Papers by Keyword: Freeze-Thaw Resistance

Abstract: This paper deals with the experimental determination of the freezing and thawing resistance of concrete using an innovative approach to evaluating the signal obtained by the ultrasonic pulse velocity test. Test specimens made of two types of concrete were used for the experiment. They were concrete mixtures of similar composition - the same components were used for their production. The only major difference was their level of resistance to freezing and thawing. The test specimens were prisms produced in the laboratory using plastic moulds and cylinders obtained by core drilling from the experimental pillar. The core-drilled test specimens were exposed to 100 freeze-thaw cycles and the test prisms with as many as 200 freeze-thaw cycles. After every 25th cycle, the non-destructive parameters were determined using the ultrasonic pulse velocity test as well as the resonance method. It was found that more advanced parameters of the ultrasonic signal than just its velocity were useful for evaluating the freezing and thawing resistance of concrete.

Abstract: The main objective of this study was to investigate the influence of using magnetized water on the mechanical properties and durability behavior in terms of freeze-thaw resistance of recycled aggregate concrete. In addition to the effect of different numbers of water rounds in the magnetic field, other variables including steel fibers, super-plasticizers and silica-fume were considered in the concrete production in order to achieve the ideal possible performance for recycled aggregate concrete made with 100% coarse aggregates replacements. For this purpose, a total of 11 concrete mixes were prepared and tested. At the first step, the effects of the mentioned variables on the basic properties, including workability, water absorption, compressive strength, splitting tensile strength, flexural strength and freeze-thaw durability test were investigated. Additionally, flexural toughness was evaluated in accordance with the post-crack strength (PCS) method and the microstructure of concrete specimens was also observed by using scanning electron microscope (SEM). The results of most experiments indicated that magnetized water, although highly effective on the mechanical properties of concrete, should not be solely utilized as a compensating factor for the defects caused by recycled coarse aggregates. The optimum toughness and durability results regarding the fiber-reinforced concrete mixes produced with recycled coarse aggregates, were related to samples containing silica-fume and 10-rounds magnetized water. Furthermore, the existence of cement replaced by 10% of silica-fume and 10-rounds magnetized water in the concrete mix MW-SF2, increased the durability of the recycled aggregate concrete by an average of approximately 63%.

Abstract: The article is devoted to determining the patterns of improving the performance of concrete using hydro-remote ash-slag mix and polypropylene fiber. For this, a four-step methodology was developed for producing purified aluminosilicates from ash-slag mix. A set of experimental studies included the study of both raw materials and developed composites. The compressive strength, flexural strength, and freeze-thaw resistance were chosen as the target characteristics. The mechanism of the effect of purified aluminosilicates on the compaction of the composite structure was determined. At the same time, polypropylene fiber effectively inhibits the formation of cracks and they growth. The optimal composition is the replacement of cement with an ash-slag mix in an amount of 50% and in the presence of fiber. In this case, the compressive strength was increased by 19%, and the flexural strength by 122% compared with the reference composition. Thus, it was proved that both hydro-remote ash-slag mix and polypropylene fiber, and especially from combined use, make it possible to create effective fiber-reinforced concrete with excellent mechanical and durability characteristics.

Abstract: The paper discusses means of testing the freeze-thaw resistance of concrete, which is part of an existing structure. Practically all standards and regulations dealing with freeze-thaw resistance describe tests that require cast prism-shaped specimens. This can make determining the freeze-thaw resistance of a concrete part of a structure rather difficult. The paper discusses the problem in detail, proposes solutions, and presents a real-world example of determining the freeze-thaw resistance of bridge abutments.

Abstract: The authors obtained fine grain concrete based on the mortars of additives-electrolytes undergone mechanic magnetic activation and characterized by improved compression and bending strength and enhanced freeze-thaw resistance. There was investigated the impact of mechanic magnetic activation (MMA) on mixing water when adding calcium chloride and sodium thiosulphate as well as on porosity of cement stone and specific features of phase formation in cement stone. It was stated by the authors that MMA facilitates formation of nucleation centers in activated water in the presence of additives-electrolytes, optimization of porous space as well as crystallization of calcium carbonate in the form of aragonite when lowering the content of Portlandite. The mechanism of joined influence of hydrodynamic and magnetic treatment of mixing water has been determined.

Abstract: This paper presents research results of recycled fine aggregate concrete testing. The main aim of this contribution is verification of properties of fine aggregate concrete with partial replacement of fine natural aggregate by recycled masonry aggregate originated from construction and demolition waste. The influence of partial replacement of natural sand to mechanical properties and freeze-thaw resistance is described. The compressive strength and flexural strength were tested at the age of 28 and 60 days and after 25, 50, 75 and 100 freeze-thaw cycles. Partial replacement of natural sand was 0, 25 and 50 % for all these tests. Prismatic specimens were examined.

Abstract: Durability is one of the main characteristics in the production of high-quality concrete paving blocks in the Baltic region climate zone. Concrete paving blocks are produced by means of vibropressing, dimensions: 198×98×80 mm. The article describes tests with concrete paving blocks, the top layer of which contains 5% of zeolite admixture obtained from waste of aluminum fluoride production by low-temperature synthesis. The durability of concrete paving blocks was tested according to abrasion resistance, tensile splitting strength, absorption and frost resistance. The test results revealed that 5% of zeolite admixture added to the top layer of concrete paving blocks reduce the absorption, increase the tensile splitting strength and decrease abrasion. The zeolite admixture used in concrete paving blocks reduces the scaling about 4 times after 28 freeze-thaw cycles when 3% NaCl is used as the freezing solution. The test results proved that synthetic zeolite obtained from aluminum fluoride by means of low temperature synthesis can be used as a supplementary cementitious material to increase the durability of concrete pavement elements.

Abstract: It’s really necessary to determine freeze-thaw resistance of concrete faster and correctly.The offered method is based on measurement of long strength by nondestructive method, based onacoustic issue. Also dilatometer is used. During this research, the theoretical analysis of concrete'sspecimen dependence on freeze-thaw resistance and energy, which is emitted by a specimen duringdestruction, has been carried out. Freeze-thaw resistance of a specimen is calculated as themathematical relation of these energies. Correctness of the offered method is proved byexperiments. The offered method is characterized by small labor input, high efficiency and a wideapplication scope, but special laboratory equipment is needed.

Abstract: The industry of construction is responsible for the high consumption of raw materials, energy and waste production. As such, it becomes imperative to develop and study new constructive solutions with greater sustainable value. The mortars with incorporation of phase change materials (PCM) have the ability to regulate the temperature inside buildings, contributing to the thermal comfort and reducing the use of heating and cooling equipment, using only the energy supplied by the sun. However, the incorporation of phase change materials in mortars modifies its characteristics. The main focus of this study was the durability of mortars with PCM incorporation based in different binders. The binders studied were aerial lime, hydraulic lime, gypsum and cement. For each type of binder, different mortars were developed with different content of PCM. The proportion of PCM studied was 0% and 40% of the mass of the sand. It was possible to observe that the incorporation of PCM in mortars caused differences in properties such as water absorption by capillarity, water absorption by immersion and degradation after freeze-thaw cycles.

Abstract: Main purpose of research is establishing correlation of decreasing strength limit at the time of concretes thermo cycling. Research is based on invented in 2008 Method for definition of concretes frost resistance. This method is concerning to estimation of concrete's deformation after saturating of concrete sample by water, its freezing to standard temperature and defrosting. It has small labor input and high operability. During research, the theoretical analysis of results of experiment by the offered Method was carried out. Correlation between decreasing strength limit and unit strain of concrete samples was establish.