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

Special cement refers to cement that has some special properties or special functions compared with general cement and aims to meet the special needs of engineering construction in various industries, and is known as the "pearl on the crown" of cement. Its birth has greatly expanded the application range and level of cement products, and is an indispensable basic material for major domestic projects. The development of special cement is also an important embodiment of China's cement industry to promote supply-side structural reform, achieve high-quality development goals, cultivate new momentum for industry development, and enhance the level of scientific and 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 guaranteeing the construction progress and quality of projects.

I. National demand and industry policy during the 13th Five-Year Plan period

According to the Outline of the 13th Five-Year Plan for National Economic and Social Development released in 2016, various ministries and commissions and regions across the country have put forward corresponding 13th Five-Year plans. Such as the "13th Five-Year Plan for National Science and Technology Innovation", "13th Five-Year Plan for National Marine Economy", "13th Five-Year Plan for Western Development", "13th Five-Year Plan for National Strategic Emerging Industry Development", "13th Five-Year Plan for Energy Development", "13th Five-Year Plan for Modern Comprehensive Transportation System Development" and so on.

In June 2017, the "13th Five-Year" development Plan for the cement industry released by the China Cement Association also clearly stated that: accelerate product upgrading and extend the cement industry chain.

It mainly includes:

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 (Marine, port, nuclear power, road and other projects).

2) Promote chromium-free refractories, long-life new refractories, and high-efficiency thermal insulation materials with microporous structures.

3) Accelerate the development of sand aggregate, high-performance mixed concrete, ready-mixed mortar and concrete products and other industries to extend the cement industry chain.

These policies lead the variety innovation of special cement, promote the high-quality development of special cement, and play an important role in accelerating the implementation of major engineering projects, implementing the new development concept, promoting the supply-side structural reform, and achieving the steady growth of special cement, adjusting the structure and making up for shortcomings.

2. Innovation and high-quality development of special cement

The definition of special cement is classified according to the outstanding performance or use of special cement, so there is a certain degree of limitation in the application of special cement due to the lack of understanding of the performance of special cement in the market.

The 13th Five-Year Plan involves a number of major projects, such as: the operating mileage of high-speed railways has reached 30,000 kilometers, covering more than 80% of big cities; About 30,000 kilometers of newly built or upgraded expressways are open to traffic. Construction of Sichuan-Tibet railway and other border railways; Beijing's new airport will be completed, and more than 50 new civil transport airports will be built. We will renovate and build a million kilometers of rural roads. Vigorously promote the development of Shanghai, Tianjin, Dalian, Xiamen and other international shipping centers; We will raise the level of port intelligence. We will build urban agglomeration transportation circles, and increase the operating mileage of urban rail transit by about 3,000 kilometers.

Construction of 60 million kilowatts of conventional hydropower began; The installed capacity of nuclear power plants in operation will reach 58 million kilowatts, and those under construction will reach more than 30 million kilowatts. Promote exploration and development of tight oil, oil sands, deep-sea oil and comprehensive development and utilization of oil shale; Construction of hydropower bases and large coal power base external power transmission channels. Construction of a number of major water diversion projects, such as the Yellow River to Budian Lake, the Yangtze River to Huaihe River, the Han River to Wei River, the central Yunnan River to Huang River, the Chuo River to Liao River. Promoting the follow-up construction of the East-Central Route of the South-to-North Water Diversion Project; The construction of Laluo in Tibet, Zhuxi in Zhejiang, Huokou in Fujian, Fengfeng in Heilongjiang, Mangshan in Hunan, Agang in Yunnan and other large reservoirs; Construction of river basin control hub projects such as Xijiang Dateng Gorge, Huai River Outlet and Xinjiang Altashe; We have basically managed 244 major rivers with a drainage area of 3,000 square kilometers or more. We will build 50 industrial bases for the comprehensive utilization of industrial waste, and discharge all industrial pollution sources up to standards.

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.

2) Preparation and application of Portland cement for high-strength medium-thermal nuclear power engineering

The new method of doping trace components to improve the C3S activity of clinker minerals was mastered, and the comprehensive properties of cement such as high early strength, medium hydration heat and dry shrinkage were realized, and the stable production was achieved in the 5000t/d pre-decomposition kiln. The maximum temperature of the raft concrete center of the nuclear island is reduced by more than 5℃, which effectively solves the contradiction between high strength and low adiabatic temperature rise of concrete. The first national standard for cement used in nuclear power engineering construction GB/T 31545-2015 "Portland Cement for Nuclear Power Engineering" has been formulated. The results have been achieved in Huaihai Zhonglian, Dalian Cement and Guangxi Yufeng more than 10 large cement enterprises scale production. It has been successfully applied in many nuclear power projects such as Yangjiang, Tianwan and Hongyanhe nuclear power plants, which has improved the performance of concrete in nuclear power engineering, effectively reduced the adiabatic temperature rise of concrete, and achieved good application results.

3) Preparation and application of Portland cement with high bending resistance

The influence mechanism of calcination system and impurity ions on the mineral phase and activity of C4AF was revealed. The composition and properties of Portland cement with high bending resistance were optimized, and the bending strength, wear resistance and dry shrinkage of cement were realized. The key technical problems of stable preparation of Portland cement with high bending resistance in large-scale pre-decomposition kilns have been overcome, and large-scale stable production has been achieved. The results have been extended to more than 10 domestic large cement enterprise groups, such as Huaxin Cement, Zhonglian Cement, Northern Cement, Guangxi Yufeng, Henan Tongli, etc., to meet the needs of road engineering construction in China. It has been successfully applied in the construction of more than 10 domestic key projects such as roads and airport pavement, including the world's longest heavy-duty highway - Inner Mongolia Junxing Coal Transport Expressway, Liuzhou Bailian Airport reconstruction and expansion project, etc., providing important technical support for ensuring the quality of road engineering construction in China. Won the first prize of the 2018 Building Materials Industry Technological Innovation Award. ...

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

The failure mechanism of cementing cement ring seal under high temperature and stress alternating load is expounded, and the evaluation method of high corrosion resistance and high toughness cementing cement cement performance is proposed. The cement cement performance control technology has been formed to solve the problem of strength decline of cement cement under complex geological conditions, achieve high corrosion resistance and high toughness of cementing cement ring, and provide technical support for the safe and efficient development of complex oil and gas resources. The results have achieved large-scale production in Sichuan Jiahua, Gezhouba Cement and Xinjiang Tianshan Cement enterprises. 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 composite cement with high corrosion resistance for Marine engineering

By adjusting the C3S and C3A content of clinker, selecting auxiliary cementing materials and controlling their granularity, adding functional adjustment components, the migration of chloride ions in cement slurry is significantly reduced, and a new generation of high-corrosion resistance multi-component composite cement with high early strength, low hydration heat, low shrinkage and good construction performance is successfully developed. It can meet the needs of high durability Marine structural engineering casting and mass concrete component production. It has successfully achieved industrial 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. It has been successfully applied in Ningbo Zhoushan Port main passage project (Zhoudai Cross-sea Bridge), Zhoushan Port Baosteel Ore Terminal Phase II project, Ningbo Port Beilunshan multi-purpose hydraulic engineering project, Guangdong Shenzhen-China Passage project (steel shell submerged tube prefabrication) and other projects.

3.2. Changes in production scale

By the end of 2020, there are about 3,440 certified cement enterprises (effective production licenses) in the country, of which about 250 enterprises have special cement production capacity, and the vast majority of special cement production enterprises can also engage in the production of general cement. The maximum clinker capacity of a single production line of special cement has now been increased to 5,000 t/d (kiln diameter is 4.8m), and the overall annual capacity has reached 50 million tons. Among them, the major cement groups have laid out special cement production lines, such as Conch Group, China Building Materials, Tianshan Shares, Huaxin cement, Jilin Yatai, Beijing BBMG, Qilian Mountain, etc., consistent with the trend of increasing industry concentration in the cement industry.

Fourth, continue to build a standard system

In order to support the continuous R&D innovation and high-quality development of the special cement industry, the standard system of special cement is also continuously updated, for innovative special cement varieties, formulate national/industry standards, for the quality improvement of existing varieties, revise national/industry standards, and improve the corresponding technical requirements and testing methods. From 2016 to 2020, a total of 5 national standards have been formulated and 4 national standards revised; Completed building materials industry standard formulation 1, building materials industry standard revision 1. As of December 2020, 3 national standard systems/revisions and 3 building materials industry standard systems/revisions are being carried out.

Five, carbon neutral carbon emission and low-carbon special cement varieties

The main CO2 emission sources in cement production are:

1) Carbonate decomposition in raw materials;

2) Combustion of fuel;

3) Power consumption of each process equipment.

About 60% of the CO2 emitted in the production of general purpose Portland cement comes from carbonate decomposition, and about 40% comes from fuel combustion and power consumption. The C3S mineral content in general Portland cement clinker is generally about 60%, and because the C3S firing temperature is higher, and the proportion of calcium carbonate in the ingredients is larger, the production energy consumption is higher, and the emissions of CO2 and NOx are also larger. Therefore, to achieve the low-carbon production of cement, the following two technical approaches can be adopted:

First, reduce the amount of CO2 generated by energy consumption, that is, within the scope of the general Portland cement system and its mineral composition, improve the production process and equipment level by regulating the flammability and grindability of raw materials, and reduce the energy consumption of the cement production process;

The second is to reduce the amount of CO2 produced by carbonate decomposition, that is, break through the limitations of the existing Portland cement clinker mineral system and its mineral composition range, reduce the content of high calcium minerals and increase the content of low calcium minerals or introduce other low calcium mineral components, and research and develop a new low-carbon cement system.

At present, the cement industry in the first way has made good progress, a series of energy saving and emission reduction technology has been widely used, under the existing technology conditions, relying on process technology and equipment level transformation to further achieve energy saving and emission reduction has been very difficult, and the research and development of low-carbon cement varieties has become a hot spot in the field of cement material science.

Low-carbon special cement products mainly include:

1) High Belite Portland cement (low-heat Portland cement, referred to as "low-heat cement");

2) sulfoaluminate (ferric) cement;

3) Portland cement with low clinker coefficient and specific properties, that is, Portland cement clinker, special Portland cement made by mixing materials with specific properties, the mixing amount of mixed materials can be up to 70%, such as slow setting Portland cement for road base, Marine Portland cement, low-heat micro-expansion cement, etc.

Sixth, the "14th Five-Year Plan" period of special cement industry challenges and opportunities coexist

The 14th Five-Year Plan period is the first five years in which China, after completing the building of a moderately prosperous society in all respects and achieving the first centenary goal, embarked on a new journey to fully build a modern socialist country and march toward the second centenary goal. "14th Five-Year Plan" period of special cement industry challenges and opportunities coexist.

1. From the perspective of challenges:

Cement industry is still resource-based, high energy consumption and consumption of environmental resources more industry, the state advocates the concept of green development, emphasizing that "green water and green mountains is gold and silver mountains". As part of the cement industry, special cement also has social responsibility requirements and also faces the same or even more stringent challenges.

(1) The future environmental requirements will be more stringent on the existing basis, a number of provinces and autonomous regions have issued ultra-low emission policy requirements, and special cement will no longer enjoy special treatment, technology, equipment, environmental protection and other requirements have reached the advanced level of the industry, as the entire industry is facing "carbon peak" "carbon neutral" tremendous pressure.

(2) The difficulty and cost of obtaining resources are getting higher and higher. Mine acquisition cycle is long, many links, complicated procedures, more and more difficult, and mine resources continue to auction high prices, the cost of resources will be higher and higher.

(3) It is increasingly urgent to eliminate backward production capacity. Since the resources required by special cement are better than that of general cement, it is necessary to reduce the energy consumption per unit of product, improve resource utilization, improve quality and market competitiveness.

2. From the perspective of opportunity:

(1) The epidemic objectively extended the plateau period of cement demand. According to the national economic situation, the government will still maintain a high intensity of infrastructure investment during the "14th Five-Year Plan" period, and the demand for cement is generally stable. The extraordinary construction environment and project scale will bring more opportunities for the application of special cement.

(2) "carbon peak" and "carbon neutrality" promote industry restructuring, accelerate the exit of small and medium-sized enterprises, and provide opportunities for large enterprises to merge and reorganize and improve industry concentration.

(3) With the promotion of "The Belt and Road", special cement will have the opportunity to support China's overseas engineering construction projects, providing opportunities for large enterprises to implement internationalization strategies.