Synergistic preparation method of all-solid waste road base material containing mountain flour and recycled coarse aggregate

Abstract

The invention discloses a synergistic preparation method of an all-solid waste road base material containing stone powder and recycled coarse aggregate, and belongs to the technical field of road engineering and solid waste recycling. The method comprises the following steps: taking recycled coarse aggregate, recycled fine aggregate and stone powder as cores, matching with steel slag, fly ash and desulfurized gypsum to construct an all-solid-waste system, carrying out optimization pretreatment on the raw materials, mixing 65-78 parts of recycled coarse aggregate, 20-28 parts of recycled fine aggregate, 12-18 parts of stone powder, 12-19 parts of steel slag, 7-14 parts of fly ash, 4-7 parts of desulfurized gypsum and 2.5-4.5 parts of an exciting agent, and uniformly stirring to obtain a mixture; and finally, carrying out natural curing in a standard curing box to obtain the road base material. 100% solid waste utilization is achieved, the 28d unconfined compressive strength of the material is larger than or equal to 5.2 MPa, carbon emission is reduced by 60% or above, large-scale equipment is not needed, the material is suitable for road bases in multi-climate areas, and environmental protection and engineering performance are both considered.

Description

Technical Field

[0001] This invention belongs to the field of road engineering materials and solid waste resource utilization technology, specifically relating to a method for the synergistic preparation of all-solid-waste road base material containing stone powder and recycled coarse aggregate. Background Technology

[0002] Traditional road base materials rely on natural sand and gravel resources, with my country consuming over 1 billion tons annually, leading to over-exploitation of natural mineral veins and exacerbating ecological damage. At the same time, the cumulative stockpiled solid waste from the construction sector, including waste concrete (including recycled aggregate raw materials) and stone powder from stone processing, as well as steel slag, fly ash, and desulfurization gypsum from the industrial sector, exceeds 10 billion tons. This not only occupies land resources but also poses environmental risks such as heavy metal leakage and dust pollution.

[0003] In existing technologies, the application of solid waste in road base courses faces the following problems: First, recycled coarse aggregates have low strength and high shrinkage due to the adhesion of old mortar to their surface; second, stone powder alone is prone to causing cracking in the base course and needs to be mixed with cement and other cementing materials, failing to achieve full utilization of solid waste; third, the synergistic effect is poor when multiple solid wastes are mixed, resulting in unstable material performance; and fourth, the preparation process is complex, requiring high-temperature curing or large amounts of cement, which does not meet low-carbon requirements. Therefore, developing a road base course material preparation method that incorporates all solid wastes, provides synergistic reinforcement, and has a simple process is of great significance. Summary of the Invention

[0004] This invention aims to overcome the triple defects of existing solid waste-based road base materials, namely "low solid waste utilization rate, insufficient mechanical properties, and dependence on cement / high temperature curing". It provides a method for the synergistic preparation of all-solid waste road base materials containing stone powder and recycled coarse aggregate. By optimizing the solid waste pretreatment process, adjusting the material ratio, and strengthening the synergistic effect of components, the material performance is stably improved under high solid waste content. Moreover, the performance can be verified through laboratory-scale testing, meeting the requirements for use in heavy traffic road bases.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows; A method for co-preparing a solid waste road base material containing stone powder and recycled coarse aggregate includes the following steps: 1. Solid waste pretreatment: (1) Recycled coarse aggregate: After the waste concrete is crushed by jaw crusher and impact shaping, it is separated into continuous graded particles with a particle size of 5-31.5mm by a three-layer screening equipment (pore size 31.5mm, 16mm, 5mm). After manually removing impurities (such as steel bars and wood chips), it is subjected to water-saturated surface drying treatment (soaking for 24 hours and then draining for 12 hours) to control the moisture content to 5-7%, crushing value ≤18%, needle-like and flaky particle content ≤14%, and apparent density ≥2350kg / m³. 3 ; (2) Stone powder: Waste stone powder from building stone processing is first dried in a 105-110℃ blower dryer until the moisture content is ≤1.5%, then pulverized by an ultrafine ball mill (grinding time 30min), and passed through a 0.15mm standard sieve. The residue is controlled to be ≤4% by negative pressure sieving method. The SiO2 content is ≥68% as detected by X-ray fluorescence spectroscopy, and the plasticity index is ≤11 as tested by liquid limit and plastic limit combined tester. (3) Auxiliary solid waste: Steel slag is treated with a permanent magnet drum magnetic separator to remove iron (iron recovery rate ≥95%), and then crushed to a particle size ≤4.5mm by an impact crusher. The free calcium oxide content is determined by EDTA titration to be ≤2.8%. The fly ash used is industrial fly ash of grade II or above, dried at 100-105℃ to a moisture content of ≤0.8%, and the loss on ignition is controlled to be ≤7% by the burning method, with a water requirement ratio of ≤105%. (4) Recycled fine aggregate: After crushing and screening waste concrete, particles with a diameter of 0.075-4.75mm are separated. The particles are then surface-dried to a moisture content of 5-6%, a crushing value of ≤23%, a mud content (washed) of ≤2.9%, and an apparent density of ≥2230kg / m³. 3 The content of needle-like and flaky particles is ≤19%; (5) Desulfurized gypsum: Industrial desulfurized gypsum is dried at 80-85℃ to a moisture content of ≤2%, and then crushed and passed through a 2.36mm sieve to ensure that there are no lumpy particles.

[0006] 2. Raw material ratio (by weight): (1) Skeleton system: 65-78 parts of recycled coarse aggregate (provides structural support, and continuous gradation ensures density), 20-28 parts of recycled fine aggregate (fills the gaps between coarse aggregate), and 12-18 parts of stone powder (ultrafine particles fill micropores and participate in the cementation reaction after activation). (2) Cementing system: 12-19 parts steel slag (provides potential cementing activity and improves later strength), 7-14 parts fly ash (improves the workability of the mixture and reduces the heat of hydration), and 4-7 parts desulfurized gypsum (adjusts the setting time and generates ettringite to enhance the interface). (3) Activation system: The activator is solid sodium silicate, with a modulus of 2.1-2.4 as tested by the specific gravity bottle method, and the fineness is controlled to have a sieve residue of ≤9% on 0.08mm sieve, with an addition amount of 2.5-4.5 parts; (4) Synergistic mechanism: Stone powder reduces the gap ratio of recycled aggregate (from 22% to below 15%) through the "micro-filling effect". Steel slag and fly ash generate CSH gel, CASH gel and ettringite under the activation of solid sodium silicate, which synergistically form a multi-component cementitious system with desulfurized gypsum. Recycled coarse aggregate constructs a rigid skeleton. The three together achieve the synergistic enhancement effect of "dense filling-strong bonding-stable skeleton" and improve the overall mechanical properties of the material.

[0007] 3. Co-mixing: First, dry-mix the mixture using a forced mixer for 1.2-1.8 minutes (mixing speed 300 r / min) to ensure that the solid particles are evenly dispersed and there are no local lumps; then add 8.5-11.5% of the total mass of tap water (water temperature 20-25℃) to the mixture and continue wet mixing for 3.5-4.5 minutes (mixing speed 250 r / min). Use a Vicat apparatus to test the consistency of the mixture and control it at 12-18 mm to meet the laboratory requirements for paving and molding workability (slump ≤ 5 mm).

[0008] 4. Compaction molding (laboratory pilot-scale process): The mixture was placed in two layers into a laboratory mold (150mm×150mm×150mm), with each layer 50-70mm thick. A small vibratory compactor (5-8kN excitation force, 30-50Hz vibration frequency) was used for compaction. The compaction process was as follows: first, two light compactions (5kN excitation force, 10mm / s compaction speed); then four to five heavy compactions (7-8kN excitation force, 8mm / s compaction speed); and finally, one light compaction for finishing (5kN excitation force, 10mm / s compaction speed). The surface moisture content of the mixture was monitored in real time using a rapid moisture content meter. If the moisture content was 1% lower than the optimum moisture content, a micro-sprayer was used to supplement water, maintaining the moisture content fluctuation within ±0.8% of the optimum moisture content. The final compaction degree (tested using the sand cone method, adapted to the mold size) was ≥96.5%.

[0009] 5. Collaborative maintenance: Within 1 hour of compaction, the test block should be placed in a standard curing chamber (temperature 20±2℃, relative humidity ≥95%) for curing. For the first 7 days, maintain stable humidity within the curing chamber and record temperature and humidity data daily. After 7 days, transfer to a natural curing environment (temperature 16-34℃, relative humidity ≥80%) for continued curing until 28 days. If the natural curing environment temperature is below 15℃, wrap the outside of the test block with a 0.12mm thick polyethylene plastic film for insulation. Monitor the surface temperature of the test block using a temperature sensor to ensure the curing environment temperature does not fall below 11℃.

[0010] Compared with the prior art, the present invention has the following beneficial effects: 1. High-value utilization of all solid waste: 100% of the raw materials are recycled coarse aggregate, recycled fine aggregate, stone powder, steel slag, fly ash, desulfurization gypsum, and other solid wastes. Each ton of material can absorb 1.3-1.6 tons of solid waste, 100% replacing natural sand and gravel (saving 1.8 tons of natural sand and gravel per ton of material), and reducing the land occupied by solid waste storage by 0.6-0.9m². 2 / ton, reducing solid waste treatment costs by 30-40 yuan / ton, achieving a dual improvement in solid waste resource utilization rate and economic benefits.

[0011] 2. Synergistic enhancement of mechanical properties: Through the synergistic mechanism of "filler-bonding-skeleton", laboratory small-scale tests have verified that the material has an unconfined compressive strength of ≥3.6MPa at 7d, ≥5.2MPa at 28d, a splitting strength of ≥0.55MPa, a resilient modulus of ≥1550MPa, a drying shrinkage rate (28d) of ≤0.07%, and a freeze-thaw resistance (25 cycles at -15℃ to 20℃) with a strength loss of ≤14%. All properties are superior to the requirements for heavy traffic road base courses in the "Technical Specifications for Construction of Highway Pavement Base Courses" (JTG / TF20-2015).

[0012] 3. Low carbon footprint and technological advantages: No cement or other natural cementitious materials are required, and laboratory curing does not require high temperatures. Carbon emissions are reduced by more than 60% compared to traditional cement-stabilized crushed stone base courses (carbon emissions per ton of material are reduced from 85 kg to less than 15 kg). The laboratory preparation process can use conventional small-scale testing equipment (such as small crushers, forced mixers, and small vibratory compactors), eliminating the need for specialized large-scale equipment. This facilitates parameter optimization and performance verification, and reduces material costs by 16-22% (the cost per ton of material is reduced from 280 yuan to less than 225 yuan).

[0013] 4. Wide Engineering Adaptability: Multiple small-scale laboratory tests have demonstrated the material's strong adaptability to climatic conditions. It can be widely applied in North my country (low temperature ≥ -15℃), East China, and South China, and is suitable for base course construction of roads of different grades, including highways, first-class highways, and municipal arterial roads. The laboratory test cycle is comparable to the engineering curing cycle (28-day curing period), providing rapid parameter support for large-scale engineering applications. See [link / details]. Figure 1 . Attached Figure Description

[0014] Figure 1 This is a flowchart of the technology of this invention.

[0015] Figure 2 This is a comparison of the performance graphs of Embodiment 1, Embodiment 2, and Embodiment 3 of the present invention. Detailed Implementation

[0016] The present invention will be further described below through specific embodiments, see Figure 2 . Example 1

[0017] A method for co-preparing a solid waste road base material containing stone powder and recycled coarse aggregate includes the following steps: (1) Solid waste pretreatment: Recycled coarse aggregate: particle size 5-31.5mm, crushing value 16%, moisture content 6%, apparent density 2380kg / m³ 3 ; Recycled fine aggregate: particle size 0.075-4.75mm, crushing value 22%, moisture content 5.5%, mud content 2.8%, apparent density 2250kg / m³ 3 ; Stone powder: SiO2 content 70%, residue after passing through a 0.15mm sieve 3.5%, plasticity index 10; Steel slag: 2.5% free calcium oxide, particle size ≤4.5mm; Fly ash: Loss on ignition 6.5%, moisture content 0.6%; Desulfurized gypsum: moisture content 1.8%.

[0018] (2) Raw material ratio (parts by weight): 72 parts recycled coarse aggregate, 24 parts recycled fine aggregate, 15 parts stone powder, 16 parts steel slag, 10 parts fly ash, 5 parts desulfurized gypsum, and 3 parts activator (solid sodium silicate, modulus 2.2).

[0019] (3) Co-mixing: Dry mix for 1.5 min, add 10% water (based on the total mass of the mixture), wet mix for 4 min, consistency 15 mm.

[0020] (4) Compaction and molding: The mixture is placed into a 150mm×150mm×150mm mold in two layers, with each layer having a thickness of 60mm. A small vibratory compactor (excitation force 5-8kN, vibration frequency 30-50Hz) is used for compaction. The compaction process is as follows: first, light compaction twice (excitation force 5kN, compaction speed 10mm / s), then heavy compaction four times (excitation force 7-8kN, compaction speed 8mm / s), and finally light compaction once for finishing (excitation force 5kN, compaction speed 10mm / s); the compaction degree is 97.2%.

[0021] (5) Collaborative curing: First, place it in a standard curing box (20℃, relative humidity 96%) for 7 days, then transfer it to a natural environment with an ambient temperature of 26℃ for 28 days.

[0022] (6) Test results: 7-day unconfined compressive strength 3.9 MPa, 28-day unconfined compressive strength 5.6 MPa, splitting strength 0.58 MPa, resilience modulus 1680 MPa, and shrinkage rate 0.065%. Example 2

[0023] A method for co-preparing a solid waste road base material containing stone powder and recycled coarse aggregate includes the following steps: (1) Solid waste pretreatment: The crushing value of recycled coarse aggregate is 17%, the moisture content is 5.8%, and the apparent density is 2360 kg / m³. 3The recycled fine aggregate has a crushing value of 21%, a moisture content of 5%, a mud content of 2.9%, and an apparent density of 2230 kg / m³; the stone powder has a SiO2 content of 68%, a residue of 4% on a 0.15 mm sieve, and a plasticity index of 11; the steel slag has a free calcium oxide content of 2.7% and a particle size of ≤4.5 mm; the fly ash has a loss on ignition of 6.8% and a moisture content of 0.7%; and the desulfurized gypsum has a moisture content of 1.9%.

[0024] (2) Raw material ratio (parts by weight): 68 parts recycled coarse aggregate, 26 parts recycled fine aggregate, 16 parts stone powder, 18 parts steel slag, 8 parts fly ash, 6 parts desulfurized gypsum, and 4 parts activator (solid sodium silicate, modulus 2.3).

[0025] (3) Co-mixing: Add 11% water, dry mix for 1.8 min, wet mix for 3.8 min, consistency 17 mm.

[0026] (4) Compaction and molding: The mixture is placed into a 150mm×150mm×150mm mold in two layers, with each layer having a thickness of 65mm. A small vibratory compactor (excitation force 5-8kN, vibration frequency 30-50Hz) is used for compaction. The compaction process is as follows: first, light compaction twice (excitation force 5kN, compaction speed 10mm / s), then heavy compaction five times (excitation force 7-8kN, compaction speed 8mm / s), and finally light compaction once for finishing (excitation force 5kN, compaction speed 10mm / s); the compaction degree is 96.8%.

[0027] (5) Collaborative curing: First, place it in a standard curing box (21℃, 95% relative humidity) for 7 days, then transfer it to a natural environment at 19℃ for 28 days.

[0028] (6) Test results: 7-day unconfined compressive strength 3.7 MPa, 28-day unconfined compressive strength 5.3 MPa, splitting strength 0.56 MPa, resilience modulus 1600 MPa, and shrinkage rate 0.068%. Example 3

[0029] A method for co-preparing a solid waste road base material containing stone powder and recycled coarse aggregate includes the following steps: (1) Solid waste pretreatment: The crushing value of recycled coarse aggregate is 15%, the moisture content is 6.5%, and the apparent density is 2400 kg / m³. 3 The recycled fine aggregate has a crushing value of 20%, a moisture content of 6%, a mud content of 2.7%, and an apparent density of 2280 kg / m³. 3 Stone powder SiO2 content 72%, residue 3% after passing through a 0.15mm sieve, plasticity index 9; steel slag free calcium oxide 2.2%, particle size ≤4mm; fly ash loss on ignition 6.2%, moisture content 0.5%; desulfurized gypsum moisture content 1.7%.

[0030] (2) Raw material ratio (parts by weight): 75 parts recycled coarse aggregate, 22 parts recycled fine aggregate, 13 parts stone powder, 14 parts steel slag, 12 parts fly ash, 4.5 parts desulfurized gypsum, and 3.5 parts activator (solid sodium silicate, modulus 2.1).

[0031] (3) Co-mixing: Add 9% water, dry mix for 1.3 min, wet mix for 4.2 min, consistency 13 mm.

[0032] (4) Compaction and molding: The mixture is placed into a 150mm×150mm×150mm mold in two layers, with each layer having a thickness of 55mm. A small vibratory compactor (excitation force 5-8kN, vibration frequency 30-50Hz) is used for compaction. The compaction process is as follows: first, light compaction twice (excitation force 5kN, compaction speed 10mm / s), then heavy compaction three times (excitation force 7-8kN, compaction speed 8mm / s), and finally light compaction once for finishing (excitation force 5kN, compaction speed 10mm / s); the compaction degree is 98%.

[0033] (5) Collaborative maintenance: First, place it in a standard maintenance box (19℃, relative humidity 97%) for 7 days, and then transfer it to a natural environment at 32℃ for 28 days.

[0034] (6) Test results: 7-day unconfined compressive strength 4.1 MPa, 28-day unconfined compressive strength 5.9 MPa, splitting strength 0.6 MPa, resilience modulus 1750 MPa, and shrinkage rate 0.062%.

Claims

1. A method for co-preparing a solid waste road base material containing stone powder and recycled coarse aggregate, characterized in that, Includes the following steps: (1) Solid waste pretreatment: Recycled coarse aggregate, stone powder, steel slag, fly ash, recycled fine aggregate, and desulfurized gypsum are pretreated respectively; (2) Raw material ratio: by weight, 65-78 parts recycled coarse aggregate, 20-28 parts recycled fine aggregate, 12-18 parts stone powder, 12-19 parts steel slag, 7-14 parts fly ash, 4-7 parts desulfurized gypsum, and 2.5-4.5 parts solid sodium silicate activator. (3) Co-mixing: Dry mix the above raw materials for 1.2-1.8 min to obtain a mixture, then add water of 8.5-11.5% of the total mass of the mixture, wet mix for 3.5-4.5 min, and control the consistency to 12-18 mm; (4) Compaction molding: Layered compaction is carried out using a vibratory compactor, and the compaction degree is controlled to be ≥96.5%; (5) Collaborative curing: First, cure in a standard curing box for 7 days, then transfer to a natural environment for curing for 28 days; the temperature of the standard curing box is 20±2℃ and the relative humidity is ≥95%; the temperature of the natural curing environment is 16-34℃ and the relative humidity is ≥80%.

2. The method for co-preparing a solid waste road base material containing stone powder and recycled coarse aggregate according to claim 1, characterized in that, In step (1), the recycled coarse aggregate is controlled with a moisture content of 5-7%, a crushing value of ≤18%, a needle-like and flaky particle content of ≤14%, and an apparent density of ≥2350 kg / m³. 3 Stone powder should have a controlled moisture content of ≤1.5%, a 0.15mm sieve residue of ≤4%, a SiO2 content of ≥68%, and a plasticity index of ≤11. Recycled fine aggregate should be surface-dried to a moisture content of 5-6%, a crushing value of ≤23%, a mud content of ≤2.9%, and an apparent density of ≥2230 kg / m³. 3 The content of needle-like and flaky particles is ≤19%.

3. The method for co-preparing a solid waste road base material containing stone powder and recycled coarse aggregate according to claim 1, characterized in that, In step (1), the steel slag is magnetically separated to remove iron and then crushed to a particle size ≤4.5mm and a free calcium oxide content ≤2.8%; the fly ash is dried at 100-105℃ to a moisture content ≤0.8%, a loss on ignition ≤7%, and a water requirement ratio ≤105%; the desulfurized gypsum is dried at 80-85℃ to a moisture content ≤2%, and then crushed and passed through a 2.36mm sieve.

4. The method for co-preparing a solid waste road base material containing stone powder and recycled coarse aggregate according to claim 1, characterized in that, In step (2), the modulus of the solid sodium silicate activator is 2.1-2.4, and the fineness is controlled to have a sieve residue of ≤9% on a 0.08mm sieve.

5. The method for co-preparing a solid waste road base material containing stone powder and recycled coarse aggregate according to claim 1, characterized in that, In step (4), the compaction process is as follows: first, lightly compact twice: excitation force 5kN, compaction speed 10mm / s; then, heavily compact 4-5 times: excitation force 7-8kN, compaction speed 8mm / s; finally, lightly compact once to finish: excitation force 5kN, compaction speed 10mm / s.

6. The method for co-preparing a solid waste road base material containing stone powder and recycled coarse aggregate according to claim 5, characterized in that, In step (4), the surface moisture content of the mixture is monitored in real time. If the moisture content is less than 1%, water is added by micro-spraying to keep the moisture content fluctuation within 1±0.8%.

7. The method for co-preparing a solid waste road base material containing stone powder and recycled coarse aggregate according to claim 5, characterized in that, In step (5), when the ambient temperature of natural curing is below 15℃, the outside of the test block is wrapped with a 0.12mm thick polyethylene plastic film to ensure that the curing temperature is not lower than 11℃.

8. A solid waste road base material prepared by the method described in any one of claims 1-7, characterized in that, The material has an unconfined compressive strength of ≥3.6MPa at 7 days, an unconfined compressive strength of ≥5.2MPa at 28 days, a splitting strength of ≥0.55MPa, a resilient modulus of ≥1550MPa, and a shrinkage rate (28 days) of ≤0.07%.

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