JP4274834B2 - Slag stability evaluation method - Google Patents

Description

[0001]
BACKGROUND 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 steelworks is used in various fields as a recycled material that reduces environmental burden from the viewpoint of resource saving and energy saving. Has been.
[0003]
For example, “hydraulicity” in which blast furnace slag and steelmaking slag gradually harden by reacting with water is suitable for roadbed materials, or the characteristics of “hard” and “abrasion resistance” of steelmaking slag. Is suitable for road asphalt and concrete aggregate.
[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 defined in JIS A5015 “Steel Slag for Roads”. It is necessary to sufficiently stabilize by performing an “aging” treatment for reacting with azobenzene.
[0005]
Among them, steelmaking slag contains digestible substances such as free CaO and MgO and has a phenomenon of expanding over a long period of time. Therefore, as a method for evaluating whether slag has been sufficiently stabilized by aging, JIS A5015 “ The “water immersion expansion test method” is defined as Annex 2 in “Steel Slag for Roads”.
[0006]
In the method described in Annex 2, a sample whose particle size is adjusted according to a certain particle size distribution is packed into a specified container (mold) and held in hot water at 80 ° C. for 6 hours, and then allowed to cool. The operation is repeated once a day for 10 days, the height of the sample in the mold after curing is measured, and the stability of the slag is evaluated from the amount of expansion. Has been used as a good indicator.
[0007]
In the above method, the slag stability evaluation has a long time of 10 days. For example, as a method for more quickly evaluating the stability of materials containing digestible substances such as cement and refractory, a sealed pressurized container is used. A sample is placed under a high temperature and high pressure of 100 ° C. or higher using an “autoclave” apparatus consisting of a heating device and a hydration reaction in a relatively short time. For example, ASTM C151-08 “Expanding Portland cement” The method of measuring the length of the sample as described in "Test method" and the rate of decrease in the compressive strength of the sample as described in JIS R2211 "Test method of digestibility of basic refractory bricks" Method of measurement, or as described in Non-Patent Document 1, sieving the treated sample and measuring the weight ratio (pulverization rate) under the sieve to evaluate the stability of the material What to do is also known.
[0008]
[Non-Patent Document 1]
Iron and steel, 64th (1978) No. 10, P-68
[0009]
[Problems to be solved by the invention]
However, when steel slag is to be used for new uses other than for roads, for example, the above-described conventional stability evaluation method has the following problems.
[0010]
In other words, the present inventors used these steel slags, especially steelmaking slags having long-term expansibility, which have been subjected to sufficient aging treatment as described above, together with other binders to solidify aggregates to be solidified. Research and development has been carried out to see if it can be used. Here, in order to estimate the long-term stability of the solidified body using steelmaking slag that has been subjected to various aging treatments, the stability of the solidified body itself is investigated by examining the stability of the solidified body. The steelmaking slag, which is the aggregate used in the above, was evaluated for its stability using the above-mentioned method, and a study was conducted to find out the conditions for stabilizing the steelmaking slag that can be applied to the solidified body.
[0011]
However, in the “water immersion expansion test method” described in JIS A5015 “steel slag for roads”, the average expansibility as a mass (group) of steel slag of a certain volume in the mold can be evaluated. Since the failure due to individual expansion of slag grains, which is one of the components that causes the solidified body to break, cannot be measured, a phenomenon that the solidified body is broken even when the expansion coefficient is small is observed. It was revealed that the stability of slag could not be evaluated.
[0012]
Also, a method for measuring the length of a sample as described in ASTM C151-08 “Method for testing the expansion of Portland cement”, or a sample described in JIS R2211 “Test method for digestibility of basic refractory bricks” Although the method of measuring the rate of decrease in the compressive strength can evaluate the expansion behavior of the molded body, it is difficult to evaluate the stability of individual slag grains.
[0013]
Further, in the method for measuring the pulverization rate described in Non-Patent Document 1, the measured value is small or the variation is large only with the powder produced as a result of hydration expansion, and the solidified body is destroyed. Slag discrimination is difficult, and it is difficult to evaluate the stability of individual slag grains, as it is stated in the paper that “There is no suitable method for indicating the slag disintegration”.
[0014]
An object of the present invention is to provide a method for more accurately evaluating the stability of steel slag that has been subjected to the aging treatment by solving the problems of the prior art.
[0015]
That is, it is an object of the present invention to accurately grasp the existence probability of individual slag grains that remain in the slag stabilized by aging treatment or the like and are still uncollapsed.
[0016]
[Means for Solving the Problems]
As described above, the present inventors investigated the fracture state of the solidified body in the stability promotion test of the solidified body using steelmaking slag subjected to various aging treatments as an aggregate, and at the same time, steelmaking used in these aggregates. The stability (disintegration) of slag was also measured by various methods, and as a result of repeated analysis and examination of whether a quantitative correlation could be found between them, the above problems were solved by the following invention. I got the knowledge.
(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 hydration promotion treatment, and the dried slag is classified by the first sieve, Further, the sieve is screened with a second sieve smaller than the first sieve,
(Mass under second sieve) / (Mass on first sieve before hydration promotion treatment) × 100 (%) is defined as the slag disintegration rate, and the slag stability evaluation method .
(2) The hydration accelerating treatment is a treatment described in “Water immersion expansion test method” of JIS A5015 “Steel slag for road” or ASTM C151-08 “Expansion test method of Portland cement”. (1) The stability evaluation method of slag as described.
(3) The slag stability evaluation method according to (1) or (2) above, wherein the first sieve mesh is rougher by one or two stages in accordance with JIS Z8801-1 than the second sieve mesh. .
(4) The slag stability evaluation method according to any one of (1) to (3) above, wherein the first sieve is 9.5 mm and the second sieve is 8 mm. .
(5) The slag stability evaluation method according to any one of (1) to (4), wherein the slag from which coarse particles of 50 mm or more have been removed is subjected to hydration promotion treatment.
(6) Any of the above (1) to (5), wherein the aging treatment is a treatment which is allowed to stand for at least 1 month in the atmosphere or at least 6 hours under normal pressure or pressurized steam. The slag stability evaluation method according to claim 1.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
[0018]
As a result of investigating the stability of various slags that have been subjected to aging treatment, the present inventors have heretofore reported the "water immersion expansion test" and "autoclave expansion test" for evaluating the expansion of slag. According to the slag, it is clear that the hydration reaction is promoted, and that some of the digestible slag grains are expanded and destroyed as a result of hydration. It was known that the reduction in the expansion rate can be properly 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, the stability of the solidified body itself is examined by examining the stability of the solidified body, and at the same time, Even for steelmaking slag, which is the aggregate used, even if we measured the above expansion coefficient and investigated the correlation between them to find out the conditions for steelmaking slag applicable to solidified bodies, this expansion coefficient is As mentioned earlier, we are evaluating the average expansion behavior as a group (group) of slag of a certain volume, and even if the expansion rate is actually small, several slags that collapse are included. It was estimated that this would cause destruction of the solidified body.
[0020]
Therefore, instead of the expansion rate, the slag after the same hydration promotion treatment is screened and the disintegration rate (pulverization rate) is measured from the weight under the screen, and the correlation with the fracture state of the solidified body is also found. On the contrary, with this method, even if various aging treatments were applied, the collapse rate of slag varied widely, and it was still difficult to make a valid evaluation.
[0021]
However, according to the above method, individual slag grains that have clearly collapsed should have been measured. In order to investigate the cause of the large variation in the decay rate of the slag, the present inventors have conducted various further studies. As a result, the following knowledge was 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 is hydrated, the slag is sieved with the same first sieve and the slag particles under the sieve are observed in detail. It was found that relatively large slag grains that seemed to have not broken down were mixed in the slag that was broken by the treatment.
[0023]
The reason for this is that for the stability evaluation of these slags, fine particles are removed by classification treatment beyond the particle size required before the hydration promotion treatment, but all small slag is completely removed at this time. However, it is considered that some fine slag remained on the sieve and these slags fell under the sieve during classification after hydration promotion.
[0024]
Therefore, when the slag after the hydration promotion treatment is classified with the first sieve, and the sieve is further sieved with a second sieve smaller than the first sieve, the undisintegrated slag is apparently undissolved. As a result of being almost completely removed, only the slag that has collapsed by the hydration promotion treatment can be measured. By using this true decay rate, the decay rate is reduced if the original slag aging treatment is sufficient. Furthermore, it was clarified that this disintegration rate is closely related to the stability (destruction state) of the solidified body.
[0025]
FIG. 1 is a diagram showing the principle of the present invention. Here, as an example, in order to measure slag of 10 mm or more and 25 mm or less that has been aged in advance, the nominal dimensions (the length of one side of the mesh) 22.4 mm and 9.5 mm specified in JIS Z8801-1 Classify the slag in advance using sifter mesh. As the aging treatment, after standing in the atmosphere for at least one month, steam aging was performed at 180 ° C. for 6 hours as necessary.
[0026]
This slag is dried by performing hydration promotion treatment using hot water immersed in 80 ° C. (6 hours / day × 10 days) or autoclave (180 ° C. (about 20 atmospheres) × 6 hours). As in the case of classification with a 9.5 mm sieve mesh. However, under this sieving, there is still an uncollapsed and stable slag lump that must be sieved off during the previous classification process. Therefore, according to JIS Z8801-1, the slag under the above-mentioned 9.5 mm sieve is further classified using 8 mm, which is another one-stage sieve mesh (W3). In the figure, there is also shown an example in which the slag below the one-step small sieve is further sieved with a 2 mm sieve and separated into fragmentary slag and powdery slag (W2, W1).
[0027]
From this figure, according to the present invention, it is self-evident that the true collapse rate is indicated by the sum of the powder W1 and the fragmented slag amount W2 with respect to the original slag amount W0.
[0028]
However, conventionally, the sum of the powder (W1), the fragments (W2), and the undisintegrated slag (W3) is regarded as the decay rate. Of course, even if the prior classification is performed under certain conditions, it can be easily assumed that the slag W3 that should have been sieved out will vary during processing, which causes variations in measured values. The present inventors have found that.
[0029]
In addition, there is a case where the disintegration rate is considered as the disintegration rate by using only the powder W1 generated by the hydration treatment, as is partly reported as the powdering rate. The evaluation is much smaller than the true decay rate.
[0030]
Here, as a sieve used for classification, what is prescribed in the above-mentioned JIS Z 8801-1 is generally used in Japan. Furthermore, the final classification using a sieve smaller than the sieve used in the pre-classification process is a feature of the present invention. This includes a sieve having a size smaller by 1 to 2 stages as defined in JIS Z8801-1. It is preferable to use a slag having a small diameter, and a sieve mesh one step lower is sufficient. The prior classification process is generally performed with a large classifier, for example, but after the hydration promotion process, the amount of collapsed slag is small, and a low-tap tester is generally used to improve accuracy. Therefore, it is preferable in terms of measurement accuracy that the slag after the hydration promotion treatment is sufficiently dried to be classified for at least 3 minutes.
[0031]
As the hydration accelerating treatment of slag, JIS A5015 “steel slag for roads” “water immersion expansion test method” (10 days in hot water at 80 ° C.) or ASTM C151-08 which can be processed in a short time The method according to “Portland cement expansion test method” is generally used. In the latter case, sufficient data for evaluation can be obtained by treatment at 180 ° C. for 3 to 6 hours.
[0032]
Since the purpose of the present invention is to evaluate the slag disintegration rate after performing the aging treatment, after the aging treatment, to classify the undisintegrated slag, it is necessary to remove fine particles with the first sieve mesh. It is essential.
[0033]
Here, if the particle size of the original slag is 50 mm or less, preferably 25 mm or less, it is not necessary to classify the 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 these coarse particles and use them for the hydration promotion treatment in order to avoid mixing the mixed metal.
[0034]
In addition, as the aging treatment, it is preferable that the digestive component is allowed to stand for 1 month or more at room temperature or for 6 hours or more under normal pressure or pressurized steam in order to cause hydration reaction. The effect of the present invention can be obtained without any particular limitation on the upper limit of the pressurization. However, in order to efficiently and economically obtain the hydration promoting effect of MgO, which has a particularly slow hydration reaction rate, it is 1 to 10 atm. It is preferable to process.
[0035]
Furthermore, the amount of slag used for the evaluation is not particularly limited, but the more the aging treatment is performed for the stabilization of the slag, the more the slag disintegration rate decreases. It is better to use at least 5kg.
[0036]
Some slags have a rocky surface, and some have a sandstone texture. Especially in the latter case, powder is formed. The measurement accuracy is better when the adhered powder is removed.
[0037]
【Example】
(Example of the present invention)
FIG. 2 shows a steelmaking slag stabilized by an aging treatment that is allowed to stand at room temperature for at least one month, and sieved with nominal sizes of 22.4 mm and 9.5 mm defined by JIS Z8801-1 (particle size range of 10 to 10). 25mm) 5kg is dried at 110 ° C for 24 hours after slag is soaked in hot water at 80 ° C for 10 days according to "Water immersion expansion test method" of JIS A5015 "Steel slag for road" 1 and classified using a sieve having a nominal size of 9.5 mm defined in JIS Z8801-1 by the method shown in FIG. 1, and the nominal size defined in JISZ8801-1 is defined under the sieve. Further classification with an 8 mm sieve, true breakage obtained by (slag mass under 8 mm sieve) / (10-25 mm slag mass before hydration promotion treatment) × 100% To confirm the stability of the solidified body (diameter: 100mm * height: 200mm) using the same slag as an aggregate and other blast furnace slag fine powder as the main binder It is the graph which showed the correlation with the destruction rate of the solidified body at the time of the acceleration evaluation (immersion for 4 weeks in 80 degreeC warm water). The fracture rate of the solidified body was determined by the number of samples disintegrated by accelerated evaluation / the number of samples used for evaluation.
[0038]
From this figure, when the true collapse rate of the slag according to the present invention exceeds about 3%, the solidified sample using the slag as an aggregate also breaks down, so that an aging treatment with a collapse rate of 3% or less was performed. Slag was found to be suitable as an aggregate for solidified bodies.
(Comparative Example 1)
FIG. 3 shows a steel slag stabilized by aging treatment that is allowed to stand at room temperature for at least one month, and sieved at nominal sizes of 22.4 mm and 9.5 mm as defined in JIS Z8801-1 (particle size range of 10 to 10). 25 mm) is packed into a container (mold) specified in “Water immersion expansion test method” as Annex 2 in JIS A5015 “Steel slag for roads”. The operation of allowing to cool after holding for 6 hours is repeated once a day for 10 days, and the coefficient of expansion obtained by measuring the height of the sample in the mold after curing and the slag as an aggregate In addition, a solidified body (diameter 100mm * height 200mm), which is made by mixing blast furnace slag fine powder as the main binder and hardening it, is promoted for confirmation of stability in the same way as slag. Is a graph showing the correlation between destruction rate of the solidified body when the pickles). The fracture rate of the solidified body was determined by the same method as in the present invention example.
[0039]
From this figure, even if the expansion coefficient which is the conventional evaluation method is used, the solidified body using the slag is broken or not broken when it is in the range of 0.3% or more. It was not possible to find a suitable slag condition.
(Comparative Example 2)
FIG. 4 shows a steel slag stabilized by an aging treatment that is allowed to stand at room temperature for at least one month, and sieved at nominal sizes of 22.4 mm and 9.5 mm defined by JIS Z8801-1 (particle size range of 10 to 10). 25mm) 5kg is dried at 110 ° C for 24 hours after slag is soaked in hot water at 80 ° C for 10 days according to "Water immersion expansion test method" of JIS A5015 "Steel slag for road" Then, when classification is performed with a sieve having a nominal size of 9.5 mm as defined in JIS Z 8801-1 as used in the previous classification process (slag mass under a sieve of 9.5 mm) / (acceleration of hydration) 10-25mm slag mass before processing) x 100%, so-called collapse rate so far, and the slag is used as an aggregate and other blast furnace slag fine powder As a slag, a solidified body (diameter 100 mm * height 200 mm), which was mixed and hardened as a slag, was evaluated for acceleration (submerged in warm water at 80 ° C. for 4 weeks) with the fracture rate of the solidified body. It is the graph which showed the correlation. The fracture rate of the solidified body was determined by the same method as in the present invention example.
[0040]
From this figure, the slag decay rate according to the conventional method is mixed with partially uncollapsed slag grains as described above, so that when the decay rate is in the range of 2% or more, Comparative Example 1 Similarly, the solidified body using the slag was broken or not broken, and the slag conditions suitable for the stable solidified body could not be found.
[0041]
【The invention's effect】
According to the present invention, when steel slag, particularly steelmaking slag having a digestible component and having a property of expanding over a long period of time, is used for a new application such as a solidified material other than for roads, an aging treatment is performed. It is possible to accurately evaluate the stability of the slag that has been applied and stabilized.
[Brief description of the drawings]
FIG. 1 is a diagram showing the principle of the present invention.
FIG. 2 is a diagram showing a relationship between a collapse rate of slag according to the present invention and a fracture rate of a solidified body using the slag as an aggregate.
FIG. 3 is a diagram showing the relationship between the expansion rate of slag according to the prior art and the fracture rate of a solidified body using the slag as an aggregate.
FIG. 4 is a diagram showing a relationship between a collapse rate of slag according to a conventional technique and a fracture 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 hydration promotion treatment, and the dried slag is classified by the first sieve, and further this Sieving the sieve with a second sieve smaller than the first sieve, (mass under sieve of second sieve) / (mass on first sieve before hydration promoting treatment) × A method for evaluating the stability of slag, wherein 100% is defined as the slag collapse rate. The hydration accelerating treatment is a treatment described in "Water immersion expansion test method" of JIS A5015 "Steel slag for road" or ASTM C151-08 "Expansion test method of Portland cement". Slag stability evaluation method. The slag stability evaluation method according to claim 1 or 2, wherein the first sieve is rougher 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 slag stability evaluation method according to any one of claims 1 to 4, wherein the slag from which coarse particles of 50 mm or more are also removed is subjected to hydration promotion treatment. The aging process is a process of leaving at least one month or more in the atmosphere or six hours or more under normal pressure or pressurized steam. Slag stability evaluation method.

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