A nanocarrier-based controlled-release composite functional admixture and its application

Abstract

This invention relates to the field of concrete admixture technology, specifically to a nano-carrier controlled-release composite functional admixture and its application. The admixture includes a controlled-release retarding component, comprising a nano-carrier, a retarding active component, and a dispersing stabilizer. The nano-carrier is a silane coupling agent-modified nano-silica / haloite composite powder; the retarding active component is a compound of sodium gluconate and citric acid; the dispersing stabilizer is a polycarboxylate superplasticizer; the nucleation-type early-strength component includes C-S-H / PCE nanocrystals and an inorganic early-strength salt; the inorganic early-strength salt is a compound of aluminum sulfate and lithium carbonate; and the expansion-compensating component includes a calcium oxide-calcium sulfoaluminate composite expansion agent. This invention achieves precise temporal control and volume stability optimization of the hydration process of a ternary composite system through the triple synergy of nano-carrier controlled-release technology, C-S-H nucleation early-strength technology, and expansion-compensating technology.

Description

Technical Field

[0001] This invention relates to the field of concrete admixture technology, specifically to a nanocarrier controlled-release composite functional admixture and its application. Background Technology

[0002] The increasingly stringent requirements for the comprehensive performance of cement-based materials in projects such as precast component steam curing, high-rise pumping, and self-leveling have led to mortar materials possessing both high early strength and excellent workability becoming a current research hotspot. Combining ordinary Portland cement (OPC), sulfoaluminate cement (SAC), and mineral powder (GGBS) to construct an OPC-SAC-GGBS ternary composite cementitious system can achieve complementary advantages and is one of the effective ways to obtain high-performance cementitious materials. However, the hydration characteristics of ordinary Portland cement and sulfoaluminate cement differ significantly. Simple combination often leads to uncoordinated hydration processes. The rapid hydration of sulfoaluminate cement drastically accelerates the hardening of the slurry, severely impairing the construction operation time and fluidity retention. Conversely, simply adding retarders to improve workability often excessively delays the overall hydration process, significantly inhibiting early strength development. Therefore, how to precisely control the hydration process of this composite system to achieve suitable workability and setting time while simultaneously achieving ideal early strength development is a key technical bottleneck for its engineering applications. Existing methods often employ a single retarder to regulate the setting time of composite cement systems. While this method can extend the setting time and improve workability to some extent, the strong adsorption of retarder molecules on the surfaces of active minerals such as tricalcium aluminate (C3A) and anhydrous calcium sulfoaluminate (C4A3S_) creates a complexing barrier that inhibits ion dissolution and product nucleation in the early stages of hydration. This results in an excessive delay in the early hydration reaction, leading to a significant loss in the early flexural and compressive strength of the cement system, making it difficult to meet the demolding and load-bearing requirements of rapid-hardening and early-strength projects.

[0003] For example, a single early-strength agent can be used to promote the early-stage strength development of cement-based materials by introducing additional Al³. + SO4² - Or Li + While accelerating the formation of ettringite and hydrated calcium silicate gel (CSH) can result in higher mechanical properties in the early stages, it also accelerates the exothermic hydration and hardening processes, leading to a decrease in the initial fluidity of the slurry, an increase in time-related losses, and a significant reduction in the workable time.

[0004] Currently, although there are methods for simply mixing retarders and accelerators, these are mostly conventional blends for single cement types, without considering the unique hydration kinetics of the OPC-SAC-GGBS ternary composite system. Furthermore, the timing of action of retarders and accelerators lacks effective matching, often resulting in antagonistic effects: either the retardation effect is too strong, preventing the accelerator from functioning effectively, or the accelerator takes over prematurely, leading to a sharp loss of workability. This fails to achieve the synergistic regulation of controllable initial retardation and effective later-stage strength promotion.

[0005] In recent years, nano-hydrated calcium silicate (CSH) nucleation accelerators have attracted widespread attention as a novel early-strength material. CSH nuclei can provide additional nucleation sites for cement hydration products, helping to lower the nucleation barrier and thus accelerating the cement hydration process. However, existing CSH nucleation accelerators are mostly used in single silicate cement systems, with limited research on their application in OPC-SAC-GGBS ternary composite systems. Furthermore, the compatibility of CSH nuclei with sulfoaluminate cement hydration products and their inducing effect on ettringite nucleation remain unclear. In addition, the dispersion stability of CSH nuclei in cement paste also limits the full realization of its early-strength effect.

[0006] Layered bimetallic hydroxides (LDHs), as two-dimensional nanomaterials with ion exchange and intercalation properties, have mature applications in the field of controlled drug release, but their application in cement admixtures is still in its early stages. Utilizing the interlayer ion exchange properties of LDHs, intercalating retarder molecules between LDH layers can achieve controlled release of the retarder; however, systematic research combining LDH intercalation technology with the hydration regulation of the OPC-SAC-GGBS ternary composite system is currently lacking.

[0007] Nanomaterials such as nano-silica and halloysite nanotubes can be used as carrier materials in cement-based materials due to their high specific surface area and surface activity. Surface modification of nanocarriers using silane coupling agents can improve their dispersibility in cement paste and enhance their interfacial bonding with organic retarders. However, current technologies primarily use nanocarriers to enhance the mechanical properties of concrete or as carriers for water-reducing agents, lacking specific designs for their use as controlled-release carriers of retarders, and failing to address the temporal synergistic regulation with early-strength components.

[0008] Furthermore, the OPC-SAC-GGBS ternary composite system is prone to early self-shrinkage during the early hydration process due to the rapid formation of ettringite and the dense accumulation of CSH gel, leading to microcracks and affecting the material's volume stability and durability. Current technologies lack effective compensation measures for the early shrinkage of this composite system, and the synergistic design of expanding agents and retarding-early strength systems is completely lacking.

[0009] In summary, existing technologies lack a nanocarrier-based controlled-release composite admixture specifically designed for the OPC-SAC-GGBS ternary composite system that can precisely control the hydration process from slow to rapid and also has shrinkage compensation capabilities. Summary of the Invention

[0010] To address the technical contradiction in existing OPC-SAC-GGBS ternary composite gelling systems—namely, the difficulty in balancing workability and early strength, and the significant early shrinkage—this invention provides a nanocarrier-based controlled-release composite functional admixture and its application.

[0011] This invention is achieved through the following technical solution: A nanocarrier-based controlled-release composite functional admixture includes: Controlled-release retarding components include nanocarriers, retarding active components, and dispersing stabilizers; The nanocarrier is a silane coupling agent modified nano-silica / haloite composite powder; the retarding active component is a compound of sodium gluconate and citric acid; and the dispersing stabilizer is a polycarboxylate superplasticizer. Nucleus-type early strength components include CSH / PCE nanocrystals and inorganic early strength salts; Among them, the inorganic early-strength salt is a compound of aluminum sulfate and lithium carbonate; The expansion compensation component includes a calcium oxide-calcium sulfoaluminate composite expansion agent.

[0012] Preferably, sodium gluconate accounts for 40% to 60% of the total mass of the retarding active components, and citric acid accounts for 40% to 60% of the total mass of the retarding active components.

[0013] Preferably, the preparation method of the controlled-release retarded component is as follows: a silane coupling agent modified nano-silica / haloysite composite carrier is added to deionized water for ultrasonic dispersion, then a mixed solution of sodium gluconate and citric acid is added for stirring and adsorption, and finally a polycarboxylate superplasticizer as a dispersion stabilizer is added and stirring is continued to obtain a suspension containing the controlled-release retarded component.

[0014] Preferably, the preparation method of the nanocarrier is as follows: nano silica and halloysite are mixed in a mass ratio of (1:2) to (2:1), then added to anhydrous ethanol and ultrasonically dispersed, then a silane coupling agent is added dropwise, and then a reflux reaction is carried out. After centrifugation, washing and drying, a silane coupling agent modified nano silica / haloysite composite carrier is obtained; wherein, the silane coupling agent is composed of γ-aminopropyltriethoxysilane and γ-methacryloyloxypropyltrimethoxysilane in a mass ratio of (1:1) to (1:1.5).

[0015] Preferably, the amount of CSH / PCE nanocrystal nuclei is 60% to 80% of the total mass of the nucleus-type early strength component, and the amount of inorganic early strength salt is 20% to 40% of the total mass of the nucleus-type early strength component.

[0016] Preferably, the preparation method of CSH / PCE nanocrystal nuclei is as follows: calcium nitrate and sodium silicate are dissolved in deionized water to prepare a 0.5 mol / L solution, and polycarboxylate superplasticizer is dissolved in deionized water to prepare a 5% (w / w) solution; At room temperature, calcium nitrate solution and sodium silicate solution were simultaneously added dropwise to PCE solution, with the calcium-silicon molar ratio controlled at 1.2–1.8. During the addition process, the mixture was continuously stirred and the pH value was controlled at 10.5–11.5. After the addition was complete, stirring was continued for 2 hours, followed by aging to obtain a CSH / PCE nanocrystal suspension, in which the CSH solid content was 5% to 10%.

[0017] Preferably, aluminum sulfate accounts for 50% to 70% of the total mass of the inorganic early-strength salt, and lithium carbonate accounts for 30% to 50% of the total mass of the inorganic early-strength salt.

[0018] Preferably, in the expansion compensation component, the mass ratio of calcium oxide type expansion component to calcium sulfoaluminate type expansion component is 1:1 to 2:1.

[0019] Application of the aforementioned nanocarrier controlled-release composite functional admixture in the OPC-SAC-GGBS ternary composite gelling system.

[0020] Preferably, based on 100 parts by weight of cementitious materials, the amount of controlled-release retarding component is 0.010–0.025 parts by weight, the amount of nucleation-type early-strength component is 0.080–0.200 parts by weight, and the amount of expansion-compensating component is 0.50–1.50 parts by weight; wherein, the cementitious materials include 60–70 parts by weight of ordinary Portland cement, 22–32 parts by weight of sulfoaluminate cement, and 8–18 parts by weight of granulated blast furnace slag powder; Usage instructions include: S1, ordinary silicate cement, sulfoaluminate cement, mineral powder, polycarboxylate superplasticizer and expansion compensation component are dry mixed to obtain premixed cementitious material; A controlled-release retarded component suspension was prepared using a controlled-release retarded component; Preparation of mixing water containing nucleation-type early strength components using nucleation-type early strength components; S2 involves adding sand to premixed cementitious materials for dry mixing, then adding a suspension prepared from controlled-release retarding components and stirring. After stirring evenly, nucleation-type early-strength components and remaining mixing water are added and stirred thoroughly to obtain cement paste and mortar with the characteristics of first slowing, then accelerating, and then compensating.

[0021] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses a nanocarrier-based controlled-release composite functional admixture comprising a controlled-release retarding component, a nucleation-type early-strength component, and an expansion-compensating component. It achieves precise temporal control and volumetric stability optimization of the hydration process of the ternary composite system through the triple synergy of nanocarrier controlled-release technology, CSH nucleation-type early-strength technology, and expansion-compensating technology. Specifically: Firstly, in the controlled-release retarding component, this invention uses a silane coupling agent-modified nano-silica / haloyrite composite carrier to load the retarding component. The controlled release of the retarding component can be achieved through surface adsorption and pore confinement effects of the nano-carrier, thereby extending the retarding time and avoiding excessive early retarding. Compared to traditional retarders, silane coupling agent-modified halloyrite composite powder is used as a water-reducing agent, while the silane coupling agent-modified nano-silica / haloyrite composite powder in this application is used as a retarder. The controlled-release retarding component has a moderate initial release rate, avoiding strength loss caused by excessive early retarding. As hydration progresses, the retarding component is continuously released, extending the effective retarding time and ensuring the workability of the paste. Furthermore, the introduction of the nano-carrier can enhance the dispersion stability of the retarding component in the cement paste, reducing the problem of excessively high or low local concentrations.

[0022] Secondly, in the nucleation-type early-strength component, this invention introduces CSH / PCE nanocrystals as the early-strength component. Utilizing their nucleation effect and the stabilizing effect of the polycarboxylic acid dispersant, it rapidly induces the nucleation and growth of hydration products after the retardation period, thereby achieving a rapid increase in early strength. Specifically, the CSH nuclei and inorganic early-strength salts (aluminum sulfate and lithium carbonate) produce a synergistic effect: the CSH nuclei provide nucleation sites and lower the nucleation barrier; the aluminum sulfate provides Al³⁺. + and SO4² - Lithium carbonate promotes rapid crystallization of ettringite; lithium carbonate through Li + The strong polarization effect accelerates the hydrolysis of C3S. The synergistic effect of the three factors results in an explosive increase in early strength, with a compressive strength of 20-28 MPa after 8 hours, which is significantly better than traditional early strength agents.

[0023] Thirdly, in the expansion compensation component, this invention incorporates a calcium oxide-calcium sulfoaluminate composite expansion agent to compensate for early shrinkage. This is achieved through a dual mechanism of hydration expansion of calcium oxide and ettringite expansion of calcium sulfoaluminate to compensate for the early chemical and auto-shrinkage of the OPC-SAC-GGBS ternary composite system. Furthermore, the nanocarrier controlled-release technology ensures that the expansion agent only begins to fully exert its effect after the retardation period, avoiding the adverse effects of early expansion on flowability, thereby achieving coordinated development of expansion and strength.

[0024] Fourth, this invention achieves three-stage hydration regulation—first slow, then rapid, and finally compensating—through precise matching of the slow-release timing of the nanocarrier with the activation timing of the CSH crystal nuclei. In the first stage (0–2 h), the controlled-release slow-release component dominates, ensuring working performance; in the second stage (2–8 h), the release rate of the slow-release component decreases, and the CSH crystal nuclei and early-strength salt are activated, rapidly promoting strength development; in the third stage (after 8 h), the expansion compensation component takes effect, compensating for early shrinkage and ensuring volume stability. This time-series synergistic mechanism solves the industry problem of balancing workability, early strength, and volume stability in ternary composite systems.

[0025] Fifth, the composite functional admixture of this invention has a simple preparation process, widely available raw materials, and controllable costs. It does not require changes to existing concrete or mortar production processes, and has good engineering adaptability and promotional value. The preparation of the nanocarrier and CSH crystal nuclei both adopt room temperature and pressure processes, which are energy-efficient and environmentally friendly, and are especially suitable for rapid repair, precast component steam curing, ultra-high-rise pumping, and self-leveling projects that require rapid hardening and early strength. Detailed Implementation

[0026] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0027] Unless otherwise stated, the terms used herein (including technical terms) have their common meaning as understood by one of ordinary skill in the art. Furthermore, it is understood that terms defined in commonly used dictionaries should be understood to have a meaning consistent with the context of their relevant field, and not to be interpreted as having an idealized or overly formal meaning.

[0028] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0029] This invention discloses a nanocarrier-based controlled-release composite functional admixture, comprising: Controlled-release retarding components include nanocarriers, retarding active components, and dispersing stabilizers.

[0030] The nanocarrier is a silane coupling agent modified nano-silica / haloysite composite powder. The preparation method is as follows: nano-silica and halloysite are mixed at a mass ratio of (1:2) to (2:1), then added to anhydrous ethanol and ultrasonically dispersed for 30 min. A silane coupling agent is then added dropwise, followed by a reflux reaction (reflux reaction at 60–80℃ for 4–6 h). After centrifugation, washing, and drying, the silane coupling agent modified nano-silica / haloysite composite carrier is obtained. The silane coupling agent is a compound of γ-aminopropyltriethoxysilane and γ-methacryloyloxypropyltrimethoxysilane at a mass ratio of (1:1) to (1:1.5), and its dosage is 3%–8% of the nanocarrier's mass.

[0031] The retarding active component is a compound of sodium gluconate and citric acid. Sodium gluconate accounts for 40% to 60% of the total mass of the retarding active component, and citric acid accounts for 40% to 60% of the total mass of the retarding active component.

[0032] The dispersant stabilizer is a polycarboxylate superplasticizer, and the dosage is 5% to 15% of the total mass of the controlled-release retarding component.

[0033] The preparation method of the controlled-release retarded component is as follows: the nano-silica / haloite composite carrier modified with silane coupling agent is added to deionized water and ultrasonically dispersed for 20 min. Then, a mixed solution of sodium gluconate and citric acid is added and stirred and adsorbed at 40-50℃ for 2-3 h. Finally, polycarboxylate superplasticizer as a dispersion stabilizer is added and stirred for another 30 min to obtain the controlled-release retarded component suspension.

[0034] Nucleus-type early strength components include CSH / PCE nanocrystals and inorganic early strength salts; The amount of CSH / PCE nanocrystal nuclei is 60% to 80% of the total mass of the nucleus-type early strength component, and the amount of inorganic early strength salt is 20% to 40% of the total mass of the nucleus-type early strength component.

[0035] CSH / PCE nanocrystals were prepared by solution chemical precipitation method, specifically: calcium nitrate and sodium silicate were dissolved in deionized water to prepare a 0.5 mol / L solution, and polycarboxylate superplasticizer was dissolved in deionized water to prepare a 5% (w / w) solution. At room temperature, calcium nitrate solution and sodium silicate solution were simultaneously added dropwise to PCE solution, with the calcium-silicon molar ratio controlled at 1.2–1.8. During the addition process, the mixture was continuously stirred and the pH value was controlled at 10.5–11.5. After the addition was complete, stirring was continued for 2 hours, followed by aging for 24 hours to obtain a CSH / PCE nanocrystal suspension, in which the CSH solid content was 5% to 10%.

[0036] Inorganic early-strength salts are complexes of aluminum sulfate and lithium carbonate, wherein aluminum sulfate accounts for 50% to 70% of the total mass of the inorganic early-strength salts, and lithium carbonate accounts for 30% to 50% of the total mass of the inorganic early-strength salts.

[0037] The expansion compensation component includes a calcium oxide-calcium sulfoaluminate composite expansion agent, and the mass ratio of the calcium oxide type expansion component to the calcium sulfoaluminate type expansion component is 1:1 to 2:1.

[0038] The calcium oxide type expansion component is calcium oxide expanded clinker obtained by calcining limestone and gypsum at 800-900℃, with a specific surface area of ​​350-450 m² / kg; the calcium sulfoaluminate type expansion component is calcium sulfoaluminate expanded clinker obtained by calcining bauxite, gypsum and limestone at 1200-1300℃, with a specific surface area of ​​400-500 m² / kg.

[0039] This invention also discloses the application of a nano-carrier controlled-release composite functional admixture in the OPC-SAC-GGBS ternary composite gelling system.

[0040] Based on 100 parts by weight of cementitious material, the amount of controlled-release retarding component is 0.010 to 0.025 parts by weight, the amount of nucleation-type early strength component is 0.080 to 0.200 parts by weight, and the amount of expansion compensation component is 0.50 to 1.50 parts by weight.

[0041] The cementitious materials include 60-70 parts by weight of ordinary silicate cement, 22-32 parts by weight of sulfoaluminate cement, and 8-18 parts by weight of granulated blast furnace slag powder.

[0042] Among them, ordinary Portland cement has a strength grade of 52.5 and a specific surface area of ​​300-360 m² / kg; sulfoaluminate cement has a strength grade of 42.5 and a specific surface area of ​​380-420 m² / kg; and granulated blast furnace slag powder has an S95 grade and a specific surface area of ​​500-550 m² / kg.

[0043] Usage instructions include: S1, ordinary silicate cement, sulfoaluminate cement, mineral powder, polycarboxylate superplasticizer and expansion compensation component are dry-mixed to obtain premixed cementitious material.

[0044] The preparation method of the expansion compensation group is as follows: calcium oxide type expanded clinker and calcium sulfoaluminate type expanded clinker are mixed at a mass ratio of 1:1 to 2:1 and ground to a specific surface area of ​​400 to 500 m² / kg to obtain the expansion compensation component.

[0045] The controlled-release retarded component suspension was prepared using a controlled-release retarded component. Specifically: The modified nanocarrier was added to deionized water and ultrasonically dispersed for 20 min. Then, a mixed solution of sodium gluconate and citric acid was added and stirred at 40–50 °C for 2–3 h for adsorption. Finally, polycarboxylate superplasticizer was added as a dispersing stabilizer and stirring was continued for 30 min to obtain a suspension containing controlled-release retarded components.

[0046] Preparation of mixing water containing nucleation-type early-strength components using nucleation-type early-strength components, specifically: Calcium nitrate and sodium silicate were dissolved in deionized water to prepare 0.5 mol / L solutions, and polycarboxylate superplasticizer was dissolved in deionized water to prepare a 5% (w / w) solution. At room temperature, the calcium nitrate solution and sodium silicate solution were simultaneously added dropwise to the PCE solution, controlling the calcium-silicon molar ratio at 1.2–1.8 and the pH value at 10.5–11.5. After the addition was complete, the mixture was stirred for 2 hours and aged for 24 hours to obtain a CSH / PCE nanocrystal suspension. Then, the CSH / PCE nanocrystal suspension was mixed with aluminum sulfate and lithium carbonate and ultrasonically dispersed for 15 minutes to obtain a nucleus-type early strength component.

[0047] S2 involves adding sand to premixed cementitious materials for dry mixing, then adding a controlled-release retarding component suspension for stirring. After stirring evenly, mixing water containing nucleation-type early-strength components is added and stirred to obtain cement paste and mortar with the characteristics of first slowing, then accelerating, and then compensating.

[0048] This invention provides a nano-carrier controlled-release composite functional admixture that is highly compatible with the OPC-SAC-GGBS ternary system, achieves controlled release of retarding components through nano-carriers, and synergistically works with CSH crystal nucleus early-strength components and expansion components. This can promote the reliable application of fast-hardening and early-strength cement-based materials in more complex engineering projects.

[0049] Example 1 Based on weight, the components of 1000 parts of cementitious material are prepared as follows: 650 parts of ordinary silicate cement, 280 parts of sulfoaluminate cement, and 70 parts of mineral powder; 0.15 parts of controlled-release retarding component (including 0.08 parts of silane-modified nano-silica / haloite composite carrier, 0.03 parts of sodium gluconate, 0.03 parts of citric acid, and 0.01 parts of polycarboxylate superplasticizer); 1.2 parts of nucleation-type early strength component (including 0.8 parts of CSH / PCE nanocrystal suspension, 0.25 parts of aluminum sulfate, and 0.15 parts of lithium carbonate); 8.0 parts of expansion compensation component (4.0 parts of calcium oxide-type expanded clinker and 4.0 parts of calcium sulfoaluminate-type expanded clinker); 2.0 parts of polycarboxylate high-performance superplasticizer; 300 parts of water; and 1200 parts of standard sand.

[0050] The preparation process is as follows: (1) Modification of nanocarrier: Mix 4 parts of nano silica and 4 parts of halloysite, add 200 parts of anhydrous ethanol and ultrasonically disperse for 30 min, add 0.5 parts of silane coupling agent (γ-aminopropyltriethoxysilane and γ-methacryloyloxypropyltrimethoxysilane in a ratio of 1:1.2), reflux at 70℃ for 5 h, centrifuge, wash and dry to obtain modified nanocarrier.

[0051] Preparation of controlled-release slow-release component: 0.08 parts of modified nanocarrier were added to 10 parts of deionized water and ultrasonically dispersed for 20 min. 0.03 parts of sodium gluconate and 0.03 parts of citric acid were added and stirred at 45℃ for 2.5 h for adsorption. 0.01 parts of polycarboxylate superplasticizer were added and stirring was continued for 30 min.

[0052] (2) Preparation of CSH / PCE nanocrystal nuclei: Calcium nitrate and sodium silicate were dissolved in deionized water to prepare 0.5 mol / L solutions, and PCE was dissolved in deionized water to prepare 5% solutions; the calcium nitrate solution and sodium silicate solution were added dropwise to the PCE solution at the same time, and the calcium-silicon molar ratio was controlled at 1.5 and the pH value was 11.0. After the addition was completed, the mixture was stirred for 2 hours and aged for 24 hours. Preparation of early strength components with crystal nuclei: 0.8 parts of CSH / PCE nanocrystal suspension were mixed with 0.25 parts of aluminum sulfate and 0.15 parts of lithium carbonate, and ultrasonically dispersed for 15 min; (3) Preparation of expansion compensation component: 4.0 parts of calcium oxide type expanded clinker and 4.0 parts of calcium sulfoaluminate type expanded clinker are mixed and ground to a specific surface area of ​​450 m² / kg.

[0053] When using it, the following steps are included: S1, add 650 parts of ordinary Portland cement, 280 parts of sulfoaluminate cement, 70 parts of mineral powder, 8.0 parts of expansion compensation component and 2.0 parts of polycarboxylate superplasticizer to the mixing pot and dry mix for 45 seconds; S2, add 1200 parts of standard sand and continue dry mixing for 30 seconds; then add the controlled-release retarding component suspension and half of the mixing water, and stir for 2 minutes; then add the nucleation type early strength component and the remaining mixing water, and stir according to the GB / T 17671-2021 standard procedure to obtain cement mortar.

[0054] Example 2 Based on weight, the components of 1000 parts of cementitious material are prepared as follows: 680 parts of ordinary silicate cement, 250 parts of sulfoaluminate cement, and 70 parts of mineral powder; 0.18 parts of controlled-release retarding component (including 0.10 parts of silane-modified nano-silica / haloite composite carrier, 0.04 parts of sodium gluconate, 0.03 parts of citric acid, and 0.01 parts of polycarboxylate superplasticizer); 1.5 parts of nucleation-type early-strength component (including 1.0 part of CSH / PCE nanocrystal suspension, 0.30 parts of aluminum sulfate, and 0.20 parts of lithium carbonate); 10.0 parts of expansion compensation component (6.0 parts of calcium oxide-type expanded clinker and 4.0 parts of calcium sulfoaluminate-type expanded clinker); 2.0 parts of polycarboxylate high-performance superplasticizer; 300 parts of water; and 1200 parts of standard sand. The remaining preparation and usage methods are the same as in Example 1.

[0055] Example 3 Based on weight, the components of 1000 parts of cementitious material are prepared as follows: 620 parts of ordinary silicate cement, 300 parts of sulfoaluminate cement, and 80 parts of mineral powder; 0.12 parts of controlled-release retarding component (including 0.06 parts of silane-modified nano-silica / haloite composite carrier, 0.03 parts of sodium gluconate, 0.02 parts of citric acid, and 0.01 parts of polycarboxylate superplasticizer); 1.0 part of nucleation-type early-strength component (including 0.7 parts of CSH / PCE nanocrystal suspension, 0.20 parts of aluminum sulfate, and 0.10 parts of lithium carbonate); 6.0 parts of expansion compensation component (3.0 parts of calcium oxide-type expanded clinker and 3.0 parts of calcium sulfoaluminate-type expanded clinker); 2.0 parts of polycarboxylate high-performance superplasticizer; 300 parts of water; and 1200 parts of standard sand. The remaining preparation and usage methods are the same as in Example 1.

[0056] Example 4 Based on weight, the components of 1000 parts of cementitious material are prepared as follows: 660 parts of ordinary silicate cement, 270 parts of sulfoaluminate cement, and 70 parts of mineral powder; 0.20 parts of controlled-release retarding component (including 0.11 parts of silane-modified nano-silica / haloite composite carrier, 0.05 parts of sodium gluconate, 0.03 parts of citric acid, and 0.01 parts of polycarboxylate superplasticizer); 1.8 parts of nucleation-type early-strength component (including 1.2 parts of CSH / PCE nanocrystal suspension, 0.40 parts of aluminum sulfate, and 0.20 parts of lithium carbonate); 12.0 parts of expansion compensation component (8.0 parts of calcium oxide-type expanded clinker and 4.0 parts of calcium sulfoaluminate-type expanded clinker); 2.0 parts of polycarboxylate high-performance superplasticizer; 300 parts of water; and 1200 parts of standard sand. The remaining preparation and usage methods are the same as in Example 1.

[0057] Example 5 Based on weight, the components of 1000 parts of cementitious material are prepared as follows: 640 parts of ordinary silicate cement, 290 parts of sulfoaluminate cement, and 70 parts of mineral powder; 0.14 parts of controlled-release retarding component (including 0.07 parts of silane-modified nano-silica / haloite composite carrier, 0.04 parts of sodium gluconate, 0.02 parts of citric acid, and 0.01 parts of polycarboxylate superplasticizer); 0.9 parts of nucleation-type early-strength component (including 0.6 parts of CSH / PCE nanocrystal suspension, 0.20 parts of aluminum sulfate, and 0.10 parts of lithium carbonate); 7.0 parts of expansion compensation component (4.0 parts of calcium oxide-type expanded clinker and 3.0 parts of calcium sulfoaluminate-type expanded clinker); 2.0 parts of polycarboxylate high-performance superplasticizer; 300 parts of water; and 1200 parts of standard sand. The remaining preparation and usage methods are the same as in Example 1.

[0058] To verify the synergistic effect of the nanocarrier-controlled release composite functional admixture of the present invention, the following comparative examples were set up: Comparative Example 1: The cementitious materials and proportions are the same as in Example 1, except that 0.15 parts of the traditional retarding component (0.07 parts of sodium gluconate and 0.08 parts of citric acid) are added, and no nucleation-type early strength component or expansion compensation component is added; Comparative Example 2: The cementitious materials and proportions are the same as in Example 1, except that 1.2 parts of the traditional early strength component (0.6 parts of aluminum sulfate and 0.6 parts of lithium carbonate) are added, and no controlled-release retarding component or expansion compensation component is added; Comparative Example 3: The cementitious materials and proportions are the same as in Example 1, except that controlled-release retarding components, nucleation-type early strength components, and expansion compensation components are not added; Comparative Example 4: The cementitious materials and proportions are the same as in Example 1, except that 0.15 parts of controlled-release retarding component and 1.2 parts of nucleation-type early strength component are added, but no expansion compensation component is added; Comparative Example 5: The cementitious materials and proportions were the same as in Example 1, except that 0.15 parts of traditional retarding component, 1.2 parts of traditional early strength component, and 8.0 parts of expansion compensation component were added (i.e., the nanocarrier controlled release technology and CSH crystal nucleus technology were not used).

[0059] The performance of the mortars and neat cement pastes prepared in Examples 1-5 and Comparative Examples 1-5 was tested, and the specific results are shown in Table 1: Table 1. Performance test results of different embodiments and comparative examples

[0060] According to the test results listed in Table 1, Comparative Example 1, while significantly prolonging the setting time and reducing fluidity loss over time by adding only a traditional retarder, sacrificed early reactivity. Comparative Example 2, while shortening the setting time by adding only a traditional early-strength agent, showed a significant deterioration in slurry workability. Comparative Example 4, although using a controlled-release retarder and a nucleation-type early-strength agent, suffered from poor volume stability in the later stages due to the lack of an expansion compensation component. Comparative Example 5, using a simple compound of a traditional retarder, early-strength agent, and expansion agent, showed some improvement, but the antagonistic effect between retarding and early strength was significant, and the fluidity loss over time remained high. In contrast, the nano-carrier controlled-release composite functional admixtures of Examples 1-5 of this invention effectively maintained high initial fluidity and 30-minute fluidity while ensuring a suitable setting time, with the fluidity loss over time controlled between 7.4% and 9.3%, significantly better than the blank group, the early-strength-only group, and the traditional compound group, indicating that this invention effectively maintained initial working performance.

[0061] Table 2. Mechanical property test results (compressive strength / MPa) of different embodiments and comparative examples

[0062] Table 3. Mechanical property test results (flexural strength / MPa) of different embodiments and comparative examples

[0063] According to the test results listed in Tables 2 and 3, Comparative Example 1, with only a retarder, showed significantly lower early-age compressive and flexural strengths at 8 hours and 1 day compared to the control group. Comparative Example 2, with only an accelerator, exhibited excellent early-strength characteristics at 8 hours and 1 day, but its strength increase from 7 days to 28 days was relatively gradual. Comparative Example 4, although employing the controlled-release and nucleation technology of this invention, showed slightly lower 28-day strength than the example due to the lack of expansion compensation. Comparative Example 5, using a traditional compounding method, showed limited improvement in early-age strength.

[0064] Examples 1-5 of this invention exhibit significant synergistic advantages: Example 1 achieved an 8-hour compressive strength of 22.5 MPa, an increase of 114.3% compared to Comparative Example 1 and 52.0% compared to the control group; its 1-day compressive strength reached 35.2 MPa, an increase of 77.8% compared to Comparative Example 1. Example 2, due to appropriately increasing the amount of CSH nuclei and the proportion of early-strength salt, achieved an 8-hour compressive strength of 25.8 MPa and a 1-day compressive strength of 38.5 MPa. Example 4, due to increasing the amount of nucleation-type early-strength component and expansion compensation component, achieved an 8-hour compressive strength of 28.5 MPa and a 1-day compressive strength of 42.0 MPa, representing the best early strength development among all examples. By 28 days, the compressive and flexural strengths of all examples were significantly higher than those of the control group and the comparative example, indicating that this invention promotes later-stage strength development.

[0065] Table 4. Volume stability test results of different embodiments and comparative examples

[0066] According to the test results listed in Table 4, Comparative Examples 1-4, without the addition of expansion compensation components or using the traditional method, all exhibited varying degrees of shrinkage, with 28-day auto-shrinkage values ​​ranging from 520 to 620 με. Although Comparative Example 5 included an expansion compensation component, the expansion agent's effectiveness was insufficient due to the antagonistic effect of the traditional retarded-early-strength system. The 28-day auto-shrinkage values ​​of Examples 1-5 of this invention were significantly reduced to 120-220 με, with both free and restricted expansion rates within reasonable ranges, indicating that the nanocarrier controlled-release technology effectively ensured the temporal synergy of the expansion components, achieving excellent volume stability. Among them, Example 4, due to its higher dosage of expansion compensation components, exhibited the best volume stability with a 28-day auto-shrinkage value of only 120 με.

[0067] In summary, the nanocarrier-based controlled-release composite functional admixture proposed in this invention is highly compatible with the OPC-SAC-GGBS ternary system. While significantly improving early-stage compressive and flexural strength at 8 hours and 1 day, it also promotes strength development at 7 days and 28 days, overcoming the shortcomings of single early-strength agents that result in slow or even reversed strength growth due to excessively rapid early hydration forming a dense coating layer. The 28-day compressive strength can reach 57–62 MPa, an improvement of 5%–13% compared to the control group.

[0068] This invention discloses a controlled-release retarding component in a nano-carrier controlled-release composite functional admixture. The retarding component is loaded onto a nano-silica / haloyrite composite carrier modified with a silane coupling agent. Organic functional groups are introduced onto the surface of the nano-carrier using a silane coupling agent (a mixture of γ-aminopropyltriethoxysilane and γ-methacryloyloxypropyltrimethoxysilane), thereby enhancing the interfacial bonding with organic retarders such as sodium gluconate and citric acid. Simultaneously, the high specific surface area of ​​nano-silica and the tubular pore structure of halloyrite provide abundant adsorption sites and confined space, allowing the retarding component to be loaded onto the carrier surface and pores through both physical adsorption and chemical bonding. The use of a silane coupling agent-modified nano-silica / haloyrite composite carrier to load the retarding component results in a controlled release characteristic of the retarding component in the alkaline environment of cement paste: a moderate initial release rate to avoid excessive retardation; and continuous release in the later stages to extend the effective retardation time. In addition, using polycarboxylate superplasticizer as a dispersing stabilizer can further ensure the uniform dispersion of nanocarriers in cement paste.

[0069] Secondly, this invention introduces CSH / PCE nanocrystals as the core material of the nucleus-type early-strength component. Through solution chemical precipitation, in the presence of polycarboxylate superplasticizer (PCE), and controlling the calcium-silicon molar ratio to 1.2–1.8, CSH nanocrystals with uniform particle size distribution and stable dispersion are prepared. In this process, PCE molecules interact with the Ca²⁺ ions on the surface of the CSH nanocrystals through their carboxyl groups. + Complexation, combined with the steric hindrance effect of polyether side chains, can inhibit the aggregation and growth of CSH crystal nuclei. Since CSH crystal nuclei have the same crystal structure as cement hydration products, they can provide homogeneous nucleation sites for CSH gel and ettringite, thus lowering the nucleation barrier. When CSH crystal nuclei are combined with aluminum sulfate and lithium carbonate, the nucleation effect of CSH crystal nuclei synergizes with the ion excitation effect of inorganic salts, resulting in a synergistic effect of 1+1>2 in early strength development.

[0070] Furthermore, this invention designs a calcium oxide-calcium sulfoaluminate composite expanding agent, which effectively compensates for early shrinkage through a dual mechanism of hydration expansion (CaO+H2O→Ca(OH)2, volume expansion of approximately 98%) in calcium oxide-type expanding clinker and ettringite expansion (C4A3S_+2CaSO4·2H2O+34H2O→2AFt+2AH3) in calcium sulfoaluminate-type expanding clinker. This is because the expansion rates and amounts of the two expanding components are complementary: the calcium oxide-type expanding agent expands faster in the early stage, which can compensate for the plastic shrinkage before initial setting; the calcium sulfoaluminate-type expanding agent expands continuously in the middle and later stages, which can compensate for the auto-shrinkage and drying shrinkage after hardening.

[0071] Finally, this invention achieves simultaneous improvement in the working performance, early mechanical properties, and volume stability of the OPC-SAC-GGBS ternary composite system through the time-series synergistic design of controlled-release retarding components, nucleation-type early-strength components, and expansion-compensating components. Specifically, the controlled-release retarding component dominates in the first stage to ensure working performance; the nucleation-type early-strength component is activated in the second stage to promote strength development; and the expansion-compensating component plays a role in the third stage to ensure volume stability. This provides strong technical support for the reliable application of rapid-hardening, early-strength cement-based materials in high-end engineering projects.

[0072] The above description is merely a preferred embodiment of the present invention and is not intended to limit the technical solution of the present invention in any way. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can be modified and replaced in several simple ways, and these modifications and replacements are all within the scope of protection covered by the claims.

Claims

1. A nanocarrier-based controlled-release composite functional admixture, characterized in that, include: Controlled-release retarding components include nanocarriers, retarding active components, and dispersing stabilizers; The nanocarrier is a silane coupling agent modified nano-silica / haloite composite powder; the retarding active component is a compound of sodium gluconate and citric acid; and the dispersing stabilizer is a polycarboxylate superplasticizer. Nucleus-type early strength components include CSH / PCE nanocrystals and inorganic early strength salts; Among them, the inorganic early-strength salt is a compound of aluminum sulfate and lithium carbonate; The expansion compensation component includes a calcium oxide-calcium sulfoaluminate composite expansion agent.

2. The nanocarrier controlled-release composite functional admixture according to claim 1, characterized in that, Sodium gluconate accounts for 40% to 60% of the total mass of the retarding active components, and citric acid accounts for 40% to 60% of the total mass of the retarding active components.

3. The nanocarrier controlled-release composite functional admixture according to claim 1, characterized in that, The preparation method of the controlled-release retarded component is as follows: a silane coupling agent modified nano-silica / haloite composite carrier is added to deionized water for dispersion, then a mixed solution of sodium gluconate and citric acid is added for stirring and adsorption, and finally a polycarboxylate superplasticizer as a dispersion stabilizer is added and stirring is continued to obtain a suspension containing the controlled-release retarded component.

4. The nanocarrier controlled-release composite functional admixture according to claim 3, characterized in that, The preparation method of the nanocarrier is as follows: nano silica and halloysite are mixed in a mass ratio of (1:2) to (2:1) and then dispersed in anhydrous ethanol. Then, a silane coupling agent is added dropwise, followed by reflux reaction. After centrifugation, washing and drying, a silane coupling agent modified nano silica / haloysite composite carrier is obtained. The silane coupling agent is composed of γ-aminopropyltriethoxysilane and γ-methacryloyloxypropyltrimethoxysilane in a mass ratio of (1:1) to (1:1.5).

5. The nanocarrier controlled-release composite functional admixture according to claim 1, characterized in that, The amount of CSH / PCE nanocrystal nuclei used is 60% to 80% of the total mass of the nucleus-type early strength component, and the amount of inorganic early strength salt used is 20% to 40% of the total mass of the nucleus-type early strength component.

6. The nanocarrier controlled-release composite functional admixture according to claim 5, characterized in that, The preparation method of CSH / PCE nanocrystal nuclei is as follows: calcium nitrate and sodium silicate are dissolved in deionized water to prepare a 0.5 mol / L solution, and polycarboxylate superplasticizer is dissolved in deionized water to prepare a 5% (w / w) solution. At room temperature, calcium nitrate solution and sodium silicate solution were simultaneously added dropwise to PCE solution, with the calcium-silicon molar ratio controlled at 1.2–1.

8. During the addition process, the mixture was continuously stirred and the pH value was controlled at 10.5–11.

5. After the addition was complete, stirring was continued for 2 hours, followed by aging to obtain a CSH / PCE nanocrystal suspension, in which the CSH solid content was 5% to 10%.

7. The nanocarrier controlled-release composite functional admixture according to claim 1, characterized in that, Aluminum sulfate accounts for 50% to 70% of the total mass of inorganic early-strength salts, and lithium carbonate accounts for 30% to 50% of the total mass of inorganic early-strength salts.

8. The nanocarrier controlled-release composite functional admixture according to claim 1, characterized in that, In the expansion compensation component, the mass ratio of calcium oxide type expansion component to calcium sulfoaluminate type expansion component is 1:1 to 2:

1.

9. The application of a nanocarrier controlled-release composite functional additive as described in any one of claims 1 to 8 in an OPC-SAC-GGBS ternary composite gelling system.

10. The application according to claim 9, characterized in that, Based on 100 parts by weight of cementitious materials, the amount of controlled-release retarding component is 0.010–0.025 parts by weight, the amount of nucleation-type early-strength component is 0.080–0.200 parts by weight, and the amount of expansion-compensating component is 0.50–1.50 parts by weight; wherein, the cementitious materials include 60–70 parts by weight of ordinary Portland cement, 22–32 parts by weight of sulfoaluminate cement, and 8–18 parts by weight of granulated blast furnace slag powder; Usage instructions include: S1, ordinary silicate cement, sulfoaluminate cement, mineral powder, polycarboxylate superplasticizer and expansion compensation component are dry mixed to obtain premixed cementitious material; A controlled-release retarded component suspension was prepared using a controlled-release retarded component; Preparation of mixing water containing nucleation-type early strength components using nucleation-type early strength components; S2 involves adding sand to premixed cementitious materials for dry mixing, then adding a controlled-release retarding component suspension for stirring. After stirring evenly, mixing water containing nucleation-type early-strength components is added and stirred to obtain cement paste and mortar with the characteristics of first slowing, then accelerating, and then compensating.

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