale production capacity have also increased.

3.1. Innovation of special cement varieties

In response to the engineering needs of national construction, the special cement industry continues to develop and innovate, 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:

Solved the technical problem of C2S stabilization and activation, and determined the composition of low-heat Portland cement clinker with C2S as the dominant mineral. For the first time, its precalcining kiln preparation technology was developed, which realized the low heat, high strength and high durability of cement properties, and met the technical requirements of high-performance concrete and hydraulic mass concrete. The results have achieved large-scale and stable production in many large domestic cement enterprises such as Sichuan Jiahua, Huaxin Cement, Gezhouba Cement, Xinjiang Tianshan, and Guangxi Yufeng. During the "Thirteenth Five-Year Plan" period, it was successfully applied to Wudongde and Baihetan Hydropower Stations.

2) Preparation and application of Portland cement for high-strength and medium-heat nuclear power projects

Mastered a new method of doping trace components to improve the activity of clinker minerals C3S, and realized the comprehensive properties of cement with high early strength, moderate hydration heat, dry shrinkage, etc., and stable production in 5000t/d precalciner kiln. The maximum temperature in the center of the prepared nuclear island raft-based concrete is reduced by more than 5°C, which effectively solves the contradiction between high concrete strength and low adiabatic temperature rise. The first national standard GB/T 31545-2015 "Portland Cement for Nuclear Power Engineering" was formulated. The results have achieved large-scale production in more than 10 large-scale cement enterprises in China, such as Huaihai Zhonglian, Dalian Cement and Guangxi Yufeng. It has been successfully applied to several nuclear power projects such as Yangjiang, Tianwan and Hongyanhe nuclear power plants, improving the performance of concrete in nuclear power projects, effectively reducing the thermal insulation temperature rise of concrete, and achieving good application results.

3) Preparation and application of high flexural road Portland cement

Revealed the influence mechanism of calcination regime and impurity ions on the mineral phase and activity of C4AF, optimized the composition and properties of high flexural Portland cement, and realized the synergistic development of cement flexural strength, wear resistance, dry shrinkage and other properties ; Overcome the key technical difficulties in the stable preparation of high-bending road Portland cement in large precalciner kilns, and achieved large-scale and stable production. The results have been extended to more than 10 large-scale cement enterprise groups in China, including Huaxin Cement, China United Cement, North Cement, Guangxi Yufeng, Henan Tongli, etc., meeting the needs of my country's road engineering construction. It has been successfully applied to the construction of more than 10 key projects such as roads and airport pavements in China, including the world's longest heavy-duty expressway—Inner Mongolia Zhunxing Coal Transportation Expressway, Liuzhou Bailian Airport Reconstruction and Expansion Project, etc. Engineering construction quality provides important technical support. Won the first prize of the 2018 Building Materials Industry Technology Innovation Award. …

4) Preparation and application of high-corrosion-resistant and high-toughness cement for cementing engineering

The failure mechanism of cementing cement ring isolation under high temperature and stress alternating load is clarified, and a performance evaluation method for cementing cement with high corrosion resistance and high toughness is proposed. The performance control technology of cementing slurry has been formed to solve the problem of strength decline of cementing cement under complex geological conditions, realize high corrosion resistance and high toughness of cementing cement sheath, and provide technical support for the safe and efficient development of complex oil and gas resources. The results have achieved large-scale production in many large-scale cement enterprises such as Sichuan Jiahua, Gezhouba Cement and Xinjiang Tianshan. It has been successfully applied to many oil and gas well cementing projects such as North China Oilfield and Southwest Oil and Gas Field, effectively improving the cementing quality under complex geological conditions, and the application effect is good.

5) Preparation and application of high corrosion resistant composite cement for marine engineering

By adjusting the C3S and C3A content of clinker, optimizing the auxiliary cementitious material, controlling its particle size, and adding functional adjustment components, the migration of chloride ions in the cement slurry was significantly reduced, and a high early strength, low The new generation of high-corrosion multi-component composite cement with high hydration heat, low shrinkage and good construction performance meets the needs of high-durability marine engineering structural engineering on-site pouring and mass concrete component production. It has successfully achieved industrialized pilot test and mass production in Changjiang Branch and Dongwan Branch of China Resources Cement Holdings Co., Ltd., Ningbo Kehuan New Building Materials Co., Ltd. and other enterprises. In Ningbo Zhoushan Port Main Channel Project (Zhoudai Cross-sea Bridge), Zhoushan Port Baosteel Ore Terminal Phase II Project, Ningbo Port Beilun