Reutilization Study on the Effect of Cooling Conditions on Co-melting of CaF2 Sludge and Bottom ash
Date Issued
2006
Date
2006
Author(s)
Hsieh, Wei-Shih
DOI
zh-TW
Abstract
The purpose of this research was to study the effect of co-melting slags produced from MSWI bottom ash and industrial calcium fluoride on pozzolanic reaction in cement-based composites, and to investigate the suitability of using slag as fine aggregate. The co-melting slag was air-cooled(AS) under room temperature, and then compared with water-cooled slag(WS). The experiments were divided into three stages：(1) Determine the lowest pouring temperature of co-melting ash and sludge at various proportions. (2) Analyze the physical and chemical characteristics of the air-cooled slag, such as chemical composition, TCLP, XRD patterns and strength activity index(SAI). (3) Incorporate the slag with the cement-based composites material as mineral admixtures to replace a fraction of the cement, and evaluate the influence of the replacement ratio on performance of the cement-based composites materials in terms of setting times, compressive strengths, (MIP), etc. Additionally, the effect of replacing fine sand in cement-based composites at various curing ages on compressive strengths and porosity were explored in order to evaluate the feasibility of replacing fine aggregate by slag.
The experimental results showed that the lowest pouring temperature was 1079℃ when the co-melting ash and sludge were in the ratio of 7：3. The molten samples were cooled at room temperature and their properties were then examined. It was observed that the air-cooled slag was more crystalline than that of water-cooled slag, and its chemical composition was close to Class C fly ash.
The test results of compressive strengths, degree of hydration, MIP and SEM indicated that the slag was a latent pozzlan and it could replace 3% to 20% cement in mortar. It was also demonstrated that the pulverized slag as mineral admixtures has the synergic effect. The air-cooled slag had not only pozzolanic activity but also crystalline structure, so it could cause higher compressive strength as compared with water-cooled slag. In addition to replacement of cement, the air-cooled slag could be used to replace the fine aggregates due to its physical properties complied with the CNS requirements. The compressive strength of the air-cooled slag was ascendant continuity with the replacement ratio of 40% and its strength was higher than that of the water-cooled slag. Corresponsively, the water-cooled slag could reach its highest strength with replacement ratio of 30%. Altogether, the air-cooled slag could be a more suitable replacement of the natural fine aggregate. As far as the waste reutilization was concerned, the air-cooled slag was more competitive regarding market mechanism. It also exhibited that the cooling conditions of the melting process could be employed as the indicator for selecting the target reutilization route.
Subjects
熔融
熔渣
攙料
細骨材
卜作嵐性質
綜效作用
melting process
slag
admixtures
aggregates
pozzolanic activity
synergic effect
Type
thesis
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