Heat storage type large-void asphalt mixture, preparation method and low-temperature environment construction method

Abstract

The present application relates to road engineering technology, provide a kind of heat storage type big gap asphalt mixture, including big gap asphalt mixture 100 parts, steel slag powder 3-7 parts and plant-based phase change material 4-6 parts.The present application also provides the preparation method of the above-mentioned heat storage type big gap asphalt mixture, and its construction method in low temperature environment.The heat storage type big gap asphalt mixture, preparation method and low temperature environment construction method of the present application, compared with conventional big gap asphalt mixture, add high specific heat capacity steel slag powder, and automatic heat storage and heat release plant-based phase change material, store a large amount of heat in the mixture preparation process, heat is gradually released in subsequent paving process.Combined with heating machine preheating and tarpaulin covering heat preservation, significantly improve the construction temperature of mixture, guarantee the construction quality.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of road engineering, in particular to a heat storage type large-void asphalt mixture, a preparation method and a low-temperature environment construction method. BACKGROUND

[0002] The construction temperature has a significant impact on the quality of the finished pavement of the asphalt mixture. After the asphalt mixture is transported to the construction site, the temperature of the mixture is generally between 160℃ and 180℃, which is acceptable. However, the mixture needs to go through the links of waiting, paving and rolling, and heat loss occurs in each link, resulting in a decrease in the temperature of the asphalt mixture. In addition to taking good heat preservation measures at each construction link, the temperature of the underlying layer has a significant impact on the heat dissipation efficiency of the mixture laid thereon. When construction is carried out in a low-temperature environment, especially in winter in mountainous areas, the wind speed is high, the asphalt mixture dissipates heat quickly, and the temperature of the underlying layer is relatively low. All these factors pose a severe test to the construction quality of the asphalt mixture. The void ratio of the large-void asphalt mixture is larger than that of the conventional mixture, it dissipates heat faster, and it has a higher requirement for the construction temperature. Due to insufficient construction temperature and substandard construction quality, the situation of large-void asphalt pavement rework often occurs.

[0003] At present, warm-mixing technology is generally used for mixture construction in a low-temperature environment, which can reduce the production temperature of the mixture by 15℃ to 30℃, to a certain extent, alleviating the impact of low temperature on the construction quality of the asphalt pavement. In addition, when performing in-situ hot recycling, a heating machine needs to be used to heat the old pavement, but the heating temperature is as high as 200℃ or above, the purpose is to soften the original pavement material to achieve the effect of raking, mixing and re-paving. In the process of conventional asphalt pavement construction, there is no method of heating the underlying layer to improve the construction quality.

[0004] Although the warm-mixing technology improves the construction quality of the mixture at a lower temperature to a certain extent, it cannot solve the problems of fast heat dissipation of the mixture and low temperature of the underlying layer in a low-temperature environment. The existing heating process of the heating machine takes the road surface temperature as the control index, and the heating temperature is high to make the pavement material fully soften. However, when normal construction is carried out, the pavement does not need to be heated to a very high temperature, only the normal road surface temperature in summer, i.e. about 60℃, is needed. In addition, most warm-mixing agents have an adverse effect on the road performance and durability of the asphalt mixture. Moreover, in a low-temperature environment in winter, when the air temperature is lower than 5℃, the asphalt mixture cannot be constructed, even if the warm-mixing asphalt mixture cannot be constructed. Therefore, it is necessary to develop an asphalt mixture with high heat storage and slow heat dissipation to meet the needs of low-temperature construction.

[0005] CONTENT OF THE APPLICATION

[0006] The application aims to provide a heat storage type large-void asphalt mixture, a preparation method and a low-temperature environment construction method.

[0007] The embodiment of the application is implemented by the following technical scheme: the heat storage type large-void asphalt mixture comprises 100 parts of large-void asphalt mixture, 3-7 parts of steel slag powder and plant-based phase change material.

[0008] The application further provides a preparation method of the heat storage type large-void asphalt mixture, comprising the following steps:

[0009] (1) heat each batch of aggregate to 180-210 DEG C, pour into the stirring cylinder according to the set proportion, stir for 10-15 s, then pour high-viscosity asphalt with a temperature of 150-170 DEG C, stir for 5-10 s, and obtain the large-void asphalt mixture;

[0010] (2) heat the steel slag powder to 180-210 DEG C, pour into the stirring cylinder according to the set proportion, and stir for 35-40 s;

[0011] (3) heat the plant-based phase change material to 70-90 DEG C, pour into the stirring cylinder according to the set proportion, and stir for 5-10 s, and obtain the heat storage type large-void asphalt mixture.

[0012] Further, the steel slag powder is ground from steel slag, has a particle size of less than 0.15 mm, and has a specific heat capacity of 1200-1500 J / (kg* DEG C).

[0013] Further, the plant-based phase change material is a wax-like or oil-like material extracted from broken plant waste, and the main component is high-carbon fatty alkyl alcohol.

[0014] Further, the plant-based phase change material has a melting peak temperature of 70-90 DEG C, a latent heat of 200-250 kJ / kg, and a specific heat capacity of 1500-2000 J / (kg* DEG C).

[0015] Further, the determination of the amount of plant-based phase change material comprises the following steps:

[0016] (1) calculate the specific surface area (m 2 / kg) of the aggregate and steel slag powder mixture = (0.41a+0.41b+0.82c+1.64d+2.87e+6.14f+12.29g+32.77h) / 10 2

[0017] In the formula: a, b, c, d, e, f, g, h respectively represent the mass percentage of the aggregate and steel slag powder mixture through 19mm, 4.75mm, 2.36mm, 1.18mm, 0.6mm, 0.3mm, 0.15mm and 0.075mm sieve hole.

[0018] (2) selecting the film thickness of the plant-based phase change material in the range of 12-16 mu m, preferably the film thickness is 14 mu m;

[0019] (3) calculating the plant-based phase change material dosage (%) = plant-based phase change material film thickness x specific surface area of the aggregate and steel slag powder mixture x plant-based phase change material density (g / cm 3 ) / 10.

[0020] The application also provides a construction method of the heat storage type large-void asphalt mixture in a low-temperature environment, which comprises the following steps:

[0021] (1) preparing the heat storage type large-void asphalt mixture, and the mixture temperature should be kept between 170-185 DEG C; when the construction air temperature is lower than 0 DEG C, the warm mix technology is used to prepare the large-void asphalt mixture;

[0022] (2) transporting the heat storage type large-void asphalt mixture to the construction site, and the on-site temperature is controlled between 160 DEG C-180 DEG C;

[0023] (3) before paving the heat storage type large-void asphalt mixture, the lower bearing layer is preheated to 60 DEG C by using a heating machine;

[0024] (4) after the heating machine, a heat preservation tarpaulin automatic winding device is followed, the heat preservation tarpaulin is used to fully cover the road section passed by the heating machine, and when the paver reaches the road section, the heat preservation tarpaulin is wound up;

[0025] (5) the mixture is uniformly paved on the lower bearing layer, the paver speed is consistent with the heating machine speed, and the control is 1-3 m / min, so that the whole operation surface construction is coordinated;

[0026] (6) the mixture is compacted by using a road roller, the road roller should follow the paving and execute the slow pressure following, the water amount is reduced as much as possible according to the non-stick wheel standard, so as to avoid the temperature loss caused by the water.

[0027] Further, the heat Q required for increasing the surface temperature of the lower bearing layer to 60 DEG C in the preheating process is Q=c x p x v x (60-t0);

[0028] In the formula: the heat Q is in units of J, the specific heat capacity c is in units of J / (kg x DEG C), the bulk density p is in units of 10 3 kg / m 3 , the volume v is in units of m 3 , and the surface temperature t0 of the lower bearing layer is in units of DEG C.

[0029] Further, the speed of the heating machine is set as V, and the power is P, and both of them need to meet the relationship: P / V=Q / L.

[0030] In the formula, the power P is in units of J / s, the speed V is in units of m / s, and the construction section length L is in units of m.

[0031] Further, the specific heat capacity of the heat storage type large-void asphalt mixture is 1100-1300 J / (kg*℃), and the bulk density p is 2.1*10 3 kg / m 3 .

[0032] The technical scheme of the embodiment of the present application has at least the following advantages and beneficial effects:

[0033] (1) The large-void asphalt mixture is composed of aggregate, mineral powder and asphalt in a certain proportion, and the mineral powder is not heated during the preparation process, and the specific heat capacity of the mixture is generally 750-1150 J / (kg*℃). The present application does not use mineral powder, but replaces it with steel slag powder with high specific heat capacity, and the steel slag powder needs to be heated during the preparation process of the mixture. The specific heat capacity of the steel slag powder is 1200-1500 J / (kg*℃), which is more than 50% higher than the specific heat capacity of general rock, which is 800-1000 J / (kg*℃). In addition, the use of high specific heat capacity plant-based phase change material, the specific heat capacity of the heat storage type large-void asphalt mixture reaches 1100-1300 J / (kg*℃), which absorbs a large amount of heat during the heating process, so that the heat stored in the prepared mixture is larger.

[0034] (2) Compared with the normal asphalt mixture mixing process, the present application adds a process, that is, the flow-like plant-based phase change material is added to the mixture and mixed, the plant-based phase change material is wrapped on the surface of the mixture particles, absorbs heat and changes its own properties, reduces the heat loss of the mixture, and further slows down the heat loss rate of the mixture. Moreover, during the paving and rolling process of the mixture, when the surrounding temperature is low, the heat absorbed by the plant-based phase change material will be automatically released, which plays a role in heating the mixture, and further ensures the construction temperature of the mixture.

[0035] (3) The surface temperature of the lower bearing layer is increased to a stable 60℃, which reaches the road surface temperature level in summer construction, ensures that the temperature of each link of the construction reaches the control standard, improves the construction quality of the large-void asphalt mixture, and puts forward the control standard of the power and speed of the heating machine.

[0036] (4) Combined with the use of heat preservation tarpaulin and warm mixing technology, the paving and rolling effect of the large-void asphalt mixture in low temperature environment is further ensured. DETAILED DESCRIPTION

[0037] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below. If specific conditions are not indicated in the embodiments, the conventional conditions or the conditions suggested by the manufacturers are adopted. If the manufacturers of the reagents or instruments are not indicated, the conventional products that can be purchased in the market are adopted.

[0038] Embodiment 1

[0039] The heat storage type large-void asphalt mixture is composed of large-void asphalt mixture, steel slag powder and plant-based phase change material, and the composition ratio is large-void asphalt mixture 100 parts, steel slag powder 5 parts and plant-based phase change material 5 parts. The preparation process of the heat storage type large-void asphalt mixture comprises the following steps:

[0040] (1) Each batch of aggregate is heated to 200℃, and is put into the stirring cylinder according to the set ratio, and is stirred for 12s, and then high-viscosity asphalt with a temperature of 160℃ is put in, and is stirred for 10s, to obtain the large-void asphalt mixture.

[0041] The ratio of each batch of raw material used in the large-void asphalt mixture is 5-10mm coarse aggregate: 10-15mm coarse aggregate: 0-3mm fine aggregate: high-viscosity asphalt = 45:40:10:5. (The coarse aggregate refers to broken stone, broken gravel, screened gravel and slag, and the fine aggregate refers to natural sand, artificial sand (including machine-made sand) and stone chips, and the same below.)

[0042] (2) The steel slag powder is heated to 200℃, and is put into the stirring cylinder according to the set ratio, and is stirred for 40s.

[0043] (3) The plant-based phase change material is heated to 74℃, and is put into the stirring cylinder according to the set ratio, and is stirred for 10s, to obtain the heat storage type large-void asphalt mixture.

[0044] The ratio of large-void asphalt mixture: steel slag powder: plant-based phase change material = 100:5:5.

[0045] The steel slag powder is ground from steel slag, and the particle size is less than 0.15mm, and the specific heat capacity is 1400J / (kg×℃).

[0046] The plant-based phase change material is a wax-like or oil-like material extracted from broken plant waste, and the main component is octacosanol.

[0047] The melting peak temperature of the plant-based phase change material is 74℃, the latent heat is 234kJ / kg, and the specific heat capacity is 1800J / (kg×℃).

[0048] Embodiment 2

[0049] The heat storage type large-void asphalt mixture prepared in Example 1 is constructed in a low temperature environment according to the following steps:

[0050] (1) The heat storage type large-void asphalt mixture is prepared, and the temperature of the mixture should be kept at 170-185°C;

[0051] (2) The mixture is transported to the construction site, and the temperature on site is controlled at 160-180°C;

[0052] (3) Before the mixture is spread, the lower bearing layer is preheated to 60°C by using a heating machine;

[0053] (4) A heating machine is followed by an automatic rolling device of heat preservation tarpaulin, and the heat preservation tarpaulin is fully covered after the heating machine passes the road section, and the heat preservation tarpaulin is rolled up when the spreader reaches the road section;

[0054] (5) The mixture is uniformly spread on the lower bearing layer, and the speed of the spreader is kept consistent with the speed of the heating machine, and the speed is controlled at 1-3 m / min to make the whole working surface construction coordinated;

[0055] (6) The mixture is compacted by using a road roller, and the road roller should follow the spreader and perform slow compaction, and the water amount is reduced as much as possible according to the standard of non-stick wheel to avoid temperature loss caused by water.

[0056] The construction method of the prepared heat storage type large-void asphalt mixture in a low temperature environment, the heat Q required for increasing the surface temperature of the lower bearing layer to 60°C in the preheating process is Q=c×ρ×v×(60-t0)=1200×2100×75×(60-15)=8.505×10 9 J.

[0057] In the formula, the heat Q is in J, the specific heat capacity c is in J / (kg×℃) and is 1200 J / (kg×℃), the bulk density ρ is in 10 3 ×kg / m 3 and is 2100 kg / m 3 , the volume v is in m 3 and is 75 m 3 , and the surface temperature t0 of the lower bearing layer is in ℃ and is 15 ℃.

[0058] The construction method of the prepared heat storage type large-void asphalt mixture in a low temperature environment, the speed of the heating machine is set as V, and the power is P, and both of them should satisfy the following formula:

[0059] P / V=Q / L, i.e. 1.06×10 7 / V=8.505×10 9 / 2000, i.e. V=2.5 m / s.

[0060] P = 1.06 x 10 7 J / s; V = 1.06 x 10 3 J / s; L = 2000 m.

[0061] The prepared heat storage type large-void asphalt mixture has a specific heat capacity c of 1200 J / (kg x °C) and a bulk density p of 2.1 x 10 3 kg / m 3 .

[0062] Comparative Example 1

[0063] A large-void asphalt mixture is prepared according to 5-10 mm coarse aggregate: 10-15 mm coarse aggregate: 0-3 mm fine aggregate: mineral powder: high-viscosity asphalt = 45:40:10:5:5, and the coarse aggregate, fine aggregate, and high-viscosity asphalt used are the same as in Example 1.

[0064] Comparative Example 2

[0065] The large-void asphalt mixture prepared in Comparative Example 1 is constructed in a low-temperature environment according to the following steps:

[0066] (1) The large-void asphalt mixture is prepared, and the mixture temperature should be maintained at 170-185°C;

[0067] (2) The mixture is transported to the construction site, and the on-site temperature is controlled at 160-180°C;

[0068] (3) The mixture is uniformly spread on the underlying layer, and the spreading speed is controlled at 1-3 m / min;

[0069] (4) The mixture is compacted by a road roller, and the road roller should follow the spreading and perform slow compaction, and the water amount should be minimized to prevent temperature loss caused by water.

[0070] Experimental Example 1

[0071] The temperatures of the large-void asphalt mixtures in each construction step of Example 2 and Comparative Example 2 are tested, and the results are shown in Table 1. As shown in Table 1, the on-site temperature of the heat storage type large-void asphalt mixture is higher than that of the conventional mixture by more than 10°C under the condition that the mixture temperatures of the two mixtures are the same. Since the underlying layer is preheated to increase from 15°C to 60°C during the construction of the heat storage type mixture, the spreading and compaction temperature of the mixture is about 20°C higher than that of the conventional mixture.

[0072] Table 1 Comparison of construction temperatures of Example 2 and Comparative Example 2

[0073]

[0074] Experimental Example 1

[0075] According to the method of T0924-2008 core drilling test pavement compaction degree in JTG 3450-2019 “Highway Subgrade and Pavement Field Test Regulations”, the compaction degrees of the pavements paved by Example 2 and Comparative Example 2 are tested, and the specific data are shown in Table 2. As shown in Table 2, the pavement paved by the heat storage type large-void asphalt mixture has obvious construction compaction effect, and the compaction degree is improved by 2-3 percentage points compared with the pavement paved by the conventional mixture, and both meet the specification requirements. However, the pavement paved by the conventional mixture cannot basically meet the specification requirements due to low construction temperature.

[0076] Table 2 Comparison of compaction degrees of Example 2 and Comparative Example 2

[0077]

[0078] The above only provides preferred embodiments of the present application and is not intended to limit the present application. The present application can have various modifications and changes for those skilled in the art. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A heat-storing large-void asphalt mixture, characterized by, The heat storage type large-void asphalt mixture comprises 100 parts of large-void asphalt mixture, 3-7 parts of steel slag powder and 4-6 parts of plant-based phase change material. The steel slag powder is ground from steel slag and has a particle size less than 0.15 mm and a specific heat capacity of 1200-1500 J / (kg×℃). The plant-based phase change material is a wax-like or oil-like material extracted from broken plant waste and mainly comprises high-carbon fatty alkyl alcohol. The large-void asphalt mixture does not use mineral powder, which is replaced by steel slag powder with high specific heat capacity.

2. The heat-accumulating large-void asphalt mixture according to claim 1, characterized by, The plant-based phase change material has a melting peak temperature of 70-90℃, latent heat of 200-250 kJ / kg and specific heat capacity of 1500-2000 J / (kg×℃).

3. The method of producing a hot storage type large void asphalt mixture according to any one of claims 1 to 2, characterized in that, The method comprises the following steps: (1) heating each batch of aggregate to 180-210℃, pouring into a stirring cylinder according to a set proportion, stirring for 10-15 s, then pouring high-viscosity asphalt with a temperature of 150-170℃, and stirring for 5-10 s to obtain the large-void asphalt mixture; (2) heating the steel slag powder to 180-210℃, pouring into the stirring cylinder according to a set proportion, and stirring for 35-40 s; (3) heating the plant-based phase change material to 70-90℃, pouring into the stirring cylinder according to a set proportion, and stirring for 5-10 s to obtain the heat storage type large-void asphalt mixture.

4. The construction method of the hot storage type large void asphalt mixture in a low temperature environment according to any one of claims 1-2, characterized in that, The method comprises the following steps: (1) preparing the heat storage type large-void asphalt mixture, and keeping the temperature of the mixture at 170-185℃, when the construction air temperature is lower than 0℃, using warm-mixing technology to prepare the large-void asphalt mixture; (2) transporting the heat storage type large-void asphalt mixture to the construction site, and controlling the on-site temperature to be 160-180℃; (3) preheating the lower bearing layer to 60℃ using a heating machine before paving the heat storage type large-void asphalt mixture; (4) following the heating machine with an automatic rolling device of heat preservation tarpaulin, fully covering the road section passed by the heating machine with the heat preservation tarpaulin, and rolling up the heat preservation tarpaulin when the paver reaches the road section; (5) uniformly paving the mixture on the lower bearing layer, keeping the speed of the paver consistent with the speed of the heating machine, and controlling the speed to be 1-3 m / min to make the whole working surface construction coordinated; (6) compacting the mixture using a road roller, keeping the road roller close to the paver, performing slow compaction, and reducing the water amount as much as possible to avoid temperature loss caused by water.

5. The construction method of the hot-stored large void asphalt mixture in a low temperature environment according to claim 4, characterized in that, The heat Q required for increasing the surface temperature of the lower bearing layer to 60℃ in the preheating process is c×ρ×v×(60-t0); In the formula, the heat Q is in units of J, the specific heat capacity c is in units of J / (kg x °C), the bulk volume density p is in units of 10 3 kg / m 3 , the volume v is in units of m 3 , and the surface temperature t0 of the lower layer is in units of °C.

6. The construction method of the hot-stored large void asphalt mixture according to claim 5, characterized in that, The speed of the heating machine is V and the power is P, and they need to satisfy the relationship P / V=Q / L. In the formula, the power P is in J / s, the speed V is in m / s, and the length L of the construction road section is in m.

7. The construction method of the hot storage type large void asphalt mixture according to claim 4, characterized in that, The specific heat capacity of the heat storage type large-void asphalt mixture is 1100-1300 J / (kg*℃), and the bulk density ρ is 2.1*10 3 kg / m 3 .

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