Road surface positive concrete mix proportion design method

Abstract

The invention discloses a pavement positive concrete mix proportion design method, and relates to the technical field of mix proportion design of hard concrete for roads and airport runways. The method comprises the following steps: setting the volume fraction Vg of coarse aggregate in concrete according to the grain shape of the coarse aggregate; determining the volume sand ratio beta v according to the maximum particle size of the coarse aggregate and the fineness modulus of the fine aggregate, and calculating the volume fraction Vs of the fine aggregate; calculating a water-cement ratio based on the target strength and adapting an additive; calculating the volume fraction Vp = 1-Vg-Vs of the slurry, and determining the mass of the slurry and the use amount of the cementing material in combination with the water-cement ratio and the density of the cementing material; correcting the dosage of each component according to the designed gas content Va; and determining the gradation of the coarse aggregate and the mixing amount of the additive through an adaptation test. By means of the method, the problems of'insufficient and bulking 'and'slurry redundancy' can be fundamentally solved, the volume stability of the concrete is accurately controlled while the using amount of the cementing material is remarkably reduced, and the mechanical performance and the durability of the concrete are improved.

Description

Technical Field

[0001] This invention belongs to the field of highway and airport runway construction engineering, and specifically relates to a mix design method for pavement concrete. Background Technology

[0002] Dry-hard concrete is widely used in the construction of pavements such as roads and airport runways due to its low cementitious material content and high load-bearing capacity. However, its mix design has long faced serious challenges: traditional design methods relying on empirical parameters such as the maximum aggregate size are prone to discrepancies between the actual produced concrete volume and the design, resulting in either "under-volume" or "over-volume." Simultaneously, to meet workability requirements, excessive cementitious material paste is often introduced, causing significant "paste redundancy." These problems directly increase material costs, and the high heat of hydration and shrinkage caused by excess paste increase the risk of concrete cracking, affecting the durability and economy of pavement projects.

[0003] To optimize concrete performance and reduce cement usage, various mix design methods based on volumetric or packing theory have emerged in existing technologies. For example, the amount of paste used is determined by measuring or simulating the aggregate packing void ratio, or aggregate gradation is optimized using a close-packed model to minimize voids. These methods have made some progress in improving the material efficiency of certain concrete systems. However, they involve a large number of experiments and trials, making them inconvenient for engineering applications.

[0004] However, when these methods are applied to the specific scenario of dry-hard concrete pavement, their shortcomings remain prominent. These methods generally cannot reliably solve the recurring problems of "deficit" and "expansion" in the production of this type of concrete, and their volume control precision is insufficient. More importantly, their design logic fails to effectively curb "slurry redundancy," and the prepared concrete still suffers from problems such as excessive cementitious material content and high potential shrinkage risk. Furthermore, the design process is often complex, relying on numerous experiments or adjustments to specific model parameters, thus limiting its engineering applicability. The design range of coarse aggregate volume fraction and volumetric sand ratio (rather than mass-based sand ratio) proposed in this patent has been fully optimized, significantly reducing the scope of trial and error.

[0005] Therefore, given the unique characteristics of dry-hard concrete pavement, the industry urgently needs a new mix design system that breaks away from the traditional "filling optimization" paradigm and can fundamentally overcome the defects of "deficient volume and excessive volume" and "redundant paste". Summary of the Invention

[0006] This application provides a mix design method for pavement positive concrete (aggregate interlocking concrete), which solves the deep-seated technical problems of "deficient volume and excessive volume" and "redundant paste" that cannot be effectively addressed when the prior art is applied to dry-hard concrete for pavement. It achieves precise control of concrete volume stability and improves its mechanical and durability properties while significantly reducing the amount of cementitious materials used.

[0007] This application provides a method for designing the mix proportion of pavement concrete. The method includes the following steps: Step 1, setting the volume fraction of coarse aggregate in concrete based on the maximum particle size and shape of coarse aggregate; Step 2, determining the volume sand ratio based on the maximum particle size of coarse aggregate and the particle size of sand; Step 3, designing the water-cement ratio and admixture dosage based on strength; Step 4, determining the composition of cementitious materials and auxiliary cementitious materials.

[0008] The maximum particle size of the coarse aggregate mentioned in step 1 includes 26.5mm, 31.5mm and 37.5mm. The particle shape of the coarse aggregate includes excellent, medium and ordinary. The Vg value ranges from 0.50 to 0.54. The criteria for judging the particle shape of coarse aggregate are: needle-like and flaky particle content <8%, particle shape is excellent; needle-like and flaky particle content is between 8% and 15%, particle shape is medium; needle-like and flaky particle content >15%, particle shape is ordinary.

[0009] The fineness modulus of the sand mentioned in step 2 is between 0.28 and 0.32, and the volumetric sand ratio ranges from 0.30 to 0.33.

[0010] The water-cement ratio formula mentioned in step 3 is as follows: , , The 28-day flexural strength of the concrete was determined. The standard value for the design flexural tensile strength of concrete; is the coefficient of variation of concrete flexural strength; t is the guarantee rate coefficient; s is the standard deviation of the flexural strength test sample; fs is the measured 28-day flexural strength of cement.

[0011] The method for calculating the dosage of the admixture in step 3 is as follows: 1) The formula for the apparent density of cementitious materials is: , , The apparent density of each cementitious material, , , This refers to the mass ratio of each cementitious material; 2) Slurry density , The density of water; 3) Mass of slurry Mp = Vp Where the volume fraction of the slurry is Vp = 1 - Vs - Vg; 4) The formula for calculating the total amount of cementitious materials Ct is: Ct = Mp / (1 + ... ).

[0012] The cementitious material described in step 4 has a formulation comprising 30%~100wt% cement, 0%~50wt% mineral powder, and 0%~70wt% fly ash.

[0013] The calculation method for the composition of the cementitious material and auxiliary cementitious material mentioned in step 4 is as follows: Water volume W = Sand usage S = Coarse aggregate dosage G= Dosage of each cementitious material = Ct Percentage of each cementitious material by mass The air content in concrete Calculated at 1.2% to 5.5%.

[0014] One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages: Firstly, this paper reveals the limitations and deep-seated defects in the existing understanding of the core structural mechanism of dry-hard concrete pavement. Existing design methods based on close-packed models fundamentally treat concrete as a composite material where "aggregate voids are filled with paste," pursuing the minimum porosity of the aggregate system under ideal conditions. This limits the technical approach to repeated experiments and model optimization of multi-grade aggregate proportions in order to reduce the amount of paste required for filling. However, this application, through systematic engineering practice and reverse analysis, discovers that for dry-hard concrete pavement, the cornerstone of its mechanical properties is not the density of the paste filling, but rather the mechanically interlocking skeleton formed between coarse aggregate particles. Existing methods completely ignore the core role of the "interlocking effect" as the dominant load-bearing mechanism. Its deep-seated flaw lies in the fact that the slurry volume designed based on the "filling logic" is always intended to fill the "theoretical voids," which inevitably leads to the amount of slurry used far exceeding the actual voids required by the "interlocking skeleton," forming an inherent "structural slurry redundancy." At the same time, the dependence on the theoretical porosity makes the design extremely insensitive to the actual stacking state of the aggregates (affected by sand interference and slurry lubrication), which is the root cause of the recurring "deficient volume, increased volume" problem.

[0015] Secondly, a new technological approach based on the "aggregate interlocking effect" as the core design paradigm is proposed. Based on the aforementioned breakthroughs in understanding, this application fundamentally overturns traditional design thinking. It proposes no longer optimizing "void ratio" as the starting point, but instead establishes the construction of a stable "aggregate interlocking skeleton" as the primary design goal and core principle. The new technological approach is: first, actively setting the necessary range of coarse aggregate volume fraction (Vg=0.50-0.54) for forming an effective interlocking skeleton. This range is established through extensive experimental deduction and represents the minimum volume threshold to ensure that coarse aggregates can fully contact and interlock in concrete, forming the main load-bearing structure. The design logic thus shifts from passive "filling optimization" to proactive "skeleton construction and adaptation."

[0016] Thirdly, it overcomes the technical obstacles faced by the new approach and provides key implementation methods. Transforming the qualitative concept of "interlocking effect" into quantifiable and operable engineering design parameters presents significant challenges. How to determine the specific volumetric parameters corresponding to "effective interlocking"? How to quantify the interference effect of sand on the interlocking framework? How to ensure reliable bonding with only a minimal amount of slurry within this framework? This application, through in-depth analysis, reveals that the stability of the interlocking skeleton is primarily controlled by the inherent properties of the coarse aggregate (particle size and shape) and the degree of involvement of fine aggregate. Based on this, a creative proposal is made: Using "maximum coarse aggregate size" and "particle shape quality" as the core criteria for directly determining Vg, the abstract "interlocking capability" is concretized into clear numerical selection rules.

[0017] The "volume sand ratio" βv is introduced to characterize and control the degree of interference of fine aggregates on the stacking of coarse aggregates. Its value is directly related to the particle size of coarse aggregates and the fineness (fineness modulus) of sand, so as to minimize the weakening of the interlocking skeleton while ensuring workability.

[0018] The slurry volume Vp is determined by the closed formula "1-Vg-Vs", reducing it from a "design objective" to a "natural result after the skeleton and sand are determined", thus eliminating the possibility of slurry redundancy from a mechanistic perspective. Since the interlocking skeleton bears the main load, the slurry bonding burden is reduced, allowing a moderate increase of 0.01-0.02 in the water-cement ratio calculated in the standard. This further reduces slurry demand and shrinkage risk.

[0019] Fourth, it provides a complete and concise technical solution. Starting with Vg and βv, this method directly derives the volume fraction of each component through a series of defined calculation steps, ultimately converting it into the actual feed mass. The entire process avoids complex model iterations and extensive trial mixing, achieving a leap from theoretical understanding of the "interlocking effect" to practical engineering technology. The prepared positive concrete exhibits sufficient aggregate interlocking and precise paste dosage, fundamentally overcoming the defects of volume instability and paste excess, achieving a balance between cost reduction, performance improvement, and simplified design. Detailed Implementation

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to limit the invention; the term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0021] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0022] In the following embodiments, the cement is Huaxin PO42.5 ordinary Portland cement; S95 mineral powder is provided by the Xiangyang Key Laboratory of Comprehensive Utilization of Bulk Solid Waste and Green Building Materials; fly ash is produced by Xiangfan Thermal Power Plant; fine aggregate is limestone manufactured sand with a fineness modulus of 2.9 and an apparent density of 2720 kg / m3; coarse aggregate is limestone crushed stone with two continuous gradations of 10-20 mm and 20-25 mm and an apparent density of 2640 kg / m3; and the admixture is polycarboxylate superplasticizer with a water reduction rate of 28%.

[0023] Example 1: Suitable for Class I highway pavement (maximum coarse aggregate size 26.5mm, excellent particle shape) Application scenario: Main road surface of Class I highway, designed bending tensile strength 5.0MPa, requiring frost resistance grade F200.

[0024] Key parameter settings: coarse aggregate with excellent particle shape, Vg=0.52, fine aggregate fineness modulus of 2.9, volumetric sand ratio of 0.32, cementitious material of 70% cement, 20% mineral powder, 10% fly ash, and air content of 4.5%.

[0025] Mix proportion calculation process: Determine the water-cement ratio: ; fc is the 28-day flexural tensile strength (MPa) of the concrete. fr: Standard value of design flexural strength of concrete; cv: Coefficient of variation of flexural strength of concrete. t: Guarantee rate coefficient; s: Standard deviation of the flexural strength test sample (MPa) fs: Measured 28-day flexural strength of cement (MPa) The design flexural strength fr = 5.0 MPa, coefficient of variation cv = 0.15, guarantee rate coefficient t = 0.72, standard deviation s = 0.5 MPa, and the measured flexural strength of cement fs = 8.0 MPa; Calculate fc = 5 / (1 - 1.04 * 0.15) + 0.72 * 0.5 = 6.284 MPa =1.5684 / (6.284 + 1.0097 - 0.3595 * 8) = 0.355 Apparent density of cementitious materials: ; =3100 kg / m³, =2850kg / m3, =2200 kg / m³, calculated as follows =2928.8 kg / m³; Slurry density Solving =1945.62kg / m3; =0.32, solving for the sand volume fraction Vs yields Vs=0.245; The volume fraction of the slurry, Vp, is calculated as 1 - Vg - Vs = 0.235. Mass of slurry Mp = Vp* =0.235*1945.62=457.22kg / m3; The total amount of cementitious material used is Ct = Mp / (1 + W / C) = 457.22 / 1.355 = 337.43 kg / m³; Water consumption W = Ct * W / C = 119.79 kg / m³; Cement usage C = 337.43 * 0.7 = 236.2 kg / m³; The amount of mineral powder used, K, is 337.43 * 0.2 = 67.49 kg / m³. Fly ash dosage F = 337.43 * 0.1 = 33.74 kg / m³; Sand usage S = 0.245 * 2720 = 666.4 kg / m³; Coarse aggregate dosage G = 0.52 * 2640 = 1372 kg / m³; After adjusting for air content, the final material usage per cubic meter of concrete (kg) is as follows: water: 114.4; cement: 225.57; mineral powder: 64.45; fly ash: 32.22; sand: 636.41; coarse aggregate: 1310.26.

[0026] The technical solutions described in the embodiments of this application above have at least the following technical effects or advantages: This embodiment serves as a benchmark case, fully demonstrating the core design process of this invention: "setting Vg → determining Vs → calculating Vp". Its successful implementation first proves the operability and certainty of the volumetric analysis method. The final mix design shows that the total amount of cementitious material is only 337.4 kg / m³. 3 The volume fraction of the slurry, Vp, was strictly limited to 0.235, avoiding slurry redundancy from the design stage. The calculated flexural strength (6.28 MPa) met and exceeded the design requirements, verifying that the expected performance could still be achieved with the set aggregate skeleton (Vg=0.52) even with low binder content, and preliminarily confirming the feasibility of "aggregate interlocking" as the main load-bearing structure.

[0027] Example 2: Suitable for highway pavement (maximum coarse aggregate size 31.5mm, medium particle shape) Application scenario: Highway driving lane, designed bending tensile strength 5.5MPa, salt freeze resistance grade F300.

[0028] Key parameter settings: coarse aggregate has a medium particle size and a maximum particle size of 31.5 mm. Vg = 0.52 is taken. As the maximum particle size of coarse aggregate increases, the sand ratio decreases. The fineness modulus of fine aggregate is 2.9. The volumetric sand ratio is taken as 0.31. The cementing material is 70% cement, 30% mineral powder, and the air content is 5%.

[0029] Mix proportion calculation process: Determine the water-cement ratio: ; fc is the 28-day flexural tensile strength (MPa) of the concrete. fr: Standard value of design flexural strength of concrete; cv: Coefficient of variation of flexural strength of concrete. t: Guarantee rate coefficient; s: Standard deviation of the flexural strength test sample (MPa) fs: Measured 28-day flexural strength of cement (MPa) The design flexural strength fr = 5.5 MPa, coefficient of variation cv = 0.15, guarantee rate coefficient t = 0.72, standard deviation s = 0.4 MPa, and the measured flexural strength of cement fs = 8.2 MPa; Calculate fc = 5.5 / (1 - 1.04 * 0.15) + 0.72 * 0.4 = 6.80 MPa =1.5684 / (6.80 + 1.0097 - 0.3595 * 8.2) = 0.323 Apparent density of cementitious materials: ; =3100 kg / m³, =2850kg / m3, =2200 kg / m³, calculated as follows =3020.51kg / m3; Slurry density Solving =2022.72kg / m3; =0.31, solving for the sand volume fraction Vs yields Vs=0.234; The volume fraction of the slurry, Vp, is calculated as 1 - Vg - Vs = 0.246. Mass of slurry Mp = Vp* =0.246*2022.72=497.59kg / m3; The total amount of cementitious material used is Ct = Mp / (1 + W / C) = 497.59 / 1.323 = 376.11 kg / m3; Water consumption W = Ct * W / C = 121.48 kg / m³; Cement usage C = 376.11 * 0.7 = 263.28 kg / m³; Mineral powder dosage K = 376.11 * 0.3 = 112.83 kg / m³; Sand usage S = 0.234 * 2720 = 636.48 kg / m³; Coarse aggregate dosage G = 0.52 * 2640 = 1372 kg / m³; After adjusting for air content, the final material usage per cubic meter of concrete is as follows (kg): water: 115.41; cement: 250.12; mineral powder: 107.19; sand: 604.66; coarse aggregate: 1303.4.

[0030] The technical solutions described in the embodiments of this application above have at least the following technical effects or advantages: In this embodiment, under the conditions of increasing design strength and using larger particle size aggregates, the particle size variation was adapted by adjusting the volumetric sand ratio (βv decreased from 0.32 to 0.31), while Vg remained constant. The results show that, to meet higher strength requirements, the amount of cementitious material was moderately increased to 376.1 kg / m³. 3However, the slurry volume fraction Vp (0.246) is close to that of Example 1, and there is no situation of blindly increasing the amount of slurry in pursuit of high strength. This proves that the method of the present invention can rationally and controllably respond to different strength and aggregate particle size requirements by fine-tuning parameters such as Vs. Its performance improvement mainly comes from the balance between skeleton optimization and slurry strength contribution, rather than the traditional increase of slurry volume, effectively suppressing the tendency of slurry excess that is prone to occur in high-strength concrete.

[0031] Example 3: Suitable for heavy-duty highway pavement (maximum coarse aggregate size 31.5mm, excellent particle shape) Application scenario: Heavy-duty highway connecting to ports, designed bending tensile strength of 6.0MPa, requiring wear resistance grade III.

[0032] Key parameter settings: Coarse aggregate has excellent particle shape, with a maximum particle size of 31.5mm and Vg=0.54. As the maximum particle size of coarse aggregate increases, the sand ratio decreases. The fineness modulus of fine aggregate is 2.9 and the volumetric sand ratio is 0.30. The cementing material is 50% cement, 50% mineral powder, and the air content is 1.5%.

[0033] Mix proportion calculation process: Determine the water-cement ratio: ; fc is the 28-day flexural tensile strength (MPa) of the concrete. fr: Standard value of design flexural strength of concrete; Cv: Coefficient of variation of flexural strength of concrete. t: Guarantee rate coefficient; s: Standard deviation of the flexural strength test sample (MPa) fs: Measured 28-day flexural strength of cement (MPa) The design flexural strength fr = 6.0 MPa, coefficient of variation cv = 0.12, guarantee rate coefficient t = 0.72, standard deviation s = 0.45 MPa, and the measured flexural strength of cement fs = 8.5 MPa; Calculate fc = 6 / (1 - 1.04 * 0.12) + 0.72 * 0.45 = 7.18 MPa =1.5684 / (7.18 + 1.0097 - 0.3595 * 8.5) = 0.3055 Apparent density of cementitious materials: ; =3100 kg / m³, =2850kg / m3, =2200 kg / m³, calculated as follows =2969.7kg / m3; Slurry density Solving =2031.6 kg / m3; =0.30, solving for the sand volume fraction Vs yields Vs=0.231; The volume fraction of the slurry, Vp, is calculated as 1 - Vg - Vs = 0.229. Mass of slurry Mp = Vp* =0.229*2031.6=465.2kg / m3; The total amount of cementitious material used is Ct = Mp / (1 + W / C) = 465.2 / 1.306 = 356.2 kg / m³; Water consumption W = Ct * W / C = 109.0 kg / m³; Cement usage C = 356.2 * 0.5 = 178.1 kg / m³; The amount of mineral powder used, K, is 356.2 * 0.5 = 178.1 kg / m³. Sand usage S = 0.231 * 2720 = 628.32 kg / m³; Coarse aggregate dosage G = 0.54 * 2640 = 1425.6 kg / m³; After adjusting for air content, the final material usage per cubic meter of concrete (kg) is as follows: water: 107.4; cement: 175.4; mineral powder: 175.4; sand: 618.90; coarse aggregate: 1404.22.

[0034] The technical solutions described in the embodiments of this application above have at least the following technical effects or advantages: This embodiment is an extreme verification of the core concept of "aggregate interlocking effect". By actively setting the highest coarse aggregate volume fraction (Vg=0.54), the densest interlocking skeleton was constructed. The results are highly convincing: among the six embodiments, this example has the highest coarse aggregate content (1425.6 kg / m³). 3 The slurry volume fraction (Vp) was the lowest (0.229), while the total amount of cementitious material was at a medium level (356.2 kg / m³). 3 However, it boasts the highest design strength (7.18 MPa flexural strength). This strongly confirms the core argument of this invention: by prioritizing a high volume fraction of aggregate interlocking skeleton, the dependence on cementitious slurry can be significantly reduced, achieving the ideal state of "high aggregate, low slurry, high strength." In this example, the slurry truly "fills only the remaining voids in the interlocking skeleton and provides bonding," completely eliminating structural redundancy.

[0035] Example 4: Suitable for rural road pavement (maximum coarse aggregate size 26.5mm, general particle shape) Application scenario: Rural main roads, designed bending tensile strength 4.5MPa, no special frost resistance requirements.

[0036] Key parameter settings: coarse aggregate has a general particle shape with a maximum particle size of 26.5mm. Vg=0.50 is taken. As the maximum particle size of coarse aggregate increases, the sand ratio decreases. The fineness modulus of fine aggregate is 2.9. The volumetric sand ratio is taken as 0.32. The cementing material is 100% cement with an air content of 1.2%.

[0037] Mix proportion calculation process: Determine the water-cement ratio: ; fc is the 28-day flexural tensile strength (MPa) of the concrete. fr: Standard value of design flexural strength of concrete; Cv: Coefficient of variation of flexural strength of concrete. t: Guarantee rate coefficient; s: Standard deviation of the flexural strength test sample (MPa) fs: Measured 28-day flexural strength of cement (MPa) The design flexural strength fr = 4.5 MPa, coefficient of variation cv = 0.20, guarantee rate coefficient t = 0.28, standard deviation s = 0.35 MPa, and the measured flexural strength of cement fs = 7.5 MPa. Calculate fc = 4.5 / (1 - 1.04 * 0.2) + 0.28 * 0.35 = 5.78 MPa =1.5684 / (5.78 + 1.0097 - 0.3595 * 7.5) = 0.383 Apparent density of cementitious materials: ; =3100 kg / m³, =2850kg / m3, =2200 kg / m³, calculated as follows =3100 kg / m³; Slurry density Solving =1960.1 kg / m3; =0.30, solving for the sand volume fraction Vs yields Vs=0.235; The volume fraction of the slurry, Vp, is calculated as 1 - Vg - Vs = 0.265. Mass of slurry Mp = Vp* =0.265*1960.1=519.4kg / m3; The total amount of cementitious material used is Ct = Mp / (1 + W / C) = 519.4 / 1.383 = 375.5 kg / m3; Water consumption W = Ct * W / C = 143.8 kg / m³; Cement usage C = 375.5 kg / m³; Sand usage S = 0.235 * 2720 = 639.2 kg / m³; Coarse aggregate dosage G = 0.5 * 2640 = 1320.0 kg / m³; After adjusting for air content, the final material usage per cubic meter of concrete (kg) is as follows: water: 142.1; cement: 371.0; sand: 631.5; coarse aggregate: 1304.2.

[0038] The technical solutions described in the above embodiments of this application have at least the following technical effects or advantages: This embodiment demonstrates the applicability of the method of the present invention in low-strength, low-cost scenarios. Although a high water-cement ratio and a single cementitious material (cement) are used, the design process still strictly follows the principle of volume control. Although its paste volume fraction Vp (0.265) is relatively high due to the low Vg, it is a clearly calculated value that matches the skeleton state, rather than an empirical redundancy. This proves that even for low-grade concrete, the present invention can provide a rational, non-over-designed proportioning method, avoiding the use of unnecessary high amounts of binder under low strength requirements, reflecting the economic advantage of the method's applicability to all grades.

[0039] Example 5: Highly frost-resistant road surfaces in frigid regions Application scenario: Provincial highways in frigid northern regions with frequent freeze-thaw cycles, where chloride-based de-icing agents are used in winter. Design flexural strength: 5.0 MPa, freeze resistance rating F400.

[0040] Key parameter settings: Coarse aggregate has excellent particle shape with a maximum particle size of 26.5mm. Vg=0.51 is taken. As the maximum particle size of coarse aggregate increases, the sand ratio decreases. The fineness modulus of fine aggregate is 2.9. The volumetric sand ratio is taken as 0.33. The cementing material is 65% cement, 35% mineral powder, and the air content is 5.5%.

[0041] Mix proportion calculation process: Determine the water-cement ratio: ; fc is the 28-day flexural tensile strength (MPa) of the concrete. fr: Standard value of design flexural strength of concrete; Cv: Coefficient of variation of flexural strength of concrete. t: Guarantee rate coefficient; s: Standard deviation of the flexural strength test sample (MPa) fs: Measured 28-day flexural strength of cement (MPa) The design flexural strength fr = 5.0 MPa, coefficient of variation cv = 0.12, guarantee rate coefficient t = 0.72, standard deviation s = 0.4 MPa, and the measured flexural strength of cement fs = 9.0 MPa; Calculate fc = 5.0 / (1 - 1.04 * 0.12) + 0.72 * 0.4 = 6.002 MPa =1.5684 / (6.002+1.0097-0.3595*9.0)=0.415; Considering extremely salt-free regions =0.38; Apparent density of cementitious materials: ; =3100 kg / m³, =2850kg / m3, =2200 kg / m³, calculated as follows =3007.7 kg / m³; Slurry density Solving =1936.9 kg / m3; =0.30, solving for the sand volume fraction Vs yields Vs=0.251; The volume fraction of the slurry, Vp, is calculated as 1 - Vg - Vs = 0.239. Mass of slurry Mp = Vp* =0.239*1936.9=463.0kg / m3; The total amount of cementitious material used is Ct = Mp / (1 + W / C) = 463.0 / 1.38 = 335.5 kg / m³; Water consumption W = Ct * W / C = 127.5 kg / m³; Cement usage C = 335.5 * 0.65 = 218.1 kg / m³; The amount of mineral powder used, K, is 335.5 * 0.65 = 117.4 kg / m³. Sand usage S = 0.251 * 2720 = 682.7 kg / m³; Coarse aggregate dosage G = 0.51 * 2640 = 1346.4 kg / m³; After adjusting for air content, the final material usage per cubic meter of concrete is as follows (kg): water: 120.5; cement: 206.1; mineral powder: 110.9; sand: 645.2; coarse aggregate: 1272.3.

[0042] The technical solutions described in the above embodiments of this application have at least the following technical effects or advantages: This embodiment verifies the flexibility and effectiveness of the method of the present invention in meeting specific durability requirements (such as freeze resistance). After determining the basic system based on the volumetric skeleton (Vg=0.51, Vs=0.251), the key parameters of the water-cement ratio are finely adjusted according to durability requirements (from 0.415 to 0.38). This adjustment slightly increases the amount of cementitious material (from a lower value calculated based on 0.415 to 335.5 kg / m³). 3 However, this is a precise optimization based on a solid volumetric framework, aimed at improving the density and erosion resistance of the slurry itself. Importantly, the adjusted slurry volume fraction Vp (0.239) remains low, proving that this method can effectively control the total amount of slurry while meeting stringent durability requirements, avoiding the old path of returning to high slurry usage in pursuit of a single performance.

[0043] Example 6: Economical pavement for low-grade highways Application scenario: Branch roads with low traffic volume within counties, designed bending tensile strength of 4.0MPa, with no frost resistance requirements.

[0044] Key parameter settings: coarse aggregate has a general particle shape with a maximum particle size of 31.5mm. Vg=0.50 is taken. As the maximum particle size of coarse aggregate increases, the sand ratio decreases. The fineness modulus of fine aggregate is 2.9. The volumetric sand ratio is taken as 0.32. The cementing material is 30% cement, 70% fly ash, and the air content is 2%.

[0045] Mix proportion calculation process: Determine the water-cement ratio: ; fc is the 28-day flexural tensile strength (MPa) of the concrete. fr: Standard value of design flexural strength of concrete; Cv: Coefficient of variation of flexural strength of concrete. t: Guarantee rate coefficient; s: Standard deviation of the flexural strength test sample (MPa) fs: Measured 28-day flexural strength of cement (MPa) The design flexural strength fr = 4.0 MPa, coefficient of variation cv = 0.20, guarantee rate coefficient t = 0.28, standard deviation s = 0.35 MPa, and the measured flexural strength of cement fs = 7.5 MPa; Calculate fc = 4.0 / (1 - 1.04 * 0.20) + 0.28 * 0.35 = 5.15 MPa =1.5684 / (5.15+1.0097-0.3595*7.5)=0.453, take the slightly higher value of 0.46; Apparent density of cementitious materials: ; =3100 kg / m³, =2850kg / m3, =2200 kg / m³, calculated as follows =2410.0 kg / m³; Slurry density Solving =1669.0 kg / m3; =0.30, solving for the sand volume fraction Vs yields Vs=0.235; The volume fraction of the slurry, Vp, is calculated as 1 - Vg - Vs = 0.265. Mass of slurry Mp = Vp* =0.265*1669.0=442.3kg / m3; The total amount of cementitious material used is Ct = Mp / (1 + W / C) = 442.3 / 1.46 = 303.0 kg / m3; Water consumption W = Ct * W / C = 139.4 kg / m³; Cement usage C = 303.0 * 0.3 = 90.9 kg / m³; Fly ash dosage F = 303.0 * 0.7 = 212.1 kg / m³; Sand usage S = 0.235 * 2720 = 639.2 kg / m³; Coarse aggregate dosage G = 0.50 * 2640 = 1320.0 kg / m³; After adjusting for air content, the final material usage per cubic meter of concrete (kg) is as follows: water: 136.6; cement: 89.1; fly ash: 207.9; sand: 626.4; coarse aggregate: 1293.6.

[0046] The technical solutions described in the above embodiments of this application have at least the following technical effects or advantages: This embodiment demonstrates the perfect combination of the method of the present invention and the high-proportion utilization of bulk industrial solid waste (fly ash). Under the set aggregate volume skeleton (Vg=0.50, Vs=0.235), even if the cement proportion in the cementitious material is only 30%, the system remains stable. The total amount of cementitious material is reduced to 303.0 kg / m³. 3 Extremely low level, cement usage less than 90 kg / m³ 3 The economic benefits are significant. This proves that the volume-stable framework provided by this invention provides a solid foundation for the application of large-volume low-activity admixtures, reduces the requirements for slurry performance, and makes it possible to configure low-cost, low-carbon cementitious systems, further expanding the energy-saving and environmental protection value of this method.

[0047] Comparison Table of Key Parameters and Effects of Examples The above six embodiments together constitute a comprehensive empirical demonstration of the technical effects of the present invention: Example 1 establishes the operability and basic effectiveness of the design method.

[0048] Examples 2 and 3, through comparison and extreme design, proved that the performance improvement stemmed from skeleton optimization rather than slurry increment. In particular, Example 3 strongly confirmed the core advantage of the "aggregate interlocking effect" with data.

[0049] Examples 4 and 6 demonstrate the broad applicability of this method under different economic and environmental demands, highlighting its value as a universal design logic.

[0050] Example 5 demonstrates that the method possesses the necessary flexibility to meet specific durability requirements without compromising fundamental volume control.

[0051] In all embodiments, the slurry volume fraction Vp was strictly limited to a narrow range of 0.229-0.265, the amount of cementitious material used was significantly lower than conventional empirical values, and the design strength was met in all cases. This systematically demonstrates that the volumetric analysis method provided by this invention can fundamentally solve the problems of "deficient volume and increased volume" (fixed volume fraction) and "slurry redundancy" (accurate Vp calculation and low-level operation) pointed out in the background art, while achieving multiple goals of high performance, low cost, and simplified design.

[0052] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for designing the mix proportion of pavement concrete, the method comprising the following steps: Step 1, setting the volume fraction of coarse aggregate in concrete based on the maximum particle size and shape of coarse aggregate; Step 2, determining the volume sand ratio based on the maximum particle size of coarse aggregate and the particle size of sand; Step 3, designing the water-cement ratio and admixture dosage based on strength; Step 4, determining the composition of cementitious materials and auxiliary cementitious materials.

2. The pavement concrete mix design method as described in claim 1, characterized in that, The maximum particle size of the coarse aggregate mentioned in step 1 includes 26.5mm, 31.5mm and 37.5mm. The particle shape of the coarse aggregate includes excellent, medium and ordinary. The Vg value ranges from 0.50 to 0.

54. The criteria for judging the particle shape of coarse aggregate are: needle-like and flaky particle content <8%, particle shape is excellent; needle-like and flaky particle content is between 8% and 15%, particle shape is medium; needle-like and flaky particle content >15%, particle shape is ordinary.

3. The pavement concrete mix design method as described in claim 1, characterized in that, The fineness modulus of the sand in step 2 is between 0.28 and 0.32, and the volumetric sand ratio ranges from 0.30 to 0.

33.

4. The pavement concrete mix design method as described in claim 1, characterized in that, The water-cement ratio formula mentioned in step 3 is as follows: , , The 28-day flexural strength of the concrete was determined. The standard value for the design flexural tensile strength of concrete; is the coefficient of variation of concrete flexural strength; t is the guarantee rate coefficient; s is the standard deviation of the flexural strength test sample; fs is the measured 28-day flexural strength of cement.

5. The pavement concrete mix design method as described in claim 1, characterized in that, The method for calculating the dosage of the admixture in step 3 is as follows: 1) The formula for the apparent density of cementitious materials is: , , The apparent density of each cementitious material, , , This refers to the mass ratio of each cementitious material; 2) Slurry density , The density of water; 3) Mass of slurry Mp = Vp Where the volume fraction of the slurry is Vp = 1 - Vs - Vg; 4) The formula for calculating the total amount of cementitious materials Ct is: Ct = Mp / (1 + ... ).

6. The pavement concrete mix design method as described in claim 1, characterized in that, The cementitious material described in step 4 has a formulation comprising 30%~100wt% cement, 0%~50wt% mineral powder, and 0%~70wt% fly ash.

7. The pavement concrete mix design method as described in claim 1, characterized in that, The calculation method for the composition of the cementitious material and auxiliary cementitious material mentioned in step 4 is as follows: Water volume W = Sand usage S= Coarse aggregate dosage G= Dosage of each cementitious material = Ct Percentage of each cementitious material by mass The air content in concrete Calculated at 1.2% to 5.5%.

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