Solid waste-based dry-mixed mortar and preparation method thereof

Abstract

The invention discloses solid-waste-based dry-mixed mortar and a preparation method thereof, the solid-waste-based dry-mixed mortar comprises the following raw materials in parts by mass: the cementing material comprises 20-35 parts of cement, 5-15 parts of fly ash and 5-10 parts of superfine slag powder; the solid waste aggregate comprises 30-45 parts of recycled fine aggregate, 10-20 parts of tailing sand and 5-15 parts of stone powder; the functional additive is prepared from the following components in parts by weight: 0.1 to 0.5 part of powdery polycarboxylic acid water reducing agent, 0.05 to 0.2 part of water-retaining agent, 0.01 to 0.05 part of air entraining agent, 0.05 to 0.15 part of retarder, 0.5 to 1.5 parts of thickening agent and 1 to 2 parts of expanding agent. The recycled fine aggregate, the tailing sand, the stone powder and other solid waste materials are scientifically proportioned, and the synergistic effect of the additive with the specific function is combined, so that the product has excellent mechanical properties and durability while maintaining good construction performance, and efficient resource utilization of solid waste is realized.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to a solid waste-based dry powder mortar and its preparation method. Background Technology

[0002] With the rapid development of my country's construction industry, the demand for natural sand and gravel resources in traditional dry-mix mortar has increased dramatically, leading to the depletion of natural aggregate resources. At the same time, mining, demolition, and industrial production processes generate large amounts of solid waste such as stone powder, tailings, and construction debris, which not only occupy significant land resources but also potentially cause dust and water pollution. How to achieve the resource utilization of these solid wastes has become a critical issue that urgently needs to be addressed by the building materials industry.

[0003] Currently, some studies have attempted to apply solid waste to dry mortar, but the following technical bottlenecks still exist: First, the amount of solid waste added is generally low, making it difficult to achieve large-scale resource utilization. This is mainly because a high amount of solid waste often leads to problems such as poor water retention and poor workability of the mortar. Second, the performance of solid waste materials fluctuates greatly, resulting in unstable mortar product quality. In addition, existing technologies have high requirements for the pretreatment of solid waste materials, which increases production costs.

[0004] In terms of additive application, traditional dry powder mortars mostly use single-function admixtures, which are difficult to meet the comprehensive requirements of solid waste-based mortars for workability, mechanical properties, and durability. In particular, when the amount of solid waste added increases, existing additive systems cannot effectively adjust key performance indicators such as mortar consistency, water retention, and strength.

[0005] Therefore, developing a dry mortar product that can achieve a high proportion of solid waste substitution, stable performance, and reasonable cost, and establishing a matching additive system and preparation process, is of great significance for promoting the green and sustainable development of the construction industry. Summary of the Invention

[0006] The main objective of this invention is to provide a solid waste-based dry powder mortar that can achieve a high proportion of solid waste replacement, has stable performance, and is cost-effective, as well as a method for its preparation.

[0007] To achieve the above objectives, the present invention provides a solid waste-based dry powder mortar, the raw materials of which include cementitious materials, solid waste aggregates, and functional additives, and the composition of each raw material by mass percentage includes:

[0008] The cementitious material includes 20-35 parts cement, 5-15 parts fly ash, and 5-10 parts slag powder; the solid waste aggregate includes 30-45 parts recycled fine aggregate, 10-20 parts tailings sand, and 5-15 parts stone powder; the functional additives include 0.1-0.5 parts powdered polycarboxylate superplasticizer, 0.05-0.2 parts water-retaining agent, 0.01-0.05 parts air-entraining agent, 0.05-0.15 parts retarder, 0.5-1.5 parts thickener, and 1-2 parts expansion agent.

[0009] Furthermore, the particle size of the recycled fine aggregate is 4.75–0.5 mm, the particle size of the tailings sand is 2.36–0.5 mm, and the specific surface area of ​​the stone powder is ≥400 m². 2 / kg.

[0010] Furthermore, the water-retaining agent is a methylcellulose ether with a viscosity of 40,000 mPa·s.

[0011] Furthermore, the air-entraining agent is an alkylbenzene sulfonate-based air-entraining agent.

[0012] Furthermore, the retarder is sodium gluconate.

[0013] Furthermore, the thickener is a redispersible latex powder.

[0014] Furthermore, the expanding agent is a sulfoaluminate expanding agent.

[0015] The present invention also provides a method for preparing the above-mentioned solid waste-based dry powder mortar, comprising the following steps:

[0016] S1: Add recycled fine aggregate, tailings sand and stone powder into a mixer and dry mix them;

[0017] S2: Add cementitious material to the above mixer, mix evenly, then add functional additives, mix evenly, and obtain the solid waste-based dry powder mortar.

[0018] Furthermore, in step S1, the dry mixing time is 30–60 seconds.

[0019] Furthermore, in step S2, the mixing time after adding the gelling material is 60-90 seconds; the mixing time after adding the functional additive is 120-180 seconds.

[0020] The prepared solid waste-based dry powder mortar can be packaged immediately.

[0021] In this invention, cement, as the main cementitious material, provides the foundation for early strength development, and its hydration product, CSH gel, forms the main strength skeleton of the mortar; fly ash plays a role in filling pores with micro-aggregate effect, and its pozzolanic activity reacts with Ca(OH)2 in the later stage to generate CSH gel, improving later strength and durability; slag powder is a potential hydraulic material, which gradually hydrates in an alkaline environment, continuously contributing to strength development and refining the pore structure;

[0022] In this invention, recycled fine aggregate serves as the main skeleton material, providing mechanical support, and the old cement paste attached to its surface can participate in secondary hydration; tailings sand is used to fill the voids between recycled aggregates, optimize particle size distribution, and increase bulk density; the high specific surface area of ​​stone powder gives it a micro-filling effect and weak cementitious activity, which can both fill micropores and participate in interfacial reactions. The micro-filling effect of stone powder refines the interfacial transition zone (ITZ), while redispersible latex powder forms an organic reinforcing layer at the interface. The two work together to reduce the ITZ thickness and improve the interfacial strength.

[0023] In this invention, the polycarboxylate superplasticizer disperses particles through steric hindrance, releasing encapsulated water and significantly reducing the water-to-binder ratio; the water-retaining agent, methyl cellulose ether, forms a three-dimensional network structure with hydrophilic polymer chains, binding free water through hydrogen bonds and improving water retention; the air-entraining agent, alkylbenzene sulfonate, introduces uniform and stable microbubbles by reducing the surface tension of the liquid phase; the thickener, after redispersible latex powder forms a film, it creates an organic-inorganic interpenetrating network, enhancing bonding strength and flexibility; and the retarder, sodium gluconate, complexes Ca... 2+ It slows down the dissolution of cement minerals and regulates the hydration process; the expansion agent sulfoaluminate generates ettringite crystals, producing moderate expansion stress to compensate for shrinkage.

[0024] This invention uses recycled fine aggregate as the main framework, tailings sand to fill the medium-coarse pores, and stone powder to further fill the micropores, forming a three-stage compact packing system of "coarse-medium-fine" to improve density. In addition, Ca(OH)2 released during cement hydration triggers the pozzolanic reaction of fly ash and slag powder, forming a cascade reaction chain of "primary hydration-secondary reaction" to achieve continuous strength development. Furthermore, this invention features a water-retention-water-reduction synergy: the water-retention effect of methyl cellulose ether ensures that the polycarboxylate superplasticizer can still fully exert its dispersion effect under low water-cement ratio conditions, and the synergy of both reduces the water-cement ratio. This invention also features an air-entraining-thickening synergy: the air bubbles introduced by the air-entraining agent are stabilized by the polymer film of the redispersible latex powder, forming an "elastic microsphere" structure, which improves workability without significantly reducing strength. Finally, this invention features a retarding-expansion sequence synergy: sodium gluconate delays the initial hydration, giving the sulfoaluminate expansive agent more reaction time, allowing the expansion effect to occur precisely during the transition from plasticity to hardening.

[0025] The beneficial effects of this invention are reflected in:

[0026] This invention innovatively utilizes multiple industrial solid wastes to synergistically replace traditional raw materials, coupled with a carefully designed multifunctional additive system, to successfully develop a high-performance, environmentally friendly, and economical solid waste-based dry mortar product. This technical solution achieves efficient resource utilization of solid waste, not only solving the problem of traditional dry mortar's dependence on natural sand and gravel resources but also significantly reducing the environmental burden during building material production. Through the scientific proportioning of recycled fine aggregates, tailings sand, and stone powder, combined with the synergistic effect of specific functional additives, the product maintains good workability while also possessing excellent mechanical properties and durability.

[0027] This invention establishes a complete technology system for solid waste-based dry powder mortar. Regarding raw material selection, the rational combination of solid waste aggregates with different particle sizes and properties ensures the product's skeletal structure and density. In terms of the additive system, the synergistic effect of multiple functional additives effectively solves technical problems such as poor workability and insufficient water retention caused by solid waste materials. Methylcellulose ether, as a water-retaining agent, significantly improves the mortar's water retention performance; redispersible latex powder enhances bonding strength and flexibility; polycarboxylate superplasticizer improves fluidity and density; air-entraining agent optimizes the pore structure and enhances freeze-thaw resistance; retarder regulates setting time; and expansion agent effectively controls shrinkage deformation.

[0028] The implementation of this technical solution has yielded significant results: First, it has enabled large-scale resource utilization of solid waste, providing a new approach for the treatment of solid waste such as construction waste and mine tailings; second, the product performance fully meets engineering application requirements, achieving or exceeding traditional mortar in terms of water retention, workability, and strength development; third, the production process is simple and reliable, easily facilitating industrial production; and finally, it offers significant overall cost advantages and has broad market application prospects. The promotion and application of this technology will strongly promote the green and sustainable development of the construction industry and is of great significance for advancing the development of a circular economy and the construction of ecological civilization. Detailed Implementation

[0029] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0030] Unless otherwise specified, the raw materials, reagents, or apparatus used in the following embodiments can be obtained from conventional commercial sources or by existing known methods; unless otherwise specified, the methods used in the embodiments of the present invention are methods mastered by those skilled in the art. Wherein:

[0031] The cement was purchased from Dengfeng Hongchang Cement Co., Ltd., PO42.5.

[0032] The fly ash was purchased from Zhejiang Jishun Metallurgical Equipment Co., Ltd., and is classified as Grade II fly ash.

[0033] The slag powder was purchased from Lingshou County Xinfu Mineral Products Processing Plant; it is S95 grade slag powder.

[0034] The tailings sand was purchased from Haotian Talc Powder Factory in Yinan County, Shandong Province.

[0035] The powdered polycarboxylate superplasticizer, model PC-1021, was purchased from Zhengzhou Chengrui Chemical Products Co., Ltd.

[0036] The methylcellulose ether was purchased from Langfang Feitai New Material Technology Co., Ltd., with a viscosity of 40000 mPa·s.

[0037] The alkylbenzene sulfonate air-entraining agent was purchased from Guangzhou Xiangmei Chemical Technology Co., Ltd., under the Xiangmei brand name HMA-101.

[0038] Sodium gluconate was purchased from Shandong Kerry Chemical Co., Ltd. Kerry brand Gluconic Acid Sodium Salt 98% (for industrial-grade concrete retarder, purity ≥98%).

[0039] The redispersible latex powder was purchased from Renqiu Jinyu Chemical Co., Ltd., Jinyu brand R-705 (solid content ≥98%, glass transition temperature Tg≈-10℃, suitable for building adhesives, mortars and other fields).

[0040] The sulfoaluminate expansive agent was purchased from Anhui Huaihe Cement Co., Ltd., model AH-U EA-1 (calcium sulfoaluminate expansive agent).

[0041] Example 1

[0042] Preparation of solid waste-based dry powder mortar

[0043] (1) Raw material preparation

[0044] 1.1 Preparation of recycled fine aggregate

[0045] Raw material preparation: Take concrete blocks from demolished buildings;

[0046] Primary crushing: Use a PE250×400 jaw crusher, with a discharge particle size ≤5mm;

[0047] Secondary crushing: PF-1214 impact crusher is used, the rotor speed is adjusted to 600rpm, the gap between the hammer and the impact plate is 15mm, and metal impurities are removed by the iron remover after crushing.

[0048] Screening: Use a ZSG1545 vibrating screen with double-layer screens of 4.75mm and 0.5mm to collect materials with a particle size of 4.75 to 0.5mm.

[0049] Drying process: The screened material is spread flat in a drying tray and dried in a 101-3A electric heating forced-air drying oven at 105℃. The material is turned over every 30 minutes and dried to constant weight (about 4 hours). The moisture content is tested to be <1%, and recycled fine aggregate is obtained.

[0050] 1.2 Tailings Sand Treatment

[0051] Raw material preparation: Take tailings sand with a moisture content of 8%;

[0052] Drying treatment: Use a GZX-9070MBE digital display drying oven at 105℃ to dry, stirring once every 30 minutes, until constant weight is achieved (about 6-8 hours);

[0053] Screening: Use a ZSG1545 vibrating screen with double-layer screens of 2.36mm and 0.5mm to collect materials with a particle size of 2.36 to 0.5mm.

[0054] 1.3 Stone Powder Processing

[0055] Raw material preparation: Take marble scraps;

[0056] Primary crushing: Using an XPC-100×60 jaw crusher, the output particle size is ≤5mm;

[0057] Ball milling: A QM-3SP4 planetary ball mill was used, with a feed rate of 500g / batch, a ball-to-material ratio of 10:1, a rotation speed of 300rpm, and a grinding time of 45 minutes (with a cooling pause every 15 minutes). After ball milling, specific surface area was tested using an FBT-9 fully automatic specific surface area meter, according to GB / T8074 standard. The specific surface area was ≥400m². 2 / kg;

[0058] (2) Mixing process

[0059] Equipment: SHR-100A ribbon mixer;

[0060] 2.1 Premixed Solid Waste Aggregates

[0061] Feeding sequence: First add 3500g of recycled fine aggregate, then add 1500g of tailings sand, and finally add 1200g of stone powder; Mixing parameters: 30rpm, 45 seconds;

[0062] Mixing uniformity test: Take 5 samples, and the content deviation of each component should be ≤2%.

[0063] 2.2 Mixing of cementitious materials

[0064] Feeding method: 3000g cement, 1000g fly ash, and 800g slag powder are added sequentially through the top feed port of the mixer; Mixing parameters: speed 45rpm, time 75 seconds;

[0065] Mixing uniformity test: Use a sampler to take material from the middle and observe for no clumping.

[0066] 2.3 Addition of functional additives

[0067] Feeding method: First, premix 30g of powdered polycarboxylate superplasticizer with 10g of retarder (sodium gluconate), premix 10g of water-retaining agent (methylcellulose ether) with 100g of thickener (redispersible latex powder), and premix 3g of air-entraining agent (alkylbenzene sulfonate air-entraining agent) with 150g of expanding agent (sulfoaluminate expanding agent). Then, put the above premixed materials into the mixer. Mixing parameters: speed 60rpm; time 150 seconds (±3 seconds); temperature monitoring: material temperature ≤45℃.

[0068] Example 2

[0069] Preparation of solid waste-based dry powder mortar

[0070] The preparation method of this embodiment is the same as that of Embodiment 1, except that the raw material dosage is adjusted as follows: cement 2500g; fly ash 1200g; slag powder 1000g; recycled fine aggregate 4000g; tailings sand 1200g; stone powder 1200g; total amount of functional additives 309g (each component is scaled proportionally).

[0071] Example 3

[0072] Preparation of solid waste-based dry powder mortar

[0073] The preparation method of this embodiment is the same as that of Embodiment 1, except that the raw material dosage is adjusted as follows: cement 3500g; fly ash 500g; slag powder 500g; recycled fine aggregate 4500g; tailings sand 1000g; stone powder 500g; total amount of functional additives 200g (each component is scaled proportionally).

[0074] Comparative Example 1

[0075] Comparison of the preparation of solid waste-based dry powder mortar

[0076] The preparation method of this comparative example is the same as that of Example 1, except that the addition of stone powder is omitted and the amount of tailings sand is increased to 2700g.

[0077] Comparative Example 2

[0078] Comparison of the preparation of solid waste-based dry powder mortar

[0079] The preparation method of this comparative example is the same as that of Example 1, except that the water-retaining agent methyl cellulose ether is omitted.

[0080] Comparative Example 3

[0081] Comparison of the preparation of solid waste-based dry powder mortar

[0082] The preparation method of this comparative example is the same as that of Example 1, except that the mixing process does not use distributed mixing, and all raw materials are mixed at once for 180 seconds.

[0083] Comparative Example 4

[0084] Comparison of the preparation of solid waste-based dry powder mortar

[0085] The preparation method of this comparative example is the same as that of Example 1, except that the addition of tailings sand is omitted and the amount of stone powder is increased to 2700g.

[0086] Comparative Example 5

[0087] Comparison of the preparation of solid waste-based dry powder mortar

[0088] The preparation method of this comparative example is the same as that of Example 1, except that the addition of alkylbenzene sulfonate air-entraining agents is omitted.

[0089] Comparative Example 6

[0090] Comparison of the preparation of solid waste-based dry powder mortar

[0091] The preparation method of this comparative example is the same as that of Example 1, except that the addition of the retarder sodium gluconate is omitted.

[0092] Performance testing

[0093] The solid waste-based dry powder mortars prepared in the above embodiments and comparative examples were subjected to performance tests according to the following methods, and the results are shown in Table 1 below:

[0094] I. Consistency Test

[0095] Standard basis: JGJ / T 70-2009; Instruments and equipment: cement mortar tumbling table (amplitude 10.0±0.2mm); truncated cone mold (upper diameter 70mm, lower diameter 100mm, height 60mm); steel tamping rod (diameter 20mm, length 200mm); electronic balance (accuracy 0.1g).

[0096] Test Procedure: Sample Preparation: Take 300g of dry mortar powder + 135g of distilled water (water-cement ratio 0.45), and mix slowly (140±5rpm) for 2 minutes using a planetary mixer; Mold Application: Place the mixture into a truncated conical mold in two layers, tamping each layer 15 times; After leveling, lift the mold vertically; Start the jumping table and jump 15 times at a frequency of 1 time / second; Measure the expansion diameter in two vertical directions with vernier calipers and take the average value; Data Recording: The test environment temperature is 20±2℃, and the relative humidity is 60±5%. Perform three parallel tests and take the arithmetic mean (range ≤5mm).

[0097] II. Water Retention Rate Test

[0098] Standard Basis: GB / T 28627-2012; Specialized Equipment: Buchner funnel (inner diameter 150mm); vacuum pump (vacuuming rate 2L / s); medium-speed qualitative filter paper (diameter 185mm); filtration flask (1000mL). Operating Procedure: Weigh 200g of the mixed mortar (M1) and spread it evenly on the filter paper; apply a vacuum of -0.05MPa and continue filtration for 10 minutes; weigh the remaining mortar on the filter paper (M2), water retention rate = (M2 / M1)×100%. Key Controls: Vacuum system sealing test (pressure drop ≤5% within 30s); filter paper must be dried at 105℃ for 2 hours before use.

[0099] III. Determination of setting time

[0100] Test standard: ASTM C403;

[0101] Equipment configuration: Penetration resistance meter (probe area 20mm²) 2 The equipment included: a constant temperature curing chamber (20±1℃); and a time recorder (accuracy ±1min). Test procedure: The mortar was poured into a 150×150×150mm mold and the surface was smoothed; it was placed in a 20℃ curing environment, and the test began with the addition of water; the penetration resistance was tested every 30 minutes: the probe was inserted vertically to a depth of 25mm, and the resistance value was recorded (accurate to 0.1MPa). Initial setting: the time when the penetration resistance reached 3.5MPa; final setting: the time when the penetration resistance reached 28MPa.

[0102] IV. Compressive Strength Test

[0103] Execution Standard: GB / T 17671-2021; Specimen Preparation: Mold Size: 40×40×160mm triple mold; Molding Procedure: Vibration frequency 50±1Hz, amplitude 0.5±0.05mm, vibration time 120±5s; Curing Conditions: Water curing at 20±1℃; Test Points: Use a 300kN universal testing machine, loading rate 2400±200N / s; Compressive Strength = Failure Load / Compressed Area (1600mm²) 2 ); For each group of 6 specimens, after removing data with a deviation >10%, the average value is taken.

[0104] V. Bond Strength Test

[0105] Testing standard: JG / T 230-2007; Special equipment: tensile clamp (bonding area 40×40mm); structural adhesive (epoxy resin); tensile testing machine (accuracy 1%); Test method: A 10mm thick mortar layer is formed on a concrete substrate. After standard curing for 28 days, 5 test points are cut out with a cutting machine. Tensile heads are bonded with structural adhesive, and tensile force is applied at a speed of 5mm / min. The maximum load at interface failure is recorded.

[0106] VI. Drying Shrinkage Rate Test

[0107] Test Standard: GB / T 50082-2009; Instrument Configuration: Length Comparator (accuracy 0.001mm); Shrinkage Mold (100×100×515mm); Constant Temperature and Humidity Chamber (20±2℃, 60±5%RH); Operating Procedures: After molding, the specimen is cured in the mold for 24 hours before demolding. The initial length (L0) is measured immediately. The specimen is then moved to a constant temperature and humidity environment, and the lengths (L0, L ... t Shrinkage rate = (L0 - L) t ) / gauge length × 100%.

[0108] VII. Gas Content Test

[0109] Standard method: ASTM C231; Equipment requirements: Gas content meter (range 0-10%, accuracy 0.1%); Calibration cylinder (7% standard gas content), tamping rod (16mm diameter); Test procedure: Fill the container with mortar in three layers, tamp each layer 25 times, level it, seal the container, pressurize to 0.2MPa, and stabilize for 10s; read the number of divisions the pressure gauge drops, and find the gas content from the calibration curve; The accuracy of the equipment must be verified with the calibration cylinder before testing.

[0110] VIII. Freeze-thaw cycle test

[0111] Execution standard: GB / T 50082-2009; Test system: Fully automatic freeze-thaw tester (temperature range -20-20℃); Dynamic elastic modulus tester, mass loss weighing device (accuracy 0.1g); Test regime: After 28 days of curing, the specimen is saturated with water for 48 hours; Each freeze-thaw cycle: cooling to -18℃ (4h), heating to +5℃ (4h); Every 25 cycles, the following are measured: mass loss rate, relative dynamic elastic modulus; Termination condition: mass loss > 5% or dynamic elastic modulus < 60%.

[0112] The test results are shown in Tables 1 and 2:

[0113] Table 1 Performance Test Results (I)

[0114]

[0115]

[0116] As shown in Table 1, the comparative test data of the embodiments and comparative examples fully verify the breakthrough progress of this invention in solving the bottlenecks of traditional mortar technology. Regarding water retention performance, the water retention rates of the three embodiments remained consistently high at 95.3%-96.8%, an increase of 7.3-8.8 percentage points compared to the 88% required by the traditional mortar standard, and significantly better than Comparative Example 2 (82.0%) without added water-retaining agent. This improvement stems from the synergistic mechanism of methylcellulose ether and redispersible latex powder: methylcellulose ether molecules form a three-dimensional water molecule binding network through hydroxyl groups, while latex powder constructs a polymer barrier membrane in the pores. The combined water retention effect of the two reduces the water evaporation rate by more than 60%, and in actual open environments, it can maintain no bleeding for more than 2.5 hours. In terms of shrinkage resistance, the drying shrinkage rate of the embodiments was controlled at an excellent level of 0.026-0.031%, which is 38-48% lower than the upper limit of 0.05% for traditional mortar. It also showed significant advantages compared with Comparative Example 1 (0.038%) which lacked stone powder filling and Comparative Example 2 (0.042%) which lacked water retention control. This is mainly due to the synergistic effect of three technologies: the sulfoaluminate expanding agent generates ettringite crystals in the early stage of hydration (1-8h) to produce precise expansion compensation; high specific surface area stone powder (≥400m²) provides a high specific surface area of ​​stone powder. 2 The physical filling of capillary pores by the recycled aggregate ( / kg) reduces porosity by 18-22%; the dense skeleton formed by the optimized gradation of recycled aggregate and tailings sand further inhibits shrinkage deformation. The water retention rate fluctuation is only 0.5-0.9% (traditional 2.5-3.8%), and this improved stability stems from the innovative combination of raw material pretreatment process and staged mixing technology. Specifically, the moisture content of recycled aggregate is strictly controlled at <1%, reducing strength dispersion by 40%; the three-stage process of premixing solid waste aggregate (30-60s) + mixing adhesive (60-90s) + post-mixing of additives (120-180s) improves component uniformity by 35%; the molecular-level synergy of polycarboxylate superplasticizer and air-entraining agent stabilizes the bubble spacing coefficient in the ideal range of 0.15-0.20mm.

[0117] Table 2 Performance Test Results (II)

[0118]

[0119]

[0120] As can be seen from Table 2, Example 1 exhibits several performance advantages over Comparative Examples 4-6: While Comparative Example 4 omits tailings sand and increases stone powder usage, Example 1 effectively improves aggregate gradation by retaining tailings sand, maintaining consistency and water retention at relatively high levels of 98±2mm and 96.8±0.5% respectively (approximately 8.2% and 1.3% higher than Comparative Example 4). Simultaneously, it increases 28-day compressive strength by 9.5% and reduces shrinkage by 15.4%, resolving the problems of decreased fluidity, insufficient density, and exacerbated drying shrinkage caused by aggregate structure deterioration. Compared to the comparative examples... In Example 5, omitting the air-entraining agent resulted in a sharp drop in air content of 30.8% (to only 4.5%), leading to a slight increase in consistency and a slight decrease in shrinkage. Example 1 stabilized the air content at 6.5±0.3% by adding an air-entraining agent. Regarding the narrowing of the construction window caused by omitting the retarder in Comparative Example 6 (which shortened the initial setting time by 21.9% to 2.5h), Example 1 controlled the initial setting time at 3.2±0.2h by retaining the sodium gluconate retarder. This ensured sufficient working time and, due to the retarder's reasonable regulation of the hydration process, solved the construction inconvenience and shrinkage control problems caused by excessively rapid early hydration. In summary, Example 1, through the synergistic effect of tailings sand, air-entraining agent, and retarder, outperformed the comparative example in key indicators such as consistency, water retention, workability, strength stability, and shrinkage control. It effectively solved a series of performance defects caused by aggregate gradation imbalance, missing air bubbles, and uncontrolled setting time.

[0121] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A solid waste-based dry powder mortar, characterized in that, The raw materials include cementitious materials, solid waste aggregates, and functional additives. By mass, the composition of each raw material includes: The cementitious material includes 20-35 parts cement, 5-15 parts fly ash, and 5-10 parts slag powder; the solid waste aggregate includes 30-45 parts recycled fine aggregate, 10-20 parts tailings sand, and 5-15 parts stone powder; the functional additives include 0.1-0.5 parts powdered polycarboxylate superplasticizer, 0.05-0.2 parts water-retaining agent, 0.01-0.05 parts air-entraining agent, 0.05-0.15 parts retarder, 0.5-1.5 parts thickener, and 1-2 parts expansion agent.

2. The solid waste-based dry powder mortar as described in claim 1, characterized in that, The recycled fine aggregate has a particle size of 4.75–0.5 mm, the tailings sand has a particle size of 2.36–0.5 mm, and the stone powder has a specific surface area ≥400 m². 2 / kg.

3. The solid waste-based dry powder mortar as described in claim 1, characterized in that, The water-retaining agent is a methylcellulose ether with a viscosity of 40,000 mPa·s.

4. The solid waste-based dry powder mortar as described in claim 1, characterized in that, The air-entraining agent is an alkylbenzene sulfonate-based air-entraining agent.

5. The solid waste-based dry powder mortar as described in claim 1, characterized in that, The retarder is sodium gluconate.

6. The solid waste-based dry powder mortar as described in claim 1, characterized in that, The thickener is a redispersible latex powder.

7. The solid waste-based dry powder mortar as described in claim 1, characterized in that, The expanding agent is a sulfoaluminate expanding agent.

8. The method for preparing solid waste-based dry powder mortar according to any one of claims 1 to 7, characterized in that, Includes the following steps: S1: Add recycled fine aggregate, tailings sand and stone powder into a mixer and dry mix them; S2: Add cementitious material to the above mixer, mix evenly, then add functional additives, mix evenly, and obtain the solid waste-based dry powder mortar.

9. The method for preparing solid waste-based dry powder mortar as described in claim 8, characterized in that, In step S1, the dry mixing time is 30-60 seconds.

10. The method for preparing solid waste-based dry powder mortar as described in claim 8, characterized in that, In step S2, the mixing time after adding the gelling material is 60-90 seconds; the mixing time after adding the functional additive is 120-180 seconds.

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