Browsing by Subject "cement ekspansywny"

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Access status: Open Access ,
Cementy specjalne dla budownictwa podziemnego
(Wydawnictwa AGH, 2009) Szeląg, Henryk; Kurdowski, Wiesław
The paper describes properties of special cements and prepared concrete blends elaborated and produced in the Division of Mineral Building Materials in Cracow. Showed properties emphasize exceptional features of these materials which guarantee durability of constructions under extreme conditions of exploitation load and environmental effects. It concerns very high resistances, small porosity and advantageous pore size distribution, resistance to chemical corrosion, freeze resistance and controlled values of very low contraction and expansion for expansive concretes. These properties predispose above mentioned materials to accomplishment and repair of concrete constructions in road infrastructure building, especially in applications of underground construction as well as in constructions of mining industry.
Access status: Open Access ,
Czynniki determinujące naprężenia powstające w cemencie ekspansywnym
(Data obrony: 2008-09-26) Szeląg, Henryk
Wydział Inżynierii Materiałowej i Ceramiki
The purpose of this paper was to study an influence of expansive cement composition on tensions taking place in mortars prepared of this kind of cement. Two expansive additives have been tested: monocalcium aluminate (CA) and calcium sulfatealuminate ($C_{4}A_{3}S$), the later known in cement technology as Klein complex. Sulfates have been introduced as gypsum only. A small addition of calcium oxide of maximum $5\%$ has also been used. On the basis of obtained results were possible to settle as follows: Increase of an expansive additive (Klein complex or monocalcium aluminate makes expansion higher. An increase of a specific surface of Klein complex or monocalcium aluminate gives the similar effect (higher expansion). A significant influence for expansion has the gypsum/Klein complex ratio or gypsum/ monocalcium aluminate ratio and by modifying this ratio is possible to modify expansion cements properties. Greater value of this ratio makes expansion higher increasing simultaneously tensions of mortar what at an extreme limit leads to the destruction of mortar prisms. Expansion cements having G/($C_{4}A_{3}S$), or G/CA ratio equal to the stechiometry of etringitt formation are suitable binders for the preparation mortars and concrete curried in the air of common humidity ($60\%$ of RH). They should be used for repair works of concrete at this kind of environmental conditions. Classic behaviour of expansive cements ensures lower G/expansive additive ratio which should approximately be equal to monocalcium aluminate phase. Calcium oxide addition plays an important role in case of cement with Klein complex, improving its properties, increasing expansion and tensions. Influence of calcium oxide on cement with monocalcium aluminate is nearly the same as in case of use of the Klein complex but the differences of obtained tensions are smaller. Expansive additive as monocalcium aluminate ensures greater tensions of samples then Klein complex additive. Fineness of Portland cement serving as matrix has great influence on tensions of expansive cements with addition of Klein complex. Influence of Portland cement fineness as a matrix in case of cements containing monocalcium aluminate is much lower.