The volume expansion cement during hardening process can be divided into Portland Expansion Cement, Aluminate Expansion Cement, Sulfoaluminate Expansion Cement and Calcium Hydroxide Expansion Cement according to mineral composition. Portland expansive cement, alunite expansive cement, iron oxide expansive cement, magnesia expansive cement, K-type expansive cement belong to Portland expansive cement. This kind of cement is usually grinded in Portland cement with various expansive components.
White Portland cement
is the most important kind of white cement. It is made of limestone, clay and silica with low content of ferric oxide and other non-ferrous metal oxides. It is calcined and quenched at high temperature to form cement clinker, and is filled with gypsum (a small amount of white limestone can be added instead of part of clinker). (or wear-resistant metal) a kind of Portland cement made by grinding lining plates and abrasives in a grinder. In the manufacturing process, in order to avoid the incorporation of non-ferrous impurities, natural gas or heavy oil are mostly used as fuel during calcination. White clinker-free cement can also be prepared from reduced slag, gypsum and white granulated slag produced by furnace steel-making. The color of white cement is expressed by whiteness, which is divided into four grades and determined by whiteness meter. The physical properties of white Portland Cement are similar to those of ordinary Portland Cement. It is mainly used as building decoration materials and also as sculpture products.
Usually it is made of white cement clinker, gypsum and pigments. The pigments used are required to have durability, high dispersion, alkali resistance and no soluble salts under the action of light and atmosphere. They do not destroy the composition and properties of cement. The commonly used inorganic pigments are iron oxide (red, yellow, brown, black cement), manganese dioxide (black, brown), chromium oxide (green), cobalt blue (blue), group blue (blue), carbon black (black); organic pigments include peacock blue (blue) and Tianjin green (green), etc. Portland cement clinker can be used instead of white cement clinker to grind red, brown and black cement. Colored cement can also be added a small amount of metal oxides as colorant in white cement raw materials, directly calcined into color cement clinker, and then grinded to make cement. Coloured cement is mainly used as building decorative materials, and can also be used for plastering and finishing of concrete, masonry, etc.
Radiation Proof Cement
It is a kind of cement with good shielding effect on X-ray, gamma-ray, fast neutron and thermal neutron energy. The main varieties of this kind of cement are barium cement, strontium cement, boron cement, etc. Barium cement is made of barite clay as the main raw material, and clinker composed of barium silicate as the main mineral is obtained by calcination, and then grinded with appropriate amount of gypsum. Its specific gravity is 4.7-5.2, which can be used to make radiation-proof concrete with heavy aggregate (such as barite, steel segment, etc.). The thermal stability of barium cement is poor, so it is only suitable for making radiation protection wall without heat. Strontium cement is a kind of clinker consisting of strontium silicate as the main mineral and grinded by adding appropriate amount of gypsum after calcining and replacing all or part of the limestone in Portland cement raw materials with strontium carbonate. Its performance is similar to that of barium cement, but its radiation protection performance is slightly inferior to that of barium cement. Boron-bearing cement can be obtained by adding appropriate amount of magnesite and gypsum to high-alumina cement clinker and grinding together. This kind of cement can be mixed with boron-containing aggregate and heavy aggregate to make concrete with high proportion, which is suitable for shielding engineering against fast neutron and thermal neutron.
When grinding Portland cement, proper amount of antimicrobial agents (such as pentachlorophenol, DDT, etc.) are added. It can be used to prepare anti-bacterial concrete for use in places where bacteria need to be prevented, such as swimming pools, public baths or food industry structures.
Algae Control Cement
Sulfur (or sulfur-containing substances) and a small amount of hardening agent (such as lime) are added into high alumina cement clinker and ground together. It is mainly used on the surface of wet shade structure to prevent algae from attaching and reduce the damage of algae to structures.