Magnesia Cement Research Articles

Development of a technology for absorbing screening of command posts with electronic equipment

The problem of creation of a technology for effective protection of rooms of control points with electronic equipment against powerful intentional and industrial interferences was studied. Development of ray weapons is a new challenge to electronic equipment safety by the use of modern powerful electromagnetic weaponry. Absence of theoretical recommendations in the conditions of growing practical needs causes the relevance of this problem solution. As a result of theoretical and experimental studies, rational ways for solution of the problem related to the necessity of absorption of the field energy in a wide frequency range at the level of 40...50 dB were substantiated while the level of absorption known from publications is 10...20 dB. The basis for solving this problem is a significant improvement of the technology for preparation of a filler with necessary electromagnetic properties. This is an electrically conductive ferrite-ferrite compound with a structure of spinel of inverse type which has the commensurate levels of relative dielectric and magnetic permeability and electrical conductivity of (103...104) S/m. These properties of the filler will contribute to the satisfaction of generally contradictory requirements. Such are the requirements for reducing the field energy reflection from the surface of the radiation absorbing coating of the room and the requirements for increasing linear energy absorption by coating (12...15 dB/mm). Therefore, the proposed 4 mm thick absorbing Sorel cement tiles with the proposed filler provide absorption of field energy in a wide frequency band at a level of 40...50 dB due to their polymerization filling. The choice of the aforementioned binder base for the filler is justified because significant levels of thermal stability of the base are required. In principle, it is also necessary to improve the technology of highly concentrated filling of the solid, heat-resistant polymer base for the radiation absorbing coating, which effectively protects hardware of the command post from contemporary ray weapons. Existing organic polymer bases for the required coating have a limited ecological purity and working temperature not exceeding 250...300 o C. Therefore, it is expedient to use an environmentally friendly inorganic polymer in a form of Sorel cement with significantly higher thermal stability. That is why the technology of screening rooms by covering their inner surface with absorbing Sorel cement tiles was proposed. Once the filler is prepared, pre-filling of the aqueous solution of cement ingredients with dispersed filler as a field energy converter is made. After solidification of the Sorel cement tiles and covering the surface of the room, energy of interfering electromagnetic fields falling on the coating converts into heat energy. The necessary hardware screening at a level of 40...50 dB is provided by the following technology stages. First, thermochemical synthesis of conductive ferrite oxide of transition metals with a structure of spinel of inverse type is carried out at a temperature above 600 o C. Secondly, vibrational polymerization concentrated filling of the base mixture of the magnesium oxide and saturated aqueous solution of magnesium chloride is realized without the loss of strength of the tiles after their solidification. The tiles are solidified at room temperature for 15 to 17 hours

Prediction of steel corrosion in magnesium cement concretebased on two dimensional Copula function

In order to solve the life prediction problem of damaged coating steel bar in magnesium cement concrete, this study tries to establish the marginal distribution function by using the corrosion current density as a single degradation factor. Representing the degree of steel corrosion, the corrosion current density were tested in electrochemical workstation. Then based on the Copula function, the joint distribution function of the damaged coating was established. Therefore, it is indicated that the corrosion current density of the bare steel and coated steel bar can be used as the boundary element to establish the marginal distribution function. By using the Frank-Copula function of Copula Archimedean function family, the joint distribution function of the damaged coating steel bar was successfully established. Finally, the life of the damaged coating steel bar has been lost in 7320d. As a new method for the corrosion of steel bar under the multi-dimensional factors, the two-dimensional Copula function has certain practical significance by putting forward some new ideas.

Preparation of Magnesium Phosphate Cement and Application in Concrete Repair

Potassium magnesium phosphate cement (MKPC) was prepared by using magnesium oxide (MgO) and potassium dihydrogen phosphate (KH2PO4, KDP). The effects of different calcination temperature, water-cement ratio and ratio on the operation of magnesium phosphate cement were studied. The effects of different water - cement ratio and ratio on the bonding strength of potassium magnesium phosphate cement and the application of potassium phosphate and magnesium cement in concrete repair and reinforcement were determined by experiments such as bending resistance, splitting, compression and bearing capacity. The experimental results show that the calcination temperature is 1100 °C, the calcination time is 1h, the settling time of magnesium oxide is 39min, and the compressive strength of one day reaches 53MPa. The water - cement ratio with the best bonding strength is 0.2, the mass ratio is 2:1.To meet the rapid repair of the construction requirements, is expected to be applied to the actual repair works.

Preparation of Magnesium Phosphate Cement and Application in Concrete Repair

Potassium magnesium phosphate cement (MKPC) was prepared by using magnesium oxide (MgO) and potassium dihydrogen phosphate (KH2PO4, KDP). The effects of different calcination temperature, water-cement ratio and ratio on the operation of magnesium phosphate cement were studied. The effects of different water - cement ratio and ratio on the bonding strength of potassium magnesium phosphate cement and the application of potassium phosphate and magnesium cement in concrete repair and reinforcement were determined by experiments such as bending resistance, splitting, compression and bearing capacity. The experimental results show that the calcination temperature is 1100 °C, the calcination time is 1h, the settling time of magnesium oxide is 39min, and the compressive strength of one day reaches 53MPa. The water - cement ratio with the best bonding strength is 0.2, the mass ratio is 2:1.To meet the rapid repair of the construction requirements, is expected to be applied to the actual repair works.

Investigation of magnesium oxychloride cement at the initial hardening stage

The paper investigates the process of variation of magnesium oxychloride cement deformations at the initial hardening stage depending on the activity of magnesium oxide powder which is determined by the parameters of the source material burning. Investigation is focused on magnesium cements obtained from pure magnesium hydroxide. Source materials were burnt at various temperatures with the purpose to obtain magnesium oxide powder with different activity. Regular content of hydrated phases was determined in hardened magnesium cement prepared on the basis of binders with different activity. The study reveals the influence of magnesium oxide powder activity on the process of deformation occurrence in hardened magnesium cement and its tendency to crack formation.

Adsorption Studies on Reactive Black 5 by Varying the Composition of Sorel Cement

Adsorption Studies on Reactive Black 5 by Varying the Composition of Sorel Cement

镁质水泥轻质海水混凝土力学性能研究

镁质水泥轻质海水混凝土力学性能研究

CONTRIBUTION TO THE KNOWLEDGE OF THE MAGNESITE DEPOSITS IN BOSNIA AND HERZEGOVINA

Magnesite is an industrial mineral of magnesium, which most often occurs in the form of crystalline, massive and amorphous forms. Mineral magnesite has a wide and varied application in the production of high-strength materials: powder (flour), sinter, bricks (magnesite, magnesite-chromite, forsteric, etc.). In the construction industry it is used for the production of magnesium cement. In smaller quantities it is used in chemical, pharmaceutical, rubber and other industrial branches. The area of the so-called "Bosnian Serpentine Zone" are stand out in the area of the inner Dinarides of Bosnia and Herzegovina, among numerous phenomena and larger deposits of magnesite. In terms of quality, the variability from high quality to those that can not be used in the refractory industry is determined. Magnesite deposits mostly require certain preparation procedures in order to achieve higher quality magnesite. The paper presents deposits and the appearance of magnesite in Bosnia and Herzegovina, with emphasis on the results of previous research, quality, reserves, usability and laboratory testing, and the results of the latest X - ray examinations from one site have been presented.

BINDING MATERIALS ACTIVITY REGULATING BY MECHANICAL CHEMICAL METHODS

It has been established that some abrading treatment of metals oxides crystallizing by halite crystal type (CaO, MgO) reduces their reactive capability. The activity reduction rate was substantially higher than that which could be explained by reducing of oxide specific surface. So, it is reduced for MgO by 30-40 %, while the oxide activity in the magnesium cement – by 250-1000 % (contrary to an impact treatment in a vibration mill). Similar results have been obtained for the interaction between calcium oxide and water, solutions of orthophosphoric acid and salts. CaO powder specific surface before and after abrading treatment by BET method reduces by 50-60 %, while variations of rate constant ranged from 1.5 to 34 times. The same mechanical treatment has a little effect on similar processes in systems where beryllium and zinc oxides are present (structure type of wurtzite). The reactive capability reduction for calcium, magnesium and cadmium oxides can be connected with some changes in the form of polycrystallites' particles in the abrading treatment process. The more prolonged abrading leads to plane sliding and some exposing flat surfaces those are characteristic for crystals of cubic syngony. Thus, an irregular defect layer is removed from grains. Small particles separated in the course of a mechanical treatment from rounded grains at the first stage (up to 5 min) show an increased activity, and then quite dense low active aggregates are formed. The more ordered zones, exposed in the course of an abrading, react slower in comparison to the initial grains, as well as to thin particles being split out. Due to this process the chemical activity reduces. On the contrary, zinc and beryllium oxides crystallites in the abrading treatment practically do not change their outline character; their chemical activity remains constant. Thus, the mechanical abrading treatment of oxides, which crystallize by halite type, really allows reducing their reactive capability in quite wide limits. This opens new opportunities in chemistry of binding materials, allowing achieving needed proportion between rates of chemical interaction and structure-forming in binding systems, which is a necessary condition for a solid monolith compositions' formation.Forcitation:Kosenko N.F., Filatova N.V. Binding materials activity regulating by mechanical chemical methods. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 1. P. 66-71

Investigation of Interrelation between Deformation, Composition and Structural Characteristics of Magnesium Oxychloride Cements

The paper studies the process of volume deformation changes in magnesium cement at its hardening in accordance with its composition and structural peculiarities, which result from the roasting parameters of the raw materials. The study has been carried out with the aim of broadening raw materials sources for production of magnesia cements and construction materials through the use waste products of ore-dressing and processing enterprises. The mineralogical and phase composition of magnesium cements, obtained on the basis of magnesite with high content of impurity minerals from the mine dumps, has been studied by the X-ray phase analysis and derivatography. The roasting of the initial raw materials was carried out at various temperature conditions in order to get cements of different activities. The typical content of hydrated phases has been found for the hardened magnesian stone obtained from cements with different activity degrees. The characteristics of volume deformations developed in the magnesian stone have been described in relation to its phase composition. The influence of low- and high-activity crystals and calcium oxide crystals on the soundness and the structural integrity of magnesian stone has been covered.

Development of MgO concrete with enhanced hydration and carbonation mechanisms

This study proposed the use of hydration agent (HA) and seeds to improve the hydration and carbonation of reactive magnesium cement (RMC)-based concrete formulations. Hydration of RMC was evaluated by isothermal calorimetry. Water absorption and compressive strength results were used to assess the mechanical performance of RMC-based concrete samples. Quantification of hydrate and carbonate phases was performed via XRD and TGA. Formation and morphology of carbonates were observed via BSE and SEM. In addition to increasing the utilization of RMC in the carbonation reaction and facilitating early strength development, the use of HA formed large carbonate phases, while the addition of seeds improved sample microstructures via the development of dense carbonate networks. The improvements in morphology, microstructure and carbonate content in samples involving the simultaneous use of HA and seeds resulted in 56% lower water absorption values and 46% higher 28-day compressive strengths (70MPa) in comparison to the control sample.

Impact of a Ni2+-influx on formation, stability, solubility and crystal structures of the magnesia cement phases 3-1-8 and 5-1-8 at 25 °C

The impact of a Ni2+-influx on formation, stability, solubility and crystal structures of the 3-1-8 (3 Mg(OH)2·MgCl2·8H2O) and the 5-1-8(5 Mg(OH)2·MgCl2·8H2O) binder phases of the magnesia cement system was studied by adding MgO, the 5-1-8 and the 3-1-8 phase to Ni2+-bearing 4.0 molal MgCl2-solutions at 25°C and applying equilibration periods of more than 2 years (up to 800days). Nickel was observed to enter the crystal structure of the 5-1-8 phase, yielding solid solutions among this magnesium chloride hydroxide hydrate and its Ni-analog, whereas no incorporation of Ni2+ ions into the crystal structure of the 3-1-8 phase takes place. The presence of nickel in the access solution inhibits the transformation of the metastable 5-1-8 phase into the thermodynamically stable 3-1-8 phase and prolongs the duration of this process from a few days to more than 2 years. As the final product of the phase formation process a mixture of the 3-1-8 phase and the 2-1-4 Ni-phase (2 Ni(OH)2·NiCl2·4H2O) could be identified. Analyses of the resulting liquid phases confirmed that almost the complete amount of dissolved nickel was removed from the solution by the addition of MgO, the 5-1-8 or the 3-1-8 phase.

Recycling contaminated sediment into eco-friendly paving blocks by a combination of binary cement and carbon dioxide curing

Dredging is a regular maintenance for navigation in harbours and water channels; however, disposal of dredged sediment poses environmental liability and leads to shortfall of disposal facilities. This study demonstrated an innovative approach to transform contaminated sediment into eco-friendly sediment blocks by applying binary cement and CO2 curing. The binary use of magnesium oxide cement (MOC) and ordinary Portland cement (OPC) with air curing improved the compatibility of heavy metals and cement by provision of sufficient magnesium hydrates for metal sequestration. However, an introduction of MOC weakened compressive strength and increased water absorption of sediment blocks. Therefore, 1-d CO2 curing was employed to transform soluble magnesium hydrate into stable carbonates, and densify the microstructure and reduce the porosity from 18.5% to 16.9%, which enabled a substantial enhancement in strength (2.8 times) as well as carbon sequestration (3.98 wt%) in 40% MOC sample. A subsequent 7-d air curing with moisturizing facilitated continuous carbonation and rehydration of binary cement, resulting in a deeper carbonation and higher strength by the provision of additional nucleation sites of reactive magnesium oxide. Although accelerated carbonation had an adverse influence on metal immobilization in OPC sample due to pH decrease, it provided synergistic interaction with binary cement samples due to sufficient hydrates and pH buffering capacity. Therefore, binary cement with CO2 curing presents a novel and green stabilization/solidification technology for recycling contaminated sediment as valuable and eco-friendly construction materials.

Electrochemical Study of ZINTEK Coated Steel Bars in Magnesium Cement Concrete

Electrochemical Study of ZINTEK Coated Steel Bars in Magnesium Cement Concrete

Influence of supplementary cementitious materials on the performance and environmental impacts of reactive magnesia cement concrete

This paper investigated the performance and environmental impacts of reactive magnesia cement (RMC)-based formulations containing pulverized fuel ash (PFA) and ground granulated blast furnace slag (GGBS). Concrete samples, whose binder component was composed of RMC with 0–50% PFA and GGBS replacement were subjected to carbonation curing for up to 28 days. The performance of each sample was analyzed and compared to corresponding Portland cement (PC)-based samples via porosity, water sorptivity, compressive strength and thermal conductivity measurements. The performance results were supported with the assessment of the environmental impact of each sample throughout their production and utilization phases. Samples in which 50% of the binder component was replaced by PFA indicated the highest strength development, reaching strengths as high as 60 MPa at 28 days, which were 33% higher than those of the corresponding RMC control sample. The advantageous strength gain demonstrated by RMC-PFA samples was associated with a reduction in sample porosity due to the filler effect of PFA as well as the formation of strength providing phases through the hydration and carbonation reactions. The use of both PFA and GGBS decreased the environmental impacts of RMC formulations, which was reflected as lower CO2 emissions, as well as reduced damage on human health and eco-system quality when compared to RMC and PC samples. The environmental efficiency calculations involving a combination of the net CO2 emissions and mechanical performance of each sample revealed the benefits of supplementary cementitious materials within RMC formulations.

Hypervelocity impact testing of materials for additive construction: Applications on Earth, the Moon, and Mars

The National Aeronautics and Space Administration’s Additive Construction with Mobile Emplacement project is investigating the building of infrastructure elements on planetary surfaces by 3-dimensional printing with construction materials made of in-situ resources. Likewise, the United States Army Corps of Engineers’ Additive Construction of Expeditionary Structures project seeks to 3-dimensionally print structures made of concrete available everywhere on Earth. These construction materials must resist failure due to micrometeorite impact and ballistic impact, respectively. Samples were tested for resistance to hypervelocity impact with a 2.0mm aluminum sphere at a velocity of 7.00±0.2km/s. Ordinary Portland Cement-bearing samples were not perforated and did not spall, including the sample that was additively constructed. This indicates printed construction material can withstand impact. The Sorel cement sample was not perforated, but fractured and spalled. Thus, Sorel cement in its current formulation would not be considered a feasible construction material for planetary structures.

Characteristic Features of Magnesia Binding Powder Production from Satka deposit Carbonate Rocks

The processes accompanying the firing of magnesites, dolomitized magnesites, and dolomites of the Satka deposit have been studied. The correlation between the size of periclase crystallites in the firing products and the physicochemical characteristics of magnesium cement powders has been found. The degree of the negative influence of free calcium oxide on the characteristics of magnesium cement powders has been determined. It has been found that the calcium oxide in any amount leads to crack formation and reduced durability. It has been shown that firing without any additives leads to the production of poor quality powders. The ways to improve the quality of the manufactured products have been suggested.

应急抢修用海工磷酸盐胶凝材料试验研究

根据海洋环境下抢修抢建的特殊性，利用海水与海砂制备海工磷酸镁水泥砂浆。通过测试其各龄期抗压强度，获得满足抢修抢建基本性能要求的最佳配合比，在此基础上，对海工磷酸镁混凝土、钢纤维增强海工磷酸镁水泥胶砂、海工磷酸镁水泥胶砂在海洋中的水上及水下两种不同环境的长期强度性能进行了初步研究。结果表明，三种海工磷酸盐水泥基材料在水上和水下的早期强度均能满足海洋环境下抢修抢建需要，但长期的强度变化规律不明显，需要进一步研究拌合海水对材料水化硬化作用以及侵蚀作用的影响。 According to the particularity of emergency repair and build under marine environment, marine engineering Magnesium-phosphate Cements were made with seawater and sea sand; the best mixture ratio was obtained which meets the requirement of emergency repair and build by testing compressive strength of each age. Based on previous research results, the primary research of long-term strength performance about Marine phosphate magnesium concrete, steel-fiber rein-forced Marine phosphate cement and Marine phosphate magnesium cement were performed in this paper. The research results show that early strength of all three kinds of Marine-phosphate cement overwater and underwater can meet the needs of the Marine environment emergency repair, but the long-term intensity variation regularity is not obvious. Further research about hydration and erosion influence of mix seawater should be performed.

Waterproof Magnesia Binder for Composite Materials

The paper presents a study of structure formation during the hardening of a new water resistant hydraulic magnesium cement. Improvement of water resistance and the manifestation of hydraulic properties in magnesium cement are associated with the use of a fundamentally new mixing liquid involving a magnesium bicarbonate solution. Use of this solution makes possible for the magnesium composition to harden not only in air, but also in water. The Coefficient of resistance is 1.0–1.8. When mixing the magnesium cement with an aqueous solution of magnesium bicarbonate, the main products of hardening are magnesium hydroxide and magnesium hydrocarbonates. The increase of the hydrocarbon phase contributes to the strengthening characteristics of magnesia compositions. Magnesium hydrocarbonates are insoluble in water, which provides the increased water resistance of magnesia compositions and the opportunity to harden and gain strength in water.

Recycling contaminated wood into eco-friendly particleboard using green cement and carbon dioxide curing

Landfill disposal of contaminated wood formwork from construction sites presents significant environmental burdens and economic wastage. This study proposed an innovative and low-carbon technology by using magnesia cement and CO2 curing to transform contaminated wood waste into eco-friendly cement-bonded particleboards, which demonstrated excellent compatibility and value-added properties. The microstructure characteristics and cement hydration chemistry were revealed by mercury intrusion porosimetry and X-ray diffraction analyses. At the optimal water to cement ratio of 0.3, the particleboards contained the lowest total pore area (10.2 m2 g−1) and porosity (26.1%), thereby successfully complying with the International Standards of mechanical strength (>9 MPa) and dimensional stability (<2% swelling after 24-h water immersion). An integration of 2-h CO2 curing facilitated carbonation at early stage and reduced the volume of mesopores and air pores, which contributed to strength development and carbon sequestration in the particleboards (8.78% by weight) helping to combat global warming. A subsequent 7-d air curing further enhanced the strength to outcompete those of 28-d air curing only, because rehydrated formation filled in capillary pores (reduced from 0.11 mL g−1 to 0.03 mL g−1). Moreover, fire resistance and thermal stability were improved by the chemistry of magnesia cement and accelerated carbonation. The carbonated particleboards retained high strength and stable dimension after 1-h heating up to 200 °C.