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Characteristic of refractory materials upon hydration - Expansion volume and pressure

Title
Characteristic of refractory materials upon hydration - Expansion volume and pressure
Other Titles
수화반응에 따른 폐내화물 특성 – 팽창량 및 팽창압
Author
박상훈
Alternative Author(s)
박상훈
Advisor(s)
박두희
Issue Date
2021. 2
Publisher
한양대학교
Degree
Master
Abstract
Refractory waste are produced during high-temperature processes and operations in steel, glass, ceramic, and cement industries. Magnesium oxide (MgO), one of the main chemical components in refractories, becomes magnesium hydroxide (Mg(OH)2) upon hydration with volume expansion. This study investigated the volume-expansion characteristics during MgO hydration and the pore-scale swelling mechanism. The packing of two types of MgO granules calcined at a relatively low (i.e., dead-burned magnesia, DBM) and a high relatively temperature (i.e., crystal-fused magnesia, CFM) was subjected to a stepwise hydration sequence, and the changes in weight and volume were measured in conjunction with three-dimensional (3D) X-ray computed tomography imaging at each step. The results showed that the DBM particles had a smaller grain size than that of the CFM particles, which induced a quicker hydration reaction. At the early stage of hydration, the DBM particles exhibited a noticeable volume expansion and weight increase, and the pore space was quickly filled with Mg(OH)2. The CFM particles gradually cracked, with a lower rate of swelling toward the asymptotic values, similar to the DBM particles. The results of this study indicate that the direct reuse of refractories as an aggregate in cement concrete or as a backfill material may not be ideal owing to the volume expansion. However, the volume-expansion behavior of MgO hydration can be used to modify soil properties such as the hydraulic conductivity, or to mitigate ground settlement. The results of the experiment on the expansion amount and expansion pressure of magnesia are performed. In the expansion amount experiment, Confining stress of 100kPa, 200kPa, 400kPa, and 600kPa were applied for MgO grain content of 30%, 50%, 70% and 100% respectively. The greater MgO grain content and the less confining stress, the greater amount of expansion came out as a result. Through this, the model equation for predicting MgO expansion of minimum and maximum value was completed. In the expansion pressure experiment, MgO grain content of 30%, 50%, 70% experiments were conducted. It was proved that the higher the MgO grain content, the greater the expansion force.
URI
https://repository.hanyang.ac.kr/handle/20.500.11754/159823http://hanyang.dcollection.net/common/orgView/200000485397
Appears in Collections:
GRADUATE SCHOOL[S](대학원) > CIVIL AND ENVIRONMENTAL ENGINEERING(건설환경공학과) > Theses (Master)
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