JP2004301694A - 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: This slag stability evaluation method has a characteristic wherein the plus-sieve slag from which a fine grain portion is removed by a first sieve mesh is further subjected to hydration acceleration treatment after the aging treatment, dried and sieved by a second sieve mesh smaller than the first sieve mesh, and the value determined by (the slag mass of the minus sieve of the second sieve mesh)/(the slag mass of the first plus sieve before the hydration acceleration treatment)×100% 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 a blast furnace, a converter, and an electric furnace slag generated in an ironworks.
[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, "hydraulic", in which blast furnace slag and steelmaking slag gradually harden by reacting with water, is suitable for roadbed materials, or the "hard" and "wear-resistant" properties of steelmaking slag Is 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]
However, in the “water immersion expansion test method” described in JIS A5015 “iron and steel slag for roads”, it is possible to evaluate the average expansibility as a mass (group) of a certain volume of steelmaking slag in a mold. Since it is not possible to measure the destruction of the slag particles, which are one of the constituent elements, which would cause the destruction of the solidified product, it is impossible to measure the destruction. It was found that the stability of the slag could not be evaluated.
[0012]
Also, a method for measuring the length of a sample as described in ASTM C151-08 “Testing method for expansion of Portland cement”, or a sample described in JIS R2211 “Testing 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) After the aging treatment, the slag on the sieve from which fine particles have been removed by the first sieve is further subjected to a hydration accelerating treatment, and the dried slag is smaller than the first sieve. Sieving with the second sieve, (slag mass under the second sieve) / (mass of slag on the first sieve before the hydration acceleration treatment) x 100 (%) slag collapse A method for evaluating slag stability, characterized in that the slag is a ratio.
(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) The method for evaluating slag stability according to any one of (1) to (4), wherein the slag from which coarse particles of 50 mm or more are also removed is subjected to a hydration promoting treatment.
(6) Any of the above (1) to (5), wherein the aging treatment is a treatment in which the aging treatment is left at least for one month or more 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]
Then, instead of the expansion rate, the slag after the same hydration accelerating treatment is sieved, and the disintegration rate (powder rate) is measured from the weight under the sieve, and the correlation with the destruction state of the solidified body is also determined. According to this method, on the contrary, even if various aging treatments were performed, the slag collapse rate greatly fluctuated, and as a result, it was difficult to properly evaluate the slag.
[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 investigate the cause of the large variation in the slag collapse rate, the present inventors conducted further various studies. As a result, the following findings were obtained as a method for accurately evaluating the stability of slag.
[0022]
That is, after the slag on the sieve classified by the first sieve was subjected to the hydration promoting treatment, the slag was sieved by the same first sieve, and the slag particles under the sieve were observed in detail. It was found that relatively large slag particles which seemed to have not collapsed were mixed in the slag or powdery slag which had collapsed by the treatment.
[0023]
The reason for this is that for the sake of stability evaluation, these slags are removed by a classification treatment to a particle size larger than that required in advance of the hydration accelerating treatment. It is considered that some fine slag was inevitably left on the sieve, and the slag fell under the sieve during the classification treatment after the promotion of hydration.
[0024]
Then, when the slag after the hydration accelerating treatment is sieved with the second sieve smaller than the first sieve, the undisintegrated slag is clearly and almost completely removed, and as a result, the slag is disintegrated by the hydration accelerating treatment. Can be measured, and by using this true decay rate, the decay rate can be reduced if the aging treatment of the original slag is sufficient. The situation of destruction).
[0025]
FIG. 1 is a diagram showing the principle of the present invention. Here, as an example, in order to measure a slag of 10 mm or more and 25 mm or less that has been aged in advance, the nominal dimensions (length of one side of a sieve) specified in JIS Z8801-1 are 22.4 mm and 9.5 mm. Classify the slag in advance using a sieve. 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.
[0026]
The slag is immersed in hot water at 80 ° C. (6 hours / day × 10 days) or subjected to a hydration promoting treatment using an autoclave (180 ° C. (about 20 atm) × 6 hours) and dried, and then JIS Z8801. The slag after the above-mentioned hydration accelerating treatment is classified by using 8 mm which is one step smaller than the 9.5 mm sieve according to -1. The figure also shows an example in which the slag under the one-stage smaller sieve is further sieved with a 2 mm sieve to separate the slag into fragmentary slag and powdery slag (W2, W1).
[0027]
From this figure, it is obvious that according to the present invention, the true decay rate is represented by the sum of the powder content W1 and the fragmentary slag amount W2 with respect to the original slag amount W0.
[0028]
However, conventionally, in addition to the powder content (W1) and the shard-like content (W2), the sum of undisintegrated slag between 8 mm and 9.5 mm was regarded as the collapse rate. Even if the preliminary classification is performed under a certain condition, if the classification is performed by using a 9.5 mm sieve, it is necessary to reduce the size from 8 mm to 9.5 mm, which should be sieved. The present inventors have found that since the slag between the samples varies during the classification process, a part of the slag can easily be left on the sieve, which results in a variation in measured values.
[0029]
In addition, as reported in some cases, the disintegration rate was referred to as the powdering rate, in some cases, the disintegration rate was regarded as the disintegration rate using only the powder component W1 generated by the hydration treatment. In other words, the evaluation is much smaller than the true collapse rate.
[0030]
Here, the sieve used for classification is generally specified in JIS Z 8801-1 as described above in Japan. Further, the feature of the present invention is that 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 stages specified in JIS Z 8801-1 is used. It is preferable that the measurement of the slag having a small diameter is sufficient with the sieve below one stage. Prior classification is generally performed, for example, with a large classifier, but after the hydration acceleration treatment, the amount of collapsed slag is small, and it is common to use a low-tap tester or the like to increase the accuracy. It is preferable from the viewpoint of measurement accuracy that the slag after the hydration accelerating treatment is sufficiently dried and classified for at least 3 minutes or more.
[0031]
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.
[0032]
Since the purpose of the present invention is to evaluate the slag collapse rate after performing the aging treatment, after aging treatment, to classify the undisintegrated slag, it is not possible to remove fine particles with the second sieve. Required.
[0033]
Here, if the original slag has a particle size of 50 mm or less, preferably 25 mm or less, there is no need to classify coarse particles in advance. On the other hand, if the particle size of the slag is more than 50 mm, preferably more than 25 mm, it is preferable to remove the coarse particles and use the slag for the hydration promoting treatment in order to avoid the incorporation of the ingot.
[0034]
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.
[0035]
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.
[0036]
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 better when the attached powder is removed.
[0037]
【Example】
(Example of the present invention)
FIG. 2 shows a steelmaking slag stabilized by an aging treatment left at room temperature for at least one month and sieved at nominal sizes 22.4 mm and 9.5 mm specified in JIS Z 8801-1 (particle size range: 10 to 10 mm). 25 mm) 5 kg was immersed in hot water at 80 ° C. for 10 days in accordance with JIS A5015 “Steel slag for roads” “Water swelling test method”, subjected to hydration accelerating treatment, and then dried at 110 ° C. for 24 hours. After sieving, classified by a sieve having a nominal size of 8 mm specified by JIS Z 8801-1 by a method as shown in FIG. 1, and (slag mass under a sieve of 8 mm) / (before hydration acceleration treatment) (10-25 mm slag mass) × 100%, the true decay rate, and solidification using the same slag as an aggregate and other blast furnace slag fine powder mixed as the main binder (Diameter 100 mm * height 200 mm), is a graph showing a correlation between accelerated evaluation (4 weeks immersion in 80 ° C. warm water) was during solidification of the rate of destruction for confirmation Likewise stability and slag. 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.
[0038]
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 1)
FIG. 3 shows a steelmaking slag stabilized by an aging treatment left at room temperature for at least one month and sieved at nominal sizes 22.4 mm and 9.5 mm specified in JIS Z 8801-1 (particle size range: 10 to 10 mm). 25 mm) in a container (mold) specified in JIS A5015 “Steel slag for roads” in “Method of water immersion expansion test” as annex 2 in Annex 2, and filled with hot water at 80 ° C. After holding for 6 hours, the operation of allowing to cool is repeated once a day for 10 days for curing, and the expansion rate obtained by measuring the height of the sample in the mold after curing and the same slag as an aggregate. In addition, a blast furnace slag fine powder was mixed as a main binder and the solidified material (diameter 100 mm * height 200 mm) was subjected to accelerated evaluation for stability confirmation in the same manner as slag (4 weeks in hot water at 80 ° C) Is a graph showing the correlation between destruction rate of the solidified body when the pickles). The destruction rate of the solidified body was determined by the same method as in the present invention.
[0039]
From this figure, it can be seen that the solidified body using the slag is broken or not broken when the expansion ratio is 0.3% or more, even if the expansion coefficient, which is a conventional evaluation method, is used. Slag conditions suitable for slag could not be found.
(Comparative Example 2)
FIG. 4 shows a steelmaking slag stabilized by an aging treatment left at room temperature for at least one month and sieved at nominal sizes 22.4 mm and 9.5 mm specified in JIS Z 8801-1 (particle size range: 10 to 10 mm). 25 mm) 5 kg was immersed in hot water at 80 ° C. for 10 days in accordance with JIS A5015 “Steel slag for roads” “Water swelling test method”, subjected to hydration accelerating treatment, and then dried at 110 ° C. for 24 hours. (Slag mass under a 9.5 mm sieve) / (hydration promotion) when classified with a sieve having a nominal size of 9.5 mm specified in JIS Z 8801-1 as used in the pre-classification process. The so-called decay rate, which was determined by the (slag mass of 10 to 25 mm before treatment) x 100%, and the slag as the aggregate, and the blast furnace slag fine powder was mainly combined Of the solidified body (diameter 100 mm * height 200 mm), which was mixed and hardened, as in the case of slag, was subjected to an accelerated evaluation for stability confirmation (immersed in 80 ° C warm water for 4 weeks). It is a graph showing the correlation. The destruction rate of the solidified body was determined by the same method as in the present invention.
[0040]
From this figure, the slag decay rate according to the conventional method also shows that the undecayed slag particles are partially mixed as described above, so that when the decay rate becomes 2% or more, Comparative Example 1 is obtained. Similarly, the solidified body using the slag was broken or did not break, and it was not possible to find slag conditions suitable for a stable solidified body.
[0041]
【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.
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 expansion rate of slag according to the prior art and the destruction rate of a solidified body using the slag as an aggregate.
FIG. 4 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 (6)

After the aging treatment, the slag on the sieve from which fine particles have been removed by the first sieve is further subjected to a hydration accelerating treatment, and the dried slag is subjected to a second slag smaller than the first sieve. Sieving with a sieve, and (slag mass under the second sieve under the second sieve) / (mass of slag on the first sieve before the hydration acceleration treatment) x 100 (%) is defined as the slag collapse rate. A method for evaluating slag stability, characterized in that: 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 method for evaluating slag stability according to any one of claims 1 to 4, wherein the slag from which coarse particles of 50 mm or more have been removed is subjected to a hydration promoting treatment. 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, according to any one of claims 1 to 5, Slag stability evaluation method.

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