This paper used the absolute volume method combined with the experiment to determine the compositions of high performance fine-grained concrete (HPFC) and presented the effect of limestone fine aggregate (LFA) and pozzolan (PU) on the HPFC properties. Test results showed that by increasing the LFA and PU, the workability of the concrete mixture decreased, the maximum slump loss after 90 minutes of mixing was 37.84%, whereas the mechanical properties of HPFC increased. The fine-grained concrete mixture containing 40% PU and LFA completely replaced material for natural sand, the compressive strength of concrete at 28-day increased about 23.87% in comparison to the control mixture. By using the standard NT Build 356, the destruction time of the four specimens tested was of 45, 63, 60 and 61 days, respectively. This result is due to the presence of PU increased the volume of the C-S-H, as well as the density of concrete structure and enhanced the strength of HPFC, thus increased destruction time of specimens used for the assessment of corrosion damage of reinforced in the concrete. The results of the current study support the use of the waste limestone from the quarries as a fine aggregate of green concrete in the future.
One urgent issue today is reducing CO2 emissions worldwide. In particular, the study of using sulfoaluminate cement to create less CO2 is a suitable solution. The paper presents compound additives' influence on the composite binder's standard consistency. Binders such as sulfoaluminate cement, natural gypsum, and tripoli are used as additives. The resulting binder's standard consistency was determined per GOST 310.3-76. Box-Wilson central composite design method was used to simulate the test results. The results obtained are presented as the surface of the second-level regression equation, which describes the dependence of the mixed binder's standard consistency on the additives' content. Research results have been obtained from compositions of composite binders with maximum and minimum standard consistency. Based on the analysis of experimental data, conclusions were drawn about the possible mechanism of the effect of the introduced additives on the consistency of the cement paste.
Introduction. The most popular binders for the concrete production are inorganic binders. Composite binding agents (CB) based on Portland cement are increasingly being used to produce high-quality concretes, improve the efficiency of cement use in concrete, as well as to solve the problem of energy and resource saving by reducing the amount of clinker inthe cement composition. Materials and methods. The properties of a composite binder consisting of Portland cement, alumina cement, natural gypsum and an active mineral additive, were studied. The Box – Wilson experiment design method was used. To determine the standard consistency of the cement paste, the standard test method was chosen according to GOST 310.3–76.The research was carried out in the laboratory of the Department of Building Materials Science of Moscow State University of Civil Engineering. Results. It was found that with the introduction of additives normal density of the cement paste increases. This is explained by the fact that the composition of the complex additive includes tripoli and alumina cement. Tripoli is a natural porous rock with a highly developed surface. Alumina cement has a great influence on the normal density and setting time as it reacts very quickly to form new hydration compounds in the first minute from the start of mixing the binder with water.The dependence of normal density on the quantitative content of additives is presented as a regression equation and surface image. Conclusions. Based on the results of this study, in the future the authors will continue to study the properties of binders based on a complex expanding and pozzolanic addition.
Introduction. The problem of increasing the strength and durability of Portland cement stone is not new, but it is still highly relevant. To improve the properties of the cement binder at the stage of manufacturing cement composites, finely dispersed additives of inorganic origin can be used. They affect processes of hydration and curing of concrete. Finely dispersed additives, being fillers of mineral and inorganic origin, compact the structure of the cement stone, and, consequently, concrete itself due to substantial porosity reduction. They also increase its strength, impermeability and frost resistance and reduce shrinkage. Besides, these additives allow saving clinker and improve the water-retaining capacity of concrete mixes, preventing their segregation, if used together with superplasticizers. Materials and methods. The effect of binder compositions on mechanical properties of a composite binder was studied using the Box-Wilson experimental design method. The compressive strength of cement stone was determined at the age of 7 and 28 days using the method of result processing according to GOST 30744–2001. The study was conducted at the laboratory of Department of Building Materials Engineering of Moscow State University of Civil Engineering. Results. The results are presented as the surface of the second level regression equation, describing the dependence of compressive strength of the cement stone on the composition of multi-component expanding and pozzolanic additives. The optimal composition of the mix, having multi-component additives, was obtained as a result of the experiments. Conclusions. In the future the authors will contribute the results of this study to their research into the properties of binders, containing multi-component expanding and pozzolanic additives.
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