Special Cement Research Articles

The development of an expansive type special cement bonded investment powder for castings of non ferrous metals and alloys

ABSTRACTAn attempt has been made to develop an investment powder which expands significantly in the setting period to meet the solidification shrinkage of most metals and alloys. Investment powders consisting of tricalcium aluminate, quartz, various sulphate bearing compounds and a small amounts of controlling agents (additives) were used in the preparation of the block investment molds. A413 Al-Si (Etial 140) alloy was melted and poured in these molds to cast a test specimen of a special geometry. The preliminary results show that it is possible to produce dimensionally accurate castings by using expansive type investment powders. Samples cast into block investment molds prepared from ordinary non-expansive investment powder were smaller than the pattern size, while those poured into molds produced from expansive type powders were the same size or greater than the pattern size.

Hydration at early ages of styrene-butadiene copolymers cementitious systems

Oil well cementing is a vital operation to assure casing stability and zonal isolation for oil and gas exploration. However, some scenarios demand the cemented region to withstand high thermal gradients and imposed deformations, as occurs in the case of oil wells subjected to cyclic steam injection at temperatures up to 250 °C, to reduce oil viscosity and to increase well pressure to facilitate heavy oil recovery. In this paper, the hydration of ductile special cement systems using styrene-butadiene latex (SBR) and carboxylated styrene-butadiene latex (XSBR) addition was studied by conduction calorimetry. The resulting heat flow curves, presented in log–log plots, were used to analyze the influence of those copolymers on the hydration stages of three families of cement pastes of different complexity. The simpler cement systems (SCCS) contained water, oil well Portland cement class G and SBR or XSBR in its composition. In medium complexity systems silica fume was added and in the higher complexity ones (HCCS), superplasticizer as well. The primary objective of adding those copolymers into the Portland cement paste is to obtain higher ductility properties after setting, silica fume to have good thermal stability up to 300 °C, while superplasticizer was added to guarantee good workability. Rheological tests were carried out to evaluate the effect of the copolymers on the composite viscosity. Thermogravimetric analysis of selected SCCS and HCCS samples was performed to quantify the main formed phases up to 24 h of cement hydration. From the obtained results, it was noticed that SBR and XSBR addition substantially affects hydration kinetics at all early age stages. Starting from pre-induction and induction periods, the main observed effect during these stages, was related to the increased viscosity of the pastes, which was higher in XSBR containing pastes, retarding the hydration reactions of respective following stages, when compared to pastes with the same cementitious matrix without copolymer addition.

Electrokinetic nanoparticle injection for remediating leaks in oil well cement

This paper presents experimental results on injecting nanoparticles into a hardened oil well cement with electromigration technique. Oil well cement is a special cement type used in underground constructions to protect steel casing of oil wells, CO2 storage wells or oil and gas platforms. Due to the technological reasons, the hardened cement is characterized with a high initial porosity. Further distressing and fracturing occurs in the hardened cement originating from the harsh underground environment which includes elevated pressure and temperature. This leads to severe leakages of the stored media and puts the steel casing to the risk of corrosion.The paper proposes to use a non-destructive remediation technique for the cement repair based on the electrokinetic injection of nanoparticles into the pore and crack space in the material. It shows the efficiency of the technique and presents results from injections with a variety of differently sized nanosilica, microsilica and nanoalumina particles. Characterization of the treated samples was based on microscopy observations, electrical measurements, the change in their open porosity and nanopore surface area assessed by the BET technique. It was found that the electrokinetic process and driving of particles in samples is very efficient and reduces the sample porosity by about 4–7% with respect to the initial porosity of intact specimens and 5–8% on aged samples. The BET analysis confirmed reduction of the inner pore surface area in the treated samples. Increasing level of agglomeration of particles on the surface as well as in the inner pores was observed during electrokinetic treatment and documented with the electric current measurements.

THE EFFECT OF AGING ON MICROSHEAR BOND STRENGTH OF RESIN CEMENT TO MONOLITHIC ZIRCONIA

Purpose. Successful long-term bonding to zirconia ceramic remains a challenge, requiring special cements and treatments, which might negatively affect the ceramic. The purpose of this study was to evaluate the durability of micro-shear bond strength between resin cement containing phosphate monomer and zirconia ceramic submitted to different surface treatments before and after aging.Material and methods monolithic zirconia (Bruxzir Glidewell, California, USA) was selected as the substrate material. The ceramic surfaces, were either left untreated as-sintered (Group NT), silica coated with Rocatec soft system (3M/ESPE, USA) (Group CT), or treated with Alloy Primer (Kurary, Japan) (Group PR). They were bonded with a dual-cured resin cement; Panavia v5 (Kurary), using an adhesive system (Clearfil SE Bond). A micro-shear bond test was carried out to measure the bond strength of the resin cement to the zirconia surface. Samples were tested in a universal testing machine at a crosshead speed of 0.5 mm/minute before and after 90 days of water storage and 6000 thermal cycles (dwell time, 30 seconds). Statistical analysis was performed using a two-way ANOVA model, at pResults. Mean microshear bond strength ranged from 14.39 to 21.59 MPa after 3 days and from 5.64 to 20.42 MPa after aging. Water storage and thermal cycling decreased bond strength significantly for NT and PR groups, while it had no significant effect on CT group. Early bond strength was highest with CT and PR groups with no significant difference between them, and they were both statistically significantly higher than NT group. SEM analysis showed an increase in interfacial adhesive failure after aging.Conclusions. Within the limitations of this study, it was concluded that silica coating and application of a chemical primer produced higher bond strengths to resin cement than leaving zirconia untreated. Aging significantly reduced the bond strengths for the untreated and primed zirconia, while silica coated zirconia remained stable and was not affected.

Correlation factor between heat of hydration and compressive strength of common cement

In this paper the results of the research of common and special cements were presented. The scope included about 200 samples of industrial cements produced in 9 manufacturing plants in Poland according to cement standard PN-EN 197-1.Obtained results indicate that for different cement plants strong correlation between the results of heat of hydration tests and the compressive strength after 28days of hardening of Portland cement CEM I without mineral additions is observed, irrespectively from strength class of that cement. Even better correlation is observed for particular cement plant. However, in the case of blast furnace cement such relationships are in the borderline between weak and moderate for different cement plants and moderate within one manufacturing plant.Achieved for particular cement plant high correlation factors allow to estimate with very low error the standard compressive strength of cement after 28days of hardening on the basis of heat of hydration tests just after 3days. It especially applies for Portland cement CEM I.

Investigation of multiphase equilibria in the subsolidus of BaO–CoO–Fe2O3–Al2O3 system

One of the most important problems related to the development of new nonmetal materials and their performance characteristics is to predict the phase composition. The most comprehensive information on phase interactions and the thermodynamic stability of phase combinations is given by the state diagrams. The materials synthesized in the system subsolidus domain can be predicted the most accurately, because their sintering occurs without participation of the melt. Due to the above fact, the studies of the subsolidus structure of BaO – CoO – Fe 2 O 3 – Al 2 O 3 system are of great interest, because on the basis of this system we can obtain a huge amount of nonmetal materials with prescribed properties, for example ferrimagnetic materials to protect from electromagnetic radiation, because the system compounds have cementing, refractory and ferrimagnetic properties. To study the structure of BaO – CoO – Fe 2 O 3 – Al 2 O 3 system in detail the authors summed up already known data on the thermodynamic constants of system compounds. This allowed us to do the thermodynamic analysis of multiphase equilibrium processes that occur in the subsolidus of BaO – CoO – Fe 2 O 3 – Al 2 O 3 system that was used as a basis for the plotting of the state diagram for the subsolidus domain of the system. A promising field for the application of obtained data is the cement production technology. The produced cement can be used independently and as a binding material to produce special cements and materials that retain their properties when exposed to the action of high-frequency electromagnetic radiation.

Biodeterioration of the Cement Composites

The destruction of natural and synthetic materials is the spontaneous and irreversible process of the elements cycling in nature. It can by accelerated or decelerated by physical, chemical and biological influences. Biological influences are represented by the influence of the vegetation and microorganisms (MO). The destruction of cement composites by different MO through the diverse mechanisms is entitled as the concrete biodeterioration. Several sulphur compounds and species of MO are involved in this complex process. Heterotrophic and chemolithotrophic bacteria together with fungi have all been found in samples of corroding cement composites. The MO involved in the process metabolise the presented sulphur compounds (hydrogen sulphide, elemental sulphur etc.) to sulphuric acid reacting with concrete. When sulphuric acid reacts with a concrete matrix, the first step involves a reaction between the acid and the calcium hydroxide forming calcium sulphate. This is subsequently hydrated to form gypsum, the appearance of which on the surface of concrete pipes takes the form of a white, mushy substance which has no cohesive properties. In the continuing attack, the gypsum would react with the calcium aluminate hydrate to form ettringite, an expansive product. The use supplementary cementing composite materials have been reported to improve the resistance of concrete to biodeterioration. The aim of this work was the study of the cement composites biodeterioration by the bacteria Acidithiobacillus thiooxidans. Experimental works were focused on the comparison of special cement composites and its resistance affected by the activities of used sulphur-oxidising

Measurement of Volume Changes of High Performance Cement Based Composites

Performed research work is focused on the experimental determination of volume changes of high-performance concrete. Studied topic is an essential problem of all cement based composites because of its influence to mechanical and durability properties due to crack formation. Special high-performance cement based mortars are often used for quick rehabilitation and renovation of current concrete structures where minimal level of total volume changes is required. Interpretation of final results is highly dependent on the way of measuring, as it is documented in the present experimental program.

The Time Factor Effects of the Drilling Cement Pastes on its Working Characteristics by Increasing Temperature

By drills realization in order to obtain petroleum and natural gas, the isolation of the individual layers along the height of drilling activity is the most important factor for judging the serviceability and follow-existence of the finished work. The special cements for drilling are used as plugging material suited according to API Spec. 10A (American Petroleum Institute).Recently, in the institute we have dealt with the impact of the time factor on the pressure characteristics and stress-strain diagrams of samples from the drilling mud additives [1], due to the time factor for composites containing drilled and subsequently in practice applied aggregates [2] and also the characteristics of a drilling cement made for lower and laboratory increased temperatures [3]. In the article we deal with a similar topic. Results for tension and pressure characteristics gathered in time up to 120 hours were used to generate the stress-strain diagrams, static and dynamic modules in compression. Heat background of tests answers the real terms of drilling activities up to 1200 m. In conclusion, we will compare the results with available foreign results.

Basic Physical and Mechanical Properties of Composites Based on Three Different Cements

This article is focused on cement based composites. Two cements differing in mineralogical composition are utilised as main binder in composites mixtures. Results of measured physical parameters of studied materials are presented. For the sake of comparison, a reference material with Portland cement was also prepared. Basic physical properties (measured by water vacuum saturation method and by helium pycnometry), characterizations of pore system (determined by mercury porosimetry) and mechanical properties are the matter of this study. Composites show various open porosity; the results of open porosity of materials containing special cements show higher values, in comparison with composite based on Portland cement. This fact of course influences other material characteristics - mainly mechanical properties.

Performance characteristics of the open-graded asphalt concrete filled with a special cement grout

This paper presents a performance of the open-graded asphalt concrete filled with a special cement grout in the road structures, introduces practical examples of the usage of this technology and defines the main properties. In addition, laboratory design of asphalt mixtures filled with special grout is researched. Finally, the results obtained from various laboratory tests are evaluated. The paper contains the open-graded asphalt concrete filled with a special cement grout mix design procedure and results of stiffness measurement, low temperature properties, permanent deformation and skid resistance. Open-graded asphalt concrete filled with a special cement grout mixture is compared to the commonly used asphalt mixes. The open-graded asphalt concrete filled with a special cement grout showed better results than the commonly used asphalt mixes by the stiffness and resistance to the permanent deformation characteristics but behavior at the low temperatures is slightly problematic.

Effect of Selected Alternative Fuels and Raw Materials on the Cement Clinker Quality

Abstract The article deals with the study of the effects of alternative fuels and raw materials on the cement clinker quality. The clinker quality was expressed by the content of two principal minerals alite C3S and belite C2S. The additions of alternative fuels ashes and raw materials, in principle, always increased the belite content and conversely reduced the amount of alite. The alternative fuels with high ash content were used such as the meat-bone meal, sewage sludge from sewage treatment plants and paper sludge and the used alternative raw materials were metallurgical slags - granulated blastfurnace slag, air cooled blastfurnace slag and demetallized steel slag, fluidized bed combustion fly ash and waste glass. Meat-bone meal, sewage sludge from sewage treatment plants and paper sludge were evaluated as moderately suitable alternative fuels which can be added in the amounts of 2.8 wt. % addition of meat-bone meals ash, 3.64 wt. % addition of sewage sludge ash and 3.8 wt. % addition of paper sludge ash to the cement raw mixture. Demetallised steel slag is suitable for production of special sulphate resistant cement clinker for CEM I –SR cement with addition up to 5 wt. %. Granulated blastfurnace slag is a suitable alternative raw material with addition 4 wt. %. Air cooled blastfurnace slag is a suitable alternative raw material with addition 4.2 wt. %. Waste glass is not very appropriate alternative raw material with addition only 1.16 wt. %. Fluidized bed combustion fly ash appears not to be equally appropriate alternative raw material for cement clinker burning with less potential utilization in the cement industry and with addition 3.41 wt. %, which forms undesired anhydrite CaSO4 in the cement clinker.

Multichannel Laboratory Device for Measurement of Smart Concrete Material Properties

This article deals with the measurement system and the use of special cement composites with carbon particulates. The type of carbon particulates consequently determines the electrical properties of cement composite material. These materials can be used for electric heating, electromagnetic shielding or stress measurement. Strain properties can be used to measure the deformation of concrete structures (bridges, beams, pillars) or for weighing-in-motion of road vehicles. This article describes novel laboratory equipment which is designed for multichannel dynamic and long-period material stability measurements.

Solid-state synthesis of SrY2O4 and SrSm2O4

The course of solid-state synthesis of SrY2O4 and SrSm2O4 is described in this work. The processes during the thermal treatment, the mechanism and kinetics, the reactivity with water and the thermal stability of products were investigated by thermal analysis, isothermal calorimetry, infrared spectroscopy and scanning electron microscopy. Since solid-state synthesis does not show any significant effect on DTA, the course of synthesis was observed by the expansion of specimen. The kinetics of formation of SrY2O4 and SrSm2O4 is driven by the rate of reaction of 2nd order (g(α) = (1 − α)−1 − 1) and requires the Ea of 450 and 918 kJ mol−1, respectively. The heat released by the reaction of SrSm2O4 with water is significantly higher than that of SrY2O4. The introduction of Al2O3 to SrY2O4 led to the formation of monoclinic phase of Sr6Y2Al4O15. The hydraulic activity of these phases can be applied for the preparation of special inorganic cements.

Study of the Evolution of Phase Calcium Aluminate through the Method for Polymeric Precursors C<sub>12</sub>A<sub>7</sub>

The synthesis of ceramic materials from polymeric precursors has been the subject of numerous studies due to lower energy cost compared to conventional processing. The study aims to research and develop synthesis of calcium aluminate powders via the polymeric precursor method, in order to obtain the pure phase of hepta-aluminate dodecálcio (C12A7) with mayenita mineral name, since it has applications like: special cements and components for high temperature fuel cells. A study of the evolution of crystalline phases by X-ray diffraction was performed, the vibrational modes of atomic location in crystalline phases were studied by micro-Raman spectroscopy was also performed and images from scanning electron microscopy. From the characterizations carried out on the material can be seen that the sintering temperature of 1200°C was obtained pure phase, so the choice of synthesis shown to be effective due to the complexity of obtaining this phase pure.

The Experimental Research on Special Polymerized Sulfur Composite- Impregnated Concrete and Cement Mortar

Specific chemical environments step out in the industry objects. This paper presents experimental investigation results of the chemical resistance of special polymerized sulfur composite impregnated concrete and cement mortar. The special polymerized sulfur composite applied as the industrial waste material. The process of special polymerized sulfur composite as the industrial waste material production is a thermal treatment process in the temperature of about 150-155°C. The result of such treatment is special sulfur composite in a liquid state. Special sulfur composite in a liquid state is mixed with previously heated extender. In the paper there is presented development of the special polymerized sulfur composite as the industrial waste material, along with the practical uses in building industry. Also this paper presents the results of the experimental research and analyses indicating the usefulness of special polymerized sulfur composite to the protection against corrosion of concrete and cement mortar. In this paper the review of the literature have been done, among other things about select using special polymerized sulfur composite in buildings, about the methods of the surface protection against corrosion of concrete and about the methods of the evaluation of protection layer on these materials. Also in paper presents materials also the domain of the personal investigations and the methodology are definite. The research has comprised the compositions and the conditions for the formation of materials. The physical and mechanical properties of special polymerized sulfur composite have been evaluated. After the analysis of the initial results the optimum compositions have been chosen to the experimental research. In this paper the usefulness of special polymerized sulfur composite to the surface protection against corrosion of the concrete and cement mortar have been evaluated. Special polymerized sulfur composite impregnation of lean concrete and cement mortar increases its compressive strength from less than 1/3 to 1-1/2 times that of high strength concrete. Maximum absorption of special polymerized sulfur composite is achieved by carrying out the impregnation in molten sulfur under vacuum. Recent work indicates that satisfactory impregnation levels may also be achieved without the use of vacuum. Studies also show that while impregnation of high strength concrete and cement mortar increases its final strength to a value higher than that of low strength concrete, the relative increase in strength and the amount of special polymerized sulfur composite absorbed are smaller. Special polymerized sulfur composite impregnated concrete and cement mortar (SIC) may be used where high strength, resistance to water penetration, chemicals etc. are required. Available impregnating technology is applicable to precast concrete and cement mortar structures, while suitable technology for impregnating cast-in-place concrete needs to be developed. The impregnation of building materials such as blocks and bricks with melted special polymerized sulfur composite increases the compressive strength by a factor of 2 and modulus of elasticity by a factor of 3. The permeability of special polymerized sulfur composite impregnated materials to water and salt solutions is also greatly reduced. Due to the large surplus of sulphur and the low price, special polymerized sulfur composite impregnation of building materials will find extensive use in tall building construction. The space in concrete and cement mortar resulting from porosity reduces strength, exposes the concrete to chemical attack and, if filled with water, leads to destructive frost action at low temperatures. Filling the pores permanently and completely with an inert solid appears to be an effective way to improve mechanical properties and durability. Laboratory studies of impregnation with polymers have indicated that this is beneficial. New developments in concrete and cement mortar special sulfur polymer materials have declined in the Poland. There are still many products that are widely used, but the growth of these materials seems to have stabilized. A brief summary of new products related to special sulfur polymer composite impregnation, repair, overlays and precast polymer concrete will be presented. Sulfur polymer composite impregnation, which has received little attention in recent years, currently has some very interesting applications. Repair materials, particularly low modulus sulfur polymer concretes, have proven to be very effective. An innovative overlay for use in areas where freezing and thawing is prevalent has been developed.

Reservoir Simulation to Diagnose the Causes of Reduced Well Production Efficiency in Coal Bed Methane

This paper gives a detailed description of Coalbed Methane reservoirs and also few case studies have been presented highlighting the physical aspects of the reservoir. A generalized material balanced equation that accounts for and incorporates the Langmuir isotherm, initial free gas, water expansion and formation compaction. This particular form of material balancing can be used to estimate the original gas in place and unlike other methods does not require an iterative process to solve the equations. Also this report documents the practical application of the proposed material balanced equation. This report also shares case histories and best practices developed from designing and placing the cement successfully in Coalbed methane wells in India. These case histories include cement design considerations and special cement placement techniques. Reservoir models that incorporate the unique flow and storage characteristics of CBM reservoirs have been developed to study the production and decline characteristics of the reservoir. Further production facilities described include artificial lift, wellhead separation, gathering systems, compression, gas treating and water disposal. Finally we conclude the report by use of reservoir simulation to diagnose the causes of reduced well production efficiency.

Cnota jako kapitał społeczny

The present article, describing the concept of virtue and its place in the formation of a person’s maturity, points to the social dimension of moral competences that have their repercussions in interpersonal relations. Virtue is a social capital thanks to the fact that it triggers definite mechanisms in a man, enabling him to get involved in the realization of the common good. It becomes a special cement of human relations when it ensures proper conditions for forming existential bonds with others and it shapes a personal way of experiencing the challenges that one encounters and of responding to them. The four cardinal virtues: prudence, justice, courage and temperance make up a cohesive quartet of attitudes that determine one’s ability to control himself and the possibility to help others in a responsible way. The supreme manifestation of the social capital is love, owing to which a man is prepared to give his life in the service of his neighbor.

Preparation and characterization of super low density foamed concrete from Portland cement and admixtures

Foamed concrete with its super low density of between 150kg/m3 and 300kg/m3 was prepared by means of chemically foaming and so called mixing and foaming process in laboratory. Conventional Portland cement was selected as the main binding material instead of rapid hardening special cement such as sulfoaluminate cement. Chemical and physical admixtures were properly introduced for the regulation of the rheological property and hardening speed of the fresh cement mixture slurry as well as the physical properties of the hardened foamed concrete. The resultant foamed concrete with its curing age of 28d thus obtained presents its compressive strength between 0.33MPa and 1.1MPa, water absorption between 6.6% and 8.3% and thermal conductivity between 0.05W/mK and 0.07W/mK.

Production Quality Control of Moderate Heat Portland Cement and Analysis of Application Effect in Roller Compacted Concrete

Moderate Heat Portland Cement is not only frequently-used cement for dam but also one of the largest amount of special cement as a main cementitious materials of concrete in hydraulic structure in China. Due to the high quality requirement and the complicated technology in the construction of dam, a series of measures are adopted to control the production quality of Moderate Heat Portland Cement used in the dam construction. In this paper, the measures of production quality control of the Moderate Heat Portland Cement are introduced, including controlling the raw materials such as the cement raw meal, fuel, clinker and gypsum, managing the discharge from the mill and the entrance test, which ensure that the various targets of physical and mechanical indexes are in accordance with the standard requirement. Moreover, the engineering quality of Roller Compacted Concrete (RCC) for the dam is effectively guaranteed through the lower pot temperature and the less hydration heat. The construction experience is available for the like-kind engineering interiorly.