Magnesium Potassium Phosphate Research Articles

Investigation of Water Stability and Microcharacteristics of Magnesium Potassium Phosphate Cement Modified by Calcium Aluminate Cement and Wollastonite

Investigation of Water Stability and Microcharacteristics of Magnesium Potassium Phosphate Cement Modified by Calcium Aluminate Cement and Wollastonite

Influence and Mechanism of Borax on the Physico-Mechanical Properties of Magnesium Potassium Phosphate Cement Exposed to High Temperatures

Influence and Mechanism of Borax on the Physico-Mechanical Properties of Magnesium Potassium Phosphate Cement Exposed to High Temperatures

Investigation of Corrosion Mechanism of Ribbed Mild Steel Bars Coated with Magnesium Potassium Phosphate Cement Paste

Investigation of Corrosion Mechanism of Ribbed Mild Steel Bars Coated with Magnesium Potassium Phosphate Cement Paste

Multi-scale investigation of creep properties of potassium magnesium phosphate cement

This paper aims to study the creep properties of potassium magnesium phosphate cement from nanoscale to macroscale. In this paper, nanoindentation technology and statistical deconvolution theory are used to study the creep properties of individual phase in potassium magnesium phosphate cement in the nanoscale. Then, the creep modulus of individual phase in potassium magnesium phosphate cement are determined. Through micro indentation test in this paper, the micro indentation method cannot predict the macro creep properties of potassium magnesium phosphate cement due to its easy cracking property. The compositions and volume fractions of phases in potassium magnesium phosphate cement are determined by XRD, TG and MIP. Based on the homogenization theory and creep parameters of each phase, a theoretical model for predicting and adjusting the creep performance of magnesium phosphate cement is proposed, and by compared with the macro creep data, the accuracy of the model is verified.

Surface modification of magnesium oxide and its effect on the performance of magnesium phosphate cement

In applying magnesium phosphate cement, controlling its setting time is of great importance, and the activity of the main raw material, magnesium oxide, is the key. In this study, dead-burned magnesia was modified with different amounts of water glass and different thermal treatment temperatures, and the effects of MgO on the macroscopic properties and microstructure of magnesium potassium phosphate cement (MKPC) were studied.The results show that the setting time of MKPC prepared with modified magnesia is prolonged, and the increase of the amount of water glass, the longer the setting time is.The setting time of the sample with 15% water glass and 300 °C treatment increased from 4.3 min to 17.5 min, an increase of 307%.The compressive strength results show that the surface modification of MgO decreased MKPC's early strength, which decreased with an increase in the water glass content and a decrease in the thermal treatment temperature.However, when the curing reached 7 days, the samples' compressive strength exceeded that of the reference group, and the strength development was optimum when the content of water glass was 5% with 300 °C treatment. The 28 d strength increased from 65.8 MPa of the reference group to 72.4 MPa, an increase of 10%.Through scanning electron microscopy (SEM), it was found that new phases were formed in the surface modified samples at the later stage of hydration. Combined with the results of energy-dispersive spectroscopy (EDS), it was confirmed that the magnesium silicate hydrate gels (M-S-H) were formed.The mercury intrusion porosimetry (MIP) test results show that these M-S-H gels can refine the pore size of MKPC, and the porosity of the sample with 5% water glass and 300 °C treatment was reduced from 6.6510% to 6.0429%, which explains the improvement in the MKPC compressive strength. Therefore, the surface modification of magnesium oxide can greatly extend its setting time without adversely affecting its later performance.

Preparation and Properties of a Sulphoaluminate Magnesium-Potassium Phosphate Green Cementitious Composite Material from Industrial Solid Wastes.

The preparation of high-performance green cementitious material from industrial solid waste is a feasible large-scale utilization approach for industrial solid waste. This work investigates the feasibility of using industrial solid wastes in a sulphoaluminate–magnesium–potassium–phosphate cementitious composite material (SAC-MKPC) clinker preparation and the influence of the calcination temperature and clinker ingredients on the hydration behavior and mechanisms of the SAC-MKPC with a Mg/P ratio of 5. The results show that the novel SAC-MKPC that was prepared from aluminum slag, carbide slag, coal gangue, and magnesium desulfurization slag was composed mainly of mineral MgO, , and C2S and the calcination temperature of the main mineral phases was 1250–1350 °C. The solid-waste-based SAC-MKPC had better mechanical properties and excellent water resistance compared with the MKPC. The optimal compressive strength reached 35.2, 70.9, 84.1, 87.7, and 101.6 MPa at 2 h, 1 d, 3 d, 7 d, and 28 d of hydration, respectively. The X-ray diffraction spectra and scanning electron micrographs of the hydration products of the SAC-MKPC clinker showed that AFt and K-struvite crystals coexisted and adhered to form a dense structure. This work provides an innovative idea to produce green cementitious material using industrial solid wastes and may promote the sustainable development of the power and mining industries.

Perspective Compounds for Immobilization of Spent Electrolyte from Pyrochemical Processing of Spent Nuclear Fuel

Immobilization of spent electrolyte–radioactive waste (RW) generated during the pyrochemical processing of mixed nitride uranium–plutonium spent nuclear fuel is an acute task for further development of the closed nuclear fuel cycle with fast neutron reactors. The electrolyte is a mixture of chloride salts that cannot be immobilized directly in conventional cement or glass matrix. In this work, a low-temperature magnesium potassium phosphate (MPP) matrix and two types of high-temperature matrices (sodium aluminoironphosphate (NAFP) glass and ceramics based on bentonite clay) were synthesized. Two systems (Li0.4K0.28La0.08Cs0.016Sr0.016Ba0.016Cl and Li0.56K0.40Cs0.02Sr0.02Cl) were used as spent electrolyte imitators. The phase composition and structure of obtained materials were studied by XRD and SEM-EDS methods. The differential leaching rate of Cs from MPP compound and ceramic based on bentonite clay was about 10−5 g/(cm2·day), and the rate of Na from NAFP glass was about 10−6 g/(cm2·day). The rate of 239Pu from MPP compound (leaching at 25 °C) and NAFP glass (leaching at 90 °C) was about 10−6 and 10−7 g/(cm2·day), respectively. All the synthesized materials demonstrated high hydrolytic, mechanical compression strength (40–50 MPa) even after thermal (up to 450 °C) and irradiation (up to 109 Gy) tests. The characteristics of the studied matrices correspond to the current requirements to immobilized high-level RW, that allow us to suggest these materials for industrial processing of the spent electrolyte.

Effects of bentonite, diatomite and metakaolin on the rheological behavior of 3D printed magnesium potassium phosphate cement composites

In this study, the effects of bentonite, diatomite, and metakaolin on the rheological behavior of 3D printed magnesium potassium phosphate cement composites (3D printed MKPCs) were investigated through characterization of the material properties, including yield stress, plastic viscosity, thixotropy, and creep. The thixotropy was studied by assessing the hysteresis area and thixotropic parameters under dynamic shear tests. The structural stability was evaluated by assessing the creep recovery, modulus of the fresh cement pastes, and deformation rate of the printed specimens. The results showed that diatomite played a key role in enhancing the thixotropy of the 3D printed MKPCs. Bentonite was found to significantly enhance the static yield stress, creep resistance, and shape stability owing to its high water absorption in the 3D printed MKPCs. Isothermal calorimetry testing showed that all additives accelerated the hydration reaction, which was confirmed by the increased compressive strength. Finally, a schematic representation of the yield stress evolution with time was proposed, revealing the beneficial effects of three additives in MKPCs during different stages of 3D printing.

Investigation of aluminum nitrate as a set retarder of magnesium potassium phosphate cement: Mechanisms involved in diluted suspension

In this study, the influence of aluminum nitrate on the hydration process of magnesium potassium phosphate (MKP) cement was investigated experimentally and through thermodynamic modelling using diluted systems with Mg/PO4 molar ratio and water-to-cement ratio of 1 and 100 respectively. Three processes contributed to retard cement hydration: the acidic nature of aluminum nitrate which reduced the initial pH of the solution by two units, the early precipitation of a taranakite-like amorphous potassium aluminophosphate, which reduced the aqueous phosphate and potassium concentrations, and a salt effect due to the presence of soluble nitrate. Precipitation of potassium-containing magnesium phosphate hydrates, like Mg2KH(PO4)2⋅15H2O and K-struvite, was prohibited, whereas precipitation of newberyite and cattiite was delayed. Furthermore, the modelled phase development with ongoing cement hydration agreed rather well with the experimental findings.

Experimental research on the utilization of gold mine tailings in magnesium potassium phosphate cement

Gold mine tailings (GT) are fine-grained ore processing wastes with a high variety of minerals and metals. Storing large amounts of GT in impoundments results in a waste of resources and in several cases environmental pollution. Magnesium potassium phosphate cement (MKPC) is green-sustainable cement made by magnesia (MgO, M) and KH2PO4, which can be used to effectively immobilize radioactive and hazardous wastes elements through mineralization and microencapsulation. This paper aimed at the utilization of GT in MKPC.GT was incorporated into MKPC through two different pathways, either partially replacing M or the binder (both M and KH2PO4). The influences of GT on MKPC were evaluated through workability, compressive strength, and microstructure. It was found that the partial replacement of M by GT can result in better workability, denser microstructure and higher late-stage compressive strength. The incorporation of GT generates new types of hydrates in the structure. The compressive strength was improved by a factor of 114.94% when an additional 10% M was replaced by GT; when the displacement of GT was 30%, it yielded a compressive strength approaching the basic group. Therefore, the partial replacement of M with GT was suitable to incorporate GT into MKPC in order to achieve the utilization of GT, reduce the cost and improve the mechanical properties of MKPC.

Study on improving interface bonding performance of magnesium potassium phosphate cement mortar

To enhance the interfacial bonding performance between magnesium potassium phosphate cement (MKPC) repair mortar and matrix concrete, in this study, MKPC modified mortar was used as the repair material to splice long prismatic test pieces. The four-point bending test was used to determine the flexural bearing capacity of the long prism, and the influence of changing the interface conditions and the modifying the MKPC repair mortar on the improvement of the basic performance of the splicing component is investigated.The research results show that, when the matrix concrete section is in a natural state, applying silica-fume modified MKPC interface agents on the interface with a repair thickness of 3 cm can improve the interface bonding performance. Furthermore, the working performance and mechanical properties of the MKPC repair mortar modified using nickel-iron slag and steel fibers have been significantly improved.

Building Envelope Prefabricated with 3D Printing Technology

The Fourth Industrial Revolution represents the beginning of a profound change for the building sector. In the last decade, the perspective of shapes, materials, and construction techniques is evolving fast due to the additive manufacturing technology. On the other hand, even if the technology is growing fast and several 3D printed buildings are being developed worldwide, the potential of concrete 3D printing in building prefabrication remains unexplored. Consequently, the application of new digital fabrication technologies in the construction industry requires a redesign of the construction process and its components. This paper proposes a novel conception, design, and prototyping of a precast building envelope to be prefabricated with extrusion-based 3D concrete printing (3DCP). The new design and conception aim to fully exploit the potential of 3D printing for prefabricated components, especially in terms of dry assembly, speed of implementation, reusability, recyclability, modularity, versatility, adaptability, and sustainability. Beyond the novel conceptual design of precast elements, the research investigated the 3D printable cementitious material based on a magnesium potassium phosphate cement (MKPC), which was devised and tested to ensure good performances of the proposed component. Finally, a prototype has been realised in scale with additive manufacturing technology in order to verify the printability and to optimize the extruder path. This study leads us to believe that the combined use of prefabricated systems, construction automation, and innovative materials can decisively improve the construction industry’s sustainability in the future.

Effect of phosphogypsum on the properties of magnesium phosphate cement paste with low magnesium-to-phosphate ratio

The incorporation of phosphogypsum (PG) in magnesium potassium phosphate cement (MPPC) can promote the utilization of PG not only by utilising the phosphate impurity in PG, but also by immobilising the heavy metals with MPPC. This paper investigates the feasibility of the incorporation of PG in preparing MPPC. Both early age properties, including workability and setting time, and hardened properties of compressive strength and microstructure, of PG-incorporated MPPC paste were investigated, and the hydration mechanism was explored. The results indicated that the addition of PG increased the workability of MPPC and extended the setting time of MPPC. However, incorporation of 20% PG slightly reduced the compressive strength because higher PG content led to the loose microstructure. Moreover, the addition of PG did not change the formation of hydration product, while it only reduced the hydration heat. Finally, compared to PG, the concentration of leached heavy metals of MPPC with PG was significantly reduced after 28 days curing.

Piezoelectric properties and microstructure of ceramicrete-based piezoelectric composites

Inorganic piezoelectric ceramic composite is the potential sensing element for long-term structural health monitoring due to its excellent durability and compatibility. In this study, a Ceramicrete-based piezoelectric composite is proposed preliminarily, in which the magnesium potassium phosphate cement is used as the matrix and the lead zirconate titanate particle is utilized as the functional phase. Piezoelectric properties test and microstructure analysis are performed to evaluate the testing samples. Results show that the piezoelectric performance of the composite increase with the increase of piezoelectric ceramic particle size. The value of the piezoelectric strain factor (d33) can reach 83.8 pC/N, while the corresponding piezoelectric voltage factor (g33) is 50.1 × 10-3 V•m/N at the 50th day after polarization. Microstructure analysis illustrates that the interfacial transition zone (ITZ) between the matrix and the particles is dense. Moreover, the influence of aging on the composite is attributed to the continuous hydration after polarization. It indicates that the composites have a higher piezoelectric performance, which can be regarded as a promising sensing element material.

Crystallization of struvite-K from pumpkin wastes.

Use of slow-release fertilizers derived from biological sources is important in sustainable agricultural development. Struvite-K (KMgPO4 ·6H2 O) is magnesium potassium phosphate mineral that has high potential for use as fertilizer in agriculture. Struvite-K is particularly suitable for slow-release fertilizer systems since struvite-K crystals are sparingly soluble in water. Seeds of pumpkin Cucurbita pepo L. are recovered and consumed as food, but the remaining pulp has no economic value. The present study evaluated the feasibility of struvite-K crystals recovery from pyrolysis products of pumpkin wastes. In the study C. pepo pulp was decomposed at high temperatures and potassium was extracted from the residue and then crystalized from the solution by addition of NaH2 PO4 ·2H2 O and MgCl2 ·6H2 O salts. Struvite-K was characterized by Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy-energy-dispersive X-ray (SEM-EDX) spectroscopy and X-ray diffraction (XRD) analysis. The study revealed pumpkin wastes can be evaluated as source of potassium and 80% of potassium could be recovered as struvite-K crystals, which have a potential use as a slow-release mineral fertilizer for sustainable agriculture operations. © 2021 Society of Chemical Industry.

Effects of Kinetic Parameters on Initial Setting Time, Microstructure and Mechanical Strength of Volcanic Ash-based Phosphate Inorganic Polymers

This study assesses the effects of curing temperatures (28 and 60 °C) and P2O5 / H2O molar ratio percentages (4 to 12 %) on initial setting time, microstructure and mechanical strength of volcanic ash-based phosphate inorganic polymers. The inorganic polymers along with the raw materials were characterized by X Ray Fluorescence (XRF), X Ray Diffraction (XRD), Fourier Transform Infra Red (FTIR) spectroscopy and Scanning Electron Microscopy (SEM). In addition, initial setting time of pastes was determined along with compressive strength and water absorption on specimens aged 28 days. The results showed that initial setting time decreases with the increase of P2O5 / H2O molar ratio percentage in the range of 126 − 20 Min (28 °C) and 20 − 10 Min (60 °C). Conversely, either at 28 or 60 °C curing, compressive strength increases with the increase of P2O5 / H2O molar ratio percentage. FTIR spectra show the presence of Ca-O and Fe-O and Al-O-P-O bonds. Dependent on curing temperature, new crystalline phases including hydroxyl apatite, brushite, sigloite, aluminium phosphate hydrate, potassium magnesium phosphate hydrate and silicon hydrogen phosphate were formed. Hence, initial setting time, microstructure and mechanical strength of volcanic ash-based phosphate inorganic polymers are P2O5 / H2O molar ratio percentage, curing temperature and chemical composition dependent.

Highly efficient phosphorus and potassium recovery from urine via crystallization process in a fluidized bed reactor system

Human urine consists of large amounts of phosphorus (P) and potassium (K), which are essential chemical elements for living species and plants growth. In this study, we investigate the effects of reflux rate on crystallization promotion to simultaneously recover P and K from urine. The effects of potassium ion presence in the formation of magnesium ammonium phosphate (MAP) in the fluidized bed reactor (FBR) is also studied. The largest removal efficiency of P at 96.57% and K at 68.40% can be achieved under the optimal conditions of: pH 9.5, P:Mg:N molar ratio of 1:1.4:1.2, and reflux rate of 12 L min–1. The purity of produced MAP and magnesium potassium phosphate (MPP) are both promoted, owing to the improved formation frequency among particles, when reflux rate is increased. During the MAP production process, MgKPO4 is initially nucleation and growth under turbulence environmental in FBR. Afterwards, with the presence of NH4+ in solution, K + ion can be replaced by NH4+ and formed the MAP due to more stability of MgNH4PO4 compound than MgKPO4. The cost analysis demonstrates that FBR system can provide a profit of $2.01/m3 on urine treatment. The investigation can shed lights on efficient removal and recovery process of P and K elements from urine through changing various reflux rates for further development.

Two-scale modelling of fracture of magnesium phosphate cement under bending using X-ray computed tomography characterisation

This paper presents an efficient experimental-numerical analysis of fracture mechanics in magnesium phosphate cement (MPC) based on the structural and mechanical properties of its constituents including potassium magnesium phosphate hexahydrate (MKP), magnesium oxide (MgO) and pores. At micro-scale, the fracture energy and material strength of solid phases were obtained relying on the combination of nanoindentation experiments and simulation. The X-ray computed tomography (XCT) image-based 3D meso-structure model of MPC beam was generated and incorporated with the finite element cohesive zone model to analyse the fracture process of MPC beam under three-point bending. The unknown fracture parameters of cohesive elements at the interface between MKP and MgO were determined via the model calibration process conditional to the experimental data in terms of relationship between macro-load and crack mouth opening displacement. The cohesive strengths obtained for MKP, MgO and MKP-MgO were found to be 5.8, 106 and 24 MPa, respectively. In the same order, the fracture energies were0.02, 0.08 and 0.04 N/mm, respectively.

Study on water instability of magnesium potassium phosphate cement mortar based on low-field 1H nuclear magnetic resonance

Low-field 1H nuclear magnetic resonance (LF-NMR) is applied to investigate water instability of magnesium potassium phosphate cement (MKPC) mortar immersed in neutral and alkaline solutions, aiming to introduce a in-situ monitoring of microstructure to demonstrate the deterioration process of MKPC mortar. By tracking the evolution of water bearing pore, the deterioration is well characterized, and mainly attributed to the coarsening of micro-pores in the K-struvite network. Compared with tap water, 2.5 wt% NaCl and MgSO4 solutions, dramatical deterioration of strength and microstructure are detected in the MKPC mortar exposed in 2.5 wt% NaOH solution. In addition, the millimeter sized water cavity is formed due to the opening of the spherical closed pores in the later exposure stage in both neutral and alkaline solutions.

Properties of magnesium potassium phosphate cement-expanded perlite composites applied as fire resistance coating

Cement-based composites have been a commonly used fire resistance material. As a new cement, magnesium potassium phosphate cement (MKPC) has been a popular and important research object due to its various excellent properties including heat resistant. However, only limited studies have been conducted on its application as fire-resistant coating. In this paper, the thermal properties of MKPC blended with/without expanded perlite (EP) under fire exposure were investigated. Two types of EP with open-pore and closed-pore structures were used, and each type of EP contained two different sized particles including 212–270 μm and 270–550 μm. The fluidity and setting time of MKPC-EP composites and adhesive strength between MKPC-EP composites coating and plywood were measured. The fire resistance properties of MKPC-EP composites were studied, including loss of weight (LOW), generated cracks, phase changes, thermal analysis, residual adhesive strength, and microstructure changes. The obtained results were intended to reveal the feasibility of MKPC-EP composites applied as coating to protect the substrate against exposure to fire. The addition of EP decreased the fluidity, extended the setting time, and enhanced the adhesive strength before and after fire test. LOW and accumulative lengths of visible cracks after fire exposure reduced for certain formula and are dependent on the pore structures, sizes and dosage of EP. X-ray diffraction (XRD) investigation and thermal analysis-infrared spectroscopy reveal MgKPO4⋅6H2O decomposed to MgKPO4⋅H2O by losing crystal water stage by stage during elevating temperature. Scanning electron microscopic (SEM) observations show that EP refined the MgKPO4⋅6H2O, and, after exposure to flame, the MKPC-EP exhibited a much denser microstructure with interconnecting MgKPO4·H2O of radiative flakes, when compared to the MKPC paste.