Lightweight low-shrinkage ultra-high performance concrete, preparation method and application thereof

Abstract

The application relates to the technical field of concrete, and particularly discloses light low-shrinkage ultra-high performance concrete as well as a preparation method and application thereof. The light low-shrinkage ultra-high performance concrete comprises the following components in parts by weight: cement 80-110 parts, silica ash 20-30 parts, fly ash 30-45 parts, hollow glass microbeads 28-45 parts, porous ceramic sand 80-95 parts, expanding agent 5-10 parts, water 30-50 parts, water reducing agent 2-10 parts and steel fiber 20-40 parts. The porous ceramic sand is selected to completely replace quartz sand as aggregate, and the hollow glass microbeads are used to partially replace cement, so that the apparent density of UHPC is reduced. The pores in the porous ceramic sand can absorb and store water, the stored water is gradually released in the UHPC matrix, the capillary negative pressure is reduced, and the expansion agent reaction generates expansion products, which has a synergistic effect with the expansion agent, so that the shrinkage of UHPC is effectively inhibited.

Description

Technical Field

[0001] This invention relates to the field of concrete technology, and in particular to a lightweight, low-shrinkage, ultra-high performance concrete, its preparation method, and its application. Background Technology

[0002] Ultra-high performance concrete (UHPC) is a cement-based composite material prepared with an extremely low water-cement ratio (0.16~0.22) and a high content of cementitious materials, exhibiting ultra-high strength and durability. It plays a crucial role in construction fields such as long-span bridges and underground engineering. Traditional UHPC has an apparent density as high as 2.6-2.8 g / cm³. 3 This significantly increases the axial compression load on the bottom load-bearing columns and foundation, causing the ultra-high strength of UHPC to be largely used to resist its own weight, with only a portion used to bear external loads, making it difficult to fully utilize the structural efficiency of UHPC. Furthermore, due to the high amount of cementitious materials and extremely low water-cement ratio used in UHPC, the hydration reaction consumes a large amount of water within the capillaries, leading to capillary dehydration and negative pressure. With tightly packed particles, the size of the matrix capillaries is even smaller, resulting in even greater capillary negative pressure, causing UHPC to shrink by a much greater amount than ordinary concrete. Excessive shrinkage of UHPC can easily lead to early cracking of the structure, reducing its mechanical properties and durability, and in severe cases, even causing safety accidents.

[0003] Currently, the main approach to addressing the issues of excessive weight and shrinkage in UHPC is to use lightweight aggregates such as sintered shale and sintered coal gangue as aggregates, along with the addition of solid expanding agents or internal curing agents. However, these methods all suffer from insurmountable technical drawbacks. Compared to the dense, solid structure of conventional aggregate quartz sand, lightweight aggregates contain numerous closed or interconnected pores, resulting in significantly lower strength compared to quartz sand. Therefore, while lightweight aggregates can effectively reduce the apparent density of UHPC when used as aggregates instead of quartz sand, they also significantly reduce its mechanical properties. Furthermore, due to the extremely low water-cement ratio of UHPC, the added solid expanding agents are difficult to react completely, resulting in fewer expansion products and limiting their expansion effect, leading to poor shrinkage compensation. Internal curing agents, typically represented by highly absorbent resins, reduce shrinkage by replenishing moisture in the capillaries and decreasing capillary pressure. However, after releasing its internal moisture, it will form pores of hundreds of micrometers in size in the matrix, resulting in a weak area in the microstructure between it and the matrix interface, which greatly reduces the strength of the matrix. Summary of the Invention

[0004] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. Therefore, an object of the present invention is to provide a lightweight, low-shrinkage, ultra-high performance concrete. A second object of the present invention is to provide a method for preparing such lightweight, low-shrinkage, ultra-high performance concrete. A third object of the present invention is to provide applications of such lightweight, low-shrinkage, ultra-high performance concrete.

[0005] The inventive concept of this invention is to completely replace quartz sand with porous ceramic sand as aggregate, and to partially replace cement with hollow glass microspheres, thereby reducing the apparent density of UHPC. The pores inside the porous ceramic sand can absorb and store moisture, which is gradually released within the UHPC matrix, reducing capillary negative pressure and supplying an expansion agent to react and generate expansion products, thereby effectively inhibiting UHPC shrinkage.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a lightweight, low-shrinkage, ultra-high-performance concrete, wherein the lightweight, low-shrinkage, ultra-high-performance concrete comprises, by weight, the following components: 80-110 parts cement, 20-30 parts silica fume, 30-45 parts fly ash, 28-45 parts hollow glass microspheres, 80-95 parts porous ceramic sand, 5-10 parts expansion agent, 30-50 parts water, 2-10 parts water-reducing agent, and 20-40 parts steel fiber.

[0007] The density of porous ceramic sand is 1.73 g / cm³. 3 It is significantly lower than the density of quartz sand (2.6~2.7 g / cm³). 3 This invention uses porous ceramic sand as aggregate introduced into the interior of UHPC, and partially replaces cement with hollow glass microspheres, effectively reducing the apparent density of UHPC. Simultaneously, the pores within the porous ceramic sand can absorb and hold moisture, preventing early moisture loss. As the hydration reaction proceeds, the moisture inside the UHPC matrix is ​​gradually consumed. Driven by the relative humidity difference generated by cement hydration, the moisture inside the pores of the ceramic sand is gradually released, directionally replenishing capillary moisture, reducing capillary negative pressure, and lowering the shrinkage driving force. Therefore, the porous ceramic sand in this invention functions as both aggregate and internal curing agent. While cement hydration generates hydration products, UHPC also continuously shrinks. At this time, the gradually released moisture from the porous ceramic sand provides conditions for the reaction of the expansion agent, generating expansion products simultaneously with cement hydration. This achieves synergy between UHPC shrinkage and expansion agent volume expansion, effectively improving expansion efficiency and reducing UHPC shrinkage.

[0008] Compared to traditional internal curing agents, porous ceramic sand, after releasing moisture, remains as aggregate within UHPC, avoiding the formation of hundreds of micrometers of pores and weak areas in the microstructure. Compared to quartz sand and other conventional lightweight aggregates (such as sintered shale and sintered coal gangue), the pores within porous ceramic sand can be filled by cement hydration products, resulting in a tighter bond between the ceramic sand and the matrix. This reduces the formation of weak micro-interface transition zones, creating a denser microstructure and effectively reducing the apparent density of UHPC while maintaining good mechanical properties. Meanwhile, the expansion agent generates expansion products, producing expansion stress. This expansion stress within the UHPC matrix compresses the steel fibers, increasing friction between the fibers and the UHPC matrix, leading to a tighter bond. Under load, the fibers can better transmit and distribute stress, reducing stress concentration and improving the toughness of the UHPC matrix.

[0009] Hollow glass microspheres are a low-density material with pozzolanic activity. This invention uses hollow glass microspheres to replace part of the cement, which can further effectively reduce the apparent density of UHPC. Furthermore, hollow glass microspheres can undergo a secondary hydration reaction with calcium hydroxide generated from the cement hydration reaction, forming CSH gel and optimizing the microstructure of UHPC. Moreover, the hollow spherical shape of the hollow glass microspheres forms an arched interface transition zone, which can uniformly distribute stress and hinder crack formation and propagation. It can offset the difference in elastic modulus between the lightweight aggregate (aggregate) and the UHPC matrix, thereby avoiding microcracks caused by inconsistent deformation between the lightweight aggregate and the matrix under applied loads, and improving the strength and crack resistance of UHPC.

[0010] Therefore, in this invention, hollow glass microspheres, porous ceramic sand, expansion agent and steel fiber work synergistically to effectively reduce the apparent density of UHPC, while improving the compressive strength of UHPC and reducing the drying shrinkage rate of UHPC.

[0011] Preferably, the lightweight, low-shrinkage, ultra-high performance concrete is composed of the following components by weight: 80-110 parts cement, 20-30 parts silica fume, 30-45 parts fly ash, 28-45 parts hollow glass microspheres, 80-95 parts porous ceramic sand, 5-10 parts expansion agent, 30-50 parts water, 2-10 parts water-reducing agent, and 20-40 parts steel fiber.

[0012] Preferably, the cement has a weight of 85-108 parts; more preferably, the cement has a weight of 88-105 parts; even more preferably, the cement has a weight of 90-102 parts; and even more preferably, the cement has a weight of 93-100 parts.

[0013] Preferably, the silica fume is in the form of 22-28 parts by weight; more preferably, the silica fume is in the form of 24-27 parts by weight; even more preferably, the silica fume is in the form of 25-26.8 parts by weight; and even more preferably, the silica fume is in the form of 26-26.5 parts by weight.

[0014] Preferably, the fly ash comprises 30-42 parts by weight; more preferably, the fly ash comprises 31-40 parts by weight; even more preferably, the fly ash comprises 32-38 parts by weight; and even more preferably, the fly ash comprises 33-35 parts by weight.

[0015] Preferably, the hollow glass microspheres are in the form of 29 to 44 parts by weight; more preferably, the hollow glass microspheres are in the form of 30 to 42 parts by weight; even more preferably, the hollow glass microspheres are in the form of 31 to 41 parts by weight; and even more preferably, the hollow glass microspheres are in the form of 32 to 40 parts by weight.

[0016] Preferably, the porous ceramic sand has a weight ratio of 82-93 parts; more preferably, the porous ceramic sand has a weight ratio of 84-90 parts; even more preferably, the porous ceramic sand has a weight ratio of 85-89 parts; and even more preferably, the porous ceramic sand has a weight ratio of 86-88 parts.

[0017] Preferably, the expansion agent is present in an amount of 5.5 to 9.5 parts by weight; more preferably, the expansion agent is present in an amount of 6 to 9 parts by weight; even more preferably, the expansion agent is present in an amount of 6.5 to 8.5 parts by weight; and even more preferably, the expansion agent is present in an amount of 7 to 8 parts by weight.

[0018] Preferably, the water comprises 32 to 48 parts by weight; more preferably, the water comprises 35 to 47 parts by weight; even more preferably, the water comprises 38 to 46 parts by weight; and even more preferably, the water comprises 40 to 45 parts by weight.

[0019] Preferably, the water-reducing agent is present in an amount of 2.5 to 8 parts by weight; more preferably, the water-reducing agent is present in an amount of 2.8 to 7 parts by weight; even more preferably, the water-reducing agent is present in an amount of 3 to 6 parts by weight; and even more preferably, the water-reducing agent is present in an amount of 4 to 5 parts by weight.

[0020] Preferably, the steel fiber has a weight ratio of 22 to 39 parts; more preferably, the steel fiber has a weight ratio of 23 to 38 parts; even more preferably, the steel fiber has a weight ratio of 24 to 37 parts; and even more preferably, the steel fiber has a weight ratio of 25 to 35 parts.

[0021] Preferably, the water-cement ratio of the lightweight, low-shrinkage, ultra-high performance concrete is 0.16 to 0.25; more preferably, the water-cement ratio of the lightweight, low-shrinkage, ultra-high performance concrete is 0.17 to 0.23; and even more preferably, the water-cement ratio of the lightweight, low-shrinkage, ultra-high performance concrete is 0.18 to 0.22.

[0022] Preferably, the specific surface area of ​​the cement is 330~350 m². 2 / kg; more preferably, the specific surface area of ​​the cement is 335~345 m². 2 / kg; and more preferably, the specific surface area of ​​the cement is 337~342 m². 2 / kg.

[0023] Preferably, the density of the cement is 2.5~4 g / cm³. 3 More preferably, the density of the cement is 2.7~3.8 g / cm³. 3 More preferably, the density of the cement is 2.9~3.3 g / cm³. 3 .

[0024] Preferably, the average particle size of the cement is 18~25μm; more preferably, the average particle size of the cement is 19~23μm; and even more preferably, the average particle size of the cement is 20~22μm.

[0025] Preferably, the specific surface area of ​​the fly ash is 680~720 m². 2 / kg; more preferably, the specific surface area of ​​the fly ash is 690~710m². 2 / kg; and more preferably, the specific surface area of ​​the fly ash is 695~705m². 2 / kg.

[0026] Preferably, the density of the fly ash is 2~4 g / cm³. 3 More preferably, the density of the fly ash is 2.1~3.5 g / cm³. 3 More preferably, the density of the fly ash is 2.2~3.0 g / cm³. 3 .

[0027] Preferably, the average particle size of the fly ash is 22-30 μm; more preferably, the average particle size of the fly ash is 23-28 μm; and even more preferably, the average particle size of the fly ash is 25-27 μm.

[0028] Preferably, the specific surface area of ​​the silica fume is 500~550 m². 2 / kg; more preferably, the specific surface area of ​​the silica fume is 510~540m². 2 / kg; and more preferably, the specific surface area of ​​the silica fume is 520~530m². 2 / kg.

[0029] Preferably, the density of the silica fume is 2~4 g / cm³. 3 More preferably, the density of the silica fume is 2.2~3.3 g / cm³. 3 More preferably, the density of the silica fume is 2.3~2.6 g / cm³. 3 .

[0030] Preferably, the average particle size of the silica fume is 10~20μm; more preferably, the average particle size of the silica fume is 12~18μm; and even more preferably, the average particle size of the silica fume is 14~16μm.

[0031] Preferably, the specific surface area of ​​the hollow glass microspheres is 350~420 m². 2 / kg; more preferably, the specific surface area of ​​the hollow glass microspheres is 360~410m². 2 / kg; and more preferably, the specific surface area of ​​the hollow glass microspheres is 370~400 m² / kg. 2 / kg.

[0032] Preferably, the density of the hollow glass microspheres is 0.3~1 g / cm³. 3 More preferably, the density of the hollow glass microspheres is 0.4~0.8 g / cm³. 3 More preferably, the density of the hollow glass microspheres is 0.5~0.7 g / cm³. 3 .

[0033] Preferably, the average particle size of the hollow glass microspheres is 15~25μm; more preferably, the average particle size of the hollow glass microspheres is 17~23μm; and even more preferably, the average particle size of the hollow glass microspheres is 18~22μm.

[0034] Preferably, the average particle size of the porous ceramic sand is 180~220μm; more preferably, the average particle size of the porous ceramic sand is 190~210μm; and even more preferably, the average particle size of the porous ceramic sand is 195~203μm.

[0035] Preferably, the porosity of the porous ceramic sand is 30% to 40%; more preferably, the porosity of the porous ceramic sand is 32% to 38%; and even more preferably, the porosity of the porous ceramic sand is 34% to 37%.

[0036] Preferably, the porous ceramic sand is water-treated porous ceramic sand; more preferably, the water treatment method is to immerse the porous ceramic sand in water for 20-30 hours; even more preferably, the water treatment method is to immerse the porous ceramic sand in water for 22-26 hours.

[0037] Preferably, the expanding agent includes at least one of calcium sulfoaluminate expanding agents, calcium sulfoaluminate-calcium oxide expanding agents, and magnesium oxide expanding agents; more preferably, the expanding agent includes at least one of expanding agent HCSA and expanding agent MgO; even more preferably, the expanding agent is expanding agent HCSA and expanding agent MgO.

[0038] Preferably, the water-reducing agent includes a polycarboxylate superplasticizer. Compared with lignin sulfonate superplasticizers, naphthalene-based superplasticizers, and other water-reducing agents, polycarboxylate superplasticizers have a higher water-reducing effect.

[0039] Preferably, the steel fiber includes copper-plated steel fiber. Compared with pure copper fiber, copper-plated steel fiber can form a stronger and more stable chemical bond with the concrete matrix, significantly improving the bonding performance between the two, thereby allowing the fiber to transfer stress to the matrix more efficiently and achieving synergistic reinforcement.

[0040] Preferably, the steel fibers are straight.

[0041] Preferably, the length of the steel fiber is 10-18 mm; more preferably, the length of the steel fiber is 12-16 mm; and even more preferably, the length of the steel fiber is 13-15 mm.

[0042] Preferably, the diameter of the steel fiber is 0.1~0.4mm; more preferably, the diameter of the steel fiber is 0.15~0.35mm; and even more preferably, the diameter of the steel fiber is 0.2~0.3mm.

[0043] Preferably, the tensile strength of the steel fiber is ≥2800MPa; more preferably, the tensile strength of the steel fiber is ≥2850MPa; even more preferably, the tensile strength of the steel fiber is ≥2900MPa; and even more preferably, the tensile strength of the steel fiber is 2900MPa~3000MPa.

[0044] Preferably, the density of the steel fiber is 7500~8000 kg / m³. 3 More preferably, the density of the steel fiber is 7600~7900 kg / m³. 3 More preferably, the density of the steel fiber is 7700~7850 kg / m³. 3 .

[0045] Preferably, the apparent density of the lightweight, low-shrinkage, ultra-high-performance concrete is ≤1870 kg / m³. 3 More preferably, the apparent density of the lightweight, low-shrinkage, ultra-high-performance concrete is ≤1860 kg / m³. 3 Furthermore, preferably, the apparent density of the lightweight, low-shrinkage, ultra-high-performance concrete is 1850 kg / m³. 3 More preferably, the apparent density of the lightweight, low-shrinkage, ultra-high-performance concrete is 1765~1845 kg / m³. 3 .

[0046] Preferably, the compressive strength of the lightweight, low-shrinkage, ultra-high performance concrete is ≥100MPa; more preferably, the compressive strength of the lightweight, low-shrinkage, ultra-high performance concrete is ≥102MPa; even more preferably, the compressive strength of the lightweight, low-shrinkage, ultra-high performance concrete is ≥105MPa; and even more preferably, the compressive strength of the lightweight, low-shrinkage, ultra-high performance concrete is 105~126MPa.

[0047] Preferably, the flexural strength of the lightweight, low-shrinkage ultra-high performance concrete is ≥19MPa; more preferably, the flexural strength of the lightweight, low-shrinkage ultra-high performance concrete is ≥19.3MPa; even more preferably, the flexural strength of the lightweight, low-shrinkage ultra-high performance concrete is ≥19.5MPa; and even more preferably, the flexural strength of the lightweight, low-shrinkage ultra-high performance concrete is 19.5~26.5MPa.

[0048] Preferably, the drying shrinkage rate of the lightweight, low-shrinkage, ultra-high-performance concrete is ≤150%. 10 -6 More preferably, the drying shrinkage rate of the lightweight, low-shrinkage, ultra-high-performance concrete is ≤148%. 10 -6 Furthermore, preferably, the drying shrinkage rate of the lightweight, low-shrinkage, ultra-high-performance concrete is ≤145%. 10 -6 More preferably, the drying shrinkage rate of the lightweight, low-shrinkage, ultra-high-performance concrete is 110%. 10 -6 ~145 10 -6 .

[0049] In a second aspect, the present invention provides a method for preparing the lightweight, low-shrinkage, ultra-high-performance concrete described in the first aspect, comprising the following steps: S1: Mix and stir the components except for porous ceramic sand and steel fiber to obtain the first slurry; S2: Add porous ceramic sand to the first slurry described in step S1 and mix to obtain a second slurry; S3: Add steel fibers to the second slurry described in step S2 and mix to obtain a third slurry; S4: The third slurry is poured and cured to the set age to obtain the lightweight, low-shrinkage, ultra-high performance concrete.

[0050] Preferably, in step S1, cement, silica fume, fly ash, hollow glass microspheres and expansion agent are first dry-mixed and stirred, and then a mixed solution of water-reducing agent and water is added and stirred to obtain the first slurry.

[0051] Preferably, the stirring time in step S2 is 5-10 min; more preferably, the stirring time in step S2 is 6-9 min.

[0052] Preferably, the stirring time in step S3 is 8-12 minutes; more preferably, the stirring time in step S3 is 9-11 minutes.

[0053] Preferably, the curing time in step S4 is >24 days; more preferably, the curing time in step S4 is >26 days; even more preferably, the curing time in step S4 is >26 days; and even more preferably, the curing time in step S4 is 28~30 days.

[0054] Preferably, the curing temperature in step S4 is 20±2℃ and the humidity is ≥95%.

[0055] Thirdly, the present invention provides the application of the lightweight, low-shrinkage, ultra-high performance concrete described in the first aspect in the technical fields of bridges, building exterior walls, roads, or pipelines.

[0056] The beneficial effects of this invention are: (1) In this invention, porous ceramic sand is selected as aggregate and introduced into the interior of UHPC, and hollow glass microspheres are used to replace cement, which effectively reduces the apparent density of UHPC. At the same time, the pores inside the porous ceramic sand can absorb and load water, which can avoid early water consumption. As the hydration reaction proceeds, the water inside the UHPC matrix is ​​gradually consumed. Driven by the relative humidity difference generated by cement hydration, the water inside the pores of the ceramic sand is gradually released, which directionally replenishes the water in the capillary pores, reduces the negative pressure in the capillary pores, and reduces the shrinkage driving force. Therefore, the porous ceramic sand in this invention has the functions of both aggregate and internal curing agent. While cement hydration generates hydration products, UHPC is also continuously shrinking. At this time, the water gradually released by the porous ceramic sand can provide conditions for the reaction of the expansion agent, generating expansion products at the same time as cement hydration, realizing the synergy between UHPC shrinkage and expansion agent volume expansion, effectively improving expansion efficiency and reducing UHPC shrinkage.

[0057] (2) Compared to traditional internal curing agents, the porous ceramic sand of this invention remains in the form of aggregate inside the UHPC after releasing moisture, and does not form pores of hundreds of micrometers or create weak areas in the microstructure. Compared to quartz sand and other conventional lightweight aggregates (such as sintered shale and sintered coal gangue), the pores inside the porous ceramic sand can be filled by the hydration products of cement, resulting in a tighter bond between the ceramic sand and the matrix, reducing the formation of weak micro-interface transition zones, and forming a tighter microstructure. This effectively reduces the apparent density of the UHPC while maintaining good mechanical properties. Meanwhile, the expansion agent generates expansion products, which produce expansion stress. This expansion stress inside the UHPC matrix compresses the steel fibers, increasing the friction between the fibers and the UHPC matrix, resulting in a tighter bond between the fibers and the matrix. When subjected to load, the fibers can better transmit and disperse stress, reducing stress concentration and improving the toughness of the UHPC matrix.

[0058] (3) This invention uses hollow glass microspheres to replace part of the cement, which can further effectively reduce the apparent density of UHPC. In addition, hollow glass microspheres can undergo a secondary hydration reaction with calcium hydroxide generated by the cement hydration reaction to generate CSH gel, which optimizes the microstructure of UHPC. Moreover, the hollow glass microspheres are hollow spherical in shape, which will form an arched interface transition zone, which can uniformly disperse stress and hinder the formation and propagation of cracks. It can offset the difference in elastic modulus between the lightweight aggregate (aggregate) and the UHPC matrix in UHPC, thereby avoiding microcracks caused by the inconsistent deformation of the lightweight aggregate and the matrix under external load, and improving the strength and crack resistance of UHPC. Therefore, in this invention, hollow glass microspheres, porous ceramic sand, expansion agent and steel fiber work together to effectively reduce the apparent density of UHPC, while improving the compressive strength of UHPC and reducing the drying shrinkage rate of UHPC.

[0059] (4) The lightweight, low-shrinkage, ultra-high performance concrete of the present invention has excellent mechanical properties, with an apparent density ≤1870 kg / m³. 3 Compressive strength ≥100MPa, flexural strength ≥19MPa, and especially drying shrinkage ≤150%. 10 -6 It is significantly superior to ultra-high performance concrete prepared from lightweight aggregates such as closed-cell shale ceramsite, pumice, or expanded perlite, and can be well applied in technical fields such as bridges, building exterior walls, roads, or pipelines. Detailed Implementation

[0060] To enable those skilled in the art to more clearly understand this application, the present invention will be further described in detail below with reference to embodiments. However, it should be understood that the following embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention should be determined by the scope defined in the claims. In the description of the present invention, it should be noted that unless specific conditions are specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments used that do not specify the manufacturer are all commercially available conventional products.

[0061] The specific surface area of ​​the cement used in this embodiment of the invention is 339.8 m². 2 / kg, density is 3.1g / cm³ 3 The average particle size is 20.26 μm.

[0062] The fly ash used in this embodiment of the invention has a specific surface area of ​​702.1 m². 2 / kg, density is 2.32g / cm³ 3 The average particle size is 25.60 μm.

[0063] The specific surface area of ​​the silica fume used in this embodiment of the invention is 523.9 m². 2 / kg, density is 2.36g / cm³ 3 The average particle size is 15.21 μm.

[0064] The specific surface area of ​​the hollow glass microspheres used in this embodiment of the invention is 383.0 m². 2 / kg, density is 0.6g / cm³ 3 The average particle size is 20.10 μm.

[0065] The porous ceramic sand used in this embodiment of the invention has an average particle size of 198.4 μm and a porosity of 36.5%.

[0066] The copper-plated steel fiber used in this embodiment of the invention has a length of 13 mm, a diameter of 0.2 mm, a tensile strength of 2965 MPa, and a density of 7800 kg / m³.

[0067] Furthermore, to better illustrate the present invention, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that the present invention can be practiced without certain specific details. In some embodiments, materials, methods, and means well-known to those skilled in the art are not described in detail in order to highlight the spirit of the invention.

[0068] Example 1 A lightweight, low-shrinkage, ultra-high performance concrete comprises the following components by weight: 100 parts cement, 26.5 parts silica fume, 33.5 parts fly ash, 32.6 parts hollow glass microspheres, 86.7 parts porous ceramic sand, 2.0 parts HCSA expansion agent, 6.0 parts MgO expansion agent, 40.1 parts water, 4.0 parts polycarboxylate superplasticizer, and 25.6 parts copper-plated steel fiber. The water-cement ratio of the lightweight, low-shrinkage, ultra-high performance concrete is 0.2.

[0069] The aforementioned lightweight, low-shrinkage, ultra-high performance concrete was prepared using the following method: Step 1: Put the cementitious materials (cement, silica fume, fly ash and hollow glass microspheres) and the expansion agent HCSA and expansion agent MgO into the mixing pot and dry mix for 3 minutes; Step 2: Mix the polycarboxylate superplasticizer and water evenly, add it to the mixing pot of Step 1, and wet mix for 8 minutes to obtain the first slurry; Step 3: Slowly add porous ceramic sand to the first slurry and continue stirring for 8 minutes to obtain the second slurry; Step 4: Slowly sprinkle copper-plated steel fibers into the second slurry and continue stirring for 10 minutes until the steel fibers are evenly distributed in the slurry to obtain the third slurry; Step 5: Pour the third slurry into the mold to form it, cover it with a film and cure it for 1 day before demolding. Then, transfer it to water for curing (curing temperature is 20±2℃, humidity ≥95%) for 28 days to obtain lightweight, low-shrinkage, ultra-high performance concrete.

[0070] Example 2 This embodiment provides a lightweight, low-shrinkage, ultra-high-performance concrete, which differs from Embodiment 1 in that the weight parts of water in this embodiment are 36.1 parts, the weight parts of polycarboxylate superplasticizer are 5 parts, and the water-cement ratio is 0.18. All other aspects are the same as in Embodiment 1.

[0071] Example 3 This embodiment provides a lightweight, low-shrinkage, ultra-high-performance concrete. The difference between this embodiment and Embodiment 1 is that the weight percentage of water is 44.1 parts, the weight percentage of polycarboxylate superplasticizer is 3.6 parts, and the water-cement ratio is 0.22. All other components are the same as in Embodiment 1.

[0072] Example 4 This embodiment provides a lightweight, low-shrinkage, ultra-high performance concrete. The difference between this embodiment and Embodiment 1 is that the weight parts of the expansive agent HCSA are 4.0 parts and the weight parts of the expansive agent MgO are 4.0 parts, while the rest are the same as in Embodiment 1.

[0073] Example 5 This embodiment provides a lightweight, low-shrinkage, ultra-high performance concrete. The difference between this embodiment and Embodiment 1 is that the weight of copper-plated steel fiber in this embodiment is 34.1 parts, while the rest are the same as in Embodiment 1.

[0074] Example 6 This embodiment provides a lightweight, low-shrinkage, ultra-high performance concrete. The difference between this embodiment and Embodiment 1 is that the weight parts of cement in this embodiment are 93.4 parts and the weight parts of hollow glass microspheres are 39.2 parts, while the rest are the same as in Embodiment 1.

[0075] Comparative Example 1 This comparative example provides ultra-high performance concrete, which differs from Example 1 in that it replaces the porous ceramsite (86.7 parts by weight) in Example 1 with 62.6 parts by weight of closed-cell shale ceramsite, while all other aspects are the same as in Example 1.

[0076] Comparative Example 2 This comparative example provides ultra-high performance concrete, which differs from Example 1 in that it replaces the porous ceramic sand (86.7 parts by weight) in Example 1 with 65.1 parts by weight of pumice, while all other aspects are the same as in Example 1.

[0077] Comparative Example 3 This comparative example provides ultra-high performance concrete, which differs from Example 1 in that it replaces the porous ceramic sand (86.7 parts by weight) in Example 1 with 37.6 parts by weight of expanded perlite, while all other aspects are the same as in Example 1.

[0078] Performance testing (1) Apparent density (kg / m³) 3 The test was conducted in accordance with GB / T 50080-2016, "Standard for Test Methods of Performance of Ordinary Concrete Mixtures".

[0079] (2) Compressive strength (MPa): Tested in accordance with GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete".

[0080] (3) Flexural strength (MPa): The test shall be conducted in accordance with GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete".

[0081] (4) Volume shrinkage rate: The test shall be conducted in accordance with GB / T 50082-2024 "Standard for Test Methods of Long-term Performance and Durability of Concrete".

[0082] The ultra-high performance concrete from Examples 1-6 and Comparative Examples 1-3 were subjected to the above tests. The test results are shown in Table 1.

[0083] Table 1. Performance characterization of ultra-high performance concrete in Examples 1-6 and Comparative Examples 1-3

[0084] As shown in Table 1, compared with the conventional lightweight aggregates used in Comparative Examples 1-3, the ultra-high performance concrete obtained by using porous ceramic sand in Examples 1-6 of this invention has better compressive strength and flexural strength while maintaining a lower apparent density. Specifically, the volume shrinkage rate of the ultra-high performance concrete in Comparative Examples 1-3 is approximately 2-3 times that of Examples 1-6, and the volume shrinkage rate of the ultra-high performance concrete in Examples 1-6 is significantly lower than that in Comparative Examples 1-3. This indicates that the porous ceramic sand and the expanding agent in the embodiments of this invention have a synergistic effect, effectively improving the expansion efficiency and reducing the shrinkage of UHPC.

[0085] In summary, this invention uses porous ceramic sand to completely replace quartz sand as aggregate and hollow glass microspheres to partially replace cement, thereby reducing the apparent density of UHPC. The pores inside the porous ceramic sand can absorb and store moisture, which is gradually released within the UHPC matrix, reducing capillary negative pressure and supplying the expanding agent to react and generate expansion products. These products work synergistically with the expanding agent, effectively inhibiting UHPC shrinkage.

[0086] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A lightweight, low-shrinkage, ultra-high-performance concrete, characterized in that, The lightweight, low-shrinkage, ultra-high performance concrete comprises the following components by weight: 80-110 parts cement, 20-30 parts silica fume, 30-45 parts fly ash, 28-45 parts hollow glass microspheres, 80-95 parts porous ceramic sand, 5-10 parts expansion agent, 30-50 parts water, 2-10 parts water-reducing agent, and 20-40 parts steel fiber.

2. The lightweight, low-shrinkage, ultra-high-performance concrete according to claim 1, characterized in that, The water-cement ratio of the lightweight, low-shrinkage, ultra-high performance concrete is 0.16~0.

25.

3. The lightweight, low-shrinkage, ultra-high-performance concrete according to claim 1, characterized in that, The porous ceramic sand is water-treated porous ceramic sand.

4. The lightweight, low-shrinkage, ultra-high-performance concrete according to claim 1, characterized in that, The expanding agent includes at least one of calcium sulfoaluminate expanding agents, calcium sulfoaluminate-calcium oxide expanding agents, and magnesium oxide expanding agents.

5. The lightweight, low-shrinkage, ultra-high-performance concrete according to claim 1, characterized in that, The water-reducing agent includes a polycarboxylate water-reducing agent; And / or, the steel fibers include copper-plated steel fibers.

6. The lightweight, low-shrinkage, ultra-high performance concrete according to claim 1, characterized in that, The specific surface area of ​​the cement is 330~350 m². 2 / kg, density is 2.5~4g / cm³ 3 The average particle size is 18~25μm; And / or, the specific surface area of ​​the fly ash is 680~720 m². 2 / kg, density is 2~4g / cm³ 3 The average particle size is 22~30μm; And / or, the specific surface area of ​​the silica fume is 500~550 m². 2 / kg, density is 2~4g / cm³ 3 The average particle size is 10~20μm; And / or, the specific surface area of ​​the hollow glass microspheres is 350~420 m². 2 / kg, density is 0.3~1g / cm³ 3 The average particle size is 15~25μm; And / or, the porous ceramic sand has an average particle size of 180~220μm and a porosity of 30%~40%.

7. The lightweight, low-shrinkage, ultra-high performance concrete according to claim 1, characterized in that, The apparent density of the lightweight, low-shrinkage, ultra-high-performance concrete is ≤1870 kg / m³. 3 ; And / or, the compressive strength of the lightweight, low-shrinkage, ultra-high performance concrete is ≥100MPa; And / or, the flexural strength of the lightweight, low-shrinkage, ultra-high performance concrete is ≥19MPa; And / or, the drying shrinkage rate of the lightweight, low-shrinkage, ultra-high performance concrete is ≤150×10⁻⁶. -6 .

8. The method for preparing lightweight, low-shrinkage, ultra-high performance concrete according to any one of claims 1 to 7, characterized in that, Includes the following steps: S1: Mix and stir the components except for porous ceramic sand and steel fiber to obtain the first slurry; S2: Add porous ceramic sand to the first slurry described in step S1 and mix to obtain a second slurry; S3: Add steel fibers to the second slurry described in step S2 and mix to obtain a third slurry; S4: The third slurry is poured and cured to the set age to obtain the lightweight, low-shrinkage, ultra-high performance concrete.

9. The preparation method according to claim 8, characterized in that, The stirring time in step S2 is 5-10 minutes; And / or, the stirring time in step S3 is 8~12 min; And / or, the curing time in step S4 is >24 days.

10. The application of the lightweight, low-shrinkage, ultra-high performance concrete according to any one of claims 1 to 7 in the fields of bridges, building exterior walls, roads, or pipelines.

Images