Cement Clinker Minerals Research Articles

Performance and mechanism of carbon sequestration of air-entraining wet shotcrete

CO2 curing concrete technology refers to the CO2 reacts with cement clinker minerals to obtain high-performance concrete and achieve the purpose of energy saving and emission reduction. The researches of air entrainment agent (AEA) focus on the development of new AEA and the study of concrete performance after adding some AEA. In the background of CO2 curing concrete technology, there are relatively few researches on the influence mechanism of different characteristics of bubbles introduced by different AEAs on carbon fixation performance of concrete. This paper demonstrates the characteristics of air bubbles introduced by SY-5 AEA (main component: triterpene saponin) and LAS AEA (main component: sodium dodecylbenzene sulfonate), compares the strength of concrete mixed with above two types of AEAs cured for 28 days and analyzed them by carbonization depth test, ultrasonic detection of fissure test, SEM, XRD and TG. Results show that different AEAs introduced different characteristics of air bubbles, which affected the internal pore characteristics of concrete, and then affected its mechanical properties and carbon sequestration properties. Compared with SY-5 AEA, LAS AEA had a slightly lower air-entraining effect. But the bubbles introduced were even and stable, the internal pores of the hardened concrete were uniform. Although the former had a high carbon sequestration, the latter had a higher intensity at 28 d, about 2.69 % higher. Under carbonization curing conditions, the improvement of concrete properties was more evident when appropriate AEAs were incorporated. The compressive strength and the splitting strength were increased by 5.57 % and 4.5 % respectively under the carbonization curing condition.

Impact of desulphurized electrolytic manganese residue-assisted cementitious materials on silicate cement hydration and environmental safety assessment

The use of electrolytic manganese residue (EMR) as a mineral admixture is an efficient way of utilization, but its high content of gypsum phase limits its utilization. In this paper, EMR was desulphurized by means of high temperature reduction roasting to remove the hindrance when utilized as a mineral admixture. The effect of desulphurized EMR (D-EMR) on the formation of major hydration products such as C–S–H and calcium hydroxide (CH), as well as on the degree of hydration of cement clinker, was explored based on mechanical properties, hydration kinetics, thermogravimetry-differential scanning calorimetry (TG-DTG) and Quantitative X-ray diffraction analysis (QXRD). In particular, the mineral phase evolution, the change rule of pore solution and the leaching behavior of heavy metals were simulated in conjunction with thermodynamics. The results show that the D-EMR content of 15 %, comparable mechanical properties and microscopic morphology to the control group can be obtained, while C3S and C2S hydration can be promoted by a factor of 1.08 and 1.28, respectively, without the risk of heavy metal leaching. Based on the thermodynamic simulation of heavy metal solidification by cement clinker minerals, it can be seen that heavy metals in D-EMR composite slurry are solidified mainly by Mn(OH)2 precipitation and weak adsorption effect, and it is safe even at the level of 30 % replacement, provided that the pH value of the leaching solution is greater than 7.5. In addition, the desulphurization technology is feasible from the perspective of environmental protection, and saves 200,000 CNY in emission costs.

Synergistic effect of recovering hardened cement powder and aluminum sulfate alkali-free liquid accelerator for enhancing the hydration and hardening of cement paste

The hardened cement powder (HCP) produced by the concrete waste disposal process can have a significant impact on the environment. How to effectively use HCP is the focus of current researchers. In this work, the synergistic effect of the treated hardened cement powder (T-HCP) and accelerator (ASS) was studied. The synergistic mechanism was studied by apparent porosity, hydration heat, XRD and SEM. Results demonstrated that the T-HCP can be used together with aluminum sulfate alkali-free liquid accelerator to improve the strength of cement. The main reason is T-HCP contains cement clinker mineral phase and fine CaCO3 crystals, in which the clinker mineral phase can be rehydrated, and the fine CaCO3 crystals can be used as nucleation sites to accelerate the generation of hydration products. Besides, adding T-HCP can improve the performance of cement mortar and save cost considering the economic aspects.

Thermodynamic Simulation of Environmental and Population Protection by Utilization of Technogenic Tailings of Enrichment.

During mining, only 4–8% is converted to final products, and the rest is accumulated in landfills. There is a lack of research on the study of various patterns and mechanisms of the formation of cement clinker minerals during the simultaneous distillation of zinc. This paper presents studies of thermodynamic stimulation of environmental and population protection by utilization of technogenic enrichment waste as secondary raw materials for clinker production and zinc extraction. In particular, a comparison of the Gibbs energy (ΔG) of clinker formation under standard chemical equations and under non-standard chemical equations is given. According to the results of the study, using thermodynamic simulation, the temperature intervals of mineral formation, the dependence of the Gibbs energy on temperature (ΔGT°), and the approximation equations were found; it was established that the presence of zinc ferrite contributes to the intensification of the formation of clinker minerals and the extraction of Zn to gas.

Use of ilmenite ore enrichment wastes in the production of Portland cement clinker

We presented the results of the research on the influence of d-elements of ilmenite ore beneficiation wastes of the Vilnohirsk Mining and Metallurgical Plant on the structure and properties of Portland cement clinker minerals, firing properties and their hydraulic activity. It was established that the use of the enrichment wastes as an aluminosilicate component of the raw material mixture for clinker firing contributes to the reduction of the consumption of blast furnace granulated slag, simultaneously increasing the consumption of limestone. The presence of compounds of d-elements contained in the wastes of enrichment of ilmenite ore in the proposed raw material mixture for obtaining Portland cement clinker increases the saturation coefficient up to 99% and improves the processes of decarbonization and sintering during clinker firing. The physical-mechanical characteristics of the developed cements, in particular the compressive strength limit indicators, are not inferior to those produced according to the classical formulation. Cements obtained on the basis of clinkers, according to their properties, correspond to type II cements (state standard DSTU B.V. 2.7-46:2010). Partial replacement of the clay component in the raw material mixture by ilmenite ore enrichment wastes allows significantly expanding the raw material base for the production of Portland cement clinker and effectively influencing the technological process of firing.

Time-dependent retardation effect of epoxy latexes on cement hydration: Experiments and multi-component hydration model

The kinetics and thermodynamics of the retardation effect of epoxy latexes on cement hydration were investigated using isothermal calorimetry and in-situ x-ray diffraction. The experimental results showed that the retardation effect of epoxy latexes on cement hydration was time-dependent. When the epoxy latexes were added to cement pastes, heat-generation rate was slowed, the hydration induction and acceleration periods were delayed, and the heat-flow maxima were suppressed. The addition of epoxy latexes markedly retarded silicate and aluminate hydrations by retarding both the dissolution of cement clinker minerals and the precipitation of hydration products. Higher epoxy latex content led to even slower cement hydration. Based on these results, a multi-component hydration model for composite cementitious materials, considering the time-dependent retardation effect of epoxy latexes on cement hydration, was established. The numerical results showed that the model showed great potential to predict the kinetics and thermodynamics of cement hydration with different epoxy latex contents, and provided more details about the phase evolution of the clinker minerals during cement hydration.

Research on mechanical performances of composite cementitious material system in new bridge expansion joint UHPC material

In the bridge expansion joint repair project, in order to ensure the efficiency of the project, the repair material needs to have better flow properties and higher early strength. The introduction of sulphoaluminate cement will significantly change the properties of UHPC. Compared with ordinary Portland cement, the composition of its cement clinker mineral belongs to another physical and chemical system, which has excellent properties such as early strength, high strength, impermeability and corrosion resistance. Therefore, different groups of UHPC were prepared by changing the content of sulphoaluminate cement, and the fluidity test of each group of slurry and the compressive strength and flexural strength test of 1d, 3d, 7d, 28d were carried out to study the sulfur. The influence of aluminate cement content on slurry fluidity and early mechanical properties in order to obtain the optimal mix ratio of UHPC materials for new bridge expansion joints.

Thermodynamic modeling of the synthesis of the main minerals of cement clinker from technogenic raw materials

In this article, thermodynamic studies of modeling the formation of the main minerals of cement clinker as a function of the Gibbs energy (ΔG) on temperature were investigated. The temperature range of the studies was 873-1873 K. In the course of modeling studies, the reactions of formation of cement clinker minerals (C2S - belite, C3S - alite, C3A – three calcium aluminates, C4AF – four calcium aluminium ferrite) from standard raw materials and non – standard-technogenic raw materials containing non-ferrous metals were calculated. Equations describing the dependence of the Gibbs energy on temperature with approximation coefficients (R2) equal to 0.99 are found. According to the results of the conducted studies, the beginning (Tb) temperatures of the course of the compared clinker formation reactions were determined, which were 1008 K for the standard reaction, and 1023 K for the non-standard reaction. It was found that the reactions begin to occur in the temperature intervals for the standard (1008 K – 1873 K), for the non - standard (1023 K - 1873 K). At the same time, the values at the initial stage of the course of the standard reaction have a more negative value of the Gibbs energy than the non-standard reaction. With a further increase in temperature, it becomes evident that the Gibbs energy of the non-standard reaction of mineral formation in the temperature range 1173-1873K becomes more negative in comparison with the values of the standard reaction and exceeds its values from 9 to 19.01%.

Influence of Uranium on the Hydration Properties of the Cement Clinker Minerals

The influence of uranium simulated waste water on the hydration properties of the cement was studied by modern test methods such as TAM air, XRD, FTIR, and SEM-EDS. The results show that uranium can promote the hydration of mineral C3S, and inhibit the hydration of mineral C3A. By comparing scanning of hydration products, it was found that the existence of uranium significantly changed the morphology of clinker hydration products , but uranium had little effect on the type of clinker hydration product.

Effect of Aluminum Sulfate on the Hydration of Tricalcium Aluminate

Aluminum sulfate (AS), as the main composition of alkali-free accelerator, was widely used to accelerate the setting and promote the early strength in the sprayed concrete. In this study, effect of AS on the hydration reaction of C3A was investigated, which is one of the most important cement clinker minerals in the early age of cement hydration. The hydration reaction and products of C3A-AS system were characterized with hydration heat test, X-ray diffraction, thermogravimetric analysis, scanning electron microscope, and thermodynamic modeling. Results indicate that AS could hinder the hydration reaction in the very early age but then accelerate C3A hydration by producing SO4-AFm, OH-AFm, and gibbsite. The findings are expected to provide theoretical guidance for the product research and engineering application of alkali-free accelerator.

Portland cement foam concrete with a zeolite-containing mineral additive

The possibility of obtaining high-quality cement by an environmentally friendly (without CO2 emission into the atmosphere) method of joint grinding of imported Portland cement clinker and local natural mineral raw materials in hard-to-reach areas of the North-East of the Russian Federation is substantiated. The results of an experimental study of the compositions and technological parameters of the manufacture of cement compositions based on portland cement clinker and active mineral additives from zeolite-containing rocks of Khonguruu, allowing non-autoclaved foam concrete with a density of 600-800 kg / m3 and compressive strength of 1,8-2,8 MPa with stable quality parameters are presented (monodisperse pore distribution and hardened inter-pore skeleton, providing stable values of density, strength and thermal conductivity).

Construction and technical properties of PC 500 D0 CEMENT

It is established that physical and mechanical properties of Portland cement, including setting time and strength, correspond to mark PC 500 D0 and meet technical requirements of the corresponding standard. However, they have increased dispersion ability and water consumption. It has been determined that the main Portland cement clinker minerals (C3S, β-C2S, C3A and C4AF) in cement are represented as solid solutions as a result of the presence of impurities in their structure.

Estimation of standard molar entropy of cement hydrates and clinker minerals

It is not straightforward to experimentally measure the standard molar entropy of cement hydrates or clinker minerals. This is further compounded by the controversies surrounding the entropy values reported in established thermodynamic datasets for cements. The purpose of this study is to assess the reliability of standard entropies compiled in those datasets. To this end, a simple but robust method is used in which the standard entropy of an inorganic solid is correlated to its formula unit volume via a linear equation. The results of this analysis show that the standard entropies and/or molar volumes (and in cases solubility products) of the following phases deserve closer scrutiny: meta-ettringite phases; magnesium/aluminium layered double hydroxide solid solutions; almost all iron-bearing monosulfate and hydrogarnet phases; and several calcium silicate hydrate solid solution end-members. In addition, this study reports the provisional estimates for the standard entropies of minerals ternesite and ye'elimite.

Effect of Cr on the Mineral Structure and Composition of Cement Clinker and Its Solidification Behavior.

In order to reveal the solidification behavior of Cr in the cement clinker mineral phase, 29Si magic-angle spinning nuclear magnetic resonance, X-ray diffraction, and scanning electron microscopy with energy-dispersive X-ray spectroscopy techniques were used to analyze the morphology and composition of the cement clinker mineral phase doped with Cr. The results showed that the addition of Cr did not change the chemical environment of 29Si in the clinker mineral phase, and it was still an isolated silicon–oxygen tetrahedron. Cr affected the orientation of the silicon–oxygen tetrahedron and the coordination number of calcium, leading to the formation of defects in the crystal structure of the clinker mineral phase, by replacing Ca2+ into the mineral phase lattice to form a new mineral phase Ca3Cr2(SiO4)3. Cr acted as a stabilizer for the formation of β-C2S in the clinker calcination. As the amount of Cr increased, the relative content of C3S decreased and the relative content of C2S increased. Further, Cr easily dissolved in C2S, while it was not found in C3S. This study is conducive to further research on the mechanism of heavy metal solidification in cement clinker. Furthermore, it is important to evaluate the environmental risk of heavy metals in the process of sludge disposal through cement kiln and promote the utilization of sludge resources and the sustainable development of the cement industry.

Effectiveness of Nanotubular Additives in the Modification of Cement Systems

Tubular chrysotile and carbon nanoparticles have been shown to effectively influence the hydration and hardening kinetics, structure formation, and strength of cement systems. Similar in crystal-chemical structure to newly formed hydrated phases, chrysotile nanotubes are the most effective modifier, ensuring a factor of 30 increase in the rate of hydration and hardening processes and a factor of 3 increase in the strength of cement stone. Chemically inert with cement clinker minerals and clinker hydration products, carbon nanotubes ensure a factor of 9 increase in the rate of hydration and hardening processes and a factor of 1.5 increase in strength.

PORTLAND CEMENT WITH NATURAL MINERAL ADDITIVES

One of the most effective developments of energy saving in the production of Portland cement used worldwide, is joint grinding of Portland cement clinker with injected mineral additives, such as pozzolanic rocks, ashes and slags.The aim of this work is to substantiate the possibility of the quality cement production using joint grinding of Portland cement clinker with natural mineral additives with a view to the of production location.River (quartz-feldspar) sands of the Lena basin and large-tonnage raw materials (zeolitecontaining rocks of the Khonguruu deposit) are considered as mineral additives to Portland cement. The study uses both standard test methods and the X-ray phase analysis for binders and concretes.The activity of the mineral additives to Portland cement is studied. The main properties of clinker, gypsum stone and mineral additives are studied to organize the production of quality Portland cement and products for the support of construction projects in the North-Eastern part of the Arctic and the North of Russia. The effect from additives and fineness of zeolitecontaining clinker and quartz-feldspar sand is studied relative to the thickness and setting time of the cement paste and cement mortar strength.It is shown that the types CEM II/A-P 32.5N and CEM II / A-P 42.5N Portland cement can be produced from imported Portland cement clinker and local mineral additives saving 5–15 % Portland cement clinker.

Structure of road soil cement compositions modified by complex additive based on organosilicon compounds and electrolytes

The complex introduction of organosilicon compound (octyltriethoxysilane) and electrolyte (sodium hydroxide) maximizes the frost resistance and strength of soil cement. However, the effect of complex additive based on octyltriethoxysilane and sodium hydroxide on the soil cement structure has not been sufficiently studied. Therefore, the aim of this work was to study the phase composition of hydrated newgrowths and soil minerals in soil cement with optimal content of complex additives. The study was conducted by methods of complex thermal analysis, X-ray powder diffraction and electron microscopy. On the XRD pattern of the sample with and without complex additive, we marked identical peaks of soil minerals, unhydrated cement clinker minerals and hydrated newgrowths. In the result of differential thermal analysis, we determined that soil cement with complex additive is characterized by the smaller amount of free calcium hydroxide formed, as well as saturation of the soil complex with sodium ions. In the soil cement sample with complex additive, we observe a smaller amount of coagulated soil aggregates in comparison with the sample without an additive. Complex additive contributes to the formation of a more dense and uniform structure of soil cement, reduces the amount of adsorption water associated with clay minerals, reduces the formation of free calcium hydroxide, which increases the physicomechanical properties of the resulting material.

Effects of quartz on crystallization behavior of mold fluxes and microstructural characteristics of flux film.

Mold fluxes are mainly prepared using cement clinker, quartz, wollastonite, borax, fluorite, soda ash and other mineral materials. Quartz, as one of the most common and essential materials, was chosen for this study to analyze itseffects on crystallization temperature, critical cooling rate, crystal incubation time, crystallization ratio and phases of flux film. We used the research methods of process mineralogy with the application of the single hot thermocouple technique, heat flux simulator, polarizing microscope, X-ray diffraction, etc. Results: By increasing the quartz content from 16 mass% to 24 mass%, the crystallization temperature, critical cooling rate and crystallization ratio of flux film decreased, and the crystal incubation time was extended. Meanwhile, the mineralogical structure of the flux film changed, with a large amount of wollastonite precipitation and a significant decrease in the cuspidine content until it reached zero. This showed a steady decline in the heat transfer control capacity of the flux film. The reason for the results above is that, by increasing the quartz content, the silicon-oxygen tetrahedron network structure promoted a rise in viscosity and restrained ion migration, inhibiting crystal nucleation and growth, leading to the weakening of the crystallization and a decline in the crystallization ratio.

Physico-mechanical studies of the advantages belite of portland cement for concrete, necessary for modern surface and underground military installations

In connection with the development of powerful weapons, especially those that are developed on new physical principles, the acute problem of reliable protection and ensure the survivability of personnel. The development of the new fortifications that can provide protection from various weapons, identify new methods for their construction on a tight time budget are the main objectives of the fortification at the present stage. Concrete structure building can be a long time to maintain its performance, however, under the influence of aggressive environmental factors, they gradually change their physico-chemical and structural-phase properties. Military facilities, including aboveground and underground structures, require not only durability and reliability but also the preservation of these properties with time.For the production of mortars and concretes that can be used for the construction of military fortifications, we propose belite Portland cement, which according to preliminary data has significant water resistance and frost resistance, low exothermy, high corrosion resistance, increasing with age of strength.The purpose of this article is to compare physical and mechanical properties alite and belite of Portland cement, determining the influence of the content of clinker minerals on tensile strength at different stages of hardening. The role of the early stages of hardening of cement the properties of concrete for various purposes is large, because with the greatest speed and intensity are the main hydration reactions of clinker minerals, the structure of cement stone.Studied the physico-mechanical properties of four types of cement and major clinker minerals С3S and С2S: alite №1 (С3S – 60.82% С2S – 14.73%); normal №2 (С3S – 40.06%, С2S – 32.58%); belite №3 (С3S – 24.59%, С2S – 48.25%) and belite №4 (С3S – 9.2%, С2S – 63.18%). It is established that the strength of cement in the first period of hardening is determined by the content С3S, which is the clinker mineral that quickly hardens. It is revealed that the influence of the mineralogical composition of Portland cement on strength is decisive to a six-month period of hardening. After six months to a year and tensile strength is does not change, and within 10 years, the cements having a high content С2S continue to gain strength, whereas for cements with a high content of С3S – losing her.Therefore, the use of belite cement for their construction is promising, however, requires detailed studies on the frost resistance, sulfate resistance and water resistance.

Effects of quartz on crystallization behavior of mold fluxes and microstructural characteristics of flux film.

Mold fluxes are mainly prepared using cement clinker, quartz, wollastonite, borax, fluorite, soda ash and other mineral materials. Quartz, as one of the most common and essential materials, was chosen for this study to analyze itseffects on crystallization temperature, critical cooling rate, crystal incubation time, crystallization ratio and phases of flux film. We used the research methods of process mineralogy with the application of the single hot thermocouple technique, heat flux simulator, polarizing microscope, X-ray diffraction, etc. By increasing the quartz content from 16 mass% to 24 mass%, the crystallization temperature, critical cooling rate and crystallization ratio of flux film decreased, and the crystal incubation time was extended. Meanwhile, the mineralogical structure of the flux film changed, with a large amount of wollastonite precipitation and a significant decrease in the cuspidine content until it reached zero. This showed a steady decline in the heat transfer control capacity of the flux film. The reason for the results above is that, by increasing the quartz content, the silicon-oxygen tetrahedron network structure promoted a rise in viscosity and restrained ion migration, inhibiting crystal nucleation and growth, leading to the weakening of the crystallization and a decline in the crystallization ratio.