A crushed stone roadbed material and a method of manufacturing the same

Abstract

This invention discloses a crushed pebble roadbed material and its preparation method, belonging to the technical field of road engineering materials. By mass, the roadbed material consists of 300-500 parts crushed pebbles, 100 parts cement, 5-10 parts rubber granules, 0.5-2 parts water-reducing agent, and 30-50 parts water. The crushed pebbles are a single-pebble crushing product. This single-pebble crushing product is divided into four grades according to different particle sizes. Through a four-grade gradation design of the crushed pebble material, sodium hydroxide pretreatment, and rubber granule composite anti-aging modification, without adding other sand and gravel fillers, a high-performance crushed pebble roadbed material is successfully prepared. This material far surpasses traditional roadbed materials in terms of strength, density, water stability, anti-aging properties, and high and low temperature performance, realizing the resource utilization of waste rubber and is suitable for roadbed construction in various road engineering projects.

Description

Technical Field

[0001] This application relates to the field of road engineering materials technology, specifically to a crushed pebble roadbed material and its preparation method. The roadbed prepared using graded crushed pebble material and rubber particles has higher strength and is especially suitable for high-grade highways, municipal roads and other projects with high roadbed performance requirements. Background Technology

[0002] In road construction, the roadbed is an earthwork structure formed through excavation or filling. As the foundational load-bearing structure of the road, it bears both static and dynamic loads from the pavement and traffic, while simultaneously transferring and dispersing these loads deep into the foundation. The performance of the roadbed directly affects the service life and driving safety of the road, and its quality directly determines the overall stability and durability of the road. Existing roadbeds use traditional paving structures, with the bottom layer made of relatively coarse-grained materials such as sand, gravel, and soil. This results in low density and strength, limiting the load-bearing capacity of the bottom layer. Furthermore, with the increasing scarcity of natural resources and ever-increasing environmental protection requirements, the search for new, environmentally friendly, and high-performance roadbed materials has become a research hotspot in the field of road engineering.

[0003] Pebbles, as a natural aggregate, are widely distributed in my country, with abundant reserves along rivers and lakes. Rational utilization can reduce road construction costs and decrease reliance on other natural resources. However, natural pebbles are characterized by rounded particles, smooth surfaces, and poor gradation, leading to compaction difficulties and poor stability when used directly as roadbed materials. Therefore, in existing roadbed or road construction, pebbles are mostly used as large-diameter aggregate additives or for laying and filling simple large-diameter layers. For example, CN106284011B discloses a roadbed construction method that involves excavating drainage trenches and placing prestressed pipe piles on the outside of the roadbed, followed by excavating the base course, and then sequentially laying a crushed stone cushion layer, a geogrid layer, a reinforced concrete layer, a geotextile filter layer, and an asphalt layer. This effectively stabilizes the base course, improves seepage prevention, and reduces settlement. The crushed stone cushion layer is composed of pebbles or crushed stone blocks with a particle size range of 30-40mm, compacted and laid. CN216275067U discloses a method for reinforcing newly filled roadbeds, comprising a rubble layer, a crushed stone layer, a sand cushion layer, and a steel-plastic composite grid. The roadbed is trapezoidal, consisting of a rubble layer, a crushed stone layer, and a sand cushion layer from bottom to top. The rubble layer is composed of irregularly shaped stones with a side length of not less than 15 cm, and the compacted thickness of the rubble layer is 30-50 cm. The crushed stone layer is composed of rock particles with a particle size greater than 4.75 mm, produced by mechanical crushing and screening of natural rocks or pebbles, and the compacted thickness of the crushed stone layer is 15-18 cm. The sand cushion layer is composed of medium-coarse sand, and the compacted thickness of the sand cushion layer is 15-18 cm. This method can improve the roadbed strength, ensure roadbed stability, prevent uneven settlement, and effectively solve the stability problem of newly filled roadbeds. CN213951802U discloses a highway subgrade structure with high load-bearing capacity. The subgrade consists of an upper base layer and a lower base layer. The upper base layer comprises an asphalt layer, a cement layer, and a concrete layer. The asphalt layer is fixedly laid on top of the cement layer, and the cement layer is fixedly laid on top of the concrete layer. The lower base layer comprises a crushed stone layer, a pebble layer, and a sand and gravel layer. The pebble layer is fixedly laid on top of the crushed stone layer. Several reinforcing structures are uniformly embedded inside the lower base layer to improve the load-bearing capacity of the subgrade. CN101343166B discloses a method for preparing impact-resistant ecological concrete. Rubber aggregate is pretreated with a rubber-cement matrix interface modifier. Then, a certain proportion of cement, coarse and fine aggregates, rubber aggregates, water, admixtures, and other materials are mixed and stirred evenly. After curing for a certain period, the concrete is prepared. The coarse aggregate is 5-30mm continuously graded crushed stone or river pebbles. This concrete exhibits significantly improved impact resistance and excellent workability. However, simply adding pebbles as aggregate to the roadbed cannot achieve effective utilization of pebbles. Furthermore, it still needs to be mixed with other aggregates for gradation, and a large amount of sand and gravel and other fillers need to be added to adjust the gradation. This fails to fully realize the application of single crushed pebble material, which not only increases material costs but may also lead to a waste of resources.

[0004] Therefore, preliminary processing of gravel has begun, such as crushing it to replace fine aggregate or crushing it into sand and gravel soil filler. Although it has good mechanical and permeability properties as filler, the arrangement of its coarse and fine particles is relatively complex. The density and gradation of sand and gravel soil vary from region to region and are difficult to control in engineering applications, resulting in complex and highly variable mechanical properties. In practical engineering applications, due to the difficulty in controlling the engineering properties of sand and gravel soil, projects using sand and gravel soil as filler material encounter difficulties in construction and the quality of construction is hard to guarantee, which has become a key problem restricting the application of sand and gravel soil. At the same time, the recycling of waste tires is also an important issue in the field of environmental protection. Crushing waste tires into rubber particles for use in roadbed materials can not only solve the environmental pollution problem of waste tires, but also improve the mechanical properties of roadbeds by utilizing the elasticity and toughness of rubber particles. Currently, there are technical solutions that directly inject concrete or granules into the inside of waste tires as filler, or crush waste tires into rubber particles and mix them into roadbed materials, utilizing the elasticity and toughness of the rubber particles or rubber materials themselves to improve the deformation resistance and shock absorption performance of the roadbed. For example, CN104058661A discloses a method for preparing hollow concrete blocks with added waste tire rubber particles. The raw materials are prepared in the following weight proportions: 302-375 parts cement, 565.7-607.2 parts medium-coarse river sand, 1180-1300 parts crushed stone and / or pebbles, 21.8-59.3 parts rubber particles, 2.385 parts water-reducing agent, and 106-134 parts water. The medium-coarse river sand, cement, water-reducing agent, and rubber particles are added to a mixer and mixed. Then crushed stone and / or pebbles are added, water is added, and the mixture is stirred to obtain a concrete slurry. The slurry is then molded in a molding machine, cured, demolded, and then naturally cured. The rubber particles have a particle size of 0.1-5mm and a reasonable gradation, making them suitable for use as load-bearing blocks for buildings with different load-bearing strength requirements. However, rubber granules are prone to aging in natural environments, and their interfacial bonding with inorganic materials such as river sand and pebbles is poor, easily leading to problems such as delamination and voids in the roadbed. Therefore, current research on the preparation of roadbed materials using pebbles and rubber granules still faces the following pressing problems that need to be overcome:

[0005] The unreasonable gradation design of crushed gravel requires the addition of other sand and gravel fillers, increasing costs and resource consumption and making it difficult to guarantee the stability of the gradation; the rubber granules have insufficient anti-aging properties, affecting the long-term stability of the roadbed; the binder has limited performance, easily softening at high temperatures and becoming brittle at low temperatures, and its interfacial adhesion with rubber granules and crushed gravel is insufficient, making it difficult to simultaneously meet the roadbed's requirements for high and low temperature resistance, adhesion performance, and anti-aging performance; traditional roadbeds have poor water stability and are easily damaged under the influence of rainwater infiltration and freeze-thaw cycles, affecting the normal use of the road.

[0006] Therefore, developing a crushed pebble roadbed material and its preparation method that can fully utilize the advantages of pebbles and rubber particles is of great significance for promoting the innovation and sustainable development of road engineering materials. It can also realize the environmentally friendly and efficient utilization of existing materials, turning waste into treasure, and has great economic value. Summary of the Invention

[0007] This invention addresses the aforementioned problems by employing a four-stage gradation design of crushed pebbles, sodium hydroxide pretreatment of the crushed pebble particles, anti-aging modification of rubber particles, and ratio optimization. This results in a high-performance modified subgrade material that uses only pebbles without adding other sand or gravel fillers. This provides a novel, environmentally friendly, and high-performance subgrade material for road engineering, achieving the goal of improving the subgrade's resistance to high and low temperatures, anti-aging properties, and water stability without adding other sand or gravel fillers. The subgrade material demonstrates outstanding performance in terms of environmental benefits and construction adaptability.

[0008] Specifically, this invention proposes a crushed pebble roadbed material, which, by mass fraction, is composed of the following raw materials:

[0009] 300-500 pieces of broken pebbles.

[0010] 100 parts cement

[0011] 5-10 parts rubber granules

[0012] Water-reducing agent 0.5-2 parts,

[0013] 30-50 parts water;

[0014] The crushed pebbles are single-pebble crushing products; the single-pebble crushing products are divided into four grades according to different particle size ranges, and by weight, they are as follows: 10wt%~30wt% of particles with a particle size range of 0.1mm-3mm (including the 0.1mm end point, excluding the 3mm end point), 20wt% of particles with a particle size range of 3mm-10mm (including the 3mm end point, excluding the 10mm end point), 30wt% of particles with a particle size range of 10mm-20mm (including the 10mm end point, excluding the 20mm end point), and 20wt%~40wt% of particles with a particle size range of 20mm-35mm (including the 20mm end point, excluding the 35mm end point). The four-stage gradation design in this invention achieves synergistic optimization of the "skeleton-filler" relationship. The crushed pebbles of four particle sizes form a continuous and complementary gradation system. Coarse particles (20mm-35mm, 20wt%~40wt%) act as the "skeleton core," providing anti-deformation support through mechanical interlocking and bearing the main load transfer. Medium particles (10mm-20mm, 30wt%) fill the gaps between coarse particles, breaking the voids (i.e., the "bridging effect") easily formed by traditional single-size particles, thus reducing macroscopic porosity. Fine particles (3mm-10mm, 20wt%) further fill the gaps between medium particles, reducing stress concentration between particles. Ultrafine particles (0.1mm-3mm, 10wt%~30wt%) combine with cement paste, filling microscopic pores and forming a dense cementitious transition zone. The four particle sizes cover the entire range of 0.1mm-35mm, and the cumulative sieve residue curve is smooth without jumps, minimizing porosity and far superior to traditional two- or three-stage gradations. Furthermore, this invention uses a single source of pebbles, which avoids differences in strength, water absorption, and other indicators caused by mixing pebbles from different origins, ensuring the stability of material performance and significantly reducing material performance fluctuations. The combination of cement, rubber particles, and water-reducing agents in the raw material formulation forms a synergistic system of "rigidity-flexibility-flowability." Cement, as the cementing core, binds the broken pebbles into a whole through hydration reactions (generating CSH gel, CH crystals, etc.), providing a foundation for strength. Rubber particles introduce a flexible phase, with an elastic modulus (0.1~1 GPa) much lower than that of pebbles (10~30 GPa) and cement paste (20~30 GPa), which can alleviate stress concentration caused by load impact and reduce crack initiation. The water-reducing agent can reduce water demand (by 10%~15%), improve the flowability of the cement paste, ensure its uniform coating of the pebble surface, and avoid weak interfacial areas caused by uneven paste dispersion. The water ratio is matched with the cement, ensuring sufficient cement hydration without increasing porosity due to excessive water.

[0015] Through extensive experimental verification, the applicant discovered that the roadbed material of this invention produces roadbeds with high strength and high density, significantly improving the compressive strength of the roadbed. The 28-day compressive strength can reach 5.0~7.5MPa, which is 30%~80% higher than that of traditional gravel roadbeds (28-day compressive strength ≤3.0MPa). The continuous gradation increases the number of contact points between particles by more than 30%, and a compaction degree of ≥97% can be achieved using conventional vibration compaction, with a dry density of 2.5~2.9g / cm³. 3 It is far superior to traditional materials; its water stability is enhanced, and the dense structure and uniform cement coating reduce water penetration channels. The strength loss after 7 days of immersion is ≤5%, and the permeability coefficient is ≤1×10⁻⁶. -7 With a particle size distribution of cm / s, it can adapt to rainy or high groundwater levels; its crack resistance and frost resistance are improved, and the elastic buffering effect of the rubber particles can absorb the volume expansion stress generated by freeze-thaw cycles, with a strength loss of ≤8% after 300 freeze-thaw cycles; at the same time, the rubber particles can inhibit drying shrinkage cracks (reducing the shrinkage rate by 20%~30%). The solution proposed in this application, through specific particle size distribution, precisely controls the particle size distribution and raw material ratio, balancing the rigidity and toughness, strength and durability of the material, while taking into account environmental protection and construction requirements, providing a high-performance and sustainable roadbed solution for road engineering.

[0016] Preferably, the crushed pebbles are single-pebble crushing products; the single-pebble crushing products are divided into four grades according to different particle size ranges, and by weight, they are as follows: 12wt%~20wt% of particles with a particle size range of 0.1mm-3mm (including the 0.1mm end point, excluding the 3mm end point), 20wt% of particles with a particle size range of 3mm-10mm (including the 3mm end point, excluding the 10mm end point), 30wt% of particles with a particle size range of 10mm-20mm (including the 10mm end point, excluding the 20mm end point), and 30wt%~38wt% of particles with a particle size range of 20mm-35mm (including the 20mm end point, excluding the 35mm end point).

[0017] Preferably, the crushed pebbles are single-pebble crushing products; the single-pebble crushing products are divided into four grades according to different particle size ranges, and by weight, they are as follows: 15wt%~18wt% of particles with a particle size range of 0.1mm-3mm (including the 0.1mm end point, excluding the 3mm end point), 20wt% of particles with a particle size range of 3mm-10mm (including the 3mm end point, excluding the 10mm end point), 30wt% of particles with a particle size range of 10mm-20mm (including the 10mm end point, excluding the 20mm end point), and 32wt%~35wt% of particles with a particle size range of 20mm-35mm (including the 20mm end point, excluding the 35mm end point).

[0018] Preferably, the crushed pebbles are single-pebble crushing products; the single-pebble crushing products are divided into four grades according to different particle size ranges, and by weight, they are as follows: 15wt% of particles with a particle size range of 0.1mm-3mm (including the 0.1mm end point, excluding the 3mm end point), 20wt% of particles with a particle size range of 3mm-10mm (including the 3mm end point, excluding the 10mm end point), 30wt% of particles with a particle size range of 10mm-20mm (including the 10mm end point, excluding the 20mm end point), and 35wt% of particles with a particle size range of 20mm-35mm (including the 20mm end point, excluding the 35mm end point).

[0019] As a preferred embodiment, the rubber granules are waste tire crushed granules impregnated with an anti-aging agent, with a particle size of 1-5 mm. The anti-aging agent is a composite system of 2,2,4-trimethyl-1,2-dihydroquinoline polymer (TMQ) and nano zinc oxide, wherein the mass ratio of 2,2,4-trimethyl-1,2-dihydroquinoline polymer to nano zinc oxide is 3:1, and the mass concentration of the impregnation solution is 3%-5%. Through extensive experiments, the applicant has discovered that introducing waste tire rubber granules impregnated with a specific anti-aging agent, through the synergistic effect of the anti-aging agent and precise process control, can significantly improve the durability of the rubber granules and their interfacial compatibility with the matrix material, thereby endowing the roadbed material with superior long-term performance and environmental adaptability. The composite anti-aging agent system, through a synergistic mechanism of "chemical protection + physical shielding," fundamentally delays the aging and degradation process of the rubber granules. TMQ can inhibit the oxidative breakage of rubber molecular chains by capturing peroxide free radicals (ROO•) generated during rubber oxidation, thus interrupting the chain reaction. Nano-zinc oxide (ZnO) with a particle size of 50-100nm exhibits strong absorption of ultraviolet light in the 200-400nm wavelength range, a major cause of photoaging in rubber, with an absorption rate ≥90%. It can form a physical barrier to reduce UV damage to the rubber's interior. When combined with TMQ at a mass ratio of 1:3, the hydroxyl groups on the surface of nano-ZnO can form hydrogen bonds with TMQ molecules, ensuring uniform dispersion of the antioxidant on the rubber surface and preventing localized accumulation or loss. Simultaneously, Zn... 2+It can catalytically decompose the hydroperoxides (ROOH) produced by rubber oxidation, reducing the regeneration of active free radicals and forming a dual protection of "free radical capture - peroxide decomposition" with TMQ. Furthermore, the rubber particle size is controlled at 1-5mm, achieving size matching with the four-level gradation of crushed pebbles, while the moderate roughness (Ra=0.8-1.2μm) of the anti-aging agent protective film can form microscopic mechanical interlocking with cement hydration products (CSH gel), reducing interfacial slippage. At high temperatures, the anti-aging agent can inhibit the thermo-oxidative aging of rubber, reducing the strength loss at 80℃ for 24 hours from 35% to below 6%, preventing subgrade deformation caused by rubber softening. At low temperatures, the treated rubber particles retain good elasticity, buffering frost heave stress and reducing cracks caused by freeze-thaw cycles. The anti-aging agent protective film can reduce the water absorption rate of rubber particles, reducing interfacial delamination caused by moisture penetration. A 7-day immersion test showed that the strength loss of the roadbed material containing treated rubber granules was ≤4.5%, and after 3 years of field exposure testing, its compressive strength retention rate still reached over 90%. More importantly, the use of waste tire rubber granules itself achieves solid waste resource utilization, while anti-aging treatment can improve its long-term stability in the roadbed and avoid secondary pollution of microplastics caused by rubber degradation. After treatment with composite anti-aging agents, the structural integrity of the rubber granules can be maintained for more than 15 years, and the release of microplastics is reduced by more than 90%, meeting the environmental protection requirements of "zero-waste engineering".

[0020] As a preferred embodiment, the cement is at least one of aluminate cement, silicate cement, and sulfoaluminate cement.

[0021] As a preferred embodiment, the water-reducing agent is a polycarboxylate water-reducing agent.

[0022] As a preferred embodiment, the single pebble crushing product is pretreated by soaking and washing it in a 0.1M~1M sodium hydroxide solution for 0.5~3 hours, and then taking it out and rinsing it repeatedly with deionized water until the crushed pebbles are neutral. Pretreatment of crushed pebble products with 0.1M~1M sodium hydroxide solution can enhance the "macro-micro" dual roughness structure between pebbles and cement matrix and rubber particles, strengthening mechanical interlocking force. Natural pebbles usually have smooth surfaces and low porosity, resulting in weak physical interlocking with cement paste and rubber particles. The main components of pebbles are quartz (SiO2) and feldspar (such as calcium feldspar). In 0.1M~1M alkaline solution, non-uniform corrosion occurs. Quartz reacts slowly in this concentration of alkaline solution, while feldspar reacts violently, forming honeycomb-like pits. That is, the corrosion effect of sodium hydroxide solution on pebbles has the characteristic of "selective etching". This selective corrosion forms macro grooves of 0.5~2mm on the pebble surface. Combined with the angular structure after crushing, the mechanical interlocking force between particles is increased by 40%~60%. Furthermore, the alkaline solution penetrates the surface of the pebbles, dissolving soluble mineral phases to form nanoscale pores. These microscopic pores provide "penetration channels" for the cement paste, allowing hydration products (such as CSH gel) to penetrate deep into the pores and form an "anchoring effect," reducing interfacial slippage. The surface of natural pebbles is mainly composed of inert Si-O-Si bonds. Alkali treatment can introduce active functional groups into the pebble surface through chemical reactions, resulting in a certain degree of hydroxylation. This hydroxylation forms hydrogen bonds or covalent bonds with the hydroxyl groups of cement hydration products (CSH gel, CH crystals), upgrading the interfacial bonding from "physical adsorption" to "chemical bonding." At the same time, the macroscopic grooves on the pebble surface can accommodate the local deformation of rubber particles (rubber elastic modulus 0.1~1 GPa). When subjected to load, the rubber particles embed into the grooves and undergo elastic deformation, dispersing the stress from "point contact" to "surface contact," reducing stress concentration and optimizing interfacial compatibility. This synergistically enhances the composite effect with the rubber particles. After hydroxylation, the polarity of the pebble surface is enhanced, significantly improving the wettability with rubber particles treated with anti-aging agents, thus increasing the interfacial bonding strength.

[0023] As a preferred embodiment, the crushing value of the crushed pebbles is no greater than 5%, and the apparent density of the rubber particles is 1.1~1.3 g / cm³. 3 The water absorption rate is no more than 3%.

[0024] Another object of the present invention is to provide a method for preparing a crushed pebble roadbed material, which includes the following steps:

[0025] (1) Grading and crushing of pebbles: Natural pebbles are crushed by a crusher and then screened to obtain crushed pebble particles with a particle size range of 0.1mm-3mm (including the 0.1mm end point, excluding the 3mm end point), 3mm-10mm (including the 3mm end point, excluding the 10mm end point), 10mm-20mm (including the 10mm end point, excluding the 20mm end point), and 20mm-35mm (including the 20mm end point, excluding the 35mm end point). The obtained crushed pebble particles are soaked and washed in 0.1M~1M sodium hydroxide solution for 0.5~3h, then taken out and rinsed repeatedly with deionized water until the particles are neutral. The obtained particles are placed in a drying oven and dried at 105±5℃ until the moisture content is ≤2%.

[0026] (2) Pretreatment of rubber particles: crush waste tires into particles with a particle size of 1~5mm, soak them in a 3wt%~5wt% anti-aging agent solution at room temperature for 1~5h, then filter them and dry them in a drying oven at 60±5℃ until constant weight, and set them aside for later use.

[0027] (3) Weigh out crushed pebble particles, cement, rubber particles, polycarboxylate superplasticizer and water according to the proportion. Mix the crushed pebble particles according to the proportion to obtain crushed pebbles. Mix the crushed pebbles and rubber particles and put them into a forced mixer and stir for 5-30 minutes until the two are evenly mixed to obtain material A. Mix the cement and superplasticizer and add water. Use a high-speed mixer at a speed of 1000~1500r / min to stir until a uniform paste is obtained to obtain material B.

[0028] (4) Mix material B with material A in a forced mixer and stir for 30-60 minutes until the mixture is uniform.

[0029] Preferably, the anti-aging agent is a composite system of 2,2,4-trimethyl-1,2-dihydroquinoline polymer and nano zinc oxide, wherein the mass ratio of 2,2,4-trimethyl-1,2-dihydroquinoline polymer to nano zinc oxide is 3:1, and the mass concentration of the solution used for impregnation is 3%~5%.

[0030] Preferably, the crusher is one of a jaw crusher, cone crusher, or impact crusher, and the screening includes dividing the crushed pebble particle size range into four grades. The applicant has found that when pebbles are crushed using a specific crusher, the content of needle-like and flaky particles after crushing is lower, which is beneficial for the uniform mixing of graded crushed stone and the improvement of the final material strength.

[0031] When the subgrade material is used for laying and filling subgrade, the mixture obtained in step (4) is spread in layers of a certain thickness, such as 20-30cm, and compacted 6-8 times with a vibratory roller at a frequency of 30-40Hz and an amplitude of 1.5-2.0mm to control the compaction degree ≥96%. Layered spreading and compaction can ensure the compaction quality of the subgrade, avoid insufficient compaction due to excessive thickness, and achieve the best compaction effect.

[0032] After compaction, cover with geotextile and water for 7 days. When the ambient temperature is below 5℃, take insulation measures such as covering with insulation blankets. The purpose of curing is to ensure that the cement materials are fully hydrated and solidified, thereby improving the strength and durability of the roadbed.

[0033] The crushed gravel roadbed material and preparation method of the present invention, through a four-stage gradation design of crushed gravel, sodium hydroxide pretreatment combined with anti-aging modification of rubber particles and optimization of raw material ratio, yields a roadbed material that exhibits excellent performance in terms of material properties, environmental benefits, and construction adaptability. The beneficial effects of the present invention include:

[0034] 1. This crushed gravel roadbed material and the roadbed obtained using it possess high strength and high density: The four-stage continuously graded crushed gravel forms a scientific "skeleton-filler" structure. The synergistic effect of particles in each size range achieves a dual improvement in density and strength from the macroscopic to the microscopic level. On the one hand, the continuous distribution of the four-stage particles increases the number of contact points between particles by more than 30%, reducing the possibility of particle slippage. On the other hand, the cementitious system formed by fine particles and cement paste fills the microscopic pores, making the overall structure of the material more compact. Coarse particles form a rigid skeleton, and their angular structure after crushing transfers loads and resists external deformation through mechanical interlocking. Medium and fine particles fill the gaps in the skeleton step by step, eliminating the large number of pores caused by the "bridging" phenomenon in traditional single-size gravel. Combined with the cementing effect, the compressive strength is greatly improved, far exceeding that of traditional gravel roadbeds. In terms of density, through gradation optimization, the material porosity can be controlled below 15%, and the compaction degree is ≥97%, providing a solid foundation for the long-term stability of the roadbed.

[0035] 2. The roadbed obtained using this material exhibits excellent water stability and frost resistance. Sodium hydroxide pretreatment to modify the pebble surface is key to improving water stability and frost resistance. Physically, alkaline corrosion creates nanoscale etching pits on the pebble surface, increasing surface roughness. These pits (50-100 nm deep) provide "anchoring points" for the cement slurry, and the synergistic effect increases interfacial shear strength by 40%-60% and reduces porosity in the interfacial transition zone, solving the problem of weak bonding between traditional pebbles and cement. The cement slurry can penetrate these microstructures to form mechanical locking, reducing the channels for water penetration. Chemically, the residual sodium silicate hydrolyzes to generate a large number of active hydroxyl groups (-OH), which form hydrogen bonds and covalent bonds (Si-O-Si) with the hydroxyl groups of cement hydration products (such as CSH gel), strengthening the interfacial bonding and reducing the porosity of the interfacial transition zone. In a 7-day immersion test, the strength loss is ≤4.5%. Regarding frost resistance, the rubber particles introduced into the material have an elastic buffering effect, absorbing the volume expansion stress generated by freeze-thaw cycles.

[0036] 3. Anti-aging modification of rubber particles can solve the durability problem of traditional rubber modified materials. This invention uses a composite anti-aging agent (mass ratio 3:1) of 2,2,4-trimethyl-1,2-dihydroquinoline polymer and nano zinc oxide to form a dual protection system of "chemical protection + physical shielding". 2,2,4-trimethyl-1,2-dihydroquinoline polymer, as a highly efficient antioxidant, can capture free radicals generated during rubber oxidation and inhibit chain reactions. Nano zinc oxide (particle size 50-100nm) has excellent ultraviolet shielding performance, with an absorption rate of ≥90% for ultraviolet rays in the 200-400nm wavelength band, reducing the breaking effect of ultraviolet rays on rubber molecular chains. Furthermore, alkali treatment enhances the polarity of the pebble surface, significantly improving the wettability with rubber particles treated with the anti-aging agent (TMQ containing polar amine groups and nano ZnO). The macroscopic grooves on the pebble surface form a size match with the 1-5mm rubber particles. After the rubber particles are embedded in the grooves, they can disperse stress through elastic deformation. The synergistic effect of both increases the interfacial bonding strength by 30%.

[0037] 4. In terms of environmental benefits, this material uses single-gravel crushed material, eliminating the need for additional sand and gravel fillers. This reduces sand and gravel mining by approximately 5,000 tons per kilometer of roadbed, lowering reliance on natural resources. Simultaneously, it utilizes 100% waste rubber granules, reducing "black pollution." Regarding construction adaptability, the material's mixing uniformity is significantly improved. Due to its rational four-stage gradation design and pre-treatment of the rubber granules (improved surface hydrophilicity), there is no significant segregation during mixing, shortening the mixing time compared to traditional materials. During paving, the material exhibits a good balance between fluidity and anti-segregation properties, achieving the designed compaction level using a conventional vibratory roller (frequency 30-40Hz), increasing construction efficiency by over 20%. Polycarboxylate superplasticizer (0.5-2 parts) can reduce the water demand of cement paste by 10%-15%. Its dispersing effect increases the paste spread by 20%, enabling uniform coating of four-graded pebbles (especially fine particles of 0.1-3mm). Simultaneously, the adsorption of the superplasticizer and cement hydration products promotes uniform deposition of CSH gel on the pebble surface, preventing localized weaknesses caused by uneven paste distribution. The synergistic effect of these two factors improves the uniformity of the mixture, ensuring a 28-day compressive strength standard deviation ≤0.3MPa and consistent overall material performance. Furthermore, the synergistic effect of single-source pebble and four-graded gradation provides a foundation for precise control of the four-graded gradation, as the mineral composition and hardness of the crushed products of single-source pebble are consistent. The four-graded gradation, through the synergy of "coarse skeleton - fine filler," maximizes the mechanical stability of single-source pebble. This synergy results in a material strength fluctuation range ≤3%, solving the performance fluctuation problem caused by the chaotic gradation of traditional multi-source pebble materials. Detailed Implementation

[0038] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the meaning consistent with their meaning in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless specifically defined as herein. The reagents used herein may be commercially available related products, and performance testing standards refer to industry or national standards.

[0040] Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in this specification means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. The term “and / or” as used herein includes all or any units and all combinations of one or more associated listed items.

[0041] Example 1

[0042] A type of crushed pebble roadbed material, by weight, is composed of the following raw materials:

[0043] 300 pieces of broken pebbles,

[0044] 100 parts of aluminate cement

[0045] 5 parts rubber granules

[0046] 0.5 parts of polycarboxylate superplasticizer,

[0047] 30 parts water;

[0048] The crushed pebble raw material is divided into four grades according to different particle size ranges, which are as follows by weight: 10 wt% for particles with a particle size range of [0.1mm-3mm], 20 wt% for particles with a particle size range of [3mm-10mm], 30 wt% for particles with a particle size range of [10mm-20mm], and 40 wt% for particles with a particle size range of [20mm-35mm]. The crushing value of the crushed pebbles is tested to be 5%, and the apparent density of the rubber particles is 1.1 g / cm³. 3 Water absorption rate: 3%.

[0049] Its preparation method includes the following steps:

[0050] (1) Grading and crushing of pebbles: Natural pebbles are crushed by a jaw crusher and screened. The corresponding crushed pebbles are weighed according to the raw material composition of the product and mixed to obtain crushed pebble particles. The obtained crushed pebble particles are soaked and washed in 0.1M sodium hydroxide solution for 3 hours. After that, they are taken out and rinsed with deionized water several times until the particles are neutral. The obtained particles are placed in a drying oven and dried at 105±5℃ until the moisture content is ≤2%.

[0051] (2) Pretreatment of rubber particles: Waste tires are crushed into particles with a particle size of 5 mm. They are then impregnated with a 3 wt% anti-aging agent (a composite system of 2,2,4-trimethyl-1,2-dihydroquinoline polymer and nano zinc oxide, wherein the mass ratio of 2,2,4-trimethyl-1,2-dihydroquinoline polymer to nano zinc oxide is 3:1). The impregnation solution has a mass concentration of 3% and is impregnated at room temperature for 5 h. After that, the particles are filtered and dried in a drying oven at 60±5℃ until constant weight, and then set aside for later use.

[0052] (3) Weigh out crushed pebble particles, cement, rubber particles, polycarboxylate superplasticizer and water according to the proportion. Mix the crushed pebble particles according to the proportion to obtain crushed pebbles. Mix the crushed pebbles and rubber particles and put them into a forced mixer and stir for 5 minutes until the two are evenly mixed to obtain material A. Mix the cement and superplasticizer and add water. Use a high-speed mixer at a speed of 1000 r / min to stir until a uniform paste is obtained to obtain material B.

[0053] (4) Mix material B with material A in a forced mixer and stir for 30 minutes until the mixture is uniform. The material was used to make roadbed. After normal paving, compaction and curing, the roadbed was tested. The test results showed that the 28-day compressive strength of the roadbed made of this material reached 5.2 MPa, the interfacial shear strength between gravel and cement was 3.8 MPa, the strength loss after 30 freeze-thaw cycles was 7.5%, the compaction degree was 97.5%, and the segregation rate was 2.8%.

[0054] Example 2

[0055] A type of crushed pebble roadbed material, by weight, is composed of the following raw materials:

[0056] 500 pieces of broken pebbles,

[0057] 100 parts of silicate cement

[0058] 10 parts rubber granules

[0059] 2 parts of polycarboxylate superplasticizer

[0060] 50 parts water;

[0061] The crushed pebble raw material is divided into four grades according to different particle size ranges, which are as follows by weight: 30 wt% for particles with a particle size range of [0.1mm-3mm], 20 wt% for particles with a particle size range of [3mm-10mm], 30 wt% for particles with a particle size range of [10mm-20mm], and 20 wt% for particles with a particle size range of [20mm-35mm]. The crushing value of the crushed pebbles is 4.5%, and the apparent density of the rubber particles is 1.3 g / cm³. 3 Water absorption rate: 2.7%.

[0062] Its preparation method includes the following steps:

[0063] (1) Grading and crushing of pebbles: Natural pebbles are crushed by a cone crusher and screened. The corresponding crushed pebbles are weighed according to the raw material composition of the product and mixed to obtain crushed pebble particles. The obtained crushed pebble particles are soaked and washed in 1M sodium hydroxide solution for 0.5h. After that, they are taken out and rinsed with deionized water several times until the particles are neutral. The obtained particles are placed in a drying oven and dried at 105±5℃ until the moisture content is 1.8%.

[0064] (2) Pretreatment of rubber particles: Waste tires are crushed into particles with a particle size of 1 mm. They are then impregnated with a 3 wt% anti-aging agent (a composite system of 2,2,4-trimethyl-1,2-dihydroquinoline polymer and nano zinc oxide, wherein the mass ratio of 2,2,4-trimethyl-1,2-dihydroquinoline polymer to nano zinc oxide is 3:1). The impregnation solution has a mass concentration of 5% and is impregnated at room temperature for 1 h. After that, the particles are filtered and placed in a drying oven at 60±5℃ to dry to constant weight for later use.

[0065] (3) Weigh out crushed pebble particles, cement, rubber particles, polycarboxylate superplasticizer and water according to the proportion. Mix the crushed pebble particles according to the proportion to obtain crushed pebbles. Mix the crushed pebbles and rubber particles and put them into a forced mixer and stir for 30 minutes until the two are evenly mixed to obtain material A. Mix the cement and superplasticizer and add water. Use a high-speed mixer at a speed of 1500 r / min to stir until a uniform paste is obtained to obtain material B.

[0066] (4) Mix material B with material A in a forced mixer and stir for 60 minutes until the mixture is uniform. The material was used to make roadbed. After normal paving, compaction and curing, the roadbed was tested. The test results showed that the 28-day compressive strength of the roadbed made of this material reached 7.5 MPa, the interfacial shear strength between gravel and cement was 3.6 MPa, the strength loss after 30 freeze-thaw cycles was 7.8%, the compaction degree was 97.2%, and the segregation rate was 2.5%.

[0067] Example 3

[0068] A type of crushed pebble roadbed material, by weight, is composed of the following raw materials:

[0069] 400 pieces of broken pebbles

[0070] 100 parts of sulfoaluminate cement

[0071] 8 parts rubber granules

[0072] 1 part of polycarboxylate superplasticizer

[0073] 40 parts water;

[0074] The crushed pebble raw material is divided into four grades according to different particle size ranges, which are as follows by weight: 15 wt% for particles with a particle size range of [0.1mm-3mm], 20 wt% for particles with a particle size range of [3mm-10mm], 30 wt% for particles with a particle size range of [10mm-20mm], and 35 wt% for particles with a particle size range of [20mm-35mm]. The crushing value of the crushed pebbles is 4.6%, and the apparent density of the rubber particles is 1.2 g / cm³. 3 Water absorption rate: 2.5%.

[0075] Its preparation method includes the following steps:

[0076] (1) Grading and crushing of pebbles: Natural pebbles are crushed by impact crusher and screened. The corresponding crushed pebbles are weighed according to the raw material composition of the product and mixed to obtain crushed pebble particles. The obtained crushed pebble particles are soaked and washed in 0.5M sodium hydroxide solution for 2 hours. Then they are taken out and rinsed with deionized water several times until the particles are neutral. The obtained particles are placed in drying oven and dried at 105±5℃ until the moisture content is 1.5%.

[0077] (2) Pretreatment of rubber particles: Waste tires are crushed into particles with a particle size of 3 mm. They are then impregnated with a 4 wt% anti-aging agent (a composite system of 2,2,4-trimethyl-1,2-dihydroquinoline polymer and nano zinc oxide, wherein the mass ratio of 2,2,4-trimethyl-1,2-dihydroquinoline polymer to nano zinc oxide is 3:1). The impregnation solution has a mass concentration of 5% and is used for impregnation at room temperature for 3 hours. After that, the particles are filtered and placed in a drying oven at 60±5℃ to dry to constant weight for later use.

[0078] (3) Weigh out crushed pebble particles, cement, rubber particles, polycarboxylate superplasticizer and water according to the proportion. Mix the crushed pebble particles according to the proportion to obtain crushed pebbles. Mix the crushed pebbles and rubber particles and put them into a forced mixer and stir for 15 minutes until the two are evenly mixed to obtain material A. Mix the cement and superplasticizer and add water. Use a high-speed mixer at a speed of 1200 r / min to stir until a uniform paste is obtained to obtain material B.

[0079] (4) Mix material B with material A in a forced mixer and stir for 45 minutes until the mixture is uniform. The material was used to make roadbed. After normal paving, compaction and curing, the roadbed was tested. The test results showed that the 28-day compressive strength of the roadbed made of this material reached 6.4 MPa, the interfacial shear strength between gravel and cement was 3.6 MPa, the strength loss after 30 freeze-thaw cycles was 7.8%, the compaction degree was 97.2%, and the segregation rate was 2.6%.

[0080] Comparative Example 1

[0081] A type of crushed pebble roadbed material is produced according to the scheme in Example 1, except that the crushed pebbles are not treated with an alkaline solution, that is, the pebbles are directly dried after crushing and screening, and the remaining steps are the same as in Example 1.

[0082] Test results showed that its 28-day compressive strength was 3.8 MPa, the shear strength at the gravel-cement interface was 2.2 MPa, the strength loss after 30 freeze-thaw cycles was 14.2%, the compaction degree was 95.0%, and the segregation rate was 3.5%.

[0083] Comparative Example 2

[0084] A crushed pebble roadbed material is prepared according to the scheme in Example 1, except that the crushed pebble particles are graded and distributed according to the following proportions: by weight, the particle size [0.1mm-3mm) accounts for 5wt%, [3mm-10mm) accounts for 10wt%, [10mm-20mm) accounts for 20wt%, and [20mm-35mm) accounts for 65wt%; the crushing value is 4.9%, and the remaining steps are the same as in Example 1.

[0085] Test results showed that its 28-day compressive strength was 3.2 MPa, the shear strength at the gravel-cement interface was 2.0 MPa, the strength loss after 30 freeze-thaw cycles was 18.5%, the compaction degree was 92.0%, and the segregation rate was 8.3%.

[0086] Comparative Example 3

[0087] A crushed pebble roadbed material is prepared according to the scheme in Example 1, except that the crushed 5mm rubber particles are not impregnated with an anti-aging agent, and the remaining steps are the same as in Example 1.

[0088] Test results showed that its 28-day compressive strength was 4.5 MPa, the shear strength at the pebble-cement interface was 3.7 MPa, the strength loss after 30 freeze-thaw cycles was 12.3%, the compaction degree was 97.1%, and the segregation rate was 2.7%. However, after 1000 hours of UV aging, its 28-day compressive strength dropped to 3.0 MPa, indicating a significant weakening of the material's anti-aging performance.

[0089] Comparative Example 4

[0090] A type of crushed pebble roadbed material is produced according to the scheme in Example 3, except that polycarboxylate superplasticizer is not used in the raw materials, and the other steps are the same as in Example 3.

[0091] Tests revealed that the material yielded a roadbed with a 28-day compressive strength of 4.1 MPa, an interfacial shear strength of 2.7 MPa between gravel and cement, a strength loss of 9.9% after 30 freeze-thaw cycles, a compaction degree of 95%, and a segregation rate of 7.6%.

[0092] The above provides a detailed description of a crushed pebble roadbed material and its preparation method. As can be seen from the examples and comparative examples, Examples 1-3 of this invention all meet the requirements of the patent application, exhibiting stable performance, with a 28-day compressive strength ≥5MPa and a compaction degree ≥97.0%, indicating that the material can maintain excellent performance within the range of raw material ratios and process parameters specified in the patent. In Comparative Example 1, the pebbles were not alkali-treated, resulting in weak interfacial bonding and a significant decrease in strength and freeze-thaw stability. In Comparative Example 2, the gradation was unreasonable, leading to reduced density and overall deterioration of various properties. In Comparative Example 3, the rubber particles were not anti-aging treated, resulting in increased freeze-thaw losses and poor long-term aging resistance, demonstrating the long-term value of anti-aging treatment. In Comparative Example 4, the lack of a water-reducing agent reduced mixing uniformity and lowered interfacial shear strength.

[0093] The preferred embodiments of the present invention have been described in detail above, and are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A crushed stone roadbed material, comprising, by weight, the following raw materials: 300-500 pieces of broken pebbles. 100 parts cement 5-10 parts rubber granules Water-reducing agent 0.5-2 parts, 30-50 parts water; The characteristic feature is that the crushed pebbles are the product of single-pebble crushing, and the crushing value of the crushed pebbles is not greater than 5%; The single pebble crushing product is divided into four grades according to different particle size ranges, and by weight, they are: 10wt%~30wt% for particles with a particle size range of [0.1mm-3mm), 20wt% for particles with a particle size range of [3mm-10mm), 30wt% for particles with a particle size range of [10mm-20mm), and 20wt%~40wt% for particles with a particle size range of [20mm-35mm]. The rubber particles are waste tire crushing particles impregnated with an anti-aging agent, with a particle size of 1~5mm. The anti-aging agent is a composite system of 2,2,4-trimethyl-1,2-dihydroquinoline polymer and nano zinc oxide, wherein the mass ratio of 2,2,4-trimethyl-1,2-dihydroquinoline polymer to nano zinc oxide is 3:

1. The cement is at least one of aluminate cement, silicate cement, and sulfoaluminate cement. The single pebble crushing product was pretreated by soaking and washing it in a 0.1M~1M sodium hydroxide solution for 0.5~3 hours, and then taking it out and rinsing it repeatedly with deionized water until the crushed pebble was neutral.

2. The gravel roadbed material according to claim 1, characterized in that, The single pebble crushing product is divided into four grades according to different particle size ranges, which are as follows by weight: 15wt% for particles with a particle size range of [0.1mm-3mm), 20wt% for particles with a particle size range of [3mm-10mm), 30wt% for particles with a particle size range of [10mm-20mm), and 35wt% for particles with a particle size range of [20mm-35mm].

3. The gravel roadbed material according to claim 1, characterized in that, The mass concentration of the anti-aging agent solution used for impregnation is 3% to 5%.

4. The gravel roadbed material according to claim 1, characterized in that, The water-reducing agent is a polycarboxylate water-reducing agent.

5. The gravel roadbed material according to claim 3, characterized in that, The apparent density of the rubber particles is 1.1~1.3 g / cm³. 3 The water absorption rate is no more than 3%.

6. A method for preparing the crushed cobblestone roadbed material as described in any one of claims 1 to 5, characterized in that, Includes the following steps: (1) Grading and crushing of pebbles: Natural pebbles are crushed by a crusher and then screened to obtain crushed pebble particles with particle sizes ranging from [0.1mm-3mm), [3mm-10mm), [10mm-20mm), and [20mm-35mm). The obtained crushed pebble particles are soaked and washed in 0.1M~1M sodium hydroxide solution for 0.5~3h, then taken out and rinsed repeatedly with deionized water until the particles are neutral. The obtained particles are placed in a drying oven and dried at 105±5℃ until the moisture content is ≤2%. (2) Pretreatment of rubber particles: crush waste tires into particles with a particle size of 1~5mm, soak them in a 3wt%~5wt% anti-aging agent solution at room temperature for 1~5h, then filter them and dry them in a drying oven at 60±5℃ until constant weight, and set them aside for later use. (3) Weigh out crushed pebble particles, cement, rubber particles, polycarboxylate superplasticizer and water according to the proportion. Mix the crushed pebble particles according to the proportion to obtain crushed pebbles. Mix the crushed pebbles and rubber particles and put them into a forced mixer and stir for 5-30 minutes until the two are evenly mixed to obtain material A. Mix the cement and superplasticizer and add water. Use a high-speed mixer at a speed of 1000~1500r / min to stir until a uniform paste is obtained to obtain material B. (4) Mix material B with material A in a forced mixer and stir for 30-60 minutes until the mixture is uniform.

7. The preparation method according to claim 6, characterized in that, The crushed pebbles are a single-pebble crushing product; by weight: 10wt%~30wt% for particles with a diameter range of [0.1mm-3mm), 20wt% for particles with a diameter range of [3mm-10mm), 30wt% for particles with a diameter range of [10mm-20mm), and 20wt%~40wt% for particles with a diameter range of [20mm-35mm); the anti-aging agent is a composite system of 2,2,4-trimethyl-1,2-dihydroquinoline polymer and nano zinc oxide, wherein the mass ratio of 2,2,4-trimethyl-1,2-dihydroquinoline polymer to nano zinc oxide is 3:1, and the mass concentration of the solution used for impregnation is 3%~5%.

8. The preparation method according to claim 6, characterized in that, The crusher is one of a jaw crusher, a cone crusher, or an impact crusher, and the screening includes screening the crushed pebble particles into four sizes.