Wet mixing test method for measuring skeleton void rate of flowing mucilage asphalt mixture

Abstract

The invention belongs to the technical field of road traffic, and particularly relates to a wet mixing test method for measuring the skeleton void rate of a flowing mortar asphalt mixture. According to the method disclosed by the invention, a small amount of asphalt is added in the aggregate mixing process, so that the coarse and fine aggregates have certain adhesion capacity without influencing the arrangement of the coarse and fine aggregates, a certain lubrication effect is provided for the surfaces of the coarse aggregates with relatively large particles, and the influence caused by friction of the surfaces of the coarse aggregates is reduced; and finally, uniformly mixing the aggregate and the asphalt, pouring the mixture into a mold according to a set weight, and compacting by using a Marshall compactor or a rotary compactor, so that errors caused by human factors are reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of road traffic, and particularly relates to a wet mixing test method for measuring the voids in the aggregate of fluid mastic asphalt mixture. Background Art

[0002] In the field of roads, with the development of the economy, the proportion of heavy vehicles such as large buses and trucks far exceeds the design at the beginning of road construction, resulting in frequent occurrence of many asphalt pavement diseases nowadays, such as cracking, rutting, bumping, potholes and other phenomena, which seriously affect the driving comfort and even safety. Therefore, how to shorten the maintenance construction time and extend the service life of roads has become an urgent problem to be solved in the current road field.

[0003] According to the existing research on fluid mastic asphalt (FMA) mixture, due to its skeleton-super dense structure with an internal void ratio (VV) close to zero, FMA has significant advantages in aspects such as fatigue resistance, water damage resistance, aging resistance, and low temperature cracking resistance. Therefore, FMA can not only be used for road maintenance to extend the life of existing pavements; it can also be used in each layer of newly built, rebuilt and expanded long-life pavement structures, can be used as a functional layer of the pavement structure, or can be used as the pavement surface layer to achieve skid resistance and skid durability.

[0004] The FMA mixture is designed by the mastic flow for filling method (MaFF). Based on this, how to accurately measure the voids in the aggregate (V ag ) of different types of FMA skeletons is crucial. With accurate V ag can accurately design FMA mixtures that meet the index requirements such as asphalt-aggregate ratio and texture depth required by the project. Currently, the only method for testing V ag is the dry ramming method, and this method has the following deficiencies: 1) Since the dry ramming method only manually mixes the aggregates evenly and then pours them into a measuring cylinder without adding other materials to prevent the fine aggregates from moving in the voids of the coarse aggregates, and in addition, after the aggregates are poured into the measuring cylinder, manual ramming is still required, which is very likely to cause the fine aggregates to flow to the bottom of the measuring cylinder due to lack of restraint, that is, segregation occurs, resulting in a large deviation in the calculation of V ag ; 2) The dry ramming method measures V agNo asphalt was added during this process. During the compaction process, due to the friction on the surface of the coarse aggregates with larger particles, the coarse aggregates did not reach the ideal compaction state. 3) The dry ramming method involves manually mixing the aggregates and manually using an iron rod to ram and compact them. Manual operation cannot ensure that the mixing degree of the aggregates and the ramming force, depth, etc. are consistent each time, thus very easily causing human errors, and the human errors caused will also have a greater impact on the test results. 4) After all the aggregates are poured into the measuring cylinder and the ramming is completed, it is necessary to use an iron rod to scrape off the aggregates above the measuring cylinder mouth. During the scraping process, due to the friction between the aggregates and the iron rod, even though objectively the aggregates are already flush with the measuring cylinder mouth, continued scraping will still bring out aggregates due to friction, resulting in the subjective perception that the aggregates are not yet flush with the measuring cylinder mouth, making the weight smaller, thus causing errors.

[0005] In addition, compared with the actual forming process of FMA, the lubricating effect of asphalt at high temperature is missing. In addition, the compaction work of various forming methods is different, and the similarity of simulating the on-site compaction process is also inconsistent. Therefore, in many aspects, the measured V ag in the indoor test is different from the actual V ag of the FMA pavement after on-site compaction, resulting in a large error, which may cause the FMA design result to be inconsistent with the actual FMA pavement. Summary of the Invention

[0006] To solve the shortcomings and deficiencies of the prior art, the purpose of the present invention is to provide a wet mixing test method for measuring the void ratio of the skeleton of flowing mortar asphalt mixture. This method adds a small amount of asphalt to the tested V ag aggregates, which not only simulates the actual pavement forming process to provide lubrication during high-temperature forming, but also enables a certain adhesion between the coarse and fine aggregates, significantly reducing the segregation phenomenon, and at the same time does not affect the arrangement between the coarse and fine aggregates. In addition, the compaction process uses a Marshall compactor or a gyratory compactor for standard operation, reducing human operation errors, so that the accuracy of the measured V ag has been greatly improved.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] A wet mixing test method for measuring the void ratio of the skeleton of flowing mortar asphalt mixture, the method comprising the following steps:

[0009] (1) Select the gradation and weigh each grade of aggregates, and weigh asphalt accounting for 2% of the aggregate weight; according to the asphalt viscosity-temperature curve obtained from the asphalt rotational viscosity test, determine the temperature T0 °C when the asphalt viscosity is 0.28 Pa·s;

[0010] Heat the asphalt, aggregates, and the tools required for the test in sections. The heating temperature in the previous period is T0 - 20°C, and the heating temperature in the last hour is T0°C. The purpose is to prevent the accelerated aging of the asphalt caused by long-term high-temperature conditions.

[0011] (2) Pour the heated aggregates into the mixer and mix them. After the aggregates are evenly mixed, add the asphalt and continue to mix thoroughly; the mixing temperature needs to be maintained at T0 + 10°C to prevent excessive temperature loss during the opening and closing of the mixing pot, which may lead to poor adhesion of the asphalt to the aggregates.

[0012] (3) According to the weight of one specimen, add the aggregates mixed with the asphalt into the mold and tamp them.

[0013] (4) After tamping, place the mold in the Marshall compactor or the gyratory compactor and compact it according to the set number of compaction times; after compaction, take out the aggregates, let them cool naturally, and then demold to obtain the specimen.

[0014] (5) Measure the height of the specimen.

[0015] (6) According to the measured height of the specimen, calculate the volume of the specimen through the cylindrical volume formula, and then divide the weight of the specimen by the volume to obtain the compacted density of the specimen; finally, the void ratio V of the specimen's skeleton can be calculated through Equation (1). ag ;

[0016]

[0017] In the formula:

[0018] V ag —— represents the void ratio of the aggregate skeleton (%).

[0019] ρ1 —— represents the compacted density of the aggregate (g / cm 3 ).

[0020] ρ2 —— represents the combined bulk density of the aggregate (g / cm 3 ).

[0021] In the method of the present invention, a small amount of asphalt is added during the mixing of the aggregates, so that the coarse and fine aggregates have a certain adhesion ability but do not affect the arrangement between the coarse and fine aggregates, and provide a certain lubricating effect on the surface of the larger coarse aggregates, reducing the influence caused by the surface friction of the coarse aggregates; finally, the aggregates and asphalt are evenly mixed and poured into the mold according to the set weight, and the Marshall compactor or the gyratory compactor is used for compaction to reduce the error caused by human factors.

[0022] Preferably, T0 in step (1) is 200°C; the asphalt is ultra-high viscosity modified asphalt or SBS modified asphalt.

[0023] Preferably, in step (2), the aggregate is poured into the mixer and mixed for 90 s, and then mixed for another 90 s after adding asphalt.

[0024] Preferably, the specific steps of step (3) are as follows: Weigh the aggregate mixed with asphalt by half of the weight of one specimen, and add it to the mold. After placing it stably, use a thin iron rod to tamp around the mold 15 times and tamp in the middle 10 times. Then add the remaining weight of the aggregate to make the total weight reach the preset value, with an upper and lower limit of no more than 5 g. Then use the thin iron rod to tamp around the mold 15 times and tamp in the middle 10 times; The weight of one specimen is preferably set to 1100 - 1600 g.

[0025] Preferably, before compaction in step (4), level the surface of the aggregate after tamping, and place a round kraft paper to prevent the aggregate from being taken out during the compaction process.

[0026] Preferably, in step (4), the number of compaction times is 75 - 200 times, and the aggregate is placed in a cool place to naturally cool for 24 h before demolding.

[0027] Preferably, for measuring the height of the specimen in step (5): When a Marshall compactor is used in step (4), use a vernier caliper to measure the height of the demolded specimen from four directions of front, back, left, and right, and finally take the average value as the height of the specimen (if the difference between the maximum and minimum measured heights is greater than 1 mm, the specimen needs to be remolded); When a gyratory compactor is used in step (4), directly export the height of the molded specimen from the gyratory compactor.

[0028] Preferably, the calculation steps for the synthetic bulk specific gravity of the aggregate in step (6): First, measure the bulk specific gravity of each size fraction of the aggregate according to Method T0304 in the "Specifications for Aggregate Tests of Highway Engineering" (JTG 3432 - 2024) (Formula T0304 - 6), then calculate the content of each size fraction of the aggregate, and finally calculate the synthetic bulk specific gravity of the aggregate according to Formula T0304 - 9 in the specification.

[0029] Preferably, considering the boundary effect influence caused by the small volume of the tested specimen, and when forming a complete flowing mastic asphalt mixture, the aggregate will be more evenly and densely distributed. Therefore, the V ag calculated in step (6) needs to be multiplied by the reduction coefficient α before being used as the V ag in the mixture design, where α = 0.70 - 0.90.

[0030] More preferably, when a Marshall compactor is used in step (4), the V ag calculated in step (6) is directly multiplied by the reduction coefficient α and used as the V ag; When a gyratory compactor is used in step (4), the V calculated in step (6) ag is multiplied by the conversion coefficient β = 1.06 as the measured V obtained from the final test ag , and the measured V ag is then multiplied by the reduction coefficient α before it can be used as the V in mixture design ag .

[0031] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0032] (1) Compared with the dry compaction method, the method of adding a small amount of asphalt proposed by the present invention can effectively prevent the fine aggregate from sinking to the bottom of the container and causing segregation, so that the error in calculating the compacted density of the aggregate can be greatly reduced;

[0033] (2) Compared with the dry compaction method, the method of adding a small amount of asphalt proposed by the present invention can effectively reduce the influence brought by the surface friction of the coarse aggregate with larger particles. The asphalt provides a certain lubricating effect on the surface of the coarse aggregate, making the compaction process of the aggregate more in line with the ideal situation;

[0034] (3) The dry compaction method only regards the state after ramming as the compacted state of the aggregate, which obviously does not meet the requirements of compaction. Therefore, the method proposed by the present invention adds a step of using an instrument for compaction, making the compacted state of the aggregate closer to the actual situation;

[0035] (4) Except for the manual operation during loading, other operations such as mixing and compaction in the method proposed by the present invention are completed by instruments. In addition to saving the energy spent on operation, it can also greatly reduce the human subjective error brought by human operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a sectional view of a Marshall specimen formed when n = 0.6.

[0037] Figure 2 It is a sectional view of a Marshall specimen formed when n = 1.2.

[0038] Figure 3 It is a sectional view of a Marshall specimen formed when n = 2.1. DETAILED DESCRIPTION OF THE INVENTION

[0039] The present invention will be further described in detail below in conjunction with the embodiments and the drawings, but the embodiments of the present invention are not limited thereto. The raw materials involved in the present invention can be directly purchased from the market. For the process parameters not specifically noted, conventional techniques can be referred to.

[0040] The present invention provides a wet mixing test method for measuring the voids in the mineral aggregate of flowing mastic asphalt mixture. The present invention has conducted an optimization experiment on the asphalt addition amount in the method, specifically as follows:

[0041] In this test, the asphalt added is ultra-high viscosity asphalt. The weight of each specimen is set to 1100 g, and it is compacted using a Marshall compactor with 75 compaction times; the test is divided into four groups, and in step (2), asphalt accounting for 1%, 2%, 3%, and 4% of the aggregate weight is added respectively (i.e., the asphalt-to-aggregate weight ratios are 1%, 2%, 3%, and 4%);

[0042] (1) According to the asphalt viscosity-temperature curve obtained from the asphalt rotational viscosity test, the temperature of 200 °C when the asphalt viscosity is 0.28 Pa·s is determined as the test mixing temperature;

[0043] Put the asphalt, aggregate, and tools required for the test into the oven and heat for 3 - 4 hours. The heating temperature in the previous period is 180 °C, and the heating temperature in the last hour is 200 °C, aiming to prevent the accelerated aging of the asphalt caused by long-term high-temperature state;

[0044] (2) Pour the heated aggregate into the mixer and mix for 90 s to make the aggregate evenly mixed; pause the mixing, add the asphalt, and continue to mix for 90 s until evenly mixed; use a shovel to appropriately stir the mixed mixture to prevent the mixture at the bottom of the mixing pot from not being fully and evenly mixed; the mixing temperature needs to be maintained at 210 °C to prevent the excessive temperature loss during the opening and closing process of the mixing pot from resulting in poor adhesion of the asphalt to the aggregate;

[0045] (3) According to the weight of one specimen, add the aggregate mixed with the asphalt into the mold for ramming; the preferred ramming method is: place the mold on the scale, tare it, then scoop out half of the weight of one specimen of the aggregate into the mold with a small cup, remove the mold and place it steadily on the ground, ram 15 times along the perimeter of the mold with a thin iron rod, ram 10 times in the middle, then put the mold back on the scale, and finally add the remaining weight of the aggregate so that the total weight reaches the preset value of 1100 g, and then ram 15 times along the perimeter of the mold with a thin iron rod and ram 10 times in the middle;

[0046] (4) Level the surface of the rammed aggregate, place a circular kraft paper on it to prevent the aggregate from being taken out during the compaction process; place the treated mold in the Marshall compactor and compact it according to the set number of times; take out the compacted aggregate, place it in a cool place to cool naturally and then demold to obtain the specimen;

[0047] (5) Use a vernier caliper to measure the height of the demolded specimen from four directions: front, back, left, and right, and finally take the average value as the height of the specimen (if the difference between the maximum and minimum measured heights is greater than 1 mm, the specimen needs to be remolded);

[0048] (6) Calculate the volume of the specimen through the cylinder volume formula according to the measured height of the specimen, and then obtain the compacted density of the specimen by dividing the weight of the specimen by the volume; finally, the skeleton void ratio V of the specimen can be calculated through Equation (1). ag ;

[0049]

[0050] In the formula:

[0051] V ag —— represents the skeleton void ratio of the aggregate (%).

[0052] ρ1—— represents the compacted density of the aggregate (g / cm 3 ).

[0053] ρ2—— represents the synthetic bulk density of the aggregate (g / cm 3 ).

[0054] (7) Analyze the calculated V ag and the phenomena observed during the test process in step (3).

[0055] The test results are shown in Table 1. When the asphalt is 2% of the weight of the aggregate, the measured results are the most ideal. And according to the analysis of the phenomena observed during the test process in step (3): when the asphalt is 1% of the weight of the aggregate, some of the aggregate surfaces are not coated with asphalt, indicating that adding 1% of asphalt cannot achieve the core idea of the present invention; when the asphalt is 3% and 4% of the weight of the aggregate, although the aggregate surfaces are completely coated with asphalt, in addition to the asphalt adhered to the aggregate surfaces, there is still more free asphalt. Therefore, the excess asphalt may play an expanding role in the volume of the specimen during the molding of the specimen, resulting in a larger measured volume of the specimen, and the calculated V ag is also larger; while when the asphalt is 2% of the weight of the aggregate, not only are the aggregate surfaces completely coated with asphalt, but almost no excess free asphalt can be seen, which is very consistent with the core idea of the present invention. Therefore, it is most appropriate to add 2% of asphalt by weight of the aggregate in the wet mixing test method of the present invention.

[0056] Table 1 V measured under different asphalt-aggregate ratios (weight ratio of asphalt to aggregate) ag

[0057]

[0058] Example 1:

[0059] This test is carried out through the Talbol formula Determine the gradation. The passing rate of each size aggregate will change with the change of the exponent n value. When calculating the passing rate, the part below 0.075mm is removed, and the remaining part is redistributed according to the proportion. Then, calculate the percentage content of each size aggregate. Multiply the total weight by the content percentage to obtain the weight of each size aggregate.

[0060] In this example, the gradation composed when the n value is 0.6 is adopted, the maximum nominal size is 9.5mm, the passing rate of each size aggregate is shown in Table 2, and the content is shown in Table 3. The aggregate is diabase, with a particle size range of 0.075mm to 13.2mm; the asphalt used is ultra-high viscosity modified asphalt; the weight of each specimen is set to 1100g; a Marshall compactor is selected for compaction during the compaction process, and the compaction times are 75 times.

[0061] The method for measuring the skeleton void ratio is as follows:

[0062] (1) According to the asphalt viscosity-temperature curve obtained from the asphalt rotational viscosity test, determine that the temperature of 200°C when the asphalt viscosity is 0.28 Pa·s is the test mixing temperature;

[0063] Put the test tools such as asphalt, aggregate, and mold into the oven and heat for 3 - 4 hours. The heating temperature in the previous period is 180°C, and the heating temperature in the last hour is 200°C. The purpose is to prevent the aging of asphalt from being aggravated due to long-term high-temperature state;

[0064] (2) Pour the heated aggregate into the mixer and mix for 90s to make the aggregate evenly mixed; pause the mixing, add 2% asphalt, and continue to mix for 90s until evenly mixed; use a shovel to stir the mixed mixture appropriately to prevent the mixture at the bottom of the mixing pot from not being fully mixed evenly; the mixing temperature needs to be maintained at 210°C to prevent the temperature from dropping too much during the opening and closing process of the mixing pot, resulting in poor adhesion of asphalt to the aggregate.

[0065] (3) Place the mold on the scale, tare it, then scoop out half of the weight of a specimen's aggregate into the mold with a small cup. Remove the mold and place it steadily on the ground. Insert a thin iron rod along the perimeter of the mold 15 times and in the middle 10 times. Then, put the mold back on the scale and finally add the remaining weight of the aggregate so that the total weight reaches the preset value of 1100g, with an upper and lower limit of no more than 5g. Then, insert the thin iron rod along the perimeter of the mold 15 times and in the middle 10 times;

[0066] (4) Level the surface of the aggregate after ramming, and place a circular kraft paper on it to prevent the aggregate from being taken out during the compaction process;

[0067] (5) Place the processed mold in the Marshall compactor and compact it according to the set number of 75 times;

[0068] Take out the aggregate after compaction is completed, place it in a cool place and let it cool naturally for 24h before demolding;

[0069] (6) Use a vernier caliper to measure the height of the specimen after demolding from four directions: front, back, left, and right. Finally, take the average value as the height of the specimen. If the difference between the maximum and minimum measured heights is greater than 1 mm, the specimen needs to be remolded.

[0070] (7) According to the measured height, calculate the volume of the specimen through the cylindrical volume formula. Then, divide the weight of the specimen by the volume to obtain the compacted density of the specimen. Finally, the skeleton void ratio V of the specimen can be calculated through Equation (1). ag 。

[0071]

[0072] In the formula:

[0073] V ag —— represents the skeleton void ratio of the aggregate (%).

[0074] ρ1 —— represents the compacted density of the aggregate (g / cm 3 );

[0075] ρ2 —— represents the combined bulk specific gravity of the aggregate (g / cm 3 );

[0076] The test results are shown in Table 4.

[0077] Example 2:

[0078] In this test, the gradation is determined through the Talbol formula . The passing rate of each size fraction of the aggregate will change with the change of the exponent n value. When calculating the passing rate, the part below 0.075 mm is removed, and the remaining part is redistributed according to the proportion. Then, calculate the percentage content of each size fraction of the aggregate. Multiply the total weight by the content percentage to obtain the weight of each size fraction of the aggregate.

[0079] In this example, the gradation composed when n is 1.2 is adopted, the maximum nominal size is 9.5 mm, the passing rates of each size fraction of the aggregate are shown in Table 2, and the contents are shown in Table 3. The aggregate is diabase, with a particle size range of 0.075 mm to 13.2 mm; the asphalt used is ultra-high viscosity modified asphalt; the weight of each specimen is set to 1100 g; a Marshall compactor is selected for compaction during the compaction process, and the number of compaction times is 75 times.

[0080] The method for measuring the skeleton void ratio is the same as that in Example 1. The test results are shown in Table 4.

[0081] Example 3:

[0082] In this test, the gradation is determined through the Talbol formula To determine the gradation, the pass rate of each grade of aggregate will change with the change of the index n value. When calculating the pass rate, the part below 0.075mm is removed, and the remaining part is redistributed according to the proportion. Then the content percentage of each grade of aggregate is calculated, and the weight of each grade of aggregate is obtained by multiplying the total weight by the content percentage.

[0083] This example uses a gradation with an n value of 2.1, a maximum nominal particle size of 9.5 mm, and aggregate pass rates for each grade are shown in Table 2, with the content shown in Table 3. The aggregate is diabase with a particle size range of 0.075 mm to 13.2 mm. The asphalt used is ultra-high-viscosity modified asphalt. Each specimen weighs 1100 g. A Marshall compactor was used for compaction, with 75 cycles.

[0084] The method for measuring the skeleton porosity is the same as that in Example 1. The test results are shown in Table 4.

[0085] Example 4:

[0086] This test uses the Talbol formula To determine the gradation, the pass rate of each grade of aggregate will change with the change of the index n value. When calculating the pass rate, the part below 0.075mm is removed, and the remaining part is redistributed according to the proportion. Then the content percentage of each grade of aggregate is calculated, and the weight of each grade of aggregate is obtained by multiplying the total weight by the content percentage.

[0087] This example uses a gradation with an n value of 0.6, a maximum nominal particle size of 9.5 mm, and aggregate pass rates for each grade are shown in Table 2, and content is shown in Table 3. The aggregate is diabase with a particle size range of 0.075 mm to 13.2 mm. The asphalt used is ultra-high-viscosity modified asphalt. Each specimen weighs 1600 g. A gyratory compactor was used for compaction, with 200 passes.

[0088] The method for measuring the skeleton porosity is as follows:

[0089] (1) According to the asphalt viscosity-temperature curve obtained from the asphalt rotation viscosity test, the temperature of 200°C when the asphalt viscosity is 0.28 Pa·s is determined as the test mixing temperature;

[0090] Place the asphalt, aggregate, mold and other test tools in an oven and heat them for 3 to 4 hours. The heating temperature is 180℃ for the first period of time and 200℃ for the last hour to prevent the asphalt from aging due to long-term high temperature.

[0091] (2) Pour the heated aggregate into the mixer and mix for 90 s to make the aggregate evenly mixed; pause the mixing, add 2% asphalt, and continue mixing for 90 s until evenly mixed; use a shovel to appropriately stir the mixed mixture to prevent the mixture at the bottom of the mixing pot from not being fully and evenly mixed; the mixing temperature needs to be maintained at 210 °C to prevent excessive temperature loss during the opening and closing of the mixing pot, resulting in poor adhesion of the asphalt to the aggregate.

[0092] (3) Place the mold on the scale, tare it, then scoop out half of the weight of a specimen of aggregate into the mold with a small cup, remove the mold and place it steadily on the ground, insert and tamp it 15 times along the perimeter of the mold with a thin iron rod and 10 times in the middle, then put the mold back on the scale, and finally add the remaining weight of aggregate so that the total weight reaches the preset value of 1600 g, with an upper and lower limit of no more than 5 g, and then insert and tamp it 15 times along the perimeter of the mold with a thin iron rod and 10 times in the middle;

[0093] (4) Level the surface of the aggregate after tamping, place a round kraft paper on it to prevent the aggregate from being carried out during compaction;

[0094] (5) Place the processed mold in the rotary compactor and compact it according to the set number of times, 200 times; take out the compacted aggregate, place it in a cool place and let it cool naturally for 20 min before demolding;

[0095] (6) Export the height of the formed specimen from the rotary compactor;

[0096] (7) According to the height exported by the instrument, calculate the volume of the specimen through the cylindrical volume formula, and then obtain the compacted density of the specimen by dividing the weight of the specimen by the volume; finally, the skeleton void ratio V of the specimen can be calculated through formula (1) ag 。

[0097]

[0098] In the formula:

[0099] V ag —— represents the skeleton void ratio of the aggregate (%);

[0100] ρ1 —— represents the compacted density of the aggregate (g / cm 3 );

[0101] ρ2 —— represents the synthetic bulk specific gravity of the aggregate (g / cm 3 );

[0102] The test results are shown in Table 4.

[0103] Example 5:

[0104] This test is based on the Talbol formula Determine the gradation. The passing rate of each size fraction of aggregates will vary with the change of the exponent n value. When calculating the passing rate, the part below 0.075mm is removed, and the remaining part is redistributed according to the proportion it occupies. Then, calculate the percentage content of each size fraction of aggregates. Multiply the total weight by the percentage content to obtain the weight of each size fraction of aggregates.

[0105] In this example, the gradation composed when the n value is 1.2 is adopted, the maximum nominal size is 9.5mm, the passing rates of each size fraction of aggregates are shown in Table 2, and the contents are shown in Table 3. The aggregates are diabase, with a particle size range of 0.075mm to 13.2mm; the asphalt used is ultra-high viscosity modified asphalt; the weight of each specimen is set to 1600g; a rotary compactor is selected for the compaction process, and the number of compaction times is 200 times.

[0106] The method for measuring the skeleton void ratio is the same as that in Example 4. The test results are shown in Table 4.

[0107] Example 6:

[0108] This test uses the Talbol formula Determine the gradation. The passing rate of each size fraction of aggregates will vary with the change of the exponent n value. When calculating the passing rate, the part below 0.075mm is removed, and the remaining part is redistributed according to the proportion it occupies. Then, calculate the percentage content of each size fraction of aggregates. Multiply the total weight by the percentage content to obtain the weight of each size fraction of aggregates.

[0109] In this example, the gradation composed when the n value is 2.1 is adopted, the maximum nominal size is 9.5mm, the passing rates of each size fraction of aggregates are shown in Table 2, and the contents are shown in Table 3. The aggregates are diabase, with a particle size range of 0.075mm to 13.2mm; the asphalt used is ultra-high viscosity modified asphalt; the weight of each specimen is set to 1600g; a rotary compactor is selected for the compaction process, and the number of compaction times is 200 times.

[0110] The method for measuring the skeleton void ratio is the same as that in Example 4. The test results are shown in Table 4.

[0111] Table 2 Passing rates of each size fraction of aggregates (%) under different n values of the Talbol formula

[0112]

[0113] Table 3 Contents of each size fraction of aggregates (%) under different n values of the Talbol formula

[0114]

[0115]

[0116] Table 4 Skeleton void ratio V of the gradation under different n values ag (%)

[0117]

[0118] Experimental results analysis

[0119] (1) Determination of the reduction coefficient α described in the present invention

[0120] Taking into account the boundary effect caused by the small volume of the test specimen, and the fact that the aggregate will be more evenly distributed and dense when the complete flowable mortar asphalt mixture is formed, the calculated V ag It must be multiplied by the reduction coefficient α before it can be used as V in mixture design. ag .

[0121] The flowable mortar asphalt mixture with a powder-to-binder ratio of 1 is formed by the single-sided Marshall compaction method. If the asphalt mortar just fills the entire specimen, it means that the V calculated by the method of the present invention is ag Based on our experience in the molding process, we first determined three reduction coefficients, 0.80, 0.84, and 0.88, and then verified them through the following experiments:

[0122] According to the principle of flowing mortar to fill the voids in the framework in the mortar flow filling design method (MaFF method), the relationship between parameters such as mortar dosage, aggregate dosage and framework void ratio is shown in formulas (2) and (3):

[0123] P ag +P ma =100 (2)

[0124] Where:

[0125] P ag is the amount of aggregate in the FMA mixture (percentage by weight);

[0126] P ma is the amount of mortar used in the FMA mixture (weight percentage).

[0127]

[0128] Where:

[0129] V ag is the skeleton void ratio of FMA mixture;

[0130] VV is the designed internal void ratio, and the measured internal void ratio of FMA is usually less than 1%;

[0131] F d The filling degree indicates the degree to which the glue fills the voids in the skeleton, and the value range is 0 to 1.0;

[0132] γ cThe bulk density (measured) in the compacted or densified state of the aggregate;

[0133] P ma0 P is the dosage of the adhesive mortar (weight percentage), which can be measured through the mixing test;

[0134] γ ma is the synthetic relative density of the mortar;

[0135] Multiply the V calculated by the Marshall compaction method (i.e., Examples 1, 2, and 3 of densification using a Marshall compactor) ag by the corresponding reduction coefficients 0.80, 0.84, and 0.88 respectively, and then substitute it together with other parameters into Formulas (2) and (3). Other required parameters are shown in Table 5 to obtain the aggregate dosage P ag and the mortar dosage P ma , and then fabricate Marshall specimens according to T0702 - 2011 in the "Test Procedures for Bitumen and Bituminous Mixtures for Highway Engineering" (JTG E20—2011). Observe whether there is bleeding during the process of fabricating Marshall specimens. If there is bleeding, it indicates that the V calculated by the method described in the present invention ag is greater than the true value. If there is no bleeding phenomenon, it indicates that the V calculated by the method described in the present invention ag is less than or equal to the true value; in the case of no bleeding, cut the fabricated specimen vertically and observe the filling degree of the asphalt mortar in the mixture. If the entire specimen is not filled, it indicates that the V calculated by the method described in the present invention ag is less than the true value. If the entire specimen is just filled, it indicates that the V calculated by the method described in the present invention ag is basically consistent with the true value.

[0136] Table 5 Parameters required for MaFF method calculation

[0137]

[0138] Analysis of the results of the flowable mortar asphalt mixture fabricated after multiplying by the three coefficients respectively:

[0139] When the reduction coefficient is selected as 0.80, there is no bleeding phenomenon during the forming process. However, according to the observation of the cross-section of the fabricated Marshall specimen, the upper part of the specimen is not completely filled with the mortar and there are still some voids, indicating that the V measured by the Marshall method (the test method of densification using a Marshall compactor) ag is smaller than the actual result after multiplying by 0.80;

[0140] When the reduction coefficient is selected asag The result is larger than the actual result after multiplying the value by 0.88;

[0141] When the reduction coefficient is selected as 0.84, there is no bleeding phenomenon during the forming process. After forming, the cut surface of the specimen is as Figures 1 to 3 shown. After cutting, it can be seen that the degree of mortar filling in the asphalt mixture formed by the corresponding gradation in the case is basically just filled, and there are basically no voids visible on the cut surface, indicating that the V ag value obtained by the Marshall method (a test method using a Marshall compactor for compaction) is basically consistent with the actual result after multiplying by 0.84.

[0142] However, in actual pavement construction, due to differences in the construction site, construction methods, compaction work, and aggregate shape, etc., there may be differences in various aspects, resulting in some differences between the V ag used in the indoor test FMA design and the site. Therefore, during actual pavement construction, the final V ag value should be adjusted based on the V ag after actual construction compaction as the standard to ensure the consistency of the design results of the flowing mortar mixture. According to the test results, the reduction coefficient should be a range value, and the recommended reduction coefficient range is more appropriate between 0.70 and 0.90.

[0143] (2) Conversion coefficient β

[0144] Due to the different simulation degrees and compaction work of the Marshall compactor and the gyratory compactor for actual construction compaction, there will be some differences in the numerical value of the V ag calculated according to the method described in the present invention, which may lead to inconsistent mortar dosages during the design process of the flowing mortar mixture. Therefore, the V ag calculated by the two forming methods should be converted through a coefficient.

[0145] Combining the Marshall method (a test method using a Marshall compactor for compaction) and the gyratory compaction method

[0146] (a test method using a gyratory compactor for compaction), the V ag calculated is fitted using the Logistic function model. By observing the positional relationship of the two function curves, it is found that after multiplying the V ag measured by the gyratory compaction method by the coefficient 1.06, the position of its fitted function curve is basically coincident with the position of the fitted function curve of the V ag measured by the Marshall method. Therefore, finally, based on the V ag calculated by the Marshall method as the standard, it is used as the V ag used in the indoor test FMA design. And when the gyratory compaction method is used, the calculated V agIt should be multiplied by the conversion coefficient β = 1.06 as the finally tested value, and then multiplied by the reduction coefficient α before it can be used as V in the mixture design. ag .

[0147] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A wet mixing test method for measuring the voids in the mineral aggregate of flowing mastic asphalt mixture, characterized in that, It includes the following steps: (1) Select the gradation and weigh each size of aggregate, and weigh the asphalt accounting for 2% of the weight of the aggregate; according to the asphalt viscosity-temperature curve obtained from the asphalt rotational viscosity test, determine the temperature T0 °C when the asphalt viscosity is 0.28 Pa·s; Heat the asphalt, aggregate, and tools required for the test in sections. The heating temperature in the previous period is T0 - 20 °C, and the heating temperature in the last hour is T0 °C; (2) Pour the heated aggregate into a mixer for mixing. After the aggregate is mixed evenly, add the asphalt and continue to mix thoroughly; the mixing temperature is T0 + 10 °C; (3) According to the weight of one specimen, add the aggregate mixed with the asphalt into the mold and tamp it; (4) After tamping, place the mold in a Marshall compactor or a gyratory compactor and compact it according to the set number of compaction times; after compaction is completed, take out the aggregate, and demold it after natural cooling to obtain the specimen; (5) Measure the height of the specimen; (6) Calculate the volume of the test piece by the cylinder volume formula according to the measured height of the test piece, and then obtain the compacted density of the test piece by dividing the weight of the test piece by the volume; finally, the skeleton void ratio V of the test piece can be calculated through Equation (1). ag ; Where: V ag —— indicates the void ratio of the aggregate skeleton, %; ρ1——Indicates the compacted density of the aggregate, g / cm 3 ; ρ2—— represents the synthetic bulk specific gravity of the aggregate, g / cm 3 .

2. The method according to claim 1, wherein T0 described in step (1) is 200 °C; the asphalt is ultra-high viscosity modified asphalt or SBS modified asphalt.

3. The method according to claim 1, characterized in that, In step (2), the mixing time of the aggregate poured into the mixer is 90 s, and continue to mix for 90 s after adding the asphalt.

4. The method according to claim 1, wherein The specific steps of step (3) are: weigh the aggregate mixed with the asphalt according to half of the weight of one specimen and add it to the mold. After placing it stably, use a thin iron rod to tamp 15 times along the periphery of the mold and 10 times in the middle. Then add the remaining weight of the aggregate to make the total weight reach the preset value, with an upper and lower limit of no more than 5 g. Then use the thin iron rod to tamp 15 times along the periphery of the mold and 10 times in the middle; the weight of one specimen is set to 1100 - 1600 g.

5. The method according to claim 1, characterized in that, Before compaction in step (4), level the surface of the aggregate after tamping and place a round kraft paper to prevent the aggregate from being carried out during the compaction process; In step (4), the number of compaction times is 75 - 200 times, and the aggregate is placed in a cool place and naturally cooled for 24 h before demolding.

6. The method according to claim 1, wherein Measuring the height of the specimen in step (5): When a Marshall compactor is used in step (4), use a vernier caliper to measure the height of the demolded specimen from four directions of front, back, left, and right, and finally take the average value as the height of the specimen. If the difference between the maximum and minimum measured heights is greater than 1 mm, the specimen needs to be remolded; when a gyratory compactor is used in step (4), directly export the height of the formed specimen from the gyratory compactor.

7. The method according to claim 1, wherein The calculation steps for the bulk specific gravity of the aggregate in step (6): First, measure the bulk specific gravity of each size of aggregate according to method T0304 in "Test Regulations for Aggregates of Highway Engineering" JTG 3432—2024, then calculate the content of each size of aggregate, and finally calculate the bulk specific gravity of the aggregate according to formula T0304-9 in the specification.

8. The method according to claim 1, characterized in that, The V calculated in step (6) ag is multiplied by the reduction coefficient α and used as the V in the mixture design ag , where α = 0.70 - 0.

90.

9. The method according to claim 8, wherein When the Marshall compactor is used in step (4), the V calculated in step (6) ag is directly multiplied by the reduction coefficient α and used as the V in the mixture design ag ; when the gyratory compactor is used in step (4), the V calculated in step (6) ag is first multiplied by the conversion coefficient β = 1.06 and then by the reduction coefficient α before it can be used as the V in the mixture design ag .

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