scholarly journals Stabilization/Solidification of Strontium Using Magnesium Silicate Hydrate Cement

Processes ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 163
Author(s):  
Tingting Zhang ◽  
Jing Zou ◽  
Yimiao Li ◽  
Yuan Jia ◽  
Christopher R. Cheeseman
Keyword(s):  
Magnesium Oxide ◽  
Silica Fume ◽  
Phase Formation ◽  
Magnesium Silicate ◽  
National Standard ◽  
Leaching Rate ◽  
Hydration Products ◽  
Hydrate Cement ◽  
Leaching Fraction ◽  
New Phase

Magnesium silicate hydrate (M–S–H) cement, formed by reacting MgO, SiO2, and H2O, was used to encapsulate strontium (Sr) radionuclide. Samples were prepared using light-burned magnesium oxide and silica fume, with sodium hexametaphosphate added to the mix water as a dispersant. The performance of the materials formed was evaluated by leach testing and the microstructure of the samples was also characterized. The stabilizing/solidifying effect on Sr radionuclide in the MgO–SiO2–H2O system with low alkalinity is demonstrated in the study. The leaching rate in a standard 42-day test was 2.53 × 10−4 cm/d, and the cumulative 42-day leaching fraction was 0.06 cm. This meets the relevant national standard performance for leaching requirements. Sr2+ was effectively incorporated into the M–S–H hydration products and new phase formation resulted in low Sr leaching being observed.

scholarly journals Control of Drying Shrinkage of Magnesium Silicate Hydrate Gel Cements

2016 ◽  
Vol 709 ◽  
pp. 109-113 ◽  
Author(s):  
Ting Ting Zhang ◽  
Xiao Min Liang ◽  
M. Lorin ◽  
Zhen Lin Wu ◽  
Chris Cheeseman ◽  
...  
Keyword(s):  
Portland Cement ◽  
Magnesium Oxide ◽  
Silica Fume ◽  
Drying Shrinkage ◽  
Magnesium Silicate ◽  
Hydration Products ◽  
Cement Ratio ◽  
Water To Cement Ratio ◽  
Order Of Magnitude ◽  
Forced Drying

Cracks were observed when the magnesium silicate hydrate gel cement (prepared by 40% MgO/ 60% silica fume) was dried. This drying cracking is believed to be caused when unbound water evaporates from the binder. The shrinkage upon forced drying to 200 °C of mortars made up from a reactive magnesium oxide, silica fume and sand was measured using dilatometry. The magnitude of the drying shrinkage was found to decrease when more sand or less water was added to the mortars and can be as low as 0.16% for a mortar containing 60 wt% sand and a water to cement ratio of 0.5, which is of a similar order of magnitude as observed in Portland cement based mortars and concretes. A simple geometrical interpretation based on packing of the particles in the mortar can explain the observed drying shrinkages and based on this analysis the drying shrinkage of the hydration products at zero added solid is estimated to be 7.3% after 7 days of curing.

scholarly journals Immobilization of Radionuclide 133Cs by Magnesium Silicate Hydrate Cement

Materials ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 146 ◽  
Author(s):  
Tingting Zhang ◽  
Tong Li ◽  
Jing Zou ◽  
Yimiao Li ◽  
Shiwei Zhi ◽  
...  
Keyword(s):  
Impact Resistance ◽  
Magnesium Silicate ◽  
Superior Performance ◽  
Transformation Rate ◽  
Leaching Rate ◽  
Hydrate Cement ◽  
The Impact ◽  
Better Than ◽  
Solidified Body ◽  
Gel System

The radionuclide cesium (Cs) was solidified using magnesium silicate hydrate (M–S–H) cement. The influence of Cs+ on the reaction of the M–S–H gel system was evaluated by measuring the compressive strength and microscopic properties of the solidified body. By testing the impact resistance, leaching resistance and freeze–thaw resistance of the solidified body, the immobilizing ability of Cs+ by the M–S–H cement was analyzed. Results indicate that Cs+ only slightly affects the reaction process of the M–S–H gel system, and only slows down the transformation rate of Mg(OH)2 into the M–S–H gel to a certain extent. The M–S–H cement exhibits superior performance in solidifying Cs+. Both the leaching rate and cumulative leach fraction at 42 d were considerably lower than the national requirements and better than the ordinary Portland cement-solidified body. The curing effect of the M–S–H cement on Cs+ is mainly physical encapsulation and chemisorption of hydration products.

scholarly journals Use Of Olivine For The Production Of MgO-SiO2 Binders

2021 ◽  
Vol 7 ◽  
Author(s):  
Scott Allan Nye ◽  
Shah Vineet ◽  
Oze Christopher ◽  
Shanks Barnaby ◽  
Cheeseman Chris
Keyword(s):  
Silica Fume ◽  
Isothermal Calorimetry ◽  
Magnesium Silicate ◽  
Binder System ◽  
Hydration Products ◽  
Cementitious Binder ◽  
Binding Component

The potential for using MgO and SiO2, recovered from olivine, was investigated for use as a cementitious binder system. The MgO to SiO2 proportion for the binder was fixed at 1:1. The nature of the hydration products were characterized using a variety of techniques including isothermal calorimetry, XRD, FTIR, and SEM. The primary binding component of the paste was determined to be magnesium silicate hydrate (M-S-H). The recovered silica exhibited faster reactivity compared to commercially available silica fume. Compressive strengths in excess of 20 MPa were obtained using the materials recovered from olivine.

Effect of Heavy Metals and Leaching Toxicity of Magnesium Potassium Phosphate Cement

2011 ◽  
Vol 117-119 ◽  
pp. 1080-1083 ◽  
Author(s):  
Bao Guo Ma ◽  
Jing Ran Wang ◽  
Xiang Guo Li
Keyword(s):  
Heavy Metals ◽  
Cement Hydration ◽  
Potassium Phosphate ◽  
National Standard ◽  
Magnesium Phosphate ◽  
Toxicity Tests ◽  
Hydration Products ◽  
Obvious Effect ◽  
Leaching Toxicity ◽  
Magnesium Potassium Phosphate Cement

Solidification / stabilization (S/S) is a popular method for treating solid wastes containing heavy metals. In recent years, it shows positive results of magnesium potassium phosphate cement as stabilizing agent. In the work, the influence of heavy metal Cu、Zn and Pb on magnesium phosphate cement and the leaching behavior of magnesium phosphate cement were studied. Two proportions of cements were employed with hard burned magnesia and potassium phosphate. The hydration products were analyzed by XRD showing that: Cu、Zn and Pb would not take on obvious effect during magnesium phosphate cement hydration process. Leaching toxicity tests showed that: Cu、Zn and Pb were immobilized within cement hydration products through physical fixation, adsorption mechanisms, and the results were far lower than that of the National Standard in China.

New phase formation of Gd[sub 2]O[sub 3] films on GaAs(100)

2001 ◽  
Vol 19 (4) ◽  
pp. 1434 ◽  
Author(s):  
A. R. Kortan ◽  
M. Hong ◽  
J. Kwo ◽  
J. P. Mannaerts ◽  
J. J. Krajewski ◽  
...  
Keyword(s):  
Phase Formation ◽  
New Phase

scholarly journals Effect of the MgO/Silica Fume Ratio on the Reaction Process of the MgO–SiO2–H2O System

Materials ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 80 ◽  
Author(s):  
Zhaoheng Li ◽  
Yudong Xu ◽  
Hao Liu ◽  
Jianwei Zhang ◽  
Jiangxiong Wei ◽  
...  
Keyword(s):  
Reaction Kinetics ◽  
Silica Fume ◽  
Main Product ◽  
Magnesium Silicate ◽  
Reaction Process ◽  
Reaction Products ◽  
Degree Of Reaction ◽  
Reaction Thermodynamics ◽  
Experimental Values ◽  
Kinetics Of

In order to clarify the effect of the MgO–silica fume (SF) ratio on the reaction process of the MgO–SiO2–H2O system, the reaction products and degree of reaction were characterized. Furthermore, the parameters of the reaction thermodynamics were calculated and the reaction kinetics were deduced. The results indicate that a large amount of Mg(OH)2 and small quantities of magnesium silicate hydrate (M–S–H) gels were generated upon dissolution of MgO. However, the M–S–H gels were continuously generated until the SF or Mg(OH)2 was consumed completely. For a MgO dosage less than 50% of the total MgO–SiO2–H2O system, the main product was M–S–H gel, while for a MgO dosage greater than 50%, the main product was Mg(OH)2. The results indicate that M–S–H gels have greater stability than Mg(OH)2, and the final reaction product was prone to be M–S–H gels. Based on the experimental values, an equation is proposed for the reaction kinetics of MgO.

Phase Segregation, Transition, or New Phase Formation of Plutonium Dioxide: The Roles of Transition Metals

2019 ◽  
Vol 58 (7) ◽  
pp. 4350-4364 ◽  
Author(s):  
Bingyun Ao ◽  
Jun Tang ◽  
Xiaoqiu Ye ◽  
Ran Tao ◽  
Ruizhi Qiu
Keyword(s):  
Transition Metals ◽  
Phase Formation ◽  
Phase Segregation ◽  
Plutonium Dioxide ◽  
New Phase

scholarly journals Formation of magnesium silicate hydrate cement in nature

2017 ◽  
Vol 175 (2) ◽  
pp. 308-320 ◽  
Author(s):  
Lisa de Ruiter ◽  
Håkon Austrheim
Keyword(s):  
Magnesium Silicate ◽  
Hydrate Cement

Evidence of a new phase formation (BaTi4O9) by barium implantation into TiO2

1994 ◽  
Vol 143 (3-4) ◽  
pp. 227-231 ◽  
Author(s):  
S.M.M. Ramos ◽  
N. Bonardi ◽  
R. Brenier ◽  
B. Canut ◽  
P. Thévénard ◽  
...  
Keyword(s):  
Phase Formation ◽  
New Phase
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