Magnesium Phosphate Cement Matrix Research Articles

Electromagnetic wave absorption performance of rapid emergency magnesium phosphate cement (MPC) canvas

This study leverages the rapid emergency protection advantages of magnesium phosphate cement (MPC) canvas to develop a novel electromagnetic wave-absorbing material based on MPC canvas. The composite is composed of an MPC matrix with magnetite and iron powder as absorbers, arranged in a gradient structure. The research investigates the effects of absorbers and gradient contents on the electromagnetic wave absorption performance (EWAP) of MPC canvas. Experimental results show a maximum RL of −37.2 dB in the 2–18 GHz range, with a 6.3 GHz absorption bandwidth below −10 dB. Simulations further confirm that the gradient MPC canvas exhibits excellent EWAP across different frequency bands. The gradient design effectively adjusts the electromagnetic parameters through multiple reflection, scattering, and interference attenuation effects within the multilayer structure, enabling broadband absorption of electromagnetic waves.

Research on the properties of brucite-based magnesium phosphate cement fire resistive coating for steel structures

Magnesium Phosphate Cement (MPC) exhibits high strength, exceptional high-temperature resistance, and outstanding adhesion properties at the steel interface, rendering it an ideal material for fire resistive coatings on steel structures. In this study, natural brucite powder was employed as the magnesium source, while hollow glass microspheres (HGM) were utilized as functional modifiers to formulate brucite-based MPC fire resistive coatings for steel structures. This research explored the influence of the mass ratio of brucite powder to ammonium dihydrogen phosphate (M/P), the brucite particle size, and the addition of HGM on the physical, mechanical, and fire-retardant properties of the coatings. The microstructure of the brucite-based MPC before and after fire testing was examined using SEM, XRD, TG-DTG, and X-CT. The results indicated that with an M/P ratio of 2.5:1 and a brucite particle size of 75–150 μm, the material exhibited optimal overall performance and was suitable as a matrix material for MPC. The incorporation of an appropriate amount of HGM increased the compressive strength of brucite-based MPC by 33.4 %, reduced the dry density by 20.5 %, extended the fire resistance of the structure, and decreased the thermal conductivity by 48.2 %. This can be attributed to: (i) HGM filling the pores in brucite-based MPC, creating a denser microstructure; (ii) HGM forming a closed porous structure with the MPC matrix, reducing thermal conductivity and increasing thermal resistance; (iii) The low thermal diffusivity of HGM/MPC impeded heat transfer, thereby decelerating thermal decomposition and flame propagation.

Ground granulated blast furnace slag-modified magnesium phosphate cement used as grouting material: Workability, mechanical property and corrosion resistance optimization

Calcium oxide and alumina, which are significant components of ground granulated blast furnace slag (GGBS), can participate in the hydration reaction with phosphate. This study examines the effect of incorporating GGBS as a mineral admixture on the fresh, mechanical, and durability properties of two-component magnesium phosphate cement (MPC)-based grouting materials. The findings reveal that GGBS replacement not only reduces the setting time and the heat released during hydration but also optimizes the fluidity of the fresh slurry at the appropriate replacement level. The optimal content of 20 % GGBS replacement significantly improves the mechanical properties of MPC grouts, achieving up to 28.4 MPa at 28 days, and enhances their resistance against the corrosion of water, chloride, and sulfate ions. XRD results show that the incorporation of GGBS leads to the formation of amorphous phases and secondary hydration products. These findings are corroborated by SEM analysis, which reveals gel-like new hydration products in matrices containing GGBS. Additionally, the incorporation of GGBS reduces the appearance of microcracks and gaps, resulting in a denser microstructure of the MPC matrix.

Properties of red mud blended magnesium phosphate cements: Workability and microstructure evolution

Alumina and iron oxide which constitute significant components of red mud can participate in the hydration reaction with phosphate. This paper partially replaced magnesia with red mud in the preparation of magnesium phosphate cement (MPC) and investigated the effects of red mud substitution on the performance of fresh and hardened properties of the MPC. The fresh properties of MPC were analyzed by measuring the setting time, fluidity, early hydration heat release and rheological properties, while the hardened mechanical properties were characterized by compressive strength measurement. The phase composition and micro-morphology were examined by XRD, SEM, EDS, and TG-DTA. The experimental results demonstrated that the incorporation of red mud prolonged the setting time, and postponed the occurrence of the peak temperature, and reduced the hydration reaction intensity. Regarding to the rheological properties, an increase in the dynamic yield stress was followed by a decline with gradually addition of red mud. Conversely, the plastic viscosity increased consistently. Concerning hardened properties, adding appropriate amount of red mud powders to MPC can significantly improve the compressive strength of hardened MPC mortars. The samples containing 15 % red mud yield the highest compressive strength, especially in the early strength, it was even more pronouncedly improved by 14.8 % comparing to the controlled samples at 3 h. Furthermore, detailed information about the modification effects of red mud on the MPC microstructure has been studied. The density of the MPC matrix was improved, microcracks and gaps appeared less, and some new hydrates could be determined, which is responsible for the improvement of the MPC’s mechanical properties.

Effect of matrix electrical and micro-structural properties on the self-sensory capabilities of smart textile reinforced composites

This study investigates the effect of the matrix properties on the structural and sensory capabilities of smart self-sensory textile reinforced cement composites, in which carbon rovings are simultaneously used as the main reinforcement system and as the sensory agent. The investigation focuses on two different cementitious matrices: Portland cement (PC) and Magnesium Phosphate cement (MPC). The differences are associated with the matrix electrical and micro-structural behaviors. It is demonstrated that compared to PC matrix, MPC matrix is characterized by a relatively high electrical resistivity, which enhances the electrical signal. It is further demonstrated that the advanced material properties of the MPC matrix improves the textile-matrix interaction, and, as a result, the structural performance of the composites. The characterization is affected and reflected by the measured electrical resistance change (ERC). The integrative gauge factor (GF) concept was chosen to demonstrate the different structural – electrical correlations associated to the matrices. It is presented that the matrix type is reflected by the value and trend of the GF. While carbon-based textile reinforced PC elements are characterized by nonlinear and lower GF values, in the case of textile reinforced MPC elements, the GF is linear and its value is about 2.5 times higher.

INTELLIGENT TEXTILE AND FIBER REINFORCED MPC COMPOSITES FOR SHM

This study develops novel intelligent composite structural elements combining three advanced technologies: magnesium phosphate cement (MPC) matrix, smart-self sensory carbon-based textile reinforcement system, and additive short-dispersed fibers. In such system, the carbon rovings simultaneously serve as the main reinforcement system and the sensory agent. The material properties of the MPC matrix include minimization of environmental effects, high flexural strength and enhanced rheological properties which is an advantage in textile reinforcement system. From the sensory point of view, MPC is electrically insulated matrix which enhances the measured electrical signal from the carbon rovings. Experimental investigation demonstrates the advanced capabilities of the new hybrid structures. The investigation compares between the structural and electrical responses of textile reinforced MPC elements and TRC elements under flexural loading. The structural-electrical correlation enables to further explore new composite configurations and to develop enhanced smart self-sensory systems. The study demonstrates that by merging MPC mixture with textile and fiber reinforcement systems, it is possible to design and construct thin-walled, elements with advanced structural and self-sensing capabilities.

Water-resisting performances and mechanisms of magnesium phosphate cement mortars comprising with fly-ash and silica fume

Design of hydraulic structures using magnesium phosphate cement (MPC) composites is a still challenging issue because of the volume instability of MPC matrices in water environment. In this research, an attempt was taken to progress the water-resistance performance of MPC blended with fly ash (FA) and silica fume (SF). The FA was introduced as one third of magnesia in the mortar specimens, where SF dosages were 5%, 10% and 15% as the substitution of magnesia. Physico-mechanical and microstructural properties of mortar samples were examined considering the air and water curing systems. The analytical results bared that compressive strength (CS) and flexural strength (FS) of specimens composed with MPC + FA+5%SF were observed about 25% higher as compared to control. Both strength properties having the optimized content of SF (i.e. 5%) was reduced close by 3–4% in water system, whereas the pure MPC matrix exhibited around 20% less at 28 d. In addition, mass loss (ML) was found nearby 1.56% at 28 d. Moreover, SEM, EDS and XRD tests were detected that intermediate minerals namely Berlinite, Mullite, Lizardite and Enstatite were formed in the microstructures, and micro-cracks and micro-pores were significantly reduced. Consequently, compact microstructure was obtained that resulted the well water-resistant of proposed MPC mortar. The outcomes of this research might be a potential information for constructing the MPC-based water structures.

Effect of Vehicle-Bridge Coupled Vibration on the Performance of Magnesium Phosphate Cement Repair Materials.

This study evaluates the effect of vehicle–bridge coupled vibration on the mechanical properties of fiber-reinforced magnesium phosphate cement (FR-MPC) composites and the bonding properties of repaired systems. By means of compressive and flexural bond strengths, fiber pullout, mercury intrusion porosimeter (MIP) and backscattered electron imaging (BSE) analysis, an enhanced insight was gained into the evolution of FR-MPC performance before and after vibration. Experimental results showed that the compressive strength and flexural strength of FR-MPC was increased when it was subjected to vibration. However, the effects of vibration on the flexural strength of plain magnesium phosphate cement (MPC) mortars was insignificant. The increased flexural strength of FR-MPC after vibration could be due to the high average bond strength and pull-out energy between the micro-steel fiber and the MPC matrix. Moreover, BSE analysis revealed that the interface structure between FR-MPC and an ordinary Portland cement (OPC) substrate was more compacted after vibration, which could possibly be responsible for the better bonding properties of FR-MPC. These findings are beneficial for construction project applications of FR-MPC in bridge repairing and widening.

Deflection hardening behaviour of ductile fibre reinforced magnesium phosphate cement-based composite

This study aims to develop the ductile fibre reinforced magnesium phosphate cement-based composite (DFRMC) to address the inherent brittleness of magnesium phosphate cement (MPC). An experimental program was conducted, in which the effects of fly ash substitute (FA) content, PVA fibre volume fraction (Vf), sand to binder mass ratio (S/B) and water to solid mass ratio (W/Solid) on the properties of DFRMC were investigated. The test results revealed that all DFRMCs, except for those with mix of FA content of 0%, 10% and W/B of 0.10, can exhibit deflection hardening behaviour accompanied by multiple fine cracks under bending. The new indexes, flexural strength gap (fg), deflection gap (Dg), and toughness gap (Tg) were introduced in this study to accurately evaluate the deflection hardening capacity. The developed DFRMC with FA content of 20%, Vf of 1.6%, S/B of 0.2 and W/Solid of 0.13 showed the superior deflection hardening capacity as compared to other DFRMCs. Meanwhile, a moderate compressive strength of about 40 MPa, nominal flexural strength of 7.60 MPa and a relatively high slump value (over 250 mm) can be achieved. Furthermore, the denser MPC matrix and rough PVA fibre surface of DFRMC were investigated by using the scanning electron microscope (SEM) method.

Effect of Cr (III) on hydration, microstructure of magnesium phosphate cement, and leaching toxicity evaluation.

The pollution caused by chromium and its compounds has caused severe harm to the environment, and waste stabilization/solidification containing these contaminants by magnesium phosphate cement (MPC) is one of the best ways to address this problem. If the mechanism between Cr3+ and MPC can be understood, it will significantly improve the latter's solidification performance with respect to ameliorating Cr pollution. In this paper, the compressive strength, microstructure, pH in the process of sample hydration, and leaching toxicity of solidified forms were studied by adding various amounts of Cr3+ into MPC. The setting time of MPC decreased at first and then increased as the Cr3+ concentration increased. The added Cr3+ reacted with the phosphate ions to form mineral phases, which changed the MPC matrix structure. The matrix's compressive strength was higher when the M/P ratio (MgO/KH2PO4 mass ratio) was smaller. When the concentration of Cr3+ was constant, and the M/P ratio was low (< 4:1), the matrix's compressive strength increased as the M/P ratio increased. The presence of Cr3+ changed the system's pH and affected the hydration products' morphology; this trend strengthened as the Cr3+ concentration increased. The highest leaching concentration of Cr3+ was 0.255mg/L, and the concentration decreased as the M/P ratio decreased. During solidification, the appropriate proportion of MPC can be selected according to the concentration of Cr3+ to achieve better solidification performance.

Water distribution characteristics and research with capillary absorption for magnesium phosphate cement-coated cement pastes

Magnesium phosphate cement (MPC) is a cementitious material formed by an acid-base reaction, which has usually developed as repair material for rehabilitation engineering. It also has the potential as coating materials for fire-resistance and for corrosion protection. In this study, the effect of magnesium phosphate cement as an inorganic coating on the water permeability of cement-based material is studied. X-ray computed tomography (XCT) was used to track the capillary adsorption process of hardened cement non-destructively. The results showed that magnesium phosphate cement as the coating of cement-based materials has an excellent resistance to water penetration, and the quantitative and qualitative analysis of XCT water penetration was conducted. The microstructure analysis showed that the MPC matrix has much smaller porosity and pore sizes than the OPC matrix, and the interphase of OPC and MPC is dense and continuous, which may provide a remarkable effect on the capillary absorption blocking process. According to the Lucas-Washburn equation, a linear relationship between water absorption height and the square root of time was established to verify the experimental results measured/calculated by XCT.

Preparation and properties of sustainable magnesium phosphate cement composites with recycled tire rubber particles

The disposition of the discarded tire rubber has become a worldwide problem with the quick development of auto industry. The application of recycled tire rubber (RTR) particles in cement-based materials is effective method for large-scale treatment of discarded tire rubber. Magnesium phosphate cement (MPC) is a repairing material commonly used in road and bridge engineering. In order to investigate the effects of RTR particles on the properties of MPC, sustainable rubberized MPC mortars with three different sizes were designed and prepared. The workability, mechanical properties, capillary water absorption and durability of rubberized MPC mortars were measured, and the interface zone between RTR particles and MPC matrix was characterized by Back-scattered Electron Detector (BSE). Test results indicate that the presence of RTR particles decreases the fluidity, compressive strength and bonding strength of MPC mortar at different levels, and it also decreases the capillary water absorption, increases the water resistance and volume stability to some extent. Both the content and fineness of RTR particles are key factors influencing the properties of rubberized MPC mortar. From one perspective, the difference in the interface zone between RTR particles and MPC matrix can explain the different effects of the three types of RTR particles. And MPC mortar with middle-size RTR particles has the most homogeneous microstructure.

The Effect of Nano-SiO2, Nano-Al2O3, and Nano-Fe2O3 on the Compressive Strength and Workability of Magnesium Phosphate Cement-Based Mortar

Abstract Magnesium phosphate cement (MPC) possesses many excellent engineering properties. The applications of MPC as a repair and quick-construction material have received significant research attention in recent years. The effects of nano-silicon dioxide, nano-aluminum oxide (Al2O3), and nano-iron oxide (Fe2O3) on the compressive strength and the fluidity of the MPC-based mortar are experimentally investigated in this study. The micromorphology and composition of the MPC-based mortar with nanoparticles were captured using scanning electron microscopy and X-ray diffraction, respectively. It was found that the addition of the nanoparticles significantly shortened the setting time of MPC and decreased the fluidity of the MPC-based mortar. The addition of the appropriate amount of nano-Fe2O3 and nano-Al2O3 improved the compressive strength of the MPC-based mortar. The optimal replacement ratios of the nano-Fe2O3 and nano-Al2O3 were 2 % and 4 %, respectively. The reaction product of aluminum phosphate x-hydrate (AlPO4 xH2O) was found in the MPC matrix with the addition of nano-Al2O3, which improved the compressive strength of the MPC-based mortar.

Effect of silica fume and basalt fiber on the mechanical properties and microstructure of magnesium phosphate cement (MPC) mortar

This paper evaluates the effect of silica fume (SF) and basalt fibers (BF) on the mechanical properties and microstructure of magnesium phosphate cement (MPC) mortar. Several MPC mortar mixtures with different contents of SF and BF were prepared. Experimental results revealed that the compressive strength and flexural strength of MPC mortar was increased by increasing the percentages of SF from 0% to 10%. Incorporation of BF improved the flexural strength and post-peak flexural behaviour of the load-deflection curve of MPC mortars, but its effect on the compressive strength was insignificant. MPC matrix with 10%SF and 0.5%BF demonstrated the highest compressive and flexural strength of 49.42 MPa and 5.31 MPa respectively at the 28 days. XRD and SEM analysis showed that control mixture without SF and BF contained more unreacted magnesia and struvite as compared to MPC mortars containing SF and BF. Moreover, SEM-EDS analysis of MPC mixtures incorporating SF and BF showed that SF and fly ash (FA) reacted within the MPC paste system to produce the secondary hydration products. It was postulated that magnesium silicate, aluminium or silicon phosphate phases were formed during the reaction of SF and FA in the MPC system. These secondary products tend to improve the bonding of solid phase and hence mechanical properties of MPC mortar. Finally, SEM-EDS analysis also confirmed the excellent interaction of BF with the MPC hydration products.

Study on an Improved Phosphate Cement Binder for the Development of Fiber-Reinforced Inorganic Polymer Composites

Magnesium phosphate cement (MPC) has been proven to be a very good repair material for deteriorated concrete structures. It has excellent adhesion performance, leading to high bonding strength with old concrete substrates. This paper presents an experimental study into the properties of MPC binder as the matrix of carbon fiber sheets to form fiber-reinforced inorganic polymer (FRIP) composites. The physical and mechanical performance of the fresh mixed and the hardened MPC paste, the bond strength of carbon fiber sheets in the MPC matrix, the tensile strength of the carbon FRIP composites and the microstructure of the MPC matrix and fiber-reinforced MPC composites were investigated. The test results showed that the improved MPC binder is well suited for developing FRIP composites, which can be a promising alternative to externally-bonded fiber-reinforced polymer (FRP) composites for the strengthening of concrete structures. Through the present study, an in-depth understanding of the behavior of fiber-reinforced inorganic MPC composites has been achieved.

Bioactive calcium sulfate/magnesium phosphate cement for bone substitute applications

A novel calcium sulfate/magnesium phosphate cement (CSMPC) composite was prepared and studied in the present work. The physical properties including the phases, the microstructures, the setting properties and the compressive strengths of the CSMPCs were studied. The bio-performances of the CSMPCs were comprehensively evaluated using in vitro simulated body fluid (SBF) method and in vitro cell culture. The dependence of the physical and chemical properties of the CSMPC on its composition and microstructure was studied in detail. It is found that the CSMPC composites exhibited mediate setting times (6–12min) compared to the calcium sulfate (CS) and the magnesium phosphate cement (MPC). They showed an encapsulation structure in which the unconverted hexagonal prism CSH particles were embedded in the xerogel-like MPC matrix. The phase compositions and the mechanical properties of the CSMPCs were closely related to the content of MPC and the hardening process. The CSMPCs exhibited excellent bioactivity and good biocompatibility to support the cells to attach and proliferate on the surface. The CSMPC composite has the potential to serve as bone grafts for the bone regeneration.