Preparation method, device and detection method of emulsified asphalt cold recycled mixture specimen

Abstract

The present invention discloses a method, device and detection method for preparing an emulsified asphalt cold recycled mixture specimen, comprising: loading the emulsified asphalt cold recycled mixture into a lower test mold, and performing an initial compaction to form a lower sample; placing the lower test mold and the lower sample in an oven for primary curing; taking out the lower test mold and the lower sample for secondary curing; laying an isolation layer on the upper side of the lower sample; placing the upper test mold on the isolation layer; loading the hot mix asphalt mixture into the upper test mold and performing a secondary compaction to form an upper sample; placing at room temperature for a third curing; taking out the lower sample; the present invention simulates the primary compaction process and the secondary compaction process in an actual construction process, so as to prepare an emulsified asphalt cold recycled mixture specimen that is more in line with the use environment, and perform subsequent testing work based on the specimen.

Description

Technical Field

[0001] The present invention relates to the technical field of road engineering materials, and in particular to a method, a device and a detection method for preparing an emulsified asphalt cold recycled mixture specimen. Background Art

[0002] After years of operation, asphalt pavements inevitably experience cracking, deformation, and loosening. Coupled with a significant increase in traffic volume, asphalt pavement repairs, renovations, and expansions are in rapid succession, gradually shifting from a construction phase to a period focused on both construction and maintenance. Traditional milling restoration methods (milling out the old asphalt layer and then patching it with new asphalt mixture) generate a large amount of recycled asphalt (RAP).

[0003] Emulsified asphalt cold recycling technology helps conserve resources and protect the environment. The utilization rate of old asphalt mixtures can reach over 80%. Compared to hot recycling technology, it avoids secondary heating of RAP materials, saves energy consumption, and reduces asphalt fume emissions, offering significant environmental advantages. Emulsified asphalt cold recycling technology involves crushing and screening recycled asphalt mixtures, then mixing them with new mineral aggregate, emulsified asphalt, and water in a specific proportion at room temperature in a specialized mixing plant to form an emulsified asphalt cold recycled mixture. This mixture is then laid to form an asphalt pavement. The recycled layer can generally be used as the sub-layer and base layer.

[0004] During the construction, there is a secondary compaction process in the construction process of the on-site emulsified asphalt cold recycled mixture. In the early design process of the cold recycled mixture, the secondary compaction effect was not considered, resulting in severe compaction rutting in the cold recycled layer during the actual construction process.

[0005] The test specimen preparation method for the mix design process of emulsified asphalt cold recycled mixtures is primarily based on the Marshall method described in the "Technical Specification for Highway Asphalt Pavement Regeneration" (JTG T 5521-2019). However, the indoor Marshall molding method described in this specification poorly simulates the secondary compaction mechanism in the field, resulting in the designed porosity of the emulsified asphalt cold recycled mixture being larger than the actual porosity. The Marshall method is unable to effectively simulate the secondary compaction process of the emulsified asphalt cold recycled mixture layer. Summary of the Invention

[0006] The technical problem to be solved by the present invention is that at the current stage, it is difficult to effectively simulate the secondary compaction process of the emulsified asphalt recycled mixture layer in actual use in the preparation of emulsified asphalt cold recycled mixture specimens indoors. The purpose is to provide a method, device and detection method for preparing emulsified asphalt cold recycled mixture specimens, which solves the problems of preparing emulsified asphalt cold recycled mixture specimens and detecting performance based on the specimens.

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

[0008] A method for preparing a specimen of an emulsified asphalt cold recycled mixture comprises:

[0009] Mixing emulsified asphalt cold recycled mixture;

[0010] The emulsified asphalt cold recycled mixture is loaded into the lower test mold, and the emulsified asphalt cold recycled mixture in the lower test mold is initially compacted to form a lower test sample;

[0011] Put the lower test mold and the lower sample into the oven for curing, and set the first temperature and the first time;

[0012] After the first curing is completed, the lower test mold and the lower sample are taken out and placed at room temperature for a second curing, and a second time is set;

[0013] Lay an isolation layer on the side of the lower specimen;

[0014] Place the upper test mold on the isolation layer;

[0015] Mixing hot mix asphalt;

[0016] The hot mix asphalt mixture is loaded into the upper test mold, and the hot mix asphalt mixture in the upper test mold is compacted twice to form an upper test sample;

[0017] Place the upper test mold, upper sample, lower test mold, and lower sample at room temperature for three curing cycles, and set the third time;

[0018] The lower layer sample was taken out to obtain the emulsified asphalt cold recycled mixture specimen.

[0019] Specifically, the first temperature is 40° C. to 80° C., the first time is 36 hours to 60 hours, the second time is 8 hours to 16 hours, and the third time is 12 hours to 36 hours.

[0020] Preferably, the first temperature is 60° C., the first time is 48 hours, the second time is 12 hours, and the third time is 24 hours.

[0021] Specifically, the mixing method of emulsified asphalt cold recycled mixture is:

[0022] Obtain the formula quantity of each raw material in the emulsified asphalt cold recycled mixture;

[0023] Add RAP, new aggregate and cement into the mixer according to the formula amount and mix them evenly;

[0024] Add water to the mixer according to the formula and stir for 90 seconds;

[0025] Add emulsified asphalt into the mixer according to the formula and stir for 90 seconds;

[0026] Add the mineral powder into the mixer according to the formula and stir for 90 seconds.

[0027] Preferably, the gradation of the emulsified asphalt cold recycled mixture is:

[0028] RAP1:RAP2:RAP3:new aggregate:mineral powder=36:11:41:10:2;

[0029] The optimal moisture content is 4.5%, the optimal emulsified asphalt dosage is 3.5%, and the optimal cement content is 1.5%;

[0030] RAP1 is RAP of 10~30mm, RAP2 is RAP of 5~10mm, RAP3 is RAP of 0~5mm, and the new aggregate is limestone crushed stone of 10~20mm.

[0031] Specifically, the isolation layer is made of glossy paper.

[0032] An emulsified asphalt cold recycled mixture specimen preparation device, used to implement the above-mentioned emulsified asphalt cold recycled mixture specimen preparation method, the device comprising:

[0033] The lower trial mold is a rectangular box with the upper side removed;

[0034] The upper test mold is a rectangular box with the upper side removed;

[0035] A fixing pin, wherein the lower portion of the upper trial mold is detachably connected to the upper portion of the upper trial mold via the pin;

[0036] A wheel rolling forming machine, which is used to provide rolling pressure to the lower sample located in the lower test mold, and is also used to provide rolling pressure to the upper sample located in the upper test mold;

[0037] Wherein, the upper side surface of the lower layer sample is in contact with the lower side surface of the upper layer test mold.

[0038] Specifically, the size of the lower trial mold is 400mm×300mm×40~100mm, and the size of the upper trial mold is 400mm×300mm×40~100mm.

[0039] Specifically, the first compaction is performed by rolling the lower layer sample back and forth 12 to 18 times through the wheel rolling forming machine, and the second compaction is performed by rolling the upper layer sample back and forth 10 to 14 times through the wheel rolling forming machine.

[0040] A method for testing an emulsified asphalt cold recycled mixture specimen, based on an emulsified asphalt cold recycled mixture specimen prepared by the above-mentioned method for preparing an emulsified asphalt cold recycled mixture specimen, the method comprising:

[0041] A rutting test was conducted on emulsified asphalt cold recycled mixture specimens to evaluate the high temperature stability of the emulsified asphalt cold recycled mixture;

[0042] Cylindrical specimens were obtained by core sampling on emulsified asphalt cold recycled mixture specimens, and the void ratio, Marshall stability and splitting strength were tested using the cylindrical specimens.

[0043] The remaining emulsified asphalt cold recycled mixture specimens were cut into strip specimens, and the strip specimens were used to carry out low-temperature bending test and fatigue test to evaluate the low-temperature crack resistance and fatigue resistance of the emulsified asphalt cold recycled mixture.

[0044] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0045] The present invention performs a primary compaction on the emulsified asphalt cold recycled mixture layer to simulate the primary compaction formed by the rolling action of a road roller during the construction process; a hot mix asphalt mixture is formed on the lower test piece, and the load and heat of the upper test piece are transferred to the lower test piece to achieve secondary compaction of the emulsified asphalt cold recycled mixture layer. This process is consistent with the secondary compaction process during the on-site paving and rolling process of the upper hot mix asphalt mixture, in which the heat and roller load are transferred to the lower emulsified asphalt cold recycled mixture layer, resulting in a further reduction in its void ratio.

[0046] By simulating the primary compaction process and the secondary compaction process in the actual construction process, the present invention can prepare an emulsified asphalt cold recycled mixture specimen that is more suitable for the use environment, and carry out subsequent testing work based on the specimen. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The accompanying drawings illustrate exemplary embodiments of the present invention and, together with the description thereof, are used to explain the principles of the present invention. These drawings are included to provide a further understanding of the present invention, and the accompanying drawings are included in and constitute a part of this specification and do not constitute a limitation of the embodiments of the present invention.

[0048] Figure 1 It is a structural schematic diagram of an emulsified asphalt cold recycled mixture specimen preparation device according to the present invention.

[0049] Figure 2 The present invention is a flowchart of a method for preparing an emulsified asphalt cold recycled mixture specimen.

[0050] Figure 3 It is a temperature diagram according to the fifth embodiment of the present invention.

[0051] Figure numerals: 1-lower test mold, 2-upper test mold, 3-wheel rolling machine. DETAILED DESCRIPTION

[0052] To make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the relevant content and are not intended to limit the present invention.

[0053] It should also be noted that, for the convenience of description, only the parts related to the present invention are shown in the drawings.

[0054] In the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0055] During conventional construction, after the emulsified cold recycled asphalt mixture is spread and rolled into shape, it takes a long time for its strength to develop and its moisture to evaporate. Therefore, the cold recycled mixture must generally be cured for at least two days (preferably no less than seven days) after rolling and forming before the upper structural layer can be paved. Curing can be terminated early when a complete core sample can be retrieved or the mixture's moisture content is below 2%. On the other hand, during the paving of the hot-mix asphalt mixture, the mixture temperature often reaches 150-170°C. This heat will inevitably transfer to the cold recycled layer, thereby increasing its temperature, which can reach a maximum temperature of over 60°C. This will inevitably accelerate the evaporation of moisture and the development of strength in the cold recycled layer. Simultaneously, the vibratory rolling action of the roller during paving will inevitably transfer to the recycled layer. This, coupled with the temperature rise, will cause secondary compaction of the cold recycled mixture.

[0056] In general, there is a secondary compaction process in the construction process of on-site emulsified asphalt cold recycled mixture, which mainly includes: 1) the primary compaction process formed by the rolling action of the roller during the construction of the emulsified asphalt cold recycled mixture layer; 2) the secondary compaction process in which the heat and roller load of the upper hot mix asphalt mixture are transferred to the lower emulsified asphalt cold recycled mixture layer during the paving and rolling process, resulting in a further reduction in its porosity, which further increases the strength of the emulsified asphalt cold recycled mixture and improves its various road performance properties.

[0057] In the early design process of cold recycled mixture, the secondary compaction effect was not taken into consideration, resulting in severe compaction rutting in the cold recycled layer during the actual construction process.

[0058] Currently, the preparation of cold-recycled emulsified asphalt mixture specimens indoors is primarily based on the "Technical Specification for Highway Asphalt Pavement Regeneration" (JTG T 5521-2019) and the "Test Procedure for Asphalt and Asphalt Mixtures for Highway Engineering" (JTG E20-2011). This involves forming 80 mm (coarse-grained) or 50 mm (medium-grained and fine-grained) thick cold-recycled mixture rutting slabs according to the T0703 wheel rolling method. These slabs are then rolled to a Marshall density of 100 ± 1%. Following rolling, the specimens are quickly dried in a 60°C forced air oven to constant weight (typically for approximately 48 hours). Dynamic stability testing is then performed according to T0719, with the specimens held at this temperature for 8 to 10 hours before testing. This standard does not consider the secondary compaction process for preparing cold-recycled emulsified asphalt mixture specimens using the wheel rolling method.

[0059] The preparation method of the test specimens in the mix ratio design process of emulsified asphalt cold recycled mixture is mainly based on the Marshall method introduced in the "Technical Specifications for Highway Asphalt Pavement Regeneration" (JTG T 5521-2019). In this test, the emulsified asphalt cold recycled mixture is compacted 50 times on both sides using a Marshall compactor (standard compaction specimen). The specimen is then placed on its side in a 60°C forced air oven together with the test mold to cure to constant weight. The specimen is then taken out and compacted 25 times on both sides using a Marshall compactor (standard compaction specimen). The specimen is then placed on its side on the ground at room temperature to cool for at least 12 hours before demolding.

[0060] The emulsified asphalt cold recycled mixture specimens were formed by the top-down hammering action of a Marshall hammer. However, the on-site compaction process and the wheel rolling method are based on the kneading action of the rolling wheel, and their forming mechanisms are quite different. In addition, the cylindrical Marshall specimens are too small and less representative. The parameters such as the void ratio of the Marshall indoor formed specimens are poorly matched with the on-site rolling formed structural layers. Therefore, the Marshall forming method is difficult to effectively simulate the forming of on-site emulsified asphalt cold recycled mixture specimens.

[0061] At the same time, during the side-curing process of Marshall-compacted cold-recycled asphalt emulsion specimens, as the internal moisture evaporates, the upper and lower surfaces of the specimens will expand slightly. A secondary Marshall compaction is then used to eliminate this expansion and simulate the secondary compaction mechanism in the field. This process may cause microcracks to form within the already solidified cold-recycled asphalt emulsion, affecting its subsequent strength growth. Clearly, the standardized indoor Marshall forming method has poor compliance with the simulated secondary compaction mechanism in the field, resulting in the designed porosity of the cold-recycled asphalt emulsion being larger than the actual porosity. In short, the Marshall method is difficult to effectively simulate the secondary compaction process of the cold-recycled asphalt emulsion layer.

[0062] Example 1

[0063] This embodiment provides an emulsified asphalt cold recycled mixture specimen preparation device, including a lower test mold 1, an upper test mold 2, fixed pins and a wheel rolling forming machine 3.

[0064] The lower test mold 1 is a rectangular box with the upper side removed, and the lower test piece can be cast in the lower test mold 1. The upper test mold 2 is a rectangular box with the upper side removed, and the upper test piece can be cast in the upper test mold 2. The upper test mold 2 can be stacked on the lower test mold 1, and the upper side of the lower test piece fits with the lower side of the upper test mold 2, so that the pressure of the upper test mold 2 can be transferred to the lower test piece.

[0065] The lower part of the upper test mold 2 is detachably connected to the upper part of the lower test mold 1 through pins, which facilitates the disassembly and connection of the upper test mold 2 and the lower test mold 1.

[0066] The wheel rolling forming machine 3 is used to provide rolling pressure to the lower sample located in the lower test mold 1, and is also used to provide rolling pressure to the upper sample located in the upper test mold 2. Compared with the Marshall method, the use of the wheel rolling forming machine 3 can more effectively simulate the rolling principle of the mixture by the roller during the construction process.

[0067] The size of the lower test mold 1 is 400mm×300mm×40~100mm, and the size of the upper test mold 2 is 400mm×300mm×40~100mm.

[0068] Example 2

[0069] Based on the above ideas and in response to existing shortcomings, this embodiment proposes a method for preparing emulsified asphalt cold recycled mixture specimens. It is based on the wheel rolling molding method of indoor plate specimens, effectively simulates the secondary rolling molding mechanism of on-site emulsified asphalt cold recycled mixtures, and is prepared based on the device of embodiment 1.

[0070] The method includes:

[0071] The first step is to mix the emulsified asphalt cold recycled mixture.

[0072] In the second step, the lower test mold 1 is placed horizontally, and the emulsified asphalt cold recycled mixture is loaded into the lower test mold 1. The emulsified asphalt cold recycled mixture in the lower test mold 1 is initially compacted by the wheel rolling forming machine 3 to form a lower test sample.

[0073] The third step is to place the lower test mold 1 and the lower sample into an oven for curing, and set the first temperature and the first time;

[0074] The fourth step is to take out the lower test mold 1 and the lower sample after completing the first curing, place them at room temperature for a second curing, and set a second time to simulate the actual curing process of the emulsified asphalt cold recycled mixture on site.

[0075] The fifth step is to lay an isolation layer on the upper side of the lower specimen to avoid close adhesion between the upper and lower specimens;

[0076] The sixth step is to place the upper test mold 2 on the isolation layer. In order to enable the upper test mold 2 to transfer pressure to the lower test piece, in practice, the upper side of the lower test piece is set to be slightly higher than the upper side of the lower test mold 1.

[0077] The seventh step is to mix the hot mix asphalt mixture and shape it according to the current "Test Procedure for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011). This step can be carried out at any appropriate time.

[0078] In the eighth step, the hot-mix asphalt mixture is loaded into the upper test mold 2 and the hot-mix asphalt mixture in the upper test mold 2 is compacted for a second time to form an upper test specimen. When the roller forming machine 3 compacts the upper test specimen, the load and heat of the upper test specimen are transferred to the lower emulsified asphalt cold recycled mixture layer to achieve secondary compaction of the lower test specimen.

[0079] Step 9: Place the upper test mold 2, the upper sample, the lower test mold 1, and the lower sample at room temperature for three curing cycles, and set a third time.

[0080] In the tenth step, the upper test mold 2 and the lower test mold 1 are separated, and the lower layer sample is taken out to obtain the emulsified asphalt cold recycled mixture specimen.

[0081] Example 3

[0082] This embodiment specifically sets some of the time and temperature in the first embodiment.

[0083] The first temperature is 40° C. to 80° C., the first time is 36 h to 60 h, the second time is 8 h to 16 h, and the third time is 12 h to 36 h.

[0084] As a further preference, the first temperature is 60° C., the first time is 48 hours, the second time is 12 hours, and the third time is 24 hours.

[0085] The preferred rolling frequency is 12-18 reciprocating passes of the three rollers on the lower layer of the sample for primary compaction, and 10-14 reciprocating passes of the three rollers on the upper layer for secondary compaction. The specific number of passes is determined based on the void ratio requirements to simulate the actual compaction of the emulsified asphalt cold recycled mixture at the construction site.

[0086] Compared with the prior art, this embodiment has the following beneficial effects:

[0087] (1) At present, the preparation of indoor emulsified asphalt cold recycled mixture plate specimens is carried out according to the T0703 wheel rolling method. The cold recycled mixture rutting plate specimens are 80mm (coarse-grained type) or 50mm thick (medium-grained type and fine-grained type). The specimens are rolled to a Marshall standard density of 100±1%. After rolling, the specimens are quickly placed in a 60℃ forced air oven to dry to constant weight (usually about 48 hours). The standard process of preparing emulsified asphalt cold recycled mixture plate specimens by wheel rolling does not take into account its secondary compaction process.

[0088] In addition, the purpose of Marshall secondary compaction in the existing specifications is mainly to avoid the volume expansion that is prone to occur in the emulsified asphalt cold recycled mixture sample during the oven heating process, and to slightly reduce the voids after some water evaporation. It cannot characterize the on-site secondary compaction process of the emulsified asphalt cold recycled mixture, resulting in the designed porosity of the emulsified asphalt cold recycled mixture being larger than the actual porosity. This deviation in the designed asphalt mixture mix ratio may cause very serious early damage to the pavement.

[0089] The preparation process of emulsified asphalt cold recycled mixture plate specimens considering secondary compaction provided by the present invention has a high degree of compliance with its secondary compaction process on site, specifically: ① The kneading action of the wheel roller forming machine 3 on the top surface of the emulsified asphalt cold recycled mixture layer back and forth is consistent with the initial compaction process formed by the rolling action of the roller during the construction process; ② The upper hot mix asphalt mixture is formed on the emulsified asphalt cold recycled mixture layer, and the load and heat of the upper specimen are transferred to the lower specimen to achieve secondary compaction. This process is consistent with the secondary compaction process in which the heat and roller load of the upper hot mix asphalt mixture paving and rolling process on site are transferred to the lower emulsified asphalt cold recycled mixture layer, resulting in a further reduction in its porosity.

[0090] (2) The current specification uses a Marshall hammer to form emulsified asphalt cold recycled mixture specimens. The forming mechanism is significantly different from the on-site roller compaction. This process may cause microcracks to form inside the already solidified emulsified asphalt cold recycled mixture, affecting its later strength growth. In addition, the cylindrical Marshall specimens are too small and poorly representative. The parameters such as the void ratio of the Marshall indoor specimens do not match the on-site rolling forming structure. Therefore, the Marshall forming method cannot effectively simulate the forming of on-site emulsified asphalt cold recycled mixture specimens.

[0091] However, the present invention uses a wheel rolling test machine to compact the emulsified asphalt cold recycled mixture through the rubbing action of a reciprocating load, without damaging the internal structure of the emulsified asphalt cold recycled mixture that has initially solidified and hardened. This is closer to the Marshall forming method compared to the compressive action of an on-site roller, and the test mold length and width are 400 mm and 300 mm respectively, which is more representative. The formed plate specimen can be regarded as a scaled model of on-site construction, which can effectively simulate the forming of on-site emulsified asphalt cold recycled mixture specimens and is simple to operate.

[0092] (3) The method for preparing emulsified asphalt cold recycled mixture specimens that can be compacted twice provides a plate specimen, which is different from the cylindrical specimen formed by Marshall. It can be used to test the road performance of emulsified asphalt cold recycled mixtures, such as dynamic stability, low-temperature bending performance, and fatigue resistance. The common feature is that the tests all use plate or strip specimens. However, the existing specifications for testing the above properties do not consider the secondary compaction process of emulsified asphalt cold recycled mixtures, and inevitably there are differences from the actual values. The secondary compaction process of emulsified asphalt cold recycled mixtures can further compress the voids, which is significantly better than the standard method. The strength of the emulsified asphalt cold recycled mixture is further improved, and its various road performance tends to be better.

[0093] Example 4

[0094] This embodiment specifically illustrates the first step in the second embodiment.

[0095] The RAP used in this example was recovered from actual road milling. The relevant RAP parameters are shown in Tables 1 and 2. The mineral powder had a 0.075 mm pass rate of 99.4%. The emulsified asphalt was an imported slow-cracking cationic asphalt with a solids content of 62.3%. The cement was PO42.5 ordinary Portland cement. The new aggregate was 10-20 mm limestone crushed stone. The relevant technical parameters are shown in Table 3.

[0096] Table 1 Test results of RAP moisture content and asphalt content

[0097]

[0098] Table 2 Recovered asphalt indicators

[0099]

[0100] Table 3 Limestone crushed stone test results

[0101]

[0102] The gradation of emulsified asphalt cold recycled mixture is: RAP1: RAP2: RAP3: new aggregate: mineral powder = 36:11:41:10:2;

[0103] The optimal moisture content is 4.5%, the optimal emulsified asphalt dosage is 3.5%, and the optimal cement content is 1.5%;

[0104] RAP1 is RAP of 10~30mm, RAP2 is RAP of 5~10mm, RAP3 is RAP of 0~5mm, and the new aggregate is limestone crushed stone of 10~20mm.

[0105] The mixing method of emulsified asphalt cold recycled mixture is:

[0106] Obtain the formula quantity of each raw material in the emulsified asphalt cold recycled mixture;

[0107] Add RAP, new aggregate and cement into the mixer according to the formula amount and mix them evenly;

[0108] Add water to the mixer according to the formula and stir for 90 seconds;

[0109] Add emulsified asphalt into the mixer according to the formula and stir for 90 seconds;

[0110] Add the mineral powder into the mixer according to the formula and stir for 90 seconds.

[0111] Example 5

[0112] Based on the emulsified asphalt cold recycled mixture specimen prepared by the above-mentioned method for preparing an emulsified asphalt cold recycled mixture specimen, a detection method for the emulsified asphalt cold recycled mixture specimen is provided, comprising:

[0113] A rutting test was conducted on emulsified asphalt cold recycled mixture specimens to evaluate the high temperature stability of the emulsified asphalt cold recycled mixture;

[0114] Cylindrical specimens were obtained by core sampling on emulsified asphalt cold recycled mixture specimens, and the void ratio, Marshall stability and splitting strength were tested using the cylindrical specimens.

[0115] The emulsified asphalt cold recycled mixture specimens were cut into strip specimens, and the strip specimens were used to carry out low-temperature bending test and fatigue test to evaluate the low-temperature stability and fatigue resistance of the emulsified asphalt cold recycled mixture, which were used to guide the mix proportion design of the emulsified asphalt cold recycled mixture.

[0116] After demoulding, the lower layer specimens were cut into small test blocks with a side length of about 8 to 10 cm. The density of each test block was tested, and the void ratio was calculated to determine the number of round trip rollings of the wheel rolling forming machine 3 under working conditions that were basically consistent with the on-site void ratio.

[0117] Initially compacted specimens of cold-recycled emulsified asphalt mixture were cut into small blocks approximately 8-10 cm in length. The density of each block was measured, and the void ratio was calculated. The void ratios were 11.9%, 10.8%, and 10.2% for 12, 15, and 18 rolling cycles, respectively. In this example, the required void ratio was 11.5%-12.0%, and the number of rolling cycles was determined to be approximately 12.

[0118] To verify the effectiveness of the experimental simulation method, the secondary compaction specimens of the emulsified asphalt cold recycled mixture were cut into small test blocks with a side length of approximately 8 to 10 cm. The density of each test block was tested, and the void ratio was calculated.

[0119] The test results are as follows: the void ratios of the emulsified asphalt cold recycled mixture after primary molding and secondary compaction were 11.9% and 9.6% respectively. After secondary molding of the upper hot mix, the void ratio of the cold recycled mixture decreased by 2.3%, a decrease of 19.3%.

[0120] At the same time, a temperature sensor was placed in the middle of the lower specimen during the preparation process. During the molding process of the upper specimen, the measured temperature peak in the middle of the lower specimen was 66.5°C.

[0121] The actual temperature of the cold recycled layer at a depth of 4cm can reach 56.3℃ after the lower layer specimens are paved and rolled by the upper layer specimens, and the void ratio of the cold recycled layer decreases by about 3.0% on average. Figure 3 shown.

[0122] It shows that there is a secondary compaction mechanism in the molding process of emulsified asphalt cold recycled mixture. The secondary compaction process plate molding method of emulsified asphalt cold recycled mixture provided by the present invention can effectively simulate its on-site secondary compaction mechanism, which helps to better guide the design of the emulsified asphalt cold recycled mixture proportion and on-site construction.

[0123] In the description of this specification, the description with reference to the terms "one embodiment / method", "some embodiments / methods", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment / method or example are included in at least one embodiment / method or example of the present application. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment / method or example. Moreover, the specific features, structures, materials or characteristics described may be combined in an appropriate manner in any one or more embodiments / methods or examples. In addition, those skilled in the art may combine and combine different embodiments / methods or examples described in this specification and the features of different embodiments / methods or examples, unless they are contradictory.

[0124] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of such features. Throughout the description of this application, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0125] It should be understood by those skilled in the art that the above embodiments are merely for the purpose of illustrating the present invention clearly, and are not intended to limit the scope of the present invention. For those skilled in the art, other changes or modifications may be made based on the above invention, and these changes or modifications are still within the scope of the present invention.

Claims

1. A method for preparing emulsified asphalt cold recycled mixture specimens, characterized in that: include: Mixing emulsified asphalt cold recycled mixture; The emulsified asphalt cold recycled mixture is loaded into the lower test mold, and the emulsified asphalt cold recycled mixture in the lower test mold is initially compacted to form a lower test sample; Put the lower test mold and the lower sample into the oven for curing, and set the first temperature and the first time; After the first curing is completed, the lower test mold and the lower sample are taken out and placed at room temperature for a second curing, and a second time is set; An isolation layer is laid on the side of the lower sample, wherein the isolation layer is made of glossy paper; Place the upper test mold on the isolation layer; Mixing hot mix asphalt; The hot mix asphalt mixture is loaded into the upper test mold, and the hot mix asphalt mixture in the upper test mold is compacted twice to form an upper test sample; Place the upper test mold, upper sample, lower test mold, and lower sample at room temperature for three curing cycles, and set the third time. The lower layer sample was taken out to obtain the emulsified asphalt cold recycled mixture specimen.

2. The method for preparing a cold recycled asphalt emulsified mixture specimen according to claim 1, characterized in that: The first temperature is 40° C. to 80° C., the first time is 36 hours to 60 hours, the second time is 8 hours to 16 hours, and the third time is 12 hours to 36 hours.

3. The method for preparing a cold recycled asphalt emulsified mixture specimen according to claim 2, characterized in that: The first temperature is 60° C., the first time is 48 hours, the second time is 12 hours, and the third time is 24 hours.

4. The method for preparing a specimen of emulsified asphalt cold recycled mixture according to claim 1, characterized in that: The mixing method of emulsified asphalt cold recycled mixture is: Obtain the formula quantity of each raw material in the emulsified asphalt cold recycled mixture; Add RAP, new aggregate and cement into the mixer according to the formula amount and mix them evenly; Add water to the mixer according to the formula and stir for 90 seconds; Add emulsified asphalt into the mixer according to the formula and stir for 90 seconds; Add the mineral powder into the mixer according to the formula and stir for 90 seconds.

5. The method for preparing a specimen of emulsified asphalt cold recycled mixture according to claim 4, characterized in that: The gradation of the emulsified asphalt cold recycled mixture is: RAP1:RAP2:RAP3:new aggregate:mineral powder=36:11:41:10:2; The moisture content is 4.5%, the emulsified asphalt dosage is 3.5%, and the cement content is 1.5%; RAP1 is RAP of 10~30mm, RAP2 is RAP of 5~10mm, RAP3 is RAP of 0~5mm, and the new aggregate is limestone crushed stone of 10~20mm.

6. A method for detecting emulsified asphalt cold recycled mixture specimens, characterized in that: The detection method for an emulsified asphalt cold recycled mixture specimen prepared by the method for preparing an emulsified asphalt cold recycled mixture specimen according to any one of claims 1 to 5 comprises: A rutting test was conducted on emulsified asphalt cold recycled mixture specimens to evaluate the high temperature stability of the emulsified asphalt cold recycled mixture; Cylindrical specimens were obtained by core sampling on emulsified asphalt cold recycled mixture specimens, and the void ratio, Marshall stability and splitting strength were tested using the cylindrical specimens. The remaining emulsified asphalt cold recycled mixture specimens were cut into strip specimens, and the strip specimens were used to carry out low-temperature bending test and fatigue test to evaluate the low-temperature crack resistance and fatigue resistance of the emulsified asphalt cold recycled mixture.

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