Special concrete for super high-rise pumping and preparation method thereof

Abstract

The invention relates to the technical field of building materials, and discloses special concrete for super high-rise pumping and a preparation method thereof, the concrete comprises the following components: Portland cement, graded basalt aggregate, superfine metakaolin, modified nano silica sol, phase change energy storage microcapsules and a ternary coupling composite admixture; the ternary coupling composite admixture comprises aminated zeolite grafted liquid crystal polymer microspheres, a magnesium phosphate / zeolite slow-release carrier and carboxylated hybrid fibers, the preparation method comprises the steps of aggregate interface optimization, ternary coupling additive preparation, gradient synergistic mixing and dynamic rheological regulation. According to the invention, the structural defect rate can be obviously reduced and the service life can be prolonged in engineering scenes such as super high-rise pumping and large-volume pouring.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials, in particular to a special concrete for super-high-rise pumping and a preparation method thereof. Background Art

[0002] In super-high-rise buildings and large-volume concrete projects, traditional concrete technology faces a common challenge: the release dynamics of functional components are insufficiently compatible with construction conditions. The static release pattern of conventional water reducers struggles to match the dynamic changes in shear rate during pumping, leading to increased slump loss over time. Existing slow-release carriers are susceptible to release rate instability due to temperature and humidity fluctuations. The synergistic failure of these two factors directly weakens the concrete's ability to maintain workability.

[0003] On the other hand, the coupling of early cement hydration heat release and pumping frictional temperature rise can induce significant temperature gradients. Traditional temperature control methods, lacking a synergistic mechanism for thermal buffering and stress dissipation, struggle to suppress the propagation of microcracks caused by thermal stress concentration. Furthermore, single fiber-reinforced materials have limited effectiveness in resisting multi-scale cracks. Furthermore, rheological property control often relies on the extensive addition of chemical admixtures, which fail to align with the timing of cement hydration. This leads to a mismatch between the slurry's rheological behavior and the shear conditions during pumping, exacerbating the risk of pipe blockage.

[0004] The fragmented control of these multi-dimensional properties has become a bottleneck restricting the development of high-durability concrete, and it is urgent to achieve cross-scale collaborative optimization through the systematic coupling of material design and process innovation. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the present invention provides a special concrete for super-high-rise pumping and a preparation method thereof, which solves the problem of coordinated loss of control between functional component release, thermal-mechanical stability and rheological properties of traditional concrete.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions: A first aspect of the present invention provides a special concrete for super-high-rise pumping, which comprises the following components by weight: 350-400 parts of Portland cement; 700-750 parts of graded basalt aggregate; 45-55 parts of ultrafine metakaolin; 20-30 parts of modified nano-silica sol; 12-18 parts of phase change energy storage microcapsules; and 8.0-9.0 parts of a ternary coupling composite admixture.

[0007] The ternary coupling composite admixture comprises: 3.0-3.5 parts of amino zeolite grafted liquid crystal polymer microspheres; 2.5-3.0 parts of magnesium phosphate / zeolite slow-release carriers; and 2.3-2.7 parts of carboxylated hybrid fibers.

[0008] The core of this invention is to build a multi-component synergistic network to overcome the problem of rheological degradation during ultra-long-distance pumping. Through the selection and proportioning of specific components, the concrete system achieves dynamic adaptation between the material's microstructure and macroscopic pumping behavior. The specific component composition and mechanism of action are as follows: Portland cement and graded basalt aggregate form the system matrix. C80-grade or higher Portland cement provides a high-strength matrix, combined with 5-15mm continuously graded basalt aggregate to form a dense, packed structure. Specific pretreatment of the basalt aggregate reduces its surface energy, weakening the interfacial friction between it and the cement paste, creating a low-resistance foundation for high-pressure pumping.

[0009] Ultrafine metakaolin and modified nano-silica sol synergistically regulate the paste microstructure. Ultrafine metakaolin fills the gaps between cement particles and participates in secondary hydration reactions. Its flaky structure creates a directional alignment effect under shear. Modified nano-silica sol chemically bonds with cement minerals through surface silanol groups, creating steric hindrance and suppressing viscosity fluctuations caused by particle agglomeration.

[0010] Phase-change energy storage microcapsules are embedded to achieve thermal field equilibrium. These microcapsules, formed by encapsulating octadecane with silica, absorb frictional heat during pumping and store excess heat through a solid-liquid phase transition. The microcapsule's phase-change temperature window matches the temperature curve of the pumping pipe wall, effectively delaying the premature onset of the cement hydration exothermic peak.

[0011] A ternary coupled composite admixture system achieves dynamic response. The admixture comprises three functional units: amino-zeolite-grafted liquid crystal polymer microspheres respond to shear stress changes through molecular conformational transitions, and their grafted structure ensures stable dispersion of the functional units in the cement paste; a magnesium phosphate / zeolite sustained-release carrier controls the release sequence of the inhibitor through the thermal expansion effect of its crystal structure, achieving hydration regulation synchronized with the pumping process; and a carboxylated hybrid fiber network, through chemical bonding and physical entanglement of surface functional groups, constructs a three-dimensional support framework within the rheological system.

[0012] Through the synergistic interaction of interfacial chemistry, physical field response, and energy conversion mechanisms, the various components enable the concrete to develop intelligent rheological behavior characterized by shear-thinning and thixotropic recovery during pumping. The conformational transition of the liquid crystal microspheres and the thermally responsive release of the sustained-release carrier create a temporally coupled effect. This, combined with the dynamic reconfiguration of the fiber network, maintains the slurry's stable performance under high pressure and variable temperature conditions.

[0013] Preferably, the amino zeolite grafted liquid crystal polymer microspheres are designed with a grafting rate of 70-75%. This range achieves functional stability by balancing the coverage of zeolite surface active sites and the freedom of movement of liquid crystal segments. When the grafting rate is lower than 70%, the unreacted amino sites are easily reacted with Ca in the cement paste. 2+Chelation occurs, resulting in premature inactivation of the carrier; and a grafting rate higher than 75% will cause excessive entanglement of the liquid crystal molecular chains, weakening their shear response sensitivity.

[0014] The liquid crystal polymer matrix is ​​a 4-vinyltriphenylene derivative. The rigid biphenyl elements in its molecular structure form a stable nematic phase, which undergoes a reversible phase transition under the shear field of pumping. This conformational change precisely matches the shear stress of the concrete pump pipe wall, achieving on-demand activation of the water reducer's function.

[0015] The zeolite carrier is NH2-ZSM5 molecular sieve. Its regular pore structure of 0.55-0.60 nm provides spatial confinement for the grafting reaction, forcing the liquid crystal monomers to preferentially graft to amino sites on the zeolite's outer surface, thus avoiding mass transfer resistance caused by pore blockage. The microspheres are controlled within a particle size range of 70-130 nm, creating a "rolling effect" between cement particles while maintaining uniform dispersion through Brownian motion. A surface zeta potential of -25-30 mV ensures colloidal stability in highly alkaline environments.

[0016] Preferably, the magnesium phosphate / zeolite sustained-release carrier is constructed by precisely controlling the Mg / P molar ratio to be 1.2 to 1.5:1 to construct a crystal structure with gradient response characteristics. When the Mg / P ratio is lower than 1.2, too many POP segments are formed in the magnesium phosphate lattice, resulting in insufficient thermal expansion coefficient and inability to effectively trigger the release of the sustained-release agent; when it is higher than 1.5, the Mg in the lattice is too large to form a POP segment. 2+ Supersaturation induces lattice distortion, causing the support to disintegrate prematurely in an alkaline environment.

[0017] The zeolite carrier is an NH2-ZSM5 molecular sieve. Its 0.55nm pore size creates a size-matching effect with the kinetic diameter of the magnesium phosphate precursor ions, ensuring that the magnesium phosphate preferentially heterogeneously nucleates and grows on the zeolite's outer surface. The amino functional groups bind to oxygen vacancies in the magnesium phosphate lattice through coordination bonds. This strong interaction ensures that the carrier maintains its structural integrity during the initial stages of cement hydration.

[0018] The carrier crystal is designed with a multi-level pore structure, comprising dual channels of 30-50 nm macropores and 2-5 nm mesopores. The macropores serve as storage chambers for the sustained-release agent, while the zinc oxide nanorod arrays loaded onto the mesopore walls form a mechanical gate. When the temperature exceeds 55°C, the magnesium phosphate lattice expands, driving the nanorods to topple, initiating a non-Fickian diffusion pathway and enabling the on-demand release of sodium gluconate. The diffusion coefficient is 2-3 orders of magnitude higher than that of conventional channels.

[0019] Preferably, the carboxylated hybrid fiber adopts a graphene / silicon carbide composite matrix, and realizes the synergistic effect of rheological regulation and mechanical enhancement through a geometric design with a diameter of 0.5 to 1.2 μm and an aspect ratio of 200 to 300. When the fiber diameter is less than 0.5 μm, the excessively high specific surface area easily induces an agglomeration effect dominated by van der Waals forces, destroying the uniformity of the slurry; and fibers exceeding 1.2 μm are difficult to align in a shear field due to significant inertia effects. The setting of an aspect ratio of 200 to 300 enables the fibers to form a three-dimensional network across the gaps between cement particles, while avoiding the risk of entanglement and breakage due to excessive length.

[0020] The carboxyl density on the fiber surface is controlled in the range of 7.5 to 8.5 μmol / g, which is achieved by oxidation etching with sulfuric acid / nitric acid mixed acid. When the density is lower than 7.5 μmol / g, the Ca between the fiber and the cement hydration product is 2+ The chelating sites are insufficient and the interface binding energy is insufficient to resist pumping shear damage; if the concentration is higher than 8.5 μmol / g, the carboxyl groups are too dense, causing local hydrophilic aggregation and destroying the fiber-paste interface compatibility.

[0021] The graphene / silicon carbide composite structure imparts multi-scale reinforcement properties to the fibers: Graphene sheets form a continuous conductive path through π-π stacking, dissipating static electricity buildup during pumping. Silicon carbide whiskers are embedded between the graphene layers at angles of 45° to 60°, providing a rigid framework that blocks microcrack propagation. Carboxyl functional groups are directionally grafted onto the ends of the silicon carbide whiskers via chemical vapor deposition, creating a "pinning effect" that gives the fibers a radial distribution configuration within the slurry.

[0022] Preferably, the phase-change energy storage microcapsules adopt an octadecane / SiO2 core-shell structure design, achieving an optimal balance between thermal energy and mechanical properties through the synergistic matching of a particle size of 80-120 μm and a shell thickness of 10-15 μm. When the particle size is less than 80 μm, the microcapsule specific surface area increases sharply, resulting in excessive chemical bonding between the hydroxyl groups on the SiO2 shell and the cement paste, causing an abnormal increase in localized slurry viscosity. When the particle size exceeds 120 μm, the self-gravity effect causes sedimentation and stratification during pumping, which destroys the homogeneity of the concrete.

[0023] The shell thickness of 10-15 μm is based on a mechanism that compensates for the difference in thermal expansion coefficients between the core and shell materials. The octadecane core material experiences a volume expansion rate of 8-12% within the phase transition range of 25-35°C, while the SiO2 shell absorbs the core material's expansion stress through elastic deformation. The shell's Young's modulus is controlled within the 15-20 GPa stiffness range, which provides resistance to shear extrusion from the pumping tube wall while avoiding brittle fracture due to excessive rigidity.

[0024] The surface of the microcapsule is modified by aminosilane coupling agent, and its surface energy is increased from 45mJ / m 2 Reduced to 28-32 mJ / m2 , forming a controllable weak interfacial bond with the cement paste. This characteristic enables the microcapsules to produce a Leidenfrost effect in the pumping shear field: while the core material's phase transition absorbs heat and reduces interfacial frictional heat, the low-surface-energy shell induces the slurry to form a nanoscale lubricating water film. This dual effect reduces the pipe wall friction coefficient to 0.12-0.15. A shell-core mass ratio of 1:4-1:5 ensures a dynamic match between the phase transition enthalpy and the frictional heat generated during the pumping process, enabling active regulation of the system's temperature rise rate.

[0025] The second aspect of the present invention provides a method for preparing the special concrete for super high-rise pumping according to the first aspect of the present invention, comprising the following steps: Step (a), aggregate interface optimization: 1. Low temperature embrittlement treatment The basalt aggregate was placed in a liquid nitrogen environment, the temperature was controlled at -190 to -200°C, and the treatment lasted for 36 to 60 hours, during which 3 to 5 thermal shock cycles were performed (30 minutes of freezing and 10 minutes of warming to 25°C each time).

[0026] The ultra-low temperature of liquid nitrogen triggers the expansion of microcracks inside the aggregate. The thermal shock cycle generates stress differences through sudden temperature changes, preferentially forming controllable fracture surfaces along the grain boundaries, thereby reducing the energy consumption of subsequent crushing.

[0027] 2. Ball milling The brittle aggregate was transferred to a planetary ball mill and milled at 550-650 r / min for 1.5-2.5 hours using zirconia grinding balls with a diameter of 3-6 mm to obtain spherical aggregate with a sphericity greater than 0.92.

[0028] The high hardness of the zirconia grinding balls (Mohs hardness 8.5) works synergistically with the planetary centrifugal force to eliminate the sharp edges of the aggregate through a dual mechanism of collision and crushing. The spherical structure increases the proportion of rolling friction between aggregates during pumping to more than 85%.

[0029] Step (b), preparation of ternary coupling admixture: 1. Synthesis of Aminated Zeolite Grafted Liquid Crystalline Polymer Microspheres 4-vinyltriphenylene derivative liquid crystal microspheres and NH2-ZSM5 zeolite are dispersed in DMF (solid-liquid ratio 1:8-1.12) at a molar ratio of 1:1.0-1.5, refluxed at 110-130°C and 0.2-0.4 MPa nitrogen pressure for 5-7 hours, and centrifugally dried to obtain composite microspheres with a grafting rate of 70-75%.

[0030] Nitrogen pressure inhibits the vaporization of DMF solvent, ensuring the stability of the reaction interface; the amino groups on the zeolite surface undergo Michael addition reaction with the liquid crystal monomers, and the grafting sites are concentrated in the mesoporous area on the outer surface of the zeolite to avoid pore blockage.

[0031] 2. Carboxylation hybrid fiber treatment The graphene / silicon carbide fiber was immersed in a concentrated sulfuric acid / nitric acid mixture (volume ratio 2.5-3.5:1), ultrasonically treated at 400-600W for 25-35min, washed with water to a pH of 6.5-7.5, and then vacuum dried at 60-80°C for 8-12 hours.

[0032] Mixed acid oxidation etching preferentially attacks the silicon carbide grain boundaries, exposing the carboxyl groups at the graphene edges; the ultrasonic cavitation effect promotes the acid to penetrate into the interlayers inside the fiber, forming a gradient carboxyl distribution (surface density 7.5-8.5 μmol / g, core <2 μmol / g).

[0033] Step (c), gradient synergistic mixing: 1.First-stage low-temperature mixing In an environment of 3-8°C, silicate cement, ultrafine metakaolin and 60-75% of the total water are premixed at 100-140 r / min for 1-2 minutes, and the modified nano-silica sol is added and stirred for 4-6 minutes.

[0034] Low temperature inhibits the initial hydration of cement. Silica sol forms prehydrated micelles (particle size 80-120 nm) with cement particles through surface silanol groups. The outer layer of the micelles adsorbs kaolin flake particles to form a "core-shell" structure.

[0035] 2. Secondary activation mixing Heat to 40-50℃, add ternary coupling admixture, and heat at 160-200r / min and 120-150s -1 Stir at a shear rate for 7 to 9 minutes, and simultaneously inject the remaining 25 to 35% of water.

[0036] The functional groups of the admixture are activated by heating, and the liquid crystal microspheres undergo a nematic-isotropic phase transition in the shear field, releasing the pre-adsorbed water-reducing components; the gradient water addition strategy gradually increases the water-binder ratio from 0.18 to 0.26-0.30, achieving gradual regulation of rheological properties.

[0037] Step (d) Dynamic rheological control: 1. Phase change microcapsule incorporation Pre-disperse octadecane / SiO2 microcapsules and mixing water in a mass ratio of 1:3-5, and stir at a low speed of 50-70 r / min for 2-4 minutes.

[0038] Pre-dispersion forms a microcapsule-water suspension (Zeta potential -35 to -40 mV), and electrostatic repulsion is used to prevent microcapsule aggregation; low-speed stirring avoids mechanical damage to the capsule shell.

[0039] 2. Static maintenance and control The mixture was cured at 20-25°C and 60-75% humidity for 25-35 minutes, and the zeta potential of the slurry was detected every 10 minutes until the threshold value of -20±2mV was reached.

[0040] During the static period, cement particles are reorganized into a honeycomb structure through electrostatic attraction (Zeta potential regulation), and microcapsules are embedded in the pores of the slurry (accounting for 12-15 vol%), forming a thermal-mechanical coupling buffer network.

[0041] The present invention provides a special concrete for super high-rise pumping and a preparation method thereof. It has the following beneficial effects: 1. Through the dynamic phase change response mechanism of liquid crystal polymer microspheres, the water reducer of the present invention can regulate the release rate in real time according to the change of pumping shear force, avoiding the slump loss caused by premature release in traditional processes, and achieving long-term maintenance of concrete workability.

[0042] 2. The present invention forms high-strength interfacial bonds with cement hydration products through the gradient chelation effect on the surface of carboxylated hybrid fibers, constructs a multi-level energy dissipation barrier on the crack propagation path, significantly inhibits the initiation and propagation of microcracks, and improves the durability of concrete structures.

[0043] 3. The present invention achieves a time-matched release of sodium gluconate by coupling the lattice expansion characteristics of the magnesium phosphate / zeolite composite carrier with the gated diffusion mechanism of the zeolite pores, solving the release mismatch problem that is prone to occur in traditional sustained-release systems under temperature-dependent conditions.

[0044] 4. The present invention delays the early hydration exothermic process of cement through the synergistic effect of low-temperature pre-hydrated micelles and shear-activated gradient water addition process, while optimizing the dispersion state of slurry particles, making the pumping rheological curve highly compatible with construction shear conditions.

[0045] 5. The present invention combines the thermal buffering effect of phase change microcapsules with the dispersion and homogenization effect of Zeta potential regulation to effectively suppress the thermal stress concentration caused by pumping friction temperature rise, ensuring that the strength development stability of concrete remains in a complex temperature change environment. DETAILED DESCRIPTION

[0046] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0047] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0048] Example 1: The special concrete comprises the following components by weight: 350 parts of Portland cement; 700 parts of graded basalt aggregate; 45 parts of ultrafine metakaolin; 20 parts of modified nano-silica sol; 12 parts of phase change energy storage microcapsules; 8.0 parts of ternary coupling composite admixture; which contains: 3.0 parts of aminated zeolite grafted liquid crystal polymer microspheres; 2.5 parts of magnesium phosphate / zeolite sustained-release carrier; 2.5 parts of carboxylated hybrid fiber.

[0049] The preparation steps of this special concrete are as follows: 1. Aggregate interface optimization The basalt aggregate was placed in liquid nitrogen at -190 °C for 36 h and subjected to three thermal shock cycles (freezing for 30 min + warming to 25 °C for 10 min).

[0050] Ball milling: Use 3 mm diameter zirconia grinding balls and ball mill at 550 r / min for 1.5 hours to obtain aggregate with a sphericity of 0.93.

[0051] 2. Preparation of admixtures Synthesis of liquid crystal microspheres: Liquid crystal microspheres and NH2-ZSM5 zeolite were reacted in DMF (solid-liquid ratio 1:8) at a molar ratio of 1:1.0, and refluxed at 110°C and 0.2 MPa nitrogen for 5 hours, with a grafting rate of 70%.

[0052] Carboxylation fiber treatment: Graphene / silicon carbide fiber was ultrasonically treated in sulfuric acid / nitric acid (2.5:1) for 25 min (400 W), and the surface carboxyl density after drying was 7.5 μmol / g.

[0053] 3. Gradient Co-mixing Primary mixing: premix cement, metakaolin and 60% water at 4°C (100 r / min, 1 min), add silica sol and stir for 4 min.

[0054] Secondary mixing: heat to 40℃, add admixture and mix at 160r / min for 120s -1 The mixture was stirred at a shear rate for 7 min, and the remaining 40% water (water-to-binder ratio 0.26) was injected simultaneously.

[0055] 3. Dynamic rheological control Incorporation of microcapsules: pre-disperse octadecane / SiO2 microcapsules and water at a ratio of 1:3 and stir at 50 rpm for 2 min.

[0056] Static curing: curing at 22℃ and 65% humidity for 25 minutes, and adjusting the Zeta potential to -20mV.

[0057] Example 2: The special concrete comprises the following components by weight: 375 parts of Portland cement; 725 parts of graded basalt aggregate; 50 parts of ultrafine metakaolin; 25 parts of modified nano-silica sol; 15 parts of phase change energy storage microcapsules; 8.5 parts of ternary coupling composite admixture; which contains: 3.25 parts of aminated zeolite grafted liquid crystal polymer microspheres; 2.8 parts of magnesium phosphate / zeolite sustained-release carrier; 2.5 parts of carboxylated hybrid fiber.

[0058] The preparation steps of this special concrete are as follows: 1. Aggregate interface optimization The aggregate was treated at -195℃ liquid nitrogen for 48 hours and four thermal shock cycles.

[0059] Ball milling: 4.5 mm diameter grinding balls, 600 r / min for 2.0 hours, sphericity 0.95.

[0060] 2. Preparation of admixtures Synthesis of liquid crystal microspheres: 1:1.25 molar ratio, DMF solid-liquid ratio 1:10, reaction at 120°C, 0.3 MPa for 6 hours, grafting rate 72%.

[0061] Carboxylated fiber: sulfuric acid / nitric acid 3.0:1 mixture, 500W ultrasound for 30 min, carboxyl density 8.0 μmol / g.

[0062] 3. Gradient Co-mixing Primary mixing: premix 65% water at 5°C (120 r / min, 1.5 min) and stir for 5 min to form micelles.

[0063] Secondary mixing: 45℃, 180r / min, 135s -1 Shear stirring for 8 minutes, water-to-cement ratio 0.28.

[0064] 4. Dynamic rheological control Microcapsule incorporation: pre-disperse at a mass ratio of 1:4 and stir at 60 rpm for 3 min.

[0065] Curing: 23℃, 70% humidity for 30 min, Zeta potential -21 mV.

[0066] Example 3: The special concrete comprises the following components by weight: 400 parts of Portland cement; 750 parts of graded basalt aggregate; 55 parts of ultrafine metakaolin; 30 parts of modified nano-silica sol; 18 parts of phase change energy storage microcapsules; 9.0 parts of ternary coupling composite admixture; comprising: 3.5 parts of aminated zeolite grafted liquid crystal polymer microspheres; 3.0 parts of magnesium phosphate / zeolite sustained-release carrier; 2.7 parts of carboxylated hybrid fiber.

[0067] The preparation steps of this special concrete are as follows: 1. Aggregate interface optimization The aggregate was treated at -200℃ liquid nitrogen for 60 hours and 5 thermal shock cycles.

[0068] Ball milling: 6 mm diameter grinding balls, 650 r / min for 2.5 hours, sphericity 0.96.

[0069] 2. Preparation of admixtures Liquid crystal microsphere synthesis: 1:1.5 molar ratio, DMF solid-liquid ratio 1:12, reflux at 130°C, 0.4 MPa for 7 hours, grafting rate 75%.

[0070] Carboxylated fiber: sulfuric acid / nitric acid 3.5:1 mixture, 600W ultrasound for 35 min, carboxyl density 8.5μmol / g.

[0071] 3. Gradient Co-mixing Primary mixing: premix 75% water at 8°C (140 r / min, 2 min), add silica sol and stir for 6 min.

[0072] Secondary mixing: stirring at 200 r / min, 150 s-1 shearing speed for 9 min at 50 ° C, with a water-to-binder ratio of 0.30.

[0073] 4. Dynamic rheological control Microcapsule incorporation: pre-disperse at a mass ratio of 1:5 and stir at 70 rpm for 4 min.

[0074] Curing: 25℃, 75% humidity for 35min, Zeta potential -22mV.

[0075] Comparative Example 1: Compared with Example 1, the difference is that the liquid nitrogen embrittlement treatment is removed, and the basalt aggregate is directly crushed to the same particle size using a jaw crusher without ball milling treatment.

[0076] Comparative Example 2: Compared with Example 1, the difference is that the thermal shock cycle is eliminated and only continuous low-temperature treatment (-190° C., 36 hours, no sudden temperature change) is performed.

[0077] Comparative Example 3: Compared with Example 2, the difference is that the amino zeolite grafted liquid crystal microspheres are removed from the ternary coupling admixture and replaced with an equal amount of polycarboxylate water-reducing agent powder.

[0078] Comparative Example 4: Compared with Example 2, the difference is that the grafting rate of liquid crystal microspheres is reduced to 50% (the reaction time is adjusted to 3 hours, and the other conditions remain unchanged).

[0079] Comparative Example 5: Compared with Example 3, the difference is that the carboxylated hybrid fibers are replaced by untreated original fibers (surface carboxyl density < 2 μmol / g).

[0080] Comparative Example 6: Compared with Example 3, the difference is that the low-temperature premixing step is eliminated in the gradient synergistic mixing, and all raw materials are mixed at 25° C. at one time.

[0081] Comparative Example 7: Compared with Example 1, the difference is that phase change microcapsules are not incorporated in the dynamic rheology control stage, and are replaced by quartz sand powder in equal amount.

[0082] Comparative Example 8: Compared with Example 2, the difference is that the Mg / P molar ratio of the magnesium phosphate / zeolite sustained-release carrier is adjusted to 1.0:1.

[0083] Comparative Example 9: Compared with Example 3, the difference is that the Zeta potential control is cancelled during the static curing stage, and standard curing is directly performed for 24 hours.

[0084] Test Example 1: Objective: To verify the effects of liquid nitrogen low-temperature embrittlement and ball milling on aggregate sphericity and pumping resistance.

[0085] The experimental steps are as follows: 1. Sample Preparation Example group: The spherical basalt aggregate prepared in Examples 1 to 3 (after liquid nitrogen embrittlement and ball milling) was taken.

[0086] Comparative group: Comparative Example 1: Basalt aggregate directly crushed by a jaw crusher (untreated).

[0087] Comparative Example 2: Aggregate subjected to continuous low-temperature treatment with liquid nitrogen only (without thermal shock cycle).

[0088] 2. Aggregate sphericity test is as follows: 1) Sample processing: Coarse aggregate (particle size 5-20 mm) was separated from the concrete, 100 pieces were randomly selected, washed with clean water and dried to constant weight.

[0089] 2) 3D imaging: A single aggregate was placed on a rotating platform, and photos were taken at three orthogonal viewing angles of 0°, 90°, and 180° using a high-resolution industrial camera (≥12 million pixels).

[0090] 3) Sphericity calculation: Import image analysis software (such as MATLAB) to calculate the volume projection ratio, according to the formula: sphericity = (36πV 2 ) (1 / 3) / S , where V is the volume and S is the surface area.

[0091] 3. Pumping resistance test is as follows: 1) Pumping system configuration: A hydraulic piston pump (power 45kW) is used to connect an S-shaped metal pipe with a diameter of 125mm and a total length of 80m (including 3 90° elbows).

[0092] 2) Pressure monitoring: A pressure sensor (range 0-40 MPa, accuracy ±0.2%) was installed at the pump outlet to collect data at a frequency of 100 Hz.

[0093] 3) Test execution: Continuous pumping at a constant pump speed of 40L / min for 5 minutes: Initial pumping pressure: Take the peak pressure in the first 10 seconds after startup Stabilize pumping pressure: take the average pressure value of the last 2 minutes.

[0094] The test results are shown in Table 1: Table 1 Summary of aggregate treatment effect test data From the test results in Table 1, we can get: The ultra-low temperature environment of liquid nitrogen induces embrittlement of the grain boundaries within the basalt aggregate. Combined with the temperature gradient stress generated by periodic thermal shock cycles, this preferentially forms a network of directional microcracks along mineral phase interfaces (such as the pyroxene-plagioclase boundary). This synergistic effect improves aggregate crushing efficiency by approximately 40%. Experimental data shows that the aggregate sphericity of Examples 1-3, which underwent three thermal shock treatments, reached 0.93-0.96, significantly higher than that of Comparative Example 2 (sphericity 0.85), which was treated only with continuous low temperatures. This demonstrates the enhanced effect of thermal stress differentials on selective grain boundary fracture.

[0095] The high-energy collision and crushing of the zirconia grinding balls (Mohs hardness 8.5) in the planetary ball mill further eliminates angular surfaces on the aggregate, creating a spherical geometry. Experimental data shows that the stable pumping pressure of the Example group (4.5-5.2 MPa) is 47-54% lower than that of Comparative Example 1 (9.8 MPa). The fundamental reason is that during the pumping process, rolling friction accounts for over 85% of the aggregate with a sphericity greater than 0.92, while sliding friction dominates in the sharp-edged Comparative Example 1 (over 60%), resulting in a doubling of shear stress on the pipe wall.

[0096] The synergistic effect of liquid nitrogen embrittlement and ball milling transforms the aggregate crushing mode from traditional mechanical energy "hard crushing" to thermal-mechanical coupled "pre-damage-guided crushing." The standard deviation of sphericity of the milled aggregate in Example 3 was only 0.03 (compared to 0.05 in Comparative Example 1), demonstrating that this process significantly improves aggregate morphology homogeneity and, in turn, reduces random fluctuations in pumping resistance (pressure fluctuations in the Example group were ±0.2-0.4 MPa, while in Comparative Example 1, they reached ±0.6 MPa), providing a material foundation for ultra-high-rise pumping stability.

[0097] Test Example 2: Objective: To verify the effect of ternary coupling admixture on slump retention and crack growth resistance.

[0098] The experimental steps are as follows: 1. Sample Preparation Example group: concrete specimens prepared in Examples 1 to 3 were taken.

[0099] Comparative Example Group: Concrete specimens prepared in Examples 3 to 5 and 8 2. The slump retention rate test is as follows: 1) Initial slump determination: Load the fresh concrete into the slump cone (upper opening inner diameter 100mm, lower opening 200mm, height 300mm) in three layers, tamp each layer 25 times, smooth the opening of the cone and lift the cone vertically.

[0100] Measure the concrete slump height immediately and calculate the slump value (cylinder height 300mm - height of the highest point after collapse).

[0101] 2) Sample rest: The remaining concrete was placed in a sealed container and placed in an environment of 25±2°C and 60±5% humidity for 120 minutes, during which time it was manually stirred 5 times every 30 minutes to prevent segregation.

[0102] 3) 120min slump measurement: After the standing period, re-stir the concrete for 30 seconds and measure the slump again according to the method in step 1.

[0103] 3. Crack propagation resistance test 1) Specimen preparation: Pour the concrete into a 600mm×600mm×60mm steel mold, smooth the surface, cover with plastic film, and let it stand for 2 hours for initial setting.

[0104] 2) Forced drying triggers cracking: The plastic film was removed and an axial flow fan (wind speed 5 m / s) was set 50 cm above the specimen to continuously blow on the surface. The ambient temperature was controlled at 25 ± 2 °C for 24 h.

[0105] 3) Quantification of crack area: Use a high-definition camera to photograph the specimen surface, import the image analysis software to calibrate the actual size, select all visible cracks to generate total area data, and convert it to crack area per square meter (mm 2 / m 2 ).

[0106] The test results are shown in Table 2: Table 2 Admixture function test data sample Initial slump (mm) 120min slump (mm) <![CDATA[24h crack area (mm 2 / m 2 )]]> Example 1 243±4 218±6 85±12 Example 2 235±3 224±5 78±9 Example 3 251±5 232±7 63±8 Comparative Example 3 228±6 158±9 245±18 Comparative Example 4 223±4 182±7 176±15 Comparative Example 5 237±5 210±6 142±11 Comparative Example 8 232±5 192±8 158±13 From the test results in Table 2, we can get: Under the shear force of pumping, the liquid crystal polymer microspheres undergo a phase transition from nematic to isotropic, releasing the pre-adsorbed water-reducing component. Experimental data show that the 120-minute slump retention of Examples 1-3 exceeds 90% (for example, Example 3 drops from 251 mm to 232 mm), while the slump loss of Comparative Example 3, after replacing it with a conventional water-reducing agent, reaches 30.7% (228 → 158 mm), confirming the liquid crystal microspheres' intelligent release mechanism in dynamic response to shear force. The liquid crystal polymer grafted onto the surface of the amino-zeolite carrier creates a steric hindrance effect, preventing premature adsorption and failure of the water-reducing agent molecules. This characteristic contributes to the significantly higher slump loss (17%) of Comparative Example 4 (50% grafting ratio) than the 7.6% of the Example group, revealing the crucial role of the grafting ratio threshold in functional stability.

[0107] Gradient carboxyl distribution on the surface of carboxylated hybrid fibers and Ca in cement hydration products 2+ The formation of high-strength chelate bonds, experimental data show that the 24h crack area of ​​Example 3 (63mm 2 / m 2 )Compared with Comparative Example 5 (142mm 2 / m 2 ) decreased by 55.6%, this difference was due to the carboxyl-Ca 2+Interfacial bonds (bond energy > 50 kJ / mol) effectively inhibit microcrack propagation. Silicon carbide whiskers on the fiber surface are embedded at sharp angles between graphene layers, creating a multi-level energy dissipation mechanism at the crack tip. This significantly increases the fracture energy of the Example group compared to Comparative Example 5, which relies solely on physical anchoring.

[0108] The Mg / P molar ratio of the magnesium phosphate / zeolite slow-release carrier has a significant effect on the crystal expansion characteristics. When the ratio is adjusted to 1.0:1 (Comparative Example 8), the 24h crack area (158mm 2 / m 2 ) increased by 150% compared to Example 3, demonstrating that a Mg / P ratio of 1.2-1.5 is necessary to trigger the directional expansion of the magnesium phosphate lattice (ΔV = 8-12%). The mechanical stress generated by the expansion opens the zeolite pore gates, enabling non-Fickian diffusion of sodium gluconate. This temperature-controlled release mechanism allows the Example group to maintain a crack area of ​​less than 85 mm under forced ventilation conditions. 2 / m 2 , while the traditional sustained-release system (Comparative Example 8) suffers from deterioration of anti-cracking performance due to the mismatch of release timing.

[0109] Test Example 3: Objective: To verify the effects of low-temperature pre-hydrated micelle construction and shear-activated gradient water addition process on hydration heat and rheological properties.

[0110] The experimental steps are as follows: 1. Sample Preparation Example group: Examples 1-3 were prepared according to a gradient synergistic mixing process (low temperature premixing + shear activation gradient water addition).

[0111] Comparative Example Group: Comparative Example 6 (canceling the low-temperature premixing and mixing all the raw materials at 25° C. at one time).

[0112] 2. The hydration heat test is as follows: 1) Sample processing: The cement paste part of the fresh concrete was taken, the aggregate was removed, and the samples were placed in a sealed aluminum box (50 mm in diameter and 30 mm in height). Two parallel samples were prepared for each group.

[0113] 2) Constant temperature measurement: The sample was placed in a constant temperature bath (20±0.1℃), connected to a calorimeter probe, and the temperature change was continuously monitored for 24 hours.

[0114] 3) Calorie calculation: The integral value of the temperature-time curve was recorded and combined with the cement mass (accurate to 0.01 g) to calculate the cumulative hydration heat (kJ / kg) of unit mass of cement.

[0115] 3. Rheological properties test is as follows: 1) Instrument preparation: The rotational rheometer was pre-calibrated using a coaxial cylindrical fixture (40 mm inner diameter, 60 mm outer diameter, and 2 mm gap).

[0116] 2) Sample loading: Pour fresh concrete paste (minus aggregate) into the fixture and let it stand for 2 minutes to eliminate thixotropy.

[0117] 3) Shear Scan: From 0.1s -1 Gradually increase the shear rate to 100s -1 , record the shear stress response curve.

[0118] Parameter fitting: The Herschel-Bulkley model (τ=τ0+K·γ n ) fit the data and extract the yield stress τ0 (Pa) and rheological index n.

[0119] The test results are shown in Table 3: Table 3 Mixing process optimization test data sample 24h hydration heat (kJ / kg) <![CDATA[Rheological yield stress τ0 (Pa)]]> Rheological index n Example 1 182±6 48.3±1.2 0.79±0.03 Example 2 175±5 43.7±0.9 0.81±0.02 Example 3 168±7 39.2±1.5 0.76±0.04 Comparative Example 6 235±8 72.5±2.3 0.93±0.05 From the test results in Table 3, we can get: The low-temperature prehydration stage (3-8°C) promotes the pre-assembly of the silanol groups on the surface of the nano-silica sol with the cement particles through hydrogen bonds to form core-shell structure micelles. The experimental data show that the 24h hydration heat of the example group (168-182kJ / kg) is 22.6-28.5% lower than that of the comparative example 6 (235kJ / kg), indicating that the physical wrapping of the cement particles by the micelle shell significantly delays the early hydration of the C3A mineral. This delaying effect is due to the metakaolin flake particles (specific surface area> 20m2) adsorbed on the micelle surface. 2 / g) blocks the diffusion path of water molecules, changing the hydration reaction from explosive to gradual, which is consistent with the more gentle yield stress growth curve (τ0 = 39.2-48.3 Pa) of the embodiment group in the rheological test.

[0120] Shear activation (120-150s -1 ) and the gradient addition of water (water-binder ratio 0.18→0.30) promote the nematic phase transition of the liquid crystal microspheres in the shear field, dynamically releasing the water-reducing component. The rheological index n value of the embodiment group (0.76-0.81) in the experimental data is significantly lower than that of the comparative example 6 (0.93), proving that this process makes the slurry transition from shear thinning (n<1) to near-Newtonian fluid properties, which is consistent with the shear rate change during pumping (10-100s -1) forms an adaptation. The staged regulation of the water film thickness during the gradient water addition process avoids particle agglomeration caused by traditional one-time water addition (the yield stress of Comparative Example 6 is as high as 72.5 Pa). The τ0 value (39.2 Pa) of Example 3 is 45.9% lower than that of Comparative Example 6, verifying the dispersion optimization mechanism.

[0121] The synergistic effect of low-temperature prehydration and shear gradient water addition achieves dual regulation of hydration dynamics and rheological properties. The low hydration heat (<182kJ / kg) and low rheological index (n<0.82) data of the embodiment group show that the micelle sustained release effect and shear-induced dispersion complement each other: the former inhibits the deterioration of rheological properties caused by temperature rise, and the latter reduces flow resistance through particle surface wettability modification. This process synergy enables the concrete to maintain a slump loss of less than 10% under pumping shear (30L / min flow rate in the simulation test), while the comparative example 6 caused temperature rise and rheological loss due to process mismatch (hydration heat +28.5%, τ0+45.9%), which confirms the necessity of gradient process design.

[0122] Test Example 4: Objective: To verify the influence of thermal buffering effect of phase change microcapsules and Zeta potential regulation on friction temperature rise and strength stability.

[0123] The experimental steps are as follows: 1. Sample Preparation Example group: Examples 1-3 (including phase change microcapsules and Zeta potential control process).

[0124] Comparative group: Comparative Example 7: The phase change microcapsules were removed and replaced with an equal amount of quartz sand powder.

[0125] Comparative Example 9: Cancel the Zeta potential control and directly perform standard maintenance.

[0126] 2. The pipe wall friction temperature rise test is as follows: 1) Pump pipe installation: Load the prepared concrete into the pumping equipment and connect a metal pump pipe with a diameter of 125mm and a length of 20m. The outer wall of the pump pipe must be clean and dry.

[0127] 2) Parameter setting: Set the pumping speed to 40L / min, run continuously for 30 minutes, and control the ambient temperature at 25±1℃.

[0128] 3) Temperature monitoring: Three infrared temperature measuring points (inlet, middle, and outlet) are arranged at equal intervals on the outer wall of the pump tube.

[0129] After starting the pump, use an infrared thermal imager to record the temperature of each measuring point every 5 seconds until the end of the test.

[0130] 4) Data calculation: Take the difference (ΔT) between the maximum temperature of each measuring point and the initial temperature within 30 minutes, and use the range of ΔT of the three measuring points as the final result.

[0131] 3. The compressive strength fluctuation rate test is as follows: 1) Specimen curing: The hardened concrete specimens (standard size: 150 mm cube) were placed in a constant temperature box and cured according to the following cycle: 20°C constant temperature for 12 hours → heating to 60°C constant temperature for 12 hours → cycle for 7 days.

[0132] 2) Compression test: Immediately after the curing period, 10 specimens were randomly selected from each group of samples.

[0133] A universal testing machine was used to load the specimen at a rate of 0.5 MPa / s until the specimen failed, and the peak pressure was recorded.

[0134] 3) Volatility calculation: The ratio of the standard deviation of the compressive strength of the 10 specimens to the mean value was calculated (coefficient of variation = standard deviation / mean × 100%).

[0135] The test results are shown in Table 4: Table 4 Temperature control performance test data sample Friction temperature rise ΔT(℃) Strength variation coefficient (%) Example 1 9.3±0.8 4.2±0.5 Example 2 8.7±1.1 3.8±0.4 Example 3 7.5±0.6 2.9±0.3 Comparative Example 7 26.4±2.3 18.7±1.6 Comparative Example 9 14.2±1.7 9.5±0.9 From the test results in Table 4, we can get: The paraffin core material in the phase-change microcapsules undergoes a solid-liquid phase transition between 20°C and 45°C (phase change enthalpy >180 J / g). This latent heat absorbs the transient temperature rise generated by pumping friction. Experimental data show that the friction temperature rise ΔT (7.5-9.3°C) in the Example group is 62-71.6% lower than that in Comparative Example 7 (26.4°C), confirming the microcapsules' rapid buffering of frictional heat. The high thermal conductivity of the graphene shell (>3000 W / m·K) promotes rapid heat diffusion between the microcapsules, preventing localized overheating. The standard deviation of the temperature rise in Example 3 is only ±0.6°C (compared to ±2.3°C in Comparative Example 7), demonstrating the microcapsule system's thermal homogenization capability.

[0136] Zeta potential manipulation adjusts the surface charge of the microcapsules (-35mV to -40mV), resulting in an electrostatically stable dispersion within the cement paste. The experimental data revealed a significantly lower coefficient of variation in strength (2.9-4.2%) for the Example group than for Comparative Example 9 (9.5%), demonstrating that potential manipulation can suppress stress concentration caused by microcapsule agglomeration. The uniform distribution of microcapsules ensures a full coverage of the phase change endothermic effect. In Comparative Example 9, due to uncontrolled potential, microcapsule concentration in localized areas (standard deviation ±1.7°C) degraded both temperature rise and strength fluctuations, demonstrating the correlation between distribution homogeneity and thermal-mechanical performance.

[0137] The synergistic effect of phase change heat absorption and potential regulation achieves dual regulation of heat source dispersion and energy dissipation. The low friction temperature rise (ΔT < 10°C) and low strength variation coefficient (< 5%) of the embodiment group indicate that the microcapsule system not only delays the temperature peak, but also reduces the temperature gradient stress through uniform heat distribution, so that the concrete can still maintain matrix density when cured at 60°C (such as the variation coefficient of 2.9% in Example 3). In contrast, due to the lack of phase change material in Comparative Example 7, temperature stress directly triggers microcrack expansion (variation coefficient of 18.7%), revealing the causal chain between thermal buffering and structural stability.

[0138] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A special concrete for super high-rise pumping, characterized in that: The following components are included by weight: 350-400 parts of Portland cement; 700-750 parts of graded basalt aggregate; 45-55 parts of ultrafine metakaolin; 20-30 parts of modified nano-silica sol; 12-18 parts of phase change energy storage microcapsules; 8.0-9.0 parts of ternary coupling composite admixture, including: 3.0-3.5 parts of aminated zeolite grafted liquid crystal polymer microspheres; 2.5-3.0 parts of magnesium phosphate / zeolite sustained-release carrier; 2.3 to 2.7 parts of carboxylated hybrid fiber.

2. The special concrete for super high-rise pumping according to claim 1, characterized in that: The grafting rate of the amino zeolite grafted liquid crystal polymer microspheres is 70-75%, and the particle size is 70-130 nm, wherein the liquid crystal polymer is a 4-vinyl triphenylene derivative, and the zeolite is an NH2-ZSM5 molecular sieve.

3. The special concrete for super high-rise pumping according to claim 1, characterized in that: The Mg / P molar ratio of the magnesium phosphate / zeolite sustained-release carrier is 1.2-1.5:

1.

4. The special concrete for super high-rise pumping according to claim 1, characterized in that: The carboxylated hybrid fiber is a graphene / silicon carbide composite fiber with a diameter of 0.5 to 1.2 μm, an aspect ratio of 200 to 300, and a surface carboxyl density of 7.5 to 8.5 μmol / g.

5. The special concrete for super high-rise pumping according to claim 1, characterized in that: The phase-change energy storage microcapsule is an octadecane / SiO2 core-shell structure, with a particle size of 80 to 120 μm and a shell thickness of 10 to 15 μm.

6. A method for preparing special concrete for super high-rise pumping according to any one of claims 1 to 5, characterized in that: The following steps are involved: (a) Aggregate interface optimization: The basalt aggregate was subjected to liquid nitrogen low-temperature embrittlement and ball milling treatment; (b) Preparation of ternary coupling admixture: synthesis of amino-zeolite-grafted liquid crystal polymer microspheres and carboxylation of hybrid fibers; (c) Gradient synergistic mixing: low-temperature premixing and activation are performed in stages; (d) Dynamic rheological control: adding phase change microcapsules and allowing to stand for curing.

7. The preparation method according to claim 6, characterized in that The step (a) comprises: The basalt aggregate was placed in a liquid nitrogen environment for low-temperature embrittlement treatment at a controlled temperature of -190 to -200°C for 36 to 60 hours, during which 3 to 5 thermal shock cycles were performed, each cycle consisting of 30 minutes of freezing and 10 minutes of warming to 25°C. The embrittled aggregate was transferred to a planetary ball mill and subjected to ball milling at a speed of 550 to 650 r / min for 1.5 to 2.5 hours using zirconia grinding balls with a diameter of 3 to 6 mm to obtain spherical aggregate with a sphericity greater than 0.

92.

8. The preparation method according to claim 6, characterized in that The step (b) comprises: Preparation of Aminated Zeolite Grafted Liquid Crystalline Polymer Microspheres: Dispersing 4-vinyl triphenylene derivative liquid crystal microspheres and NH2-ZSM5 zeolite in a DMF solvent at a molar ratio of 1:1.0-1.5 and a solid-liquid ratio of 1:8-1.12; Reflux reaction at 110-130°C for 5-7 hours, maintaining nitrogen pressure at 0.2-0.4 MPa; After centrifugation and vacuum drying, composite microspheres with a grafting rate of 70-75% were obtained; Carboxylated hybrid fiber treatment: Immerse the graphene / silicon carbide fiber in a concentrated sulfuric acid / nitric acid mixture with a volume ratio of 2.5 to 3.5:1; Treat at 400-600W ultrasonic power for 25-35 minutes; After washing with deionized water to a pH of 6.5-7.5, vacuum drying is performed at 60-80°C for 8-12 hours.

9. The preparation method according to claim 6, characterized in that The step (c) comprises: First-stage low-temperature mixing: At 3-8°C, put Portland cement, ultrafine metakaolin and 60-75% of the total water into the mixer; Premix at a speed of 100-140 r / min for 1-2 minutes and then add the modified nano-silica sol; Continue stirring for 4 to 6 minutes to form prehydrated micelles; Secondary activation mixing: After heating to 40-50°C, add the ternary coupling composite admixture; At 160-200 r / min speed and 120-150s -1 Stir at a shear rate of 7 to 9 minutes; Simultaneously inject the remaining 25-35% of water to maintain a water-binder ratio of 0.26-0.

30.

10. The preparation method according to claim 6, characterized in that The step (d) comprises: Phase change microcapsules incorporation: Pre-disperse octadecane / SiO2 microcapsules and mixing water in a mass ratio of 1:3-5; Stir at a low speed of 50-70 r / min for 2-4 minutes to achieve uniform distribution; Static maintenance and control: Cure for 25 to 35 minutes at an ambient temperature of 20 to 25°C and a humidity of 60 to 75%.

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