A method for improving the adhesion of aggregate and asphalt interface based on EICP technology

Abstract

The application belongs to the technical field of building materials, and particularly discloses a method for improving the adhesion of aggregate and asphalt based on EICP technology, which comprises the following steps: preparing an EICP treatment solution by mixing a urease solution and a cementing solution; the urease solution is composed of urease and skimmed milk powder, and the cementing solution is composed of urea and calcium acetate; soaking or spraying the aggregate with the EICP treatment solution to obtain modified aggregate; and mixing the modified aggregate with hot asphalt to completely wrap the surface of the modified aggregate with asphalt. The aggregate is treated by the EICP technology, so that calcium carbonate precipitate is induced to be generated on the surface of the aggregate. When the asphalt wraps the aggregate, the calcium carbonate precipitate on the surface of the aggregate increases the roughness of the surface and has calcareous characteristics, thereby enhancing the adhesion of the aggregate and the asphalt. The treatment mode of the EICP treatment solution is regulated according to the acid-base property of the aggregate, so that the adhesion of the aggregate and the asphalt is significantly improved while the treatment time is shortened.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of building materials, and particularly relates to a method for improving the adhesion of aggregate and asphalt based on EICP technology. BACKGROUND

[0002] Early water damage has become one of the main diseases of the highway asphalt pavement, and can cause other pavement problems, seriously affecting the service performance and design life of the pavement. Adhesion reflects the ability of the asphalt film on the aggregate surface to resist damage or peeling, and is a key factor affecting the water stability of asphalt mixture.

[0003] At present, the methods for improving the adhesion between asphalt and aggregate mainly include two types: modification of asphalt and modification of aggregate. In terms of modification of asphalt, one method is to add modifiers to asphalt, such as rubber powder, high molecular polymer, metal soap, surfactant, high molecular anti-peeling agent, silane coupling agent (SCA), etc., to improve the adhesion between asphalt and aggregate, thereby improving the anti-peeling performance of asphalt mixture. For example, adding SCA and titanate coupling agent to asphalt in an appropriate amount can improve the adhesion grade between asphalt and granite from 2 to 5. However, the application of this method is limited by the disadvantages of environmental pollution, poor modification effect and influence on asphalt performance, and therefore is less used at present.

[0004] In terms of aggregate modification, first, alkaline aggregate with good adhesion to asphalt, such as limestone, is selected. Acidic components in asphalt are prone to chemical reaction with alkaline aggregate to generate substances that are difficult to dissolve in water, thereby enhancing the chemical adhesion of the asphalt-aggregate interface. Second, the aggregate is modified using a solution prepared by mixing silane coupling agent (SCA) with distilled water and anhydrous ethanol. Silicon in SCA forms Si-O-Si bonds with silicon on the surface of the aggregate, which is conducive to enhancing the adhesion between the aggregate and asphalt. In addition, Chinese invention patent (CN106587742B) discloses a method for improving the interfacial adhesion between glass aggregate and asphalt by using nano iron oxide. As an alkaline material, nano iron oxide does not change the properties of glass aggregate and is easy to adhere to the surface of glass, increasing the surface roughness and thereby enhancing the interfacial adhesion between glass aggregate and asphalt, improving the utilization rate of glass aggregate, and having good adhesion and durability, while reducing energy consumption and not polluting the environment. Chinese invention patent (CN102515598B) improves the performance of aggregate by forming a two-layer modified film of silica sol and fully hydrated cement on the surface of granite. The inner layer is a silica sol layer with a thickness of 0.10-0.20 mm, and the outer layer is a silica-aluminum-phosphorus gel layer with a thickness of 0.10-0.20 mm. This modified film can wrap the aggregate, allowing it to be tightly combined with water-soluble epoxy resin and phosphoaluminate cement at the same time, thereby reducing the void ratio of the concrete to 10.32%. However, it should be noted that although aluminate coupling agent can improve the adhesion between asphalt and aggregate, it will reduce the rutting resistance of the mixture at high temperatures.

[0005] Inorganic anti-stripping agents, such as lime and cement, can also improve the adhesion between asphalt and aggregate. Lime modifies the surface of the aggregate to form a rough and porous structure, enhancing the porous adsorption and thereby improving the water stability of asphalt mixture. Cement can be mixed into asphalt to form asphalt mortar, which reacts with organic acids in asphalt to generate substances with strong adsorption capacity, thereby improving the water stability of asphalt mixture. In addition, cement can also be used as a filler to mix with aggregate, replacing the use of mineral powder, to further enhance the water stability of asphalt mixture. However, since lime and cement are in powder form, it is difficult to mix uniformly during mixing, which may result in poor anti-stripping effect.

[0006] Therefore, it is necessary to provide an improved method for improving the adhesion between aggregate and asphalt based on EICP technology to solve the above problems. SUMMARY

[0007] The application aims to provide a method for improving the adhesion of aggregate and asphalt based on the EICP technology, which can shorten the treatment time and significantly improve the adhesion of aggregate and asphalt by adjusting the composition and treatment method of the EICP treatment solution, thereby enhancing the water stability of the asphalt mixture, improving the quality of the asphalt pavement and prolonging the service life of the asphalt pavement.

[0008] To achieve the above-mentioned purpose, the application adopts the technical scheme as follows:

[0009] The application provides a method for improving the adhesion of asphalt and aggregate, which comprises the following steps:

[0010] S1, preparing an EICP treatment solution: mixing a urease solution and a cementing solution to obtain the EICP treatment solution; the urease solution is composed of urease and skimmed milk powder, and the cementing solution is composed of urea and calcium acetate;

[0011] S2, soaking or spraying the aggregate with the EICP treatment solution for 1-3 times, and then drying to obtain modified aggregate;

[0012] S3, mixing the modified aggregate with hot asphalt to completely wrap the surface of the modified aggregate with asphalt.

[0013] In the EICP treatment solution, the calcium acetate provides calcium ions for the solution, the urea provides carbonate ions for the solution, the skimmed milk powder can increase the nucleation sites of calcium carbonate precipitation, deionized water is used as the solvent, and the urease is used as the catalyst for the hydrolysis of urea.

[0014] The application treats the aggregate by the EICP technology to induce the formation of a layer of calcium carbonate precipitation on the surface of the aggregate. When the asphalt wraps the aggregate, the calcium carbonate precipitation on the surface of the aggregate increases the roughness of the surface, thereby enhancing the adhesion with the asphalt. Meanwhile, the calcium carbonate generated on the surface of the aggregate has calcium characteristics, which helps to improve the adhesion of the aggregate and the asphalt. The calcium carbonate precipitation on the surface of the aggregate also enhances the non-polar performance of the limestone aggregate (limestone), promotes the combination between the aggregate and the asphalt through covalent bond, and further enhances the adhesion between the two, thereby improving the water stability of the asphalt mixture.

[0015] Further, each soaking treatment refers to immersing the surface of the aggregate in the EICP treatment solution, and the mineralization treatment is completed after 48±5h.

[0016] Each spraying treatment refers to spraying every 8h within 24h. Usually, after the final spraying, 24h is placed, then the surface invalid precipitation is removed by cleaning, and then dried.

[0017] Further, the soaking or spraying treatment is preferably carried out at 25℃.

[0018] Further, the aggregate is one or more of sandstone, diabase, limestone; the application can be preferably used for modifying acidic and neutral aggregate, the acid-base and surface roughness of the modified aggregate can be optimized by EICP technology treatment, the adhesion of the aggregate and asphalt is enhanced, and then the water stability of the asphalt mixture is enhanced, the quality of the asphalt pavement is improved, and the service life of the asphalt pavement is prolonged. When the aggregate is alkaline aggregate, spraying treatment is adopted, which is helpful to improve the adhesion of the aggregate and asphalt.

[0019] When the aggregate is sandstone, the aggregate is subjected to 1 time of immersion treatment or 3 times of spraying treatment by the EICP treatment liquid;

[0020] When the aggregate is diabase, the aggregate is subjected to 1-3 times of immersion treatment or 3 times of spraying treatment by the EICP treatment liquid;

[0021] When the aggregate is limestone, the aggregate is subjected to 1 time of immersion treatment or 2-3 times of spraying treatment by the EICP treatment liquid.

[0022] Further, in the EICP treatment liquid, the concentrations of urease and skimmed milk powder are 0.684±0.1 g / L and 3±0.5 g / L respectively, and the molar ratio of urea and calcium acetate is 1: (1-1.2), preferably 1:1.

[0023] Further, in the EICP treatment liquid, the concentrations of urea and calcium acetate are 33.750±0.5 g / L and 99.093±0.5 g / L respectively.

[0024] Further, in step S2, the mass ratio of the aggregate and the EICP treatment liquid in each spraying treatment is (50-60):10, preferably 56:10.

[0025] Further, in step S3, the temperature of the hot asphalt is 135-140℃, preferably the asphalt is heated in an oven at 135-140℃ for 40-50 minutes.

[0026] Further, step S3 specifically comprises: immersing the modified aggregate in asphalt at 135-140℃ for 40-50s, so that the surface of the aggregate is completely wrapped by the asphalt film, the excess asphalt is flowed off, and the room temperature is cooled for 10-20min.

[0027] Further, before the aggregate is soaked or sprayed, according to the requirements of the method of the Highway Engineering Asphalt and Asphalt Mixture Test Regulations (JTGE 20-2011), the aggregate of 13.2-16mm is selected, ultrasonic cleaning is carried out using distilled water to remove dust on the surface of the aggregate, and drying is carried out at 100°C until the mass no longer changes. The purpose of washing is to clean the invalid sediment on the surface of the aggregate, and the purpose of drying is to dry the moisture on the surface of the aggregate.

[0028] Compared with the existing modified aggregate for improving the adhesion between asphalt and aggregate, the advantages of the present application are:

[0029] 1、The present application obtains modified aggregate by optimizing the composition and treatment method of the EICP treatment solution, the calcium carbonate sediment generated on the surface of the aggregate can enhance the adhesion between asphalt and aggregate, improve the water stability of asphalt mixture, and prolong the service performance of asphalt pavement. The treatment method of the present application is simple, low in energy consumption, free of environmental pollution, has remarkable adhesion improvement effect, and does not cause negative effects on the performance of asphalt. It can effectively improve the durability of the pavement, and has wide application prospect.

[0030] 2、The present application modifies the aggregate by the EICP treatment solution, and it is found that the treatment effect of this method is closely related to the acid-base property of the aggregate, therefore, according to the acid-base property of the aggregate, the preferred treatment method is provided, so that the adhesion between asphalt and aggregate can be significantly improved while the treatment time is shortened. The present application has wide application range and is convenient for popularization and application. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 Fig. 2 is a comparison of the actual objects of the unmodified sandstone and the sandstone modified by Example 1 after the water boiling test, wherein (a) and (b) are respectively the unmodified sandstone and the sandstone modified by Example 1 after the water boiling test;

[0032] Figure 2 Fig. 3 is a comparison of the actual objects of the unmodified diabase and the diabase modified by Example 2 after the water boiling test, wherein (a) and (b) are respectively the unmodified diabase and the diabase modified by Example 2 after the water boiling test;

[0033] Figure 3 Fig. 4 is a comparison of the actual objects of the unmodified limestone and the limestone modified by Example 3 after the water boiling test, wherein (a) and (b) are respectively the unmodified limestone and the limestone modified by Example 3 after the water boiling test;

[0034] Figure 4 Fig. 5 is a comparison of the actual objects of the sandstone soaked for 2 times and 3 times from left to right;

[0035] Figure 5 Fig. 6 is a comparison of the actual objects of the diabase soaked for 2 times and 3 times from left to right;

[0036] Figure 6 Fig. 7 is a comparison of the actual objects of the limestone soaked for 2 times and 3 times from left to right;

[0037] Figure 7 From left to right are the physical pictures of sandstone spray treatment 1, 2 and 3 times, respectively;

[0038] Figure 8 From left to right are the physical pictures of diabase spray treatment 1, 2 and 3 times, respectively;

[0039] Figure 9 From left to right are the physical pictures of limestone spray treatment 1, 2 and 3 times, respectively. DETAILED DESCRIPTION

[0040] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions in the present application are described clearly and completely below. Obviously, the described embodiments are some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0041] The urea and calcium acetate used in the following test are all analytically pure reagents. The urease is provided by Shanghai Rugi Biological Reagent Company, and the urease is derived from Canavalia ensiformis with an activity of 150 U / mg, and is generally stored at 2-8°C.

[0042] Example 1

[0043] (1) Take sandstone aggregate with a particle size of 13.2-16 mm, clean the surface dust by ultrasonic cleaning with distilled water, dry at 100±5°C until the mass no longer changes, and store for use;

[0044] (2) The EICP treatment solution is mixed by urease solution and cementing solution, and the cementing solution is prepared by urea-calcium acetate. The urease solution is prepared by dissolving urease and skimmed milk powder, and the skimmed milk powder is used to provide nucleation sites. The cementing solution is prepared by mixing urea (CO(NH2)2) and calcium acetate monohydrate (C4H6O4Ca·H2O) at a molar ratio of 1:1. In the finally obtained EICP treatment solution, the concentrations of urease, skimmed milk powder, urea and calcium acetate are 0.684 g / L, 3 g / L, 33.750 g / L and 99.093 g / L, respectively;

[0045] (3) Soak the aggregate in step (1) in the EICP treatment solution for 48 h (the mass ratio of aggregate to EICP treatment solution is 1.99:1), so that calcium carbonate precipitate is formed on the surface of the aggregate, and then dry at 50°C for 8 h to obtain modified aggregate;

[0046] (4) Preheat the unmodified aggregate and the modified aggregate, respectively, and immerse them in 140°C bitumen for 45 s, so that the surface of the aggregate is completely wrapped by bitumen film, the excess bitumen is flowed away, and then cool at room temperature for 15 min;

[0047] (5) Referring to the method of the "Test Procedure for Asphalt and Asphalt Mixtures in Highway Engineering" (JTGE 20-2011), the aggregate coated with asphalt is immersed in water and kept in a slightly boiling state. After immersion for 3 minutes, the aggregate is taken out of the water and the degree of asphalt film peeling is observed to evaluate its adhesion grade.

[0048] like Figure 1 As shown in (a), the water boiling test results indicate that the asphalt film on the surface of the unmodified sandstone aggregate partially detaches, while some areas remain on the stone surface. The percentage of detached area is greater than 30%, and its adhesion level is determined to be level 2. Figure 1 As shown in (b), the modified sandstone aggregate has an intact asphalt film on its surface, and its adhesion level is determined to be 5.

[0049] Example 2

[0050] (1) Take diabase aggregate with a particle size of 13.2-16 mm, ultrasonically clean it with distilled water to remove surface dust, dry it at 100±5°C until the quality no longer changes, and store it for later use.

[0051] (2) The EICP treatment solution was prepared by mixing a urease solution and a cementing solution, with the cementing solution being prepared using urea-calcium acetate. The urease solution was prepared by dissolving urease and skim milk powder, with the skim milk powder providing nucleation sites. The cementing solution was prepared by mixing urea (CO(NH2)2) and calcium acetate monohydrate (C4H6O4Ca·H2O) in a 1:1 molar ratio. In the final EICP treatment solution, the concentrations of urease, skim milk powder, urea, and calcium acetate were 0.684 g / L, 3 g / L, 33.750 g / L, and 99.093 g / L, respectively.

[0052] (3) Soak the aggregate from step (1) in EICP treatment solution for 48 hours (mass ratio of aggregate to EICP treatment solution is 1.99:1) to form calcium carbonate precipitate on the surface of the aggregate, and then dry it at 50°C for 8 hours to obtain modified aggregate;

[0053] (4) Preheat the unmodified aggregate and the modified aggregate, immerse them in 140°C asphalt for 45s respectively, so that the surface of the aggregate is completely covered by the asphalt film, drain off the excess asphalt, and cool at room temperature for 15min.

[0054] (5) Referring to the method of the "Test Procedure for Asphalt and Asphalt Mixtures in Highway Engineering" (JTGE 20-2011), the aggregate coated with asphalt is immersed in water and kept in a slightly boiling state. After immersion for 3 minutes, the aggregate is taken out of the water and the degree of asphalt film peeling is observed to evaluate its adhesion grade.

[0055] like Figure 2As shown in (a), the water boiling test results indicate that the asphalt film on the surface of the unmodified diabase aggregate partially detaches, while some areas remain on the aggregate surface. The percentage of detached area is less than 30%, and its adhesion level is determined to be level 3. Figure 2 As shown in (b), the modified diabase aggregate has an intact asphalt film on its surface, and its adhesion level is determined to be 5.

[0056] Example 3

[0057] (1) Take limestone aggregate with a particle size of 13.2-16 mm, ultrasonically clean it with distilled water to remove the dust on the surface, dry it at 100±5°C until the quality no longer changes, and store it for later use.

[0058] (2) The EICP treatment solution was prepared by mixing a urease solution and a cementing solution, with the cementing solution being prepared using urea-calcium acetate. The urease solution was prepared by dissolving urease and skim milk powder, with the skim milk powder providing nucleation sites. The cementing solution was prepared by mixing urea (CO(NH2)2) and calcium acetate monohydrate (C4H6O4Ca·H2O) in a 1:1 molar ratio. In the final EICP treatment solution, the concentrations of urease, skim milk powder, urea, and calcium acetate were 0.684 g / L, 3 g / L, 33.750 g / L, and 99.093 g / L, respectively.

[0059] (3) Soak the aggregate from step (1) in EICP treatment solution for 48 hours (mass ratio of aggregate to EICP treatment solution is 1.99:1) to form calcium carbonate precipitate on the surface of the aggregate, and then dry it at 50°C for 8 hours to obtain modified aggregate;

[0060] (4) Preheat the unmodified aggregate and the modified aggregate, immerse them in 140°C asphalt for 45s respectively, so that the surface of the aggregate is completely covered by the asphalt film, drain off the excess asphalt, and cool at room temperature for 15min.

[0061] (5) Referring to the method of the "Test Procedure for Asphalt and Asphalt Mixtures in Highway Engineering" (JTGE 20-2011), the aggregate coated with asphalt is immersed in water and kept in a slightly boiling state. After immersion for 3 minutes, the aggregate is taken out of the water and the degree of asphalt film peeling is observed to evaluate its adhesion grade.

[0062] like Figure 3 As shown in (a), the water boiling test results indicate that the asphalt film on the surface of the unmodified limestone aggregate partially detaches, while some areas remain on the aggregate surface. The percentage of detached area is less than 10%, and its adhesion level is determined to be level 4. Figure 3 As shown in (b), the modified diabase aggregate has an intact asphalt film on its surface, and its adhesion level is determined to be 5.

[0063] Continue to increase the number of immersion treatments for each of the three aggregates in Examples 1-3 to study the effect of the number of immersion treatments on adhesion, as shown in Table 1 and Figures 4-6 As shown in Table 1 and

[0064] Table 1 Adhesion grades of sandstone, diabase and limestone before and after modification (immersion treatment)

[0065]

[0066] According to the experimental analysis and comparison of the experimental results of sandstone and limestone, it can be seen that the EICP treatment of acidic aggregate (sandstone) can enhance the adhesion of aggregate and asphalt, but excessive treatment will lead to too much calcium carbonate on the surface of the aggregate, which will reduce the effect; the limestone is an alkaline aggregate, which has good adhesion to asphalt, and the calcium carbonate generated after excessive EICP treatment is not as firm as the aggregate itself, which reduces the adhesion to asphalt. The diabase is a neutral aggregate, and the adhesion to asphalt is stronger after EICP treatment.

[0067] Experimental results of EICP treatment liquid spraying type treatment of aggregate

[0068] The difference between the spraying treatment and Examples 1-3 is that step (3) is changed to: spray the aggregate with EICP treatment liquid every 8 hours within 24 hours, i.e. spray 3 times within 24 hours (the mass ratio of aggregate to EICP treatment liquid for each spraying treatment is 56:10), and then place it in room temperature for 24 hours after the spraying within 24 hours is completed. After 24 hours, remove the aggregate, wash off the ineffective precipitate on the surface, and dry it for use. Among them, the 24-hour spraying period corresponds to 1 treatment in Table 2, and 2 treatments require another 24-hour spraying.

[0069] Table 2 Adhesion grades of sandstone, diabase and limestone before and after modification (spraying treatment)

[0070]

[0071] By analyzing the experimental results of spraying type compared with immersion type, when EICP is sprayed for 1 time, the adhesion of the aggregate is not obviously improved, and when it is sprayed for 2 or 3 times, the adhesion of the aggregate is obviously improved. This is because the amount of calcium carbonate generated by the spraying type treatment is less and evenly distributed, so the effect of 1 time treatment is not obvious, and the amount of calcium carbonate generated by 2 or 3 times treatment is more, but it does not have a negative impact on the adhesion of the aggregate. It can also be seen from Table 2 that the spraying treatment effect is less affected by the acidity and alkalinity of the aggregate. The calcium carbonate generated by the immersion type is mostly formed on the upper surface of the aggregate, because the calcium carbonate is affected by the weight and mostly falls on the upper surface of the aggregate, which leads to uneven distribution of calcium carbonate, and a large amount of calcium carbonate accumulates on one side of the aggregate, thereby reducing the adhesion of the aggregate.

[0072] In summary, the aggregate of the present application is treated by EICP, and the surface forms rough calcium carbonate precipitate, which enhances the adhesion with asphalt. The calcareous properties of calcium carbonate generated on the surface of aggregate can improve the adhesion of aggregate and asphalt. The calcium carbonate precipitate on the surface of aggregate enhances the non-polar properties of limestone aggregate, enhances the combination of aggregate and asphalt through covalent bond with asphalt (non-polar), and further enhances the adhesion of aggregate and asphalt. The present application can greatly improve the adhesion of acidic aggregate and neutral aggregate, and also has a promotion effect on the adhesion of alkaline aggregate and asphalt. The method can effectively improve the water stability of asphalt mixture and prolong the service life of asphalt pavement.

[0073] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of each embodiment of the present application.

Claims

1. A method of improving the adhesion of an asphalt to aggregate interface, characterized by, The method comprises the following steps: S1, preparing an EICP treatment solution: mixing a urease solution and a cementing solution to obtain the EICP treatment solution; the urease solution is composed of urease and skimmed milk powder, and the cementing solution is composed of urea and calcium acetate; In the EICP treatment solution, the concentrations of the urease and the skimmed milk powder are 0.684±0.1 g / L and 3±0.5 g / L respectively, and the concentrations of the urea and the calcium acetate are 33.750±0.5 g / L and 99.093±0.5 g / L respectively; S2, soaking or spraying the aggregate with the EICP treatment solution for 1-3 times, and then drying to obtain modified aggregate; The average particle size of the aggregate is 13.2-16 mm, and the aggregate is diabase or limestone; Each time of the soaking treatment refers to immersing the aggregate surface in the EICP treatment solution, and completing the mineralization treatment after 48±5 h; each time of the spraying treatment refers to spraying every 8 h within 24 h, and the spraying period of 24 h corresponds to 1 time of the spraying treatment; the mass ratio of the aggregate to the EICP treatment solution in each time of the spraying treatment is 56:10; When the aggregate is diabase, the aggregate is soaked or sprayed with the EICP treatment solution for 1-3 times; the diabase is neutral aggregate; When the aggregate is limestone, the aggregate is soaked or sprayed with the EICP treatment solution for 1-3 times; the limestone is alkaline aggregate; S3, mixing the modified aggregate with hot asphalt to completely wrap the surface of the modified aggregate with asphalt.

2. The method of improving the adhesion of asphalt to aggregate interface of claim 1, wherein, In S3, the temperature of the hot asphalt is 135-140°C.

3. The method of improving the adhesion of asphalt to aggregate interface of claim 2, wherein, The asphalt is heated in an oven at 135-140°C for 40-50 min.

4. The method of improving the adhesion of asphalt to aggregate interface of claim 1, wherein, S3 specifically comprises: immersing the modified aggregate in asphalt at 135-140°C for 40-50 s to completely wrap the surface of the aggregate with asphalt film, flowing off the excess asphalt, and cooling at room temperature for 10-20 min.

5. The method of improving the adhesion of asphalt to aggregate interface of claim 1, wherein, In S2, the aggregate is washed with clean water before use, and then dried at 100±5°C.

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