Gradient heat conduction directional regulation and control type injection type composite asphalt pavement surface layer structure

Abstract

The invention discloses a gradient heat conduction directional regulation type injection type composite asphalt pavement surface layer structure, and belongs to the field of pavement materials. The invention aims to solve the problems of low heat-conducting property, poor pavement performance and incapability of conveniently realizing directional heat conduction of heat in surface layers of asphalt pavements in different regions in the current pouring type composite asphalt pavement. Composite cement grouting materials with different heat conductivities are prepared, and multi-layer composite cement material grouting is completed in a large-gap matrix asphalt mixture, so that the grouting type composite asphalt mixture with the gradient heat conduction function is prepared and is applied to different layers of a pavement surface layer structure, and the gradient heat conduction performance of the pavement surface layer structure is improved. Directional heat conduction of asphalt pavement heat in different areas is expected to be achieved, and the purposes of relieving the urban heat island effect and protecting the frozen soil structure are achieved.

Description

Technical Field

[0001] The invention belongs to the field of pavement materials, and in particular relates to a gradient heat-conducting directional controllable poured-in composite asphalt pavement surface layer structure. Background Art

[0002] Asphalt pavement is widely used because of its safety, comfort and convenient construction. However, as a typical black pavement, asphalt pavement has a high heat absorption capacity, and the internal heat collection and slow heat dissipation of the pavement structure will aggravate the urban heat island effect, increase energy consumption, and affect the health of residents. In addition, in plateau frozen soil areas, the inefficient heat dissipation characteristics of asphalt pavement will also destroy the frozen soil structure, affect the service life of the asphalt pavement, and cause serious ecological damage and loss of life and property.

[0003] Poured asphalt pavement is a composite pavement structure formed by filling the voids of open-graded asphalt mixture with cement-based grouting materials. It combines the flexibility of asphalt materials and the rigidity of cement-based materials, and has extremely strong load-bearing capacity and service life. Compared with cement concrete pavement or asphalt concrete pavement, poured asphalt pavement has moderate flexibility and rigidity, and has broad application prospects. However, the current poured composite asphalt pavement has problems such as weak thermal conductivity, poor road performance, and the inability to conveniently achieve directional heat conduction inside the asphalt pavement surface layer in different regions. Summary of the invention

[0004] In order to solve the problems of weak thermal conductivity, poor road performance and inconvenient directional heat conduction inside the surface layer of asphalt pavements in different regions in the current poured composite asphalt pavement, the present invention provides a gradient thermal conductive directional controllable poured composite asphalt pavement surface layer structure.

[0005] The present invention provides a gradient heat-conducting directional controllable poured-in composite asphalt pavement surface layer structure. The present invention provides two pavement structures. The first one is a directional thermal induction structure with a small top and a large bottom, which is established to alleviate the urban heat island effect based on the grouting composite gradient thermal conduction method, laying a thermal induction layer between pavement surface layers, and laying a reflective layer grouting material on the top of the upper layer of the pavement; the second one is a directional thermal induction structure with a large top and a small bottom, which is established to protect the frozen soil structure based on the grouting composite gradient thermal conduction method, laying a thermal induction layer between pavement surface layers, laying a reflective layer grouting material on the top of the upper layer of the pavement, and laying a high thermal resistance layer on the bottom of the lower layer of the pavement.

[0006] The asphalt pavement surface layer for mitigating the urban heat island effect is divided into an upper and lower double-layer structure; the upper layer is formed by sequentially pouring low thermal conductivity grouting material and reflective low thermal conductivity grouting material into the skeleton; the lower layer is formed by sequentially pouring high thermal conductivity grouting material with a high dosage and low thermal conductivity grouting material with a low dosage into the skeleton; a heat-induced bonding layer is laid between the upper and lower layers; The asphalt pavement surface layer for protecting frozen soil structure is divided into an upper and lower double-layer structure; the upper layer is formed by sequentially pouring high thermal conductivity grouting material and reflective high thermal conductivity grouting material into the skeleton; the lower layer is formed by sequentially pouring high-dosage low thermal conductivity grouting material and low-dosage low thermal conductivity grouting material into the skeleton; a heat-induced bonding layer is laid between the upper and lower layers; a high thermal resistance bonding layer is laid at the bottom of the lower layer; Specifically, the asphalt pavement surface layer is divided into an upper and lower double-layer structure. For the "small on top and large on bottom" structure, the upper part of the upper layer is reflective low-thermal conductivity grouting material, and the lower part is low-thermal conductivity grouting material. The low-thermal conductivity powder dosage of the two is more on the upper part and less on the lower part, and the injection depth ratio of the two grouting materials is 1:1; the upper part of the lower layer is high-thermal conductivity grouting material with low dosage, and the lower part is high-thermal conductivity grouting material with high dosage, and the injection depth ratio of the two grouting materials is 1:1; a heat-induced bonding layer is laid between the upper and lower layers.

[0007] For the "big on top and small on bottom" structure, the upper part of the upper layer is reflective high thermal conductivity grouting material, and the lower part is high thermal conductivity grouting material. The high thermal conductivity powder dosage of the two is more on the upper part and less on the lower part, and the injection depth ratio of the two grouting materials is 1:1; the upper part of the lower layer is low thermal conductivity grouting material with low dosage, and the lower part is low thermal conductivity grouting material with high dosage, and the injection depth ratio of the two grouting materials is 1:1; a heat-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.

[0008] The skeletons are all made of large-void matrix asphalt mixture, and the void ratio is controlled between 20% and 35%; The high thermal conductivity grouting material is prepared according to the following process: firstly, high thermal conductivity composite cement, modified high thermal conductivity powder, micro beads, quartz sand, retarder, early strength agent, defoamer, expansion agent and workability regulator are dry mixed together and stirred until uniform to obtain a dry mixed mixture; then, the water reducer is placed in water and stirred uniformly for 1min to 3min; finally, the aqueous solution containing the water reducer is added to the dry mixed mixture and stirred for 3min to 5min to obtain the high thermal conductivity grouting material to be used; The low thermal conductivity grouting material is prepared according to the following process: firstly, low thermal conductivity composite cement, modified low thermal conductivity powder, microspheres, quartz sand, retarder, early strength agent, defoamer, expansion agent and workability regulator are dry-mixed together and stirred until uniform to obtain a dry-mixed mixture; then, the water reducer is placed in water and stirred uniformly for 1min to 3min; finally, the aqueous solution containing the water reducer is added to the dry-mixed mixture and stirred for 3min to 5min to obtain the low thermal conductivity grouting material to be used; During the dry mixing process of preparing the high thermal conductivity grouting material or the low thermal conductivity grouting material, a colorant is added and stirred together until uniform to obtain a dry mixed mixture, and after adding the water reducing agent aqueous solution, stirring is continued for 3 minutes to 5 minutes to obtain a reflective high thermal conductivity composite cement grouting material or a reflective low thermal conductivity composite cement grouting material to be used.

[0009] Preparation of composite cement grouting material in the present invention: (1) Materials: The materials required for the preparation of composite cement grouting materials include cement, sand, mineral admixtures, water, and admixtures (water reducer, retarder, early strength agent, defoamer, expansion agent, workability regulator, and colorant). The addition of admixtures can ensure the efficiency of the gradient thermal conductivity of the poured composite asphalt pavement while also ensuring good road performance of the poured composite asphalt pavement.

[0010] Cement includes three types: ordinary Portland cement (42.5MPa), sulphoaluminate cement (42.5MPa) and magnesium ammonium phosphate cement (42.5MPa). In order to improve the performance of composite cement grouting materials and poured composite pavement materials thereof, the present invention uses the above three cements to prepare two composite cements for preparing composite cement grouting materials. The first composite cement is a low thermal conductivity composite cement, which is composed of ordinary Portland cement and sulphoaluminate cement, and the blending ratio of the two is ordinary Portland cement: sulphoaluminate cement = 1: (1-5); the second composite cement is a high thermal conductivity composite cement, which is composed of ordinary Portland cement and magnesium ammonium phosphate cement, and the blending ratio of the two is ordinary Portland cement: magnesium ammonium phosphate cement = 1: (1-5).

[0011] The sand is 30~200 mesh quartz sand, which can be divided into three grades: 30~50 mesh, 50~100 mesh, and 100~200 mesh. The mass ratio of the three grades is 1: (0.1~0.3): (0.4~0.6), and the added mass is 80%~125% of the mass of the composite cement; The mineral admixture includes a thermally conductive powder, a thermally conductive powder modifier and microbeads, wherein the thermally conductive powder includes a high thermally conductive powder and a low thermally conductive powder. The high thermally conductive powder in the present invention can be selected from graphite or silicon carbide, and the low thermally conductive powder can be selected from floating beads or hollow glass microbeads; the mesh number of graphite is between 800 and 1200 meshes, and the thermal conductivity is between 125 and 140 W / (m·K); the mesh number of silicon carbide is between 100 and 300 meshes, and the thermal conductivity is between 400 and 490 W / (m·K); the mesh number of floating beads is between 200 and 400 meshes, and the thermal conductivity is between 0.054 and 0.095 W / (m·K); the mesh number of hollow glass microbeads is between 60 and 100 meshes, and the thermal conductivity is between 0.03 and 0.045 W / (m·K); In order to improve the wettability and dispersibility of the thermally conductive powder in the grouting material and improve the interface bonding degree between the thermally conductive powder and the grouting material, for high thermally conductive powder, the present invention first uses a sodium hydroxide solution with a concentration of 2mol / L~4 mol / L to pre-modify the high thermally conductive powder (the mass ratio of the high thermally conductive powder to the sodium hydroxide solution is 1:1.2~1.5), and then uses a KH-560 silane coupling agent with a concentration of 0.03mol / L~0.05 mol / L to re-modify the pre-modified high thermally conductive powder (the mass ratio of the high thermally conductive powder to the KH-560 silane coupling agent is 1:0.008~0.012). For low thermally conductive powder, the present invention directly uses a silane coupling agent with a concentration of 0.03mol / L~0.05 mol / LKH-560 silane coupling agent is used to modify the low thermal conductivity powder (the mass ratio of low thermal conductivity powder to 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 the dispersion solution of KH-560 silane coupling agent, and the water used is deionized water; in addition, due to its continuous particle size distribution and non-porous characteristics, the microbeads can enhance the interface connection between grouting materials, improve the fluidity of grouting materials, and improve the overall strength of grouting materials. In summary, the added mass of mineral admixtures is 0%~20% of the mass of composite cement, among which the mass ratio of thermal conductive powder to microbeads is 1:(0.8~2); The added mass of water is 30~70% of the mass of the composite cement; The types, functions and corresponding blending ratios of the admixtures involved in the present invention are as follows: The water reducer is an early-strength polycarboxylic acid water reducer, which can increase the fluidity of the grouting material and enhance the early strength of the grouting material. The added mass is 0.1-0.2% of the mass of the composite cement. The retarder is prepared by compounding sodium gluconate and borax, which can prolong the setting time of the grouting material and improve the pouring efficiency. The added mass is 0-0.06% of the mass of the composite cement, wherein the mass ratio of sodium gluconate to borax is 1:2-5; The early strength agent is lithium carbonate, which can enhance the early strength of the grouting material. The added mass is 0-0.1% of the mass of the composite cement. The defoamer is Mingling P 803 defoamer, which can remove the foam in the grouting material, making the internal structure of the grouting material more compact. The added mass is 0.02~0.06% of the mass of the composite cement grouting material; The expansion agent is calcium sulfoaluminate expansion agent, which can improve the shrinkage phenomenon in the grouting material and improve the crack resistance of the grouting material. The added mass is 3-6% of the mass of the composite cement; The workability regulator is composed of BASF anti-settling agent and low-viscosity hydroxyethyl methyl cellulose ether, which can improve the settlement performance of the grouting material and improve the water retention performance of the grouting material. The added mass is 0.03-0.06% of the mass of the composite cement grouting material, wherein the mixing ratio of BASF anti-settling agent to hydroxyethyl methyl cellulose ether is 1:1-2; The colorant 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. The added mass is 1-4% of the mass of the composite cement grouting material.

[0012] (2) Preparation process: According to the above materials, the present invention prepares three types of composite cement grouting materials, including high thermal conductivity composite cement grouting material, low thermal conductivity composite cement grouting material and reflective composite cement grouting material. Each composite grouting material follows the principle of mixing on demand. The reflective composite cement grouting material is prepared by adding a colorant to the high thermal conductivity composite cement grouting material and the low thermal conductivity composite cement grouting material, and is further divided into reflective high thermal conductivity composite cement grouting material and reflective low thermal conductivity composite cement grouting material.

[0013] Preparation of large void matrix asphalt mixture in the present invention (1) Materials: The materials required for the preparation of large-void matrix asphalt mixture include asphalt, aggregate, mineral powder and fiber.

[0014] The asphalt is SBS / rubber composite modified asphalt, which mainly plays a cementing role in the large-void matrix asphalt mixture and can significantly improve the service performance of the large-void matrix asphalt mixture. Among them, SBS is a linear modifier, accounting for 3-8% of the asphalt mass, and the rubber is 40-mesh rubber, accounting for 10-20% of the asphalt mass. The amount of SBS / rubber composite modified asphalt is 2-4% of the asphalt mixture. The aggregate is basalt coarse and fine aggregate, which can be divided into four grades: 0~5mm, 5~10mm, 10~15mm and 15~20mm. It mainly plays the role of skeleton in large-void matrix asphalt mixture. The amount of aggregate is 85~92% of the asphalt mixture. The mineral powder is limestone powder, which can improve the interaction between large-void matrix asphalt mixtures. The amount of mineral powder is 5-20% of the asphalt mixture. The fiber is flocculent lignin fiber, which can improve the adhesion between asphalt and aggregate and asphalt and asphalt. The fiber content is 0.2~0.4% of the asphalt mixture.

[0015] (2) Preparation process: The volume design method is adopted to design the mix ratio of each component material of large-void matrix asphalt mixture. The gradation of asphalt mixture is a continuous open-gradation "skeleton-void structure". The void ratio of the prepared large-void matrix asphalt mixture is 20-35%.

[0016] Specifically, first, asphalt, aggregate, mineral powder and fiber are weighed according to the designed mix ratio and placed in an oven for preheating; then, the preheated aggregate, fiber, asphalt and mineral powder are placed in a mixing pot in turn for mixing, the mixing temperature is 160-180°C, and the mixing time is 360-450s; then, a rotary compactor or a hydraulic rutting specimen forming machine is used to compact and shape the large-void matrix asphalt mixture to obtain a cylindrical specimen or a rutting plate specimen, and the compaction temperature is 150-180°C.

[0017] Preparation of the poured composite asphalt mixture in the present invention (1) Materials: The materials required for the preparation of the poured 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.

[0018] (2) Preparation process: An infused composite asphalt mixture is prepared using a large-void matrix asphalt mixture as a skeleton and composite cement grouting materials with different thermal conductivities as fillers in the skeleton voids. The infused composite asphalt mixture fully utilizes the toughness of the asphalt mixture and the stiffness of the composite cement grouting material. At the same time, based on the different thermal conductivities of the composite cement grouting material, the preparation of an infused composite asphalt mixture with gradient thermal conductivity can be achieved.

[0019] In order to form a gradient thermal conductive structure in a large-void matrix asphalt mixture specimen, the present invention determines grouting materials with different thermal conductivities according to different amounts of thermal conductive powder added therein for the same type of composite cement grouting material, and sequentially pours the grouting materials with different thermal conductivities into the large-void matrix asphalt mixture specimen in layers, and forms grouting material solidified layers with different thermal conductivities in the large-void matrix asphalt mixture.

[0020] Specifically, taking the high thermal conductivity composite cement grouting material containing graphite powder as an example, two high thermal conductivity composite cement grouting materials with different thermal conductivity are prepared by changing the graphite powder dosage (low dosage and high dosage) contained therein; then, the bottom and side surfaces of the large void matrix asphalt mixture specimen prepared in the second step are sealed with plastic wrap and adhesive tape, and the top surface is reserved for slurry injection; subsequently, the high thermal conductivity composite cement grouting material containing a high dosage of graphite powder is injected into the cooled large void matrix asphalt mixture specimen, and the injection depth is 1000 μm. half of the height of the specimen; after the high thermal conductivity composite cement grouting material containing a high amount of graphite powder has initially set, the high thermal conductivity composite cement grouting material containing a low amount of graphite powder is poured into the mixture specimen, and the pouring depth is also half of the height of the large-void matrix asphalt mixture specimen. During this process, use a brush to scrape off excess grouting material on the surface until the surface structure of the mixture is exposed; finally, put the specimen into a standard cement curing box for curing. After the two high thermal conductivity composite cement grouting materials solidify and harden, an infused composite asphalt mixture with a gradient thermal conductivity structure can be obtained.

[0021] Preparation of gradient heat conduction infusion composite asphalt pavement structure in the present invention (1) Materials: The materials required for the preparation of the gradient thermal conductivity poured composite asphalt pavement structure 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, large void matrix asphalt mixture, thermally induced bonding material and high thermal resistance bonding material. Among them, the gradation of the large void matrix asphalt mixture is a continuously open-graded "skeleton-void structure" with a void ratio of 20-35%; the thermally induced bonding material is SBS / rubber composite modified asphalt and graphite in a molten state at 140-160°C, stirred using a high-speed shearing machine (stirring speed is 1000-2000r / min, stirring time is 20-40min), The blending ratio of SBS / rubber composite modified asphalt and graphite is 1:0.10~0.25; the high thermal resistance bonding material is made by stirring SBS / rubber composite modified asphalt and floating beads in a molten state at 140~160°C using a high-speed shearing machine (stirring speed is 1000~2000r / min, stirring time is 20~40min), and the blending ratio of SBS / rubber composite modified asphalt and floating beads is 1:0.10~0.25.

[0022] (2) Preparation process: When the thermal conductivity of different structural layers in the pavement is distributed according to a certain gradient, the heat in the pavement will tend to be conducted in the direction of increasing thermal conductivity. According to the actual needs of directional heat conduction inside the 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 to reduce high temperature and heat accumulation in the pavement, thereby achieving the purpose of alleviating the urban heat island effect and protecting the frozen soil structure.

[0023] to this end, The present invention prepares composite cement grouting materials containing different thermal conductivities and completes the infusion of multiple layers of composite cement materials in a large-void matrix asphalt mixture, thereby preparing an infused composite asphalt mixture with a gradient thermal conductivity function, and applies it to different layers of the pavement surface structure to achieve directional heat conduction of the pavement surface layer, thereby alleviating the urban heat island effect and protecting the frozen soil structure.

[0024] Compared with the prior art, the present invention has the following beneficial effects: The present invention uses composite cement, mineral admixtures and admixtures to improve the performance of composite cement grouting materials, and indirectly improves the service performance of poured composite asphalt pavement; at the same time, with the help of the high flowability of the composite cement grouting material, the modified high and low thermal conductivity powders with different addition amounts are poured into the interior of the large-void matrix asphalt mixture, which can not only improve the thermal conduction effect of the heat in the asphalt pavement, but also improve the service performance of the asphalt pavement.

[0025] In order to alleviate the urban heat island effect and protect the frozen soil structure, the present invention proposes a gradient thermal conductivity directional control type poured composite asphalt pavement surface layer structure. The structure uses composite cement grouting materials with different thermal conductivities prepared by high and low thermal conductivity powders and reflective colorants, which can effectively promote the downward transfer of heat in the asphalt pavement structure or the upward transportation of heat. The structure combines the thermal conductive composite cement grouting material with the reflective composite cement grouting material, thereby better achieving the purpose of alleviating the urban heat island effect and protecting the frozen soil structure.

[0026] In order to further understand the features and technical contents of the present invention, please refer to the following detailed description and drawings of the present invention. However, the attached drawings are only provided for reference and illustration and are not intended to limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is the preparation of poured composite asphalt mixture (taking high thermal conductivity composite cement grouting material containing graphite powder as an example); Figure 2 It is a "small on top and large on the bottom" road structure built to alleviate the urban heat island effect; Figure 3 It is a "big on top and small on bottom" pavement structure built to protect frozen soil. DETAILED DESCRIPTION

[0028] The present invention will be described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, and do not limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0029] Example 1: In this example, different types of composite cement grouting materials are prepared according to the following steps: The preparation process of high thermal conductivity composite cement grouting material is as follows: firstly, high thermal conductivity composite cement prepared by ordinary silicate cement and magnesium ammonium phosphate cement (the mixing ratio of the two is 1:2), modified graphite powder (7% of the mass of composite cement), microspheres (8% of the mass of composite cement), three grades of quartz sand meeting the mixing ratio (100% of the mass of composite cement, the three grades of mixing ratio are 30~50 mesh: 50~100 mesh: 100~200 mesh = 32:5:15), retarder (0.02% of the mass of composite cement), early strength agent (0.03% of the mass of composite cement grouting material), defoamer (0.03% of the mass of composite cement grouting material), expansion agent (3% of the mass of composite cement) and workability regulator (0.0 4%) are put together according to the designed proportion and dry-mixed, and stirred evenly (it takes about 1 to 3 minutes) to obtain a mixed dry-mixed mixture; then, the water reducer (0.15% of the mass of the composite cement) is put into water (60% of the mass of the composite cement) and stirred evenly, and the stirring time takes about 1 to 3 minutes; then, the aqueous solution containing the water reducer is added to the dry-mixed mixture and continued to stir for 5 minutes; finally, the prepared high thermal conductivity composite cement grouting material is poured into the test mold coated with engine oil to prepare compression specimens (70.7×70.7×70.7mm) and flexural specimens (40×40×160mm), respectively. After the specimens are formed, they are numbered and placed in a standard cement curing box (temperature 20°C, humidity 95%) for curing for 7 days.

[0030] The preparation process of low thermal conductivity composite cement grouting material is as follows: firstly, low thermal conductivity composite cement prepared by ordinary silicate cement and sulphoaluminate cement (the mixing ratio of the two is 1:2), modified bleached bead powder (7% of the mass of composite cement), micro beads (8% of the mass of composite cement), three grades of quartz sand meeting the mixing ratio (100% of the mass of composite cement, the three grades of mixing ratio are 30~50 mesh: 50~100 mesh: 100~200 mesh = 32:5:15), retarder (0.02% of the mass of composite cement), early strength agent (0.03% of the mass of composite cement), defoamer (0.03% of the mass of composite cement grouting material), expansion agent (3% of the mass of composite cement) and workability regulator (0.04% of the mass of composite cement grouting material) are added. %) are put together according to the designed ratio and dry-mixed, and stirred evenly (it takes about 1 to 3 minutes) to obtain a uniform dry-mixed mixture; then, the water reducer (0.15% of the mass of the composite cement) is put into water (60% of the mass of the composite cement) and stirred evenly, and the stirring time takes about 1 to 3 minutes; then, the aqueous solution containing the water reducer is added to the dry-mixed mixture and continued to stir for 5 minutes; finally, the prepared low thermal conductivity composite cement grouting material is poured into the test mold coated with engine oil to prepare compression specimens (70.7×70.7×70.7mm) and flexural specimens (40×40×160mm), respectively. After the specimens are formed, they are numbered and placed in a standard cement curing box (temperature 20°C, humidity 95%) for curing for 7 days.

[0031] For the preparation of reflective composite cement grouting material, during the process of preparing the dry-mixed mixture of high thermal conductivity composite cement grouting material or low thermal conductivity composite cement grouting material, a colorant (3% of the mass of the composite cement grouting material) is added to the dry-mixed mixture and stirred together. Subsequently, an aqueous solution containing a water reducer is added to the dry-mixed mixture and continued to be stirred for 5 minutes. Finally, the prepared reflective high thermal conductivity composite cement grouting material or reflective low thermal conductivity composite cement grouting material is poured into a test mold coated with engine oil to prepare compression specimens (70.7×70.7×70.7mm) and flexural specimens (40×40×160mm), respectively. After the specimens are formed, they are numbered and placed in a standard cement curing box (temperature 20°C, humidity 95%) for curing for 7 days.

[0032] The preparation process of the comparative composite cement grouting material is as follows: first, high thermal conductivity composite cement prepared by ordinary Portland cement and magnesium ammonium phosphate cement (the mixing ratio of the two is 1:2), microspheres (15% of the mass of the composite cement), three grades of quartz sand meeting the mix ratio (100% of the mass of the composite cement, the three grades of ratio are 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), defoamer (0.03% of the mass of the composite cement grouting material), expansion agent (3% of the mass of the composite cement) and workability regulator (0.04% of the mass of the composite cement grouting material) are mixed according to the mixing ratio. Put them together according to the designed ratio and dry mix them for 1-3 minutes to obtain a uniform dry mixture; then, put the water reducer (0.15% of the mass of the composite cement) in water (60% of the mass of the composite cement) and stir them evenly for 1-3 minutes; then, add the aqueous solution containing the water reducer to the dry mixture and continue stirring for 3-5 minutes; finally, pour the prepared comparison composite cement grouting material into the test mold coated with engine oil to prepare compression specimens (70.7×70.7×70.7mm) and flexural specimens (40×40×160mm), respectively. After the specimens are formed, they are numbered and placed in a standard cement curing box (temperature 20°C, humidity 95%) for curing for 7 days.

[0033] The average mesh size of graphite used is 1000 mesh; The average mesh size of the floating beads is 300 mesh; The modified high thermal conductivity powder is first pre-modified with a 3 mol / L sodium hydroxide solution (prepared with deionized water), and then modified with a 0.04 mol / L KH-560 silane coupling agent ethanol dispersion. The mass ratio of the high thermal conductivity powder to the sodium hydroxide solution is 1:1.3, and the mass ratio of the high thermal conductivity powder to the KH-560 silane coupling agent is 1:0.01. The modified low thermal conductivity powder is modified by using 0.04 mol / L KH-560 silane coupling agent ethanol dispersion to modify the low thermal conductivity powder, and the mass ratio of the low thermal conductivity powder to the KH-560 silane coupling agent is 1:0.01; The water reducer is an early-strength polycarboxylate water reducer; The retarder is prepared by compounding sodium gluconate and borax, and the mass ratio of sodium gluconate to borax is 1:2.5; The early strength agent is lithium carbonate early strength agent; The defoamer is Mingling P 803 defoamer; The expansion agent is calcium sulphoaluminate expansion agent; The workability regulator is composed of BASF anti-settling agent and low-viscosity hydroxyethyl methyl cellulose ether, wherein the blending ratio of BASF anti-settling agent to hydroxyethyl methyl cellulose ether is 1:1.5; The colorant is a mixture of titanium dioxide pigment and a fixing agent.

[0034] The flexural strength tester and pressure testing machine were used to test the flexural strength and compressive strength of the above five specimens respectively. Three groups of each type of grouting material were tested in parallel and the average value was taken. The results are shown in Table 1 below.

[0035] Table 1 7d flexural strength and 7d compressive strength test results

[0036] Existing specifications point out that the 7d flexural strength of the grouting material is not less than 2MPa, and the 7d compressive strength is not less than 15MPa. As can be seen from Table 1, the 7d flexural strength and 7d compressive strength of the five prepared grouting materials all meet the requirements of the specifications, and compared with the comparative composite cement grouting material, the high thermal conductivity composite cement grouting material, low thermal conductivity composite cement grouting material, reflective high thermal conductivity composite cement grouting material, and reflective low thermal conductivity composite cement grouting material prepared by the present invention have greater flexural strength and compressive strength, indicating that the grouting material prepared by the present invention has better strength. Example

[0037] When preparing the large void matrix asphalt mixture in this embodiment, the mass of SBS / rubber composite modified asphalt is 3.5% of the mass of the mixture, the mass of flocculent lignin fiber is 0.2% of the mass of the mixture, and the gradation of aggregate and mineral powder is shown in Table 2 below.

[0038] The asphalt is SBS / rubber composite modified asphalt, in which SBS accounts for 5.5% of the asphalt mass, and the rubber is 40 mesh rubber, in which rubber accounts for 18% of the asphalt mass; Table 2 Gradation design of large void matrix asphalt mixture

[0039] According to the grading shown in Table 2, the preparation method is specifically as follows: first, asphalt, aggregate, mineral powder and fiber are weighed according to the designed mix ratio and placed in an oven for preheating; then, fiber, asphalt and mineral powder are added to the preheated aggregate in sequence and mixed at 180°C for 360s; then, a rotary compactor is used to compact and shape the mixture at 170°C, with 50 compaction times on both sides. 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. Example

[0040] Based on the specific examples 1 and 2, the present invention takes the high thermal conductivity composite cement grouting material containing graphite powder as an example to prepare the pouring composite asphalt mixture. The preparation process is as follows: Figure 1 shown.

[0041] Two high thermal conductivity composite cement grouting materials with different thermal conductivity were prepared with graphite powder content of 3% and 7%; then, the bottom and side surfaces of the large void matrix asphalt mixture specimen prepared in Example 2 were sealed with plastic wrap and adhesive tape, and the top surface was reserved for slurry injection; subsequently, the high thermal conductivity composite cement grouting material containing 7% graphite powder was injected into the cooled large void matrix asphalt mixture specimen, and the injection depth was half of the height of the large void matrix asphalt mixture specimen, i.e., 5 cm; after the high thermal conductivity composite cement grouting material containing 7% graphite powder was injected into the cooled large void matrix asphalt mixture specimen, the injection depth was half of the height of the large void matrix asphalt mixture specimen, i.e., 5 cm; After the grouting material initially sets, the high thermal conductivity composite cement grouting material containing 3% graphite powder is poured into the mixture specimen. The pouring depth is also half of the height of the large-void matrix asphalt mixture specimen, i.e. 5 cm. During this process, a brush is used to scrape off the excess grouting material on the surface until the surface structure of the mixture is exposed. Finally, the specimen is placed in a standard cement curing box (temperature 20°C, humidity 95%) for curing for 3 days. After the two high thermal conductivity composite cement grouting materials solidify and harden, an infused composite asphalt mixture with a gradient thermal conductivity structure can be obtained.

[0042] In order to characterize the thermal conductivity and road performance of the poured composite asphalt mixture prepared by the present invention, a comparative poured composite asphalt mixture is also prepared in this embodiment, and the preparation process is as follows: First, the bottom and sides of the large-void matrix asphalt mixture specimen prepared in Example 2 were sealed with plastic wrap and adhesive tape, and the top surface was reserved for slurry injection; then, the comparative composite cement grouting material prepared in Example 1 was injected into the large-void matrix asphalt mixture specimen. During this process, the specimen was slightly shaken to assist the flow until it could not be completely penetrated; subsequently, the excess grouting material on the surface was scraped off with a brush until the surface structure of the mixture was exposed, and the specimen was placed in a standard cement curing box (temperature 20°C, humidity 95%) for curing for 3 days to obtain a comparative poured composite asphalt mixture.

[0043] The injection rate, thermal conductivity, high temperature stability and water damage resistance of the two prepared injection-type composite asphalt mixtures were tested, and the results are as follows: The infusion rate of the infused composite asphalt mixture with a gradient thermal conductivity structure is 97.8%, the thermal conductivity is 1.523W / (m·K), the dynamic stability is 13274 times / mm, the water immersion residual stability is 98.7%, and the freeze-thaw splitting strength ratio is 97.5%.

[0044] The injection rate of the comparative injection-type composite asphalt mixture is 96.7%, the thermal conductivity is 0.121 W / (m·K), the dynamic stability is 12311 times / mm, the residual stability after immersion in water is 97.6%, and the freeze-thaw splitting strength ratio is 96.6%.

[0045] It can be seen from this that the injection rates of the two types of poured composite asphalt mixtures meet the requirements of the relevant standards that the injection rate is greater than 85%, and compared with the comparative poured composite asphalt mixture, the poured composite asphalt mixture with a gradient thermal conductive structure has better thermal conductivity, high temperature stability and water damage resistance. Example

[0046] In this embodiment, a gradient heat-conductive infused composite asphalt pavement structure is prepared on the basis of Embodiment 1, Embodiment 2 and Embodiment 3, and the porosity 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°C, stirred using a high-speed shearing machine (stirring speed is 15000r / min, stirring time is 30min), and the blending 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°C, stirred using a high-speed shearing machine (stirring speed is 15000r / min, stirring time is 30min), and the blending ratio of SBS / rubber composite modified asphalt and floating beads is 1:0.15.

[0047] The pavement structure provided by the present invention is divided into two layers, an upper layer and a lower layer, each layer is 10 cm thick, and the schematic diagrams of the preparation of the two pavement structures are as follows: Figure 2 and Figure 3 shown.

[0048] The first type is a "small on top and large on bottom" structure built to alleviate the urban heat island effect. The upper part of the upper layer is reflective low thermal conductivity grouting material (7% floating bead powder content), and the lower part is low thermal conductivity grouting material (3% floating bead powder content). The grouting depth of both grouting materials is 5 cm; the upper part of the lower layer is low-dosage high thermal conductivity grouting material (3% graphite powder content), and the lower part is high-dosage high thermal conductivity grouting material (7% graphite powder content). The grouting depth of both grouting materials is 5 cm; a heat-induced bonding layer (such as Figure 2 as shown).

[0049] In order to prove that the "small top and large bottom" pavement structure proposed by the present invention can effectively alleviate the urban heat island effect, this embodiment first forms a Figure 2The pavement structure shown in the figure is used, and a temperature sensor is placed at three locations in the pavement structure, namely, the surface of the upper layer, the heat-induced bonding layer, and the bottom of the lower layer; then, a 500W iodine tungsten lamp is placed above the pavement structure (50 cm vertically from the top of the upper layer), the iodine tungsten lamp is turned on for 8 hours, and then the temperature data at the three locations are recorded; finally, the iodine tungsten lamp is turned off, and the temperature at the upper layer surface of the pavement structure is restored to 25°C, and then the temperature data at the above three locations are recorded. The relevant results are shown in Table 3. As can be seen from Table 3, by observing the difference between the two temperature readings at the heat-induced bonding layer and the bottom of the lower layer, it can be clearly found that the temperature at the bottom of the lower layer decreases less than that at the heat-induced bonding layer, which indicates that the "small on top and large on the bottom" pavement structure implemented by the present invention can effectively promote heat transfer downward, thereby alleviating the urban heat island effect.

[0050] Table 3 Statistics of temperature data at different positions of the “small at the top and large at the bottom” pavement structure

[0051] The second type is a "big on top, small on bottom" structure built to protect frozen soil. The upper part of the upper layer is a reflective high thermal conductivity grouting material (graphite powder content is 7%), and the lower part is a high thermal conductivity grouting material (graphite powder content is 3%). The grouting depth of both grouting materials is 5 cm; the upper part of the lower layer is a low thermal conductivity grouting material with a low dosage (floating bead powder content is 3%), and the lower part is a high thermal conductivity grouting material with a high dosage (floating bead powder content is 7%). The grouting depth of both grouting materials is 5 cm; a heat-induced bonding layer is laid between the upper and lower layers, and a high thermal resistance bonding layer (such as Figure 3 as shown).

[0052] In order to prove that the "large upper and small lower" pavement structure proposed by the present invention can effectively protect the frozen soil structure, this embodiment first forms a Figure 3 The pavement structure shown in the figure was used, and a temperature sensor was placed at three locations in the pavement structure: the surface of the upper layer, the heat-induced bonding layer, and the high thermal resistance bonding layer; then, a 500W iodine tungsten lamp was placed above the pavement structure (50 cm vertically from the top of the upper layer), and the iodine tungsten lamp was turned on for 8 hours, and then the temperature data of the three locations were recorded; finally, the iodine tungsten lamp was turned off, and the temperature of the above three locations was recorded after the surface temperature of the upper layer of the pavement structure returned to 25°C. The relevant results are shown in Table 4.

[0053] Table 4 Statistics of temperature data at different positions of the “large at the top and small at the bottom” pavement structure

[0054] As can be seen from Table 4, by observing the difference between the temperature readings before and after the heat-induced bonding layer and the high thermal resistance bonding layer, it can be obviously found that compared with the heat-induced bonding layer, the temperature drop at the high thermal resistance bonding layer is greater, which indicates that the "large top and small bottom" pavement structure implemented in the present invention can effectively promote heat transfer upward, thereby achieving the purpose of protecting the frozen soil structure.

Claims

1. A gradient heat-conducting directional controllable poured composite asphalt pavement surface structure, characterized in that: The asphalt pavement surface layer is divided into an upper and lower double-layer structure; The upper layer is formed by pouring low thermal conductivity grouting material and reflective low thermal conductivity grouting material into the frame in sequence; the lower layer is formed by pouring high thermal conductivity grouting material with high dosage and low thermal conductivity grouting material with low dosage into the frame in sequence; a heat-induced bonding layer is laid between the upper and lower layers; Alternatively, the upper layer is formed by sequentially pouring high thermal conductivity grouting material and reflective high thermal conductivity grouting material into the frame; the lower layer is formed by sequentially pouring high-dosage low thermal conductivity grouting material and low-dosage low thermal conductivity grouting material into the frame; a heat-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; The skeletons are all made of large-void matrix asphalt mixture, and the void ratio is controlled between 20% and 35%; The high thermal conductivity grouting material is prepared according to the following process: firstly, high thermal conductivity composite cement, modified high thermal conductivity powder, micro beads, quartz sand, retarder, early strength agent, defoamer, expansion agent and workability regulator are dry mixed together and stirred until uniform to obtain a dry mixed mixture; then, the water reducer is placed in water and stirred uniformly for 1min to 3min; finally, the aqueous solution containing the water reducer is added to the dry mixed mixture and stirred for 3min to 5min to obtain the high thermal conductivity grouting material to be used; The low thermal conductivity grouting material is prepared according to the following process: firstly, low thermal conductivity composite cement, modified low thermal conductivity powder, microspheres, quartz sand, retarder, early strength agent, defoamer, expansion agent and workability regulator are dry-mixed together and stirred until uniform to obtain a dry-mixed mixture; then, the water reducer is placed in water and stirred uniformly for 1min to 3min; finally, the aqueous solution containing the water reducer is added to the dry-mixed mixture and stirred for 3min to 5min to obtain the low thermal conductivity grouting material to be used; During the dry mixing process of preparing the high thermal conductivity grouting material or the low thermal conductivity grouting material, a colorant is added and stirred together until uniform to obtain a dry mixed mixture, and after adding the water reducing agent aqueous solution, stirring is continued for 3 minutes to 5 minutes to obtain a reflective high thermal conductivity composite cement grouting material or a reflective low thermal conductivity composite cement grouting material to be used.

2. According to claim 1, a gradient heat-conducting directional controllable poured composite asphalt pavement surface layer structure is characterized in that: The macrovoid matrix 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% to 8% of the asphalt mass, the rubber is 40 mesh rubber, rubber accounts for 10% to 20% of the asphalt mass, and the amount of SBS / rubber composite modified asphalt is 2% (mass) to 4% (mass) of the asphalt mixture; The aggregate is basalt coarse and fine aggregate, divided into four grades: 0~5mm, 5~10mm, 10~15mm and 15~20mm. The amount of aggregate is 85% (mass) to 92% (mass) of the asphalt mixture. The mineral powder is limestone powder, and the amount of the mineral powder is 5% (mass) to 20% (mass) of the asphalt mixture; The fiber is flocculent lignin fiber, and the fiber content is 0.2% (mass) to 0.4% (mass) of the asphalt mixture; The specific preparation method is as follows: firstly, asphalt, aggregate, mineral powder and fiber are weighed respectively according to the designed mix ratio and placed in an oven for preheating; then, fiber, asphalt and mineral powder are added to the preheated aggregate in sequence and mixed at 160℃~180℃ for 360s~450s; Then, a rotary compactor or a hydraulic rutting specimen forming machine is used to compact and form the specimen at 150°C ~ 180°C.

3. According to claim 1, a gradient heat-conducting directional controllable poured composite asphalt pavement surface layer structure is characterized in that: High thermal conductivity composite cement is composed of ordinary Portland cement and magnesium ammonium phosphate cement in a blending ratio of 1: (1~5); low thermal conductivity composite cement is composed of ordinary Portland cement and sulphoaluminate cement in a blending ratio of 1: (1~5).

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

5. According to claim 4, a gradient heat-conducting directional controllable poured composite asphalt pavement surface layer structure is characterized in that: The mesh number of graphite is between 800 and 1200 mesh, and the thermal conductivity is between 125 and 140 W / (m·K); The mesh size of silicon carbide is between 100 and 300 meshes, and the thermal conductivity is between 400 and 490 W / (m·K); The mesh size of the floating beads is between 200 and 400 mesh, and the thermal conductivity is between 0.054 and 0.095 W / (m·K); The mesh number of hollow glass microspheres is between 60 and 100, and the thermal conductivity is between 0.03 and 0.045 W / (m·K); The ethanol concentration is 95% to 98%, which is used as a dispersing solvent for the KH-560 silane coupling agent; The water used was deionized water.

6. A gradient heat-conducting, directional, controllable, poured-in composite asphalt pavement surface layer structure according to claim 1 or 4, characterized in that: The modified thermally conductive powder and the microspheres are collectively referred to as mineral admixtures; The mass ratio of modified thermal conductive powder to microspheres is 1: (0.8~2.0); the added mass of mineral admixture is 0~20% of the mass of composite cement; The quartz sand is mixed with 30~50 mesh, 50~100 mesh and 100~200 mesh quartz sand in a mass ratio of 1:(0.1~0.3):(0.4~0.6), and the mass of quartz sand added is 80%~125% of the mass of the composite cement.

7. According to claim 1, a gradient heat-conducting directional controllable poured composite asphalt pavement surface layer structure is characterized in that: The added mass of water is 30%~70% of the mass of the composite cement; The water reducer is an early-strength polycarboxylate water reducer, and its addition amount is 0.1%~0.2% of the mass of the composite cement; The retarder is prepared by compounding sodium gluconate and borax, and its added mass is 0%~0.06% of the mass of the composite cement, wherein the mass ratio of sodium gluconate to borax is 1:(2~5); The early strength agent is lithium carbonate early strength agent, and its added mass is 0%~0.1% of the mass of the composite cement; The defoamer is Mingling P 803 defoamer, and its added mass is 0.02%~0.06% of the mass of the composite cement grouting material; The expansion agent is calcium sulphoaluminate expansion agent, and its added mass is 3%~6% 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 its added mass is 0.03%~0.06% of the mass of the composite cement grouting material, wherein the mixing ratio of BASF anti-settling agent to hydroxyethyl methyl cellulose ether is 1:(1~2); The colorant is a mixture of titanium dioxide pigment and color fixing agent, and its added mass is 1%~4% of the mass of the composite cement grouting material.

8. According to claim 1, a gradient heat-conducting directional controllable poured composite asphalt pavement surface layer structure is characterized in that: The thermally induced bonding material is made by stirring SBS / rubber composite modified asphalt and graphite in a molten state at 140°C~160°C using a high-speed shearing machine, and the blending ratio of SBS / rubber composite modified asphalt and graphite is 1:(0.10~0.25); the stirring speed is 1000r / min~2000r / min, and the stirring time is 20min~40min.

9. The gradient heat-conducting directional controllable poured composite asphalt pavement surface layer structure according to claim 1, characterized in that: The high thermal resistance bonding material is made by stirring SBS / rubber composite modified asphalt and floating beads in a molten state at 140°C~160°C using a high-speed shearing machine, and the blending ratio of SBS / rubber composite modified asphalt and floating beads is 1:(0.10~0.25); the stirring speed is 1000r / min~2000r / min, and the stirring time is 20min~40min.

10. A gradient heat-conducting, directional, controllable, poured-in composite asphalt pavement surface layer structure according to claim 8 or 9, characterized in that: In SBS / rubber composite modified asphalt, SBS is a linear modifier, SBS accounts for 3%~8% of the asphalt mass, and the rubber is 40 mesh rubber, rubber accounts for 10%~20% of the asphalt mass.

Images