A method for evaluating volume stability of steel slag based on hydrothermal cycle treatment

Abstract

The application provides a steel slag volume stability evaluation method based on a wet heat cycle treatment, comprising the following steps: step one, steel slag aggregate preparation: crushing and screening the steel slag to be tested to obtain steel slag aggregates with different particle sizes; step two, concrete specimen preparation and volume detection: preparing steel slag mixed concrete according to a preset proportion, forming a steel slag mixed concrete specimen, and detecting the volume of the specimen; step three, wet heat cycle treatment: using a boiling tank to perform a wet heat cycle treatment on the specimen, and cooling the specimen to room temperature after the treatment; step four, volume comparison: detecting the volume of the specimen after the wet heat cycle treatment, and calculating the volume change rate before and after the wet heat cycle treatment; and step five, steel slag volume stability evaluation: performing volume stability evaluation according to the result obtained in step four. The application can reliably, simply and reasonably evaluate the volume stability of steel slag used as concrete aggregate, and promote the green development of steel slag used as concrete aggregate.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of bulk solid waste recycling, and particularly relates to a steel slag volume stability evaluation method based on wet heat cycle treatment. BACKGROUND

[0002] Steel slag, as a bulk industrial solid waste, has good engineering performance and can be widely used in the preparation of building materials. Using steel slag as concrete aggregate not only solves the environmental problems caused by large-scale steel slag stacking, but also greatly alleviates the shortage of sand and gravel aggregate resources in the building material industry, improves the additional utilization value of steel slag, and has important promoting significance for the green development of concrete materials.

[0003] However, there are a large number of extremely unstable expansive minerals in steel slag. Although many scholars at home and abroad have made many attempts in the evaluation of the volume stability of steel slag, the volume stability of steel slag aggregate in the actual engineering field application still has great uncertainty, and serious engineering safety problems can easily occur. Autoclaving is the most severe method for testing the volume stability of steel slag aggregate concrete, but this method also has a certain destructive effect on the strength of concrete. Even natural sandstone concrete will have a large strength loss after 28 days of standard curing and then directly subjected to 1.0 MPa saturated steam pressure. Therefore, a more scientific and reasonable method for testing and evaluating the volume stability of steel slag as concrete aggregate is still needed. SUMMARY

[0004] In view of the above problems, the present application is proposed in order to provide a steel slag volume stability evaluation method based on wet heat cycle treatment to overcome the above problems or at least partially solve the above problems, so that the volume stability test of steel slag as concrete aggregate can be truly and effectively performed, and a scientific and simple test and evaluation method for the application of steel slag in concrete aggregate is provided.

[0005] According to the steel slag volume stability evaluation method based on wet heat cycle treatment provided by the present application, the following steps are included:

[0006] Step one. Steel slag aggregate preparation: crushing and sieving the steel slag to be tested to obtain steel slag aggregates of different particle size ranges;

[0007] Step two. Concrete specimen preparation and volume detection: preparing steel slag aggregate concrete by replacing the corresponding particle size of natural aggregate with steel slag aggregate in a certain proportion and equal volume, and detecting the volume after curing;

[0008] Step three. Wet heat cycle treatment: using a boiling tank to perform wet heat cycle treatment on the steel slag aggregate concrete specimen, and cooling to room temperature after the treatment is completed;

[0009] Step four. Volume contrast: volume detection is performed on the test piece obtained in step three, and the volume change rate of the steel slag aggregate concrete before and after the hygrothermal cycle treatment is calculated;

[0010] Step five. Steel slag volume stability evaluation: volume stability evaluation is performed according to the results obtained in step four to determine the volume stability of the application particle size steel slag.

[0011] In some optional embodiments, in step four, the volume change rate is:

[0012] Wherein: Vr is the volume change rate of the test piece, %;

[0013] V is the volume of the test piece after hygrothermal treatment, mm 3 ;

[0014] V0 is the volume of the test piece before hygrothermal treatment, mm 3 ;

[0015] The volume values of the test piece before and after hygrothermal treatment are the average values of three test pieces.

[0016] In some optional embodiments, in step four, the volume change rate determination of the steel slag aggregate concrete test piece after boiling includes: if the steel slag aggregate concrete test piece has damage such as surface peeling, corner and side edge damage, etc., it is directly determined that it is completely deformed, and the volume change rate is 100%.

[0017] In some optional embodiments, in step five, if the volume change rate of the test piece is greater than the rated ratio, the volume stability of the application particle size steel slag is unqualified, and the steel slag cannot be used to prepare concrete. If the volume change rate of the test piece is less than or equal to the rated ratio, the volume stability of the application particle size steel slag is qualified.

[0018] In some optional embodiments, in step five, the rated ratio is 0.20% to 0.70%.

[0019] In some optional embodiments, in step one, the steel slag aggregate with different particle size ranges includes 0-5mm (including 5mm) particle size steel slag fine aggregate, 5-10mm (including 10mm) particle size steel slag coarse aggregate, and 10-20mm (including 20mm) particle size steel slag coarse aggregate.

[0020] In some optional embodiments, in step two, the steel slag aggregate concrete has a strength grade of C60, and the formula is: cement 420-460 parts, fly ash 80-120 parts, fine aggregate 990-1200 parts, coarse aggregate 900-1300 parts, water 160-200 parts, and water reducing agent 10-25 parts, wherein the weight ratio of 5-10mm (including 10mm) to 10-20mm (including 20mm) steel slag aggregate is 1:2.

[0021] In some optional embodiments, in the step two, the steel slag aggregate with a certain particle size is one or more of the following: steel slag fine aggregate with a particle size of 0-5 mm (including 5 mm), steel slag coarse aggregate with a particle size of 5-10 mm (including 10 mm), and steel slag coarse aggregate with a particle size of 10-20 mm (including 20 mm); and the proportion of each particle size range of steel slag aggregate replacing the corresponding particle size of natural aggregate is 90%-100% (including 100%).

[0022] In some optional embodiments, in the step two and the step three, the concrete volume detection method is a geometric calculation method, and the calculation formula is: :

[0023] In which: V is the volume of the test piece, mm 3 ;

[0024] a i is the center line of the test piece surface, which is measured by a vernier caliper, mm.

[0025] In some optional embodiments, in the step two, the size of the steel slag aggregate concrete test piece is 100 mm x 100 mm x 100 mm, the curing temperature is 18-22℃, the curing humidity is ≥95% RH, and the curing time is 28 days.

[0026] In some optional embodiments, in the step three, the boiling tank is provided with a liftable bearing table, a fan and an air blowing pipe. After boiling is completed, the bearing table drives the test piece to rise upward and separate from the boiling water. The fan is started to cool the test piece by air, thereby increasing the cooling rate of the test piece.

[0027] In some optional embodiments, in the step three, the total time of the wet and hot cycle treatment is 14-40 h, which is divided into 4-8 cycles, the cumulative boiling time is ≥12 h, and the cumulative wet and hot cycle period per day is ≥2.

[0028] In some optional embodiments, in the step three, the wet and hot cycle period mainly includes two steps:

[0029] (1) Boiling: after the test piece and water are placed in the boiling tank, heating is started. The boiling temperature should be raised to 100℃ within 30 min, and the constant boiling time should be 2.5-3.5 h. After the boiling time ends, the distilled water in the tank is emptied.

[0030] (2) Air blowing: after the test piece is lifted upward by the bearing table to separate from the boiling water, the fan is started to blow cold air to cool the test piece. The temperature of the test piece should be reduced to room temperature within 0.5-1 h.

[0031] In some optional embodiments, in the third step, the water quantity in the boiling tank is required to ensure that the water level can always cover the test piece in a single boiling time, and distilled water is not added during the wet heat cycle, and distilled water is added after the wet heat cycle.

[0032] The present application can obtain the following technical effects:

[0033] The present application effectively accelerates the hydration reaction of the expansion component in the steel slag under high temperature and high humidity conditions, and determines the feasibility of various graded steel slag as concrete aggregate by the volume change rate (Vr) of the steel slag aggregate concrete before and after the wet heat cycle, so that the volume stability evaluation of the steel slag as concrete aggregate can be scientifically performed.

[0034] The boiling condition adopted in the present application is relatively mild compared with the autoclaving condition, and will not cause serious damage to the concrete, so that the volume change rate of the concrete can be maintained within a relatively reasonable numerical range, and the boiling operation is relatively safe and simple, and does not need to consider the pressure change, so that the present application has good operability.

[0035] The above description is only a summary of the technical scheme of the present application, in order to more clearly understand the technical means of the present application, and can be implemented according to the content of the specification, and in order to make the above and other purposes, characteristics and advantages of the present application more obvious and easy to understand, the following specific embodiments of the present application are described. BRIEF DESCRIPTION OF DRAWINGS

[0036] Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The accompanying drawings are included to provide a description of the preferred embodiments and are not meant to limit the present application. Furthermore, the same reference numerals are used throughout the several drawings to designate the same or similar parts. In the drawings:

[0037] Figure 1 The flowchart of the steel slag volume stability evaluation method based on the wet heat cycle treatment provided in some embodiments of the present application is shown in the figure.

[0038] Figure 2 The overall schematic diagram of the steel slag volume stability evaluation method based on the wet heat cycle treatment provided in some embodiments of the present application is shown in the figure. DETAILED DESCRIPTION

[0039] Exemplary embodiments of the present application will be described herein below with reference to the accompanying drawings. Although exemplary embodiments of the present application are shown in the drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided so that the present application can be more thoroughly understood and the scope of the present application can be accurately conveyed to those skilled in the art.

[0040] According toFigure 1 and Figure 2 A steel slag volume stability evaluation method based on a wet heat cycle treatment according to an embodiment of the present application is shown and at least includes the following steps:

[0041] Step one. Steel slag aggregate preparation: crush and sieve the steel slag to be tested to obtain steel slag aggregates of different particle sizes;

[0042] Step two. Concrete specimen preparation and volume detection: replace the natural aggregates of the corresponding particle size with the steel slag aggregates obtained in step one at a certain ratio to prepare steel slag aggregate concrete, and detect the volume after curing;

[0043] Step three. Wet heat cycle treatment: use a boiling box to perform a wet heat cycle treatment on the steel slag aggregate concrete specimen, and cool to room temperature after the end of the treatment;

[0044] Step four. Volume comparison: detect the volume of the specimen obtained in step three, and calculate the volume change rate of the steel slag aggregate concrete before and after the wet heat cycle treatment;

[0045] Step five. Steel slag volume stability evaluation: evaluate the volume stability according to the results obtained in step four to determine the volume stability of the steel slag of the application particle size.

[0046] In an optional embodiment, in step four, the volume change rate is:

[0047] Wherein: Vr is the specimen volume change rate, %;

[0048] V is the specimen volume after the wet heat treatment, mm 3 ;

[0049] V0 is the specimen volume before the wet heat treatment, mm 3 ;

[0050] The specimen volume values before and after the wet heat treatment are the average values of three specimens.

[0051] In an optional embodiment, in step four, the volume change rate determination of the steel slag aggregate concrete specimen after boiling includes: if the steel slag aggregate concrete specimen has damage such as skin peeling, corner and side edge damage, etc., it is directly determined that it has completely deformed, and the volume change rate is 100%.

[0052] In an optional embodiment, in step five, if the specimen volume change rate is greater than the rated ratio, the volume stability of the steel slag of the application particle size is unqualified, and the steel slag cannot be used to prepare concrete; if the specimen volume change rate is less than or equal to the rated ratio, the volume stability of the steel slag of the application particle size is qualified.

[0053] In an alternative embodiment, the rated ratio in step five is 0.20% to 0.70%.

[0054] In an alternative embodiment, the different particle size range of steel slag aggregate in step one includes 0-5mm (including 5mm) particle size steel slag fine aggregate, 5-10mm (including 10mm) particle size steel slag coarse aggregate, and 10-20mm (including 20mm) particle size steel slag coarse aggregate.

[0055] In an alternative embodiment, the steel slag aggregate concrete preparation strength grade in step two is C60, and the formula is: cement 420-460 parts, fly ash 80-120 parts, fine aggregate 990-1200 parts, coarse aggregate 900-1300 parts, water 160-200 parts, and water reducing agent 10-25 parts, wherein the weight ratio of 5-10mm (including 10mm) to 10-20mm (including 20mm) steel slag aggregate is 1:2.

[0056] In an alternative embodiment, the steel slag aggregate of a certain particle size in step two is one or more of 0-5mm (including 5mm) particle size steel slag fine aggregate, 5-10mm (including 10mm) particle size steel slag coarse aggregate, and 10-20mm (including 20mm) particle size steel slag coarse aggregate; the replacement ratio of each particle size range of steel slag aggregate to the corresponding particle size of natural aggregate is 90%-100% (including 100%).

[0057] In an alternative embodiment, the concrete volume detection method in steps two and three is a geometric calculation method, and the calculation formula is: :

[0058] Wherein: V——test volume, mm 3 ;

[0059] a i ——Test specimen centerline, measured by vernier caliper, mm.

[0060] In an alternative embodiment, the steel slag aggregate concrete test specimen size in step two is 100mm×100mm×100mm, the curing temperature is 18-22℃, the curing humidity is ≥95%RH, and the curing time is 28 days.

[0061] In an alternative embodiment, the boiling tank in step three is provided with a liftable bearing table, a fan and an air blowing pipe. After boiling is completed, the bearing table drives the test specimen to rise upward and separate from the boiling water. The fan is started to cool the test specimen, thereby increasing the cooling rate of the test specimen.

[0062] In an alternative embodiment, in step three, the total time of the wet heat cycle treatment is 14-40 hours, and the boiling time is accumulated to be greater than or equal to 12 hours, and the accumulated wet heat cycle period per day is greater than or equal to 2.

[0063] In an alternative embodiment, in step three, the wet heat cycle period mainly includes two steps:

[0064] (1) Boiling: the boiling tank is placed with the test piece, water is added, and then heating is started. The boiling temperature is increased to 100°C within 30 minutes, and the constant boiling time is ensured to be 2.5-3.5 hours. The boiling time is ended, and the distillation water in the tank is emptied.

[0065] (2) Air blowing: after the test piece is lifted up by the bearing table to separate from the boiling water, the air blower is started to blow cold air to cool the test piece. The temperature of the test piece is decreased to room temperature within 0.5-1 hour.

[0066] In an alternative embodiment, in step three, the water amount in the boiling tank is required to ensure that the water level can always cover the test piece during the boiling time of a single period. The distillation water is not added during the wet heat cycle period, and the distillation water is added after the wet heat cycle period is ended. Specific embodiments

[0067] In this embodiment, steel slag produced by three steel plants is crushed and sieved into fine aggregate of 0-5 mm (including 5 mm), coarse aggregate of 5-10 mm (including 10 mm), and coarse aggregate of 10-20 mm (including 20 mm).

[0068] The component mixing ratio of the steel slag aggregate concrete can be referred to Table 1. Numbers S1-S10 are 10 specific embodiments.

[0069] Table 1: Mixing ratio of steel slag aggregate concrete

[0070]

[0071] The different particle size ranges of the steel slag aggregate used in the above embodiments S1-S4 are all produced by steel plant A. S1 is completely replaced by natural sand with the steel slag fine aggregate; S2 is completely replaced by 5-10 mm (including 10 mm) natural crushed stone with the 5-10 mm (including 10 mm) steel slag coarse aggregate; S3 is completely replaced by 10-20 mm (including 20 mm) natural crushed stone with the 10-20 mm (including 20 mm) steel slag coarse aggregate; S4 is completely replaced by natural coarse aggregate with the 5-20 mm (including 20 mm) steel slag coarse aggregate, and completely replaced by natural fine aggregate with the steel slag fine aggregate. The boiling period of the test piece is 6, and the constant boiling time of each period is 3 hours, which is performed in two days.

[0072] The different particle size ranges of the steel slag aggregates to be tested used in the above-described Examples S5-S7 were all produced by Steel Mill B. In S5, 90% of the natural sand was replaced by fine steel slag aggregates to be tested; in S6, 90% of the 5-10 mm (including 10 mm) natural crushed stones were replaced by 5-10 mm (including 10 mm) steel slag coarse aggregates; and in S7, 90% of the 5-20 mm (including 20 mm) natural crushed stones were replaced by 5-20 mm (including 20 mm) steel slag coarse aggregates to be tested. The boiling periods of the test specimens were 5 in total, and each period lasted for 3.5 h, which was performed in two days.

[0073] The different particle size ranges of the steel slag aggregates to be tested used in the above-described Examples S8-S10 were all produced by Steel Mill C. In S8, 95% of the natural sand was replaced by fine steel slag aggregates to be tested; in S9, 95% of the 5-10 mm (including 10 mm) natural crushed stones were replaced by 5-10 mm (including 10 mm) steel slag coarse aggregates to be tested; and in S10, 95% of the 10-20 mm (including 20 mm) natural crushed stones were replaced by 10-20 mm (including 20 mm) steel slag coarse aggregates, and 95% of the natural fine aggregates were replaced by fine steel slag aggregates to be tested. The boiling periods of the test specimens were 8 in total, and each period lasted for 2.5 h, which was performed in two days. The following test results were obtained:

[0074] Table 2. Test results of the volume of the steel slag aggregate concrete

[0075]

[0076] From the component proportions and test results of Examples S1-S10, it can be seen that the volume change rates of the steel slag aggregate concrete S1-S3 prepared by using the steel slag produced by Steel Mill A were all not more than 0.25%, i.e., the volume stabilities of the 0-5 mm (including 5 mm) fine aggregates, 5-10 mm (including 10 mm) and 10-20 mm (including 20 mm) coarse aggregates were good, and the three kinds of steel slag aggregates could be used singly as the aggregates for preparing the concrete. However, the volume change rate of S4 was higher than 0.40%, i.e., the volume stability of the 0-20 mm continuous graded steel slag aggregates was poor, and the steel slag could not be used for preparing the concrete.

[0077] The steel slag aggregate concrete S5-S8 prepared by using the steel slag produced by Steel Mill B, the volume loss of S5 was more than 0.70%, and the volume change rates of S6 and S7 were all not more than 0.25%. It can be seen that the volume stability of the steel slag sand produced by Steel Mill B was poor, while the volume stabilities of the 5-10 mm (including 10 mm) and 5-20 mm (including 20 mm) coarse aggregates were qualified.

[0078] The volume change rates of the steel slag aggregate concrete S8-S10 prepared by using the steel slag produced by Steel Mill C were all more than 0.25%. It can be seen that the volume stabilities of the steel slag sand, 5-10 mm (including 10 mm) and 10-20 mm (including 20 mm) coarse aggregates produced by Steel Mill C were poor.

[0079] In summary, the embodiments of the present application can obtain the following features and effects:

[0080] 1. The high temperature and high humidity conditions are used to effectively accelerate the hydration reaction of the expansion component in the steel slag, the volume change rate (Vr) of the concrete before and after the wet heat cycle of the steel slag aggregate is used to determine the feasibility of various gradation steel slag as concrete aggregate, and the volume stability evaluation of the steel slag as concrete aggregate can be scientifically performed.

[0081] 2. The boiling condition is relatively mild compared with the pressure steaming condition, and will not cause serious damage to the concrete, so that the volume change rate of the concrete is kept in a relatively reasonable range; and the boiling operation is relatively safe and simple, and does not need to consider the pressure change, and has good operability.

[0082] It should be noted that:

[0083] The algorithms and displays presented herein are not inherently related to any particular computer, virtual system, or other apparatus. Various general purpose systems can be used with programs in accordance with the teachings herein, or it can prove convenient to construct more specialized apparatus to perform the required method steps. The required structure for a variety of these systems will be apparent from the description above. In addition, the present application is not intended to be limited to a particular programming language. It will be appreciated that there are many programming languages that can be used to implement the teachings herein, and any such programming language can be used in connection with the various aspects of the present application.

[0084] In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the application can be practiced without these specific details. In some instances, well-known methods, structures and techniques have not been described in detail in order to not obscure the understanding of this description.

[0085] Similarly, it is to be understood that the mechanical details of the application sometimes are presented in terms of one or more exemplary implementations thereof, and / or to descriptions thereof in the context of one or more particular applications. However, it should be readily apparent to those skilled in the art that the metes of the present application are not limited to those implementations per se described above but apply to any and all equivalents thereof.

[0086] Those skilled in the art will appreciate that the modules in the apparatuses in the embodiments can be adapted and placed in one or more apparatuses other than that in the embodiments. The modules or units or components in the embodiments can be combined into one module or unit or component, and furthermore can be split into multiple sub-modules or sub-units or sub-components. Any combination of all the features disclosed in the specification (including the accompanying claims, abstract and drawings), and any method or process or device of any combination of the features disclosed in the specification (including the accompanying claims, abstract and drawings) can be taken, except that at least some of such features and / or processes or units are mutually exclusive, unless specifically stated otherwise. Each feature disclosed in the specification (including the accompanying claims, abstract and drawings) can be replaced by alternative features serving the same, equivalent or similar purpose, unless specifically stated otherwise.

[0087] Furthermore, those skilled in the art will appreciate that different embodiments of the application have different features and thus not all embodiments will exhibit all of the features described herewith, although each feature should be considered a part of at least one embodiment of the application. It should also be noted that not all of the features described herewith are necessary in every situation and the application should not be construed as limited to only those embodiments that include all of the features described herewith.

[0088] It should be noted that the above-mentioned embodiments illustrate rather than limit the application, and that one skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word 'comprising' does not exclude the presence of elements or steps other than those listed in a claim. The word 'a' or 'an' preceding an element does not exclude the presence of a plurality of such elements. The application can be implemented by means of both hardware and software, and any combination thereof. In a system claim enumerating several means, several of these means can be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different claims does not indicate that a combination of these measures cannot be used to advantage. The application relates to all possible combinations of features unless otherwise explicitly stated (e.g. combinations that include analogous structures to those shown in the figures, combinations that include features from different embodiments, combinations that include features from the same embodiment, combinations that include features from the same figure, combinations that include features from different figures, combinations that include features from the same claim, combinations that include features from different claims, combinations that include features from the same paragraph, combinations that include features from different paragraphs, combinations that include features from the same section, combinations that include features from different sections, combinations that include features from the same document, combinations that include features from different documents, combinations that include features from the same patent, combinations that include features from different patents, combinations that include features from the same inventor, combinations that include features from different inventors, combinations that include features from the same assignee, combinations that include features from different assignees, combinations that include features from the same company, combinations that include features from different companies, combinations that include features from the same country, combinations that include features from different countries, combinations that include features from the same continent, combinations that include features from different continents, combinations that include features from the same hemisphere, combinations that include features from different hemispheres, combinations that include features from the same hemisphere, combinations that include features from different hemispheres, combinations that include features from the same hemisphere, combinations that include features from different hemispheres, combinations that include features from the same hemisphere, combinations that include features from different hemispheres, combinations that include features from the same hemisphere, combinations that include features from different hemispheres, combinations that include features from the same hemisphere, combinations that include features from different hemispheres, combinations that include features from the same hemisphere, combinations that include features from different hemispheres, combinations that include features from the same hemisphere, combinations that include features from different hemispheres, combinations that include features from the same hemisphere, combinations that include features from different hemispheres, combinations that include features from the same hemisphere, combinations that include features from different hemispheres, combinations that include features from the same hemisphere, combinations that include features from different hemispheres, combinations that include features from the same hemisphere, combinations that include features from different hemispheres, combinations that include features from the same hemisphere, combinations that include features from different hemispheres, combinations that include features from the same hemisphere, combinations that include features from different hemispheres, combinations that include features from the same hemisphere, combinations that include features from different hemispheres, combinations that include features from the same hemisphere, combinations that include features from different hemis

Claims

1. A method for evaluating the volume stability of steel slag based on hydrothermal cycle treatment, characterized by, It comprises the following steps: Step one. Steel slag aggregate preparation: the steel slag to be tested is crushed and sieved to obtain steel slag aggregates of different particle size ranges, including one or more of 0-5 mm particle size steel slag fine aggregate, 5-10 mm particle size steel slag coarse aggregate, and 10-20 mm particle size steel slag coarse aggregate; Step two. Concrete specimen preparation and volume detection: prepare steel slag aggregate concrete by mixing the steel slag aggregates obtained in step one according to a predetermined ratio, form steel slag aggregate concrete specimens, and cure the specimens at a curing temperature of 18-22°C and a curing humidity of ≥95% RH for 28 days, and then detect the volume; the steel slag aggregate concrete has a strength grade of C60, and the formulation is: cement 420-460 parts, fly ash 80-120 parts, fine aggregate 990-1200 parts, coarse aggregate 900-1300 parts, water 160-200 parts, and water reducing agent 10-25 parts; Step three. Wet heat cycle treatment: use a boiling tank to perform wet heat cycle treatment on the steel slag aggregate concrete specimens, and cool to room temperature after the treatment; the wet heat cycle period mainly includes two steps: (1) boiling: place the specimens in the boiling tank, add water, and start heating; the boiling temperature is raised to 100°C within a predetermined time, and the constant boiling time is 2.5-3.5 h; after the boiling time ends, empty the distilled water in the tank; (2) air blowing: after the specimens are lifted up and separated from the boiling water, start the air blower to blow cold air to cool the specimens; the temperature of the specimens should be reduced to room temperature within 0.5-1 h; the total wet heat cycle time is 14-40 h, which is divided into 4-8 cycles; the boiling time is ≥12 h in total, and the cumulative wet heat cycle period per day is ≥2; the water level in the boiling tank should be high enough to cover the specimens during the boiling time of each cycle; distilled water should not be added during the wet heat cycle period; after the wet heat cycle period ends, add distilled water; Step four. Volume contrast: the volume of the test piece after step three is detected, and the volume change rate of the steel slag aggregate concrete before and after the hygrothermal cycle treatment is calculated, and the volume change rate is: , Wherein: Vr is the specimen volume change rate, %; V is the specimen volume after wet heat treatment; V0 is the specimen volume before wet heat treatment; The specimen volume values before and after wet heat treatment are the average values of multiple specimens; Step five. Steel slag volume stability evaluation: evaluate the volume stability based on the results obtained in step four to determine the volume stability of the applied particle size steel slag; if the specimen volume change rate is greater than the rated ratio, the volume stability of the applied particle size steel slag is determined to be unqualified and cannot be used to prepare concrete; if the specimen volume change rate is less than or equal to the rated ratio, the volume stability of the applied particle size steel slag is determined to be qualified.

2. The method for evaluating the volume stability of steel slag based on hydrothermal cycle treatment according to claim 1, characterized in that, In step four, if the steel slag aggregate concrete specimens after boiling show skin peeling, corner and side edge damage, they are directly determined to be completely deformed.

3. The method for evaluating the volume stability of steel slag based on hydrothermal cycle treatment according to claim 1, characterized in that, The rated ratio is 0.20%-0.70%.

4. The method for evaluating the volume stability of steel slag based on hydrothermal cycle treatment according to claim 1, characterized in that, In step two, the weight ratio of 5-10 mm and 10-20 mm steel slag aggregates is 1:

2.

5. The method for evaluating the volume stability of steel slag based on hydrothermal cycle treatment according to claim 1, characterized in that, In step two, the replacement ratio of steel slag aggregates of each particle size range with natural aggregates of the corresponding particle size is 90%-100%.

6. The method for evaluating the volume stability of steel slag based on hydrothermal cycle treatment according to claim 1, characterized in that, In the second step, the volume detection method is a geometric calculation method, and the calculation formula is: , Wherein: V is the specimen volume; a i - specimen face centerline, as measured with a vernier caliper.

7. The method for evaluating the volume stability of steel slag based on hydrothermal cycle treatment according to claim 1, characterized in that, The steel slag volume stability evaluation method based on wet heat cycle treatment further comprises at least one of the following: In the second step, the size of the steel slag aggregate concrete test piece is 100mm*100mm*100mm; In the third step, the boiling tank is provided with a lifting bearing table, a fan and an air blowing pipe. After boiling, the bearing table drives the test piece to rise upward, and the test piece is separated from the boiling water. The fan is started to cool the test piece by air, and the cooling rate of the test piece is increased.

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