The Increase of Hydration Activity of Portland Cement by Additives of Crystalline Hydrates

2019 ◽  
Vol 974 ◽  
pp. 195-200
Author(s):  
Yury R. Krivoborodov ◽  
Svetlana V. Samchenko
Keyword(s):  
Phase Composition ◽  
Portland Cement ◽  
Cement Hydration ◽  
Bound Water ◽  
Cement Stone ◽  
Pulsation Apparatus ◽  
Rotary Pulsation Apparatus ◽  
Calcium Hydrosilicates ◽  
Crystalline Hydrates

The article presents the results of a study of the effect of synthesized microdisperse additives of crystalline hydrates based on calcium sulfoaluminates on the properties of cement stone. The effectiveness of the use of a rotary pulsation apparatus (RPA) to obtain microdispersed additives is identified. The possibility of accelerating the hardening of cement stone by entering microdispersed additives into its composition is shown. It has been established that in the presence of microdispersed additives of crystalline hydrates in the cement stone, the phase composition of hydrate tumors changes, the amount of calcium hydrosilicates and ettringite increases, the porosity decreases and the strength of the cement stone increases. This provision is confirmed by the increase in the degree of cement hydration, the amount of bound water in all periods of hardening of the stone. It is proposed to use microdisperse additives, which play the role of primers for the crystallization of ettringite and calcium hydrosilicates, to increase the strength of cement stone in the early stages of hardening.

scholarly journals CHANGES IN THE STRUCTURAL AND PHASE COMPOSITION OF CEMENT CONCRETE DURING MICROBIOLOGICAL CORROSION

2021 ◽  
Vol 6 (11) ◽  
pp. 106-113
Author(s):  
K. Strokin ◽  
D. Novikov ◽  
V. Konovalova ◽  
N. Kasiyanenko
Keyword(s):  
Compressive Strength ◽  
Phase Composition ◽  
Portland Cement ◽  
Cement Stone ◽  
Cement Concrete ◽  
Microbiological Corrosion ◽  
Crystalline Phases ◽  
X Ray ◽  
Calcium Hydrosilicates ◽  
Black Mold

The article considers the change in the structural and phase composition of cement stone made of Portland cement of the CEM I 42.5 N brand in the process of bacterial and fungal corrosion during 6 months when humidified. The X-ray images of cement stone show peaks that characterize the non-hydrated components of Portland cement alite, belite, tricalcium aluminate, four-calcium aluminoferrite and gypsum. By the method of X-ray phase analysis, it is found that during microbiological corrosion, the content of all phases of cement stone decreases. The aspergillus niger van Tieghem fungi have a stronger effect on the structural and phase composition of cement stone. Fungal microorganisms destroy the crystalline phases and absorb amorphous phases – calcium hydrosilicates C-S-H (I) and C-S-H (II) and tobermorite. When bacteria Bacillus subtilis affects the cement stone, the content of the calcite phase increases, which is a product of corrosion, while the action of black mold reduces the intensity of CaCO3 peaks. A decrease in the content of low-base calcium hydrosilicates and ettringite, as well as other crystalline phases, leads to a decrease in the compressive strength of the cement stone. During 6 months of microbiological corrosion of cement concrete under conditions of constant wetting, the compressive strength decreases by about 35 %.

Influence of Nanoscale Barium Hydrosilicates on Composition of Cement Stone

2016 ◽  
Vol 683 ◽  
pp. 90-94 ◽  
Author(s):  
Anna Nikolaevna Grishina ◽  
Evgeniy Valerjevich Korolev
Keyword(s):  
Composite Materials ◽  
Chemical Composition ◽  
Portland Cement ◽  
Cement Hydration ◽  
Experimental Investigations ◽  
Cement Stone ◽  
Hydration Products ◽  
Efficient Control ◽  
Calcium Hydrosilicates ◽  
Portland Cement Hydration

The development of new types of composite materials is an important aim for construction. Nanoscale admixtures allow efficient control of the composition and properties. Results of experimental investigations concerning effect of admixture of nanoscale barium hydrosilicates to the chemical composition of hydrated portland cement are discussed in the present work. It is shown that several key processes are taking place during nanomodification. Amount of portlandite in cement stone decreases, and there is also quantity growth of different calcium hydrosilicates CSH (I), CSH (II), riversideite and xonotlite. Influence of composition and storing time of barium hydrosilicates to the ratio of different portland cement hydration products is examined. It is found that admixture of barium hydrosilicates with gross formula BaO•26.47SiO2•nH2O stored for 28 days leads to both reduction of portlandite and accretion of hydrated phase.

Properties of Composite Gypsum Binders Depending on Multicomponent Mineral Additives

2019 ◽  
Vol 945 ◽  
pp. 238-243 ◽  
Author(s):  
Valery S. Lesovik ◽  
N.V. Chernysheva ◽  
M.Yu. Drebezgova
Keyword(s):  
Portland Cement ◽  
Magnetic Separation ◽  
Water Resistance ◽  
Cement Hydration ◽  
Raw Materials ◽  
Crystal Formation ◽  
Calcium Hydrosilicates ◽  
Nanodispersed Silica ◽  
Mineral Additives ◽  
Ferruginous Quartzites

This article considers the possibility of increasing the effectiveness of composite gypsum binders (CGB) by controlling the processes of structure formation as a result of using new types of multicomponent mineral additives that are significantly different from the traditionally used quartz raw materials:- waste of wet magnetic separation of ferrous quartzites (WMS waste,) of polymineral composition with quartzy of varying degrees of crystallinity, nanodispersed silica and chalk powder. We have studied the cause-effect relationship between the change in the ratio of binding and mineral additives of various compositions, which determines the conditions for the formation of technological and strength characteristics of the projected composite materials with specified performance properties. We have established the presence of regularities in the changes in the properties of CGB, the composition of the hardening products and the microstructure depending on the type and content of gypsum binders of β-and α-modifications, portland cement, multicomponent finely-dispersed mineral additives, the regularity consists in the binding of portlandite, which is released upon portland cement hydration, by the amorphous phase of earth siliconas a part ofnanodispersed powder and chalcedony variety of quartz waste of wet magnetic separation of ferruginous quartzites. This provides a reduction in the basicity of the solidifying system, the intensification of crystal formation, and the formation of newgrowths with a high content of tobormorite-low-basic calcium hydrosilicates that compact the microstructure of the hardening matrix and, as a result, increase the water resistance and stability. It is noted that this mechanism of hydration of CGB minimizes inner stresses and volume deformations, therefore the number of microcracks decreases, which leads to an increase in its efficiency in comparison with the traditionally used gypsum binder and that differs from the traditional portland cement by a fast strength generation.

Influence Of Composition Of A Liquid Phase At Hardening Of Cements

2019 ◽  
pp. 48-55
Keyword(s):  
Liquid Phase ◽  
Calcium Ions ◽  
Cement Hydration ◽  
Hydrate Formation ◽  
Cement Stone ◽  
Concentration Of Ions ◽  
Formation Zone ◽  
High Concentrations ◽  
Intergranular Space

The processes of structure formation of cement stone are considered. The change in the composition of the liquid phase and change in the hydration of polymineral cement over time are studied; the change in the concentration of ions of calcium in the course of cement hydration is determined. The effect of calcium chloride and sodium nitrite additives on the composition of the liquid phase during hydration of polymineral cements was investigated. It is shown that these additives significantly increase the metastable concentrations of calcium ions in the liquid phase of hydrating cements, differently affect the amount of supersaturation of the liquid phase and create different conditions for hydrate formation. The determining role of tricalcium silicate in the character of changes in the composition of the liquid phase and the conditions of subsequent hydrate formation during hardening of polymineral cements has been established. High concentrations of calcium ions in the liquid phase cause the removal of the hydrate formation zone from the surface of the initial cement grains into the volume of the intergranular space, which increases the uniformity of the distribution of the solid component in the volume of the cement stone.

scholarly journals Nano-level management of calcium silicate-hydrate nanoparticles structure formation during portland cement hydration process

2018 ◽  
Vol 196 ◽  
pp. 04012
Author(s):  
Alexander Guryanov ◽  
Vyacheslav Kozlov ◽  
Yulia Sidorenko
Keyword(s):  
Portland Cement ◽  
Structure Formation ◽  
Building Materials ◽  
Cement Hydration ◽  
Structural Parameters ◽  
Control Process ◽  
Hydration Process ◽  
Cement Stone ◽  
Carbonate Sludge ◽  
Portland Cement Hydration

Cement-containing building materials durability depends both on the original clinker composition and on the structure of hydrated portland cement compositions on micro and nanoscales. To calculate structural parameters of silicate-hydrate calcium nanoparticles during portland cement hydration process, the researchers applied the method of small-angle neutron scattering which included distribution of nanoparticles in size, medium nanoparticles radius, fractal dimension. Modifying nanoparticles blending with portland cement composition affects structural parameters of silicate-hydrate calcium nanoparticles. The authors used complex modifying nanoparticles in this study. Nanoparticle composition included a component that served as a filler and a chemically active component that was used as a modifier. The first component was a mixture of alpha oxide aluminum, gamma oxide aluminum and carbonate sludge. The second component presented a mixture of alumoalkaline sludge with alumocalcite sludge. These sludges were of technogenic origin. The research showed that application of complex nanoagents made it possible to control process of silicate-hydrate calcium nanoparticles structure formation, and, as the result, to influence durability of cement stone.

Improvement of Wood-Cement Composition Properties with Microsilica Additive

2020 ◽  
Vol 992 ◽  
pp. 162-167
Author(s):  
E.Yu. Gornostaeva ◽  
N.P. Lukuttsova ◽  
D.I. Dryazgov
Keyword(s):  
Thermal Conductivity ◽  
Compressive Strength ◽  
Silicon Dioxide ◽  
Cement Hydration ◽  
Cement Stone ◽  
Hydration Products ◽  
Maximum Increase ◽  
Calcium Hydrosilicates ◽  
Calcium Silicates ◽  
Composition Properties

The properties and microstructure of wood-cement compositions (WCC) with microsilica (MS) additive for the manufacture of small-pieces wall products are studied. The extreme dependences of mean density, thermal conductivity and compressive strength on the content of microsilica additive are established. The mechanism of microsilica effect on wood-cement compositions is offered. Two interrelated factors (chemical and physical) could be distinguished at that. The first factor includes mainly the interaction of silicon dioxide with lime having released during hydration of calcium silicates, i.e. pozzolatic process. The second factor lies in the compaction of wood-cement compositions and the cement stone structure by means of cement hydration products and silica particles. It is established that introducing 20% of microsilica in the composition results in the maximum increase in ultimate compression strength (3 times). It can be explained not only by forming calcium hydrosilicates, uniformly and densely covering the wood aggregate, but by compacting effect of spherical microsilica inclusions, filling the space between the new cement stone formations and wood aggregate.

Improving the Efficiency of Slag Portland Cement by Reducing Shrinkage Deformations

2020 ◽  
Vol 992 ◽  
pp. 104-110
Author(s):  
Svetlana V. Samchenko ◽  
D.A. Zorin
Keyword(s):  
Portland Cement ◽  
Compression Strength ◽  
Cement Hydration ◽  
Early Stage ◽  
Cement Clinker ◽  
Cement Stone ◽  
Slag Cement ◽  
Portland Cement Clinker ◽  
Granulated Slag ◽  
Portland Slag Cement

The influence of the artificial additive introduced at the joint grinding of granulated slag, Portland cement clinker and gypsum on the Portland slag cement hydration, its compression strength at an early stage and shrinkage deformation is investigated. It was found that in the presence of sulfoferrite clinker there is an amorphization of cement stone structure with formation of stone with high density and strength in early setting. The open porosity of the hardened paste is reduced by 13 – 15 % in comparison with plain Portland slag cement. The samples strength increases by 1.55 - 1.78 times at grade stage, by 15.5 - 19.4 % in bending and by 6.4 - 11.2 % in compression.

Mechanism of Interaction between Concrete Cement Matrix and Mineral Additive Particles

2020 ◽  
Vol 992 ◽  
pp. 98-103
Author(s):  
S.M. Rakhimbaev ◽  
A.A. Logvinenko ◽  
M.I. Logvinenko
Keyword(s):  
Cement Matrix ◽  
Cement Stone ◽  
Aggressive Interaction ◽  
Granulated Blast Furnace Slag ◽  
Additive Particles ◽  
Mineral Additive ◽  
Calcium Hydrosilicates ◽  
Mechanism Of Interaction ◽  
Internal Strains

A nature of the forces, which act between the concrete cement matrix and entrained mineral particles (ground additives, fine and coarse additives), has been considered. It has been shown that the adhesion between them is attributable to the forces of different nature. The strongest adhesion between the particles of the hydrated binding material and mineral additives occurs, when materials, which react with calcium hydrate of the pore fluid, are used. The latter includes glassy wollastonite, which is part of granulated blast furnace slag. Even at a temperature of 25 °C, an aggressive interaction between them is observed and firm chemical bonds occur. In such case, the dissociation energy of such bonds ranges from 400 to 500 kJ per bond. Between materials, such as crystalline wollastonite and the concrete cement matrix, there is an epitaxial coalescence of its basal surfaces and tobermorite calcium hydrosilicates formed by the interaction of the binder with water. A direct contact is required between the reacting surfaces for such interaction. This is implemented by virtue of the bond, which is attributable to contraction forces resulting from shrinkage strains of the hydrated particles in the concrete cement matrix. Internal strains of the cement that are attributable to contraction, shrinkage, and carbonization of hydrated compounds result in the cement sheath contracting around the aggregate grains and steel reinforcement. Internal strains of the cement stone can be calculated using the Lame equation. We have reviewed the role of the factors, which are most critical for contraction of the cement ring around coarse particles of the aggregate and for stress-strain properties of artificial conglomerates, which have different composition and purpose.

Role of the filler on Portland cement hydration at early ages

2012 ◽  
Vol 27 (1) ◽  
pp. 82-90 ◽  
Author(s):  
V. Rahhal ◽  
V. Bonavetti ◽  
L. Trusilewicz ◽  
C. Pedrajas ◽  
R. Talero
Keyword(s):  
Portland Cement ◽  
Cement Hydration ◽  
Portland Cement Hydration
Sign in / Sign up

Export Citation Format

Share Document