A gradient heat conduction directional regulation type pouring type composite asphalt pavement surface layer structure

Abstract

The application discloses a gradient heat conduction directional regulation type filling type composite asphalt pavement surface layer structure and belongs to the field of pavement materials. The application aims at solving the problems of the current filling type composite asphalt pavement, such as weak heat conduction performance, poor road performance and the inability to conveniently realize the directional heat conduction of heat in the asphalt pavement surface layer in different regions. The application prepares composite cement grouting materials containing different thermal conductivities, fills the multi-layer composite cement materials in the large-void matrix asphalt mixture, and then prepares the filling type composite asphalt mixture with the gradient heat conduction function, and applies the filling type composite asphalt mixture to different layer positions of the pavement surface layer structure, so as to realize the directional heat conduction of heat in the asphalt pavement in different regions, and achieve the purposes of relieving the urban heat island effect and protecting the frozen soil structure.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of pavement materials, and particularly relates to a gradient heat conduction directional regulation type filling type composite asphalt pavement surface layer structure. BACKGROUND

[0002] Asphalt pavement is widely used due to its advantages such as safety, comfort and convenient construction. However, as a typical black pavement, asphalt pavement has high heat absorption capacity, and the heat collection in the pavement structure is high and the heat dissipation is slow, which will exacerbate the urban heat island effect, increase energy consumption, and affect the health of residents. In addition, in plateau permafrost regions, the inefficient heat dissipation characteristics of asphalt pavement will also damage the permafrost structure, affect the service life of the asphalt pavement, and further cause serious ecological damage and loss of life and property.

[0003] The filling type asphalt pavement is a composite pavement structure formed by filling the voids of open-graded asphalt mixture with cement-based grouting material, which combines the flexibility of asphalt material and the rigidity of cement-based material, and has strong bearing capacity and service life. Compared with cement concrete pavement or asphalt concrete pavement, the filling type asphalt pavement has moderate flexibility and rigidity, and has broad application prospects. However, the current filling type composite asphalt pavement has the problems of weak heat conduction performance, poor road performance, and inability to conveniently realize directional heat conduction of heat in the asphalt pavement surface layer in different regions. SUMMARY

[0004] The present application provides a gradient heat conduction directional regulation type filling type composite asphalt pavement surface layer structure to solve the problems of weak heat conduction performance, poor road performance and inability to conveniently realize directional heat conduction of heat in the asphalt pavement surface layer in different regions.

[0005] The present application provides a gradient heat conduction directional regulation type filling type composite asphalt pavement surface layer structure,

[0006] The present application sets two kinds of pavement structures, the first kind is a directional heat induction structure of "small on top and large on bottom" established based on the grouting composite gradient heat conduction method, the heat induction layer laid between the pavement surface layers and the reflective layer grouting material laid on the top of the upper pavement surface layer to relieve the urban heat island effect; the second kind is a directional heat induction structure of "large on top and small on bottom" established based on the grouting composite gradient heat conduction method, the heat induction layer laid between the pavement surface layers, the reflective layer grouting material laid on the top of the upper pavement surface layer and the high thermal resistance layer laid on the bottom of the lower pavement surface layer to protect the permafrost structure.

[0007] The asphalt pavement surface layer for mitigating the urban heat island effect is divided into upper and lower double-layer structures; the upper layer is formed by sequentially injecting low thermal conductivity grout and reflective low thermal conductivity grout into the skeleton; the lower layer is formed by sequentially injecting high-content high thermal conductivity grout and low-content high thermal conductivity grout into the skeleton; a thermally induced bonding layer is laid between the upper and lower layers.

[0008] The asphalt pavement surface layer for protecting the frozen soil structure is divided into upper and lower double-layer structures; the upper layer is formed by sequentially injecting high thermal conductivity grout and reflective high thermal conductivity grout into the skeleton; the lower layer is formed by sequentially injecting high-volume low thermal conductivity grout and low-volume low thermal conductivity grout into the skeleton; a thermally induced bonding layer is laid between the upper and lower layers; and a high thermal resistance bonding layer is laid at the bottom of the lower layer.

[0009] Specifically, the asphalt pavement surface layer is divided into upper and lower double-layer structures. For the "smaller upper layer and larger lower layer" structure, the upper part of the upper layer is a reflective low thermal conductivity grout, and the lower part is a low thermal conductivity grout. The amount of low thermal conductivity powder in the upper layer is more than that in the lower layer, and the injection depth ratio of the two grouts is 1:1. The upper part of the lower layer is a low amount of high thermal conductivity grout, and the lower part is a high amount of high thermal conductivity grout. The injection depth ratio of the two grouts is 1:1. A thermally induced bonding layer is laid between the upper and lower layers.

[0010] For the "larger top, smaller bottom" structure, the upper part of the upper layer is a reflective high thermal conductivity grout, and the lower part is a high thermal conductivity grout. The amount of high thermal conductivity powder in the upper layer is greater than that in the lower layer, and the grouting depth ratio of the two grouts is 1:1. The upper part of the lower layer is a low thermal conductivity grout with a low content, and the lower part is a high thermal conductivity grout with a high content. The grouting depth ratio of the two grouts is 1:1. A thermally induced bonding layer is laid between the upper and lower layers, and a high thermal resistance bonding layer is laid at the bottom of the lower layer.

[0011] The skeleton is made of large-void matrix asphalt mixture, and its porosity is controlled between 20% and 35%.

[0012] The high thermal conductivity grout is prepared according to the following process: First, high thermal conductivity compound cement, modified high thermal conductivity powder, microspheres, quartz sand, retarder, early strength agent, defoamer, expanding agent and workability regulator are mixed together and stirred until uniform to obtain a dry mixture; then, water-reducing agent is added to water and stirred evenly for 1 min to 3 min; finally, the aqueous solution containing water-reducing agent is added to the dry mixture and stirred for another 3 min to 5 min to obtain the high thermal conductivity grout ready for use.

[0013] The low-thermal-conductivity grouting material is prepared according to the following process: first, low-thermal-conductivity composite cement, modified low-thermal-conductivity powder, microbeads, quartz sand, a retarder, an early strength agent, a defoaming agent, an expansive agent and a workability regulator are placed together and dry-mixed until uniform to obtain a dry-mixed mixture; then, a water reducing agent is stirred in water until uniform, and the stirring is continued for 1-3 minutes; finally, the water solution containing the water reducing agent is added to the dry-mixed mixture and the stirring is continued for 3-5 minutes to obtain the low-thermal-conductivity grouting material ready for use.

[0014] The coloring agent is added during the dry-mixing of the high-thermal-conductivity grouting material or the low-thermal-conductivity grouting material and is stirred until uniform to obtain a dry-mixed mixture, and the stirring is continued for 3-5 minutes after the addition of the water solution of the water reducing agent to obtain the reflective high-thermal-conductivity composite cement grouting material or the reflective low-thermal-conductivity composite cement grouting material ready for use.

[0015] The composite cement grouting material is prepared according to the following process:

[0016] (1) Materials:

[0017] The materials required for the preparation of the composite cement grouting material include cement, sand, mineral admixtures, water and admixtures (a water reducing agent, a retarder, an early strength agent, a defoaming agent, an expansive agent, a workability regulator and a coloring agent). The addition of the admixtures can ensure the gradient thermal conductivity performance efficiency of the grouting type composite asphalt pavement and good road performance of the grouting type composite asphalt pavement.

[0018] The cement includes ordinary portland cement (42.5 MPa), sulphoaluminate cement (42.5 MPa) and ammonium magnesium phosphate cement (42.5 MPa). In order to improve the performance of the composite cement grouting material and the grouting type composite pavement material, the above three kinds of cement are used to prepare two kinds of composite cement for the preparation of the composite cement grouting material. The first kind of composite cement is low-thermal-conductivity composite cement, which is composed of ordinary portland cement and sulphoaluminate cement, and the mixing ratio of the two is ordinary portland cement:sulphoaluminate cement=1:(1-5); the second kind of composite cement is high-thermal-conductivity composite cement, which is composed of ordinary portland cement and ammonium magnesium phosphate cement, and the mixing ratio of the two is ordinary portland cement:ammonium magnesium phosphate cement=1:(1-5).

[0019] The sand is 30-200 mesh quartz sand, which can be divided into three grades of 30-50 mesh, 50-100 mesh and 100-200 mesh, and the mass ratio of the three grades is 1:(0.1-0.3):(0.4-0.6), and the added amount of the quartz sand is 80%-125% of the mass of the composite cement;

[0020] The mineral admixture comprises a heat-conducting powder, a heat-conducting powder modifier and microbeads, wherein the heat-conducting powder comprises high-heat-conducting powder and low-heat-conducting powder, the high-heat-conducting powder can be selected from graphite or silicon carbide, and the low-heat-conducting powder can be selected from floating beads or hollow glass microbeads; the graphite has a mesh number of 800-1200 and a heat-conducting coefficient of 125-140 W / (m*K), the silicon carbide has a mesh number of 100-300 and a heat-conducting coefficient of 400-490 W / (m*K), the floating beads have a mesh number of 200-400 and a heat-conducting coefficient of 0.054-0.095 W / (m*K), and the hollow glass microbeads have a mesh number of 60-100 and a heat-conducting coefficient of 0.03-0.045 W / (m*K); in order to improve the wettability and dispersibility of the heat-conducting powder in the grouting material and improve the interface bonding degree of the heat-conducting powder and the grouting material, for the high-heat-conducting powder, the high-heat-conducting powder is pre-modified by using a sodium hydroxide solution with a concentration of 2-4 mol / L (the mass ratio of the high-heat-conducting powder to the sodium hydroxide solution is 1:1.2-1.5), and then the pre-modified high-heat-conducting powder is re-modified by using a KH-560 silane coupling agent with a concentration of 0.03-0.05 mol / L (the mass ratio of the high-heat-conducting powder to the KH-560 silane coupling agent is 1:0.008-0.012), and for the low-heat-conducting powder, the low-heat-conducting powder is directly modified by using a KH-560 silane coupling agent with a concentration of 0.03-0.05 mol / L (the mass ratio of the low-heat-conducting powder to the KH-560 silane coupling agent is 1:0.008-0.012), in the above process, ethanol with a concentration of 95%-98% is used as a dispersion solution of the KH-560 silane coupling agent, and the water used is deionized water; in addition, the microbeads can enhance the interface bonding degree between the grouting materials, improve the flowability of the grouting materials and improve the overall strength of the grouting materials due to the continuous particle size distribution and the non-porous characteristics of the microbeads. In summary, the added mass of the mineral admixture is 0%-20% of the mass of the compounded cement, the mass ratio of the heat-conducting powder to the microbeads is 1:(0.8-2), the added mass of water is 30%-70% of the mass of the compounded cement, and the added mass of the water-reducing agent is 0.1%-0.2% of the mass of the compounded cement.

[0021] The added mass of water is 30-70% of the mass of the compounded cement.

[0022] The types, functions and corresponding mixing ratios of the admixtures are as follows.

[0023] The water-reducing agent is early-strength polycarboxylic acid water-reducing agent, which can increase the flowability of the grouting material and enhance the early strength of the grouting material, and the added mass of the water-reducing agent is 0.1-0.2% of the mass of the compounded cement.

[0024] The retarder is prepared from sodium gluconate and borax, which can prolong the setting time of the grouting material, improve the grouting efficiency, and the added mass is 0~0.06% of the mass of the cement, and the mass ratio of sodium gluconate to borax is 1:2~5;

[0025] The early strength agent is lithium carbonate early strength agent, which can enhance the early strength of the grouting material, and the added mass is 0~0.1% of the mass of the cement;

[0026] The defoaming agent is Mingling P 803 defoaming agent, which can remove the foam in the grouting material, so that the internal structure of the grouting material is more compact, and the added mass is 0.02~0.06% of the mass of the composite cement grouting material;

[0027] The expansion agent is calcium sulphoaluminate expansion agent, which can improve the shrinkage phenomenon in the grouting material and improve the crack resistance of the grouting material, and the added mass is 3~6% of the mass of the cement;

[0028] The workability regulator is composed of BASF anti-settling agent and low-viscosity hydroxyethyl methyl cellulose ether, which can improve the settling performance of the grouting material and improve the water retention performance of the grouting material, and the added mass is 0.03~0.06% of the mass of the composite cement grouting material, and the mixing ratio of BASF anti-settling agent to hydroxyethyl methyl cellulose ether is 1:1~2;

[0029] The coloring agent is a mixture of titanium dioxide pigment and fixing agent, which can improve the reflectivity of the grouting material and reduce the surface temperature of the poured composite asphalt pavement, and the added mass is 1~4% of the mass of the composite cement grouting material.

[0030] (2) Preparation process:

[0031] According to the above-mentioned materials, three kinds of composite cement grouting materials are prepared, including high-thermal-conductivity composite cement grouting material, low-thermal-conductivity composite cement grouting material and reflective composite cement grouting material, each kind of composite grouting material follows the principle of using and mixing, and the reflective composite cement grouting material is prepared by adding a coloring agent on the basis of the high-thermal-conductivity composite cement grouting material and the low-thermal-conductivity composite cement grouting material, and is divided into reflective high-thermal-conductivity composite cement grouting material and reflective low-thermal-conductivity composite cement grouting material.

[0032] In the present application, the large-void matrix asphalt mixture is prepared

[0033] (1) Material:

[0034] The materials required for preparing the large-void matrix asphalt mixture include asphalt, aggregate, mineral powder and fiber.

[0035] The asphalt is SBS / rubber composite modified asphalt, which mainly plays a role of cementation in the large-void matrix asphalt mixture, and can significantly improve the service performance of the large-void matrix asphalt mixture, wherein the SBS is a linear modifier, accounts for 3-8% of the mass of the asphalt, the rubber is 40-mesh rubber, accounts for 10-20% of the mass of the asphalt, and the dosage of the SBS / rubber composite modified asphalt is 2-4% of the asphalt mixture.

[0036] The aggregate is basalt coarse and fine aggregate, which can be divided into four grades of 0-5mm, 5-10mm, 10-15mm and 15-20mm, mainly plays a role of skeleton in the large-void matrix asphalt mixture, and the dosage of the aggregate is 85-92% of the asphalt mixture.

[0037] The mineral powder is limestone mineral powder, which can improve the interaction between the large-void matrix asphalt mixtures, and the dosage of the mineral powder is 5-20% of the asphalt mixture.

[0038] The fiber is flocculent lignin fiber, which can improve the adhesion between asphalt-aggregate and asphalt-asphalt, and the dosage of the fiber is 0.2-0.4% of the asphalt mixture.

[0039] (2) Preparation process:

[0040] The mixing ratio design of each component material of the large-void matrix asphalt mixture is carried out by using the volume design method, the asphalt mixture gradation is a continuous open-graded "skeleton-void structure", and the void ratio of the prepared large-void matrix asphalt mixture is 20-35%.

[0041] Specifically, first, the asphalt, aggregate, mineral powder and fiber are weighed according to the designed mixing ratio and placed in an oven for preheating; then, the preheated aggregate, fiber, asphalt and mineral powder are sequentially placed in a mixing pot for mixing, the mixing temperature is 160-180 DEG C, and the mixing time is 360-450s; then, the rotary compactor or hydraulic track sample forming machine is used for compaction molding of the large-void matrix asphalt mixture to obtain a cylindrical test piece or a track plate test piece, and the compaction temperature is 150-180 DEG C.

[0042] In the present application, the preparation of the pouring type composite asphalt mixture

[0043] (1) Material:

[0044] The materials required for the preparation of the pouring type composite asphalt mixture include high-thermal-conductivity composite cement grouting material, low-thermal-conductivity composite cement grouting material, reflective high-thermal-conductivity composite cement grouting material, reflective low-thermal-conductivity composite cement grouting material and large-void matrix asphalt mixture.

[0045] (2) Preparation process:

[0046] The present application discloses a preparation method of a gradient heat conduction filled composite asphalt mixture, which comprises the following steps: preparing a large-void matrix asphalt mixture as a skeleton, and preparing a composite cement grout with different thermal conductivities as a filler of the skeleton voids.

[0047] In order to form a gradient heat conduction structure in the large-void matrix asphalt mixture specimen, the present application determines the grout with different thermal conductivities according to the different contents of the heat conduction powder in the composite cement grout, and then the grout with different thermal conductivities is sequentially layered and filled into the large-void matrix asphalt mixture specimen, and the large-void matrix asphalt mixture forms the solidified layers of the grout with different thermal conductivities.

[0048] Specifically, the present application takes the high-thermal-conductivity composite cement grout containing graphite powder as an example, and prepares two high-thermal-conductivity composite cement grouts with different thermal conductivities by changing the content of the graphite powder (low content and high content) in the high-thermal-conductivity composite cement grout; then, the bottom surface and the side surface of the large-void matrix asphalt mixture specimen prepared in the second step are sealed by using a plastic wrap and adhesive tape, and the top surface is reserved for grout filling; subsequently, the high-thermal-conductivity composite cement grout containing the high-content graphite powder is filled into the cooled large-void matrix asphalt mixture specimen, and the filling depth is half of the height of the large-void matrix asphalt mixture specimen; after the high-thermal-conductivity composite cement grout containing the high-content graphite powder is initially cured, the high-thermal-conductivity composite cement grout containing the low-content graphite powder is filled into the mixture specimen, and the filling depth is also half of the height of the large-void matrix asphalt mixture specimen; in this process, the surface excess grout is scraped off by using a brush until the mixture surface structure is exposed; finally, the specimen is placed into a standard cement curing box for curing, and the gradient heat conduction filled composite asphalt mixture can be obtained after the two high-thermal-conductivity composite cement grouts are solidified and hardened.

[0049] Preparation of the gradient heat conduction filled composite asphalt pavement structure in the present application

[0050] (1) Materials:

[0051] The materials required for preparing the gradient heat conduction poured composite asphalt pavement structure include high heat conduction composite cement grouting material, low heat conduction composite cement grouting material, reflective high heat conduction composite cement grouting material, reflective low heat conduction composite cement grouting material, large-void matrix asphalt mixture, heat-induced bonding material and high thermal resistance bonding material, wherein the gradation of the large-void matrix asphalt mixture is a continuous open-graded'skeleton-void structure', and the void ratio is between 20% and 35%; the heat-induced bonding material is SBS / rubber composite modified asphalt and graphite, which are stirred in a molten state at 140-160 DEG C using a high-speed shearing machine (stirring speed: 1000-2000 r / min, stirring time: 20-40 min), and the mixing ratio of SBS / rubber composite modified asphalt and graphite is 1:0.10-0.25; and the high thermal resistance bonding material is SBS / rubber composite modified asphalt and floating beads, which are stirred in a molten state at 140-160 DEG C using a high-speed shearing machine (stirring speed: 1000-2000 r / min, stirring time: 20-40 min), and the mixing ratio of SBS / rubber composite modified asphalt and floating beads is 1:0.10-0.25.

[0052] (2) Preparation process:

[0053] When the thermal conductivities of different structural layers in the pavement are distributed in a certain gradient, the heat in the pavement tends to conduct along the direction in which the thermal conductivity increases. According to the actual needs of directional heat conduction of heat in asphalt pavement in different regions, the heat flow in the pavement is controlled in a directional manner through reasonable pavement material and pavement structure design, so as to reduce pavement high temperature and heat accumulation, and thus achieve the purposes of relieving urban heat island effect and protecting frozen soil structure.

[0054] Therefore,

[0055] The present application comprises the following steps:

[0056] Compared with the prior art, the present application has the following beneficial effects:

[0057] The present application uses composite cement, mineral admixtures and additives to improve the performance of the composite cement grouting material, and indirectly improves the service performance of the poured composite asphalt pavement; at the same time, the modified high and low heat conduction powders with different mixing amounts are poured into the large-void matrix asphalt mixture by means of the high flow performance of the composite cement grouting material, which can improve the heat conduction effect of the heat in the asphalt pavement and the service performance of the asphalt pavement.

[0058] The application is a gradient heat conduction directional regulation type pouring composite asphalt pavement surface layer structure for relieving urban heat island effect and protecting frozen soil structure, the structure is prepared by high and low heat conduction powder and reflection colorant, and has different thermal conductivity, so that the heat in the asphalt pavement structure can be effectively transferred downward or upward transported, and the structure combines the heat conduction composite cement grout and the reflection composite cement grout, so that the purpose of relieving urban heat island effect and protecting frozen soil structure is better achieved.

[0059] In order to further understand the features and technical contents of the present application, please refer to the following detailed description of the present application and the accompanying drawings, however, the accompanying drawings are provided for reference and illustration only, and are not used to limit the present application. BRIEF DESCRIPTION OF DRAWINGS

[0060] Figure 1 is preparation of pouring composite asphalt mixture (taking high heat conduction composite cement grout containing graphite powder as an example);

[0061] Figure 2 is an "upper small and lower large" pavement structure for relieving urban heat island effect;

[0062] Figure 3 is an "upper large and lower small" pavement structure for protecting frozen soil. DETAILED DESCRIPTION

[0063] The present application will be described in detail below in combination with specific examples. The following examples will help the person skilled in the art to further understand the present application, and do not limit the present application in any form. It should be pointed out that, for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made. These all belong to the protection scope of the present application.

[0064] In this embodiment, different kinds of composite cement grout preparation is prepared according to the following steps:

[0065] The preparation process of the high-thermal-conductivity composite cement grout is as follows: first, high-thermal-conductivity composite cement prepared from ordinary Portland cement and ammonium magnesium phosphate cement (the mixing ratio of the two is 1:2), modified graphite powder (7% of the mass of the composite cement), microbeads (8% of the mass of the composite cement), three-grade quartz sand (100% of the mass of the composite cement, the three-grade mixing ratio is 30-50 mesh: 50-100 mesh: 100-200 mesh = 32:5:15), retarder (0.02% of the mass of the composite cement), early strength agent (0.03% of the mass of the composite cement), defoaming agent (0.03% of the mass of the composite cement), expansive agent (3% of the mass of the composite cement), and workability regulator (0.04% of the mass of the composite cement) are placed together and dry-mixed according to the designed ratio, and stirred uniformly (the stirring time is about 1-3 min), to obtain a mixed dry-mixed mixture; then, water reducing agent (0.15% of the mass of the composite cement) is stirred in water (60% of the mass of the composite cement) until uniform, and the stirring time is about 1-3 min; subsequently, the water solution containing the water reducing agent is added to the dry-mixed mixture and continues to be stirred for 5 min; finally, the prepared high-thermal-conductivity composite cement grout is grouted in a test mold coated with machine oil, to prepare compression test pieces (70.7x70.7x70.7mm) and flexural test pieces (40x40x160mm) respectively, and after the test pieces are formed, they are numbered and placed in a standard cement curing box (temperature 20℃, humidity 95%) for curing for 7 days.

[0066] The preparation process of the low thermal conductivity composite cement grout is as follows: first, the low thermal conductivity composite cement prepared from ordinary portland cement and sulphoaluminate cement (the mixing ratio of the two is 1:2), modified floating bead powder (7% of the mass of the composite cement), microbeads (8% of the mass of the composite cement), three-grade quartz sand meeting the mixing ratio (100% of the mass of the composite cement, the three-grade mixing ratio is 30-50 mesh: 50-100 mesh: 100-200 mesh = 32:5:15), retarder (0.02% of the mass of the composite cement), early strength agent (0.03% of the mass of the composite cement), defoaming agent (0.03% of the mass of the composite cement), expanding agent (3% of the mass of the composite cement) and workability regulator (0.04% of the mass of the composite cement) are placed together and dry-mixed according to the designed ratio, and the dry-mixed mixture is uniformly stirred (the stirring time is about 1-3 min) to obtain a uniformly mixed dry-mixed mixture; then, the water reducing agent (0.15% of the mass of the composite cement) is stirred in water (60% of the mass of the composite cement) until it is uniformly stirred, and the stirring time is about 1-3 min; then, the water solution containing the water reducing agent is added to the dry-mixed mixture and continues to be stirred for 5 min; finally, the prepared low thermal conductivity composite cement grout is poured into an oil-coated test mold to prepare compression test pieces (70.7x70.7x70.7mm) and bending test pieces (40x40x160mm), respectively, and the test pieces are numbered and placed in a standard cement curing box (temperature 20℃, humidity 95%) for curing for 7 days.

[0067] For the preparation of the reflective composite cement grout, the colorant (3% of the mass of the composite cement) is added to the dry-mixed mixture and stirred during the preparation of the high thermal conductivity composite cement grout or the low thermal conductivity composite cement grout, then the water solution containing the water reducing agent is added to the dry-mixed mixture and continues to be stirred for 5 min; finally, the prepared reflective high thermal conductivity composite cement grout or reflective low thermal conductivity composite cement grout is poured into an oil-coated test mold to prepare compression test pieces (70.7x70.7x70.7mm) and bending test pieces (40x40x160mm), respectively, and the test pieces are numbered and placed in a standard cement curing box (temperature 20℃, humidity 95%) for curing for 7 days.

[0068] The preparation process of the comparative composite cement grout is as follows: first, high-thermal-conductivity composite cement prepared from ordinary portland cement and ammonium magnesium phosphate cement (the mixing ratio of the two is 1:2), microbeads (15% of the mass of the composite cement), three-grade quartz sand (100% of the mass of the composite cement, the three-grade mixing ratio is 30-50 mesh: 50-100 mesh: 100-200 mesh = 32:5:15), a retarder (0.02% of the mass of the composite cement), an early strength agent (0.03% of the mass of the composite cement), a defoaming agent (0.03% of the mass of the composite cement), an expansive agent (3% of the mass of the composite cement), and a workability regulator (0.04% of the mass of the composite cement) are placed together and dry-mixed according to the designed ratio, and stirred for 1-3 min to obtain a uniformly mixed dry-mixed mixture; then, a water reducing agent (0.15% of the mass of the composite cement) is stirred in water (60% of the mass of the composite cement) until it is uniformly mixed, and stirred for 1-3 min; subsequently, the water solution containing the water reducing agent is added to the dry-mixed mixture and continues to be stirred for 3-5 min; finally, the prepared comparative composite cement grout is injected into a test mold coated with machine oil to prepare compression test pieces (70.7x70.7x70.7mm) and flexural test pieces (40x40x160mm), respectively, and after the test pieces are formed, they are numbered and placed in a standard cement curing box (temperature 20℃, humidity 95%) for curing for 7 days.

[0069] The average mesh number of the graphite is 1000 mesh;

[0070] The average mesh number of the floating beads is 300 mesh;

[0071] The modified high-thermal-conductivity powder is first pre-modified with a sodium hydroxide solution (prepared by using deionized water) with a concentration of 3 mol / L, and then modified with a KH-560 silane coupling agent ethanol dispersion liquid with a concentration of 0.04 mol / L, the mass ratio of the high-thermal-conductivity powder to the sodium hydroxide solution being 1:1.3, and the mass ratio of the high-thermal-conductivity powder to the KH-560 silane coupling agent being 1:0.01;

[0072] The modified low-thermal-conductivity powder is modified with a KH-560 silane coupling agent ethanol dispersion liquid with a concentration of 0.04 mol / L, the mass ratio of the low-thermal-conductivity powder to the KH-560 silane coupling agent being 1:0.01;

[0073] The water reducing agent is an early-strength polycarboxylic acid water reducing agent;

[0074] The retarder is prepared by compounding sodium gluconate and borax, the mass ratio of the sodium gluconate to the borax being 1:2.5;

[0075] The early strength agent is a lithium carbonate early strength agent;

[0076] The defoaming agent is Mingling P 803 defoaming agent;

[0077] The expanding agent is calcium sulphoaluminate expanding agent;

[0078] The workability regulator is composed of BASF anti-settling agent and low viscosity hydroxyethyl methyl cellulose ether, wherein the mixing ratio of the BASF anti-settling agent to the hydroxyethyl methyl cellulose ether is 1:1.5;

[0079] The coloring agent is a mixture of titanium dioxide pigment and fixing agent.

[0080] The flexural strength and compressive strength of the above five kinds of test pieces are tested by using a flexural strength tester and a pressure testing machine respectively, three groups of each grouting material are tested in parallel and the average value is taken, and the results are shown in Table 1.

[0081] Table 1 7d flexural strength and 7d compressive strength test results

[0082]

[0083] The existing specification indicates that the 7d flexural strength of the grouting material is not less than 2MPa, and the 7d compressive strength is not less than 15MPa. From Table 1, it can be seen that the 7d flexural strength and 7d compressive strength of the five kinds of grouting materials prepared meet the specification requirements, and compared with the comparative composite cement grouting material, the flexural strength and compressive strength of the high thermal conductivity composite cement grouting material, the low thermal conductivity composite cement grouting material, the reflective high thermal conductivity composite cement grouting material and the reflective low thermal conductivity composite cement grouting material prepared by the application are all large, which indicates that the grouting material prepared by the application has good strength. Embodiment

[0084] In the preparation of the large-void matrix asphalt mixture of the embodiment, the mass of the SBS / rubber composite modified asphalt is 3.5% of the mass of the mixture, and the mass of the flocculent lignin fiber is 0.2% of the mass of the mixture, and the gradation of the aggregate and the mineral powder is shown in Table 2.

[0085] Among them, the asphalt is SBS / rubber composite modified asphalt, SBS accounts for 5.5% of the mass of the asphalt, and the rubber is 40 mesh rubber, and the rubber accounts for 18% of the mass of the asphalt;

[0086] Table 2 Gradation design of large-void matrix asphalt mixture

[0087]

[0088] According to the gradation shown in Table 2, the preparation method is specifically as follows: first, the designed mixture ratio is used to respectively weigh the asphalt, aggregate, mineral powder and fiber, and then the preheating is carried out in an oven; subsequently, the fiber, asphalt and mineral powder are sequentially added to the preheated aggregate, and then the mixing is carried out at 180℃ for 360s; then, the rotary compactor is used for compaction molding under the condition of 170℃, the double-side compaction frequency is 50 times each, the prepared cylindrical specimen has a height of 10cm, a void ratio of 28%, a stability of 5.13kN and a flow value of 2.02mm. Embodiment

[0089] Based on the specific embodiments 1 and 2, the high-thermal-conductivity composite cement grout containing graphite powder is taken as an example to prepare the grouting type composite asphalt mixture, and the preparation process is as shown in Figure 1 .

[0090] The high-thermal-conductivity composite cement grout with different thermal conductivities is prepared by using 3% and 7% of graphite powder; then, the bottom surface and the side surface of the large-void matrix asphalt mixture specimen prepared in embodiment 2 are sealed by using the fresh-keeping film and the adhesive tape, and the top surface is reserved for grouting; subsequently, the high-thermal-conductivity composite cement grout containing 7% of graphite powder is grouted into the cooled large-void matrix asphalt mixture specimen, and the grouting depth is half of the height of the large-void matrix asphalt mixture specimen, i.e. 5cm; after the initial setting of the high-thermal-conductivity composite cement grout containing 7% of graphite powder, the high-thermal-conductivity composite cement grout containing 3% of graphite powder is grouted into the mixture specimen, and the grouting depth is also half of the height of the large-void matrix asphalt mixture specimen, i.e. 5cm; in this process, the excess grouting material on the surface is scraped off by using a brush until the surface structure of the mixture is exposed; finally, the specimen is placed into a standard cement curing box (temperature 20℃, humidity 95%) for curing for 3d, and after the hardening of the two kinds of high-thermal-conductivity composite cement grouts, the grouting type composite asphalt mixture with gradient thermal conductivity structure can be obtained.

[0091] In order to characterize the thermal conductivity and road performance of the grouting type composite asphalt mixture prepared by the present application, the comparative grouting type composite asphalt mixture is also prepared in the present embodiment, and the preparation process is as follows:

[0092] Firstly, the bottom surface and the side surface of the large-void matrix asphalt mixture specimen prepared in embodiment 2 are sealed by using the fresh-keeping film and the adhesive tape, and the top surface is reserved for grouting; then, the comparative composite cement grout prepared in embodiment 1 is grouted into the large-void matrix asphalt mixture specimen, and in this process, the specimen is slightly shaken to assist the flow until it cannot be completely penetrated; subsequently, the excess grouting material on the surface is scraped off by using a brush until the surface structure of the mixture is exposed, and the specimen is placed into a standard cement curing box (temperature 20℃, humidity 95%) for curing for 3d, and the comparative grouting type composite asphalt mixture is obtained.

[0093] The filling rate, heat conduction performance, high temperature stability and water damage resistance of the two prepared filling type composite asphalt mixtures are tested, and the results are as follows:

[0094] The filling rate of the filling type composite asphalt mixture with gradient heat conduction structure is 97.8%, the thermal conductivity is 1.523 W / (m·K), the dynamic stability is 13274 times / mm, the immersion residual stability is 98.7%, and the freeze-thaw splitting strength ratio is 97.5%.

[0095] The filling rate of the comparative filling type composite asphalt mixture is 96.7%, the thermal conductivity is 0.121 W / (m·K), the dynamic stability is 12311 times / mm, the immersion residual stability is 97.6%, and the freeze-thaw splitting strength ratio is 96.6%.

[0096] Therefore, the filling rates of the two filling type composite asphalt mixtures meet the requirement of the related standard that the filling rate is greater than 85%, and compared with the comparative filling type composite asphalt mixture, the filling type composite asphalt mixture with gradient heat conduction structure has better heat conduction performance, high temperature stability and water damage resistance. Embodiment

[0097] In this embodiment, a gradient heat conduction filling type composite asphalt pavement structure is prepared based on the embodiments 1, 2 and 3, and the void ratio of the large void matrix asphalt mixture of each layer of the pavement is 28%; the heat-induced bonding material is SBS / rubber composite modified asphalt and graphite in a molten state at 150℃, which is stirred by a high-speed shear machine (stirring speed is 15000r / min, stirring time is 30min), and the mixing ratio of SBS / rubber composite modified asphalt and graphite is 1:0.15; the high thermal resistance bonding material is SBS / rubber composite modified asphalt and floating beads in a molten state at 150℃, which is stirred by a high-speed shear machine (stirring speed is 15000r / min, stirring time is 30min), and the mixing ratio of SBS / rubber composite modified asphalt and floating beads is 1:0.15.

[0098] The pavement structure provided in the present application is divided into two layers of upper layer and lower layer, and the thickness of each layer is 10cm, and the preparation schematic diagram of the two pavement structures is as shown in Figure 2 and Figure 3 .

[0099] The first is an "upper small lower large" structure established to alleviate urban heat island effect, the upper layer is divided into an upper part and a lower part, the upper part is a reflective low thermal conductivity grouting material (the mixing amount of floating bead powder is 7%), the lower part is a low thermal conductivity grouting material (the mixing amount of floating bead powder is 3%), and the grouting depth of the two grouting materials is 5 cm; the lower layer is also divided into an upper part and a lower part, the upper part is a low-mixing high thermal conductivity grouting material (the mixing amount of graphite powder is 3%), the lower part is a high-mixing high thermal conductivity grouting material (the mixing amount of graphite powder is 7%), and the grouting depth of the two grouting materials is 5 cm; a thermal induction bonding layer (as shown in Figure 2 ) is arranged between the upper layer and the lower layer.

[0100] To prove that the "upper small lower large" pavement structure proposed in the application can effectively alleviate the urban heat island effect, the embodiment first forms the pavement structure as shown in Figure 2 based on the above steps, and places a temperature sensor at each of the surface of the upper layer, the thermal induction bonding layer and the bottom of the lower layer in the pavement structure; then, a 500W iodine tungsten lamp is placed above the pavement structure (the vertical distance from the top of the upper layer is 50 cm), the iodine tungsten lamp is turned on to irradiate for 8 hours, and then the temperature data of the three places are recorded; finally, the iodine tungsten lamp is turned off, and after the temperature of the surface of the upper layer of the pavement structure returns to 25℃, the temperature data of the above three places are recorded again. The related results are shown in Table 3. As can be seen from Table 3, by observing the temperature reading difference before and after the thermal induction bonding layer and the bottom of the lower layer, it can be found that the temperature reduction amplitude of the bottom of the lower layer is smaller than that of the thermal induction bonding layer, which indicates that the "upper small lower large" pavement structure implemented in the application can effectively promote the downward transmission of heat, thereby alleviating the urban heat island effect.

[0101] Table 3 Temperature data statistics of different positions of "upper small lower large" pavement structure

[0102]

[0103] The second is an "upper large lower small" structure established to protect frozen soil, the upper layer is divided into an upper part and a lower part, the upper part is a reflective high thermal conductivity grouting material (the mixing amount of graphite powder is 7%), the lower part is a high thermal conductivity grouting material (the mixing amount of graphite powder is 3%), and the grouting depth of the two grouting materials is 5 cm; the lower layer is also divided into an upper part and a lower part, the upper part is a low-mixing low thermal conductivity grouting material (the mixing amount of floating bead powder is 3%), the lower part is a high-mixing low thermal conductivity grouting material (the mixing amount of floating bead powder is 7%), and the grouting depth of the two grouting materials is 5 cm; a thermal induction bonding layer is arranged between the upper layer and the lower layer, and a high thermal resistance bonding layer (as shown in Figure 3 ) is arranged at the bottom of the lower layer.

[0104] To prove that the "upper large lower small" pavement structure proposed in the application can effectively protect the frozen soil structure, the embodiment first forms the pavement structure as shown in Figure 3The temperature sensors are placed at three positions, i.e., the surface of the upper layer, the heat-induced bonding layer and the high-thermal-resistance bonding layer in the pavement structure. Then, a 500W iodine tungsten lamp is placed above the pavement structure (50cm vertically from the top of the upper layer), and the iodine tungsten lamp is turned on to irradiate for 8 hours, and then the temperature data of the three positions are recorded. Finally, the iodine tungsten lamp is turned off, and after the temperature of the surface of the upper layer of the pavement structure returns to 25℃, the temperature data of the three positions are recorded again. The related results are shown in Table 4.

[0105] Table 4 Temperature data statistics of different positions in the pavement structure of "big on top and small on bottom"

[0106]

[0107] As can be seen from Table 4, by observing the difference between the two temperature readings before and after the heat-induced bonding layer and the high-thermal-resistance bonding layer, it can be found that the temperature reduction of the high-thermal-resistance bonding layer is greater than that of the heat-induced bonding layer, which shows that the pavement structure of "big on top and small on bottom" according to the present application can effectively promote the heat transfer upward, thereby achieving the purpose of protecting the frozen soil structure.

Claims

1. A gradient heat conduction directional regulation type poured composite asphalt pavement surface layer structure, characterized in that, The asphalt pavement surface layer is divided into upper and lower double-layer structures; The upper layer is formed by sequentially pouring low-thermal-conductivity grouting material and reflective low-thermal-conductivity grouting material into the framework; the lower layer is formed by sequentially pouring high-thermal-conductivity grouting material with high content and low-thermal-conductivity grouting material with low content into the framework; and a heat-induced bonding layer is arranged between the upper and lower layers; The framework is made of large-void base asphalt mixture, and the void ratio is controlled to be between 20% and 35%; The high-thermal-conductivity grouting material is prepared by the following process: first, high-thermal-conductivity composite cement, modified high-thermal-conductivity powder, microbeads, quartz sand, a retarder, an early strength agent, a defoaming agent, an expansive agent, and a workability regulator are mixed together and stirred until uniform to obtain a dry mixture; then, a water reducing agent is stirred in water until uniform, and the stirring is continued for 1-3 minutes; finally, the water solution containing the water reducing agent is added to the dry mixture and stirred for another 3-5 minutes to obtain the high-thermal-conductivity grouting material ready for use; The low-thermal-conductivity grouting material is prepared by the following process: first, low-thermal-conductivity composite cement, modified low-thermal-conductivity powder, microbeads, quartz sand, a retarder, an early strength agent, a defoaming agent, an expansive agent, and a workability regulator are mixed together and stirred until uniform to obtain a dry mixture; then, a water reducing agent is stirred in water until uniform, and the stirring is continued for 1-3 minutes; finally, the water solution containing the water reducing agent is added to the dry mixture and stirred for another 3-5 minutes to obtain the low-thermal-conductivity grouting material ready for use; The low-thermal-conductivity grouting material is prepared by the following process: first, low-thermal-conductivity composite cement, modified low-thermal-conductivity powder, microbeads, quartz sand, a retarder, an early strength agent, a defoaming agent, an expansive agent, and a workability regulator are mixed together and stirred until uniform to obtain a dry mixture; then, a water reducing agent is stirred in water until uniform, and the stirring is continued for 1-3 minutes; finally, the water solution containing the water reducing agent is added to the dry mixture and stirred for another 3-5 minutes to obtain the low-thermal-conductivity grouting material ready for use; The high-thermal-conductivity composite cement is composed of ordinary Portland cement and ammonium magnesium phosphate cement with a blending ratio of 1: (1-5); the low-thermal-conductivity composite cement is composed of ordinary Portland cement and sulphoaluminate cement with a blending ratio of 1: (1-5); The modified thermal-conductivity powder and the microbeads are collectively referred to as mineral admixtures; The mass ratio of the modified thermal-conductivity powder to the microbeads is 1: (0.8-2.0); the added amount of the mineral admixtures is 0-20% of the mass of the composite cement; The workability regulator is composed of BASF anti-settling agent and low-viscosity hydroxyethyl methyl cellulose ether, and the blending ratio of the BASF anti-settling agent to the hydroxyethyl methyl cellulose ether is 1: (1-2); The coloring agent is a mixture of titanium dioxide pigment and a color fixing agent.

2. The gradient heat conduction directional regulation and control type poured composite asphalt pavement surface layer structure according to claim 1, characterized in that, The large-void base asphalt mixture is made of asphalt, aggregate, mineral powder, and fiber; The asphalt is SBS / rubber composite modified asphalt, SBS is a linear modifier, SBS accounts for 3%-8% of the mass of the asphalt, rubber is 40-mesh rubber, and rubber accounts for 10%-20% of the mass of the asphalt; the blending amount of the SBS / rubber composite modified asphalt is 2% (mass)-4% (mass) of the asphalt mixture; The aggregate is basalt coarse and fine aggregate, which is divided into four grades of 0-5 mm, 5-10 mm, 10-15 mm, and 15-20 mm; the blending amount of the aggregate is 85% (mass)-92% (mass) of the asphalt mixture; The mineral powder is limestone mineral powder, and the blending amount of the mineral powder is 5% (mass)-20% (mass) of the asphalt mixture; The fibers are fluff-like lignin fibers, and the fiber content is 0.2% (mass) to 0.4% (mass) of the asphalt mixture; The preparation method is specifically as follows: first, the asphalt, aggregate, mineral powder and fibers are respectively weighed according to the designed mixing ratio and preheated in an oven; then, the preheated aggregate is sequentially added with the fibers, asphalt and mineral powder, and mixed at 160°C to 180°C for 360s to 450s; Then, a rotary compactor or a hydraulic track sample forming machine is used to compact and form under the condition of 150°C to 180°C.

3. The gradient heat conduction directional regulation and control type poured composite asphalt pavement surface layer structure according to claim 1, characterized in that, The modified high-thermal-conductivity powder is pre-modified by using a sodium hydroxide solution with a concentration of 2 mol / L to 4 mol / L, and then re-modified by using a KH-560 silane coupling agent ethanol dispersion liquid with a concentration of 0.03 mol / L to 0.05 mol / L, the mass ratio of the high-thermal-conductivity powder to the sodium hydroxide solution being 1: (1.2 to 1.5), and the mass ratio of the high-thermal-conductivity powder to the KH-560 silane coupling agent being 1: (0.008 to 0.012); The modified low-thermal-conductivity powder is modified by using a KH-560 silane coupling agent ethanol dispersion liquid with a concentration of 0.03 mol / L to 0.05 mol / L, the mass ratio of the low-thermal-conductivity powder to the KH-560 silane coupling agent being 1: (0.008 to 0.012); The high-thermal-conductivity powder is graphite or silicon carbide; The low-thermal-conductivity powder is floating bead or hollow glass bead.

4. The gradient heat conduction directional regulation and control type poured composite asphalt pavement surface layer structure according to claim 3, characterized in that, The graphite has a mesh number of 800 to 1200 and a thermal conductivity of 125 to 140 W / (m·K); The silicon carbide has a mesh number of 100 to 300 and a thermal conductivity of 400 to 490 W / (m·K); The floating bead has a mesh number of 200 to 400 and a thermal conductivity of 0.054 to 0.095 W / (m·K); The hollow glass bead has a mesh number of 60 to 100 and a thermal conductivity of 0.03 to 0.045 W / (m·K); The ethanol has a concentration of 95% to 98% and is used as a dispersion solvent of the KH-560 silane coupling agent; The water used is deionized water.

5. The gradient heat conduction directional regulation and control type poured composite asphalt pavement surface layer structure according to claim 1 or 3, characterized in that, The quartz sand is mixed by 30 to 50 mesh, 50 to 100 mesh and 100 to 200 mesh quartz sand at a mass ratio of 1: (0.1 to 0.3): (0.4 to 0.6), and the quartz sand addition mass is 80% to 125% of the mass of the compounded cement.

6. The gradient thermal-conductivity directional regulation type poured composite asphalt pavement surface layer structure according to claim 1, characterized in that, The water addition mass is 30% to 70% of the mass of the compounded cement; The water reducing agent is an early-strength polycarboxylic acid water reducing agent, and the addition amount is 0.1% to 0.2% of the mass of the compounded cement; The retarder is prepared by compounding sodium gluconate and borax, and the addition mass is 0% to 0.06% of the mass of the compounded cement, wherein the mass ratio of the sodium gluconate to the borax is 1: (2 to 5); The early-strength agent is a lithium carbonate early-strength agent, and the addition mass is 0% to 0.1% of the mass of the compounded cement; The defoaming agent is Mingling P 803 defoaming agent; The expansion agent is calcium sulphoaluminate expansion agent, and the addition mass is 3% to 6% of the mass of the compounded cement.

7. The gradient heat conduction directional regulation and control type poured composite asphalt pavement surface layer structure according to claim 1, characterized in that, The heat-induced bonding material is prepared by stirring SBS / rubber composite modified asphalt and graphite in a molten state at 140-160 DEG C using a high-speed shearing machine, wherein the mixing ratio of SBS / rubber composite modified asphalt and graphite is 1:(0.10-0.25), the stirring speed is 1000-2000 r / min, and the stirring time is 20-40 min.

8. The gradient heat conduction directional regulation and control type poured composite asphalt pavement surface layer structure according to claim 7, characterized in that, In the SBS / rubber composite modified asphalt, SBS is a linear modifier, SBS accounts for 3-8% of the mass of the asphalt, and rubber is 40-mesh rubber, rubber accounts for 10-20% of the mass of the asphalt.

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