| Summary: | 碩士 === 國立成功大學 === 土木工程學系碩博士班 === 100 === Basic oxygen furnace slag (BOF) is the by-product in the consistent steelmaking operation process, and the annual production is about 120 to 130 million tones in Taiwan. In recent years, the recycle applications of BOF are getting more and more, and the bulk of them are used for filling or roadbed materials. But using the BOF as an engineering material may cause the engineering to fail, especially when the users do not understand its characteristics enough or apply it to the engineering improperly.
In order to apply the BOF to civil engineering (especially road engineering) effectively and extensively, this study will conduct a series of tests for the BOF. And the content of tests is mainly divided into three parts. The first part is “basic physical and chemical properties” of BOF, and the projects include the particle size analysis, Atterberg limits, specific gravity and water absorptivity, dry unit weight, Mohs hardness, and PH value test; the second part is “engineering characteristics test,” including soundness, slake durability, Los Angeles abrasion, laboratory compaction, and laboratory swelling test; the third part is “swelling mitigation test,” trying to improve the swelling behavior of the BOF. And in this test there are five methods, which are water content change method, hollow improved method, sodium sulfate method, cut-back asphalt method, and mudstone mixed method. The main results are as follows:
(1)The specific gravity value of the BOF is close to 3.4, which is greater than the value of riverbed aggregates; the water absorptivity of the BOF is greater than riverbed aggregates, and the value of fine parts of the BOF is greater than its coarse parts; the unit weight of the BOF is greater than concrete, and the value of coarse parts of the BOF is greater than its fine parts; the soundness percent loss and the abrasion rate of the BOF are both slightly smaller than riverbed aggregates, and the value of fine parts of the BOF is greater than its coarse parts.
(2)In the laboratory compaction test, it can be divided into “JIS A5015 method,” “CNS11777-1D method,” and “CNS11777-1D of substitution method” with different specifications. In terms of optimum moisture content (OMC), the CNS11777-1D method is greater than the CNS11777-1D of substitution method, and the CNS11777-1D of substitution method is greater than the JIS A5015 method; and in terms of maximum dry density(rd,max), the order is reversed. Among them, the JIS A5015 method and the CNS11777-1D of substitution method are more suitable for situ.
(3)In the swelling pressure test, due to allowed swelling days (10 days to 30 days), the value of swelling pressure is different, which is between 0.786 MPa to 1.199 MPa approximately. And the estimative value of stable swelling pressure of long term (235 days) is 1.98 MPa.
(4)In the swelling mitigation test, the effect of“water content change method”and“hollow improved method”on mitigation is not good, and the effect of“sodium sulfate method,”“cut-back asphalt method”and“mudstone mixed method”on mitigation is much better. Among the methods of the latter , the effect of the “cut-back asphalt method”which volatilizes seven days and the “mudstone mixed method”which mixes 40% mudstone on mitigation is the best, and the swelling ratios both conform to the regulations of JIS A5015 (less than 1.5%).
|
|---|
