scholarly journals Heat-Resistant Foam Concrete on the Basis of Two-Component Binder

2019 ◽  
Vol 18 (2) ◽  
pp. 121-126
Author(s):  
S. N. Leonovich ◽  
D. V. Sviridov ◽  
A. L. Belanovich ◽  
V. P. Savenko ◽  
S. A. Karpushenkov
Keyword(s):  
Essential Role ◽  
Solid Phase ◽  
Basalt Fiber ◽  
Foam Concrete ◽  
Initial Strength ◽  
Heat Resistant ◽  
Two Component ◽  
Aluminous Cement ◽  
Mineral Additives ◽  
Cementing Agent

The composition of dry mix on the basis of two-component cementing agent (aluminous cement and clay of the “Kustikha” field), mineral additives (a metakaolin, the RSAM sulfoaluminate modifier, waste of basalt fiber), Ufapore foamer and the accelerating and plasticizing “Citrate-T” additive is developed. When mixing “Citrate-T” additive with water at Water/Solid = 0.45–0.70, the subsequent mechanical binder and hardening of a foam mass heat-resistant foam concretes with a density of 300–650 kg/m3 are formed (depending on Water/Solid value). Foam concretes have strength on compression of 0.2–2.5 MPa before warming up when their initial strength depends on processes of hydration curing of aluminous cement that provides fixation of their porous structure. After annealing at 1000 °C foam concretes have final strength of 0.3–3.2 MPa due to processes of solid-phase agglomeration of clay with other components of dry mix at their heating. Foam concretes after annealing unlike foam concretes on the basis of a Portland cement and aluminous cement have big strength. Introduction of the accelerating and plasticizing “Citrate-T” additive into composition of the dry mix leads to an increase of rheological properties in expanded foam mass and time reduction of its drying and curing. It has been established that an essential role is played by the relation Water/Solid: at increase in the relation Water/Solid (with 0.45 to 0.70) occurs increase in volume of foam mass after a mechanical binder, and also heterogeneity of pores and their sizes increases that leads to reduction of density of foam concretes and strength on compression.

Impact of Superplasticizing Agents on Physical and Mechanical Properties of Cellular Concrete

2019 ◽  
Vol 974 ◽  
pp. 181-186
Author(s):  
V.A. Perfilov ◽  
V.V. Gabova ◽  
Inessa A. Tomareva
Keyword(s):  
Mechanical Properties ◽  
Pore Structure ◽  
Pore Space ◽  
Experimental Studies ◽  
Basalt Fiber ◽  
Physical And Mechanical Properties ◽  
Foam Concrete ◽  
Cellular Concrete

The effect of superplasticizing, foam agents, various fiber aggregates on the physical and mechanical properties of cellular concrete has been studied. The article covers the results of experimental studies conducted to determine the effect of foam agents PO-6 and PB-2000, as well as polymeric and basalt fiber on the pore structure of foam concrete. The dependence between the change in density and strength of cellular concrete and the structure of its pore space has been determined.

Preparation of copper compounds of different compositions and particle morphologies

1991 ◽  
Vol 6 (4) ◽  
pp. 766-777 ◽  
Author(s):  
Stanka Kratohvil ◽  
Egon Matijević
Keyword(s):  
Essential Role ◽  
Solid Phase ◽  
Particle Morphology ◽  
Chemical Compositions ◽  
Rapid Phase ◽  
Copper Compounds ◽  
Sulfate Solutions ◽  
Amorphous Particles ◽  
Particle Shapes ◽  
Nitrate Solutions

Copper compounds of different chemical compositions and particle shapes were prepared by homogeneous precipitation from copper salt solutions in the presence of urea. It was demonstrated that the nature of the anions played an essential role in the properties of the generated solid phase. Thus, Cu(II)-nitrate solutions yielded spherical amorphous particles which had the composition of malachite [Cu2(OH)2CO3], the Cu(II)-chloride solutions gave bipyramidal particles of atacamite [CuCl2 · 3Cu(OH)2], and in Cu(II)-sulfate solutions needle-shaped brochantite [3Cu(OH)2 · CuSO4] or platelets of posnjakite [3Cu(OH)2 · CuSO4 · H2O] were formed. The addition of NaOH to prepared dispersions resulted in a rapid phase transformation of all above solids into needle-like Cu(OH)2. Calcination of various copper basic compounds at 700–800 °C temperature produced CuO, while the particle morphology was retained.

scholarly journals Research of the mineral additives influence on aggregative stability of foam concrete mixture

2021 ◽  
Vol 2131 (4) ◽  
pp. 042034
Author(s):  
E Bartenjeva
Keyword(s):  
Aggregate Stability ◽  
Stable Structure ◽  
Concrete Mixture ◽  
Aggregative Stability ◽  
Cement Stone ◽  
Foam Concrete ◽  
Effect Of Additives ◽  
Modifying Effect ◽  
The Stability ◽  
Mineral Additives

Abstract An effective method for increasing the aggregate stability of non-autoclave heat-insulating foam concrete is proposed. This material is prepared using a two-stage technology on a turbulent-type installation. An increase in the stability of the foam in the mortar mixture by 9.5-23% has been established. An increase in the viscosity of the foam concrete mixture by 13.5% was revealed. Wollastonite and diopside are actively involved in the formation of a stable structure of foam concrete and are structurally modifying centers. The introduction of mineral additives contributes to the formation of a homogeneous stable structure of non-autoclave foam concrete. Thus, an increase in the stability of the cellular system in the technology of non-autoclave cement-ash foam concrete is possible due to the control of the processes of structure formation when using dispersed mineral additives of wollastonite and diopside. Due to the structural-modifying effect of additives as crystallization centers for neoplasms, a more complete hydration of the cement and a strong contact of the additives with the cement stone should be ensured

scholarly journals Rheological characteristics of the binder for foam concrete with a complex of mineral modifiers

2021 ◽  
Vol 12 (2-2021) ◽  
pp. 180-184
Author(s):  
D. D. Netsvet ◽  
◽  
V. V. Nelubova ◽  
Keyword(s):  
Portland Cement ◽  
Cement Mortar ◽  
Point Of View ◽  
Rheological Characteristics ◽  
Foam Concrete ◽  
Combined Use ◽  
Cement System ◽  
Mineral Additives ◽  
Mixing Water ◽  
Modifying Additive

The paper considers the effect of mineral additives on the rheological characteristics of a binder for foam concrete. The compositions in the study were divided into two groups: based on nanostructured binder (NB) and based on cement. For the compositions of the first group portland cement is proposed as a modifying additive,for the compositions of the second group NB and anhydrite were used as modifying additives. It has been shown that the introduction of cement into NB increases the viscosity due to an increase in the concentration of large-sized particles, while the combined use of nanostructured binder and anhydrite as modifiers of the cement system helps to reduce the viscosity of the cement mortar and increase its mobility, which reduces the amount of mixing water. From a technological point of view, this will make it possible to obtain materials with a rational pore structure by optimizing porosity processes.

scholarly journals Application of equilibrium phase diagrams for calculation of segregation kinetics during two-component melt cooling

2020 ◽  
Vol 63 (2) ◽  
pp. 129-134
Author(s):  
A. D. Drozin ◽  
E. Yu. Kurkina
Keyword(s):  
Liquid Phase ◽  
Equilibrium State ◽  
Cross Section ◽  
Diffusion Coefficients ◽  
Solid Phase ◽  
Equilibrium Phase ◽  
Minimum Size ◽  
Two Component ◽  
Solid Phases ◽  
Liquid And Solid Phases

According to the equilibrium state diagrams, when the melt is cooled to a certain temperature below liquidus, compositions of liquid and solid phases are uniquely determined by corresponding curves in the diagram. However, it does not happen in reality. For equilibrium (which the diagram describes), it is necessary that the melt is maintained indefinitely at each temperature, or thermal conductivity of liquid and solid phases, and the diffusion coefficients of their components, are infinitely large. We made an attempt to find out how these processes occur in reality. In this work, we consider the growth of individual crystal during cooling of a two-component melt. Mathematical model is constructed based on the following. 1. The melt area with volume corresponding to one grain, the periphery of which is cooled according to a certain law, is considered. 2. At the initial instant of time, a crystal nucleus of a certain minimum size is in the liquid. 3. At the surface of crystal, compositions of liquid and solid phases correspond to equilibrium state diagram at a given temperature on its surface. 4. Changes in temperature and composition in liquid and solid phases occur according to the laws of heat conduction and diffusion, respectively. As the melt gets cold and the crystal grows, the liquid phase is enriched in one component and depleted in another, the solid phase – on the contrary. Since the diffusion coefficients of the components in the solid phase are small, the composition of the crystal does not have time to completely equalize its cross section. The model proposed in the work allows us to study this phenomenon, to calculate for each cooling mode how the composition of the crystal will vary over its cross section. The calculations have shown that the temperature equalization occurs almost instantly, and composition of the liquid phase equalizes much slower. Equalization of the solid phase composition does not occur in the foreseeable time. The results of the work will help to improve technology of generation of alloys with an optimal structure.

scholarly journals POLYMINERAL COMPOSITE BINDERS FOR FOAM CONCRETE: FEATURES OF HYDRATION AND HARDENING

2020 ◽  
Vol 17 (1) ◽  
pp. 122-135
Author(s):  
V. V. Voronov ◽  
E. S. Glagolev
Keyword(s):  
Electron Microscopy ◽  
Portland Cement ◽  
Building Materials ◽  
Heat Dissipation ◽  
Experimental Studies ◽  
Foam Concrete ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Mineral Additives ◽  
Scanning Electron

Introduction. The paper devotes to the features of hydration and hardening of polymineral composite binders. The authors carry out the complex research of the phase composition, hydration and structure formation processes of hardened composite binders with active mineral additives by X-ray phase analysis, differential scanning calorimetry and electron microscopy. The study using a Tescan MIRA 3 scanning electron microscope reveals differences in the microstructure of hardened binders and the authors confirm the results by microprobe studies. The authors study the hydration of the composite binder prepared on the basis of Portland cement and mineral components. Moreover, the paper demonstrates the dynamics of the system’s heat dissipation from the moment of mixing with water and hardening up to 24 hours and up to 72 hours by the expressed bond of dQ / dt = f (t) using a differential calorimeter.Methods and materials. The authors carried out experimental studies at Belgorod State Technological University named after V.G. Shukhov, at the Department of Building Materials, Products and Structures, at the High Technology Center and “BelGTASM-Certificate” Test Center. Therefore, the authors used the existing basic research methods, including modern physicochemical methods of analysis: X-ray phase, scanning electron microscopy, etc. The paper determined the main characteristics of raw materials, composite binders and foam concrete using standard methods and regulatory requirements.Results. The authors obtained the results that testified the peculiarities of hydration and hardening processes of polymineral composite binders on the basis of Portland cement and mineral additives: opoka marl and fly ash.Conclusion. The research establishes the hydration and hardening processes of polymineral composite binders. As a result, the authors demonstrate that the opoka marl introduced into the cement leads to the increased hydration in the induction and accelerated periods and also increases the hydration completeness of the main clinker minerals due to the manifestation of the pozzolanic reaction and the active binding of blocking Portlandite, as well as to the higher concentration of accumulated neoplasms, second generation calcium hydrosilicates.Financial transparency: the authors have no financial interest in the presented materials or methods. There is no conflict of interest.

THE ROLE OF THE PITUITARY IN THE RESISTANCE OF THE GOLDFISH (CARASSIUS AURATUS L.) TO A HIGH TEMPERATURE

1967 ◽  
Vol 45 (3) ◽  
pp. 329-345 ◽  
Author(s):  
Peter H. Johansen
Keyword(s):  
High Temperature ◽  
Heat Resistance ◽  
Carassius Auratus ◽  
Essential Role ◽  
High Temperature Stress ◽  
Heat Resistant ◽  
Goldfish Carassius Auratus ◽  
Normal Fish ◽  
Resistance Tests

The heat resistance of normal, hypophysectomized and pituitary-autotransplanted goldfish acclimated to 20 °C under 16-h photoperiod and 8-h photoperiod conditions was determined. It was found that hypophysectomized goldfish were less heat resistant than normal fish and that those with an autotransplanted pituitary were as heat resistant as normal fish.The photoperiod results, though inconclusive, suggest that normal 16-h photoperiod fish are more heat resistant than normal 8-h photoperiod fish and that only the fish with a normal pituitary can respond to photoperiod changes. The fish without a pituitary are slightly less heat resistant than normal 8-h-photoperiod fish, while those possessing an autotransplanted pituitary are as resistant to a high temperature as normal 16-h-photo period fish.Treatment of hypophysectomized goldfish with luteinizing, thyrotropic, adrenocorticotropic, and lactotropic (prolactin) hormones and crude salmon pituitary extract appeared not to affect resistance to a high temperature.In the experiments involving pituitary autotransplantation, a study was made of various organs influenced by pituitary secretions to determine the pattern of hormone output by the pituitary. By contrasting this information with that of the heat resistance tests, various hormones have been suggested as not playing an essential role in high temperature resistance. The hypothesis is put forward that a prolactin-like hormone plays the essential role in resisting a high-temperature stress.

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