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|Other Titles: ||Preparation of cement admixture with MSWI ash by mechanical milling technology for Pb stabilization and cementitious modification|
|Authors: ||陳政綱;Chen, Cheng-Gang|
|Keywords: ||焚化飛灰;機械研磨;氯離子穩定;無機膠體;MSWI fly ash;Mechanical milling;Stabilize chloride ion;inorganic gel|
|Issue Date: ||2013-04-13 12:02:58 (UTC+8)|
實驗以水、不同濃度之磷酸(0.002 M、0.2 M PO4
多，形成的漿體較緻密，以NMR 分析後發現C-S-H 聚合度提升，抗壓強度與市
當以0.2 M 磷酸研磨液進行研磨時，研磨時間小於1 小時即產生許多磷酸鈣
結晶 (HAp, TCP, TTCP)，然而可解離的磷酸鈣化合物及過多的PO4
強度的效果，導致漿體抗壓強度較市售水泥漿體為低。以0.002 M 磷酸進行時，
所產生的卜作嵐反應造成7 天與28 天抗壓強度仍大於OPC。
以不同偏高嶺土調配比進行研磨活化時(1 M 氫氧化鈉、24 小時)，發現鹼液
達到穩定重金屬的效果。然而當鹼液濃度提高時(5 M 氫氧化鈉)，則變成由活化膠
利用5 M 氫氧化鈉搭配煆燒淨水污泥進行研磨活化，水萃反應灰調配量較高
salt 結構，因而有顯著的化學穩定性能，在7 天齡期中水泥漿體即有相當優良的
This study used mechanical milling to change physical and chemical properties of
municipal solid waste incinerator (MSWI) fly ash. The mobility of heavy metals would be
reduced by mechanical milling and the amount of inorganic gelwould be also promoted by
alkali activation of the MSWI fly ash. After mechanical milling and alkali activation
processes, the MSWI fly ash can achieve the aim of detoxification and recovery, and can
be a good substitute of Type I ordinary Portland cement (OPC).
The crystal structure of MSWI fly ash was destroyed and became the amorphous
phase after milling 96 h. At the same time, the leaching concentration of the heavy metals
of milled fly ash could be decreased below the detection limit. The paste which partial
substituted the OPC by the milled fly ash would increase the amount of gel pores and
middle-size pores, and led the paste to become denser than OPC paste. The results of the
nuclear magnetic resonance Spectrometer (NMR) test indicated that the milled fly ash
can not only increase the amount of C-S-H gel which is caused by the higher hydration
reaction, but also can accelerate the pozzolanic reaction. Based on these results, the
compressive strength of the paste could rise up in all of the curing times.
By 0.2 M PO4
3- of milling solution and 1 h milling time, the calcium phosphate of
hydroxyapatite (HAp), tricalcium phosphate (TCP) and tetracalcium phosphate (TTCP)
would be produced. However, the dissolution of calcium phosphate compounds and
3- remained in the milled ash, which made the calcium hydroxide of paste be
consumed. This result indicate that the milled fly ash by PO4
3- caused the negative impact
of the compressive strength of the milled fly ash paste greater than the positive impact,
and led the compressive strength lower than the OPC paste.
The milled fly ash with 0.002 M PO4
3- would produce a lot of TTCP when it partial
substituted OPC paste, which the TTCP would react with water to produce HAp and
calcium hydroxide. In addition, the effect of the pozzolanic reaction premature generated
by 96 h of milling time still appears and the compressive strength of the milled fly ash
paste after 7 days and 28 days of curing also higher than the OPC paste.
The effect of metakaolin and washed fly ash on a different mixing ratio by
mechanical milling activation (1 M NaOH , 24 h) was evaluated. The results show 1 M
NaOH of milling solution was lack of alkali concentration, thus it could not dissolute the
silicate of metakaolin. The compounds produced by metakaolin after mechanical milling
activation could conduct an ions exchange of heavy metal and achieve the stabilization of
heavy metal. When the alkali concentration increased to 5 M, heavy metal would bond
with the activated gel. Due to the bonding strength is weak, so the leaching concentration
of heavy metal was slightly increased. In addition, the high concentration of sodium
hydroxide would cause significant negative influence on the hydration reaction.
The milling activation was conducted in 5M of NaOH with the water treatment plant
sludge after calcination. The results show that the stabilized chloride crystallization would
be increased when the amount of the extracted fly ash was increased. Nevertheless, when
the amount of the extracted fly ash was decreased, the type of the bound with chloride ion
was the physical stability mechanism, which would lead to poor stability of the paste.
From above statement, the milled activated fly ash would form a gel of weak structure for
binding with chloride ion and was not conducive to stabilize chloride for the paste in the
early curing time. When the water was the milling solution, it would generate many
similar Friedel’s salt structure which caused the effect of observably chemical stability.
The excellent of the effect of stabilize chloride ion for the paste would be appeared after 7
days of curing. The stabilization and reaction mechanism of chloride ion in the inorganic
gel is difference with traditional cement evidently.
|Appears in Collections:||[水資源及環境工程學系暨研究所] 學位論文|
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