Brief discussion on cement variety innovation

Editor's note: Wang Yanmou, an authority in the cement industry, and the team of the Key Laboratory of Sulfurous Aluminate Cement wrote an article entitled "On the Innovation of Cement Varieties". Compared with Portland cement

, sulphoaluminate cement and ferroaluminate cement belong to different mineral systems, which is a revolutionary breakthrough in cement technology. This breakthrough makes ferroaluminate cement have the performance advantages of seawater, saline-alkali non-corrosive and negative temperature construction, as well as outstanding energy-saving and low-carbon characteristics.

With the improvement of the testing system and the accumulation of a large number of laboratory data and engineering case testing data for more than 40 years, it has been fully shown that ferroaluminate cement has the special performance of non-corrosive in seawater, salt and alkali. What is more exciting is that over time, the intensity does not decrease but increases. It is really known as the "stainless steel" in cement. In order to become a powerful marine country,

China can not do without the construction of marine infrastructure and the support of non-corrosive cement in seawater and saline-alkali environment. The Guiding Catalogue of Industrial Structure Adjustment (2024 edition) specifies that concrete for marine engineering is encouraged. Guofa [2013] No.41 In industries with serious overcapacity, selective, focused and targeted solutions should be carried out according to the characteristics of the industry. One of the measures for the cement industry is to develop new products such as special cement to meet the needs of marine, port, nuclear power, tunnel and other projects. It is believed that aluminoferrite cement with revolutionary breakthrough characteristics of new quality productivity will play an important role in

accelerating technological innovation and industrialization by playing the role of innovative carriers such as national laboratories and national key industry laboratories! However, in the long-term use, it is found that Portland cement still has performance defects, mainly seawater corrosion, saline-alkali corrosion and the inability of negative temperature construction. In

the 1970s and 1980s, the Chinese invented sulphoaluminate cement and aluminoferrite cement, which belong to different mineral systems compared with Portland cement, as shown in Table 1.

Table 1 Main minerals

of different cement varieties

cement is usually expressed by Kn value. The Kn value is obtained by dividing the flexural strength of the specimen cured in the corrosive solution Rsolution by the flexural strength of the specimen cured in the fresh water Rwater , That is, Kn = Rliquid _/ Rwater . N is the curing age, generally 28 days, 6 months, 12 months or 24 months. The physical meaning of K value is that if the value is less than 1, it indicates that the cement sample has been corroded in the corrosive solution, and the lower the value is, the greater the degree of corrosion is; if the value is greater than 1, it indicates that the cement sample has not been corroded, and the greater the value is, the higher the strength of the cement sample in the corrosive solution is. Kn value is the most accurate index to characterize whether the cement hydration sample will be corroded or the degree of corrosion. See Table 2 and Table 3 for K values of different types of cement in typical corrosion solution.

Table 2 K6m values

of different types of cement cured in immersion water of saline-alkali land in Lop Nur region Table 3 Kn values

of different cement types cured in seawater of Dongshan Island Fall 1982, Self-stressing tubes made of Portland cement and aluminoferrite cement at the same time were placed on the beach of Xipu Bay, Dongshan Island, Fujian Province for natural exposure test. According to the investigation in 2023, the Portland cement pipe has been severely corroded, almost without strength (see Figure 1), and the internal reinforcement is seriously corroded; while the ferroaluminate cement pipe has no corrosion, and the internal reinforcement has no obvious corrosion. The strength results of cutting and sampling of the cement pipe are shown in Table 4.

Fig. 1 Comparison

of corrosion conditions of different types of cement pipes after 41 years of seawater natural exposure test Table 4 Strength values

of different types of cement self-stressing pipes after 41 years of seawater natural exposure test in Dongshan Island Different types of cement exhibit different properties because they have different hydrated mineral compositions.".

Table 5 Hydrated mineral composition

of different cement types

Liu Li: Deputy Chief Engineer of Technical Supervision and Research Center of Building Materials Industry.

He Changyu, Wang Zhiyong, Li Changcheng: Deputy Director of Key Laboratory of Sulfurous Aluminate Cement.