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Content available remote Mechanical and durability properties of concretes incorporating natural zeolite
EN
This paper investigates the application of natural zeolite as a substitute of cement in concrete. It studies the mechanical and durability properties of concretes containing 10% of natural zeolite and superplasticizer, as well as 10% of natural zeolite, superplasticizer and an air-entraining agent in comparison to concretes without natural zeolite. The study shows that fresh concrete mixture containing zeolite due to its high surface area demands a higher dosage of superplasticizer to achieve the targeted slump flow. While concretes containing natural zeolite characterize a lower compressive strength until 90 days of hardening, the compressive strength exceeds the strength of the concretes without zeolite after 180 days. The results also reveal the considerable effectiveness of using a superplasticizer and an air-entraining agent in zeolite incorporating concretes on water penetration, drying shrinkage and freeze–thaw resistance of concretes.
EN
Complex geological structure as well as long-term intensive operation of oil and gas deposits in Borislav-Pokutska zone of Carpathians leads to changes in thermo-dynamical parameters of pools, rock deformation and, as a result, to crippling of the boreholes and creasing and damaging of boring casing. The abovementioned actions not only complicate extraction of oil and gas but increase the technological charge on the environment. In this study 3 types of materials were investigated: PCT-I-100 – traditional tamping cement, CREA and CREA-LF tamping mixes produced by dry mixing technology that were designed by authors. Dry mixes are characterized by higher level of SiO2 because of addition of milled sand and provide better cementation quality. Developed materials are characterized by lower dehydration and water reduction, thanks to clearly chosen composition and modern chemical admixtures usage. The method of borehole eliminative cementation is also presented by authors.
EN
In this study, properties and peculiarities of hydration processes as well as paste microstructure of blended cements containing 10% by weight of natural zeolite were investigated. Free calcium hydroxide content, crystalline hydration products and microstructural architecture of hydrated cement pastes were examined by physical and chemical methods. It was found that the addition of natural zeolite provides formation of an extra amount of fine crystalline ettringite and tobermorite-like calcium hydrosilicates of CSH (B) type in the mineral non-clinker part of Portland cement resulting in strength synthesis of cement stone with high performance properties.
EN
In the article there were presented the results of modern composite materials for cementing the boring casing during the construction of boreholes at oil-and-gas deposits of Pry-Carpathians region. Implemented investigations evidenced the effectiveness of use of composite oil-well and oil-and-gas materials and deposit.
5
Content available remote Dry building mixtures on the basis of gypsum-free portland cement
EN
Theoretical principles for obtaining gypsum-free Portland cement (GFPC) modified by organic-mineral additives were investigated. Gypsum-free Portland cement was improved by rational selection of the chemical additives which act as hardening accelerators, plasticizers and setting retarders. The hydration and structure formation processes as well as building-technical properties and running ability were established. The influence of alkaline metals carbonates as hardening accelerators on pH of a liquid phase, hydration degree in the alkaline systems as well as features of plasticizers action in constitution complex chemical additives were investigated. The possibility of speed regulation of GFPC early structure formation by introduction setting retarders which are replacing the effects of gypsum was determined. There were investigated the characteristics of the phase structure and microstructure of the artificial cement stone on the basis of gypsum-free Portland cement modified by the complex chemical additives and fine-dyspersated lime stone. Early structure formation is characterized by hydroaluminate hardening type with formation of metastable carbonate replaced by AF-phase followed by structurally active hexagonal AFm-phase C4A.C02-11H20.
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