Influence of wollastonite on hydration and properties of magnesium potassium phosphate cements

Xu, Biwan; Lothenbach, Barbara; Winnefeld, Frank

doi:10.1016/j.cemconres.2020.106012

Cited by 64 publications

(26 citation statements)

References 68 publications

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“…The XRD patterns of the coating before the flame test show the presence of the main crystalline phases of CaCO 3 , KMgPO 4 ·6H 2 O, and MgO; after the flame test, new peaks attributed to KMgPO 4 , Ca 5 (PO 4 ) 3 (OH) (HAP), and CaO are also assessed in the XRD patterns ( Figure 10 b). Based on these results correlated with the literature [ 17 , 18 , 19 , 20 ] one can also consider the formation of HAP (or apatite phases [ 20 ]) with a low crystallinity degree in the reaction of the phosphate solution with calcium carbonate (at longer curing periods—up to 28 days) and its crystallization at the increase in temperature (during the flame test).…”

Section: Resultssupporting

confidence: 68%

Coatings Based on Phosphate Cements for Fire Protection of Steel Structures

et al. 2021

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Fire events in buildings can cause losses to human life and important material damage, therefore a great deal of attention is paid nowadays to fire prevention. Buildings based on steel structures are especially affected in the event of a fire, due to the important loss of load-bearing capability when steel is heated at temperatures higher than 500 °C. Therefore, one possible method to mitigate the deleterious effect of fire is to protect steel structures from direct heating by applying protective coatings. In this paper, the ability of magnesium phosphate cement (MPC), based on dead burned magnesite and calcium magnesium phosphate cement (CMPC) coatings, to protect a steel substrate was assessed. CMPCs were obtained by mixing partially calcined dolomite with a KH2PO4 (MKP) solution, and in some cases, with a setting retarder (borax). The main mineralogical compounds assessed by X-ray diffraction and electronic microscopy (SEM-EDS) in CMPC are MgO, CaCO3, and K-struvite (KMgPO4·6H2O). The coatings based on MPC and CMPC, applied to steel plates, were tested in direct contact with a flame; the coatings of MPC and CMPC without the borax addition prevented the temperature increase of a metal substrate above 500 °C. No exfoliation of coatings (MPC and CMPC without borax addition) was noticed during the entire period of the test (45 min).

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Section: Resultssupporting

confidence: 68%

Coatings Based on Phosphate Cements for Fire Protection of Steel Structures

et al. 2021

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“…The TG-DTG analysis of our hydration products is shown in Figure 7 a. The primary weight loss of the MKPC slurry occurred in the range of 30–200 °C, due to the change in quality caused by dehydration of the main hydration product struvite-K [ 36 ]. The mass loss is shown in Figure 7 b, indicating that, as the glass powder content increased at an M/P ratio of 1:1, the formation of hydration product struvite-K increased.…”

Section: Resultsmentioning

confidence: 99%

Effect of Waste Glass on the Properties and Microstructure of Magnesium Potassium Phosphate Cement

et al. 2021

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Waste glass is a bulk solid waste, and its utilization is of great consequence for environmental protection; the application of waste glass to magnesium phosphate cement can also play a prominent role in its recycling. The purpose of this study is to evaluate the effect of glass powder (GP) on the mechanical and working properties of magnesium potassium phosphate cement (MKPC). Moreover, a 40 mm × 40 mm × 40 mm mold was used in this experiment, the workability, setting time, strength, hydration heat release, porosity, and microstructure of the specimens were evaluated. The results indicated that the addition of glass powder prolonged the setting time of MKPC, reduced the workability of the matrix, and effectively lowered the hydration heat of the MKPC. Compared to an M/P ratio (MgO/KH2PO4 mass ratio) of 1:1, the workability of the MKPC with M/P ratios of 2:1 and 3:1 was reduced by 1% and 2.1%, respectively, and the peak hydration temperatures were reduced by 0.5% and 14.6%, respectively. The compressive strength of MKPC increased with an increase in the glass powder content at the M/P ratio of 1:1, and the addition of glass powder reduced the porosity of the matrix, effectively increased the yield of struvite-K, and affected the morphology of the hydration products. With an increase in the M/P ratio, the struvite-K content decreased, many tiny pores were more prevalent on the surface of the matrix, and the bonding integrity between the MKPC was weakened, thereby reducing the compressive strength of the matrix. At less than 40 wt.% glass powder content, the performance of MKPC improved at an M/P ratio of 1:1. In general, the addition of glass powders improved the mechanical properties of MKPC and reduced the heat of hydration.

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“…e strength gain is attributed to the presence of phosphate in the MPB samples due to condensed microstructure in the MPB samples [22]. e drying shrinkage represented in Figure 2 shows that on initial days there are no shrinkage and as the days increase the shrinkage also increases for both MB and MPB samples.…”

Section: Resultsmentioning

confidence: 99%

Investigation on Calcined Magnesium‐Based Mineral Powder and Its Behavior as Alternative Binder

Devi¹,

Sudalaimani²

2020

Advances in Materials Science and Engineering

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This paper investigates the behavior of calcined powder made of natural magnesite and natural steatite. The magnesite and steatite are made into a powder of ratio 3 : 1 by weight proportion, and the combination is thermally decomposed at a temperature of 1200° Celsius. The calcined powder along with and without Sodium Tripolyphosphate (STPP) salt is tested for its microscopic structural development, consistency, initial setting time, final setting time, and heat of hydration. The powder is made into paste with water/powder ratio as 0.25 and the hardened samples are tested for its compressive strength, drying shrinkage, pH value, SEM analysis, and XRD analysis. The results show that adding phosphate salt increases the hydration process, setting time, and strength aspects. The test samples are found with hydration products such as magnesium hydroxide and struvite. Thus, the present work shows that natural metamorphic magnesite and natural metamorphic steatite can be the potential alternative resource for the production of magnesium-based binder.

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Influence of wollastonite on hydration and properties of magnesium potassium phosphate cements

Cited by 64 publications

References 68 publications

Coatings Based on Phosphate Cements for Fire Protection of Steel Structures

Coatings Based on Phosphate Cements for Fire Protection of Steel Structures

Effect of Waste Glass on the Properties and Microstructure of Magnesium Potassium Phosphate Cement

Investigation on Calcined Magnesium‐Based Mineral Powder and Its Behavior as Alternative Binder

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