Categories cement
CEMENT usual CATEGORIES
Portland cement unit (without active additives)
These cements may be used in most structures of concrete, reinforced concrete and prestressed concrete, therefore constituting a critical mass in cement production. Let the class I and compression strength after 28 days in standard mortar, with values of 32.5, 42.5 and 52.5 N / mm2. Also, these cements are characterized by the grinding fineness normal (min. 2500 cm2 / g), good consistency and a normal outlet volume.
Portland cement with additives
These cements can be classified as:
Cement with slag additions.
These cements are produced by the introduction of grinding Portland cement clinker, granulated blast furnace slag and gypsum need to adjust the setting time. The use of blast furnace slags together with other additives possibly lead to savings and reduce clinker portland cement cost prices. Depending on the combination of additives and the amount of slag cement contained in the table, they may receive one of the following properties: a lower initial mechanical strength and resistance portland cements identical end unit; opening and closing a mechanical strength lower compared with the Portland cements with additives (very economical for the lower concrete class); heat of hydration of these cements decreases with increasing proportions of slag (required massive concrete construction); a workability tend to decrease the mortars and concretes, the downside removed by addition of plasticizers or additives to the mixture of the silica ultrafine (SUF).
Ash cement with additives
These cements are obtained by placing the grinding of Portland cement clinker, a power plant fly ash (artificial pozzolan). Like slag, fly ash from power plants, resulting in economy portland clinker and achieving concrete properties (heat-treated) prepared with them: an improved workability of fresh concrete (decrease of mixing water); an increasing homogeneity of fresh concrete; a reduced heat of hydration of cement; a decrease in mechanical strength of the concrete within the first two weeks after the casting; an increase in mechanical strength of concrete after 14 days of casting them; a slight decrease gelivităţii concrete (must be used with air entraining additive); a high resistance to thermal shock and fire; an increased resistance to certain chemical aggressiveness.
Portland cement with high initial strength
These cements are manufactured with a high grinding fineness (min. 3500 cm2 / g). Classes of resistance after 28 days from the cement ranges between 32.5 and 62.5 N / mm2, and their initial resistances are high values 1,2,3 and 7 days compared with the normal cements. They used to work in cold weather concrete, precast concrete industry etc. There extrarapidă hardening Portland cement, obtained by milling to a very fine (min. 7000 cm2 / g) and addition of 1 … 2% calcium chloride. Extrarapidă curing cements are socket 5 … 30 min. in contact with water and used in concrete work in cold climate areas with strong infiltration of water, etc.
Portland cement with limited heat of hydration
These cements have chemical compositions – Mineralogical which improves the low temperatures that most of the heat and moisture to dissipate. Cements of this type have reduced the rate of hydration so that their class is guaranteed 28 days and grade cement concrete made with such specifications is guaranteed by 28 … 90 days after preparation. Portland cement with limited heat of hydration are used in the preparation of concrete placed in the work in heavy elements (weight dams, large blocks of foundations) concrete work put in hot climates, etc.
Blow-resistant Portland cement
These cements are one of the remedies sulphate corrosion. They are characterized by a heat of hydration and a reduced cure rate. In terms of resistance to compression after 28 days they reach minimum values of 32.5 N / mm2.
White or colored cements
For white portland cement is used raw materials with low iron oxide (high quality limestone or chalk and kaolin). These cements have high cost and used for monumental works, decorative works, special finishes etc. For colored Portland cement, use of white cement raw materials, with the addition of fluxing oxides mineralized, dyes, and oxides required.
