A Look Into Portland Cement Types & Production Features

The post on portland cement manufacturing features is prepared in cooperation with Telling, the architectural company widely using hydraulic lime, lime mortar and concrete materials in its projects.

Plasticized portland is the product of pulverizing portland cement clinker with gypsum dihydrate (3-5%) and with addition of about 0.25% of yeast mash sulfide or other plasticizing additives at a grinding stage. These additives are adsorbed on the surface of the cement particles, improve wetting of cement with water and preventing their interaction. The additives reduce the friction between the grains of cement in concrete mixtures – and between grains of filler, thereby increasing their mobility, which can reduce the consumption of cement in the concrete by 5-10%.

Hydrophobic Portland cement is the product of pulverizing portland cement clinker with gypsum dihydrate (3-5%) and with the addition of 0.1-0.2% of hydrophobic additives – oil soap, synthetic fatty acids, etc., during grinding. Synthetic fatty acids, their salts and other particles are adsorbed on the surface of the grains of cement, to form thinnest water repellent films, reducing wettability. As a result, the hydrophobic cements can stay a long time in air with high humidity without losing its qualities.

While stirring concrete the integrity of hydrophobic film is disrupted, after which the cement reacts with water easily. The remaining additives in the concrete improve its quality, such as increasing the frost resistance, resistance to aggressive environments, etc.

Plasticized and hydrophobic Portland cement is used on a par with ordinary Portland cement for concrete and reinforced concrete ground, underground and underwater structures, including working under cyclic freezing or moisture.

White and colored Portland cement

The raw material for the production of white Portland cement are pure limestone and white clay. The raw mass is burned in an ash-free (gaseous) fuels, to improve the whiteness the clinker is fired in a reducing environment and is bleached by water quench. White cement should contain no more than 0.35-0.5% of iron oxide. During grinding the cement should be carefully protected from falling into the iron particles or iron oxides which impair its whiteness. According to the degree of whiteness of white Portland cement divided into three classes: 1st grade cement has a reflectivity of at least 80%; 2nd grade – no less than 75% and 3rd grade – no less than 68%. The brightness is determined photometrically; as for the reference barium sulfate BaS04 is considered as it has a reflectance of not less than 95%. It should be noted that the reflectance of conventional Portland cement is 40%.

Colored cements are produced by mixing white Portland cement clinker with alkali resisting and light-resistant pigments. Pigments are added is not more than 15% of the mineral and not more than 0.3%) of organic. To create colored cements – yellow, pink, red, brown, green, blue and black colors, natural pigments (ocher, iron oxide, and others.) and artificial (chromium oxide, mummy, manganese oxide – pyrolusite) are used.