JP2004301747A - Slag stability evaluation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To evaluate accurately stability of steel slag subjected to aging treatment such as a blast furnace, converter or electric furnace slag generated in an iron mill or the like. <P>SOLUTION: In this slag stability evaluation method, the slag subjected to the aging treatment is sieved by a first sieve mesh, and the value determined, when the particles of minus sieve in the above sieving are sieved again by a second sieve mesh smaller than the first sieve mesh, by (the slag mass of the minus sieve of the second sieve mesh)/(the slag mass after the aging treatment before classification)×100% is used as 'the fine grain portion ratio (%) of the slag after the aging treatment'. Then, the slag subjected to the aging treatment is further subjected to hydration acceleration treatment, dried and sieved by the first sieve mesh, and the particles of minus sieve are sieved again by the second sieve mesh, and the value determined by (the slag mass of the minus sieve of the second sieve mesh after the hydration acceleration treatment)/(the slag mass before the hydration acceleration treatment)×100% is used as 'the fine grain portion ratio (%) of the slag after the hydration acceleration treatment'. The value determined by subtracting 'the fine grain portion ratio of the aging slag' from 'the fine grain portion ratio of the slag after the hydration acceleration treatment' is used as the slag decay rate. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for evaluating the stability of steel slag such as blast furnaces, converters, and electric furnace slag generated in steelworks.
[0002]
[Prior art]
Steel slag generated from smelting furnaces such as blast furnaces, converters, and electric furnaces at ironworks is used as a recycled material that reduces the burden on the environment from the viewpoint of resource saving and energy saving, and is used in various fields by taking advantage of its many characteristics. Have been.
[0003]
For example, the "hydraulic property" in which blast furnace slag and steelmaking slag gradually harden by reacting with water is suitable for roadbed materials, or the "hard" and "high wear resistance" of steelmaking slag. Characteristics are suitable for asphalt and concrete aggregate for roads.
[0004]
Since it is important that the slag used in these applications is stable over a long period of time, air and water are used for several months after the slag is crushed, for example, as specified in JIS A5015 “Steel slag for roads”. There is a need to perform an "aging" treatment for reacting with the compound to sufficiently stabilize it.
[0005]
Among them, steelmaking slag contains digestive substances such as free CaO and MgO and has a phenomenon of expanding for a long time. Therefore, as a method for evaluating whether slag has become sufficiently stable by aging, JIS A5015 “ “Steel slag for roads” defines “Water immersion expansion test method” as Annex 2.
[0006]
According to the method described in Annex 2, a sample whose particle size has been adjusted according to a certain particle size distribution is packed in a prescribed container (mold), and the sample is kept in 80 ° C. hot water for 6 hours and then allowed to cool. The operation is repeated once a day for 10 days for curing, the height of the mold in the mold after curing is measured, and the stability of the slag is evaluated from the expansion amount. Has been used as an important indicator.
[0007]
In addition, although the above method has a long time of 10 days for evaluating the stability of slag, as a method for more quickly evaluating the stability of a material containing a digestible substance, such as cement or refractory, a sealed pressurized container is used. A sample is placed under a high temperature and high pressure of 100 ° C. or more using an “autoclave” device including a heating device and a hydration reaction is caused in a relatively short time, and then, for example, ASTMC151-08 “Expansion of Portland cement” As described in "Test Methods", the method of measuring the length of a sample, and as described in JIS R2211 "Test method for digestibility of basic refractory bricks", the rate of decrease in compressive strength of a sample is measured. A method of measurement or, as described in Non-Patent Document 1, sieving of a treated sample and measuring the ratio of the weight under the sieve (powdering rate) to evaluate the stability of the material Some do.
[0008]
[Non-patent document 1]
Iron and Steel, 64th (1978) No. 10, P-68
[0009]
[Problems to be solved by the invention]
However, when attempting to use steel slag for a new purpose other than, for example, road use, the above-described stability evaluation method in the related art has the following problems.
[0010]
In other words, the present inventors have made these steel slags, in particular, those obtained by subjecting steel slag having a long-term expansion property to a sufficient aging treatment as described above to a solidified aggregate that is mixed with other binders and solidified. I have been conducting research and development to see if it can be used. Here, in order to estimate the long-term stability of a solidified body using steelmaking slag subjected to various aging treatments as aggregate, the stability promotion test of the solidified body itself was performed to examine the destruction state of the solidified body, and at the same time, The stability of steelmaking slag, which is the aggregate used in the above, was evaluated using the method described above, and a study was conducted to find conditions for stabilization of steelmaking slag applicable to the solidified body.
[0011]
Here, in the "water immersion expansion test method" described in JIS A5015 "iron and steel slag for roads", it is possible to evaluate the average expandability of a mass (group) of steelmaking slag of a certain volume in a mold. Since the fracture accompanying the individual expansion of the slag grains, which is one of the constituent elements, which can lead to the fracture of the solidified body cannot be measured, a phenomenon that the solidified body is broken even if the expansion rate is small is seen, It turned out that the stability of the slag could not be evaluated accurately.
[0012]
Also, a method for measuring the length of a sample as described in ASTM C151-08 “Expansion test method for Portland cement” or a sample described in JIS R2211 “Test method for digestibility of basic refractory brick” Although the expansion behavior of a molded article can be evaluated by a method for measuring the rate of decrease in the compressive strength of the slag, it is difficult to evaluate the stability of each slag particle.
[0013]
Further, in the method of measuring the powdering rate described in Non-Patent Document 1, the measured value is small or the dispersion is large only with the powder component generated as a result of hydration swelling, and the solidified body is broken. It is difficult to discriminate slag, and it is also difficult to evaluate the stability of individual slag grains, as described in the article, "There is no suitable method for indicating the disintegration of slag."
[0014]
An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a method for more accurately evaluating the stability of an aged steel slag.
[0015]
That is, it is an object of the present invention to accurately grasp the existence probability of individual slag grains that have not yet been collapsed and remain in the slag stabilized by the aging treatment or the like.
[0016]
[Means for Solving the Problems]
As described above, the present inventors investigated the state of destruction of the solidified body in a stability promotion test of the solidified body using various aging-treated steelmaking slags as an aggregate, and at the same time, used the steelmaking slag used for these aggregates. The stability (disintegration) of slag was also measured by various methods, and the analysis and examination were repeated as to whether a quantitative correlation was found between the two. As a result, the above-mentioned problems were solved by the following invention. Knowledge was obtained.
(1) When the slag subjected to the aging treatment is sieved with a first sieve, and the slag under the sieve is further sieved with a second sieve smaller than the first sieve,
{(Slag mass under the second sieve) / (Aging slag mass before classification) × 100 (%)}
Is the ratio of fine particles of slag after aging treatment (%),
Next, the aging-treated slag is further subjected to a hydration accelerating treatment, and the dried slag is sieved with the first sieve and further sieved under the second sieve with the second sieve.
{(Slag mass under the second sieve after hydration acceleration treatment) / (Slag mass before hydration acceleration treatment) × 100} (%)
Is defined as “fine-grain fraction (%) of slag after hydration acceleration treatment”
"Fine particle ratio of slag after hydration acceleration treatment"-"Fine particle ratio of aging slag"
A slag decay rate, and a method for evaluating slag stability.
(2) The hydration accelerating treatment is a treatment described in JIS A5015 “Steel slag for road” “Water swelling test method” or ASTMC151-08 “Portland cement expansion test method”. (1) The slag stability evaluation method described in (1).
(3) The method for evaluating slag stability according to (1) or (2), wherein the first sieve is coarser than the second sieve by one or two stages in accordance with JIS Z8801-1. .
(4) The method for evaluating slag stability according to any one of (1) to (3), wherein the first sieve is 9.5 mm, and the second sieve is 8 mm. .
(5) Any one of the above (1) to (4), wherein the aging treatment is a treatment in which the aging treatment is left for at least one month in the atmosphere or for six hours or more under normal pressure or pressurized steam. 2. The method for evaluating slag stability according to claim 1.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
[0018]
The present inventors have investigated the stability of various slags subjected to aging treatment, and as a result, conventionally, to evaluate the slag expandability reported in the "water immersion expansion test" and "autoclave expansion test" According to the results, it is clear that the slag promotes the hydration reaction, and it is clear that some of the digestible slag granules expand and break with hydration. It was known that the more the expansion coefficient was reduced, the more it could be evaluated.
[0019]
However, in order to estimate the long-term stability of the solidified body using steelmaking slag that has been subjected to various aging treatments as aggregate, the stability promotion test of the solidified body itself was conducted to examine the fracture state of the solidified body, and at the same time, Regarding the steelmaking slag that is the aggregate used, the expansion rate was measured by measuring the above-mentioned expansion rate and examining the correlation between the two to find out the conditions of steelmaking slag applicable to the solidified body. As mentioned earlier, the average expansion behavior of a certain volume of slag as a lump (group) is evaluated. Even if the expansion rate is actually small, several collapsed slags are contained in the slag. It was presumed that this would lead to the destruction of the solidified body.
[0020]
Therefore, next, not the expansion coefficient, sieved the slag that has been aged,
{(Slag mass under sieve after aging treatment) / (Slag mass after aging treatment) × 100 (%)}
Is determined in advance as the fine-grain fraction (%) of the slag after the aging treatment. Next, a hydration acceleration test is further performed without classifying the entire slag that has been subjected to the aging treatment first. Sieve with the same roughness as the sieve,
{(Slag mass under sieve after hydration acceleration treatment) / (Slag mass before hydration acceleration treatment) × 100 (%)}
Is determined as the fine grain fraction (%) of the slag after the hydration accelerating treatment,
This “Ratio of fine particles of slag after hydration acceleration treatment” − “Ratio of fine particles of slag after aging treatment” (%)
The correlation between the slag decay rate and the state of destruction of the solidified body was also investigated, but conversely, with this method, the slag decay rate greatly fluctuated even after various aging treatments, and the result was that it was also difficult to evaluate properly It became.
[0021]
However, according to the above-mentioned method, it should have been possible to measure the individual slag particles that have clearly collapsed, and in order to determine the cause of the large variation in the slag collapse rate, the present inventors have conducted various studies. As a result, the following knowledge was obtained as a method for accurately evaluating the stability of slag.
[0022]
That is, the slag after the hydration promoting treatment was sieved and the slag particles under the sieving were observed in detail. It was found that relatively large slag particles that seem to be absent were mixed.
[0023]
In order to determine an accurate slag decay rate, it is necessary to remove relatively large slag particles that are apparently not collapsed and that are contained under the sieve. This is the same problem when calculating not only the fine grain fraction including the truly disintegrated slag grains after the hydration promoting treatment but also the slag fine grain fraction after the aging treatment.
Therefore, the slag that has undergone the aging treatment is sieved with a first sieve, and further below the sieve is sieved with a second sieve smaller than the first sieve.
｛(Mass of slag under the second sieve under sieving) / (mass of slag after aging treatment before classification) × 100 (%)
Is determined in advance as the fine-grain fraction (%) of the slag after the aging treatment, and then the dried slag after the hydration promoting treatment is the same as the sieve for which the fine-grain fraction of the slag after the aging treatment was determined. Sieving with a first sieve of roughness and further sieving under this sieve with a second sieve smaller than the first sieve results in the apparently complete removal of undisintegrated slag In this way, only slag that has collapsed due to hydration acceleration treatment can be measured,
｛(Mass of slag under the second sieve after hydration promoting treatment) / (mass of slag before hydration promoting treatment × 100)
Is defined as “fine-grain fraction (%) of slag after hydration acceleration treatment”
"Fine particle ratio of slag after hydration acceleration treatment"-"Fine particle ratio of aging slag"
By setting the true slag decay rate as described above, this decay rate is reduced if the aging treatment of the original slag is sufficient, and furthermore, this decay rate is closely related to the stability (destruction situation) of the solidified body. And so on.
[0024]
FIG. 1 is a diagram showing the principle of the present invention. In the present invention, the slag that has been subjected to aging treatment in advance is a measurement target. As the aging treatment, after leaving in the air for at least one month, steam aging was performed at 180 ° C. for 6 hours as needed.
[0025]
In order to determine the fine particle fraction of the slag after the aging treatment, a certain amount of the slag subjected to the aging treatment is classified with a 9.5 mm sieve in accordance with JIS Z8801-1, and the slag under the sieve is further classified according to JIS Z8801-. Classification is performed using 8 mm which is another smaller sieve according to 1 to remove undisintegrated comparatively large slag particles (W2) and obtain fine particles of slag after aging treatment under the sieve ( W1). Here, ｛(mass of slag under the second sieve under sieving = W1) / (mass of slag after aging treatment before classification = W0) × 100 (%)
Is calculated as the “slag fine particle fraction (%) after aging treatment”.
[0026]
Next, the entire slag that has been aged first is not classified, but is further immersed in warm water at 80 ° C. (6 hours / day × 10 days) or further subjected to water treatment using an autoclave (180 ° C. (about 20 atm) × 6 hours). After performing the sum accelerating treatment and drying, it is similarly classified with a 9.5 mm sieve according to JIS Z8801-1, and another lower sieve is further below the sieve according to JIS Z8801-1. Classifying using 8 mm, removing relatively large unsoiled slag particles (W2 ′), obtaining fine particles of slag after aging treatment under a sieve (W1 ′),
{Slag mass under the second sieve after hydration promotion treatment = W1 '} / (slag mass before hydration promotion treatment = W0) x 100 (%)
Is defined as “fine-grain fraction (%) of slag after hydration acceleration treatment”.
[0027]
From this figure, the true slag collapse rate is determined as follows.
[0028]
True slag decay rate = "fine-grain fraction (%) of slag after hydration promoting treatment"-"fine-grain fraction (%) of slag after aging treatment"
Conventionally, when evaluating the slag disintegration rate, the slag content (sum of W1 and W2) under the first sieve of the aging slag and the slag content under the first sieve after the hydration promoting treatment, that is, water The difference between the sum (W1 '+ W2') of the slag collapsed by the sum promotion treatment and the undegraded slag was regarded as the collapse rate. Even if the preliminary classification is performed under certain conditions, it is easy to assume that the slags W2 and W2 ', which should have been sieved out, vary during processing, and this is the variation in measured values. The present inventors have found that
[0029]
Here, the sieve used for classification is generally specified in JIS Z 8801-1 as described above in Japan. Furthermore, it is a feature of the present invention that the final classification is performed using a sieve smaller than the sieve used in the pre-classification treatment. For this, a sieve smaller by about 1 to 2 steps specified in JIS Z 8801-1 is used. It is preferable to use slag having a smaller diameter for measurement of slag having a smaller diameter.
[0030]
As slag hydration accelerating treatment, JIS A5015 “Steel for road slag”, which has many achievements, “water immersion expansion test method” (10 days in hot water at 80 ° C.) and ASTM C151-08 which can be treated in a short time. In general, a method according to the “Portland cement expansion test method” is used. In the latter case, treatment at 180 ° C. for 3 to 6 hours can provide sufficient data for evaluation.
[0031]
Since the purpose of the present invention is to evaluate the slag decay rate after performing the aging treatment, after aging treatment, to classify undisintegrated slag, it is not possible to remove fine particles with the first sieve. Required.
[0032]
In addition, as the aging treatment, it is preferable that the digestion component is left at room temperature for one month or more, or under normal pressure or pressurized steam for 6 hours or more so that the digestion component undergoes a hydration reaction. The effect of the present invention can be obtained without particular limitation on the upper limit of pressurization. However, in order to efficiently and economically obtain the hydration accelerating effect of MgO, which has a slow hydration rate, 1 to 10 atmospheres is required. Processing is preferred.
[0033]
Furthermore, the amount of slag used for evaluation is not particularly limited, but the more the aging treatment is performed for stabilizing the slag, the more the slag collapse rate decreases, so in order to improve the accuracy of the measured value, It is better to use at least 5 kg or more.
[0034]
In addition, some slags have a smooth surface in the shape of a rock, while others have a rough surface in the form of sandstone.Especially in the case of the latter, powder is generated. The measurement accuracy is improved by removing the adhered powder.
[0035]
【Example】
(Example of the present invention)
FIG. 2 shows that 5 kg of a steelmaking slag (particle size range: 100 mm or less) stabilized by an aging treatment left at room temperature for at least one month is sieved to a nominal size of 9.5 mm specified by JIS Z 8801-1 (first type). And classified under a sieve having a nominal size of 8 mm (second sieve) specified in JIS Z8801-1.
｛(Mass of slag under the second sieve under sieving) / (mass of slag after aging treatment before classification) × 100 (%)
Is determined in advance as the fine-grain fraction of the slag after the aging treatment, and then 5 kg of the aging slag (particle size range of 100 mm or less) is subjected to the “water immersion expansion test method” of JIS A5015 “Road steel slag”. After being immersed in warm water of 80 ° C. for 10 days to perform hydration accelerating treatment, and then dried at 110 ° C. for 24 hours, it is specified by JIS Z 8801-1 by the method shown in FIG. Classifying using a sieve with a nominal size of 9.5 mm, and further classifying under the sieve with a sieve with a nominal size of 8 mm specified in JIS Z8801-1,
{(Slag mass under the second sieve after hydration acceleration treatment) / (Slag mass before hydration acceleration treatment) × 100 (%)}
Is determined as the fine grain fraction of the slag after the hydration promoting treatment, (the fine grain fraction of the slag after the hydration promoting treatment) − (the fine grain fraction of the slag after the aging treatment) (%).
The solid slag (diameter 100 mm * height 200 mm) obtained by mixing the true slag collapse rate obtained as Similarly, it is a graph showing a correlation with a destruction rate of a solidified body when accelerated evaluation (immersion in warm water of 80 ° C. for 4 weeks) for confirming stability. In addition, the destruction rate of the solidified body was determined by the number of samples collapsed by the accelerated evaluation / the number of samples subjected to the evaluation.
[0036]
From this figure, it can be seen that when the true decay rate of the slag according to the present invention exceeds about 3%, the sample of the solidified body using the slag as an aggregate also breaks down. The slag was found to be suitable as a solidified aggregate.
(Comparative example)
FIG. 3 shows that 5 kg of a steelmaking slag (particle size range: 100 mm or less) stabilized by an aging treatment that is left at room temperature for at least one month is sieved with a nominal size of 9.5 mm specified by JIS Z 8801-1 (first type). Classification using only the sieve) and {(mass of slag under the first sieve) / (mass of slag after aging treatment before classification) × 100 (%)}
Is determined in advance as the fine-grain fraction (%) of the slag after the aging treatment. Then, 5 kg of the slag (the particle size range of 100 mm or less) after the aging treatment is subjected to the “water immersion expansion test” of JIS A5015 “Steel slag for roads”. The slag is immersed in warm water at 80 ° C. for 10 days according to the “method”, subjected to a hydration promoting treatment, dried at 110 ° C. for 24 hours, and then JIS Z8801- according to the method shown in FIG. Classifying using only the sieve with a nominal size of 9.5 mm (first sieve) specified in 1,
{(Slag mass under the first sieve after hydration acceleration treatment) / (Slag mass before hydration acceleration treatment) × 100 (%)}
Is determined as the fine-grain fraction of the slag after the hydration acceleration treatment,
(Ratio of fine particles in slag after hydration acceleration treatment)-(Ratio of fine particles in slag after aging treatment) (%)
The solidified material (diameter 100 mm * height 200 mm) obtained by using the same slag as the aggregate and the blast furnace slag fine powder as the main binder, and then solidifying 7) is a graph showing the correlation with the destruction rate of the solidified body when accelerated evaluation (immersion in hot water at 80 ° C. for 4 weeks) for confirming the stability as in the case of slag. The fracture rate of the solidified body was determined by the same method as in the present invention.
[0037]
As can be seen from this figure, the slag decay rate by the conventional method is, as described above, because some undisintegrated slag particles are mixed. The solidified body using crushed or not broken, and slag conditions suitable for a stable solidified body could not be found.
[0038]
【The invention's effect】
According to the present invention, steel slag, especially steelmaking slag that has a digestible component and has the property of expanding over a long period of time, when aging treatment is to be used for new applications other than road use, such as solidified bodies, The stability of the applied and stabilized slag can be accurately evaluated.
[Brief description of the drawings]
FIG. 1 illustrates the principle of the present invention. (W0 to W2 indicate slag mass after aging treatment, and W1 ′ and W2 ′ indicate slag mass after hydration promotion treatment.)
FIG. 2 shows the relationship between the slag collapse rate according to the present invention and the destruction rate of a solidified body using the slag as an aggregate.
FIG. 3 shows the relationship between the slag collapse rate according to the prior art and the destruction rate of a solidified body using the slag as an aggregate.

Claims (5)

The slag that has undergone the aging treatment is sieved with a first sieve, and the slag under this sieve is sieved with a second sieve smaller than the first sieve (the slag under the second sieve). Mass) / (mass of slag after aging treatment before classification) × 100 (%) is defined as “fine slag fine particle fraction (%)”,
Next, the aging-treated slag is further subjected to a hydration accelerating treatment, and the dried slag is sieved with the first sieve and further sieved under the second sieve with the second sieve.
{(Slag mass under the second sieve after hydration acceleration treatment) / (Slag mass before hydration acceleration treatment) × 100} (%)
Is defined as “fine-grain fraction (%) of slag after hydration acceleration treatment”
A method for evaluating slag stability, wherein the ratio of fine particles of slag after hydration acceleration treatment-the ratio of fine particles of aging slag is a slag collapse rate. The hydration accelerating treatment is a treatment described in JIS A5015 "Steel slag for roads" "Water immersion expansion test method" or ASTM C151-08 "Portland cement expansion test method". Slag stability evaluation method. The slag stability evaluation method according to claim 1 or 2, wherein the first sieve is coarser by one or two stages in accordance with JIS Z8801-1 than the second sieve. The slag stability evaluation method according to any one of claims 1 to 3, wherein the first sieve is 9.5 mm and the second sieve is 8 mm. The aging treatment is a treatment that is left at least for one month or more in the atmosphere or for six hours or more under normal pressure or pressurized steam. Slag stability evaluation method.

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