Dry-mixed rapid-setting mortar for road surface repair and preparation process thereof

Abstract

This application relates to the field of building materials technology, and discloses a dry-mixed quick-setting mortar for road repair and its preparation process. The mortar is made from a ternary cementitious system composed of sulfoaluminate cement, rapid-hardening silicate cement, and high-belite sulfoaluminate cement, combined with temperature-sensitive microporous mineral composite functional particles, graded fine sand, active admixtures, nano-calcium carbonate, quick-setting agent, and polypropylene fiber. The preparation process employs a two-step mixing process of low-speed premixing and secondary high-speed shear mixing. This invention utilizes the stepped hydration exothermic mechanism of the ternary cementitious system combined with the targeted slow-release mechanism of the temperature-sensitive particles to achieve adaptive control of setting time across the entire temperature range, overcoming the defect of uncontrolled hydration rate under extreme temperature differences. The resulting mortar possesses high early-stage strength and non-regressive later-stage strength, while exhibiting low drying shrinkage and high bonding strength between new and old interfaces, meeting the requirements for rapid all-weather road repair and long-term service.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a dry-mixed quick-setting mortar for road repair and its preparation process. Background Technology

[0002] With the continuous development of transportation infrastructure, the maintenance and emergency repair of damaged roads require repair materials to reach traffic-ready strength within a short period of time. Existing rapid road repair materials typically employ pure sulfoaluminate cement systems or ordinary silicate cement combined with accelerators. These conventional materials are highly sensitive to changes in ambient temperature during actual construction. In high-temperature environments, early hydration heat release is concentrated, easily leading to premature setting and causing the mortar to quickly lose its fluidity, leaving construction workers with insufficient working time. In low-temperature environments, especially below zero degrees Celsius, the reduced activation energy of the liquid phase slows down the hydration reaction, significantly prolonging the final setting time and failing to meet the requirements for ultra-early load-bearing capacity, while also easily causing early frost damage. Conventional chemical accelerators often cannot simultaneously control the setting time under large-scale high and low temperature conditions.

[0003] In terms of the evolution of mechanical properties, existing rapid-setting repair materials generally suffer from a decline in strength in the later stages. Systems primarily composed of pure sulfoaluminate cement provide early strength through the rapid formation of ettringite crystals during the initial mixing phase. However, in the later stages of hydration, as free water within the system is consumed, stress concentration and microcrack initiation easily occur at crystal overlaps. This localized damage to the microstructure reduces the overall density of the hardened paste, causing the material's later strength to fail to increase further or even decrease, thus affecting the long-term load-bearing capacity of the repaired structure.

[0004] Furthermore, during the rapid curing process of traditional quick-setting mortar, the negative pressure caused by water consumption in the internal capillaries leads to significant drying shrinkage. This volumetric deformation translates into interlayer shear stress on the confined surface of the old concrete base. In addition, conventional preparation and mixing processes struggle to achieve sufficient deagglomeration and uniform dispersion of various fine powders and functional admixtures, resulting in defects within the matrix. Under the continuous action of shrinkage stress, delamination easily occurs at the interface between the new and old materials, causing the repair layer to detach and compromising the long-term durability of the road repair project. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a dry-mixed quick-setting mortar for road repair and its preparation process. It solves the problems of uncontrolled hydration reaction rate in existing road repair mortars under extreme environmental temperature differences, which makes it difficult to control the setting time, as well as the problems of reduced strength, large drying shrinkage rate, and easy peeling of new and old interfaces caused by structural defects in early hydration products in traditional quick-setting materials.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] In a first aspect, the present invention provides a dry-mixed quick-setting mortar for road repair, employing the following technical solution:

[0008] A dry-mix quick-setting mortar for road repair comprises the following components by weight percentage:

[0009] Sulfoaluminate cement: 25.0%~35.0%;

[0010] Rapid-hardening Portland cement: 15.0%~25.0%;

[0011] High belite sulfoaluminate cement: 10.0%~20.0%;

[0012] Graded fine sand: 20.0%~40.0%;

[0013] Active admixtures: 5.0%–10.0%;

[0014] Thermosensitive microporous mineral composite functional particles: 1.0%–2.5%;

[0015] Nano-calcium carbonate: 1.0%–3.0%;

[0016] Calcium aluminate quick-setting agent: 0.5%~1.5%;

[0017] Citric acid: 0.05%–0.1%;

[0018] Polypropylene fiber: 0.1%–0.3%;

[0019] Polycarboxylate superplasticizer: 0.5%–1.2%;

[0020] Cellulose ethers: 0.05%–0.15%;

[0021] Plasticizer: 0.1%~0.2%.

[0022] By adopting the above technical solution, and using a ternary cementing system composed of sulfoaluminate cement, rapid-hardening silicate cement and high-belite sulfoaluminate cement, combined with temperature-sensitive microporous mineral composite functional particles, adaptive regulation of hydration dynamics in the entire temperature range is achieved.

[0023] A segmented hydration regulation mechanism: The system utilizes the differences in hydration rates among different mineral phases to construct a stepped exothermic model. Initially, sulfoaluminate cement rapidly hydrates to generate ettringite crystals, constructing the early strength framework. The dicalcium mineral phase in high-belite sulfoaluminate cement intervenes in the middle of hydration, and the heat generated maintains the system's activity. Rapid-hardening silicate cement continues to hydrate in the later stages to generate calcium silicate gel, filling the micropores between the ettringite framework, avoiding structural defects caused by the excessively rapid growth of early products in a single system, and effectively solving the problem of later strength reduction.

[0024] Thermosensitive targeted sustained-release mechanism: Thermosensitive microporous mineral composite functional particles sense ambient temperature through their outer lipid-wax phase transition coating layer.

[0025] At low temperatures, the coating remains solid, blocking the internal excitation components and maintaining basic hydration by relying on the initial induction effect of the high belite phase.

[0026] When the ambient temperature rises or internal hydration heat accumulates, the phase change material melts, and lithium nitrate and triethanolamine in the microporous carrier are released into the liquid phase through the pores.

[0027] The released lithium ions act as nucleation inducing agents, reducing the nucleation potential energy of hydration products, accelerating the dissolution and precipitation equilibrium of mineral phases such as calcium aluminate, and compensating for the reactivity at low temperatures.

[0028] Meanwhile, triethanolamine complexes with aluminum ions in the liquid phase, regulating the ion migration rate and enabling the slurry to maintain the necessary construction consistency at high temperatures, thus preventing premature setting.

[0029] Microstructure reinforcement and volume stability control: Nano-calcium carbonate, acting as ultrafine nucleation units, is uniformly distributed in the slurry, providing numerous heterogeneous nucleation sites. Combined with the secondary pozzolanic reaction of active admixtures, free calcium hydroxide in the liquid phase is transformed into a dense calcium silicate gel network. Polypropylene fibers form a three-dimensionally randomly distributed reinforcing structure in the hardened body, synergistically dispersing drying shrinkage stress through a low-shrinkage gelation system, thereby improving the material's volume stability and interfacial bonding strength.

[0030] Therefore, a road repair material with excellent environmental adaptability, high early strength and no shrinkage in the later stage, strong interfacial bonding and low shrinkage rate was obtained.

[0031] Preferably, the active admixture is composed of metakaolin, silica fume and fly ash, and the mass ratio of metakaolin, silica fume and fly ash is 2:1:2.

[0032] By employing the above technical solution, graded filling was achieved using micro-powders of different particle sizes and activities. The high reactivity of metakaolin ensured compensation for early chemical shrinkage, silica fume filled the extremely fine pores, and fly ash improved the flow properties of the slurry. The combination of these three components formed a dense micro-filling system, enhancing the impermeability and durability of the mortar.

[0033] Preferably, the temperature-sensitive microporous mineral composite functional particles include a microporous mineral carrier, a composite activation liquid loaded in the pores of the microporous mineral carrier, and a phase change coating covering the outer surface of the microporous mineral carrier; the microporous mineral carrier is natural clinoptilolite powder that has undergone calcination and activation treatment; the composite activation liquid is a mixture of lithium nitrate and triethanolamine in a mass ratio of 2.8 to 3.2; the phase change coating is a mixture of stearic acid and paraffin wax, and the mass ratio of stearic acid to paraffin wax is 0.8 to 1.2.

[0034] By employing the above technical solutions, natural clinoptilolite, after calcination and activation, opens up a large number of internal channels, providing a large specific surface area for adsorbing the composite activation liquid. The eutectic mixture formed by stearic acid and paraffin has a precise phase transition range, enabling sensitive physical state switching for the typical temperature range of road repair (especially the critical temperature range crossing the freezing point). The synergistic effect of lithium nitrate and triethanolamine can both promote the dissolution of early silicate mineral phases and regulate the precipitation rate of aluminate mineral phases, ensuring the balance of catalytic effects.

[0035] Preferably, the strength grade of the sulfoaluminate cement, rapid-hardening silicate cement, and high-belite sulfoaluminate cement is not lower than 42.5, and the specific surface area is controlled at 380 m². 2 / kg~480m 2 The graded fine sand is between 2.3 and 2.8 kg / kg; the graded fine sand is dried and graded manufactured sand or natural sand, with a fineness modulus of 2.3 to 2.8, a mud content of less than 0.5 wt%, and a moisture content of less than 0.1 wt%; the average particle size of the nano-calcium carbonate is 20 nm to 80 nm, and its specific surface area is 20 m² / kg. 2 / g~40m 2 / g; The polypropylene fiber is a monofilament bundle fiber with a length of 6mm to 12mm and a diameter of 15μm to 30μm.

[0036] By adopting the above technical solutions, the precise limitation of the physical specifications of raw materials ensures the controllability of the hydration heat release kinetics of the cementitious materials. The gradation and fineness modulus of the fine sand guarantee the density and workability of the mortar. The high specific surface area of ​​nano-sized calcium carbonate greatly enhances its nucleation efficiency. The size setting of the polypropylene fibers allows them to play an efficient role in crack resistance in the mortar matrix without affecting the rheological behavior of the mortar.

[0037] Secondly, the present invention provides a preparation process for dry-mixed quick-setting mortar for road repair, which adopts the following technical solution:

[0038] A process for preparing dry-mixed quick-setting mortar for road repair includes the following steps:

[0039] According to the weight percentage ratio, separately weigh out sulfoaluminate cement, rapid-hardening silicate cement, high belite sulfoaluminate cement, active admixture, graded fine sand, temperature-sensitive microporous mineral composite functional particles, nano calcium carbonate, calcium aluminate quick-setting agent, citric acid, polypropylene fiber, polycarboxylate-based high-efficiency water-reducing agent, cellulose ether, and plasticizer.

[0040] The weighed sulfoaluminate cement, rapid-hardening silicate cement, high belite sulfoaluminate cement, active admixture, nano-calcium carbonate, temperature-sensitive microporous mineral composite functional particles, and graded fine sand are put into a mixing device and dry-mixed at the first speed to obtain a premixed material.

[0041] Continue to add the weighed polypropylene fiber, calcium aluminate quick-setting agent, citric acid, plasticizer, polycarboxylate-based high-efficiency water-reducing agent and cellulose ether to the mixing equipment containing the premixed materials. Raise the mixing equipment to the second speed for high-speed shearing and mixing. After the mixing is completed, discharge the material to obtain dry-mix quick-setting mortar for road repair.

[0042] Its mixing, dispersion, and microstructure assembly process are as follows:

[0043] Multi-scale powder collision and deagglomeration process: In the first premixing stage, cementitious materials, active admixtures, nano-calcium carbonate, and fine sand are mixed. Large-particle-size graded fine sand and cement particles serve as grinding media, generating physical collisions and friction under low-speed dry stirring. The mechanical kinetic energy between particles is transferred to the nano-calcium carbonate and active micro-powders, overcoming the van der Waals forces and electrostatic adsorption between ultrafine powders, thus de-agglomerating the powder. Temperature-sensitive microporous mineral composite functional particles flow with the large particles in this stage, avoiding direct exposure to high-intensity mechanical shearing and maintaining the physical integrity of the external wax coating layer.

[0044] High-energy dispersion process of admixtures and fibers: In the secondary high-speed shear mixing stage, polypropylene fibers and various chemical admixtures are added and the rotation speed is increased. The high-speed rotating mechanical unit establishes a strong shear stress field within the mixing equipment. Under the action of three-dimensional shear force, the polypropylene fibers undergo mechanical unbundling and are randomly distributed in the dry powder system. Trace chemical components such as calcium aluminate accelerator and water-reducing agent are uniformly adhered to the surface of cement particles and powder during high-speed airflow collision. The short-term high-energy input ensures the uniform concentration of trace chemical components in the macroscopic matrix and eliminates the defects of local chemical stress concentration.

[0045] Therefore, a dry-mixed material with high dispersion of each component, uniform particle size distribution and good functional particle activity was obtained, providing a material basis for the simultaneous occurrence of subsequent hydration reaction of mortar.

[0046] Preferably, the mixing equipment is a twin-shaft paddle mixer; the first rotation speed is controlled between 320 r / min and 380 r / min; the dry mixing time is controlled between 3 min and 5 min; the second rotation speed is controlled between 850 r / min and 1000 r / min; and the high-speed shear mixing time is controlled between 5 min and 8 min.

[0047] By employing the above technical solution, the biaxial impeller structure establishes a cross-convection and weightless boiling zone within the cylinder. The first rotational speed, combined with a time of 3 to 5 minutes, completes the macroscopic homogenization of bulk basic materials, while the heat generated by mechanical friction remains within a controllable range, below the phase transition melting point range of temperature-sensitive particles. The second rotational speed is increased to 850 to 1000 r / min, inputting high-intensity mechanical energy into the system within 5 to 8 minutes. These operating parameters are above the critical stress for polypropylene fiber unbundling and below the threshold for mechanical degradation of the powder material, achieving a balance between dispersion efficiency and process energy consumption.

[0048] Preferably, the active admixture is prepared by weighing and dry-mixing metakaolin, silica fume and fly ash in the corresponding mass ratio in advance, and then using it as a single mixing component; the graded fine sand is added into the mixing equipment all at once in the first pre-mixing stage.

[0049] By adopting the above technical solution, three types of volcanic ash micropowders with different fineness and surface energies are pre-homogenized, eliminating the segregation tendency caused by differences in powder specific gravity and forming an auxiliary cementitious material phase with consistent composition. Graded fine sand is fully added during the pre-mixing stage, ensuring a constant aggregate quantity within the mixing equipment throughout the process, thus improving the mechanical dispersion and grinding efficiency for subsequently added ultrafine powders.

[0050] Preferably, the relative humidity of the environment during the primary premixing and secondary high-speed shear mixing processes is controlled below 45%, and during the secondary high-speed shear mixing stage, the loading volume of the material in the mixing equipment is controlled to be 50% to 60% of the effective volume of the mixer.

[0051] By adopting the above technical solutions, the relative humidity of the production environment is controlled below the critical value, cutting off the early contact path between air moisture and rapid-hardening silicate cement and the high-belite phase, preventing agglomeration and activity reduction on the material surface due to micro-hydration. Limiting the loading volume to 50% to 60% preserves sufficient space for material throwing and exchange within the mixing equipment. This spatial dimension ensures the free flight trajectory of powder particles, allowing mechanical shear force to completely penetrate the material bed and eliminating mixing dead zones within the equipment.

[0052] This invention provides a dry-mixed, quick-setting mortar for road repair and its preparation process. It has the following beneficial effects:

[0053] 1. This invention achieves stable control of setting time under varying environmental temperature ranges by introducing temperature-sensitive microporous mineral composite functional particles in synergistic action with a ternary cementing system containing sulfoaluminate, fast-hardening silicate, and high-belite sulfoaluminate. In low-temperature environments, the wax phase change layer on the outer layer of the functional particles melts, directionally releasing lithium nitrate and triethanolamine activating components to accelerate hydration; in high-temperature environments, the coating layer remains stable, and the zeolite carrier adsorbs excess ions to delay the reaction. This ensures that the final setting time of the mortar remains stable between 27 and 32.5 minutes within an environmental temperature range of -5℃ to 40℃, solving the construction problems of slow low-temperature reaction and rapid setting at high temperatures associated with traditional repair materials.

[0054] 2. This invention utilizes the stepwise hydration exothermic mechanism of a ternary cementitious system combined with nano-calcium carbonate and active admixtures to solve the technical defect of reduced strength in the later stages of rapid-setting repair mortar. In the initial hydration stage, the sulfoaluminate phase rapidly generates an ettringite skeleton, enabling a compressive strength of over 20 MPa within 30 minutes, meeting the early traffic requirements for road repairs. In the middle and later stages of hydration, the continuous hydration of the rapid-hardening silicate cement and the secondary pozzolanic reaction of the active admixtures generate a large amount of calcium silicate gel, densely filling the pores between the early crystal skeletons. This ensures that the compressive strength continues to climb to over 65 MPa within 28 days, avoiding the hardening matrix deterioration caused by microcracks in traditional pure sulfoaluminate systems.

[0055] 3. This invention employs a two-step gradient mixing process combined with polypropylene fibers, improving the volume stability and interfacial bonding performance of the hardened mortar. The combination of low-speed premixing and secondary high-speed shear mixing ensures the integrity of the temperature-sensitive particle's physical structure, achieving highly uniform monofilament dispersion of ultrafine powder, water-reducing agent, and polypropylene fibers within the dry powder matrix. This uniformly dispersed material system effectively cuts off the capillary channels for internal moisture evaporation, controlling the 28-day drying shrinkage rate below 0.035% and reducing interlayer shrinkage stress. The failure surface in the pull-out test reaches deep into the original concrete substrate, overcoming the interfacial brittle peeling phenomenon that easily occurs in conventional repair layers. Attached Figure Description

[0056] Figure 1 This is a graph showing the release kinetics of the thermosensitive composite functional particles of the present invention.

[0057] Figure 2 This is a diagram showing the hydration heat release rate of the dry-mixed quick-setting mortar of the present invention.

[0058] Figure 3 This is a graph showing the setting time variation of the dry-mixed quick-setting mortar across the entire temperature range.

[0059] Figure 4 The graphs show the evolution of compressive strength of each group of mortar samples as a function of age.

[0060] Figure 5 This is a comparison chart of the interfacial bond strength and drying shrinkage rate of each group of mortar samples in this invention after 28 days. Detailed Implementation

[0061] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to test examples. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0062] Preparation Examples 1-4:

[0063] Preparation Example 1:

[0064] This preparation example provides a method for preparing thermosensitive microporous mineral composite functional particles, including the following steps:

[0065] (1) Activation of substrate: Natural clinoptilolite powder was selected, calcined at 300℃ for 2 hours, and then placed in a desiccator to cool to room temperature;

[0066] (2) Vacuum impregnation: The activated zeolite powder is placed in a vacuum impregnation machine, and a vacuum is drawn to a pressure of -0.09 MPa and maintained for 25 min; then, a composite activation liquid is introduced at a mass ratio of 100:25 between zeolite powder and composite activation liquid. The composite activation liquid is a mixture of lithium nitrate and triethanolamine at a mass ratio of 3:1; the pressure is restored to normal and stirred at 50 r / min for 30 min.

[0067] (3) Phase change coating: Weigh 15% of the mass of stearic acid and paraffin wax mixture, wherein the mass ratio of stearic acid to paraffin wax is 1:1, and heat to 70°C to molten state; preheat the loaded zeolite powder to 48°C in a high-speed mixer, and uniformly spray the molten coating material through an atomizing nozzle, controlling the cooling rate to 3°C / min, to obtain composite functional particles with a particle size of 45μm to 100μm.

[0068] Preparation Example 2:

[0069] This preparation example provides a method for preparing thermosensitive microporous mineral composite functional particles, including the following steps:

[0070] (1) Activation of substrate: Natural clinoptilolite powder was selected, calcined at 280℃ for 2.5h, and then placed in a desiccator to cool to room temperature;

[0071] (2) Vacuum impregnation: The activated zeolite powder was placed in a vacuum impregnation machine, and a vacuum was drawn to a pressure of -0.095 MPa and maintained for 30 min; then, the composite activation liquid was introduced at a mass ratio of 100:20 between the zeolite powder and the composite activation liquid. The composite activation liquid was made by mixing lithium nitrate and triethanolamine at a mass ratio of 2.8:1.2; the pressure was restored to normal and the mixture was stirred at a speed of 40 r / min for 40 min.

[0072] (3) Phase change coating: Weigh 12% of the mass of stearic acid and paraffin wax mixture, wherein the mass ratio of stearic acid to paraffin wax is 0.8:1.2, and heat to 65°C to molten state; preheat the loaded zeolite powder to 45°C in a high-speed mixer, and uniformly spray the molten coating material through an atomizing nozzle, controlling the cooling rate to 2°C / min, to obtain composite functional particles with a particle size of 45μm to 80μm.

[0073] Preparation Example 3:

[0074] This preparation example provides a method for preparing thermosensitive microporous mineral composite functional particles, including the following steps:

[0075] (1) Activation of substrate: Natural clinoptilolite powder was selected, calcined at 320℃ for 1.5h, and then placed in a desiccator to cool to room temperature;

[0076] (2) Vacuum impregnation: The activated zeolite powder was placed in a vacuum impregnation machine, and a vacuum was drawn to a pressure of -0.085 MPa and maintained for 20 min; then, a composite activation liquid was introduced at a mass ratio of 100:30 between the zeolite powder and the composite activation liquid. The composite activation liquid was made by mixing lithium nitrate and triethanolamine at a mass ratio of 3.2:0.8; the pressure was restored to normal and the mixture was stirred at a speed of 60 r / min for 25 min.

[0077] (3) Phase change coating: Weigh 18% of the mass of stearic acid and paraffin wax mixture, where the mass ratio of stearic acid to paraffin wax is 1.2:0.8, and heat to 75°C to molten state; preheat the loaded zeolite powder to 50°C in a high-speed mixer, and uniformly spray the molten coating material through an atomizing nozzle, controlling the cooling rate to 5°C / min, to obtain composite functional particles with a particle size of 60μm to 100μm.

[0078] Preparation Example 4:

[0079] This preparation example provides a method for preparing thermosensitive microporous mineral composite functional particles, including the following steps:

[0080] (1) Activation of substrate: Natural clinoptilolite powder was selected, calcined at 310℃ for 2 hours, and then placed in a desiccator to cool to room temperature;

[0081] (2) Vacuum impregnation: The activated zeolite powder is placed in a vacuum impregnation machine, and a vacuum is drawn to a pressure of -0.092 MPa and maintained for 25 min; then, a composite activation liquid is introduced at a mass ratio of 100:22 between zeolite powder and composite activation liquid. The composite activation liquid is a mixture of lithium nitrate and triethanolamine at a mass ratio of 3:1; the pressure is restored to normal and stirred at 55 r / min for 35 min.

[0082] (3) Phase change coating: Weigh 14% of the mass of stearic acid and paraffin wax mixture, wherein the mass ratio of stearic acid to paraffin wax is 1:1, and heat to 68°C to molten state; preheat the loaded zeolite powder to 46°C in a high-speed mixer, and uniformly spray the molten coating material through an atomizing nozzle, controlling the cooling rate to 4°C / min, to obtain composite functional particles with a particle size of 50μm to 90μm.

[0083] Examples 1-5:

[0084] Example 1:

[0085] This embodiment provides a method for preparing dry-mixed quick-setting mortar for road repair, including the following steps:

[0086] (1) Ingredients: Weigh the raw materials according to the mass percentage, including 30.0% sulfoaluminate cement, 20.0% rapid-hardening silicate cement, 15.0% high belite sulfoaluminate cement, 5.0% active admixture (2.0% metakaolin, 1.0% silica fume, 2.0% fly ash), 1.5% composite functional particles obtained in Preparation Example 1, 1.5% nano calcium carbonate, 25.32% graded fine sand, 0.7% calcium aluminate quick-setting agent, 0.08% citric acid, 0.2% polypropylene fiber, 0.5% polycarboxylate superplasticizer, 0.1% cellulose ether, and 0.1% plasticizer;

[0087] (2) First-time premixing: The above-mentioned cement, active admixture, graded fine sand, nano calcium carbonate and composite functional particles are put into a twin-shaft paddle mixer and stirred at 350 r / min for 4 min.

[0088] (3) Secondary high-speed shear mixing: continue to add polypropylene fiber, quick-setting agent, citric acid, plasticizer, water-reducing agent and cellulose ether into the mixer, increase the speed to 900 r / min, and continue to stir for 6 min to obtain dry-mixed quick-setting mortar.

[0089] Example 2:

[0090] This embodiment provides a method for preparing dry-mixed quick-setting mortar for road repair, including the following steps:

[0091] (1) Ingredients: Weigh the raw materials according to the mass percentage, including 25.0% sulfoaluminate cement, 15.0% rapid-hardening silicate cement, 10.0% high belite sulfoaluminate cement, 10.0% active admixture (4.0% metakaolin, 2.0% silica fume, 4.0% fly ash), 2.5% composite functional particles obtained in Preparation Example 2, 3.0% nano calcium carbonate, 31.45% graded fine sand, 1.5% calcium aluminate quick-setting agent, 0.05% citric acid, 0.3% polypropylene fiber, 1.0% polycarboxylate superplasticizer, 0.05% cellulose ether, and 0.15% plasticizer;

[0092] (2) First-time premixing: The above-mentioned cement, active admixture, graded fine sand, nano calcium carbonate and composite functional particles are put into a twin-shaft paddle mixer and stirred at 320 r / min for 5 min.

[0093] (3) Secondary high-speed shear mixing: continue to add polypropylene fiber, quick-setting agent, citric acid, plasticizer, water-reducing agent and cellulose ether into the mixer, increase the speed to 850 r / min, and continue to stir for 8 min to obtain dry-mixed quick-setting mortar.

[0094] Example 3:

[0095] This embodiment provides a method for preparing dry-mixed quick-setting mortar for road repair, including the following steps:

[0096] (1) Ingredients: Weigh the raw materials by mass percentage, including 26.0% sulfoaluminate cement, 16.0% rapid-hardening silicate cement, 12.0% high belite sulfoaluminate cement, 5.0% active admixture (2.0% metakaolin, 1.0% silica fume, 2.0% fly ash), 1.0% composite functional particles obtained in Preparation Example 3, 1.0% nano calcium carbonate, 36.8% graded fine sand, 0.5% calcium aluminate quick-setting agent, 0.1% citric acid, 0.1% polypropylene fiber, 1.2% polycarboxylate superplasticizer, 0.15% cellulose ether, and 0.15% plasticizer;

[0097] (2) First-time premixing: The above-mentioned cement, active admixture, graded fine sand, nano calcium carbonate and composite functional particles are put into a twin-shaft paddle mixer and stirred at 380 r / min for 3 min.

[0098] (3) Secondary high-speed shear mixing: continue to add polypropylene fiber, quick-setting agent, citric acid, plasticizer, water-reducing agent and cellulose ether into the mixer, increase the speed to 950 r / min, and continue to stir for 5 min to obtain dry-mixed quick-setting mortar.

[0099] Example 4:

[0100] This embodiment provides a method for preparing dry-mixed quick-setting mortar for road repair, including the following steps:

[0101] (1) Ingredients: Weigh the raw materials according to the mass percentage, including 28.0% sulfoaluminate cement, 18.0% rapid-hardening silicate cement, 14.0% high belite sulfoaluminate cement, 8.0% active admixture (3.2% metakaolin, 1.6% silica fume, 3.2% fly ash), 2.0% composite functional particles obtained in Preparation Example 4, 2.0% nano calcium carbonate, 25.45% graded fine sand, 1.2% calcium aluminate quick-setting agent, 0.07% citric acid, 0.15% polypropylene fiber, 0.8% polycarboxylate superplasticizer, 0.13% cellulose ether, and 0.2% plasticizer;

[0102] (2) First-time premixing: The above-mentioned cement, active admixture, graded fine sand, nano calcium carbonate and composite functional particles are put into a twin-shaft paddle mixer and stirred at 340 r / min for 4.5 min;

[0103] (3) Secondary high-speed shear mixing: continue to add polypropylene fiber, quick-setting agent, citric acid, plasticizer, water-reducing agent and cellulose ether into the mixer, increase the speed to 880 r / min, and continue to stir for 7 min to obtain dry-mixed quick-setting mortar.

[0104] Example 5:

[0105] This embodiment provides a method for preparing dry-mixed quick-setting mortar for road repair, including the following steps:

[0106] (1) Ingredients: The ingredient ratio is the same as in Example 1;

[0107] (2) Premixing: Cement, active admixture, graded fine sand, nano calcium carbonate and composite functional particles are put into a twin-shaft paddle mixer and stirred for 3 min at a speed of 320 r / min;

[0108] (3) Secondary high-speed shear mixing: continue to add polypropylene fiber, quick-setting agent, citric acid, plasticizer, water-reducing agent and cellulose ether into the mixer, increase the speed to 1000 r / min, and continue to stir for 5 min to obtain dry-mixed quick-setting mortar.

[0109] Comparative Examples 1-6:

[0110] Comparative Example 1:

[0111] Compared with Example 1, the difference is that it does not contain high-belite sulfoaluminate cement, and the missing mass fraction is made up by an equal amount of sulfoaluminate cement, while the rest are the same.

[0112] Comparative Example 2:

[0113] Compared with Example 1, the difference is that it does not contain the composite functional particles obtained in Example 1. Instead, an equal mass of lithium nitrate and triethanolamine mixture (mass ratio of the two is 3:1) is directly added. The missing mass fraction of the carrier and coating material is made up by an equal amount of graded fine sand. All other aspects are the same.

[0114] Comparative Example 3:

[0115] The difference from Example 1 is that the functional particles used are those that were not coated with the phase change coating in step (3) after step (2) in Example 1, while the rest are the same.

[0116] Comparative Example 4:

[0117] Compared with Example 1, the difference is that it does not contain rapid-hardening silicate cement and high-belite sulfoaluminate cement. The missing mass fraction is made up by an equal amount of sulfoaluminate cement, and the rest are the same.

[0118] Comparative Example 5:

[0119] Compared with Example 1, the difference is that it does not contain the composite functional particles obtained in Preparation Example 1, and is replaced by an equal mass of commercially available aluminate quick-setting agent; otherwise, they are the same.

[0120] Comparative Example 6:

[0121] Compared with Example 1, the difference is that the stirring speed in step (3) is set to 350 r / min, and high-speed shear dispersion is not performed, while the rest are the same.

[0122] Test Examples 1-5:

[0123] Test Example 1:

[0124] Experimental Objective: This test case aims to verify the ion blocking and release characteristics of thermosensitive microporous mineral composite functional particles under different ambient temperatures. The experimental subjects are the composite functional particles obtained in Preparation Example 1 and the particles without phase change coating used in Comparative Example 3.

[0125] Experimental steps:

[0126] (1) Weigh 5.00 g each of the dried composite particles obtained in Preparation Example 1 and the uncoated particles used in Comparative Example 3, and place them in a dry petri dish for later use.

[0127] (2) Prepare four constant temperature jacketed glass reactors containing 500 mL of deionized water. The internal water temperature is precisely stabilized at 5℃, 20℃ and 40℃ respectively. The reactors are equipped with tetrafluoroethylene rotors. A magnetic stirrer is used to provide continuous fluid shear force at a constant speed of 250 r / min to simulate the dynamic environment of the actual mixing stage of mortar.

[0128] (3) The two types of particles were quickly put into deionized water at the corresponding temperatures and the timing system was started simultaneously. At 5 min, 10 min, 20 min, 30 min, 45 min and 60 min after feeding, the conductivity change of the liquid phase was recorded in real time using an immersion high-precision conductivity meter. The obtained conductivity value was converted into the cumulative release rate of the effective component in the system by using the pre-calibrated concentration-conductivity standard working curve.

[0129] Experimental results (see Table 1):

[0130] Table 1: Test data on the cumulative effective ion release rate of composite particles at different temperatures

[0131] Extraction time (min) Preparation Example 1 (Test at 5°C) Preparation Example 1 (Tested at 20℃) Preparation Example 1 (Tested at 40℃) Comparative Example 3 (20℃ Test) 5 2.13% 15.42% 42.67% 68.32% 10 3.51% 32.78% 65.11% 82.15% 20 5.26% 58.34% 81.43% 89.47% 30 6.84% 74.19% 88.75% 93.51% 45 8.42% 83.61% 92.28% 95.84% 60 9.74% 89.25% 94.56% 96.92%

[0132] Test conclusion:

[0133] Figure 1 This is a graph showing the release kinetics of the temperature-sensitive composite functional particles of this invention. Figure 1 The paper specifically shows the ion accumulation release rate of the composite functional particles obtained in Preparation Example 1 in a water environment at 5℃, 20℃, and 40℃, and compares the release trajectory of the free state particles without phase change coating used in Comparative Example 3 at 20℃.

[0134] According to the data in Table 1, the effective ion cumulative release rate of the composite functional particles obtained in Preparation Example 1 was only 9.74% within 60 minutes in a constant temperature water environment of 5℃. This long-term sealing performance in the low-temperature liquid phase directly reflects that the stearic acid and paraffin eutectic mixture maintains a dense solid shell morphology below its phase transition point, cutting off the capillary channels for the internal excitation liquid to diffuse to the surrounding water. Actual construction sites are often accompanied by complex environmental temperature differences. When the external reference temperature or the heat accumulation caused by the early weak hydration of cement in the local system causes the local temperature to exceed the phase transition threshold, the physical state of the coating material undergoes a fundamental change. As revealed by the test conditions of 20℃ and 40℃, the ion concentration in the liquid phase exhibits a non-linear increase positively correlated with temperature. At 40℃, 42.67% of the load overflowed within just 5 minutes of feeding. The opening of pores caused by the melting of the coating allows lithium nitrate and triethanolamine loaded deep within the natural clinoptilolite to rapidly desorb along the concentration gradient established at the solid-liquid interface. In Comparative Example 3, bare particles lacking the coating layer experienced a 68.32% runaway release within 5 minutes at 20°C. If such pulsed, high-concentration ion implantation occurs in a complex multi-cement compound system, it will inevitably disrupt the original ion dissolution and precipitation equilibrium and trigger early irreversible flocculation. Considering the release trajectory characteristics under different temperature gradients, the phase change coating structure in the prepared example not only provides physical spatial isolation but also establishes a responsive mass transfer pathway based on thermodynamic phase change. By adjusting the component release flux under different environmental enthalpies, it forcibly couples the internal chemical activation process with the fluctuations in external environmental temperature.

[0135] Test Example 2:

[0136] Experimental Objective: This test case aims to verify the hydration heat release law and the synergistic control mechanism among components of the dry-mixed quick-setting mortar of the present invention under different ambient temperatures using microcalorimetry. The experimental subjects are the dry-mixed quick-setting mortar product prepared in Example 1, the mortar with free activator directly added in Comparative Example 2, and the pure sulfoaluminate system mortar in Comparative Example 4.

[0137] Experimental steps:

[0138] (1) Sampling and environmental preconditioning: Weigh 10.05g of each of the dry-mixed mortar powder of Example 1, Comparative Example 2 and Comparative Example 4 and place them in sealed glass ampoules. Turn on the multi-channel isothermal microcalorimeter and calibrate the ambient reference temperature of different test channels to -5℃ and 20℃ respectively. Stabilize the instrument at a constant temperature for 12 hours to establish a stable heat flux baseline.

[0139] (2) Mixing and loading: Measure the mixing water corresponding to the test temperature according to a water-cement ratio of 0.18. Pour the mixing water into the ampoule outside the calorimeter and quickly homogenize it for 60 seconds using a micro glass rod. Immediately after mixing, seal the ampoule and push it vertically into the corresponding isothermal calorimetric channel.

[0140] (3) Data acquisition and conversion: Start the matching heat flow acquisition program, set the recording step size to 1 minute, and continuously monitor the heat flow rate data within 300 minutes. After the test, export the heat flow power test results of each channel, normalize them according to the exact mass of the sample to the heat release rate per unit mass, and perform integral calculation on the heat flow curve of the whole process to obtain the cumulative heat release parameter.

[0141] Experimental results (see Table 2):

[0142] Table 2: Test data of hydration heat release kinetic parameters of mortar samples in different ambient temperatures

[0143] Sample Name Test temperature (°C) End time of induction period (min) Time of first exothermic peak (min) First exothermic peak (mW / g) Time of occurrence of the second exothermic peak (min) Cumulative heat release over 5 hours (J / g) Example 1 20 18.2 46.5 12.42 173.2 241.65 Example 1 -5 42.1 88.3 8.71 251.4 196.38 Comparative Example 2 -5 5.3 23.8 15.24 No obvious peak was detected. 145.82 Comparative Example 4 20 12.4 34.1 18.67 No obvious peak was detected. 218.41

[0144] Test conclusion:

[0145] Figure 2 This is a hydration heat release rate diagram of the dry-mixed quick-setting mortar of the present invention. Figure 2 The paper specifically demonstrates the stepped heat flow distribution law of Example 1 at 20℃ and -5℃, and introduces Comparative Example 4 (pure sulfoaluminate system, 20℃) and Comparative Example 2 (uncoated free excitation group, -5℃) as reference benchmarks for kinetic behavior.

[0146] According to the data in Table 2, conventional pure sulfoaluminate systems are prone to intense exothermic reactions and concentrated heat generation during the initial hydration stage. The test results of Comparative Example 4 directly reflect this intrinsic characteristic of the material; its induction period after mixing is only 12.4 minutes, followed by a rapid surge to 18.67 mW / g of the first exothermic peak. After the peak, the heat flow curve quickly declines and remains at a low level. This one-dimensional, explosive exothermic mode often leads to localized thermal stress accumulation within the structure and insufficient structural density in the later stages of actual road repair operations.

[0147] The heat flow trajectory of Example 1 at 20°C revealed the synergistic advantages of the components in the ternary cementitious system, exhibiting two exothermic peaks with distinct time gradients throughout the system's development. High-belite sulfoaluminate cement, in combination with conventional sulfoaluminate cement, dominated the first exothermic peak at 46.5 minutes, ensuring the initial setting strength required for the repair mortar with a relatively mild heat output. Rapid-hardening silicate cement smoothly took over in the middle and later stages of the hydration reaction, constructing a broad second exothermic peak at 173.2 minutes. This effectively dispersed the overall heat of hydration while providing continuous kinetic support for the subsequent crosslinking of the hydrated calcium silicate network in the cementitious material. When exploring the system's adaptability under extreme low temperature conditions, Comparative Example 2, due to the direct incorporation of free lithium nitrate activator, experienced forced activation the moment the system came into contact with the mixing water at -5℃, dissipating most of the chemical potential energy. The heat flux reached an abnormally high 15.24 mW / g in 23.8 minutes before being completely exhausted, causing the entire liquid phase system to be unable to withstand the continuous heat deprivation from the extremely cold environment. The subsequent hydration process almost stopped, and the overall accumulated heat release over 5 hours was severely reduced.

[0148] Example 1 utilizes a temperature-sensitive phase transition barrier based on the composite particle core structure to intervene in this process. At -5°C, the initial induction period in the liquid phase is rationally controlled at 42.1 minutes. The wax eutectic coating on the functional particles undergoes localized melting and condensation after capturing the weak initial heat of hydration of the high-Belitton phase, allowing the slowly released ion clusters to take over the subsequent catalytic pathway. Although the exothermic rate is somewhat reduced overall and the peak elution time is delayed under low-temperature constraints, it still stably reproduces the complete stepped bimodal heat flow structure. This chemically confirms that the material system possesses the ability to adaptively regulate temperature fluctuations, completely avoiding the technical dead end of sub-freezing hydration dormancy.

[0149] Test Example 3:

[0150] Experimental Objective: This test aims to verify the adaptive control capability of the dry-mixed quick-setting mortar of the present invention in terms of setting time under extreme environmental temperature difference constraints. The experimental subjects are the finished dry-mixed quick-setting mortars prepared in Examples 1 to 5, and the reference mortar samples prepared in Comparative Examples 1 to 5.

[0151] Experimental steps:

[0152] (1) Test environment construction and sample preparation: Three sets of constant temperature and humidity test chambers were configured according to standard requirements. The internal ambient temperature was precisely locked at -5℃, 20℃ and 40℃ respectively, and the relative humidity was uniformly maintained at 60%±5% to simulate the actual road repair scenarios of severe winter cold, normal spring and autumn temperature and high summer temperature. All mortar dry powder samples, mixing water and test equipment were placed in the test chambers at the corresponding temperatures and left to stand for 24 hours in advance to eliminate the interference of the initial enthalpy of the material on the test results.

[0153] (2) Slurry mixing and molding: At the corresponding temperature environment, add mixing water to the dry mortar powder at a fixed water-cement ratio of 0.16 to 0.18. Use a standard planetary cement mortar mixer for mechanical mixing. Mix at low speed for 60 seconds, stop for 15 seconds, clean the residue on the pot wall, and then continue mixing at high speed for 60 seconds. Immediately after mixing, pour the homogeneous slurry into the truncated cone mold in one go, vibrate to remove air, and then scrape the surface smooth.

[0154] (3) Continuous tracking and determination of final setting time: The moment water is added is taken as the starting point for timing, and the setting process of each sample is determined using a standard Vicat apparatus. Tests are conducted every 3 minutes before the slurry loses its fluidity, and the testing frequency is shortened to once every 1 minute as the final setting state approaches. The cumulative time when the annular attachment cannot leave a clear circular mark on the sample surface and the needle penetration depth does not exceed 0.5 mm is recorded as the final setting time at that temperature. Three parallel tests are conducted in parallel, and the arithmetic mean is taken to reduce operational errors.

[0155] Experimental results (see Table 3):

[0156] Table 3: Test data of final setting time of mortar samples in different ambient temperatures

[0157] Sample Name Final setting time (min) at -5℃ Final setting time (min) at 20℃ Final setting time (min) at 40℃ Maximum time range (min) Example 1 31.5 29.0 28.5 3.0 Example 2 29.5 28.5 27.0 2.5 Example 3 32.5 30.5 29.5 3.0 Example 4 31.0 31.5 30.0 1.5 Example 5 30.5 29.5 28.0 2.5 Comparative Example 1 65.0 30.5 27.5 37.5 Comparative Example 2 18.5 15.0 10.5 8.0 Comparative Example 3 22.0 16.5 12.0 10.0 Comparative Example 4 45.5 28.0 15.5 30.0 Comparative Example 5 58.0 25.5 14.0 44.0

[0158] Test conclusion:

[0159] Figure 3 This is a curve showing the setting time variation of the dry-mixed quick-setting mortar across the entire temperature range according to the present invention. Figure 3 (a) Specifically demonstrates the setting time fluctuation trajectory of multiple mortar systems configured in Examples 1 to 5 within a wide temperature range of -5℃ to 40℃. Figure 3 (b) then presents the hydration runaway phenomenon faced by Comparative Examples 1 to 5 under the same temperature gradient.

[0160] According to the data in Table 3, conventional pavement repair materials often face the technical dilemma of early-stage collapse when confronted with large-scale environmental temperature differences. In Comparative Examples 4 and 5, when using traditional pure sulfoaluminate systems or commercially available accelerators, the setting time exhibited a highly linear dependence on ambient heat. Under simulated summer pavement temperatures of 40°C, the supersaturated precipitation of calcium aluminate hydrate nuclei led to explosive setting within 15 minutes or even less, completely eliminating effective time for manual finishing and leveling. Conversely, in a simulated frozen soil environment of -5°C, the sharp drop in liquid phase activation energy caused the hydration reaction to enter a dormant period. Comparative Example 1, lacking the low-temperature ignition effect of high-belite sulfoaluminate cement, experienced a severely delayed final setting time of 65 minutes. This drastic time drift was sufficient to cause irreversible structural frost damage to the repaired section.

[0161] The influence of microscopic catalytic mechanisms on macroscopic states of matter was explored. Comparative Examples 2 and 3 attempted to salvage low-temperature performance by directly incorporating accelerators. While this forcibly compressed the condensation period at -5°C to some extent, it triggered a vicious cycle of ion concentration at 20°C and 40°C, leading to uncontrolled rapid condensation across the entire temperature range. This demonstrates that a single chemical catalytic pathway cannot establish a buffer system to cope with temperature fluctuations. The high consistency of macroscopic data shown in Examples 1 to 5 confirms the deep thermodynamic coupling between the ternary gelation system and the temperature-sensitive functional particles. Within an extreme temperature range exceeding 45°C, the final condensation time of each example group was consistently kept within the target range of 27 to 32.5 minutes, with the maximum time range not exceeding 3 minutes.

[0162] This bio-thermostating mechanism manifests as a dynamic chemical resistance network within the system. When a low-temperature environment attempts to freeze the hydration process, the phase change material melts in a timely manner and releases potent nucleating agents such as lithium nitrate, forcibly raising the system temperature through localized catalytic exothermic reaction. When a high-temperature environment poses a risk of explosive coagulation, the unique ion exchange channels of the zeolite carrier actively intervene, temporarily adsorbing excess calcium and aluminate ions in the liquid phase, forming an effective steric barrier in conjunction with citric acid complexes. This intelligent valve mechanism, which relies on the thermal environment to spontaneously regulate the reaction intensity, endows this mortar material with true all-weather construction capabilities.

[0163] Test Example 4:

[0164] Experimental Objective: This test aims to investigate the strength evolution of dry-mixed quick-setting mortar at different hydration stages and verify the synergistic control mechanism of the ternary composite cementitious system and functional admixtures on early strength gain and later microstructural stability. The experimental subjects were the finished dry-mixed quick-setting mortars prepared in Examples 1 to 5, and the reference mortar samples prepared in Comparative Examples 1, 4, and 5.

[0165] Experimental steps:

[0166] (1) Weigh out the dry powder of each group of mortar and the mixing water according to the water-cement ratio of 0.16, and mechanically mix them in a constant temperature room of 20℃ using a planetary cement mortar mixer. Divide the well-mixed slurry into two layers and put them into a special triple mold of 40mm×40mm×160mm. Place it on a vibrating table to vibrate and shape it. Scrape off the excess slurry and smooth the surface.

[0167] (2) Record the initial time of adding water and mixing. Transfer the molded specimens into a standard curing chamber at 20℃ and relative humidity not less than 90% for initial curing. For ultra-early specimens with test ages of 30 min and 2 h, demolding should be performed 5 minutes before reaching the specified age. For late-stage specimens with a test age of 28 d, demolding should be performed uniformly 24 hours after molding, and then the specimens should be immersed in a constant temperature water bath at 20℃ for continued curing until the specified age.

[0168] (3) Upon reaching the corresponding test age, remove the specimen and wipe off the surface moisture. Use a microcomputer-controlled electro-hydraulic servo universal testing machine to determine the flexural strength at a loading rate of 50 N / s. After the flexural test, place the broken half of the specimen in the compression fixture and determine the compressive strength at a loading rate of 2400 N / s. Test 3 specimens for each age group. The flexural strength is taken as the arithmetic mean, and the compressive strength is taken as the arithmetic mean of the 6 broken specimen test values. Discrete data that exceed the allowable error range are discarded.

[0169] Experimental results (see Table 4):

[0170] Table 4: Compressive and flexural strength test data of mortar samples at different ages.

[0171] Sample Name 30-minute compressive strength (MPa) Flexural strength (MPa) at 30 min 2h compressive strength (MPa) Flexural strength at 2 hours (MPa) 28-day compressive strength (MPa) 28-day flexural strength (MPa) Example 1 22.36 4.52 35.61 6.84 68.43 11.27 Example 2 21.84 4.38 34.25 6.75 65.72 10.95 Example 3 23.15 4.67 36.42 6.92 67.85 11.08 Example 4 20.92 4.15 33.88 6.43 71.36 11.84 Example 5 22.78 4.61 36.14 6.88 69.25 11.42 Comparative Example 1 14.53 3.12 24.87 5.26 58.44 9.63 Comparative Example 4 20.47 4.05 28.16 5.82 51.28 8.45 Comparative Example 5 23.51 4.86 31.85 6.15 48.62 7.94

[0172] Test conclusion:

[0173] Figure 4 These are curves showing the evolution of compressive strength of each group of mortar samples as a function of age. Figure 4 The document specifically demonstrates the ternary cementitious systems represented by Examples 1 and 3, as well as the compressive strength growth trajectory and subsequent shrinkage phenomenon of Comparative Example 1 (lacking high belite sulfoaluminate cement), Comparative Example 4 (pure sulfoaluminate cement system), and Comparative Example 5 (using commercially available aluminate accelerator) over a span of 30 minutes, 2 hours, and 28 days.

[0174] According to the data in Table 4, in road repair engineering practice, materials often face a contradiction between the requirements of early traffic opening and the later structural durability. The traditional pure sulfoaluminate system represented by Comparative Example 4 achieved an initial compressive strength of 20.47 MPa at 30 minutes, meeting the basic mechanical threshold for ultra-early traffic opening. However, its actual later strength evolution fell into a trap of stagnant growth or even slight shrinkage. This phenomenon stems from the large-scale formation of needle-like ettringite crystals in the early stages of pure sulfoaluminate cement hydration. After these crystals overlap to form an early skeleton, as the internal free water is consumed and local micro-environment stress concentrates, the coarse crystals generate microcracks and destroy the overall density of the hardened paste.

[0175] Comparative Example 5 introduced a commercially available accelerator. While the initial forced injection of free aluminate ions initially boosted the 30-minute compressive strength to 23.51 MPa, the large number of impurity ions disrupted the precipitation-dissolution equilibrium of the liquid phase, causing a significant drop in the 28-day compressive strength to 48.62 MPa. The subsequent strength reduction rate was extremely high. Comparative Example 1, after removing the high-belite phase, only achieved a 30-minute strength of 14.53 MPa, revealing that the two-component system lacked sufficient reaction potential energy in the ultra-early phase overlap stage, making it unsuitable for meeting the stringent load-bearing requirements of emergency environments within two hours.

[0176] Examples 1 to 5 exhibit a step-like, progressive mechanical evolution characteristic without subsequent regression. Taking Example 1 as an example, the compressive strength reaches 22.36 MPa at 30 minutes and steadily climbs to 68.43 MPa at 28 days. This long-term, robust mechanical growth relies on the alternating hydration of ternary mineral phases and the microscopic filling network of active microparticles. In the early stage of hydration, calcium sulfoaluminate minerals rapidly provide the ettringite framework to support the spatial configuration. The abundant C2S minerals in the high-belite sulfoaluminate cement play a buffering and connecting role in the mid-stage hydration process, and the continuously generated calcium silicate gel encapsulates and stabilizes the early crystal network.

[0177] The hydration products continuously released by rapid-hardening silicate cement over a 28-day period, combined with the secondary pozzolanic reaction between nano-calcium carbonate and metakaolin, transform free calcium ions within the capillaries into dense CSH gel, completely sealing the spatial pathways for microcrack initiation. Mechanical test data, from a macroscopic load-bearing capacity perspective, confirms that the designed dry-mixed mortar not only breaks the inherent fate of conventional rapid-setting materials—"early strength inevitably leads to later shrinkage"—but also establishes a highly dense hardened matrix with self-healing potential at the microscopic scale.

[0178] Test Example 5:

[0179] Experimental Objective: This test aims to verify the volume stability of dry-mixed quick-setting mortar after curing and its interfacial deformation-co-deformation capability with existing concrete substrates. The experimental subjects were the finished dry-mixed quick-setting mortars prepared in Examples 1 to 5, and the reference mortar samples prepared in Comparative Examples 4 and 6.

[0180] (1) A reference concrete slab with a strength grade of C40 was prepared in advance and cured in a standard curing room for 28 days. The surface of the reference slab was roughened by a high-pressure water jet device to expose the coarse aggregate to simulate the rough base surface after milling in actual road repair. The reference slab was then soaked in water for 24 hours and the surface water was wiped off before the test.

[0181] (2) Prepare each group of mortar slurry according to the corresponding mix ratio and mixing process. Pour a portion of the mixed slurry into a steel drawing mold with an inner diameter of 40 mm fixed on the surface of the reference plate, gently vibrate to compact and smooth it, for subsequent interfacial bond strength testing; pour the other portion of the slurry into a special shrinkage steel mold of 25 mm × 25 mm × 280 mm, embed stainless steel probes at both ends, for long-term monitoring of drying shrinkage rate.

[0182] (3) Pull-out specimens were cured in a constant temperature chamber at 20℃ for 28 days. The pull-out base was bonded to the mortar surface using high-strength epoxy resin. After curing, a smart digital display bond strength tester was used to apply a vertical tensile force at a constant rate. The critical load at failure was recorded, the morphology of the failure surface was observed, and the pull-out bond strength was calculated. Shrinkage specimens were demolded 24 hours after molding. Their initial length was measured using a high-precision length comparator. They were then placed in a test chamber at 20℃ and 60% relative humidity and left to stand. The length change value at 28 days was recorded and converted into the drying shrinkage rate.

[0183] Experimental results (see Table 5):

[0184] Table 5: Test data of interfacial bond strength and drying shrinkage of mortar samples after 28 days.

[0185] Sample Name 28-day interfacial bond strength (MPa) 28-day drying shrinkage rate (%) Observation of the characteristics of the damaged surface Example 1 2.74 0.024 Most of the concrete substrate was damaged. Example 2 2.61 0.028 Mixed destruction Example 3 2.83 0.021 Substrate damage is the main issue. Example 4 2.55 0.031 Mixed destruction Example 5 2.89 0.018 Mixed destruction of substrate and material bulk Comparative Example 4 1.94 0.068 Completely stripped of the interface Comparative Example 6 1.62 0.053 Interface stripping is the main focus

[0186] Test conclusion:

[0187] Figure 5 This is a comparison chart of the interfacial bond strength and drying shrinkage rate of various groups of mortar samples after 28 days, in which... Figure 5 (a) The differences in pull-out bearing capacity of concrete substrates between Examples 1 and 3 and Comparative Examples 4 and 6 are visually presented in the form of grayscale columnar sections. Figure 5 (b) traces the volume shrinkage evolution of the four corresponding samples under constrained conditions through the broken line trajectory.

[0188] According to the data in Table 5, during the long service life of actual road repair projects, interfacial delamination often precedes the damage to the repair material itself, becoming the root cause of systemic failure. Comparative Example 4 relies solely on a single sulfoaluminate system, and its hydration product, ettringite, readily consumes surrounding free water after its early formation in large quantities, causing a sharp increase in the negative pressure of the internal capillary pores, ultimately exhibiting a 28-day drying shrinkage rate as high as 0.068%.

[0189] This massive macroscopic shrinkage translates into severe interlaminar shear stress on the confined old concrete substrate, directly resulting in an interfacial bond strength of only 1.94 MPa, with the failure surface exhibiting typical brittle delamination characteristics. Investigating the microscopic intervention effect of the preparation process on interfacial properties, it was found that Comparative Example 6, lacking the high-speed shear mixing step, experienced a bond performance that plummeted to a low of 1.62 MPa. Low-speed stirring could not break the agglomeration effect of nano-calcium carbonate and microporous zeolite particles in a short time. Incompletely deagglomerated functional particles formed dense micro-defect stress concentration zones within the slurry. Free water evaporated outward along these loose channels, exacerbating localized drying shrinkage. This reflects the irreplaceable bridging role of process parameters in the dispersion of microparticles and macroscopic volume stability.

[0190] The example groups, through the combined construction of ternary component cascade hydration and high-speed shearing technology, completely reversed this mechanical degradation trend. The 28-day bond strength of Examples 1 and 3 remained stable between 2.74 MPa and 2.83 MPa, and the failure surfaces in the pull-out tests all reached the interior of the original reference concrete, proving that the anchoring force between the old and new interfaces exceeded the tensile limit of the substrate itself.

[0191] Tracing the source from the perspective of volumetric deformation, metakaolin and silica fume are uniformly embedded in the cement-based micropores under a shear field. The CSH gel formed in the later stages of hydration effectively severs the capillary network that allows moisture to migrate to the external environment, forcibly reducing the overall system's 28-day shrinkage rate to below 0.024%. The phase change coating on the surface of the functional particles not only regulates heat during the phase change process, but its trace amounts of wax exudation also play a role in stress lubrication and hydrophobic sealing at the tips of linear microcracks, offsetting the shrinkage stress induced by the coupling of temperature and humidity differences. This bottom-up microstructural intervention ultimately constructs a low-shrinkage, high-adhesion, durable repair system at the macroscopic level.

Claims

1. A dry-mixed quick-setting mortar for road repair, characterized in that, Made from the following components by weight percentage: Sulfoaluminate cement: 25.0%~35.0%; Rapid-hardening Portland cement: 15.0%~25.0%; High belite sulfoaluminate cement: 10.0%~20.0%; Graded fine sand: 20.0%~40.0%; Active admixtures: 5.0%–10.0%; Thermosensitive microporous mineral composite functional particles: 1.0%–2.5%; Nano-calcium carbonate: 1.0%–3.0%; Calcium aluminate quick-setting agent: 0.5%~1.5%; Citric acid: 0.05%–0.1%; Polypropylene fiber: 0.1%–0.3%; Polycarboxylate superplasticizer: 0.5%–1.2%; Cellulose ethers: 0.05%–0.15%; Plasticizer: 0.1%~0.2%.

2. The dry-mixed quick-setting mortar for road repair according to claim 1, characterized in that, The active admixture is composed of metakaolin, silica fume and fly ash, and the mass ratio of metakaolin, silica fume and fly ash is 2:1:

2.

3. The dry-mixed quick-setting mortar for road repair according to claim 1, characterized in that, The temperature-sensitive microporous mineral composite functional particles include a microporous mineral carrier, a composite excitation liquid loaded in the pores of the microporous mineral carrier, and a phase change coating covering the outer surface of the microporous mineral carrier. The microporous mineral carrier is natural clinoptilolite powder that has undergone roasting and activation treatment. The polycarboxylate-based high-efficiency water-reducing agent is an ether-based polycarboxylate water-reducing agent powder; The plasticizer is selected from dibutyl phthalate or sodium lignosulfonate. The composite activating solution is composed of lithium nitrate and triethanolamine mixed at a mass ratio of 2.8 to 3.

2. The phase change coating is a mixture of stearic acid and paraffin, and the mass ratio of stearic acid to paraffin is 0.8 to 1.

2.

4. The dry-mixed quick-setting mortar for road repair according to claim 3, characterized in that, The preparation steps of the temperature-sensitive microporous mineral composite functional particles include: Natural clinoptilolite powder was selected and calcined at 280℃~320℃ for 1.5h~2.5h, then cooled to room temperature; The activated natural clinoptilolite powder was placed in a vacuum environment and kept at a pressure of -0.085MPa to -0.095MPa for 20 to 30 minutes. The composite activation liquid was introduced at a mass ratio of 100:(20 to 30) of zeolite powder to composite activation liquid. The pressure was restored to normal and stirred at a speed of 40 r / min to 60 r / min for 25 to 40 minutes. Weigh out the phase change coating mixture at a ratio of 12% to 18% by mass of zeolite powder, heat it to 65℃ to 75℃ to a molten state, preheat the zeolite powder after restoring it to normal pressure to 45℃ to 50℃, and uniformly spray the molten coating material through an atomizing nozzle, controlling the cooling rate to 2℃ / min to 5℃ / min, to obtain composite functional particles with a particle size of 45μm to 100μm.

5. The dry-mixed quick-setting mortar for road repair according to claim 1, characterized in that, The specific surface area of ​​the sulfoaluminate cement, rapid-hardening silicate cement, and high-belite sulfoaluminate cement is controlled at 380 m². 2 / kg~480m 2 Between / kg; The graded fine sand is either manufactured sand or natural sand that has been dried and graded. The average particle size of the nano-calcium carbonate is 20 nm to 80 nm, and its specific surface area is 20 m². 2 / g~40m 2 / g; The polypropylene fiber is a monofilament bundle with a length of 6mm to 12mm and a diameter of 15μm to 30μm.

6. A preparation process for a dry-mixed quick-setting mortar for road repair, used to prepare the dry-mixed quick-setting mortar for road repair as described in any one of claims 1-5, characterized in that, Includes the following steps: According to the weight percentage ratio, separately weigh out sulfoaluminate cement, rapid-hardening silicate cement, high belite sulfoaluminate cement, active admixture, graded fine sand, temperature-sensitive microporous mineral composite functional particles, nano calcium carbonate, calcium aluminate quick-setting agent, citric acid, polypropylene fiber, polycarboxylate-based high-efficiency water-reducing agent, cellulose ether, and plasticizer. The weighed sulfoaluminate cement, rapid-hardening silicate cement, high belite sulfoaluminate cement, active admixture, nano-calcium carbonate, temperature-sensitive microporous mineral composite functional particles, and graded fine sand are put into a mixing device and dry-mixed at the first speed to obtain a premixed material. Continue to add the weighed polypropylene fiber, calcium aluminate quick-setting agent, citric acid, plasticizer, polycarboxylate-based high-efficiency water-reducing agent and cellulose ether to the mixing equipment containing the premixed materials. Raise the mixing equipment to the second speed for high-speed shearing and mixing. After the mixing is completed, discharge the material to obtain dry-mixed quick-setting mortar for road repair.

7. The preparation process of a dry-mixed quick-setting mortar for road repair according to claim 6, characterized in that, The mixing equipment is a twin-shaft paddle mixer; The first rotational speed is controlled between 320 r / min and 380 r / min; The dry mixing time is controlled to be 3 min to 5 min.

8. The preparation process of a dry-mixed quick-setting mortar for road repair according to claim 6, characterized in that, The second rotation speed is controlled between 850 r / min and 1000 r / min, and the high-speed shear mixing time is controlled between 5 min and 8 min.

9. The preparation process of a dry-mixed quick-setting mortar for road repair according to claim 6, characterized in that, The active admixture is prepared by weighing metakaolin, silica fume and fly ash in the corresponding mass ratio and dry mixing them to homogenize them beforehand, and then using them as a single mixed component. The graded fine sand is all fed into the mixing equipment at the first rotational speed stage.

10. The preparation process of a dry-mixed quick-setting mortar for road repair according to claim 6, characterized in that, The relative humidity of the environment during the shear mixing process at the first and second rotation speeds is controlled below 45%, and during the shear mixing stage at the second rotation speed, the loading volume of the material in the mixing equipment is controlled to be 50% to 60% of the effective volume of the mixer.

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