Strength Of Cement Stone Research Articles

The use of finely ground slag in portland cement with mineral additives

The method of introducing of finely ground granulated blast furnace slag (GBFS) in the composition of the cement as a result of dry mixing of the material with the additive is considered. The aim of the research was to study the effect of the addition of finely ground slag on the construction, technical, physical, mechanical, and structural characteristics of cement with mineral additives. The setting time was studied, the normal density of the cement paste with the addition of finely ground slag was determined. The dependences of the strength and porosity of the cement stone on the time of hydration of samples are built. The strength of the cement was determined by the national standard GOST 30744-2001. The porosity of the cement stone was determined by saturating the samples with an inert liquid. It has been established that the introduction of 3–5% of slag 1 and 1–3% of slag 2 provides an increase in the strength of cement stone during the first days of hardening on average by 37–44%; at the grade age - by 26–30%, decrease in porosity — by 17–28%. It is shown that the introduction of finely ground slag additives compacts and strengthens the structure of the cement stone. It has been established that grinding GBFS to a size of 1 μm (slag 1) is impractical because the obtained research results are comparable with the results when slag 2 is introduced into the cement composition.

ФИЗИКО-ХИМИЧЕСКИЕ ПОДХОДЫ К РАЗРАБОТКЕ ЭФФЕКТИВНЫХ ОРГАНОМИНЕРАЛЬНЫХ ДОБАВОК ДЛЯ БЕТОНА

Представлены физико-химические подходы к разработке эффективных органоминеральных добавок для регулирования свойств бетонных смесей. Углублены представления о влиянии свойств минеральных компонентов на структурообразование цементного камня. Установлена связь результатов физико-механических испытаний цементного камня с его микроструктурой и свойствами минеральных компонентов. Показана возможность сохранения эффективности пластифицирующих добавок за счет частичного замещения поликарбоксилатного пластификатора на более доступное химическое сырье. Разработанные комплексные органоминеральные добавки позволяют модифицировать структуру цементного камня и улучшать физико-технические свойства бетона.
 Работа выполнена при финансовой поддержке РФФИ, грант № 18-29-19033 мк

Efficiency in Cement and Cement Concrete of Dispersed Granitic Rock

The paper presents results of investigations on the dispersion (grinding) process in a ball mill and it also shows an effect of dispersed granitic rock (granite screenings of RUPP “Granit”, Brest region) used as a mineral additive on cement properties, hardening kinetics and cement stone strength, morphology of cement hydration products in the presence of the granitic rock. Complex studies including data of X-ray phase and derivatographic analyses have revealed that granitic rock material does not change morphology of new formations these are reaction products obtained due to reaction of binder clinker portion with water. They are identical to those that are formed due to reactions of a no-dosage (clean-bite) binder with it. At the same time it has been established that when 10–20 % of granite screening grinded up to Sud ~ 3000 cm2/g (0.3 m2/g) have been added to cement strength of cement stone is increased by 20–25 %, and the amount of chemically bound water in clinker component of the binder is increased by 10–15 %. The paper has substantiated a hypothesis of the “crystallization centers” effect which is revealed by fractions of grinded screening £0.3 μm (£3000 Å). The fractions constitute an amount of ~15 % of the screening mass. This hypothesis has been proved by the above-mentioned data on the increase in cement stone strength and amount of chemically bound water in their presence when samples are hardened in normal-humid conditions, in water and after steaming. There is also an obvious increase in strength of cement stone on a binder with this additive (in 2–2.5 times in 1–3 days of hardening) under conditions of “inhibition” in cement hydration reactions due to introduction of a chemical additive that is lignosulphonate technical additive in the cement paste with enhanced dosage (0.3 % of the cement mass).

STRUCTURE CHANGES IN THE REFRACTORY CALCIUM-ALUMINATE CONCRETES

The influence of both the organic and inorganic additives to the calcium aluminates on the cement hydration and the cement stone's structure formation both at the normal and elevated is regarded in the article. The investigating results are given for the phase transformations in the hardened calcium aluminate samples being heated between 20 and 900 °C. The structure change mechanism and the reasons of the cement stone's strength reduction under the high temperature's influence are described. Ill. 3. Ref. 22. Tab. 3.

Effect of colloidal nanosilica on early-age compressive strength of oil well cement stone at low temperature

The compressive strength of cement stone rises slowly when cementing marine shallow section at low temperature, resulting in increased drilling cost and risk. This paper presents results of experimental study that was conducted to investigate the effect of low temperature on early-age compressive strength of cement stone admixed with colloidal nanosilica. The compressive strength of cement stones was measured after aging at 4 °C for 1, 3, and 7 days respectively. The hydration products of different aging cement stone were analyzed by X-ray diffraction and Fourier Transform infrared spectroscopy, and the microstructures were observed by scanning electron microscopy. In addition, the hydration exotherm of colloidal nanosilica modified cement slurry during hydration process was tested at 20 °C. The results indicated that the compressive strength of cement stone significantly improved by colloidal nanosilica. Interestingly, colloidal nanosilica retarded the initial hydration, and then promote the hydration process afterward. The mechanism of colloidal nanosilica to improve the compressive strength of cement stone was that colloidal nanosilica consumed calcium hydroxide to produce additional calcium silicate hydrate, filling large pores and cracks inside cement stone. More importantly, nanosilica particles provided nucleation sites of cement hydration and modified the internal structure of the hardened stone. The improvement of early-age compressive strength of oil well cement stone is beneficial to saving costs and reducing risk.

FEATURES OF ACCIDENTS AND COMPLICATIONS ELIMINATION BY SIDE TRACKING METHOD WHILE ULTRADEEP DRILLING

While ultradeep wells construction there is often a need to drill a new well as a way to eliminate various accidents and complications. The experience of drilling new wells during the construction of Tyumenskaya (7502 m) and Yen-Yakhinskaya (8250 m) ultradeep wells in the north of Western Siberia is considered in the article. During the construction the main complications requiring drilling of new wells arose due to adherence of a drill string at a depth below 6 km. At present, for normal depths, effective well trajectory control systems have been developed - rotor-driven systems, but they cannot be used for technical pur-poses at high pressures and temperatures of ultradeep horizons. Drilling from a cement plug installed with the use of the USHTS-2-200 cement, designed for high thermobaric condi-tions and allowing to create the necessary density of cement stone, was not successful, since the compressive strength values for rocks in the interval of drilling are 51-118 MPa, exceeding the strength of cement stone in 6-10 times. To ensure the strength of the support-ing bridge, there were used aluminum pipe fittings (ABT) with a diameter of 147 mm with protective thickenings, the strength of aluminum for compression corresponds to 320-350 MPa. During the construction of the Tyumen well, the need to drill a new well occurred three times, Yen-Yakhinskaya - once. In all cases, the drilling was held success-fully.

The use of amorphous silica-alumina-based additive in the adhesive dry mixes of building materials

Proved the possibility of using amorphous aluminosilicate as a modifying agent for the adhesive dry mixes. Are given the data on the microstructure and chemical composition of the amorphous aluminosilicates. Installed , that the microstructure of the synthetic additives is characterized by particles of round shape, dimensions 5,208-5,704 μm, Also there are particles of elongated shape in size 7.13-8.56 μm. Predominate chemical elements O, Si, Na, S, and Al in quantity 60.69%, 31.26%, 24.23%, 18.69% and 8.29% respectively. Described the character changes in the rheological properties of cement-sand mortar, depending on the percentage of additives. Determined, that the introduction in the cement-sand mortar the additive based on amorphous aluminosilicate leads to higher values of plastic strength. Are given the model of cement stone strength using synthetic additives in the formulation. The results of the evaluation of the frost resistance of cement-based tile adhesives with the use of amorphous aluminosilicates as a modifying additive are presented. In the article is determined the mark on frost resistance of tile glue and frost resistance of the contact zone of tile glue. The evaluation of the performance properties of the layer of tile adhesive on the basis of cement, dry mixes. The calculation of the value of displacement of the adhesive layer made on the basis of the developed recipes cement dry mixes applied to a vertical surface. Experimental data obtained values of displacement tiles relative to the substrate. Described the results of physical and mechanical properties of tile adhesive made on the basis of the developed adhesive dry mix formulations.

Investigation of the Effect of Microwave Irradiation of Cement Slurries on the Strength of Cement Stone and Concrete

Investigation of the Effect of Microwave Irradiation of Cement Slurries on the Strength of Cement Stone and Concrete

Исследование химического состава «летучей» золы и ее влияние на прочность цементного камня

Статья посвящена проблемам, связанным со снижением негативного воздействия золошлаковых отходов ТЭЦ Казахстана на окружающую среду. Вырабатываемая в больших количествах летучая зола как продукт сгорания топлива на энергостанциях отрицательно влияет на внешнюю среду, загрязняя воздух, почвы, сточные воды и т.п. В статье приведены результаты химического состава золошлаковых отходов. Рассмотрены возможные пути использования золы. Также изучен фазовый состав цементного камня с добавлением летучей золы с помощью современных методов анализа: рентгенофазовый и рентгенофлуоресцентный. Было выявлено, что к основным макроэлементам золы относятся Si, Al, Fе, О, Ca, Ti, Mg, S, K, Na. Помимо изучения размеров и форм микросфер в работе ставились задачи определения видов термоактивных фаз, составляющих цементного камня при термообработке; изучение структурных изменений при термообработке. Рентгенофазовый анализ по исследованию зольных микросфер показал следующие фазы: муллита Al6Si2O13, кварца SiO2 и аморфной стеклофазы. Применение золы как источника оксидов алюминия и кремния не только позволит снизить использование невозобновляемых ресурсов, но и получить материалы с улучшенными теплофизическими характеристиками (прочность, термостойкость и теплопроводность). Выбор оптимального количества золы уноса взамен части цемента способствует образованию желательной структуры цементного камня.

Influence of microwave irradiation of cement mixtures on the strength of cement stone and concrete

The influence of microwave irradiation of mixtures on the strength of cement stone and concrete was studied. Created at NRNU MEPHI experimental installation for the investigation of microwave effects on imperfect dielectrics and semiconductor materials was the source of radiation. It is shown that on the twenty-eighth day after mixing, the strength of the cement stone increases by 1.2 times, and that of concrete by 2.2 times.

Properties and self-healing behavior of oil absorbent microspheres modified cement

This paper concerns the properties and self-healing behavior of cement composites modified by oil absorbent microspheres with fumed silica shell. These microspheres, prepared by Pickering polymerization, possessed excellent properties, such as uniform particle size, good hydrophilicity and fine thermal stability. Furthermore, the effect of these microspheres on the properties of cement slurry was studied. The results showed that these microspheres had good compatibility with cement slurry, except for a slight effect on the consistency of cement slurry and the compressive strength of cement stone. At last, we derived the mathematical formulation of valid sealing for microcracks in self-healing cement, and measured sealing pressure under different filling conditions. The self-healing cement would guarantee the health, safety and high efficiency in the process of oil and gas production.

PECULIAR PROPERTIES OF STRUCTURAL FORMATION OF CEMENT COMPOSITES IN THE PRESENCE OF FUELEROID TYPE CARBON NANOPARTICLES

The paper deals with the application of fulleroid carbon nanoparticles (FCN) for the cement com-posites modification. In particular, the thermokinetic analysis was performed to assess the change in the rate and completeness of the cement hydration when the nanomodifier was introduced into it. The study of exothermic heterogeneous interactions and thermal effects in the binder - water - nanomodifier system allows one to estimate the hydration rate and depth and to assess the degree of nanomodifier’s influence. The conducted studies revealed the increase in the hydration temperature when carbon nanoparticles are introduced into the cement dough, while the induction period is prolonged, that indicates a more complete course of the reactions. It is confirmed by the results of qualitative X-ray structural analysis. The dynamics of decrease in calcium silicate peaks characterizes the completeness of hydration and binding of portlandite, that explains the increase in the modified cement stone strength. Microstructural analysis allows to detect the structure characteristic of control samples with a large number of large chaotically located crystals, the bulk of which is formed on the first day of solidification. Under the same conditions, the modification of the cement stone contributes to the creation of the more dense spatial structure consisting of small crystalline hydrate formations. All that process positively influences the formation of the rigid matrix with a smaller number of pores, which determines the in-crease in strength and durability of cement stone and concrete on its basis.

Phase composition and strength of cement stone with a complex additive

Ecologically friendly construction is impossible without the use of materials that are characterized by a low emission of dangerous substances from the surface and have other appropriate properties. A solution of the problem related to the elaboration of special measures taken to reduce the emission of ammonia from construction materials and the structures manufactured using the Portland cement has been offered. An optimized composite dope was developed and optimized for the Portland cement composition that contains the nitric acid calcium, which is one of the ingredients that can considerably reduce the concentration of nitrogencontaining compounds, making thus the construction materials less dangerous to the human health. Strength characteristics of the cement stone with the composite dope were studied and it was established that a level of the intensification of a gain in the strength is rather significant and by the seventh day the hardening exceeds the values peculiar for the dope-free compositions at an age of 28 days by more than 45 %.

IMPACT OF FORMULA-TECHNOLOGICAL FACTORS ON CONCRETE STRENGTH INDICATORS FOR INJECTING WITH TWO-STAGE EXPANSION

Abstract. Objectives The aim of the study is to clarify the dependence of the cement stone strength on additional porosity that is formed owing both to the cement stone’s development of free deformations and the expansion of the hardening concrete in the second stage as caused by the action of the expanding additive. Method The study is based on the introduction of a sulphoaluminate-type expanding additive in the composition of a binder based on alumina cement, natural gypsum stone and nitrilotrimethylphosphonic acid. Results It is shown that an important role is played in the technology of expanding concrete not only by the degree of expansion of the cement stone, but also by its strength, both during the development of deformations and following stabilisation. Among factors influencing the kinetics of hardening are not only recipe-related (composition and dosage of the additive, mineralogical composition of Portland cement clinker, composition of the concrete, presence of chemical additives), but also technological (fineness of cement grinding, hardening temperature, etc.) that makes the management of the processes of structure formation quite complex. The dependence of the strength of cement stone on the additional porosity formed due to the growth of the cement stone own free deformations and expansion of the hardening concrete in the second stage due to the action of the expanding additive is revealed; dependence of the influence of kinetics of the structure formation regulator - nitrilotrimethylphosphonic acid - on the consistency of the development of the intrinsic free expansion deformations and the formation of the strength of the cement stone in the second stage; the dependence of the strength of the cement stone on the additional porosity formed due to gas evolution and expansion of the mixture in the first stage due to the action of the gas-forming additive; the influence of the constraint of expansion on the formation of the structure of cement stone and its strength; the effect of hardening conditions on the strength characteristics of concrete with a two-stage expansion. Conclusion The process of expansion under the conditions of deformation free development is accompanied by an increase in the porosity of the cement stone of up to 9% and a regular decrease in the strength of the cement stone by compression up to 19.3%. The effect of hardening conditions on the compressive strength of concrete with a two-stage expansion is established: when exposed to air for 28 days at a temperature of 5 oC, the strength decreases to 50% relative to normal conditions, and at a temperature of 35 oС - to 14 %. With water aging the strength is reduced to 33% due to intensive expansion in the second stage. The dependence of the ratio of tensile strength to compressive strength for concretes with a two-stage expansion is specified, taking into account the hardening conditions.

Use of the Additive Based on Amorphous Silica-Alumina in the Adhesive Dry Mixes

This article proves the possibility of using amorphous aluminosilicate as a modifying additive for the adhesive dry mixes. The data is given on the microstructure and chemical composition of the amorphous aluminosilicates. This article described the character changes in the rheological properties of cement-sand mortar, depending on the percentage of additives. The model of cement stone strength using synthetic additives in the formulation is illustrated. The results of physical and mechanical properties of tile adhesive made on the basis of the developed adhesive dry mix formulations are described.

The effect of carbon fiber additive on early hydration of calcium aluminate cement

The effect produced by the short carbon fiber additive on the hydration of calcium aluminate cement under the ambient temperatures of 10, 20 and 30 °C is investigated. The calorimetric analysis of the cement paste has shown that the carbon fiber additive increases heat release and decreases the induction period of hydration at the ambient temperatures of 10 and 30 °C, while at the temperature of 20 °C, this period is increased. X-ray diffraction and thermal analysis have shown that carbon fiber additive does not have any influence on the composition of the formed hydrates; however, their amount depends on it. It has been also found that a dense layer of cement hydrates is formed around the fibers. Due to the positive effect of carbon fiber additive on cement hydration and microstructure, as well as its reinforcing effect, the compressive strength and the bending strength of cement stone are increased by 3–23 and 13–70 %, respectively, depending on the ambient temperature.

SODIUM CITRATE INFLUENCE ON FORMATION OF CEMENT STONE IN THE ALUMINOUS BINDER

The paper deals with the effect of sodium citrate on the formation of a cement stone in the aluminous binder. Formation of cement stone framework in cement hydraulic binder is accompanied with complicated physical and chemical processes of interphase interactions and dispersion, these processes are predicated on qualitative and quantitative composition of the cement mortar, continuous changes in its properties from preparation stage till curing. Addition of sodium citrate to tempering water enhances hydration of both Portland cement and calcium aluminate cement. Process pertaining to an increase of cement hydration rate is considered as a consequence of destruction in surface formations and exclusion of damping effect in respect of hydration rate and hydrolysis of products resulted from interaction of clinker material with tempering. It has been established that sodium citrate makes it possible to control processes of hydration, hydrolysis, binding and curing for cement mass. High degree of hydration of aluminous cement in the presence of sodium citrate provides fast binding and curing of binder, low porosity and rather high compression breaking strength of cement stone for all curing stages. An increase in concentration of sodium citrate in cement mixture up to 10 % of the cement mass exerts an influence not only on the process of cement mortar liquefaction, reduction of time for cement mass setting and hardening but also increases compression strength of cement stone. An analysis of the structure for cleavage surface of cement stone gives ground to declare that the addition of sodium citrate provides cement stone sealing and reduces its water absorption.

Research on the influence of K-PAM on the microstructure of cement slurry

In this paper, liquid nitrogen freezing and vacuum drying are used to sublimate the water in cement slurry, so that the microstructure of cement slurry can be maintained and the hydration process can be stalled. The microstructure changes of cement slurry containing potassium polyacrylamide (K-PAM) are then observed. The conclusion of the incompatibility mechanism is drawn by comprehensive analysis of the results of the molecular structure of K-PAM, aggregation stability and microstructure of cement slurry. Experimental research shows that a K-PAM molecular chain can adsorb a plurality of cement particles, resulting in an adsorption bridging effect. After reacting with Ca2+ in cement slurry, K-PAM turns into polypropylene calcium, which forms a needle-like structure in the cement slurry. Such a needle-like structure is aggregation and staggers to form a net-like structure, causing cement slurry flocculation. Hydrophilic groups of K-PAM and water interact with each other through hydrogen bonding, which forms a layer of solvent membrane on the surface of the cement particles, hindering the contact between water and cement particles. This can reduce the hydration reaction rate, and finally decrease the compressive strength of cement stone.

The influence of sulfomethyl phenol formaldehyde resin (SMP) on cementing slurry

The poor compatibility between drilling fluid additives and cementing slurry can lead to downhole accidents and inferior cementing quality. Therefore, this paper intends to study on the influence of sulfomethyl phenol formaldehyde resin (SMP) on cement slurry. This paper studies the influence of SMP on the rheological property, thickening time, aggregate stability of cement slurry, and compressive strength of cement stone, and studies the influence of SMP on the concentration of metal ions of cement slurry. And this paper analyzes the influence of SMP on the microstructure of cement slurry via vacuum freeze-dry technology of liquefied nitrogen combined with environmental scanning electron microscope. Finally draw the conclusions: SMP and metal ions with high valence (Fe3+, etc.) set off complexation reaction in cement slurry, which increases the molecular weight of complex compound adsorbed on the surface of the cement particles. Meanwhile, Zeta potential is decreased after SMP is added to cement slurry, and the cement slurry becomes thickened as the particles move from agglomeration and diffusion equilibrium towards aggregation direction. After SMP and metal ions with high valence (Fe3+, … etc.) set off the complexation reaction in cement slurry, a dense “film” is formed on the surface of the particles to prevent cement particles from contacting free water, which will reduce the hydration rate of cement particles, increase the thickening time of cement slurry, and reduce the compressive strength of the cement stone to only two-fifth of the compressive strength of cement stone with original formula.

Strength properties of cement slurries with lightweights applied in oil and gas wells

The article is focused on the cement stone strength properties resulted from lightweight cement slurries that meet GOST-1581-96 (state Standards) requirements. Exfoliated vermiculite, hollow aluminosilicate microspheres (HAMs), diatomite and perlite were used as lightweighting additives.