Abstract
This paper mainly introduces the history of the formation and development of an ultra-high performance low-carbon waste-utilizing cement (fast-setting and fast-hardening high-belite sulphoaluminate cement). This cement not only uses a large amount of solid waste (fly ash, blast furnace slag, industrial waste gypsum, alkali slag, etc.) as raw materials, and the waste utilization can reach 40%~95%, but also has a calcination temperature of 150~200℃ and 50 ℃ lower than that of traditional ordinary Portland cement and sulphoaluminate cement, and the carbon emission is equivalent to 30%~60% and 50%~80%. Through the elaboration of its main mineral composition, chemical composition, physical properties and action mechanism, the reasons for its excellent properties such as good whiteness, fast setting and hardening, high late strength, and small dimensional deformation are analyzed. And the application research is focused on the fields of inorganic flooring, airports, road quick repair, prefabricated walls, ultra-light and efficient A-level fire insulation, cement crafts, inorganic artificial stone, and UHPC ultra-high performance concrete. At present, there are many types of low-carbon cement in the world, including Porsol cement, Alinit cement, Celitement cement, Japanese eco-cement, multi-component high-mixture cement, high-belite cement, Anther cement, BCT cement, etc., but most of the products have a slow coagulation and hardening speed, and cannot meet the needs of rapid demolding, turnover, and traffic opening for mortar, concrete, cement products or pavements; at the same time, the production process is complicated and cumbersome, the later strength is low, the deformation is large, and the durability is poor. Therefore, in the actual promotion process in the engineering field, there are great difficulties and many constraints. Among them, Aether cement and BCT cement belong to the belite-sulfoaluminate cement system. Aether cement has 6h early strength performance. Compared with Portland cement (burning temperature1400~1500℃), it can significantly reduce production energy consumption, reduce CO2 emissions by 25%~30% per ton of cement, and the 28-day compressive strength reaches the strength level of standard cement (CEMⅠ52.5R); the size shrinkage of this concrete is less than 50% of that of OPC concrete, but
its raw materials still use limestone, bauxite, gypsum, iron raw materials and marl raw materials, without effective utilization of bulk industrial waste, and CO2 emissions are far from meeting the low-carbon environmental protection requirements. BCT cement can be produced at a lower temperature (1250~1300℃), and its raw materials use industrial waste residues such as limestone, marl, fly ash and industrial by-product gypsum. CO2 emissions are 30% lower than traditional OPC cement clinker, but
there is no early hourly strength, and the strength after 1~2 days is higher than that of ordinary Portland cement. This is far from the goal of using bulk industrial waste as raw materials to produce green, low-carbon, energy-saving and high-performance cement materials, which is currently widely used at home and abroad. At the same time, the above-mentioned low-carbon cement cannot effectively and reasonably control key indicators such as cement whiteness value, early strength before 4 hours, and dimensional change rate, and cannot meet the requirements of high-performance cement. At the same time, the production process is not mature and stable enough, and there is still a long way to go to meet the comprehensive popularization of production industrialization and promotion scale.