Low-cost self-curing concrete and preparation method thereof
By utilizing solid waste such as washed sand mud, recycled aggregates, and high-titanium slag to construct self-curing concrete, the problem of difficult concrete curing in arid and windy environments has been solved, achieving low-cost, high-performance self-curing effects, and is suitable for various engineering scenarios.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JIAHUA SPECIAL CEMENT
- Filing Date
- 2025-12-25
- Publication Date
- 2026-04-24
AI Technical Summary
Existing concrete is difficult to cure in arid and windy environments. External curing is costly and its effects are unstable. Commonly used internal curing materials are expensive or have a negative impact on concrete strength. Furthermore, industrial solid waste is difficult to treat.
Using industrial solid waste such as washed sand mud, recycled aggregates and high-titanium slag as raw materials, and by optimizing the material ratio and preparation process, an internal self-curing system is constructed. It utilizes polyacrylamide molecules to lock in water and aggregates to absorb and release water slowly, combined with zeolite powder to retain water, to form self-curing concrete.
It achieves continuous hydration without the need for external watering, significantly reduces material costs, improves the mechanical properties and durability of concrete, solves the problem of solid waste treatment, and is suitable for engineering scenarios where curing conditions are limited, such as drought, water shortage, or high-altitude operations.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of concrete materials technology, specifically to a low-cost self-curing concrete and its preparation method. Background Technology
[0002] With the rapid development of the construction industry, the demand for concrete, as a core structural material, continues to rise, and it is widely used in various construction scenarios such as high-rise buildings, large-scale infrastructure, and transportation projects. However, concrete pouring in harsh climatic environments such as drought and wind generally faces prominent curing challenges: low air humidity and high wind speeds cause rapid evaporation of moisture from the concrete surface, resulting in a sharp drop in internal relative humidity, which severely hinders the hydration process of the cementitious materials. This not only significantly reduces the early and later mechanical properties of concrete but also easily induces plastic shrinkage and drying shrinkage, generating a large number of microcracks, seriously affecting the integrity, durability, and long-term safety of the structure, and shortening the service life of the building.
[0003] To address these issues, the most common concrete curing methods currently used in the engineering field are external curing, primarily including covering with wet burlap sacks, straw bags, or sand and regularly sprinkling water to maintain moisture, or spraying curing agents onto the concrete surface to form a water-retaining film. However, these traditional methods have significant limitations: the covering and sprinkling method requires a continuous investment of large amounts of water resources and manpower, making it difficult to implement in arid and water-scarce areas or in the construction of high-rise building facades, and the uniformity of curing is difficult to guarantee; while the surface curing agent method reduces the frequency of watering to some extent, the film formed has poor stability in dry and windy environments, is prone to cracking and failure, and increases material costs and construction procedures, resulting in inconsistent curing effects.
[0004] Addressing the inherent limitations of external curing techniques, the academic and engineering communities generally agree that the most fundamental and effective solution is to compensate for the moisture required for hydration within the concrete itself—that is, to develop internal curing techniques. The core of internal curing is incorporating components with excellent water absorption and slow-release capabilities during concrete preparation. As the concrete hardens and internal humidity decreases, these components gradually release the stored moisture, thus providing a continuous and uniform guarantee for the hydration reaction of the cementitious materials, fundamentally solving the problem of insufficient moisture supply in arid environments.
[0005] Currently, there are many types of commonly used internal curing agents, mainly including lightweight porous materials such as lightweight expanded clay, pumice, expanded shale, zeolite, rice husk ash, as well as lightweight aggregates and superabsorbent resins. Among them, lightweight aggregates and superabsorbent resins are relatively widely studied and applied in the field of concrete internal curing due to their high water absorption capacity and certain water release characteristics.
[0006] However, existing internal maintenance technologies still face significant technical bottlenecks and economic obstacles in practical engineering applications, limiting their large-scale promotion: Limitations of superabsorbent polymer (SAP): Although SAP has a high water absorption rate, it expands significantly after absorbing water, leaving large pores in hardened concrete. This disrupts the microstructure and density of the matrix, often negatively impacting the strength and modulus of elasticity of the concrete. Furthermore, as a chemical product, SAP has a high procurement cost, significantly increasing the unit material cost of concrete.
[0007] The performance limitations of lightweight aggregates: Lightweight aggregates have relatively low strength and insufficient compressive and flexural strength. When their admixture is high, it will directly weaken the overall mechanical properties and load-bearing capacity of concrete, making them unsuitable for structural engineering projects with high strength requirements. At the same time, the matching between their water absorption and release dynamics and the hydration process of cementitious materials is also difficult to control precisely.
[0008] Other material-related issues: Materials such as natural zeolite and rice husk ash, due to their limited water absorption and release efficiency, or their unstable sources and high processing costs, make it difficult to achieve an effective balance between economy and practicality while ensuring concrete performance.
[0009] At the same time, my country generates a massive amount of solid waste annually during industrial production and urban construction, such as sand washing mud from manufactured sand washing, recycled aggregate obtained from crushed demolition waste, and high-titanium slag, a byproduct of vanadium-titanium magnetite smelting. The long-term accumulation of these solid wastes not only occupies vast amounts of land resources but also poses environmental risks such as dust and water pollution. Their resource utilization has become an urgent need for the sustainable development of the industry.
[0010] Against this backdrop, this invention addresses the current technological shortcomings in self-curing materials and the national strategic need for solid waste resource utilization, aiming to propose an innovative solution. By cleverly utilizing washed sand mud (especially the residual polyacrylamide) in a graded manner and optimizing the gradation and performance of recycled aggregates and high-titanium slag, the characteristics of solid waste are transformed into advantages for improving concrete performance. This results in the development of a low-cost self-curing concrete that combines excellent self-curing performance, good mechanical properties, and significant cost advantages, providing a new technical approach for the preparation of green, low-carbon, and high-performance concrete. Summary of the Invention
[0011] The purpose of this invention is to address the problems in existing technologies, such as the difficulty of curing concrete in arid and windy environments, the high cost and unstable effectiveness of external curing, and the expensive cost or negative impact on concrete strength of commonly used internal curing materials. This invention provides a low-cost self-curing concrete and its preparation method. Using industrial solid waste as the main raw material, this invention constructs an internal self-curing system through optimized material proportions and innovative preparation processes. This enables continuous hydration and performance development of concrete without the need for external watering, while significantly reducing material costs and improving the resource utilization rate of solid waste.
[0012] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A low-cost self-curing concrete, comprising the following raw materials per cubic meter: Cement: 266-304 kg / m³; Fly ash: 50-76 kg / m³; Washed sand and mud fine powder: 13-25 kg / m³; Zeolite powder: 13-25 kg / m³; Fine aggregate: 785-811 kg / m³; Coarse aggregate: 1057-1083 kg / m³; Water-reducing agent: 4.18-4.56 kg / m³; Water: 160-162 kg / m³; Among them, the fine aggregate is composed of washed sand and mud fine aggregate, recycled fine aggregate and manufactured sand in a mass ratio of 1:(4-5):(4-5); The coarse aggregate is continuously graded high-titanium slag crushed stone; Both the fine powder and fine aggregate of washed sand mud are derived from the mud slurry generated during the washing process of manufactured sand. They are obtained by drying, screening and grading. The fine powder of washed sand mud contains residual anionic or nonionic polyacrylamide. The polyacrylamide molecular chains in the washed sand and mud fine powder are stretched out through shearing and mixing treatment and combine with some fly ash to form micron-sized composite aggregates in concrete.
[0013] Furthermore, the micron-sized composite aggregates have a structure with fly ash particles as the core and washed sand mud fine powder with adsorbed extended polyacrylamide molecular chains as the shell.
[0014] Furthermore, the particle size of the fine powder of the washed sand and mud is no greater than 0.075 mm, and the particle size of the fine aggregate of the washed sand and mud is 0.075-0.15 mm.
[0015] Furthermore, the particle sizes of the recycled fine aggregate and the manufactured sand are 0.15-1.18 mm and 1.18-4.75 mm, respectively.
[0016] Furthermore, the continuously graded high-titanium slag crushed stone has a particle size of 5-20 mm, a water absorption rate of 8.8%, a mud content of 0.3%, a crushing value of 9.1%, and an apparent density of 3098 kg / m³. 3 The bulk density is 2001 kg / m³. 3 .
[0017] Furthermore, the recycled fine aggregate is derived from waste concrete through crushing, screening, and washing, with a saturated water absorption rate of 10.9% and an apparent density of 2303 kg / m³. 3The saturated water absorption rate of the manufactured sand is 1.3%, and its apparent density is 2640 kg / m³. 3 .
[0018] Furthermore, the cement is ordinary Portland cement with a strength grade of 42.5; the water-reducing agent is a polycarboxylate high-performance water-reducing agent with a water reduction rate of more than 30% and a solid content of 40%; the fly ash is Grade I fly ash with a 28-day activity index of 88%; the zeolite powder has a particle size of 180μm, a water absorption rate of 5.52%, and a loss on ignition of 12.18%.
[0019] A method for preparing low-cost self-curing concrete includes the following steps: S1. Slurry activation and composite suspension preparation: Washed sand mud fine powder and water are mixed at a mass ratio of 1:(3-5) and stirred continuously for 15-25 min under shear conditions of 40-50℃ and 1500-2500 rpm to obtain activated slurry; Take a portion of fly ash, spray it with a nonionic surfactant aqueous solution of 0.3-0.7% of the fly ash mass (to form loose wet material), and then gradually add it to the activated slurry at a dry basis mass ratio of (1.2-1.8):1. High shear treatment is carried out at 12000-18000 rpm for 10-20 min to form washed sand mud-fly ash composite suspension; In S1, the shearing treatment at 1500-2500 rpm is used to break up the agglomerates of fine sand and mud particles, promoting the dissolution and full expansion of anionic or nonionic polyacrylamide (PAM) molecular chains adsorbed on and inside the particles in the aqueous phase, exposing active groups. The shearing treatment at 12000-18000 rpm uses the expanded PAM long chains as molecular bridges in a high shear field. Its chain segments are simultaneously adsorbed onto the smooth surface of fly ash and the rough surface of fine sand and mud particles through hydrogen bonds and van der Waals forces, thereby "anchoring" and "binding" the fine sand and mud particles around the fly ash particles, forming micron-sized composite agglomerates with fly ash as the core and a fine sand and mud powder-PAM composite layer as the shell.
[0020] S2. Adjustment of suspension performance: Add water-reducing agent to the composite suspension. The dosage of water-reducing agent is 0.4-0.8% of the total dry basis of fly ash and washed sand mud powder in the composite suspension. Then adjust the Marsh funnel viscosity of the composite suspension to 35-65 seconds to ensure good fluidity. S3. Pre-treatment of aggregates with water saturation: Soak the coarse high-titanium slag crushed stone and the recycled fine aggregate in the fine aggregate until they are saturated with water, take them out and wipe off the surface moisture to obtain saturated coarse aggregate and saturated recycled fine aggregate for later use. S4. Batching and Mixing: Weigh out the following according to the proportions: cement, remaining fly ash, zeolite powder, saturated coarse aggregate treated with S3 and saturated recycled fine aggregate, washed sand and mud fine aggregate, manufactured sand, and remaining water-reducing agent; the total mixing water is 160-162 kg / m³. 3 After deducting the activation water of S1 and the saturated water absorption of aggregate in S3, the remaining mixing water is obtained; after the weighed dry materials are premixed evenly, the remaining mixing water, the remaining water-reducing agent and the composite suspension prepared in S2 are added, and the mixture is stirred thoroughly to obtain a homogeneous concrete mixture. S5. Molding and curing: Pour the mixture obtained in S4 into a mold, vibrate to compact it, and then cover it with a film at 18-22℃ and let it stand to cure until hardened.
[0021] Furthermore, during the high-shear treatment process, the activated and extended polyacrylamide molecular chains in the washed sand and mud fine powder are simultaneously adsorbed onto the surface of fly ash particles and the surface of washed sand and mud fine powder particles through hydrogen bonds and van der Waals forces. This anchors and wraps the washed sand and mud fine powder particles around the fly ash particles, forming a micron-sized composite agglomerate with fly ash as the core and the washed sand and mud fine powder-polyacrylamide composite layer as the shell.
[0022] Furthermore, in S1, the nonionic surfactant aqueous solution is an alkylphenol polyoxyethylene ether aqueous solution; in S5, the covering film static curing should begin immediately after the pouring and vibration compaction process is completed, and no external watering operation of any kind, including but not limited to sprinkling and spraying, should be carried out on the concrete specimens or components during the entire curing period.
[0023] Compared with the prior art, the present invention has the following beneficial effects: 1. The degree of synergy in solid waste resource utilization is high, and the overall cost is significantly reduced.
[0024] This invention achieves a precise match between the characteristics of solid waste and the performance requirements of concrete by synergistically blending and functionalizing three types of solid waste: washed sand sludge, recycled aggregate from waste concrete, and high-titanium slag. Residual polyacrylamide (PAM) in the washed sand sludge is activated and utilized as an internal curing functional component; the recycled aggregate and high-titanium slag replace natural sand and gravel and conventional crushed stone, respectively. Through this system, the proportion of solid waste raw materials in each cubic meter of concrete can reach over 66%, significantly reducing the consumption of natural sand and cement, directly saving raw material costs, and effectively solving the land occupation and environmental pollution problems caused by the stockpiling of related industrial solid waste, thus achieving outstanding economic and environmental benefits.
[0025] 2. Excellent internal self-maintenance performance, significantly reducing reliance on and cost of external maintenance.
[0026] This invention constructs a synergistic internal curing system consisting of "PAM molecules locking in water - dual aggregates absorbing and releasing water - zeolite powder assisting in water retention". On one hand, the activated and expanded long chains of PAM in the washed sand can strongly adsorb and anchor water in the concrete matrix; on the other hand, highly absorbent recycled aggregates (saturated water absorption rate of 10.9%) and high-titanium slag (water absorption rate of 8.8%) can pre-store a large amount of water and release it continuously and slowly as the internal humidity decreases during cement hydration; simultaneously, the added zeolite powder has a natural porous adsorption structure, which can not only adsorb and store some water itself, but also regulate the water release rate through its pore structure, forming a synergistic water retention effect with PAM molecules and dual aggregates, further extending the water supply cycle. The synergy of these three elements achieves precise self-curing throughout the entire cycle from water adsorption and storage to slow release. This system eliminates the need for external water spraying or the addition of expensive superabsorbent polymer (SAP) and other water-retaining agents during the concrete hardening process, making it particularly suitable for engineering scenarios with limited curing conditions or high curing costs, such as drought, water shortage, and high-altitude operations.
[0027] 3. Mechanical properties and durability are improved in synergy, enhancing structural reliability.
[0028] This invention, through the optimized combination of functional components, achieves self-curing and solid waste utilization while ensuring and improving the overall performance of concrete. High-strength, dense high-titanium slag, used as coarse aggregate, enhances the skeletal strength and load-bearing capacity of the concrete. The rational gradation of recycled aggregate and high-titanium slag, combined with the pozzolanic activity of fly ash, zeolite powder, and washed sand powder, effectively fills and refines the pore structure inside the concrete, improving the density of the matrix. Therefore, the resulting concrete not only possesses stable mechanical properties but also exhibits excellent crack resistance and long-lasting internal humidity retention (28-day internal relative humidity ≥85%), ensuring the long-term durability and safety of the structure. Detailed Implementation
[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.
[0030] In this embodiment, the fine aggregate is composed of washed sand and mud fine aggregate with a particle size of 0.075-0.15mm, recycled fine aggregate with a particle size of 0.15-1.18mm, and manufactured sand with a particle size of 1.18-4.75mm in a mass ratio of 1:4.41:4.59.
[0031] In this embodiment, the recycled fine aggregate is obtained from waste concrete through crushing, screening, and washing, with a saturated water absorption rate of 10.9% and an apparent density of 2303 kg / m³. 3 The saturated water absorption rate of the manufactured sand is 1.3%, and its apparent density is 2640 kg / m³. 3 .
[0032] In this embodiment, the coarse aggregate is continuously graded high-titanium slag crushed stone with a particle size of 5-20mm, a water absorption rate of 8.8%, a mud content of 0.3%, a crushing value of 9.1%, and an apparent density of 3098kg / m³. 3 The bulk density is 2001 kg / m³. 3 .
[0033] In this embodiment, the cement is ordinary Portland cement (PO42.5 cement) with a strength grade of 42.5.
[0034] In this embodiment, the water-reducing agent is a polycarboxylate high-performance water-reducing agent with a water reduction rate of more than 30% and a solid content of 40%.
[0035] In this embodiment, the fly ash is Class I fly ash with an activity index of 88% after 28 days.
[0036] In this embodiment, the zeolite powder is finely ground zeolite powder with a particle size of 180 μm, a water absorption rate of 5.52%, and a loss on ignition of 12.18%.
[0037] In this embodiment, the preparation method includes the following steps: S1. Slurry activation and composite suspension preparation: Washed sand mud fine powder and water were mixed at a mass ratio of 1:4, simply stirred with a glass rod, sealed, and stirred in a magnetic stirrer for 10 min. Then, the mixture was placed in a heatable shearing tank and stirred continuously for 20 min under shear conditions of 48℃ and 2000 rpm to obtain an activated slurry. A portion of fly ash was taken, and it was sprayed with 0.5% of the mass of the fly ash in an alkylphenol polyoxyethylene ether aqueous solution. Then, it was gradually added to the activated slurry on the magnetic stirrer at a dry basis mass ratio of 1.5:1 and stirred continuously. The mixture was then transferred to a high-shear homogenizer and subjected to high-shear treatment at 15000 rpm for 15 min to form a washed sand mud-fly ash composite suspension. S2. Adjustment of suspension performance: Add water-reducing agent to the composite suspension. The dosage of water-reducing agent is 0.6% of the total dry basis of fly ash and washed sand mud powder in the composite suspension. Then adjust the Marsh funnel viscosity of the composite suspension to 40-60 seconds. S3. Pre-treatment of aggregates with water saturation: Soak the coarse high-titanium slag crushed stone and the recycled fine aggregate in the fine aggregate until they are saturated with water, take them out and wipe off the surface moisture to obtain saturated coarse aggregate and saturated recycled fine aggregate for later use. S4. Batching and Mixing: Weigh out the following according to the proportions: cement, remaining fly ash, zeolite powder, saturated coarse aggregate treated with S3 and saturated recycled fine aggregate, washed sand and mud fine aggregate, manufactured sand, and remaining water-reducing agent; the total mixing water is 160-162 kg / m³. 3 After deducting the activation water consumption of S1 and the saturated water absorption of aggregates in S3, the remaining mixing water is obtained. Weigh out the cement, the remaining fly ash and zeolite powder and mix them evenly in a mixer; then add the weighed saturated coarse aggregate, saturated recycled fine aggregate, washed sand and mud fine aggregate and manufactured sand and continue mixing to obtain a mixed dry material; after the remaining water-reducing agent and the remaining mixing water are fully mixed evenly, add them to the mixed dry material and continue mixing, then add the composite suspension prepared by S2 and mix thoroughly to obtain a homogeneous concrete mixture; S5. Molding and Curing: Pour the mixture obtained in S4 into the mold, vibrate to compact, and then cover with a film and allow to cure in an environment of 18-22℃ until hardened. The film-covered curing should begin immediately after the pouring and vibration compaction process, and no external watering operations of any kind, including but not limited to sprinkling and spraying, should be performed on the concrete specimens or components during the entire curing period.
[0038] Example 1. As a preferred embodiment of the present invention, the specific composition of the low-cost self-curing concrete of this embodiment is shown in Table 1.
[0039] Table 1
[0040] Example 2. As a preferred embodiment of the present invention, the specific composition of the low-cost self-curing concrete of this embodiment is shown in Table 2.
[0041] Table 2
[0042] Example 3. As a preferred embodiment of the present invention, the specific composition of the low-cost self-curing concrete of this embodiment is shown in Table 3.
[0043] Table 3
[0044] To verify the effectiveness of this invention, the following comparative tests were conducted: Comparative Example 1: Ordinary concrete, without solid waste aggregate and internal curing components, using natural sand and gravel, and conventionally water-cured. The specific composition is shown in Table 4.
[0045] Table 4
[0046] Comparative Example 2: Adding 3.8 kg / m 3Concrete using sodium polyacrylate superabsorbent polymer (SAP) as an internal curing agent, with natural sand and gravel, and conventional water curing, has the specific composition shown in Table 5.
[0047] Table 5
[0048] The fine aggregate used in Comparative Example 1 and Comparative Example 2 was manufactured sand with an apparent density of 2623 kg / m³. 3 The fineness modulus is 2.8; the coarse aggregate used is crushed stone with a particle size of 5-20 mm and an apparent density of 2600 kg / m³. 3 The crushing value was 7.5%, and the water absorption rate after 24 hours was 1.6%. The SAP used in Comparative Example 2 was a water-absorbing resin, the main component of which was sodium polyacrylate, a white powder with a particle size of 110 μm.
[0049] Test examples. The following tests were conducted on the concrete of each embodiment and comparative example: (1) Compressive strength test: The compressive strength of concrete specimens cured for 28 days was tested according to GB / T50081 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete".
[0050] (2) Early crack resistance of concrete: The test was conducted according to standard GB / T50082 "Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete". After the specimens were molded for 30 minutes, they were moved to an environment with a temperature of (20±2)℃ and a relative humidity of (60±5)%. The fan was immediately adjusted so that the wind speed at 100mm directly above the center of the specimen surface reached (5±0.5) m / s, and the wind direction was required to be parallel to the specimen surface and the crack inducing device. The test time was calculated from the time the concrete was watered, and the crack area was measured after 24 hours.
[0051] (3) Relative humidity test inside concrete: The relative humidity inside concrete is measured using a temperature and humidity sensor. The test uses a 100mm×100mm×100mm test block. When the concrete is being formed, a plastic tube with an inner diameter of 6mm is pre-embedded in the center of the concrete. A stainless steel bar with a diameter of 6mm is inserted into the tube so that the inner wall of the plastic tube is in close contact with the steel bar. The length of the steel bar extends 10mm beyond the top and bottom of the plastic tube. After initial setting, the steel bar is slowly pulled out and immediately sealed with a rubber stopper. The contact surface between the outside of the plastic tube and the mold is also sealed with sealant to prevent gas exchange due to the gap between the tube and the mold. When conducting the humidity test, a wedge-shaped rubber sleeve is pre-installed on the temperature and humidity probe rod. The rubber stopper is quickly removed and the probe is inserted. The plastic tube opening is then sealed with the wedge-shaped rubber sleeve. The value is read after the displayed humidity value stabilizes.
[0052] The test results of the concrete in each embodiment and comparative example are shown in Table 6.
[0053] Table 6
[0054] The internal relative humidity of all embodiments (1-3) of the present invention remained above 85% for 28 days, which was significantly higher than that of Comparative Example 1 (72%) without effective internal curing measures, and also superior to that of Comparative Example 2 (80%) with the addition of expensive SAP. This indicates that the "PAM water-locking-aggregate water-storage" system constructed in this invention can maintain the internal moisture environment of concrete in a long-term and effective manner.
[0055] The early cracking area in each embodiment of the present invention is much lower than that in Comparative Example 1 (reduced by more than 80%), and is on the same order of magnitude as or even better than that in Comparative Example 2. This is due to the continuous supply of internal moisture, which effectively inhibits drying shrinkage.
[0056] With the extensive use of solid waste (accounting for >66%) and without the addition of expensive SAP, the 28-day compressive strength (44.0-45.9 MPa) of the concrete of this invention is comparable to that of the benchmark concrete using natural aggregate and conventional curing (Comparative Example 1, 45.4 MPa). Although it is slightly lower than that of the concrete with added SAP (Comparative Example 2, 47.3 MPa), considering the reduction in cost, utilization of solid waste and self-curing efficiency, this invention achieves an excellent balance between performance and cost.
[0057] Example 2 demonstrates optimal overall performance (high humidity, low cracking), proving the effectiveness of the optimized formulation. This invention, through unique raw material processing and formulation design, successfully achieves synergistic effects of high-value utilization of solid waste, improved self-curing efficiency, and guaranteed mechanical properties.
[0058] In summary, the low-cost self-curing concrete prepared by this invention achieves efficient activation of residual PAM through the graded utilization of washed sand and mud. Combined with the high water absorption characteristics of recycled aggregates and the high strength advantage of high-titanium slag, a synergistic system of "PAM water locking - dual aggregate water absorption and slow release - solid waste gradation enhancement" is constructed, achieving a win-win situation of synergistic utilization of solid waste resources and improved concrete performance. This concrete requires no additional water curing, significantly reducing production costs. It possesses excellent mechanical properties, crack resistance, and durability, making it particularly suitable for engineering scenarios with limited curing conditions, such as drought and outdoor environments. Simultaneously, it significantly reduces industrial solid waste, aligning with the trend of green building development and possessing extremely high value for widespread application.
[0059] Finally, it should be noted that the above embodiments are merely preferred embodiments of the present invention used to illustrate the technical solutions of the present invention, and are not intended to limit the invention, nor are they intended to limit the patent scope of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention. That is to say, any changes or refinements made to the main design concept and spirit of the present invention that are not of substantial significance, but whose technical problems are still consistent with the present invention, should be included within the protection scope of the present invention. In addition, the direct or indirect application of the technical solutions of the present invention to other related technical fields are similarly included within the patent protection scope of the present invention.
Claims
1. A low-cost self-curing concrete, characterized in that, Each cubic meter of concrete includes the following raw materials: Cement: 266-304 kg / m³; Fly ash: 50-76 kg / m³; Washed sand and mud fine powder: 13-25 kg / m³; Zeolite powder: 13-25 kg / m³; Fine aggregate: 785-811 kg / m³; Coarse aggregate: 1057-1083 kg / m³; Water-reducing agent: 4.18-4.56 kg / m³; Water: 160-162 kg / m³; Among them, the fine aggregate is composed of washed sand and mud fine aggregate, recycled fine aggregate and manufactured sand in a mass ratio of 1:(4-5):(4-5); The coarse aggregate is continuously graded high-titanium slag crushed stone; Both the fine powder and fine aggregate of washed sand mud are derived from the mud slurry generated during the washing process of manufactured sand. They are obtained by drying, screening and grading. The fine powder of washed sand mud contains residual anionic or nonionic polyacrylamide. The polyacrylamide molecular chains in the washed sand and mud fine powder are stretched out through shearing and mixing treatment and combine with some fly ash to form micron-sized composite aggregates in concrete.
2. The low-cost self-curing concrete according to claim 1, characterized in that, Micron-sized composite aggregates have a structure with fly ash particles as the core and washed sand mud powder with adsorbed extended polyacrylamide molecular chains as the shell.
3. The low-cost self-curing concrete according to claim 1, characterized in that, The particle size of the fine powder of washed sand and mud is no greater than 0.075mm, and the particle size of the fine aggregate of washed sand and mud is 0.075-0.15mm.
4. The low-cost self-curing concrete according to claim 1, characterized in that, The particle sizes of recycled fine aggregate and manufactured sand are 0.15-1.18 mm and 1.18-4.75 mm, respectively.
5. The low-cost self-curing concrete according to claim 1, characterized in that, The continuously graded high-titanium slag crushed stone has a particle size of 5-20 mm, a water absorption rate of 8.8%, a mud content of 0.3%, a crushing value of 9.1%, and an apparent density of 3098 kg / m³. 3 The bulk density is 2001 kg / m³. 3 .
6. The low-cost self-curing concrete according to claim 1, characterized in that, The recycled fine aggregate is obtained from waste concrete through crushing, screening, and washing. It has a saturated water absorption rate of 10.9% and an apparent density of 2303 kg / m³. 3 The saturated water absorption rate of the manufactured sand is 1.3%, and its apparent density is 2640 kg / m³. 3 .
7. The low-cost self-curing concrete according to claim 1, characterized in that, The cement is ordinary Portland cement with a strength grade of 42.5; the water-reducing agent is a polycarboxylate high-performance water-reducing agent with a water reduction rate of more than 30% and a solid content of 40%; the fly ash is Grade I fly ash with a 28-day activity index of 88%; the zeolite powder has a particle size of 180μm, a water absorption rate of 5.52%, and a loss on ignition of 12.18%.
8. A method for preparing low-cost self-curing concrete according to any one of claims 1-7, characterized in that, Includes the following steps: S1. Slurry activation and composite suspension preparation: Washed sand mud fine powder and water are mixed at a mass ratio of 1:(3-5) and stirred continuously for 15-25 min under shear conditions of 40-50℃ and 1500-2500 rpm to obtain activated slurry; Take a portion of fly ash, spray it with 0.3-0.7% of the mass of the fly ash nonionic surfactant aqueous solution, and gradually add it to the activated slurry at a dry basis mass ratio of (1.2-1.8):1, and perform high shear treatment at 12000-18000 rpm for 10-20 min to form washed sand mud-fly ash composite suspension; S2. Adjustment of suspension performance: Add water-reducing agent to the composite suspension. The dosage of water-reducing agent is 0.4-0.8% of the total dry basis of fly ash and washed sand mud powder in the composite suspension. Then adjust the Marsh funnel viscosity of the composite suspension to 35-65 seconds. S3. Pre-treatment of aggregates with water saturation: Soak the coarse high-titanium slag crushed stone and the recycled fine aggregate in the fine aggregate until they are saturated with water, take them out and wipe off the surface moisture to obtain saturated coarse aggregate and saturated recycled fine aggregate for later use. S4. Batching and Mixing: Weigh out the following according to the proportions: cement, remaining fly ash, zeolite powder, saturated coarse aggregate treated with S3 and saturated recycled fine aggregate, washed sand and mud fine aggregate, manufactured sand, and remaining water-reducing agent; the total mixing water is 160-162 kg / m³. 3 After deducting the activation water of S1 and the saturated water absorption of aggregate in S3, the remaining mixing water is obtained; after the weighed dry materials are premixed evenly, the remaining mixing water, the remaining water-reducing agent and the composite suspension prepared in S2 are added, and the mixture is stirred thoroughly to obtain a homogeneous concrete mixture. S5. Molding and curing: Pour the mixture obtained in S4 into a mold, vibrate to compact it, and then cover it with a film at 18-22℃ and let it stand to cure until hardened.
9. The method for preparing a low-cost self-curing concrete according to claim 8, characterized in that, During the high-shear treatment process, the activated and extended polyacrylamide molecular chains in the washed sand and mud fine powder are simultaneously adsorbed onto the surface of fly ash particles and the surface of washed sand and mud fine powder particles through hydrogen bonds and van der Waals forces. This anchors and wraps the washed sand and mud fine powder particles around the fly ash particles, forming a micron-sized composite agglomerate with fly ash as the core and the washed sand and mud fine powder-polyacrylamide composite layer as the shell.
10. The method for preparing a low-cost self-curing concrete according to claim 8, characterized in that, In S1, the nonionic surfactant aqueous solution is an alkylphenol polyoxyethylene ether aqueous solution; in S5, the covering film static curing should begin immediately after the pouring and vibration compaction process is completed, and no external watering operation of any kind, including but not limited to sprinkling and spraying, should be carried out on the concrete specimens or components during the entire curing period.