INFLUENCE OF RECIPE AND TECHNOLOGICAL FACTORS ON THE PROPERTIES OF ALKALINE ACTIVATION BINDERS

2021 ◽  
pp. 65-70
Author(s):  
М. Ш. Саламанова
Keyword(s):  
Silica Fume ◽  
Ph Value ◽  
Pore Space ◽  
Cement Stone ◽  
Chemical Transformations ◽  
Strength Gain ◽  
Amorphous Substance ◽  
Technological Factors ◽  
Alkaline Conditions ◽  
Kinetics Of

В работе исследовано влияние микрокремнезема на кинетику набора прочности, изменение плотности и порового пространства цементного камня, рецептурно-технологических факторов и условий твердения. Обоснованы химические превращения микрокремнезема в условиях щелочной среды, приводящие к изменениям водородного показателя. Структура цементного камня характеризуется присутствием гидроалюмосиликатов натрия и кальция, кристаллических новообразований, близких к ларниту, и их гидратов, аморфной субстанции, сульфоалюминатов кальция, гидроалюминатов кальция. The paper investigates the effect of microsilica on the kinetics of strength gain, changes in the density and pore space of cement stone, formulation and technological factors and hardening conditions. The chemical transformations of silica fume under alkaline conditions, leading to changes in the pH value, have been substantiated. The structure of the cement stone is characterized by the presence of sodium and calcium hydroaluminosilicates, crystalline neoplasms similar to larnite and their hydrates, amorphous substance, calcium sulfoaluminates, calcium hydroaluminates.

Comparative Labelling and Biokinetic Studies of 99mTc-EDTA(Sn) and 99mTc-DTPA(Sn)

1977 ◽  
Vol 16 (01) ◽  
pp. 30-35 ◽  
Author(s):  
N. Agha ◽  
R. B. R. Persson
Keyword(s):  
Complex Formation ◽  
Significant Influence ◽  
Room Temperature ◽  
Ph Value ◽  
Maximum Activity ◽  
Reduction Step ◽  
Labelling Yield ◽  
Different Temperatures ◽  
Kinetics Of

SummaryGelchromatography column scanning has been used to study the fractions of 99mTc-pertechnetate, 99mTcchelate and reduced hydrolyzed 99mTc in preparations of 99mTc-EDTA(Sn) and 99mTc-DTPA(Sn). The labelling yield of 99mTc-EDTA(Sn) chelate was as high as 90—95% when 100 μmol EDTA · H4 and 0.5 (Amol SnCl2 was incubated with 10 ml 99mTceluate for 30—60 min at room temperature. The study of the influence of the pH-value on the fraction of 99mTc-EDTA shows that pH 2.8—2.9 gave the best labelling yield. In a comparative study of the labelling kinetics of 99mTc-EDTA(Sn) and 99mTc- DTPA(Sn) at different temperatures (7, 22 and 37°C), no significant influence on the reduction step was found. The rate constant for complex formation, however, increased more rapidly with increased temperature for 99mTc-DTPA(Sn). At room temperature only a few minutes was required to achieve a high labelling yield with 99mTc-DTPA(Sn) whereas about 60 min was required for 99mTc-EDTA(Sn). Comparative biokinetic studies in rabbits showed that the maximum activity in kidneys is achieved after 12 min with 99mTc-EDTA(Sn) but already after 6 min with 99mTc-DTPA(Sn). The long-term disappearance of 99mTc-DTPA(Sn) from the kidneys is about five times faster than that for 99mTc-EDTA(Sn).

Special Binding for Refractory Concretes

2019 ◽  
Vol 17 (17) ◽  
pp. 11-16
Author(s):  
Elena Valentina Stoian ◽  
Dan Nicolae Ungureanu ◽  
Florin Toma ◽  
Alexandru Gabriel Colţa ◽  
Daniel Anculescu ◽  
...  
Keyword(s):  
Silica Fume ◽  
Ph Value ◽  
Concrete Structures ◽  
Hydrated Alumina ◽  
Binding System ◽  
Hydraulic Binder ◽  
Aluminous Cement ◽  
Mechanical Strengths ◽  
Condensed Silica Fume ◽  
New System

AbstractThe paper shows data related to coexistence of various binding systems, which could be present during the hardening of special concretes. It is taken into account the Ultra Low Aluminous Cement Concretes additivated with different materials (phosphates and mineral ultra dispersed powders - Condensed Silica Fume, Hydrated Alumina etc). In correlation to the pH-value, these substances can favour the forming of new binding systems besides the hydraulic binder (which is not important in this case). The new system is the coagulation binding form. The coagulation binding system has a very important role in the advanced compactness and in the increasing mechanical strengths of concrete structures.

Influence of High-Calcium Ash Composition on the Composite Binders’ Properties

2021 ◽  
Vol 316 ◽  
pp. 1019-1024
Author(s):  
O. A. Ignatova ◽  
A. A. Dyatchina
Keyword(s):  
Mechanical Properties ◽  
Chemical Composition ◽  
Cement Stone ◽  
Normal Density ◽  
Fine Aggregate ◽  
Equivalent Amount ◽  
High Calcium ◽  
Composition Structure ◽  
Kinetics Of ◽  
Positive Effect

The paper presents the studies’ results of chemical composition, structure, and physico-mechanical properties of high-calcium ashes from the Kansk-Achinsk coals (2017-2019 selection). It was found that ash has a complex poly-mineral composition and contains hydraulically active minerals and oxides of СаОfr, β-C2S, CA, C3A, C4AF, C2F, CaSO4. According to the content of CaOfr, MgO does not meet standards’ requirements. The uniformity of the volume change is maintained by the composition with 50% of cement. The structure and hardening kinetics of ash and ash-cement stone compositions, obtained from the test of normal density, were analyzed. It was established that the hardening of compositions with ash from the Kansk-Achinsk coals was largely influenced by ash minerals. An equivalent amount of cement in composite binders cannot be replaced. In order to obtain a positive effect, compositions with ash instead cement of no more than 30% and a part of fine aggregate, without exceeding the ratio of ash: cement = 1: 1, should be used.

Digital Printing Performance of Cashmere Fabric under Acid or Alkaline Conditions

2011 ◽  
Vol 214 ◽  
pp. 240-244
Author(s):  
Yi Nong Yan ◽  
Xiang Ru Zhang ◽  
Dan Li ◽  
Jian Jian Xu
Keyword(s):  
Ph Value ◽  
Digital Printing ◽  
Dye Uptake ◽  
Printing Quality ◽  
Alkaline Conditions ◽  
Basic Reference ◽  
Minimal Damage ◽  
First Time ◽  
Pretreatment Solution

Pretreatment solution which was obtained by many experiments who had a good printing effect was used to do the digital printing experiment on the cashmere fabric. Printing performance of the cashmere fabric in different pH value was compared to improve the printing quality of the cashmere fabric. Digital printing experiments in the alkaline environment were carried out for the first time and the best pH value was found out which could ensure dye uptake, color fastness, anti-seepage property and minimal damage to cashmere fabric. The paper provided basic reference to the actual production.

Reaction Kinetics for the Hydrolysis of Titanium Isopropoxide Carboxylate Complexes

1992 ◽  
Vol 271 ◽  
Author(s):  
Charles D. Gagliardi ◽  
Dilum Dunuwila ◽  
Beatrice A. Van Vlierberge-Torgerson ◽  
Kris A. Berglund
Keyword(s):  
Carboxylic Acids ◽  
Ceramic Materials ◽  
Titanium Isopropoxide ◽  
General Interest ◽  
Chemical Transformations ◽  
Molecular Precursors ◽  
Novel Applications ◽  
Kinetics Of ◽  
Hydrolysis Of

ABSTRACTTitanium alkoxides modified by carboxylic acids have been widely studied as the molecular precursors to ceramic materials. These alkoxide complexes have also been very useful in the formation of stable, porous, optically clear films having many novel applications such as chemical sensors, catalytic supports, and ion-exchange media. To improve the processing of these materials, it is essential to better understand the kinetics of the chemical transformations which occur.The kinetics of the hydrolysis reaction are studied for selected carboxylic acids using Raman spectroscopy to probe the chemistry of the process. The study has a special emphasis on the titanium isopropoxide-valeric acid system due to the superior quality of these films over other carboxylates. Greater knowledge of the hydrolysis kinetics allows increased control over the quality of the film materials and should be of general interest to those working with modified metal alkoxides.

scholarly journals THE ESTIMATION METHODS OF MICROFILLERS INFLUENCE ON CEMENT STONE PROPERTIES/MIKROUŽPILDŲ ĮTAKOS CEMENTINIO AKMENS SAVYBĖMS ANALITINIO ĮVERTINIMO PRINCIPAI

1997 ◽  
Vol 3 (10) ◽  
pp. 69-75
Author(s):  
Juozas Deltuva ◽  
Žymantas Rudžionis
Keyword(s):  
Relative Density ◽  
Silica Fume ◽  
Cement Paste ◽  
Heterogeneous Material ◽  
Estimation Methods ◽  
Cement Stone ◽  
Structural Element ◽  
Regular Form ◽  
Amorphous Sio2 ◽  
Hardening Process

The concrete and cement microfillers are materials of different fineness, such as wastes of production or pulverized rocks. According to their influence on cement hardening process, they may be classified into inert microfillers or chemically active ones. The chemically active microfillers, such as silica fume, fly ashes and others, have more then 50% amorphous SiO2, that takes part in cement hardening process. Inert microfillers, such as granite, dolomite, sand dust and others, in most cases have no influence on the cement hydration. The usage of microfillers in concrete is common, but so far no clear dependence between the quantity of added microfillers and properties of concrete has been established. One of possible ways to estimate the microfillers influence on the products with cement binder is the structural element method. The structural element is the smallest cell, approximated to a spatial figure of regular form, that has all components with the same proportions, as in all the volume of heterogeneous material. The essence of this method is to divide the mix in to bigger particles, that are named “nuclei” of structural elements and take 50% of all mix volume, and smaller particles, that form cover layers of the nuclei and make up the rest of the volume of the mix. The dependence between the relative density of loose materials and relation (1) between the diameters of the bigger and smaller particles of the structural element has been estimated. This relation is changed when microfillers are added to the cement. There is a possibility to optimize relative density by (2), (3) and (4) relations, if the granulometric composition of the cement and microfillier is known. The experimental and calculated results of this optimization are shown in Table 1. The properties of pressed cement stone with inert microfillers admixture are presented in Table 2. Formulae for calculating the relative density (8) and compressive strength (11) of hardening cement have been estimated. The chemically active microfillers, such as silica fume, interact with Ca(OH)2 and form new CSH. The density and strength of cement stone increased after this interaction. The influence of chemically active microfillers on the relative density of the cement stone is given in (12). The density of cement stone increases to 4.5% and strength increases to 40.2%, if the quantity of inert microfillers in the cement paste reaches 10%. The density of cement stone increases to 7.4% and strength increases to 54.7%, if the quantity of chemically active microfillers in the cement paste reaches 10%.

scholarly journals INFLUENCE OF MECHANOMAGNETIC ACTIVATION OF SOLUTIONS CaCl2 AND Na2S2O3 ON PHASE STRUCTURE OF CEMENT STONE

2019 ◽  
Vol 62 (12) ◽  
pp. 101-107
Author(s):  
Tatyana E. Slizneva ◽  
Marina V. Akulova ◽  
Pavel B. Razgovorov
Keyword(s):  
Solid Phase ◽  
Tap Water ◽  
Pore Space ◽  
Control Sample ◽  
Hydrodynamic Cavitation ◽  
Cement Stone ◽  
Cement Pastes ◽  
Carbonate Ion ◽  
Joint Influence ◽  
Reactive Oxygen Forms

The mechanism of the joint influence of the magnetic field and hydrodynamic cavitation on the properties of CaCl2 and Na2S2O3 solutions used for mixing cement pastes is considered. Hydrodynamic cavitation leads to the formation of reactive oxygen forms, HCO3– anions, carbon dioxide nanobubbles, and initiates the interaction of new forms with impurity metal cations dissolved in water. After mechanomagnetic treatment of the solutions, particles of a solid phase with sizes of 5...10 and 10...100 nm were found in them. The observed increase in the ξ- potential indicates the stabilization of such dispersed systems with the preservation of nanoscale fractions in them (up to 3 days). At the same time, the progress of reactions under the conditions of tightness that occur after cement paste has been mixed. The effect of activating factors in tap water is more pronounced than in distilled water, which is explained by the process of hydration of the carbonate ion and the formation of fine nucleation centers. Using X-ray phase analysis, it was found that, along with calcite, aragonite crystallizes in the resulting cement stone, which is practically absent in the control sample. In addition, the analysis of diffraction patterns taken on the modified samples reveals the inclusion of a carbonate ion. Obviously, optimization of the pore space in the cement stone is achieved both by clogging the pores with fine calcium carbonate, and by forming small pores during crystallization of ettringite-like phases. It is established that the resulting cement stone is characterized by increased strength (by 9-30%) and frost resistance (up to 55%) compared to that obtained by the traditional method.

scholarly journals Desorption and re-adsorption of PAHS on aircraft soot surface

2020 ◽  
Vol 42 (4) ◽  
Author(s):  
Nguyen Mai Lan
Keyword(s):  
High Performance ◽  
Flow Reactor ◽  
Activation Energies ◽  
Binding Energies ◽  
Desorption Kinetics ◽  
Chemical Transformations ◽  
Polycyclic Aromatic ◽  
Kinetics Of Degradation ◽  
Kinetics Of ◽  
Pyrex Tube

Polycyclic Aromatic Hydrocarbons (PAHs) in aircraft soot are capable to distribute in the gas phase and particulate phase in chemical transformations in the atmosphere. The desorption of PAHs from the soot surface is a preliminary step in the study of the reactivity of particulate PAHs. The desorption kinetics of PAHs are measured from soot samples to determine desorption rate constants for different PAHs as a function of temperature and the binding energies between PAHs and soot. The kinetics of degradation of particulate PAHs were studied in the flow reactor. The soot samples previously deposited on a Pyrex tube are introduced into the reactor along its axis and the concentrations of PAHs adsorbed on soot are determined by the High-Performance Liquid Chromatography (HPLC) as a function of the desorption time. The results show a correlation between the size of PAHs and the thermodynamics of desorption: with the PAHs have the same number of carbon atoms, their energies of desorption are very similar and increase with this number. The activation energies EA and the number of carbon atoms in PAHs have a linear correlation. It is consistent with the additivity of the laws Van der Waals. The similarity between the activation energies of desorption of PAHs and the corresponding sublimation enthalpies is consistent with the similarity between the graphitic structure of soot and the structure of PAHs.

scholarly journals Research on Mechanical Performance & Behaviour of Geopolymer Concrete Subjected to Elevated Temperatures

2019 ◽  
Vol 8 (2S8) ◽  
pp. 883-887
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Silica Fume ◽  
Elevated Temperatures ◽  
Mechanical Performance ◽  
Geopolymer Concrete ◽  
Sem Images ◽  
Before And After ◽  
Alkaline Conditions ◽  
Compressive Strength Of Concrete

The investigative studies on mechanical performance & behaviour, of Geopolymer Concrete (GPC) before and after the exposure to elevated temperatures (of 200 0 C -1000 0 C with an increment of 100 0 C). Indicate that the GPC Specimens Exhibited better Compressive strength at higher temperatures than that of those made by regular OPC Concrete with M30 Grade. The chronological changes in the geopolymeric structure upon exposure to these temperatures and their reflections on the thermal behaviour have also been explored. The SEM images indicate GPC produced by fly ash , metakaolin and silica fume, under alkaline conditions form Mineral binders that are not only non-flammable and but are also non-combustible resins and binders. Further the Observations drawn disclose that the mass and compressive strength of concrete gets reduced with increase in temperatures.

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