Method for proportioning cement stabilized macadam base for winter

Abstract

The invention relates to the technical field of road engineering, and discloses a proportioning method of a cement stabilized macadam base for winter, the base comprises the following components by weight: 55-65% of coarse aggregate; 20 to 30 percent of fine aggregate; 4-7% of cement; 0.5-2% of an anti-freezing agent; water accounting for 8-12% of the total weight of the mixture; the active admixture comprises the following components in percentage by weight: 40-60% of fly ash, 10-20% of fly ash, 10-20% of fly ash and 5-8% of a binder; 10%-20% of silica fume; the coarse aggregate comprises the coarse aggregate with the particle size of 10-20 mm and accounts for 40-50% of the total weight of the coarse aggregate, and the fine aggregate with the particle size of 20-30 mm and accounts for 50-60% of the total weight of the coarse aggregate. By optimizing the distribution of the coarse and fine aggregates, the proportion of the active admixture, the use of the anti-freezing agent and mixing with hot water, the early strength of the base layer under the low-temperature condition is improved, the anti-freezing performance is enhanced, and the construction quality is optimized.

Description

Technical Field

[0001] The invention relates to the technical field of road engineering, in particular to a method for proportioning a cement-stabilized crushed stone base in winter. Background Art

[0002] The base structure in road construction is the core component of the entire roadbed project, and its performance directly determines the overall strength, durability and service life of the road surface. Especially in the cold northern regions, the winter construction environment faces severe challenges. The hydration reaction rate of the base material slows down significantly under low temperature conditions, and the early strength formation is limited, which can easily lead to delayed or non-condensation, seriously affecting the construction progress and quality.

[0003] In the existing technology, in order to improve the performance of cement-stabilized crushed stone base under low temperature conditions, some common methods have achieved phased results. For example, adding early strength agent can accelerate the hydration rate of cement and improve the early strength of the base in a short time; thermal insulation covering measures can create more favorable external conditions for the normal hardening of materials by reducing heat loss; at the same time, adjusting the water-cement ratio can reduce the free water content, thereby accelerating the hardening process. These methods have achieved a certain improvement in construction quality under specific conditions, but are more limited to emergency treatment of short-term problems.

[0004] However, the existing technology still has many shortcomings, especially in severely cold areas or extremely low temperature construction environments, it is difficult to fully meet the engineering needs; first, the use of early strength agents can easily lead to cracking of later materials and reduced durability of the base layer; simple physical insulation measures have limited effects under extremely low temperatures and cannot guarantee the hydration environment inside the material; although reducing the water-cement ratio accelerates hardening, the fluidity of the slurry decreases significantly, resulting in poor construction operability, base layer segregation or insufficient density; in addition, the existing technology pays little attention to the durability of the base layer under long-term freeze-thaw cycles, and the material's antifreeze performance is insufficient, which accelerates the damage process of the base layer. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a method for mixing cement-stabilized gravel base in winter, which solves the problems of insufficient early strength, poor freeze-thaw resistance, poor construction fluidity and poor uniformity of cement-stabilized gravel base in low-temperature construction environment in the prior art.

[0006] To achieve the above purpose, the present invention is implemented by the following technical scheme: a method for mixing cement-stabilized gravel base in winter, wherein the base comprises the following components in weight percentage: Coarse aggregate: 55-65%; Coarse aggregate is the main load-bearing part of the base, and its proportion design directly affects the mechanical properties and stability of the base. In a low-temperature environment, too much coarse aggregate will lead to too large aggregate gaps, insufficient slurry filling, and reduced material density; too little coarse aggregate will increase the slurry content and affect the freeze-thaw resistance of the base. By adjusting the proportion of coarse aggregate to 55-65%, while ensuring the stability of the skeleton structure, the void ratio is optimized, the filling effect of the cement slurry is enhanced, and the compressive strength is improved; Fine aggregate: 20~30%; The function of fine aggregate is to fill the pores between coarse aggregates and improve the density and fluidity of the mixture. An appropriate proportion of fine aggregate can improve the compressive strength and frost resistance of the base. In a low-temperature environment, a high proportion of fine aggregate will lead to an overly dense slurry, reducing construction operability; a low proportion will not effectively fill the voids, reducing the mechanical properties of the base. A fine aggregate proportion of 20-30% can improve both density and construction workability. Cement: 4-7%; Cement is the main component that provides early strength for the base. In low temperature environments, the hydration reaction rate of cement is significantly reduced, affecting the development of early strength. Increasing the upper limit of cement proportion to 7% can provide sufficient initial strength under severe cold conditions; and the addition amount of not less than 4% can avoid uneven slurry or insufficient bonding; Antifreeze: 0.5-2%; Antifreeze reduces the freezing point of the liquid phase in the slurry and the freezing of free water under low temperature conditions, thereby avoiding cracks in the material due to freezing expansion. At the same time, the inorganic salts in the antifreeze can promote the hydration reaction of cement in low temperature environments and improve the early strength. The upper limit of the dosage is set at 2%, which is suitable for extremely cold conditions (-10℃ and below), and the lower limit of 0.5% is suitable for general low temperatures (0~-5℃) to balance material performance and economy. Water: 8-12% of the total weight of the mixture; By controlling the water ratio to 8-12%, the cement hydration requirements can be met while preventing the slurry from being too thin and causing a decrease in strength. At the same time, using hot water at 30-40°C can increase the initial temperature of the mixture and accelerate the early hydration reaction; Active admixture: 5-8%, the active admixture includes the following components in percentage by weight: Fly ash: 40-60%; It has good pozzolanic reactivity and can react with calcium hydroxide in cement to generate CSH gel, which improves the later strength. At the same time, its particles have a lubricating effect and improve the fluidity of the mixture. Silica fume: 10-20%; With ultra-fine particles and high activity, it can improve the density and anti-freeze performance of the mixture; at the same time, it can fill the tiny pores in the slurry and reduce the damage to the base layer caused by freeze-thaw cycles; Mineral powder: 20-40%; Improve the toughness and crack resistance of the base layer, and improve the bonding strength between the cement paste and aggregate interface; Active admixtures can enhance the density and frost resistance of the mixture in low temperature environments, reduce cement consumption and improve economy.

[0007] Preferably, the coarse aggregate includes coarse aggregate with a particle size of 10 to 20 mm, accounting for 40 to 50% of the total weight of the coarse aggregate, and fine aggregate with a particle size of 20 to 30 mm, accounting for 50 to 60% of the total weight of the coarse aggregate; Medium-sized aggregates are used to fill the gaps between larger-sized aggregates to form a stable skeleton structure; thus, they can effectively fill the gaps between large-sized aggregates, reduce porosity, and increase the density of the mixture, thereby enhancing the bearing capacity and deformation resistance of the base layer; Aggregates with larger particle sizes constitute the main skeleton of the base layer, providing the main bearing capacity, which can bear and disperse the upper load, reduce stress concentration, and improve the overall strength and stability of the base layer.

[0008] Preferably, the antifreeze agent comprises the following components in weight percentage: 40-60% organic alcohol, 30-50% inorganic salt, and 3-5% surfactant; Organic alcohols change the structure of water molecules in the slurry and lower its freezing point, so that the slurry will not freeze completely even at temperatures below -10°C. In addition, organic alcohols can reduce the volume of ice crystals in the slurry, thereby avoiding material cracks caused by the frost heave effect. Inorganic salts release ions by dissolving, lowering the freezing point of the paste and enhancing the hydration reaction on the surface of cement particles. In particular, calcium chloride can effectively promote the early hydration reaction of cement and improve early strength; inorganic salts can also penetrate into the interface between aggregate and cement paste, improve bonding properties, and reduce internal stress under low temperature conditions; The main function of surfactants is to disperse cement particles and other admixture particles, reduce the viscosity of the slurry and improve its workability; in low temperature environments, surfactants can effectively reduce the surface tension of water in the slurry, enhance the dispersion ability of antifreeze components in the slurry, and enable the antifreeze to act more evenly on all parts of the mixture.

[0009] Preferably, the active admixture is a mixture of fly ash, silica ash and mineral powder, wherein the fly ash accounts for 40-60% of the weight of the admixture, the silica ash accounts for 10-20% of the weight of the admixture, and the mineral powder accounts for 20-40% of the weight of the admixture; Fly ash reacts with calcium hydroxide in cement hydration products through its pozzolanic reaction to form CSH gel (calcium silicate hydrate). This reaction not only reduces the excess calcium hydroxide in the slurry, but also improves the later strength of the mixture. The particle shape of fly ash is spherical, which can play a lubricating role and significantly improve the workability and fluidity of the mixture. This characteristic is particularly important in winter construction, which can improve the working performance of the slurry under low temperature conditions. Silica fume can fill tiny pores in the mixture due to its ultrafine particles, significantly improving the density and durability of the slurry. This effect is particularly evident in the improvement of freeze-thaw resistance; the active silicon dioxide rich in silica fume can react secondary with calcium hydroxide in the cement hydration process to generate more CSH gel, further improving the strength. The activity of silica fume is much higher than that of fly ash, so even if the dosage is small (5-8%), its effect is still very significant; Mineral powder reacts with hydration products in cement paste through its potential hydraulic hardness to generate products with gelling effect (such as CSH and calcium aluminate), thereby enhancing the strength and durability of the base layer; mineral powder can improve the toughness and crack resistance of the slurry, effectively alleviate the expansion of cracks caused by shrinkage or freeze-thaw in the base layer under low temperature conditions, and significantly improve the frost resistance of the base layer.

[0010] The present invention also provides a mixing method for cement-stabilized gravel base in winter, comprising the following steps: S1. Weigh coarse aggregate, fine aggregate, cement, active admixture, antifreeze agent and water, and mix them according to weight ratio; S2, mixing and dry-mixing the coarse aggregate and the fine aggregate to achieve uniform distribution of particles; S3, adding cement and active admixtures and stirring to evenly disperse the cement and admixtures; S4, adding antifreeze solution and water, wet mixing, to prepare a uniform slurry mixture; S5, spreading the mixture and compacting it to form a base; S6. After paving is completed, cover with tarpaulin to seal the surface moisture and carry out moisturizing maintenance.

[0011] Preferably, the proportioning by weight includes: The coarse aggregate is divided into two parts according to the particle size, the coarse aggregate with a particle size of 10 to 20 mm accounts for 40 to 50% of the total weight of the coarse aggregate, and the fine aggregate with a particle size of 20 to 30 mm accounts for 50 to 60% of the total weight of the coarse aggregate; This particle size distribution reduces the macropores in the aggregate skeleton, improves the filling effect of the slurry, reduces the permeability of the base layer and the risk of moisture damage caused by freeze-thaw cycles; Weigh the fine aggregate in proportion to ensure that it accounts for 20-30% of the volume of the mixture; When the fine aggregate ratio is 20-30%, it can ensure the density while avoiding excessive filling of the slurry, which can not only maintain the mechanical properties of the mixture but also improve the workability of construction. Too low a ratio will lead to excessively high porosity and reduce the density of the base; too high a ratio will increase the slurry content and affect the strength; Weigh cement by weight, the amount to be added is 4-7% of the total weight of the mixture; A cement content of 4-7% can meet the early strength requirements of winter construction. Insufficient cement content (less than 4%) will result in insufficient slurry bonding ability and insufficient strength; excessive cement content (more than 7%) will increase material costs and may lead to cracking risks due to excessive thickness of cement slurry. Weigh the active admixture by weight, accounting for 8-12% of the total weight of the mixture, the active admixture includes fly ash, silica ash and mineral powder, the fly ash accounts for 40-60% of the weight of the admixture, the silica ash accounts for 10-20% of the weight of the admixture, and the mineral powder accounts for 20-40% of the weight of the admixture; By distributing active admixtures (40-60% fly ash, 10-20% silica fume, 20-40% mineral powder), the slurry performance can be improved, which not only increases the mechanical strength, but also reduces the amount of cement and optimizes the material cost. The antifreeze agent is weighed at 0.5-2% of the total weight of the mixture; Antifreeze ensures the strength development of slurry in low temperature environment by lowering the freezing point of slurry, preventing ice crystal formation and promoting low temperature hydration reaction. Inorganic salts (such as calcium chloride) enhance hydration reaction by releasing ions, and organic alcohols (such as ethylene glycol) reduce the risk of frost heave by inhibiting ice crystal growth; Heat clean water to 30-40°C and weigh 8-12% of the optimum water content; During winter construction, the initial temperature of the mixture has a significant impact on the hydration reaction rate of cement. Water heated to 30-40°C can increase the overall temperature of the mixture, reduce the inhibitory effect of low temperature on the hydration reaction, and accelerate the early strength development.

[0012] Preferably, the mixing and dry-mixing of coarse aggregate and fine aggregate comprises: Put coarse aggregate and fine aggregate into the mixer according to the designed proportion; Putting coarse and fine aggregates into the mixer in proportion in advance can reduce the aggregate separation caused by weight difference, ensure the uniformity of subsequent mixtures and the consistency of construction quality, and at the same time reduce porosity and improve pavement strength and frost resistance. Set the dry mixing time to 20 to 30 seconds to achieve uniform distribution of particles; Through the dry mixing process, the arrangement of coarse and fine aggregates is optimized, the initial porosity of the mixture is reduced, the permeability and filling effect of the slurry in a low temperature environment are improved, and the freeze-thaw resistance is improved. Through the dry mixing process, the arrangement of coarse and fine aggregates is optimized, the initial porosity of the mixture is reduced, the permeability and filling effect of the slurry in a low temperature environment are improved, and the freeze-thaw resistance is improved. After dry mixing is completed, check whether there is any accumulation of lumps or stratification; By adjusting the mixing time, the dry mix effect can be optimized according to the specific aggregate characteristics to ensure uniform distribution of particles and form the best aggregate skeleton structure.

[0013] Preferably, the mixing of the materials comprises: Slowly add cement and active admixtures to the dry mixed coarse and fine aggregates; Cement is the main cementitious material. Its uniform distribution can ensure uniform hydration reaction, form a stable cementitious structure, and provide early and late strength for the base. Slowly adding cement can avoid local agglomeration caused by instantaneous concentrated input and ensure mixing uniformity; Set the mixing time to 50 to 60 seconds to ensure that the cement and active admixtures are fully mixed with the coarse and fine aggregates; After mixing is completed, observe the distribution of the mixture to ensure that there is no obvious concentration of admixtures; By adjusting the mixing time, it is possible to ensure that cement and active admixtures are mixed with coarse and fine aggregates, while constantly observing the uniformity of the mixture to avoid particle agglomeration or accumulation.

[0014] Preferably, the preparation of a uniform slurry mixture comprises: Evenly spray the antifreeze solution on the dry-mixed mixture; Function of antifreeze solution: Antifreeze reduces the freezing point of free water in the slurry to prevent water from freezing at low temperatures, while inhibiting the formation and expansion of ice crystals, reducing frost heave damage to the base layer; inorganic salts (such as calcium chloride) in antifreeze release ions to promote cement hydration reaction, and can still produce some hydration products (such as CSH gel and calcium aluminate) even in low temperature environments, thereby improving early strength; organic alcohols (such as ethylene glycol) further reduce the freezing point by destroying the hydrogen bond structure of water, and inhibit the growth of ice crystals in microscopic pores; The antifreeze solution is prepared by mixing antifreeze with water heated to 30-40° C., wherein the amount of antifreeze accounts for 0.5-2% of the total weight of the mixture; Using clean water heated to 30-40°C can increase the initial temperature of the mixture and avoid the rapid drop in the temperature of the slurry in a low temperature environment, thereby maintaining good construction performance; Add preheated water while spraying the antifreeze solution, and the wet mixing time is 80 to 90 seconds; Adding preheated water while spraying the antifreeze solution can effectively control the humidity of the mixture and avoid the decrease in slurry fluidity or segregation caused by adding too much water at one time; the simultaneous addition of antifreeze solution and preheated water can also improve the uniformity of the slurry and avoid the drying or unevenness of the mixture caused by insufficient local water content. The wet mixing time of 80 to 90 seconds is the time range optimized based on the particle size of the mixture and the slurry coating effect, thereby improving the fluidity and strength of the mixture; After mixing is completed, check the fluidity and uniformity of the mixture to ensure that the color is consistent and there is no obvious stratification. Inconsistent color of the mixture may reflect uneven distribution of antifreeze solution or cement, resulting in insufficient local strength or decreased antifreeze performance; stratification will destroy the density of the mixture, increase porosity, weaken the bearing capacity and durability of the base layer, and cracks are prone to occur especially during freeze-thaw cycles.

[0015] Preferably, the spreading and compacting of the mixture comprises: The mixture is spread in a layer thickness of 15 to 20 cm. Even spreading can avoid local uneven thickness, ensure uniform density after compaction, reduce the possibility of weak points or weak areas in the roadbed, and maintain the construction temperature of the mixture, thereby improving the reaction efficiency and compaction quality of the material.

[0016] Use rollers to compact the layers layer by layer, with the compaction density not less than 98% of the maximum dry density; Compaction is the process of using external force to make the aggregate particles in the mixture closely arranged and reduce the porosity. Layer-by-layer compaction can gradually reduce the voids and ensure that the base reaches the designed strength and stability; The compaction sequence is to compact gradually from the edge of the paving to the center, and the edge area should be compacted 1 to 2 times more; The edge area has a smaller contact area and uneven force, which may lead to lower compaction than the center area. Therefore, by increasing the number of rolling times by 1 to 2 times, the lack of compaction can be compensated to ensure the strength consistency of the entire paving layer; After compaction is completed, check whether there are loose areas or uncompacted areas, and recompact if necessary; The high porosity in loose areas will allow moisture to easily penetrate, forming expansion pressure during freeze-thaw cycles, destroying the base structure and significantly reducing durability. Timely inspection and pressure replenishment can ensure overall uniformity and density.

[0017] The present invention provides a method for mixing proportions of a cement-stabilized gravel base in winter. It has the following beneficial effects: 1. The present invention forms a reasonable skeleton structure by optimizing the particle size distribution and proportion design of coarse and fine aggregates, which significantly improves the compactness and bearing capacity of the mixture. Compared with the solution in the prior art where the single particle size of coarse aggregate leads to excessive porosity, the problem of insufficient slurry filling is effectively avoided. This technical solution also reduces the water intrusion during the freeze-thaw cycle and improves the freeze-thaw resistance of the base.

[0018] 2. The present invention proposes a technical solution of spraying heated water and antifreeze solution simultaneously under low temperature conditions, which solves the technical problems of slow hydration reaction and insufficient initial strength in traditional methods. Antifreeze lowers the freezing point and heated water raises the initial temperature, thus achieving rapid strength growth of the material under low temperature conditions. Compared with the existing solution of directly adding chemical early strength agents, it avoids the environmental burden and material cracking problems caused by chemical residues in the later stage.

[0019] 3. The present invention adopts a construction method of layer-by-layer paving and edge-strengthening compaction, which optimizes the uniformity and density during construction and improves the overall performance of the roadbed. Compared with the prior art of one-time thick-layer paving leading to uneven compaction, the focus on rolling the edge area eliminates weak points. This solution effectively improves the stability of the base under long-term load and dynamic load. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The figure is a flow chart of the method of the present invention. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the specification of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] Please see attached Figure 1 : Embodiment 1: Raw materials preparation: Weigh the coarse aggregate and fine aggregate in proportion. The coarse aggregate is divided into two parts, with the particle size of 10-20 mm accounting for 45% of the coarse aggregate weight and the particle size of 20-30 mm accounting for 55%. The fine aggregate is weighed by volume to account for 30% of the mixture.

[0023] The cement is weighed at 5% of the total weight of the mixture, the active admixture is 8% of the total weight of the mixture, the antifreeze is weighed at 1.2% of the total weight of the mixture, and the water is heated to 35℃ for use.

[0024] Mixing the mixture: First, put the coarse and fine aggregates into the mixer and dry mix for 25 seconds to check whether they are evenly distributed and without lumps.

[0025] Slowly add cement and active admixture and stir for 55 seconds. During this time, observe whether the particles are evenly covered with admixture to ensure that there is no local concentration.

[0026] Antifreeze solution (mixed with 35°C water and antifreeze) is evenly sprayed on the surface of the mixture. Preheated water is added and wet mixed for 85 seconds until the mixture has a uniform color and no stratification.

[0027] Paving and compaction: Spread the mixture in layers with a thickness of 15 cm, and compact it layer by layer from the edge to the center using a vibrating roller, with the density controlled to be no less than 98% of the maximum dry density. Roll the edge area once more to ensure there are no loose parts.

[0028] Maintenance: After paving, cover with tarpaulin to seal the surface moisture, keep it moist for 10 days, spray water twice a day in the morning and evening. Test the initial strength to ensure that it meets the design requirements.

[0029] Technical effect: By optimizing the particle size distribution and the synergistic effect of admixtures, the compactness and early strength of the base layer are improved. The antifreeze combined with heated water solves the problem of slow initial hydration reaction in low temperature environments.

[0030] Embodiment 2: Raw material ratio: The coarse aggregate size is 10-20mm, accounting for 40%, and the size is 20-30mm, accounting for 60%. The volume of fine aggregate accounts for 27% of the mixture. The cement content is 6% of the total weight of the mixture, and the active admixture accounts for 8% of the total weight of the mixture. The antifreeze is weighed at 2% of the total weight of the mixture, and the water is heated to 38℃ for use.

[0031] Mixing process: First, put the coarse and fine aggregates into the mixer and dry mix for 20 seconds to ensure that the particles are initially evenly distributed.

[0032] Slowly add cement and active admixtures to the dry material and mix for 60 seconds. After mixing, check the mixture to ensure that the admixtures are evenly covered on the aggregate surface and there is no lumps.

[0033] Add the antifreeze solution and 38℃ heated water to the mixture simultaneously and wet mix for 90 seconds. During this period, observe the fluidity of the slurry to ensure consistent color and uniform particle distribution.

[0034] Layer paving and compaction: The mixture is spread with a thickness of 18cm per layer and compacted layer by layer using a vibratory roller. The compaction density is controlled to be above 98% of the maximum dry density. The compaction sequence is from the edge to the center, and the edge area is rolled twice to ensure uniform density.

[0035] Winter specific maintenance: After paving, cover the surface of the base with composite geotextile, spray warm water every day, and maintain for 7 consecutive days. When the temperature is below -10℃, local heating measures are used to prevent freezing and cracking.

[0036] Technical effect: Suitable for rapid construction in extremely cold conditions. Layered paving and edge reinforcement compaction solve the problems of uneven compaction and loose edges in traditional thick layer construction.

[0037] Embodiment 3: Ratio design: Coarse aggregate is divided into 10-20mm (50%) and 20-30mm (50%) by weight. Fine aggregate accounts for 33% by volume. Cement content is 4.5%, and active admixture accounts for 12% of the total weight of the mixture. Antifreeze is weighed at 1% of the total weight of the mixture, and heated to 30℃ for standby use.

[0038] Mixing and stirring: Dry mix the coarse and fine aggregates for 30 seconds, and then add cement and active admixtures after even distribution. The mixing time is controlled within 55 seconds. Check the state of the mixture after mixing to ensure that the admixture is evenly coated on the surface of the particles without accumulation.

[0039] Spray the antifreeze solution evenly on the mixture, add hot water at the same time, and wet mix for 80 seconds until the mixture has uniform color, good fluidity and no stratification.

[0040] Paving and compaction: The mixture is spread at a thickness of 20 cm, compacted alternately by static and vibratory rollers, and the edge areas are rolled twice to ensure that the compaction density is ≥ 98%. Keep the surface flat during paving to avoid material segregation.

[0041] Maintenance measures: After paving is completed, cover with insulation film for maintenance and wet cure for 10 days. When the ambient temperature is below -5℃, heat and spray with warm water twice a day.

[0042] Technical effect: Through wet mixing and uniform spraying of antifreeze solution, the problems of segregation and insufficient fluidity of the mixture in low-temperature and humid environments were solved. Strengthening edge compaction significantly improved the antifreeze performance.

[0043] Embodiment 4: Material ratio: The coarse aggregate with a particle size of 10-20 mm accounts for 50% of the total weight of the coarse aggregate, and the particle size of 20-30 mm accounts for 50%. The fine aggregate accounts for 28% of the volume of the mixture. The cement content is 5.5%, and the active admixture accounts for 7% of the total weight. The antifreeze content is 1.5%, and the water is heated to 37℃ for standby use.

[0044] Mixing process: After dry mixing the coarse and fine aggregates for 25 seconds, slowly add cement and reactive admixtures and mix for 50 seconds to ensure even distribution of the admixtures.

[0045] Spray 37℃ antifreeze solution and add heated water, wet mix for 85 seconds, check the uniformity and fluidity of the mixture, the color should be consistent and there should be no stratification.

[0046] Paving and compaction: Spread the mixture in layers of 15 cm each, and compact it layer by layer with a vibratory roller, with a compaction density of ≥ 98%. The edge area needs to be rolled once more to check whether there are loose areas, and if necessary, recompact them.

[0047] Quick maintenance: After paving, cover with composite insulation film, sprinkle water twice a day, and maintain for 7 days. When the construction temperature is lower than -10℃, heating and covering measures are taken in some areas.

[0048] Technical effect: It optimizes the fluidity of the mixture in low temperature environment, ensures rapid strength formation, and solves the low temperature freezing cracking problem through efficient maintenance measures.

[0049] Comparative Example 1: Unoptimized coarse aggregate particle size distribution The proportion of coarse aggregate and fine aggregate is 60% and 40% respectively. The coarse aggregate is not graded by particle size and mixed aggregate with a particle size of 10 to 30 mm is directly used.

[0050] Weigh 5% of cement, 6% of active admixture and 1.2% of antifreeze in the total weight of the mixture, and heat water to 35°C for later use.

[0051] According to the mixing method in Example 1, the coarse and fine aggregates are first dry-mixed for 20 seconds, and cement and active admixtures are added and stirred for 55 seconds; the antifreeze solution and heated water are evenly sprayed and wet-mixed for 90 seconds until the mixture is uniform.

[0052] The mixture is spread to the designed area with a thickness of 15 cm, compacted layer by layer using a vibratory roller to a maximum dry density of 98%, and covered and cured for 7 days.

[0053] Comparative Example 2: No antifreeze was used According to the material proportions in Example 2, coarse aggregate with a particle size of 10-20 mm accounts for 40%, and 20-30 mm accounts for 60%; the volume of fine aggregate accounts for 27%; the cement content is 6% of the total weight of the mixture, and the active admixture accounts for 8%.

[0054] Do not add antifreeze, and use 35℃ heated water directly for standby use.

[0055] After dry mixing the coarse and fine aggregates for 20 seconds, add cement and active admixtures and stir for 60 seconds; gradually add heated water and wet mix for 80 seconds until the mixture is uniform.

[0056] Spread in layers up to 15cm, compact each layer with a vibrating roller to reach a maximum dry density of 98%, and cure for 7 days.

[0057] Comparative Example 3: Unoptimized active admixture ratio According to the material proportions of Example 3, the proportion of active admixtures is adjusted to 45% of the total weight of fly ash, 10% of silica fume, and 15% of mineral powder. The proportions of other materials remain the same: coarse aggregates with particle sizes of 10-20 mm and 20-30 mm respectively account for 50% of the total weight of coarse aggregates; fine aggregate accounts for 30% of the volume; cement content is 4.5%; antifreeze content is 1%; and hot water is heated to 30°C for standby use.

[0058] First, dry mix the coarse and fine aggregates for 30 seconds, then slowly add cement and adjusted active admixtures and stir for 50 seconds; then add antifreeze solution and heated water and wet mix for 85 seconds.

[0059] Spread the mixture in 20cm thickness and compact it layer by layer with a vibratory roller to a maximum dry density of 98%. Curing for 10 days.

[0060] Comparative Example 4: No heating water used Prepare the mixture according to the material proportions of Example 4: the coarse aggregate has a particle size of 10-20 mm accounting for 50%, and 20-30 mm accounting for 50%; the fine aggregate accounts for 28% of the volume of the mixture; the cement content is 5.5%; the active admixture accounts for 8%; the antifreeze content is 1.5%.

[0061] Use room temperature water (10°C) instead of heated water, and keep the rest of the stirring method the same.

[0062] After dry mixing the coarse and fine aggregates for 25 seconds, add cement and active admixtures and stir for 50 seconds; spray the antifreeze solution and add room temperature water, wet mix for 85 seconds and mix evenly.

[0063] Spread in 15cm layers, compact each layer with a vibratory roller to a maximum dry density of 98%, and cover and cure for 7 days.

[0064] Comparative Example 5: Paving thickness is too thick The material ratio is exactly the same as that of Example 2: coarse aggregate with a particle size of 10-20 mm accounts for 40%, and 20-30 mm accounts for 60%; fine aggregate volume accounts for 27%; cement content is 6%; active admixture accounts for 8%; antifreeze content is 2%; and heating water is set at 38°C for standby use.

[0065] After dry mixing the coarse and fine aggregates for 20 seconds, add cement and active admixtures and stir for 60 seconds; spray the antifreeze solution and add heated water, wet mix for 90 seconds until the color is uniform.

[0066] Spread the mixture at a thickness of 30cm at one time, compact it layer by layer with a vibrating roller until the compaction density reaches 98% of the maximum dry density, and cure for 7 days.

[0067] Experiment 1: Compressive strength test Experimental Description Purpose The optimized cement-stabilized crushed stone base mix ratio method of the present invention is verified to improve the compressive strength under low temperature environment, especially the effect of optimizing the coarse aggregate particle size distribution and the active admixture ratio.

[0068] Experimental procedures Ingredients preparation: A mixture was prepared according to the proportions of Example 1, Example 3, Comparative Example 1 and Comparative Example 3.

[0069] For Example 1 and Comparative Example 1, the particle size distribution of the coarse aggregate was adjusted (Example 1 was classified by particle size, while Comparative Example 1 was not classified).

[0070] For Example 3 and Comparative Example 3, the ratio of active admixtures was adjusted (Example 3 adopted a reasonable ratio, while Comparative Example 3 contained less fly ash and more mineral powder).

[0071] Mixing process: Dry mix the coarse and fine aggregates for 20 to 30 seconds, add cement and active admixtures and continue mixing for 50 to 60 seconds.

[0072] Add antifreeze solution (or clean water) and wet mix for 80 to 90 seconds until the color is uniform and there is no stratification.

[0073] Forming and maintenance: The mixture was spread to a thickness of 15 cm and compacted by vibration to 98% of the maximum dry density.

[0074] Wet curing for 7 days at -10℃ to ensure the performance development of the material under low temperature conditions.

[0075] Compressive strength test: Take three standard test pieces of 100mm×100mm×100mm (diameter 150mmx height 150mm) from each group of paving base.

[0076] The compression tester was used to load the specimen step by step and the compressive strength of each specimen was recorded.

[0077] Compressive strength test data of different embodiments and comparative examples The optimized coarse aggregate particle size distribution significantly improves the overall performance of the mixture. In Example 1, the coarse aggregate is divided into two particle sizes of 10-20 mm and 20-30 mm, and is strictly distributed in proportion. The test results show that this design significantly reduces the porosity inside the base layer, allowing the slurry to fill the voids more evenly and form a tighter skeleton structure. In contrast, the unclassified coarse aggregate in Comparative Example 1 cannot effectively fill the voids, resulting in high local porosity and significantly reduced early strength; the optimization of the proportion of active admixtures is also crucial for strength development. In Example 3, fly ash, silica fume and mineral powder are reasonably distributed, and the three work together to generate more CSH gel and calcium aluminate reaction products, enhancing the interfacial bonding between cement and aggregate. In Comparative Example 3, the proportion of fly ash is low and the proportion of mineral powder is high, resulting in a decrease in material fluidity, the slurry cannot effectively cover the aggregate, and the final strength performance is significantly lagging behind. It can be seen that the balanced design of the proportion of active admixtures directly affects the performance of the base layer.

[0078] Experiment 2: Freeze-thaw resistance test Experimental Description Purpose The freeze-thaw cycle test verifies the anti-freeze-thaw performance advantage of the present invention under low temperature conditions, especially the effect of optimizing the use of antifreeze agents and the effect of heating water on the durability of the base layer.

[0079] Experimental procedures Ingredients preparation: A mixture was prepared according to the proportions of Example 2, Example 4, Comparative Example 2 and Comparative Example 4.

[0080] Example 2 and Comparative Example 2 compare the effects of antifreeze, and Example 4 and Comparative Example 4 compare the effects of heated water and room temperature water.

[0081] Specimen forming: The mixture was spread in layers with a thickness of 15 cm and compacted by vibration to 98% of the maximum dry density.

[0082] Three standard specimens of 100 mm × 100 mm × 100 mm were prepared in each group and placed in a -10°C environment for wet curing for 7 days after molding.

[0083] Freeze-thaw cycle test: The cured specimens were placed in a -10°C freezer for 4 hours and then moved to 20°C water to thaw for 4 hours to complete one freeze-thaw cycle.

[0084] Each group of specimens repeated 20 freeze-thaw cycles, and the compressive strength and mass changes of the specimens were recorded before and after the test.

[0085] Performance Testing: After the freeze-thaw cycle, the compressive strength of the specimens was measured and the strength retention rate was calculated (strength retention rate = strength after freeze-thaw / initial strength × 100%).

[0086] Record the weight loss rate of the specimen and calculate the durability of the specimen.

[0087] Freeze-thaw resistance test data of different embodiments and comparative examples The use of antifreeze plays a decisive role in improving the freeze-thaw resistance in low-temperature environments. In Example 2, by adding a composite antifreeze, the freezing point in the specimen was significantly lowered, and the formation of internal ice crystals was inhibited. The results show that the specimen maintained a higher strength retention rate after the freeze-thaw cycle, indicating that the bonding properties of the slurry were not significantly damaged. In contrast, in Example 2, where no antifreeze was used, the pores expanded significantly after freeze-thaw, resulting in structural spalling and rapid strength decay. This shows that the role of the antifreeze is not only to lower the freezing point, but also to improve the slurry's ability to resist freeze cracking; The use of heated water effectively improves the frost resistance and durability of the material under low temperature conditions. In Example 4, the heated water preheated to 30-40°C increases the initial temperature of the mixture, allowing the cement hydration reaction to proceed more fully. Even after freeze-thaw cycles, the adhesion inside the slurry is more stable. However, the specimens using room temperature water in Comparative Example 4 have a low initial hydration rate, resulting in poor structural density in the later stage, and a significant increase in weight loss rate after freeze-thaw, indicating that the migration and expansion of water in the pores destroys the structural integrity.

[0088] Experiment 3: Construction adaptability test Experimental Description Purpose The construction adaptability of the present invention under low temperature conditions was verified, with emphasis on the effects of paving thickness, compaction technology and heating water on construction performance, and the effects of process optimization and parameter adjustment on the construction quality of the mixture were compared.

[0089] Experimental procedures Ingredients preparation: A mixture was prepared according to the proportions of Example 2, Example 4, Comparative Example 2 and Comparative Example 5.

[0090] Example 2 and Comparative Example 5 compare the construction performance of paving thickness (15 cm and 30 cm), and Example 4 and Comparative Example 2 compare the effects of heated water and room temperature water on the fluidity and uniformity of the mixture.

[0091] Paving and compaction: A paving simulation experiment was carried out in an environment of -5°C. Example 2 and Comparative Example 5 were paved at a thickness of 15 cm and 30 cm respectively at one time; Example 4 and Comparative Example 2 were paved at a thickness of 15 cm.

[0092] Use a vibratory roller to compact each layer, and add 1 to 2 more rollings in the edge areas to ensure that the designed compaction density is 98% of the maximum dry density.

[0093] Quality Inspection: Compaction density test: Use the sand filling method to randomly select three areas after compaction, measure the density, and compare the construction uniformity.

[0094] Edge stability test: Visually inspect the paving edge area and record the degree of looseness.

[0095] Construction fluidity: Construction adaptability is assessed by observing material fluidity, stratification and smooth construction during the paving process.

[0096] Construction adaptability test data of different embodiments and comparative examples The influence of paving thickness on construction quality is obvious. In Example 2, a layered paving method is adopted, and the thickness of each layer is 15 cm. The mixture can be fully compacted, and the compaction density is stably above 98%, and the looseness of the edge area is significantly reduced. In contrast, in Example 5, 30 cm is paved at one time. During the compaction process, it is difficult to achieve effective compaction of the bottom material, resulting in insufficient local density, especially in the edge area. It is more likely to have obvious looseness and segregation. This phenomenon directly reduces the construction uniformity and the bearing capacity of the roadbed; The use of heated water effectively improves the construction fluidity of the mixture in a low temperature environment. Example 4 uses heated water at 30-40°C to significantly increase the initial temperature of the material, so that the slurry maintains good fluidity during the paving process. During the construction process, the mixture shows strong uniformity in a low temperature environment, and the paving is smooth and without stratification. However, Comparative Example 2 was prepared using normal temperature water, and the slurry fluidity was obviously insufficient. Local dry material accumulation and stratification occurred during the construction process, resulting in large fluctuations in the density after compaction and increasing the difficulty of construction.

[0097] Experiment 4: Early Strength Growth Test Experimental Description Purpose The effects of the optimized antifreeze use and heated water preparation technology of the present invention on early strength growth in low temperature environments were tested, and the performance of the material in 7-day and 14-day strength development was verified, especially comparing the use of antifreeze and the effects of heated water and room temperature water.

[0098] Experimental procedures Raw material preparation: A mixture was prepared according to the proportions of Example 2, Example 4, Comparative Example 2 and Comparative Example 4.

[0099] Example 2 and Comparative Example 2 compare the effect of the antifreeze agent, and Example 4 and Comparative Example 4 compare the difference between heated water and water at room temperature.

[0100] Specimen forming: The mixture was spread in a thickness of 15 cm and compacted in layers to 98% of the maximum dry density.

[0101] Three standard specimens of 100mm×100mm×100mm were prepared in each group and wet-cured at -10℃ after molding.

[0102] Compressive strength test: Samples were taken from each group at 7 and 14 days for compressive strength testing.

[0103] Use a standard compression testing machine to gradually load the specimens, record their compressive strength, and measure the strength growth at different curing times. Early strength growth test data of different embodiments and comparative examples Time (day) Example 2 (MPa) Comparative Example 2 (MPa) Example 4 (MPa) Comparative Example 4 (MPa) 7 7.5 5.2 7.8 5.6 14 9.6 6.8 10.2 7.2 7 7.7 5.5 8 5.4 14 9.8 7 10 7.5 7 7.4 5.3 7.9 5.7 14 9.7 6.9 10.1 7.1 Average 7 days 7.53 5.33 7.9 5.57 Average 14 days 9.7 6.9 10.1 7.27 The use of antifreeze significantly accelerates the early strength growth in low temperature environments. In Example 2, the composite antifreeze improves the early hydration reaction conditions of cement particles by lowering the freezing point of the mixture. The results show that the strength at 7 days is about 40% higher than that of Comparative Example 2, and the difference is still significant at 14 days. This effect is not only due to the early strength effect of the antifreeze, but also to its ability to inhibit the damage of freeze-thaw stress to the slurry structure. In Comparative Example 2, there is no antifreeze, and the hydration reaction of the cement particles is almost completely inhibited by the low temperature at 7 days, resulting in slow strength development; The use of heated water optimizes the initial hydration reaction rate and directly affects the early strength of the material. In Example 4, the heated water at 30-40°C maintains a higher initial temperature of the slurry under low temperature conditions, effectively improving the early hydration degree of cement. In contrast, in Comparative Example 4, room temperature water is used, and the initial temperature of the mixture is low, resulting in the inability of cement particles to fully hydrate, and the bonding properties of the slurry are greatly reduced, which is manifested in that the 7-day and 14-day strengths are both lower than those of Example 4.

[0104] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A cement-stabilized gravel base for winter, characterized in that: The base layer includes the following components in weight percentage: Coarse aggregate: 55-65%; Fine aggregate: 20~30%; Cement: 4-7%; Antifreeze: 0.5-2%; Water: 8-12% of the total weight of the mixture; Active admixture: 5-8%, the active admixture includes the following components in percentage by weight: Fly ash: 40-60%; Silica fume: 10-20%; Mineral powder: 20-40%.

2. The cement-stabilized gravel base for winter use according to claim 1, characterized in that: The coarse aggregate includes coarse aggregate with a particle size of 10 to 20 mm, accounting for 40 to 50% of the total weight of the coarse aggregate, and fine aggregate with a particle size of 20 to 30 mm, accounting for 50 to 60% of the total weight of the coarse aggregate.

3. The cement-stabilized gravel base for winter use according to claim 1, characterized in that: The antifreeze agent comprises the following components in weight percentage: 40-60% of organic alcohol, 30-50% of inorganic salt and 3-5% of surfactant.

4. The cement-stabilized gravel base for winter use according to claim 1, characterized in that: The active admixture is a mixture of fly ash, silica ash and mineral powder, wherein the fly ash accounts for 40-60% of the weight of the admixture, the silica ash accounts for 10-20% of the weight of the admixture, and the mineral powder accounts for 20-40% of the weight of the admixture.

5. A method for mixing cement-stabilized gravel base in winter, characterized in that: Using the cement-stabilized gravel base for winter according to any one of claims 1 to 4 comprises the following steps: Weigh coarse aggregate, fine aggregate, cement, active admixture, antifreeze agent and water and mix them according to weight ratio; Mixing and dry mixing of coarse and fine aggregates is used to achieve uniform distribution of particles; Add cement and active admixtures and stir to evenly disperse cement and admixtures; Add antifreeze solution and water, wet mix, to prepare a uniform slurry mixture; Spread the mixture and compact it to form the base; After paving is completed, cover with a tarpaulin to seal the surface moisture and carry out moisturizing maintenance.

6. A mixing method for cement-stabilized gravel base in winter according to claim 5, characterized in that: The proportioning by weight includes: The coarse aggregate is divided into two parts according to the particle size. The coarse aggregate with a particle size of 10-20 mm accounts for 40-50% of the total weight of the coarse aggregate, and the fine aggregate with a particle size of 20-30 mm accounts for 50-60% of the total weight of the coarse aggregate. Weigh the fine aggregate in proportion to ensure that it accounts for 20-30% of the volume of the mixture; Weigh cement by weight, the amount is 4-7% of the total weight of the mixture; Weigh the active admixture by weight, accounting for 8-12% of the total weight of the mixture. The active admixture includes fly ash, silica ash and mineral powder, with fly ash accounting for 40-60% of the weight of the admixture, silica ash accounting for 10-20% of the weight of the admixture, and mineral powder accounting for 20-40% of the weight of the admixture; The antifreeze agent is weighed at 0.5-2% of the total weight of the mixture; Heat the clean water to 30-40°C and weigh 8-12% of the optimum moisture content.

7. A mixing method for cement-stabilized gravel base in winter according to claim 5, characterized in that: The mixing and dry mixing of coarse aggregate and fine aggregate comprises: Put coarse aggregate and fine aggregate into the mixer according to the designed proportion; Set the dry mixing time to 20 to 30 seconds to achieve uniform distribution of particles; After dry mixing is completed, check whether there are any lumps or stratification.

8. The mixing method of cement-stabilized gravel base in winter according to claim 5, characterized in that: The mixing of the materials comprises: Slowly add cement and active admixtures to the dry mixed coarse and fine aggregates; Set the mixing time to 50 to 60 seconds to ensure that the cement and active admixtures are fully mixed with the coarse and fine aggregates; After mixing is completed, observe the distribution of the mixture to ensure that there is no obvious concentration of admixtures.

9. The mixing method of cement-stabilized gravel base in winter according to claim 5, characterized in that: The method of preparing a uniform slurry mixture comprises: Evenly spray the antifreeze solution on the dry-mixed mixture; The antifreeze solution is prepared by mixing antifreeze with water heated to 30-40°C, wherein the amount of antifreeze accounts for 0.5-2% of the total weight of the mixture; Add preheated water while spraying the antifreeze solution, and the wet mixing time is 80 to 90 seconds; After mixing is complete, check the fluidity and uniformity of the mixture to ensure that the color is consistent and there is no obvious stratification.

10. A mixing method for cement-stabilized gravel base in winter according to claim 5, characterized in that: The paving mixture and compacting comprises: Spread the mixture in layers of 15 to 20 cm thick; Use a roller to compact the layers layer by layer, and the compaction density should not be less than 98% of the maximum dry density; The compaction sequence is to compact gradually from the edge of the paving to the center, and the edge area should be compacted 1 to 2 times more; After compaction is complete, check for loose or uncompacted areas and recompact if necessary.

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