Preparation and half-dosage continuous weak vibration construction method of high-strength low-shrinkage steel slag base mixture

Abstract

The invention discloses preparation of a high-strength low-shrinkage steel slag base mixture and a half-dosage continuous weak vibration construction method. The mixture comprises the following base raw materials in volume ratio: 40%-75% of natural aggregate, 25%-60% of steel slag aggregate, 3.0%-5.0% of cement, and 5.0%-15.0% of fly ash. Wherein the maximum dry density of the mixture is 2.35-2.55 g / cm < 3 >, and the optimal water content is 4.0-6.0%; the 7d unconfined compressive strength of the mixture is greater than or equal to 4.0 MPa; the drying shrinkage coefficient is less than or equal to 120 mu epsilon; during preparation, a grading optimization mechanism for inhibiting the steel slag expansion risk through a physical means is provided; during construction, a continuous weak vibration technology is innovatively adopted to replace traditional strong vibration, high-density steel slag and conventional broken stone synchronously sink at a constant speed in the compaction process, vertical segregation caused by density difference is thoroughly eliminated, structural homogeneity is remarkably improved, and the service life is remarkably prolonged.

Description

Technical Field

[0001] This invention belongs to the field of road engineering technology, and more specifically, relates to a method for preparing high-strength, low-shrinkage steel slag base course mixture and a semi-admixture continuous weak vibration construction method. Background Technology

[0002] my country's steel industry produces over 100 million tons of steel slag annually, but its comprehensive utilization rate has long been low, and its large-scale stockpiling severely encroaches on land resources. Meanwhile, with the accelerated development of a strong transportation network, the demand for high-quality aggregates from high-grade highway construction continues to surge. However, due to their non-renewable nature, natural sand and gravel resources are facing depletion and supply shortages, making it difficult to meet the industry's sustainable development needs.

[0003] Steel slag, a typical bulk industrial solid waste, possesses excellent physical and mechanical properties such as high strength, good wear resistance, and sharp edges. Theoretically, it is an ideal candidate material to replace natural aggregates with high-quality manufactured sand and gravel. Its large-scale application in highway base materials can "turn waste into treasure," providing a dual solution to alleviate aggregate resource shortages and dispose of solid waste, resulting in significant environmental and economic benefits.

[0004] However, the application of steel slag in road base courses faces two major technical barriers:

[0005] (1) Poor volume stability restricts the increase of steel slag content: The free calcium oxide (f-CaO) and free magnesium oxide (f-MgO) remaining in steel slag undergo delayed volume expansion under long-term hydration conditions. When the steel slag content is too high, the accumulated expansion stress in the base layer can easily lead to cracking, warping and other defects in the structural layer, seriously threatening the service life and structural safety of the road. However, if the steel slag content is excessively reduced in order to control risks, it will be difficult to achieve the core goal of large-scale solid waste disposal. How to significantly increase the steel slag content while ensuring volume stability is the primary challenge.

[0006] (2) Construction segregation induced by aggregate density difference: The density of steel slag is significantly higher than that of traditional aggregates, with a density difference exceeding 30%. When the current typical paving and compaction process of "static pressure + weak vibration + strong vibration + static pressure" is adopted, the huge energy input in the strong vibration stage will drastically amplify the density difference effect, causing steel slag particles to sink rapidly and crushed stone aggregates to float relatively, forming significant vertical density stratification segregation. This segregation not only causes significant unevenness in compaction degree in the layer thickness direction, but also leads to increased dispersion in the final base course strength distribution, making it difficult for the overall performance of the base course to meet the stringent requirements of high-grade highways for structural homogeneity and load-bearing stability.

[0007] Therefore, developing a novel steel slag-based base material preparation technology that can overcome dosage limitations and possess high strength and excellent volume stability, and simultaneously innovating a compaction process that can effectively avoid segregation defects caused by density differences, are the core issues that urgently need to be addressed to promote the large-scale and high-value application of steel slag in highway base courses. Summary of the Invention

[0008] To address the aforementioned deficiencies or improvement needs of existing technologies, this invention provides a method for preparing high-strength, low-shrinkage steel slag base course mixtures and a semi-admixture continuous weak vibration construction method. In the mix design process, the use of semi-admixture steel slag, gradation optimization technology, and steel slag-fly ash chemical interaction control technology effectively alleviates base course cracking caused by steel slag hydration expansion, reducing the risk of crack development. During construction, a compaction process combining static pressure, continuous weak vibration, kneading, and static pressure is employed, avoiding problems such as insufficient compaction and mixture segregation associated with traditional compaction processes. This ensures uniform and dense formation of the mixture, improves road performance, and extends road service life, providing an economical, environmentally friendly, and efficient solution for highway construction. Through a three-in-one innovation of "materials-structure-process," with semi-admixture steel slag (25%–60%) as the core and continuous weak vibration technology as the breakthrough point, this invention not only overcomes the construction challenges of steel slag base course applications but also achieves significant progress in "improved solid waste disposal capacity, extended pavement life, and reduced carbon emissions," marking a milestone in promoting the green transformation of transportation infrastructure.

[0009] To achieve the above objectives, one aspect of the present invention provides a high-strength, low-shrinkage steel slag base course mixture, comprising the following base course raw materials in the following volume ratios: 40%–75% natural aggregate, 25%–60% steel slag aggregate, 3.0%–5.0% cement admixture, and 5.0%–15.0% fly ash admixture; wherein,

[0010] The natural aggregates include crushed stone or gravel;

[0011] The maximum dry density of the high-strength, low-shrinkage steel slag base course mixture is 2.35–2.55 g / cm³. 3 The optimal moisture content is 4.0–6.0%.

[0012] The 7-day unconfined compressive strength of the steel slag base mixture is ≥4.0MPa; the drying shrinkage coefficient is ≤120με.

[0013] Furthermore, the steel slag aggregate is divided into three particle size grades: 10-20mm, 5-10mm, and 0-5mm.

[0014] Furthermore, the water immersion expansion rate of the steel slag aggregate is ≤1.0%, the free calcium oxide content is ≤2.0%, the autoclaving pulverization rate is ≤3.0%, and the metallic iron content is <2.0%.

[0015] Furthermore, the cement is ordinary Portland cement with an initial setting time > 4h and a final setting time > 6h.

[0016] Furthermore, the fly ash used is raw fly ash or Grade I fly ash;

[0017] When the fly ash used is raw fly ash, the amount of raw fly ash is limited to 15% to 20% of the mass of steel slag aggregate, and the total amount of fly ash is ≥ 5% of the total mass of the mixture.

[0018] When the fly ash used is Grade I fly ash, the amount of Grade I fly ash is limited to 10% to 15% of the mass of steel slag aggregate, and the total amount of fly ash is ≥ 5% of the total mass of the mixture.

[0019] A second aspect of the present invention provides a method for preparing a high-strength, low-shrinkage steel slag base course mixture, comprising the following steps:

[0020] S1: Weigh out natural aggregate, steel slag aggregate, cement, and fly ash by volume ratios of 40%–75%, 25%–60%, 3.0%–5.0%, and 5.0%–10.0%, respectively; classify the steel slag aggregate by particle size to determine the mass ratio of coarse and fine aggregates in the steel slag aggregate; and determine the elastic modulus of natural aggregate and steel slag aggregate.

[0021] S2: Select the gradation design structure type based on the dominant particle size distribution and elastic modulus of the steel slag particles in the mixture; if the elastic modulus between coarse aggregates is >80GPa and the elastic modulus between fine aggregates is <1GPa, and the steel slag particle size is mainly coarse aggregate, adopt a suspended dense structure for gradation design, and design the mix proportion using CB-1 fine gradation; if the steel slag aggregate is mainly fine aggregate, adopt a skeleton void structure for gradation design, and design the mix proportion using CB-3 coarse gradation.

[0022] S3: By converting volume to mass, the mass percentage of each aggregate specification is obtained, thus yielding the final mix proportion;

[0023] S4: Add the graded natural aggregate, steel slag aggregate, cement and fly ash into the mixing equipment according to the design mix ratio obtained in step S3, and mix thoroughly until uniform to obtain a high-strength, low-shrinkage steel slag base mixture.

[0024] Furthermore, in step S1, the water immersion expansion rate of the steel slag aggregate is ≤1.0%, the free calcium oxide content is ≤2.0%, the autoclaving pulverization rate is ≤3.0%, and the metallic iron content is <2.0%.

[0025] The particle size of steel slag particles is divided into three grades: 10-20mm, 5-10mm, and 0-5mm.

[0026] Steel slag particles with a diameter > 5 mm are classified as coarse aggregate; steel slag particles with a diameter ≤ 5 mm are classified as fine aggregate.

[0027] Furthermore, when the proportion of coarse steel slag aggregate in the total amount of steel slag mixture is ≥50%, it is determined that the steel slag aggregate is mainly composed of coarse aggregate particles; when the proportion of fine steel slag aggregate in the total amount of steel slag mixture is ≥50%, it is determined that the steel slag aggregate is mainly composed of fine aggregate particles.

[0028] Furthermore, the volume-mass conversion in step S3 is expressed by equation (1):

[0029]

[0030] Among them, A mi A represents the mass percentage of aggregate of specification i in the mixture; Vi The volume percentage of aggregate of type i in the mixture; γ i This represents the bulk relative density of aggregate of the i-th specification, which is dimensionless. Bulk relative density refers to the ratio of the density of aggregate in its natural state (including internal pores) to its density in its saturated state, and is used to reflect the density characteristics of aggregate. This represents the sum of the products of the volume percentage of all aggregate sizes and their gross volume relative density. This sum is used for normalization calculations to ensure that the sum of the mass percentages of all aggregate sizes is 100%; n represents the total number of aggregate sizes.

[0031] A third aspect of the present invention provides a method for continuous weak vibration construction of a high-strength, low-shrinkage steel slag base mixture with half dosage, wherein the high-strength, low-shrinkage steel slag base mixture is used for on-site construction, comprising the following steps:

[0032] S100, Measurement calibration: The steel slag aggregate, natural aggregate, cement and fly ash are measured and calibrated according to the preset mix proportions.

[0033] S200, mixing: The raw materials of the high-strength, low-shrinkage steel slag base mixture are loaded into different hoppers and mixed to ensure uniform mixing of the materials;

[0034] S300, Loading: The material is loaded into the transport vehicle through a five-step loading method to reduce the segregation of coarse and fine aggregates;

[0035] S400, Paving: At the construction site, a dedicated person is assigned to direct the material trucks to unload material onto the paver, ensuring that the paver's hopper always contains a sufficient amount of mixture; the paving thickness is controlled between 15 and 25 cm; workers are arranged behind the paver to monitor and handle any potential segregation of coarse and fine materials in real time, ensuring the uniformity of the paving layer.

[0036] S500, compaction, operate continuously in the following sequence:

[0037] Static compaction: Use a 13-18t double-drum roller at a speed of 1.2-2.4 km / h for one pass of static compaction;

[0038] Continuous weak vibration: Use a 22-30t vibratory roller to perform weak vibration 4-6 times at a speed of 1.2-2.4km / h. The vibration parameters are limited to: frequency 25-30Hz, amplitude 0.4-0.8mm, and excitation force 250-350kN.

[0039] Compaction: Use a 26-30t rubber-tired roller to compact twice at a speed of 1.2-2.4 km / h;

[0040] Finishing: Use a 13-18t double-drum roller to perform static compaction once for finishing;

[0041] S600, Inspection and Curing: Conduct quality inspection on the compacted base course mixture to ensure it meets construction requirements; immediately cover the qualified base course mixture with geotextile or film and use spray watering for curing.

[0042] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects:

[0043] (1) The high-strength, low-shrinkage steel slag base mixture preparation and half-dosage continuous weak vibration construction method of the present invention uses steel slag as road construction aggregate, and controls the f-CaO of the steel slag aggregate to be ≤2.0% and the water immersion expansion rate to be ≤1.0% through source control; relying on the theory of steel slag-fly ash synergistic hydration to generate dense CSH gel, by adding 5% to 15% fly ash, when the steel slag dosage ratio reaches 25% to 60% (half-dosage), the drying shrinkage coefficient of the steel slag base mixture is ≤120με, which is 30% to 40% lower than that of traditional steel slag mixture, and meets the crack resistance requirements of cold / arid regions; the present invention can break through the volume stability bottleneck and realize the safe application of high-dosage steel slag.

[0044] (2) The high-strength, low-shrinkage steel slag base course mixture preparation and semi-admixture continuous weak vibration construction method of the present invention proposes a gradation optimization mechanism based on elastic modulus adaptation. The elastic modulus between coarse aggregates is >80GPa, and the elastic modulus between fine aggregates is <1GPa. If the steel slag particle size is mainly coarse aggregate, the coarse aggregate will expand and the expansion stress cannot be released. In order to prevent the disease caused by the expansion of the steel slag base course, a suspended dense structure should be adopted, preferably CB-1 fine gradation, and the 4.75mm sieve passing rate should be controlled at 30% to 35%. The fine aggregate filling buffers the interface stress concentration caused by the expansion of steel slag. If the steel slag particle size is mainly fine aggregate, when the fine aggregate expands, in order to prevent the pavement disease caused by the expansion of the steel slag base course, a skeleton porous structure should be adopted, preferably CB-3 coarse gradation, to reserve space for the expansion of fine aggregate, and limit the 4.75mm sieve passing rate to 25% to 30%.

[0045] (3) The high-strength, low-shrinkage steel slag base mixture preparation and semi-admixture continuous weak vibration construction method of the present invention innovatively adopts continuous weak vibration process (25-30Hz low frequency vibration + 0.4-0.8mm small amplitude + 250-350kN excitation force) to replace the traditional strong vibration. During the compaction process, the high-density steel slag and conventional crushed stone sink at the same speed and synchronously, completely eliminating vertical segregation caused by density difference; at the same time, a four-stage rolling closed loop is constructed: static pressing (leveling) → continuous weak vibration (uniform compaction) → rubber wheel kneading (eliminating micro-cracks) → static pressing finishing (sealing the surface), which solves the problem of density segregation and insufficient compaction from the root, and significantly improves the structural homogeneity and service life.

[0046] (4) The high-strength, low-shrinkage steel slag base course mixture preparation and semi-admixture continuous weak vibration construction method of the present invention increases the steel slag admixture to 25% to 60%, significantly increasing the steel slag consumption; reducing the amount of crushed stone mining and alleviating the pressure of sand and gravel resource depletion; by replacing crushed stone with steel slag, carbon emissions from material mining and transportation can be reduced; and the amount of cement used can be reduced through the potential activity of steel slag itself and the chemical regulation of steel slag-fly ash; achieving a double leap in economic, resource and environmental benefits; through the three-in-one innovation of "material-structure-process", with semi-admixture steel slag (25% to 60%) as the core and continuous weak vibration process as the breakthrough point, it not only overcomes the industry problem of steel slag base course application, but also achieves significant progress in "improved solid waste disposal capacity + extended road surface life + reduced carbon emissions", which is of great significance for promoting the green transformation of transportation infrastructure. Attached Figure Description

[0047] Figure 1 This is a schematic diagram of the overall process of a method for preparing high-strength, low-shrinkage steel slag base mixture and performing semi-admixture continuous weak vibration construction according to an embodiment of the present invention.

[0048] Figure 2 This is a schematic diagram illustrating the selection of a suspended dense structure for gradation design in a method for preparing a high-strength, low-shrinkage steel slag base mixture according to an embodiment of the present invention.

[0049] Figure 3 This is a schematic diagram illustrating the selection of a skeleton void structure for gradation design in a method for preparing a high-strength, low-shrinkage steel slag base mixture according to an embodiment of the present invention.

[0050] Figure 4 This is a schematic diagram of the gradation curve of the suspended dense structure used in Embodiment 4 of the present invention;

[0051] Figure 5 This is a schematic diagram of the core sample taken after drilling in Embodiment 4 of the present invention;

[0052] Figure 6 This is a schematic diagram of the gradation curve using a skeleton void structure in Embodiment 5 of the present invention;

[0053] Figure 7 This is a schematic diagram of the core sample taken after drilling in Embodiment 5 of the present invention. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0055] Example 1

[0056] Embodiment 1 of the present invention provides a high-strength, low-shrinkage steel slag base course mixture, comprising the following base course raw materials in the following volume ratios: 40%–75% natural aggregate, 25%–60% steel slag aggregate, 3.0%–5.0% cement admixture, and 5.0%–10.0% fly ash admixture; the maximum dry density of the high-strength, low-shrinkage steel slag base course mixture is 2.35–2.55 g / cm³. 3 The optimal moisture content is 4.0–6.0%.

[0057] Furthermore, the steel slag aggregate is graded into three sizes: 10–20 mm, 5–10 mm, and 0–5 mm; the water immersion expansion rate of the steel slag aggregate is ≤1.0%, the free calcium oxide content is ≤2.0%, the autoclaving pulverization rate is ≤3.0%, and the metallic iron content is <2.0%; the natural aggregate includes crushed stone or gravel. The cement is ordinary Portland cement with an initial setting time >4 h and a final setting time >6 h.

[0058] Furthermore, the fly ash can effectively inhibit the expansion of steel slag. It can be made from raw fly ash or Class I fly ash. When raw fly ash is used, the amount of raw fly ash is limited to 15%–20% of the mass of the steel slag aggregate, and the total amount of fly ash is ≥ 5% of the total mass of the mixture. When Class I fly ash is used, the amount of Class I fly ash is limited to 10%–15% of the mass of the steel slag aggregate, and the total amount of fly ash is ≥ 5% of the total mass of the mixture.

[0059] Furthermore, the 7-day unconfined compressive strength of the steel slag base mixture is ≥4.0MPa; the drying shrinkage coefficient is ≤120με.

[0060] Example 2

[0061] like Figure 1 As shown, Embodiment 2 of the present invention provides a method for preparing a high-strength, low-shrinkage steel slag base course mixture, comprising the following steps:

[0062] S1: Weigh out natural aggregate, steel slag aggregate, cement, and fly ash by volume ratios of 40%–75%, 25%–60%, 3.0%–5.0%, and 5.0%–10.0%, respectively; classify the steel slag aggregate by particle size to determine the mass ratio of coarse and fine aggregates in the steel slag aggregate; and determine the elastic modulus of natural aggregate and steel slag aggregate.

[0063] S2: Select the gradation design structure type based on the dominant particle size distribution and elastic modulus of the steel slag particles in the mixture; if the elastic modulus between coarse aggregates is >80GPa and the elastic modulus between fine aggregates is <1GPa, and the steel slag particle size is mainly coarse aggregate, adopt a suspended dense structure for gradation design, and design the mix proportion using CB-1 fine gradation; if the steel slag aggregate is mainly fine aggregate, adopt a skeleton void structure for gradation design, and design the mix proportion using CB-3 coarse gradation.

[0064] S3: By converting volume to mass, the mass percentage of each aggregate specification is obtained, thus yielding the final mix proportion;

[0065] S4: Add the graded natural aggregate, steel slag aggregate, cement and fly ash into the mixing equipment according to the design mix ratio obtained in step S3, and mix thoroughly until uniform to obtain a high-strength, low-shrinkage steel slag base mixture.

[0066] Furthermore, in step S1, the water immersion expansion rate of the steel slag aggregate is ≤1.0%, the free calcium oxide content is ≤2.0%, the autoclaving pulverization rate is ≤3.0%, and the metallic iron content is <2.0%.

[0067] The particle size of steel slag particles is divided into three grades: 10-20mm, 5-10mm, and 0-5mm.

[0068] Steel slag particles with a diameter > 5 mm are classified as coarse aggregate; steel slag particles with a diameter ≤ 5 mm are classified as fine aggregate.

[0069] Furthermore, in step S2, when the proportion of coarse steel slag aggregate in the total amount of steel slag mixture is ≥50%, it is determined that the steel slag aggregate is mainly composed of coarse aggregate particles.

[0070] The elastic modulus of steel slag coarse aggregate is >80 GPa. Since the steel slag coarse aggregate forms a rigid interface with natural crushed stone, fine aggregates are needed to fill the pores to form a homogeneous body to prevent stress concentration. Therefore, a suspended dense structure is selected for gradation design (e.g., Figure 2 (As shown), the mix design is carried out using the CB-1 fine gradation template;

[0071] Figure 2The diagram illustrates a design concept using a suspended dense structure; the red portion represents steel slag particles, and the gray portion represents fine aggregates. In this structure, the steel slag particles are surrounded by fine aggregates, forming a suspended state, which helps to disperse stress and reduce the risk of expansion. It is recommended to use a finer gradation such as CB-1 for mix design.

[0072] When the proportion of fine aggregate in the total amount of steel slag mixture is ≥50%, it is determined that the steel slag aggregate is mainly composed of fine aggregate particles.

[0073] The elastic modulus between fine steel slag aggregates is <1 GPa, indicating that the modulus of fine steel slag is close to that of natural sand. The strength of the mixture is mainly determined by the skeletal effect between coarse aggregates. To prevent the potential expansion risk of steel slag and to safely fill the pores of the skeletal structure, coarse aggregates are needed to construct a mechanical skeleton. The gradation design should be based on a skeletal structure with appropriate voids (e.g., ...). Figure 3 As shown), the steel slag fine aggregate only serves as a filler, and the mix design is carried out using the CB-3 coarse gradation template;

[0074] Figure 3 This diagram illustrates a design concept employing a skeleton-void structure. In this structure, the strength between the mixture is primarily determined by the skeletal effect of the coarse aggregates, while the fine steel slag aggregates only serve a filling function. The gray areas in the diagram represent coarse aggregates, and the red areas represent the fine steel slag aggregates. In this structure, the coarse aggregates form the skeleton, and the fine steel slag aggregates fill the voids between the skeletons, contributing to improved overall strength and stability of the mixture.

[0075] CB-1 fine gradation template is suitable for suspended dense structures with a high proportion of fine materials and is compatible with continuous weak vibration processes; CB-3 coarse gradation template is suitable for skeleton void structures, with coarse materials interlocking to resist the expansion stress of steel slag.

[0076] In the gradation design of the suspended dense structure, the 4.75mm passing rate is controlled at 30% to 35%, and the micro powder fills the gaps between the steel slag coarse materials to suppress the interface cracks caused by the difference in modulus.

[0077] In the gradation design of the skeleton void structure, the 4.75mm passing rate is controlled at 25% to 30% to ensure the coarse aggregate skeleton is interlocked, and the steel slag fine aggregate only fills the pores and is strictly prohibited from participating in the skeleton construction to avoid the risk of expansion.

[0078] Unconfined compressive strength (7d) of the suspended dense structure ≥ 4.0 MPa; shrinkage coefficient ≤ 120 με;

[0079] The unconfined compressive strength (7d) of the skeleton void structure is ≥4.5MPa; the drying shrinkage coefficient is ≤100με; and the skeleton void ratio is ≤20%.

[0080] Step S2 addresses the interfacial stress and volume stability issues of high-content steel slag through elastic modulus-gradation linkage control.

[0081] Further, step S3 includes:

[0082] S31: Determine the physical parameters of raw materials, and test the bulk relative density, water absorption rate and bulk density of each specification of aggregate, including natural aggregate and steel slag aggregate, for each grade; the bulk relative density is tested according to the "Specifications for Testing Aggregates for Highway Engineering" (JTG 3432) T 0304; the water absorption rate is used to verify the influence of moisture content on density; the bulk density is used to assist in verifying the grade mixability.

[0083] S32: Based on the gradation design results of step S2, determine the volume percentage of each aggregate specification in the mixture; the sum of the volume percentages of each aggregate specification in the mixture is 100%.

[0084] S33: Perform volume-mass conversion to obtain the mass percentage of each aggregate specification;

[0085] S34: Verify the compatibility of the mix proportions. Substitute the mass percentage results into the mixture design and check whether it meets the following requirement: maximum dry density 2.35~2.55g / cm³. 3 The optimal moisture content was determined to be 4.0%–6.0% through compaction tests.

[0086] S35: Generate a standardized mix proportion table, clearly defining the mass percentage of each component.

[0087] Furthermore, the volume-mass conversion in step S33 is expressed by equation (1):

[0088]

[0089] Among them, A mi A represents the mass percentage of aggregate of specification i in the mixture; Vi The volume percentage of aggregate of type i in the mixture; γ i This represents the bulk relative density of aggregate of the i-th specification, which is dimensionless. Bulk relative density refers to the ratio of the density of aggregate in its natural state (including internal pores) to its density in its saturated state, and is used to reflect the density characteristics of aggregate. This represents the sum of the products of the volume percentage of all aggregate sizes and their gross volume relative density. This sum is used for normalization calculations to ensure that the sum of the mass percentages of all aggregate sizes is 100%; n represents the total number of aggregate sizes.

[0090] Step S3 calculates the mass percentage of each aggregate in the mixture based on the volume ratio and bulk relative density of the aggregates, thus obtaining the final mix proportion. Step S3 ensures that the steel slag content is precisely controllable within the range of 25% to 60%; the mix gradation meets the design requirements of suspended / skeletal void structure; and provides the mix proportion foundation for the "high strength (compressive strength ≥4MPa) and low shrinkage (dry shrinkage ≤120με)" described in Example 1. The volume-mass dynamic conversion formula solves the problem of distorted proportions between the high density of steel slag and the low density of crushed stone, ensuring the accurate implementation of the designed gradation.

[0091] Example 3

[0092] like Figure 1 As shown, Embodiment 3 of the present invention provides a method for continuous weak vibration construction of high-strength, low-shrinkage steel slag base mixture with half dosage, comprising the following steps:

[0093] S100, Measurement calibration: The steel slag aggregate, natural aggregate, cement and fly ash are measured and calibrated according to the preset mix proportions.

[0094] S200, mixing: The raw materials of the high-strength, low-shrinkage steel slag base mixture are loaded into different hoppers and mixed to ensure uniform mixing of the materials;

[0095] S300, Loading: The material is loaded into the transport vehicle through a five-step loading method to reduce the segregation of coarse and fine aggregates;

[0096] S400, paving: At the construction site, a dedicated person is assigned to direct the material trucks to unload material onto the paver, ensuring that the paver's hopper always contains a sufficient amount of mixture; the paving thickness is controlled between 15 and 25 cm; 3 to 4 workers are arranged behind the paver to monitor and handle any potential segregation of coarse and fine materials in real time, ensuring the uniformity of the paving layer.

[0097] In step S400, ensuring that the paver's hopper always contains a sufficient amount of mixture can reduce segregation caused by insufficient material in the hopper, i.e., the separation of coarse and fine aggregates.

[0098] The paving thickness is controlled between 15 and 25 cm. This thickness range is determined according to project requirements and material properties to ensure the stability and load-bearing capacity of the base layer.

[0099] If segregation is found behind the paver, workers should promptly remove the segregated mixture and fill it with a uniformly coarse mixture. This will ensure the uniformity and density of the paved layer and prevent structural defects caused by segregation.

[0100] By using a five-step material loading method and real-time repair of segregation during paving, a closed loop for segregation control is formed from mixing to paving, which greatly improves the uniformity of the mixture.

[0101] S500, compaction, operate continuously in the following sequence:

[0102] Static compaction: Use a 13-18t double-drum roller at a speed of 1.2-2.4 km / h for one pass of static compaction;

[0103] Continuous weak vibration: Use a 22-30t vibratory roller to perform weak vibration 4-6 times at a speed of 1.2-2.4km / h. The vibration parameters are limited to: frequency 25-30Hz, amplitude 0.4-0.8mm, and excitation force 250-350kN.

[0104] Compaction: Use a 26-30t rubber-tired roller to compact twice at a speed of 1.2-2.4 km / h;

[0105] Finishing: Use a 13-18t double-drum roller to perform static compaction once for finishing;

[0106] S600, Inspection and Curing: Conduct quality inspection on the compacted base course mixture to ensure it meets construction requirements; immediately cover the qualified base course mixture with geotextile or film and use spray watering for curing.

[0107] Furthermore, after the mixture is paved and shaped in step S500, it should be compacted promptly. The compacted sections must be clearly layered and marked with obvious boundary markers. The roller should compact the mixture from both sides towards the center, overlapping each wheel's track by 1 / 3. During compaction, the roller must travel smoothly and at a constant speed without any impact. The compaction process in step S500 prevents insufficient compaction and segregation of the steel slag mixture, improves road performance, and extends road service life.

[0108] Furthermore, in step S600, when the water truck is used for water spraying and curing, the water truck nozzles must be spray type, and high-pressure nozzles are strictly prohibited to avoid damaging the base structure.

[0109] Example 4

[0110] Taking a national highway in Northwest China as an example, 600m of steel slag base course was laid. The specific mixing scheme is shown in Table 1:

[0111] Table 1: Specific mixing scheme for laying 600m of steel slag base course

[0112]

[0113] In this embodiment, the steel slag content is 31%, of which coarse steel slag aggregate accounts for 71% of the total steel slag content. The mix design adopts a suspended dense structure, and CB-1 gradation is used as the recommended gradation. The 4.75mm sieve passing rate of this scheme is 36%. The gradation curve is as follows. Figure 4 As shown;

[0114] The construction process in this embodiment is as follows:

[0115] The measurement calibration, mixing, transportation, spreading, testing, and curing processes are all consistent with traditional methods.

[0116] The specific rolling process is as follows;

[0117] Static compaction: A 13-18t double-drum roller is used for static compaction at a speed of 1.2-2.4 km / h;

[0118] Weak vibration: A 22-30t vibratory roller is used for weak vibration compaction at a speed of 1.2-2.4km / h. The vibration parameters are limited to: frequency 25-30Hz, amplitude 0.4-0.8mm, and excitation force 250-350kN.

[0119] Compaction: Use a 26-30t rubber-tired roller at a speed of 1.2-2.4 km / h for compaction;

[0120] Finishing: Static compaction using a 13-18t double-drum roller;

[0121] The specific compaction process is as follows:

[0122] 1 pass of static pressing + 3 passes of (weak vibration + kneading) + 1 pass of static pressing;

[0123] After 7 days of curing, core samples were taken, and the core samples are shown below. Figure 5 The core sample shows that the base layer surface is free of pores and steel slag segregation, indicating good compaction. The representative value of its 7-day unconfined compressive strength is 4.67 MPa, with a coefficient of variation of 4.04%, indicating a small coefficient of variation in the base layer strength, good construction quality, and strength meeting the specifications.

[0124] Example 5

[0125] Taking a highway in Northwest China as an example, 1000m of steel slag base course was laid. The specific mixing scheme is shown in Table 2:

[0126] Table 2: Specific mixing scheme for laying 600m of steel slag base course

[0127]

[0128] In this embodiment, the steel slag content is 49%, of which fine steel slag aggregate accounts for 53.06% of the total steel slag content. The mix design adopts a skeleton void structure, and CB-3 gradation is used as the recommended gradation. The passing rate of this scheme through a 4.75mm sieve is 28%. The gradation curve is shown in [reference needed]. Figure 6 ;

[0129] The construction process in this embodiment is as follows:

[0130] The measurement calibration, mixing, transportation, spreading, testing, and curing processes are all consistent with traditional methods.

[0131] The specific rolling process is as follows:

[0132] Static compaction: A 13-18t double-drum roller is used for static compaction at a speed of 1.2-2.4 km / h;

[0133] Weak vibration: A 22-30t vibratory roller is used for weak vibration compaction at a speed of 1.2-2.4km / h. The vibration parameters are limited to: frequency 25-30Hz, amplitude 0.4-0.8mm, and excitation force 250-350kN.

[0134] Compaction: Use a 26-30t rubber-tired roller at a speed of 1.2-2.4 km / h for compaction;

[0135] Finishing: Static compaction using a 13-18t double-drum roller;

[0136] The specific compaction process is as follows:

[0137] Static pressing 1 time + (weak vibration 1 time + kneading 1 time) * 4 times + static pressing 1 time;

[0138] After 7 days of curing, core samples were taken, and the core samples are shown below. Figure 7 The core sample shows that the base layer surface is free of pores and steel slag segregation, indicating good compaction. The representative value of its 7-day unconfined compressive strength is 5.67 MPa, with a coefficient of variation of 3.15%, indicating a small coefficient of variation in the base layer strength, good construction quality, and strength meeting the specifications.

[0139] This invention achieves a disruptive breakthrough in steel slag base course technology through a three-pronged innovation of "materials-structure-process": combining the steel slag-fly ash volcanic ash reaction mechanism and the gradation optimization mechanism that uses physical means to suppress the expansion risk of steel slag, it breaks through the traditional application approach with low steel slag content and achieves high strength and low shrinkage of steel slag pavement base course; through continuous weak vibration process combined with four-stage rolling closed loop, density segregation is eliminated, ultimately achieving a triple leap in resources-technology-environmental protection, a significant increase in solid waste disposal capacity, a significant extension of pavement life, and a significant reduction in carbon emissions.

[0140] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements 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 high-strength, low-shrinkage steel slag base mixture, characterized in that, The base course materials include the following volumetric proportions: 40%–75% natural aggregate, 25%–60% steel slag aggregate, 3.0%–5.0% cement admixture, and 5.0%–15.0% fly ash admixture; among which, The natural aggregates include crushed stone or gravel; The maximum dry density of the high-strength, low-shrinkage steel slag base course mixture is 2.35–2.55 g / cm³. 3 The optimal moisture content is 4.0–6.0%. The 7-day unconfined compressive strength of the steel slag base mixture is ≥4.0MPa; the drying shrinkage coefficient is ≤120με.

2. The high-strength, low-shrinkage steel slag base mixture according to claim 1, characterized in that: The steel slag aggregate is divided into three particle size grades: 10-20mm, 5-10mm, and 0-5mm.

3. The high-strength, low-shrinkage steel slag base mixture according to claim 2, characterized in that: The steel slag aggregate has a water immersion expansion rate ≤1.0%, a free calcium oxide content ≤2.0%, a steam autoclaving pulverization rate ≤3.0%, and a metallic iron content <2.0%.

4. A high-strength, low-shrinkage steel slag base course mixture according to any one of claims 1-3, characterized in that: The cement is ordinary Portland cement with an initial setting time of >4h and a final setting time of >6h.

5. The high-strength, low-shrinkage steel slag base mixture according to claim 4, characterized in that: The fly ash used is raw fly ash or Grade I fly ash; When the fly ash used is raw fly ash, the amount of raw fly ash is limited to 15% to 20% of the mass of steel slag aggregate, and the total amount of fly ash is ≥ 5% of the total mass of the mixture. When the fly ash used is Grade I fly ash, the amount of Grade I fly ash is limited to 10% to 15% of the mass of steel slag aggregate, and the total amount of fly ash is ≥ 5% of the total mass of the mixture.

6. A method for preparing a high-strength, low-shrinkage steel slag base course mixture, characterized in that, The preparation of the high-strength, low-shrinkage steel slag base mixture as described in any one of claims 1-5 comprises the following steps: S1: Weigh out natural aggregate, steel slag aggregate, cement, and fly ash by volume ratios of 40%–75%, 25%–60%, 3.0%–5.0%, and 5.0%–10.0%, respectively; classify the steel slag aggregate by particle size to determine the mass ratio of coarse and fine aggregates in the steel slag aggregate; and determine the elastic modulus of natural aggregate and steel slag aggregate. S2: Select the gradation design structure type based on the dominant particle size distribution and elastic modulus of the steel slag particles in the mixture; if the elastic modulus between coarse aggregates is >80GPa and the elastic modulus between fine aggregates is <1GPa, and the steel slag particle size is mainly coarse aggregate, adopt a suspended dense structure for gradation design, and design the mix proportion using CB-1 fine gradation; if the steel slag aggregate is mainly fine aggregate, adopt a skeleton void structure for gradation design, and design the mix proportion using CB-3 coarse gradation. S3: By converting volume to mass, the mass percentage of each aggregate specification is obtained, thus yielding the final mix proportion; S4: Add the graded natural aggregate, steel slag aggregate, cement and fly ash into the mixing equipment according to the design mix ratio obtained in step S3, and mix thoroughly until uniform to obtain a high-strength, low-shrinkage steel slag base mixture.

7. The method for preparing a high-strength, low-shrinkage steel slag base course mixture according to claim 6, characterized in that: In step S1, the water immersion expansion rate of the steel slag aggregate is ≤1.0%, the free calcium oxide content is ≤2.0%, the autoclaving pulverization rate is ≤3.0%, and the metallic iron content is <2.0%. The particle size of steel slag particles is divided into three grades: 10-20mm, 5-10mm, and 0-5mm. Steel slag particles with a diameter > 5 mm are classified as coarse aggregate; steel slag particles with a diameter ≤ 5 mm are classified as fine aggregate.

8. The method for preparing a high-strength, low-shrinkage steel slag base course mixture according to claim 6, characterized in that: In step S2, when the proportion of coarse steel slag aggregate in the total amount of steel slag mixture is ≥50%, it is determined that the steel slag aggregate is mainly composed of coarse aggregate particles; when the proportion of fine steel slag aggregate in the total amount of steel slag mixture is ≥50%, it is determined that the steel slag aggregate is mainly composed of fine aggregate particles.

9. The method for preparing a high-strength, low-shrinkage steel slag base course mixture according to claim 6, characterized in that: The volume-mass conversion in step S3 is expressed by equation (1): Among them, A mi A represents the mass percentage of aggregate of specification i in the mixture; Vi The volume percentage of aggregate of type i in the mixture; γ i This represents the bulk relative density of aggregate of the i-th specification, which is dimensionless. Bulk relative density refers to the ratio of the density of aggregate in its natural state (including internal pores) to its density in its saturated state, and is used to reflect the density characteristics of aggregate. This represents the sum of the products of the volume percentage of all aggregate sizes and their gross volume relative density. This sum is used for normalization calculations to ensure that the sum of the mass percentages of all aggregate sizes is 100%; n represents the total number of aggregate sizes.

10. A method for continuous weak vibration construction of a high-strength, low-shrinkage steel slag base mixture with half-admixture, characterized in that: The on-site construction using the high-strength, low-shrinkage steel slag base mixture as described in any one of claims 1-5 includes the following steps: S100, Measurement calibration: The steel slag aggregate, natural aggregate, cement and fly ash are measured and calibrated according to the preset mix proportions. S200, mixing: The raw materials of the high-strength, low-shrinkage steel slag base mixture are loaded into different hoppers and mixed to ensure uniform mixing of the materials; S300, Loading: The material is loaded into the transport vehicle through a five-step loading method to reduce the segregation of coarse and fine aggregates; S400, Paving: At the construction site, a dedicated person is assigned to direct the material trucks to unload material onto the paver, ensuring that the paver's hopper always contains a sufficient amount of mixture; the paving thickness is controlled between 15 and 25 cm; workers are arranged behind the paver to monitor and handle any potential segregation of coarse and fine materials in real time, ensuring the uniformity of the paving layer. S500, compaction, operate continuously in the following sequence: Static compaction: Use a 13-18t double-drum roller at a speed of 1.2-2.4 km / h for one pass of static compaction; Continuous weak vibration: Use a 22-30t vibratory roller to perform weak vibration 4-6 times at a speed of 1.2-2.4km / h. The vibration parameters are limited to: frequency 25-30Hz, amplitude 0.4-0.8mm, and excitation force 250-350kN. Compaction: Use a 26-30t rubber-tired roller to compact twice at a speed of 1.2-2.4 km / h; Finishing: Use a 13-18t double-drum roller to perform static compaction once for finishing; S600, Inspection and Curing: Conduct quality inspection on the compacted base course mixture to ensure it meets construction requirements; immediately cover the qualified base course mixture with geotextile or film and use spray watering for curing.

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