Design method of low-carbon cement stabilized macadam material

Abstract

The application provides a low-carbon cement stabilized macadam material design method, wherein the glue powder is mixed to reduce the shrinkage of the cement stabilized macadam material, the mixing proportion of the glue powder is controlled through double indexes of key sieve holes and volume parameters, the mixing of the glue powder does not affect the overall gradation and does not expand the overall structure, the performance of the cement stabilized macadam is effectively ensured to be stable, the characteristics of the glue powder are greatly different from those of the stone, the glue powder specific surface area is calculated, the cement mortar film forming theory on the aggregate, tailing sand and glue powder surface is combined, the glue powder cement stabilized macadam mortar dosage calculation method is provided, and it is ensured that there is enough cement mortar for wrapping to obtain better strength. According to the density synthesis of the volume composition state, the application provides a design density determination method, the loading mass of different test materials can be effectively determined, the test precision is improved, and the test amount is reduced. The tailing sand and the glue powder are used as the raw materials of the cement stabilized macadam material, and the waste resource utilization is realized.

Description

Technical Field

[0001] This invention relates to the field of road engineering technology, and in particular to a design method for low-carbon cement-stabilized crushed stone materials. Background Technology

[0002] For a long time, my country's asphalt pavement has adhered to the design philosophy of "strong base and thin surface." Cement-stabilized crushed stone, as the base layer of the pavement, has high early strength, good slab properties, and strong stress diffusion, and has always been synonymous with "strong base." Affected by humidity and temperature, cement-stabilized crushed stone materials are prone to shrinkage, leading to frequent and numerous early cracks in semi-rigid base layers during use. The formation of cracks and the infiltration of water through these cracks severely damage the pavement structure. Under traffic loads, this easily leads to pumping, potholes, pavement settlement, and other secondary diseases, seriously impacting the service life of the pavement.

[0003] Shrinkage cracks in cement-stabilized crushed stone are mainly divided into drying shrinkage cracks and thermal shrinkage cracks. Drying shrinkage cracks are caused by changes in the internal moisture content of the cement-stabilized crushed stone, leading to volume shrinkage of the base layer. Thermal shrinkage cracks are mainly caused by temperature changes leading to internal expansion of the cement-stabilized crushed stone, freezing, and surface tension, resulting in volume and interfacial forces that trigger cracking. Rubber powder particles have good flexibility and strong deformation capacity. When cement-stabilized crushed stone mixtures are subjected to tensile stress, the rubber powder adapts to the strain of the cement stone through elongation deformation, offsetting part of the load, increasing the failure strain of the cement-stabilized crushed stone mixture, and delaying the formation of micro-cracks, thereby improving the flexural tensile strength of the concrete to a certain extent. However, the coordination deformation capacity between rubber powder and cement stone is different, the interfacial bond between rubber and cement is weak, and the increase in rubber content leads to more weak points, and stress concentration accelerates the failure of cement-stabilized crushed stone. Therefore, it is necessary to propose a design method for cement-stabilized crushed stone materials with added adhesive powder. By controlling the amount of adhesive powder added, it is possible to ensure that the structure of cement-stabilized crushed stone will not be stretched and destroyed, and that there is enough cement slurry to coat the crushed stone to form good strength. It is also necessary to ensure that the addition of adhesive powder reduces the shrinkage of cement-stabilized crushed stone while maintaining good strength. Summary of the Invention

[0004] This invention addresses the shrinkage and cracking defects of cement-stabilized crushed stone by providing a design method for cement-stabilized crushed stone with added adhesive powder. By incorporating adhesive powder, the shrinkage of the cement-stabilized crushed stone material is reduced, and a certain amount of tailings sand is added to reuse the adhesive powder and tailings sand, achieving low-carbon and environmentally friendly results. This method controls the proportion of adhesive powder, fine aggregate, and tailings sand by controlling the key sieve aperture, and controls the volume parameters to ensure that the added material does not expand the structure of the cement-stabilized crushed stone, while providing sufficient adhesive slurry to coat the aggregate and form good strength.

[0005] The technical problem to be solved by this invention is achieved by the following technical solution:

[0006] A design method for low-carbon cement-stabilized crushed stone materials includes the following steps:

[0007] (1) Low-carbon cement stabilized crushed stone materials include: cement, adhesive powder, tailings sand, and aggregates. Each grade of aggregates and tailings sand is screened to determine the gradation composition of each grade of aggregates and tailings sand.

[0008] (2) The cement stabilized crushed stone material is graded and then tailings sand and adhesive powder are added. Based on the 0.6mm and 0.075mm sieve passing rates of the gradation design results, the mixing ratio of tailings sand, fine aggregate with a particle size of 0-3mm and adhesive powder is controlled.

[0009] (3) Aggregates with a particle size of 2.36 mm or more are mixed according to the gradation design results of cement stabilized crushed stone materials. The theoretical density is calculated according to the mixing ratio. The mixture is then formed by vibration compaction. The forming density of the composite gradation of aggregates with a particle size of 2.36 mm or more is measured. Based on this, the remaining porosity is calculated.

[0010] (4) Tailings sand, fine aggregate with a particle size of 0-3mm and adhesive powder are filled into the remaining pores after the aggregate with a particle size of 2.36mm or larger is formed. After filling, the porosity is designed for cement-stabilized crushed stone, and the volume structure of the aggregate with a particle size of 2.36mm or larger is not expanded. The mixing ratio of tailings sand, fine aggregate with a particle size of 0-3mm and adhesive powder is controlled by the change in porosity before and after filling.

[0011] (5) Cement and water form a cement mortar film of a certain thickness to coat the aggregate, tailings sand and adhesive powder, and fill part of the pores. The amount of mortar used is calculated by the thickness of the mortar coating film and the specific surface area of ​​the aggregate, tailings sand and adhesive powder.

[0012] (6) Calculate the design density of cement-stabilized crushed stone material according to the combined density of adhesive powder, tailings sand, aggregate and adhesive slurry, and take into account the final porosity value. Determine the material mass when molding the compressive and flexural strength test specimens based on the volume of the test mold.

[0013] Further technology of the present invention:

[0014] Preferably, using 0.6mm and 0.075mm as the key sieve openings, the blending ratio of tailings sand, fine aggregate with a particle size of 0-3mm, and binder powder is controlled according to the following formula:

[0015] P 0～3 ×d x0.075 +P w ×d w0.075 =S 0.075 ×100

[0016] P 0～3 ×d x0.6 +P w ×d w0.6 +P j ×100=S0.6 ×100

[0017] In the formula: P w —Tailings sand blending ratio, %; P 0～3 —Particle size 0–3 mm, %; P j —Adhesive powder ratio, %; d w0.075 —Tailings sand throughput of 0.075mm, %;

[0018] d w0.6 —Tailings sand 0.6mm throughput, %; d x0.6 —Pass yield of 0.6mm material with a 0-3mm tolerance, %;

[0019] d x0.075 —Pass yield of 0.075mm material with a 0-3mm guideline, %; S 0.6 —Design gradation 0.6mm pass rate, %;

[0020] S 0.075 —Design gradation pass rate of 0.075mm, %.

[0021] Preferably, the residual porosity of the aggregate gradation with a particle size of 2.36 mm or larger is calculated according to the following formula:

[0022]

[0023] Where: VCA—residual porosity after the aggregate with a particle size of 2.36mm or larger is synthesized and sized, %;

[0024] ρ 2.36以上 —Synthetic graded molding density, g / cm³ 3 ;ρ g —Theoretical maximum density of the synthetic gradation, g / cm³ 3 .

[0025] Preferably, tailings sand, fine aggregate with a particle size of 0-3mm, and adhesive powder are all filled into the remaining pores after the aggregate with a particle size of 2.36mm or larger is formed, and their blending ratio is controlled according to the following formula:

[0026] P 0～3 +P w +P 2.36以上 +P j =100

[0027]

[0028] Where: VV—design porosity of cement-stabilized crushed stone; ρ0~3—density of aggregate with particle size 0~3, g / cm³ 3 ;ρ j — Density of adhesive powder, g / cm³ 3 ;ρw —Density of tailings sand, g / cm³ 3 ;ρ 胶浆 — Density of adhesive paste, g / cm³ 3 .

[0029] Preferably, the amount of adhesive used is calculated according to the following formula, based on the thickness of the adhesive coating film and the specific surface area of ​​the aggregate, tailings sand, and adhesive powder:

[0030]

[0031] S=0.41+0.0041a+0.0082b+0.0164c+0.0287d+0.0614e

[0032] +0.1229f+0.3277g

[0033] In the formula: S 2.36以上 —Specific area of ​​aggregates with a particle size of 2.36mm or larger, in m² 2 / kg; S 0～3 —Specific area of ​​aggregates with a particle size of 0-3mm, m² 2 /

[0034] kg; S j —Specific area of ​​the adhesive powder, m 2 / kg; S w —Comparative area of ​​tailings, m 2 / kg; d j —Particle size converted from the mesh count of the adhesive powder, in mm;

[0035] S—Comparison area, m 2 / kg; μ—thickness of cement mortar film, μm;

[0036] a, b, c, d, e, f, and g represent the passing rates of sieve openings of 4.75 mm and below.

[0037] The preferred design density of cement-stabilized crushed stone material is calculated according to the following formula:

[0038]

[0039] Preferably, the adhesive powder in the cement-stabilized crushed stone material has a mesh size of 30-50, and the tailings sand is iron tailings sand with a maximum particle size of less than 4.75 mm.

[0040] Preferably, the designed porosity of the cement-stabilized crushed stone material is 2-4%, and the thickness of the cement mortar film is 16-20 μm.

[0041] The beneficial effects of this invention are:

[0042] This invention proposes a dual control method for the proportion of adhesive powder incorporation through key sieve aperture and volume parameters. The incorporation of adhesive powder will not affect the overall gradation of cement-stabilized crushed stone mixture, nor will it disrupt the overall structure, thus effectively ensuring the stable performance of cement-stabilized crushed stone.

[0043] This invention provides a design method for cement-stabilized crushed stone material with added adhesive powder. The properties of the adhesive powder itself are quite different from those of the stone, and its addition will affect the state of the adhesive slurry coating the stone. By correcting the specific surface area of ​​the adhesive powder and combining it with the theory of film formation of cement slurry on the surface of aggregates, tailings sand and adhesive powder, the amount of cement slurry to be added to stabilize the crushed stone is calculated to ensure that there is enough cement slurry to coat the stone, thereby obtaining better strength.

[0044] This invention synthesizes density based on volume composition, providing a method for determining the design density of cement-stabilized crushed stone materials with added adhesive powder. It can effectively determine the molding quality of the material according to different test mold volumes, reduce blind spots and errors in the test process, and greatly reduce the amount of testing.

[0045] This invention uses tailings sand and adhesive powder as raw materials for cement-stabilized crushed stone materials, regenerating industrial waste for reuse, realizing the resource utilization of waste, saving resources, and being highly efficient and environmentally friendly. Detailed Implementation

[0046] To make the technical means, creative features, objectives, and effects of this invention easier to understand, the invention is further described below with reference to specific embodiments. However, the following embodiments are merely preferred embodiments of this invention and not all of them. Other embodiments obtained by those skilled in the art based on the embodiments described herein without creative effort are all within the protection scope of this invention.

[0047] A method for producing asphalt sand with added adhesive powder includes screening tailings sand, 0-3mm fine aggregate, and 3-5mm coarse aggregate, with the results shown below:

[0048] Table 1 Raw material screening results

[0049]

[0050] Table 2 Raw material density

[0051]

[0052] Aggregate gradation was carried out according to the specified gradation range. The blending ratio of each aggregate grade was determined as follows, based on the gradation range specified in the specification:

[0053] Table 3. Gradation Design Results of Cement Stabilized Crushed Stone

[0054]

[0055]

[0056] Based on the gradation design results, aggregates with a particle size of 2.36mm were graded into 20-27mm, 10-20mm, 5-10mm, and 3-5mm sizes, and the theoretical maximum density was calculated as follows:

[0057]

[0058] Materials were prepared according to the following proportions: 33% for 20–27 mm, 12% for 10–20 mm, 20% for 5–10 mm, and 19% for 3–5 mm. The compacted density ρ was measured using a rotary compaction method. 2.36以上 =1.92g / cm 3 The porosity VCA after compaction is 30.8.

[0059] Based on the gradation design results, the passing rates for 0.075mm and 0.6mm particles are 9.9% and 3.4%, respectively. Using 40-mesh rubber powder with a particle size of 0.425mm, the blending ratio is calculated using the following formula:

[0060] P 0～3 ×17.8+P w ×38.1=3.4×100

[0061] P 0～3 ×52.8+P w ×73.2+100×P j =9.9 × 100

[0062] The design porosity is 3%, and the cement mortar density is 1.6 kg / m³. 3 By analyzing the change in porosity before and after filling, the mixing ratio of tailings sand, fine aggregate with a particle size of 0-3mm and adhesive powder is calculated according to the following formula.

[0063] P 0～3 +P w +P 2.36以上 +P j =100

[0064]

[0065] The thickness of the cement mortar film is taken as 18µm. The specific surface area of ​​fine aggregate (0-3mm), coarse aggregate (2.36mm and above), and tailings sand is calculated according to the following formula:

[0066] S=0.41+0.0041a+0.0082b+0.0164c+0.0287d+0.0614e

[0067] +0.1229f+0.3277g

[0068] The calculated specific surface areas of fine aggregate (0–3 mm), coarse aggregate (greater than 2.36 mm), and tailings sand are 14.4 m². 2 / kg, 0.7m 2 / kg, 27.5m 2 / kg. Specific surface area of ​​the adhesive powder.

[0069]

[0070] The above formulas can be combined into a system of equations as shown below:

[0071] P 0～3 ×17.8+P w ×38.1=3.4×100

[0072] P 0～3 ×52.8+P w ×73.2+100×P j =9.9 × 100

[0073] P 0～3 +P w +P 2.36以上 +P j =100

[0074]

[0075]

[0076] The proportions of each raw material were determined as follows: coarse aggregate larger than 2.36mm accounted for 85.2%, aggregate between 0 and 3mm accounted for 7.3%, tailings sand accounted for 5.5%, adhesive powder accounted for 2%, and cement mortar accounted for 9.84%.

[0077] In the gradation design process, the proportions of particles with a diameter greater than 2.36mm (20-27mm, 10-20mm, 5-10mm, 3-5mm) were 33%, 12%, 20%, and 19%, respectively. After normalization, these proportions were 39.3%, 14.3%, 23.8%, and 22.6%. Particles with a diameter greater than 2.36mm accounted for 85.2% of cement-stabilized crushed stone mixed with binder powder. Calculations showed that the proportions of 20-27mm, 10-20mm, 5-10mm, and 3-5mm particles in cement-stabilized crushed stone mixed with binder powder were 33.5%, 12.2%, 20.3%, and 19.2%, respectively. Based on the proportions of raw materials, the design for cement-stabilized crushed stone mixed with binder powder yielded the following results: cement mortar accounted for 9.84%.

[0078]

[0079] Based on the combined density of adhesive powder, tailings sand, aggregate and adhesive slurry, and considering the final porosity value, calculate the design density of cement-stabilized crushed stone material according to the following formula, and determine the material mass when molding the compressive and flexural strength test specimens according to the test mold volume.

[0080]

[0081] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method of designing a low carbon cement stabilized aggregate material, characterized by: The method comprises the following steps: (1) The low-carbon cement stabilized macadam material comprises cement, rubber powder, tailing sand, and aggregate, and each aggregate and tailing sand is sieved to determine the gradation composition of each aggregate and tailing sand; (2) The cement stabilized macadam material is graded and designed, and then the tailing sand and rubber powder are added, and the mixing ratio of the tailing sand, fine aggregate with a particle size of 0-3 mm, and rubber powder is controlled according to the 0.6 mm and 0.075 mm sieve hole passing rates of the gradation design results according to the following formula: P 0～3 ×d x0.075 +P w ×d w0.075 = S 0.075 × 100 P 0～3 ×d x0.6 +P w ×d w0.6 +P j ×100 = S 0.6 ×100 wherein: P w — Tailings incorporation ratio, %; P 0～3 — Incorporation ratio of particle size 0-3 mm, %; P j — % of cement powder incorporation; d w0.075 — % of tailings sand 0.075 mm passing rate; d w0.6 - Tailings sand 0.6 mm pass rate, %;d x0.6 - 0-3 mm fraction 0.6 mm pass rate, %; d x0.075 - 0-3 mm fraction 0.075 mm pass rate, %; S 0.6 - design grading 0.6 mm pass rate, %; S 0.075 - Designation Sieve 0.075 mm Pass, %; (3) The aggregate with a particle size of more than 2.36 mm is mixed according to the gradation design results of the cement stabilized macadam material, the theoretical density is calculated according to the mixing ratio, and the molding density of the aggregate with a particle size of more than 2.36 mm is determined by using the vibration compaction method, and then the residual porosity is calculated according to the following formula: In the formula, VCA is the residual porosity of the aggregate with a particle size of more than 2.36 mm after molding, and the mixing ratio of the tailing sand, fine aggregate with a particle size of 0-3 mm, and rubber powder is controlled according to the following formula: ρ 2.36以上 — Synthetic graded shaped density, g / cm 3 ; ρ g — Synthetic graded theoretical maximum density, g / cm 3 ; The tailing sand, fine aggregate with a particle size of 0-3 mm, and rubber powder are filled in the residual pores of the aggregate with a particle size of more than 2.36 mm after molding, and the mixing ratio is controlled according to the following formula: P 0～3 +P w +P 2.36以上 +P j =100 In the formula: VV - design void ratio of cement stabilized macadam; p 0～3 - density of 0-3 aggregate, g / cm 3 ; p j - density of rubber powder, g / cm 3 ; p w - density of tailings sand, g / cm 3 ; p 胶浆 - density of cement mortar, g / cm 3 ; The design porosity of the cement stabilized macadam after filling is not expanded by the volume structure of the aggregate with a particle size of more than 2.36 mm after molding, and the mixing ratio of the tailing sand, fine aggregate with a particle size of 0-3 mm, and rubber powder is controlled by the change of the porosity before and after filling; (5) The cement and water form a certain thickness of cement paste film to wrap the aggregate, tailing sand, and rubber powder, and fill a part of the pores, and the amount of the cement paste is calculated according to the film thickness and the specific surface area of the aggregate, tailing sand, and rubber powder according to the following formula: S = 0.41 + 0.0041a + 0.0082b + 0.0164c + 0.0287d + 0.0614e + 0.1229f + 0.3277g In the formula, a, b, c, d, e, f, and g are the passing rates of each sieve hole of 4.75 mm and below; S 2.36以上 — Particle size 2.36 mm or more aggregate comparative area, m 2 / kg; S 0～3 — Particle size 0-3 mm aggregate comparative area, m 2 / kg; S j — the powder comparison area, m 2 / kg; S w — tailings comparative area, m 2 / kg; d j —Particle size converted to mesh, mm; S - area, m 2 kg; μ - cement paste film thickness, μm; (6) The design density of the cement stabilized macadam material is calculated according to the following formula according to the combined density of the rubber powder, tailing sand, and aggregate and considering the final porosity value: The design density of the cement stabilized macadam material is calculated according to the following formula: The loading quality of the compression and flexural strength test piece is determined according to the test volume. The rubber powder in the cement stabilized macadam material has a mesh number of 30-50 mesh, and the tailing sand is iron tailing sand with a maximum particle size of less than 4.75 mm.

2. A method of designing a low carbon cement stabilized aggregate material according to claim 1, characterized in that: The design porosity of the cement stabilized macadam material is 2-4%, and the thickness of the cement paste film is 16-20 μm.

3. A method of designing a low carbon cement stabilized aggregate material as claimed in claim 1, wherein: ​

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