Method for determining effective relative density of steel slag and method for determining bulk volume relative density

Abstract

The present application relates to a method for determining effective relative density of steel slag and a method for determining bulk volume relative density, comprising the following steps: obtaining the asphalt mass required for completely wrapping the steel slag according to the asphalt film thickness, and then obtaining the oil-rock ratio, which is the mass ratio of asphalt to steel slag; according to the oil-rock ratio, batching the asphalt and the steel slag, mixing after preheating, and obtaining the uniformly coated steel slag; dispersing the prepared coated steel slag to obtain a dispersion, cooling the dispersion to a set temperature, weighing a set mass of the dispersion, placing it into a negative pressure device, adding water in the negative pressure device, and then vacuumizing; obtaining the theoretical maximum relative density according to the mass of the negative pressure device and the dispersion in water and the mass of the negative pressure device in water; obtaining the effective relative density of the steel slag according to the theoretical maximum relative density and the oil-rock ratio; the method principle is clear, the testing process is simple, and the determined result is more accurate than the traditional testing method.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of asphalt pavement materials, in particular to a method for determining effective relative density of steel slag and a method for determining bulk volume relative density. BACKGROUND

[0002] The statements herein are provided only to enhance understanding of the present application and are not necessarily intended to constitute the prior art.

[0003] Steel slag has been increasingly used as coarse aggregate in asphalt mixture due to its high strength and abrasion resistance. The effective relative density and bulk volume relative density of aggregate, including steel slag, are important basic data for the mix design of asphalt mixture, and their accuracy is particularly important. The current method for determining the effective relative density of steel slag is the asphalt immersion method, i.e. the steel slag is placed in a container filled with asphalt, and the steel slag is completely immersed in the asphalt, so as to test the effective relative density of the steel slag. This method does not correspond to the actual working conditions, as the mass of steel slag in asphalt mixture is much greater than that of asphalt, and it is impossible for the steel slag to be completely immersed in the asphalt, so the test result is inaccurate. The bulk volume relative density of coarse aggregate is generally tested by the basket method of T0304-2005 in JTG E42-2005 "Highway Engineering Aggregate Test Procedures", but for steel slag, the surface water of steel slag particles needs to be wiped off with a towel when the basket method is used to test, and the mass of the surface-dried steel slag is measured. Due to the presence of many pores on the surface of steel slag, and some large pores, the water in these pores is easily wiped off, which often leads to an overestimation of the bulk volume relative density. CN103528918A discloses a test method for effectively determining the maximum theoretical relative density of asphalt mixture. Although the application involves a method for determining the effective relative density of coarse aggregate, the asphalt-coated aggregate is aggregated together, and there are inevitably voids, which cause the effective volume to be too large and the effective relative density to be too small. SUMMARY

[0004] The purpose of the present application is to overcome the shortcomings of the prior art, and to provide a method for determining the effective relative density of steel slag, which is relatively accurate.

[0005] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0006] In a first aspect, the embodiments of the present application provide a method for determining the effective relative density of steel slag, comprising the following steps:

[0007] The asphalt mass required for completely coating the steel slag is obtained according to the asphalt film thickness, and then the oil-stone ratio is obtained, which is the mass ratio of asphalt to steel slag;

[0008] The asphalt and steel slag are proportioned according to the oil-stone ratio, and after preheating, they are mixed to obtain asphalt-coated steel slag.

[0009] The prepared asphalt-coated steel slag is dispersed to obtain a dispersion, and the dispersion is cooled to a set temperature, then a dispersion of a set mass is placed into a negative pressure device, water is added in the negative pressure device, and then vacuum is extracted;

[0010] A theoretical maximum relative density is obtained according to the mass of the negative pressure device and the dispersion in water and the mass of the negative pressure device in water;

[0011] An effective relative density of the steel slag is obtained according to the theoretical maximum relative density and the oil-stone ratio.

[0012] Optionally, a plurality of theoretical maximum relative density values are obtained by placing dispersions of asphalt-coated steel slag of different set masses into a negative pressure device, adding water, and then extracting vacuum, and an average value of the plurality of theoretical maximum relative density values is taken as a final theoretical maximum relative density.

[0013] Optionally, the set mass of the dispersion of the asphalt-coated steel slag is in a range of 900g-1500g.

[0014] Optionally, the asphalt is SBS modified asphalt.

[0015] Optionally, the steel slag is preheated at 170℃-180℃ for 3.5-4.5h, and preferably, the steel slag is preheated at 180℃ for 4h.

[0016] Optionally, the asphalt is preheated at 160℃-180℃ for 2.5-3.5h, and preferably, the asphalt is preheated at 175℃ for 3h.

[0017] Optionally, the mixer is preheated to 170℃-180℃ in advance, and then the asphalt and the steel slag are poured into the mixer for mixing.

[0018] Optionally, the asphalt-coated steel slag is taken out from the mixer and placed in a porcelain dish, the asphalt-coated steel slag is dispersed and cooled to a set temperature, and the set temperature is 20℃-30℃.

[0019] Optionally, the mixing time of the steel slag and the asphalt is 90s-120s.

[0020] In a second aspect, embodiments of the present application provide a method for determining a bulk volume relative density of steel slag, the method comprising: determining an effective relative density of the steel slag by the method of the first aspect; and determining the bulk volume relative density of the steel slag by combining the effective relative density and an apparent relative density of the steel slag.

[0021] The present application has the following beneficial effects:

[0022] 1.The effective density determination method of steel slag of the present application, by mixing asphalt and steel slag according to the calculated oil-rock ratio to obtain asphalt-coated steel slag (A-Slag), and forming a dispersion after complete dispersion, the dispersion is vacuumed by a negative pressure device, and the theoretical maximum relative density is obtained according to the mass of the negative pressure device and the dispersion in water and the mass of the negative pressure device in water, the method is not affected by the pores of A-Slag, and the result is accurate; the effective relative density of steel slag is obtained according to the theoretical maximum relative density and the oil-rock ratio, the principle is clear and explicit, the calculation is relatively simple, and the result is more accurate compared with the traditional asphalt impregnation method.

[0023] 2.The bulk volume relative density determination method of steel slag of the present application, which is calculated by the obtained effective relative density and the apparent relative density, without using the net basket method, and the measurement result is more accurate. BRIEF DESCRIPTION OF DRAWINGS

[0024] The drawings accompanying the specification of the present application serve to provide further understanding of the present application, the illustrative embodiments of the present application and the description thereof serve to explain the present application, and do not constitute a limitation on the present application.

[0025] Figure 1 It is a method flowchart of Example 1 of the present application;

[0026] Figure 2 It is a photograph of the weighed steel slag of Example 1 of the present application;

[0027] Figure 3 It is a photograph of the asphalt-coated steel slag dispersion of Example 1 of the present application DETAILED DESCRIPTION

[0028] In a typical embodiment of the present application, the effective relative density determination method of steel slag in Example 1, as shown in the figure, includes the following steps: Figure 1

[0029] Step 1: obtain the required asphalt mass for completely wrapping the steel slag according to the asphalt film thickness (the asphalt film thickness is 6-8um), and then obtain the oil-rock ratio, which is the mass ratio of asphalt to steel slag;

[0030] The asphalt is SBS modified asphalt or other modified asphalt meeting the specification requirements. The required asphalt mass can be calculated by using the existing theoretical calculation method, which is not described in detail here.

[0031] Step 2: according to the oil-rock ratio, the asphalt and steel slag are dosed and mixed after preheating to obtain uniformly asphalt-coated steel slag, which is referred to as A-Slag in this embodiment;

[0032] ​Step 3: Pour the prepared asphalt-coated steel slag (A-Slag) into a clean porcelain dish, quickly break it apart while cooling, and form a completely dispersed A-Slag dispersion; complete dispersion means that the asphalt-coated steel slag particles are laid flat in a layer on the porcelain dish, without particles sticking together, etc.

[0033] After cooling to the set temperature, a set mass of A-Slag dispersion is placed into the negative pressure device, water is added, and then vacuum is extracted.

[0034] The amount of water added is such that the water covers the A-Slag dispersion, i.e. the A-Slag dispersion is completely immersed in the water in the negative pressure device.

[0035] The negative pressure device is selected from any type specified in JTG E20-2011 "Highway Engineering Asphalt and Asphalt Mixture Test Procedures" T0711-2011, which is not described in detail here.

[0036] Step 4: Place the negative pressure device into which the A-Slag dispersion is poured and vacuum is extracted into a water tank containing water, measure the mass of the negative pressure device and A-Slag dispersion in water, i.e. the sum of the mass of the negative pressure device in water and the mass of the A-Slag dispersion in water, then remove the A-Slag dispersion, measure the mass of the negative pressure device in water, and obtain the theoretical maximum relative density according to the mass of the negative pressure device and A-Slag dispersion in water and the mass of the negative pressure device in water.

[0037] Specifically, the calculation method of the theoretical maximum relative density γ t is as follows:

[0038]

[0039] Wherein, m d is the set mass of the A-Slag dispersion, m s is the mass of the negative pressure device and asphalt-coated steel slag in water after vacuum extraction, and m w is the mass of the negative pressure device in water.

[0040] Step 5: Obtain the effective relative density of the steel slag according to the theoretical maximum relative density and the oil-stone ratio.

[0041] Specifically, the calculation method of the effective relative density of the steel slag γ se is as follows:

[0042]

[0043] Pa is the oil-stone ratio of A-Slag; γ s is the relative density of SBS modified asphalt, dimensionless.

[0044] In steps 3-4, different set quality of A-Slag dispersion is weighed and placed in a negative pressure device, then water is added in the negative pressure device, and then vacuum is extracted to obtain a plurality of theoretical maximum relative density values, and the average value is taken as the final theoretical maximum relative density.

[0045] The set quality of A-Slag dispersion is in the range of 900g-1500g.

[0046] In step 2, the steel slag is preheated at 170-180℃ for 3.5-4.5h, preferably, the steel slag is preheated at 180℃ for 4h. In this embodiment, the steel slag is placed in an oven, the oven is started, and after the oven temperature reaches 170-180℃, it is maintained for 3.5-4.5h, preferably, after the oven temperature reaches 180℃, it is maintained for 4h.

[0047] In step 2, the asphalt is preheated at 160-180℃ for 2.5-3.5h, preferably, the asphalt is preheated at 175℃ for 3h. In this embodiment, the asphalt is placed in an oven, the oven is started, and after the oven temperature reaches 160-180℃, it is maintained for 2.5-3.5h, preferably, after the oven temperature reaches 175℃, it is maintained for 3h.

[0048] In step 2, the mixer is preheated to 170-180℃ before pouring in the asphalt and steel slag for mixing.

[0049] In step 2, the mixing time of steel slag and asphalt is 90-120s.

[0050] In step 3, the asphalt-coated steel slag is taken out of the mixer and placed in a porcelain dish, and the asphalt-coated steel slag is dispersed and cooled to a set temperature, which is room temperature, and the room temperature is 20-30℃.

[0051] In one specific application example of this embodiment:

[0052] The effective relative density and bulk volume relative density of 10-15mm coarse steel slag are determined. The specific implementation steps are as follows:

[0053] 1) As shown in the figure, about 2kg of 10-15mm steel slag is weighed; Figure 2

[0054] 2) To ensure that the steel slag is completely coated with SBS modified asphalt, the asphalt film thickness is set to 7μm, and the oil-stone ratio is calculated to be 4.0%;

[0055] 3) The steel slag is preheated at 180℃ for 4h, the SBS modified asphalt is preheated at 175℃ for 3h, the mixing pot is preheated to 175℃, and after preheating, the steel slag and SBS modified asphalt are mixed for 90s using a mixer;

[0056] ​4) After the mixing is completed, two portions of A-Slag, each weighing about 1 kg, are taken out of the mixing pot and placed on a porcelain plate, while being cooled, the A-Slag is dispersed, and the effect is shown in Fig. 2; Figure 3

[0057] 5) The A-slag dispersion is vacuumed using a vacuum negative pressure container, and then the mass m s of water in the vacuum negative pressure container and the A-Slag dispersion is measured, and the mass m w of water in the vacuum negative pressure container is measured, the test is performed twice, the theoretical maximum relative density γ t of the A-slag is calculated, and the average value is taken, and the results are shown in Table 1.

[0058] Table 1 Test results of the theoretical maximum relative density of A-Slag

[0059]

[0060] 6) After the actual measurement of the theoretical maximum relative density of the A-Slag, the effective relative density γ se of the steel slag for the SBS modified asphalt is calculated using formula (2), and the results are shown in Table 2.

[0061] Table 2 Calculation of the effective relative density of steel slag

[0062]

[0063] Another application example of the embodiment is:

[0064] The effective relative density and the bulk volume relative density of 5-10 mm coarse steel slag are determined. The above method is used, and the specific implementation steps are as follows:

[0065] 1) 3 kg of 5-10 mm steel slag is weighed;

[0066] 2) The mass of the asphalt is determined. The asphalt film thickness is 8 μm, and the oil-stone ratio is 4.6% after being calculated, and the mass of the asphalt is weighed according to the mass;

[0067] 3) The steel slag is preheated at 180°C for 4h, the SBS modified asphalt is preheated at 175°C for 3h, and the mixer is preheated to 175°C in advance, and after the preheating is completed, the steel slag and the SBS modified asphalt are mixed using the mixer for 100s;

[0068] 4) After the mixing is completed, two portions of A-Slag, each weighing about 1 kg, are taken out of the mixing pot and placed on a porcelain plate, while being cooled, the A-Slag is dispersed, and the effect is shown in Fig. 2;

[0069] 5) The A-slag dispersion is vacuumed using a vacuum negative pressure container, and then the mass m s ​The mass m of the water in the negative pressure container w The test was conducted twice, the theoretical maximum relative density γ t of A-slag was calculated and the average value was taken, the results are shown in Table 3.

[0070] Table 3 Test results of the theoretical maximum relative density of A-slag

[0071]

[0072] 6) After the measured theoretical maximum relative density of A-slag, the effective relative density γ se of the steel slag under the dosage of the SBS modified asphalt was calculated, the results are shown in Table 4.

[0073] Table 4 Calculation results of the effective relative density of steel slag

[0074]

[0075] The method of the embodiment is clear and definite in principle, relatively simple in calculation, consistent with the actual working condition, and more accurate in measurement results compared with the traditional asphalt impregnation method.

[0076] Embodiment 2

[0077] The embodiment provides a method for determining the bulk volume relative density of steel slag, the effective relative density γ se of the steel slag is obtained by the method of embodiment 1, the apparent relative density γ a of the steel slag is measured according to the method of T0304-2005 in the “Highway Engineering Aggregate Test Procedures” 2005, and then the effective relative density calculation formula of asphalt mixture in the current “Technical Specification for Highway Asphalt Pavement Construction” is used to establish the following equation group:

[0078]

[0079] The γ se and γ a determined above are substituted into the equation group, and the bulk volume relative density γ b , the water absorption rate ω x and the asphalt absorption coefficient C of the steel slag are obtained by solving.

[0080] In one application example of the embodiment, the effective relative density of the steel slag is obtained by the method of the first application example in embodiment 1.

[0081] After the effective relative density γ se of the steel slag is determined, the apparent relative density γ a of the steel slag is measured, and the bulk volume relative density γ b , the water absorption rate ω x and the asphalt absorption coefficient C of the steel slag are obtained by solving the equation group, and the results are shown in Table 5.

[0082] Table 5 Calculation results of the bulk volume relative density of the steel slag

[0083]

[0084] In another application example of the embodiment, the effective relative density of the steel slag is obtained by using the method of the second application example in Embodiment 1.

[0085] The effective relative density γ of the steel slag is determined se Then, the apparent relative density γ of the steel slag is measured a , and the equation set is solved to obtain the bulk volume relative density γ b , water absorption ω x and asphalt absorption coefficient C of the steel slag, and the results are shown in Table 6.

[0086] Table 6 Calculation results of the bulk volume relative density of the steel slag

[0087]

[0088] By using the method of the embodiment, the effective relative density obtained is combined with the apparent relative density to calculate, without using the mesh basket method, and the measurement result is more accurate.

[0089] Although the specific embodiments of the present application are described above with reference to the accompanying drawings, the description is not a limitation on the scope of protection of the present application, and those skilled in the art should understand that various modifications or changes made on the basis of the technical solutions of the present application without creative labor are still within the scope of protection of the present application.

Claims

1. A method for determining the effective relative density of steel slag, characterized in that, Includes the following steps: The mass of asphalt required to completely encapsulate the steel slag is obtained based on the thickness of the asphalt film, and then the asphalt-aggregate ratio is obtained, which is the mass ratio of asphalt to steel slag. Asphalt and steel slag are batched according to the asphalt-aggregate ratio, preheated, and then mixed to obtain steel slag coated with asphalt. The prepared asphalt-coated steel slag is dispersed to obtain a dispersion. After the dispersion is cooled to a set temperature, a set mass of the dispersion is weighed and placed into a negative pressure device. Water is added to the negative pressure device, and then a vacuum is drawn. The theoretical maximum relative density is obtained based on the mass of the negative pressure device and the dispersion in water, and the mass of the negative pressure device in water. The effective relative density of steel slag is obtained based on the theoretical maximum relative density and the oil-stone ratio.

2. The method for determining the effective relative density of steel slag as described in claim 1, characterized in that, Different mass of steel slag coated with asphalt was weighed and placed into a negative pressure device. Water was added to the negative pressure device, and then a vacuum was drawn to obtain multiple theoretical maximum relative density values. The average value was taken as the final theoretical maximum relative density.

3. The method for determining the effective relative density of steel slag as described in claim 1, characterized in that, The set mass range for the dispersed material of steel slag coated with asphalt is 900g-1500g.

4. The method for determining the effective relative density of steel slag as described in claim 1, characterized in that, The asphalt is SBS modified asphalt.

5. The method for determining the effective relative density of steel slag as described in claim 1, characterized in that, The steel slag is preheated at 170℃-180℃ for 3.5-4.5 hours.

6. The method for determining the effective relative density of steel slag as described in claim 5, characterized in that, The steel slag was preheated at 180℃ for 4 hours.

7. The method for determining the effective relative density of steel slag as described in claim 1, characterized in that, Asphalt is preheated at 160℃-180℃ for 2.5-3.5 hours.

8. The method for determining the effective relative density of steel slag as described in claim 7, characterized in that, The asphalt was preheated at 175℃ for 3 hours.

9. The method for determining the effective relative density of steel slag as described in claim 1, characterized in that, Preheat the mixing plant to 170℃-180℃ before adding asphalt and steel slag for mixing.

10. The method for determining the effective relative density of steel slag as described in claim 9, characterized in that, Remove the asphalt-coated steel slag from the mixer and place it in a ceramic pan. After dispersing the asphalt-coated steel slag, cool it to the set temperature, which is 20℃-30℃.

11. The method for determining the effective relative density of steel slag as described in claim 1, characterized in that, The mixing time for steel slag and asphalt is 90s-120s.

12. A method for determining the bulk relative density of steel slag, characterized in that, The effective relative density of steel slag is obtained by using the determination method described in any one of claims 1-11, and the bulk relative density of steel slag is obtained by combining the measured apparent relative density of steel slag.

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