JP4357199B2 - 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 “hard” and “high wear resistance” of steelmaking slag. The property 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 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]
Here, in the “water immersion expansion test method” described in JIS A5015 “steel slag for roads”, the average expansibility as a mass (group) of a certain volume of steelmaking slag in the mold can be evaluated. , Because it is not possible to measure the damage caused by the individual expansion of the slag grains, which is one of the components, leading to the destruction of the solidified body, a phenomenon that the solidified body is broken even if the expansion coefficient is small, It was found that the slag stability could not be evaluated accurately.
[0012]
Further, 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 brick” 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) When the slag subjected to aging treatment is sieved with a first sieve mesh, and further under the sieve, a second sieve mesh smaller than the first sieve mesh, {(second sieve mesh Slag mass under sieve) / (Slag mass after aging treatment before classification) × 100 (%)}
Is the fine particle ratio (%) of slag after aging treatment,
Next, the aging-treated slag is further subjected to hydration promotion treatment, and the dried slag is sieved with the first sieve, and further, the sieve is screened under the sieve with the second sieve,
{(Mass of slag under sieving after hydration promotion treatment) / (Mass of slag before hydration promotion treatment and before aging treatment) × 100 ( %) }
Is defined as "fine slag fraction ratio (%) after hydration promotion treatment"
"Fine grain ratio of slag after hydration promotion treatment"-"Fine grain ratio of slag after aging treatment "
A method for evaluating the stability of slag, characterized in that the slag collapse rate is used.
(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) Any of the above (1) to (4), 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, the slag that has been aged is screened instead of the expansion rate,
{(Slag mass under sieve after aging treatment) / (Slag mass after aging treatment) × 100 (%)}
Is obtained in advance as the fine particle fraction (%) of the slag after the aging treatment, and then a hydration promotion test is further conducted without classifying the entire slag that was initially aged, and the slag after the hydration promotion treatment Sift with the same roughness as the sieve mesh,
{(Slag mass under sieving after hydration promotion treatment) / (Slag mass before hydration promotion treatment) × 100 (%)}
Is obtained as the fine particle fraction (%) of the slag after the hydration promotion treatment,
This "ratio of slag fine particles after hydration promotion treatment"-"ratio of slag fine particles after aging treatment" (%)
As the slag decay rate, the correlation with the fracture state of the solidified body was also investigated, but in this method, on the contrary, the slag decay rate varies greatly even after various aging treatments, and it is still difficult to make a valid evaluation It became.
[0021]
However, according to the above-described method, it should have been possible to measure individual slag grains that have clearly collapsed, and in order to investigate the cause of the large variation in the slag collapse rate, 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, the slag after the hydration promotion treatment was sieved and the slag grains under the sieving were observed in detail. As a result, the slag was clearly broken down into the fragmented or powdered slag that was destroyed by the hydration treatment. It was found that relatively large slag grains that seemed to be absent were mixed.
[0023]
In order to obtain an accurate slag disintegration rate, it is necessary to remove relatively large slag grains, which are apparently not disintegrated, contained under the sieve. This is the same problem when determining not only the fine particle ratio including the truly disintegrated slag particles after the hydration promotion treatment but also the slag fine particle fraction ratio after the aging treatment.
Therefore, the slag after aging treatment is sieved with a first sieve, and further, the lower sieve is sieved with a second sieve smaller than the first sieve,
{(Slag mass under sieve of second sieve) / (Slag mass after aging treatment before classification) × 100 (%) }
The slag after aging treatment was obtained in advance as “ the fine particle ratio (%) of the slag after aging treatment ” , and the slag after the hydration promotion treatment was dried, Sifting with a first sieve of the same roughness and further sieving under this sieve with a second sieve smaller than the first sieve will obviously remove the undisintegrated slag almost completely. As a result, only slag that has collapsed due to hydration promotion treatment can be measured,
{(Mass of slag under the second sieve after hydration promotion treatment) / (Mass of slag after aging treatment before hydration promotion treatment and before classification ) × 100 (% ) }
Is defined as "fine slag fraction ratio (%) after hydration promotion treatment"
"Fine grain ratio of slag after hydration promotion treatment"-"Fine grain ratio of slag after aging treatment "
If the original slag aging treatment is sufficient, the decay rate will decrease, and this decay rate is closely related to the stability of the solidified body (fracture state). I was able to clarify.
[0024]
FIG. 1 is a diagram showing the principle of the present invention. In the present invention, slag that has been aged in advance is used as a measurement target. As the aging treatment, after being left in the atmosphere for at least one month, steam aging was performed at 180 ° C. for 6 hours as necessary.
[0025]
In order to obtain the fine particle fraction of the slag after aging treatment, a certain amount of slag after aging treatment was classified with a 9.5 mm sieve according to JIS Z8801-1, and further under this sieve was JIS Z8801-1. In accordance with the above, classification is performed using 8 mm, which is one step smaller sieving mesh, and undisintegrated relatively large slag grains (W2) are removed to obtain a fine slag fraction after aging treatment under sieving (W1 ). Where {(slag mass under second sieve = W1) / (slag mass after aging treatment before classification = W0) × 100 (%)
Is calculated as “the ratio of fine particles of slag after aging treatment (%)”.
[0026]
Next, without classifying the whole slag that was initially aged, water was further added by using immersion in 80 ° C. warm water (6 hours / day × 10 days) or autoclave (180 ° C. (about 20 atmospheres) × 6 hours). After performing the sum promotion treatment and drying, similarly, classification is performed with a 9.5 mm sieve according to JIS Z8801-1, and the sieve under this sieve is further one stage smaller according to JIS Z8801-1. Classification using 8 mm, removing undisintegrated relatively large slag grains (W2 ′), and obtaining slag fine grains after aging treatment under sieving (W1 ′),
{ ( Mass of slag under the second sieve after hydration promotion treatment = W1 ′ ) / (Mass of slag before hydration promotion treatment and before aging treatment after aging treatment = W0) × 100 (%) }
Is defined as “the ratio of fine particles of slag after hydration promotion treatment (%)”.
[0027]
From this figure, the true slag collapse rate is obtained as follows.
[0028]
True slag disintegration rate = “Slag fraction ratio after hydration promotion treatment (%)”-“Slag fraction ratio after aging treatment (%)”
Conventionally, when evaluating the decay rate of slag, the slag content (the sum of W1 and W2) of the first sieving slag of the aging treatment slag, and the slag content of the first sieving after the hydration promotion treatment, that is, water The difference between the sum (W1 ′ + W2 ′) of the slag collapsed by the sum promotion process and the uncollapsed slag was regarded as the collapse rate. Even if the prior classification is performed under certain conditions, it is easy to assume that the slags W2 and W2 ', which should have been sieved out, will vary during processing, which is a variation in measured values. The present inventors have found out that
[0029]
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 that is one step lower is sufficient.
[0030]
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.
[0031]
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.
[0032]
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 a 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.
[0033]
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.
[0034]
Some slags have a rocky surface, and some have a sandstone texture. Especially in the latter case, powder is formed. The measurement accuracy improves when the adhered powder is removed.
[0035]
【Example】
(Example of the present invention)
FIG. 2 shows that 5 kg of a steelmaking slag (particle size range of 100 mm or less) stabilized by an aging treatment that is allowed to stand at room temperature for at least one month is a sieve having a nominal size of 9.5 mm defined by JIS Z8801-1 (first And further classify under the sieve with a sieve having a nominal size of 8 mm (second sieve) defined in JIS Z8801-1,
{(Slag mass under sieve of second sieve) / (Slag mass after aging treatment before classification) × 100 (%) }
Is obtained in advance as the fine-grain fraction ratio of the slag after aging treatment, and then 5 kg of the slag (grain size range of 100 mm or less) after the above aging treatment is applied to the “water immersion expansion test method” of JIS A5015 “steel slag for roads”. In accordance with JIS Z 8801-1 according to the method shown in FIG. 1 after immersing in warm water at 80 ° C. for 10 days to give hydration promotion treatment and drying at 110 ° C. for 24 hours. Classification is carried out using a sieve having a nominal size of 9.5 mm, and further classification is carried out with a sieve having a nominal size of 8 mm specified in JIS Z8801-1.
{(Mass of slag under sieve of second sieve after hydration promotion treatment) / (Mass of slag after aging treatment before hydration promotion treatment and before classification ) × 100 (%)}
Is calculated as the fine particle ratio of slag after hydration promotion treatment (fine particle ratio of slag after hydration promotion treatment)-(fine particle ratio of slag after aging treatment) (%)
The slag is a solidified body (diameter: 100 mm * height: 200 mm), which is a solid slag collapse rate obtained as follows, and the slag is used as an aggregate and mixed with blast furnace slag fine powder as a main binder It is the graph which showed the correlation with the fracture rate of the solidified body at the time of accelerated evaluation for a stability confirmation (immersion in 80 degreeC warm water for 4 weeks) similarly. 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.
[0036]
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)
FIG. 3 shows that 5 kg of steelmaking slag (particle size range of 100 mm or less) stabilized by aging treatment that is allowed to stand at room temperature for at least one month is sieved with a nominal size of 9.5 mm defined by JIS Z8801-1 (first Classify using only (sieving eyes),
{(Slag mass under sieve of first sieve) / (Slag mass after aging treatment before classification) × 100 (%)}
Is obtained in advance as the fine particle fraction (%) of the slag after aging treatment, and then 5 kg of the slag (grain size range of 100 mm or less) after the above aging treatment is subjected to a “water immersion expansion test of JIS A5015“ steel slag for roads ”. According to the “method”, slag was immersed in warm water at 80 ° C. for 10 days, subjected to hydration promotion treatment, dried at 110 ° C. for 24 hours, and then subjected to JIS Z 8801- by the method shown in FIG. Classification using only a sieve mesh having a nominal size of 9.5 mm (first sieve mesh) defined in 1.
{(Mass of slag under the first sieve after hydration promotion treatment) / (Mass of slag before hydration promotion treatment) × 100 (%)}
Is obtained as the fine-grain fraction of slag after hydration promotion treatment,
(Fine particle ratio of slag after hydration promotion treatment)-(Fine particle ratio of slag after aging treatment) (%)
The so-called slag decay rate and so-called slag that have been said to be used as an aggregate, and solidified blast furnace slag powder as a main binder (diameter 100 mm * height 200 mm) ) Is a graph showing the correlation with the fracture rate of the solidified body at the time of accelerated evaluation for confirming stability (immersion in warm water at 80 ° C. for 4 weeks) in the same manner as slag. The fracture rate of the solidified body was determined by the same method as in the present invention.
[0037]
From this figure, the slag decay rate according to the conventional method is mixed with some undegraded slag grains as described above, so when the decay rate is in the range of 2% or more, the slag As a result, the solidified product using slag was broken or not broken, and it was not possible to find the slag conditions suitable for a stable solidified product.
[0038]
【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 illustrates the principle of the present invention. (W0 to W2 are slag masses after aging treatment, and W1 ′ and W2 ′ are slag masses after hydration promotion treatment.)
FIG. 2 shows the relationship between the decay rate of slag according to the present invention and the fracture rate of a solidified body using the slag as an aggregate.
FIG. 3 shows the relationship between the collapse rate of slag according to the prior art and the fracture rate of a solidified body using the slag as an aggregate.

Claims (5)

When the aged slag is sieved with the first sieve mesh, and the screen under the sieve sieve is screened with a second sieve mesh smaller than the first sieve mesh, {(slag under the second sieve mesh) Mass) / (mass of slag after aging treatment before classification) × 100 (%)} is defined as “the fine particle ratio (%) of slag after aging treatment ”,
Next, the aging-treated slag is further subjected to hydration promotion treatment, and the dried slag is sieved with the first sieve, and further the sieve is screened with the second sieve,
{(Water second sieve of sieve under slag weight after sum promoting treatment) / (slag mass after hydration promoting pretreatment and before the classification of the aging process) × 10 0 (%)}
Is defined as "fine slag fraction ratio (%) after hydration promotion treatment"
"Fine grain ratio of slag after hydration promotion treatment"-"Fine grain ratio of slag after aging treatment "
A method for evaluating the stability of slag, characterized in that the slag collapse rate is used.   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.   5. The aging treatment is a treatment that is allowed to stand for at least 1 month in the atmosphere or at least 6 hours in a normal pressure or pressurized steam. 5. Slag stability evaluation method.

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