Low-viscosity low-shrinkage ultrahigh-strength concrete and preparation method thereof

Abstract

The invention relates to the field of ultrahigh-strength concrete, in particular to low-viscosity low-shrinkage ultrahigh-strength concrete and a preparation method thereof. The low-viscosity low-shrinkage ultrahigh-strength concrete comprises the following substances in parts by weight: 30-50 parts of cement; 80 to 120 parts of basalt coarse aggregate; 60 to 80 parts of fine aggregate; 10 to 20 parts of water; 0.1 to 0.3 part of a water reducing agent; the basalt coarse aggregate is a porous basalt coarse aggregate with the pore diameter of 1-50 [mu] m and the porosity of 5-15%. The traditional aggregate is replaced by the porous basalt coarse aggregate, the density of the concrete is reduced and the aggregate-slurry interface bonding is optimized by utilizing the internal pore structure of the porous basalt coarse aggregate, and meanwhile, the proportioning range of the cement, the fine aggregate, the water and the water reducing agent is limited, so that high strength and low viscosity of the concrete under the low water-binder ratio are ensured. Due to the introduction of the porous aggregate, drying shrinkage can be reduced through pore water absorption-water release balance.

Description

Technical Field

[0001] This application relates to the field of ultra-high strength concrete, and particularly to a low-viscosity and low-shrinkage ultra-high strength concrete and its preparation method. Background Art

[0002] With the development of modern architecture towards ultra-high-rise, large-span and complex structures, the high-strengthening, functionalization and durability improvement of concrete materials have become key requirements in the engineering field. Although traditional high-strength concrete achieves high strength through high cement dosage and low water-binder ratio, problems such as difficult pumping caused by its high viscosity, cracking risk caused by high shrinkage, and weak aggregate-paste interface are becoming increasingly prominent. Taking basalt aggregate as an example, although its dense characteristics can improve mechanical properties, the interface bonding with the cement matrix is insufficient, easily forming stress concentration areas and exacerbating the expansion of shrinkage cracks. In addition, although traditional expansion agents can compensate for shrinkage, they have defects such as excessive early expansion and later shrinkage rebound, and it is difficult to match the hydration process of high-strength concrete. Traditional solutions often replace part of the cement with mineral admixtures to reduce shrinkage, but too high admixture content will sacrifice early strength; fiber reinforcement (although it can inhibit cracks, significantly increases viscosity). Therefore, how to synergistically solve the contradictions of low viscosity, low shrinkage and interface strengthening while ensuring ultra-high strength has become the core challenge in the technological innovation of high-strength concrete.

[0003] In view of the above-mentioned existing technologies, the inventors found that the contradiction between viscosity and strength in the existing high-strength concrete technology is prominent. The high binder system results in viscous paste, and in construction, it is necessary to rely on a large amount of water-reducing agent, which is prone to segregation and costly; at the same time, the aggregate-matrix interface is weak, the elastic modulus difference between the dense aggregate and the cement paste is large, and the porosity of the interfacial transition zone is high, becoming a shortcoming in durability. The above defects severely restrict the application potential of high-strength concrete in harsh engineering scenarios. Summary of the Invention

[0004] To improve the above technical problems, this application provides a low-viscosity and low-shrinkage ultra-high strength concrete and its preparation method.

[0005] In the first aspect, this application provides a low-viscosity and low-shrinkage ultra-high strength concrete, adopting the following technical solution: A low-viscosity and low-shrinkage ultra-high strength concrete, comprising the following substances in parts by weight: Cement 30 - 50 parts; Coarse basalt aggregate 80 - 120 parts; Fine aggregate 60 - 80 parts; Water 10 - 20 parts; Water-reducing agent 0.1 - 0.3 parts; The coarse basalt aggregate is a porous coarse basalt aggregate with a pore diameter of 1 - 50 μm and a porosity of 5 - 15%.

[0006] Through the above technical solution, in this application, porous basalt coarse aggregate is used to replace traditional aggregate, and its internal pore structure is utilized to reduce the density of concrete and optimize the interfacial bonding between aggregate and paste. At the same time, the mixing ratio ranges of cement, fine aggregate, water and water reducer are limited to ensure that high strength and low viscosity are achieved under a low water-binder ratio. The introduction of porous aggregate can also reduce drying shrinkage through the balance of pore water absorption and release.

[0007] Furthermore, an expansion modifier is filled in the porous basalt coarse aggregate.

[0008] Through the above technical solution, in this application, an expansion modifier is filled in the pores of porous basalt aggregate to compensate for shrinkage through chemical expansion. After the expansion agent absorbs water, a hydration reaction occurs, generating expansion stress in the initial stage of concrete hardening to offset the chemical shrinkage and drying shrinkage of the cement matrix. The pores act as a "storage reservoir" for the expansion agent, controlling the release rate of the expansion agent to synchronize its expansion peak with the concrete shrinkage process.

[0009] Furthermore, the expansion modifier is fly ash and basalt chopped fibers mixed in a mass ratio of 1:(3 - 5).

[0010] Through the above technical solution, in this application, the reactive SiO2 and Al2O3 in fly ash react with the cement hydration product Ca(OH)2 to form C-S-H gel, generating micro-expansion, filling pores and enhancing the late strength. The basalt fibers form a three-dimensional network in the matrix, inhibiting the propagation of micro-cracks through bridging action and enhancing the fracture energy. The synergistic effect of fibers and fly ash reduces interface defects and optimizes stress distribution. The composite system improves the flexural strength of concrete, and at the same time, through the synergy of micro-expansion and fiber restraint, reduces the shrinkage rate of concrete materials.

[0011] Furthermore, the aspect ratio of the basalt chopped fibers is 800 - 1200, and the diameter is 1 - 20 μm.

[0012] Through the above technical solution, in this application, the aspect ratio and diameter of basalt fibers are limited. Denser crack resistance networks are formed in the matrix by fibers with a high aspect ratio, enhancing the crack spanning ability; at the same time, it avoids the fracture of too long fibers due to stirring shear force. Fine-diameter fibers reduce the interference with the fluidity of the paste, and with an increased specific surface area, enhance the fiber-matrix interfacial bonding strength. Effect: The optimized fibers improve the toughness of concrete and achieve the balance of high strength and low viscosity.

[0013] Furthermore, the basalt chopped fibers are surface-treated basalt chopped fibers, and the surface treatment steps include: Take a silane coupling agent and add it to ethanol, stir and mix to collect the modified liquid; Immerse the chopped basalt fibers in the modified liquid. After the immersion treatment, allow it to dry naturally to prepare the surface-treated chopped basalt fibers.

[0014] Through the above technical solution, in this application, the silane coupling agent is evenly coated on the fiber surface through an ethanol solvent, undergoes a hydrolysis reaction to generate silanol groups, and reacts with the hydroxyl groups on the basalt surface and Ca in the cement hydration products 2+ to form chemical bonds (Si-O-Si and Si-O-Ca), enhancing the interfacial bonding. The alkali resistance of the treated fibers is improved, preventing the fibers from corroding and failing in an alkaline environment. The interfacial bonding strength of the surface-treated fibers is increased, and the fiber pull-out work is improved, significantly delaying the crack propagation.

[0015] Furthermore, the surface of the porous basalt coarse aggregate is also coated with a xanthan gum coating layer.

[0016] Through the above technical solution, in this application, a xanthan gum layer is coated on the surface of the porous aggregate, which gradually hydrolyzes in the initial stage of concrete hardening and slowly releases the expansive agent in the pores, avoiding ineffective expansion caused by premature water absorption. The pseudoplastic behavior of xanthan gum reduces the yield stress of the paste, making the pumping viscosity of the concrete meet the requirements of self-compacting. With the xanthan gum coating layer, the utilization rate of the expansive agent is increased, meeting the requirements of super high-rise pumping construction.

[0017] Furthermore, the xanthan gum coating layer is prepared by coating with a xanthan gum coating liquid, and the xanthan gum coating liquid includes the following substances in parts by weight: Xanthan gum 20 - 50 parts; Dispersant 5 - 10 parts; Penetration promoter 1 - 5 parts.

[0018] Furthermore, the xanthan gum is xanthan gum after enzymatic modification, and the enzymatic modification includes the following steps: Take xanthan gum and dissolve it in a 1% phosphate buffer solution with pH = 6, add cellulase for enzymatic hydrolysis treatment, and then the xanthan gum after enzymatic modification can be prepared; The molecular weight of the xanthan gum after enzymatic modification is 80 - 100 kDa.

[0019] Through the above technical solution, in this application, the molecular weight of xanthan gum is reduced from 200 kDa to 80 - 100 kDa through enzymatic modification. The low-molecular-weight xanthan gum is more likely to penetrate into the pores of the aggregate to form a continuous sealing layer. After enzymatic hydrolysis, the molecular chain flexibility of xanthan gum increases, and it synergizes with the dispersant and penetration promoter to form a dense and erosion-resistant film structure on the aggregate surface, so that the sealing layer remains intact during the concrete mixing process, and the release rate of the expansive agent highly matches the cement hydration process.

[0020] In a second aspect, the present application provides a method for preparing a low-viscosity, low-shrinkage, ultra-high-strength concrete, which adopts the following technical solutions: A method for preparing a low-viscosity, low-shrinkage, ultra-high-strength concrete, comprising the following preparation steps: Take cement, basalt coarse aggregate and fine aggregate, mix them and place them in a stirring device, stir and mix to collect a mixture; Inject a water reducing agent and water into the mixture in three times, stir and mix to collect a slurry; Take the slurry, pour it, and perform curing treatment to prepare a low-viscosity, low-shrinkage, ultra-high-strength concrete.

[0021] Through the above technical solutions, the present application combines material modification (porous aggregate, fiber treatment), functional components (expansive agent, xanthan gum) and process innovation (step-by-step stirring) to solve the problems of shrinkage, viscosity and weak interface of high-strength concrete.

[0022] In summary, the present application has the following beneficial effects: First, the present application uses porous basalt coarse aggregate to replace the traditional aggregate, utilizes its internal pore structure to reduce the density of the concrete and optimize the interfacial bonding between the aggregate and the paste. At the same time, the mixing ratios of cement, fine aggregate, water and water reducing agent are limited to ensure high strength and low viscosity of the concrete under a low water-binder ratio. The introduction of porous aggregate can also reduce drying shrinkage through the balance of pore water absorption and release.

[0023] Second, the present application fills the pores of the porous basalt aggregate with an expansion modifier to compensate for shrinkage through chemical expansion. After the expansive agent absorbs water, it undergoes a hydration reaction, generating an expansion stress at the initial stage of concrete hardening to offset the chemical shrinkage and drying shrinkage of the cement matrix. The pores serve as a "storage depot" for the expansive agent, controlling the release rate of the expansive agent to synchronize its expansion peak with the concrete shrinkage process.

[0024] Third, the present application coats the surface of the porous aggregate with a xanthan gum layer, which gradually hydrolyzes at the initial stage of concrete hardening and slowly releases the expansive agent in the pores, avoiding ineffective expansion caused by premature water absorption. The pseudoplastic behavior of xanthan gum reduces the yield stress of the paste, making the pumping viscosity of the concrete meet the requirements of self-compacting. The utilization rate of the expansive agent is increased through the xanthan gum coating layer, meeting the requirements of super high-rise pumping construction. Specific embodiments

[0025] The following further elaborates on the present application with reference to examples.

[0026] Preparation Example 1 Porous basalt coarse aggregate First, crush basalt to 5 - 20 mm. After washing and drying, soak it in 5% hydrochloric acid by mass for 3 h, then rinse it with 5% sodium bicarbonate solution by mass, and then soak it in 10% sodium hydroxide solution for 2 h. After rinsing with water until the washing liquid is neutral, porous basalt coarse aggregate with a pore size of 1 - 50 μm and a porosity of 10% is prepared.

[0027] Preparation Example 2 Expansion modifier 1 Mix fly ash and basalt short fibers with an aspect ratio of 800 - 1200 and a diameter of 1 - 20 μm by a mass ratio of 1:3, and stir - mix to obtain expansion modifier 1.

[0028] Preparation Example 3 Expansion modifier 2 Mix fly ash and basalt short fibers with an aspect ratio of 800 - 1200 and a diameter of 1 - 20 μm by a mass ratio of 1:4, and stir - mix to obtain expansion modifier 2.

[0029] Preparation Example 4 Expansion modifier 3 Mix fly ash and basalt short fibers with an aspect ratio of 800 - 1200 and a diameter of 1 - 20 μm by a mass ratio of 1:5, and stir - mix to obtain expansion modifier 3.

[0030] Preparation Example 5 Surface - treated basalt short fibers Take 20 g of silane coupling agent KH - 550 and add it to 500 mL of absolute ethanol, stir - mix and collect to obtain the modification liquid; Immerse 200 g of basalt short fibers in the modification liquid. After immersion treatment, dry naturally to obtain surface - treated basalt short fibers.

[0031] Preparation Example 6 Expansion modifier 4 Mix fly ash and surface - treated basalt short fibers with an aspect ratio of 800 - 1200 and a diameter of 1 - 20 μm by a mass ratio of 1:4, and stir - mix to obtain expansion modifier 4.

[0032] Preparation Example 7 Gellan gum coating liquid 1 Take 200 g of gellan gum, 50 g of dispersant PCE - DF30, 10 g of penetration promoter SDS and 10 kg of water, stir - mix to obtain gellan gum coating liquid 1.

[0033] Preparation Example 8 Gellan gum coating liquid 2 Take 350 g of welan gum, 75 g of dispersant PCE-DF30, 30 g of penetration promoter SDS and 10 kg of water, stir and mix them to prepare welan gum coating solution 2.

[0034] Preparation Example 9 Welan gum coating solution 3 Take 500 g of welan gum, 100 g of dispersant PCE-DF30, 50 g of penetration promoter SDS and 10 kg of water, stir and mix them to prepare welan gum coating solution 3.

[0035] Preparation Example 10 Take welan gum and dissolve it in a buffer solution of disodium hydrogen phosphate and sodium dihydrogen phosphate with a mass fraction of 1% at pH = 6. After adding cellulase for enzymatic hydrolysis treatment, enzymatically modified welan gum with a molecular weight of 80 - 100 kDa can be prepared.

[0036] Preparation Example 11 Take swelling modifier 1 and add it to water at a solid content of 20%, add sodium polycarboxylate with a mass fraction of 1% and stir and mix, then collect the mixed slurry; Take the mixed slurry and stir and mix it with porous basalt coarse aggregate and perform pressure treatment. After maintaining the pressure for 30 min, dry it with hot air until there is no visible water on the surface, and then dry it at 60 °C for 2 h to prepare modified porous basalt coarse aggregate 1.

[0037] Preparation Example 12 Take swelling modifier 2 and add it to water at a solid content of 20%, add sodium polycarboxylate with a mass fraction of 1% and stir and mix, then collect the mixed slurry; Take the mixed slurry and stir and mix it with porous basalt coarse aggregate and perform pressure treatment. After maintaining the pressure for 30 min, dry it with hot air until there is no visible water on the surface, and then dry it at 60 °C for 2 h to prepare modified porous basalt coarse aggregate 2.

[0038] Preparation Example 13 Take swelling modifier 3 and add it to water at a solid content of 20%, add sodium polycarboxylate with a mass fraction of 1% and stir and mix, then collect the mixed slurry; Take the mixed slurry and stir and mix it with porous basalt coarse aggregate and perform pressure treatment. After maintaining the pressure for 30 min, dry it with hot air until there is no visible water on the surface, and then dry it at 60 °C for 2 h to prepare modified porous basalt coarse aggregate 3.

[0039] Preparation Example 14 Take swelling modifier 4 and add it to water at a solid content of 20%, add sodium polycarboxylate with a mass fraction of 1% and stir and mix, then collect the mixed slurry; Mix the mixed slurry with the porous basalt coarse aggregate, stir and mix them, and apply pressure. After maintaining the pressure for 30 minutes, dry them with hot air until there is no visible free water on the surface, and then dry them at 60 °C for 2 hours to prepare the modified porous basalt coarse aggregate 4.

[0040] Preparation Example 15 Add the expansion modifier 2 to water at a solid content of 20%, add 1% by mass of sodium polyacrylate and stir and mix, and collect the mixed slurry; Mix the mixed slurry with the porous basalt coarse aggregate, stir and mix them, and apply pressure. After maintaining the pressure for 30 minutes, dry them with hot air until there is no visible free water on the surface, and then dry them at 60 °C for 2 hours. Then, take the welan gum coating solution 1 and spray it onto the surface of the porous basalt coarse aggregate. The spraying amount is 2 - 3 g of welan gum coating solution / 100 g of aggregate, and cure it with hot air at 60 °C for 30 minutes to form a continuous film layer with a thickness of 1 - 2 μm, thus preparing the modified porous basalt coarse aggregate 5.

[0041] Preparation Example 16 Add the expansion modifier 2 to water at a solid content of 20%, add 1% by mass of sodium polyacrylate and stir and mix, and collect the mixed slurry; Mix the mixed slurry with the porous basalt coarse aggregate, stir and mix them, and apply pressure. After maintaining the pressure for 30 minutes, dry them with hot air until there is no visible free water on the surface, and then dry them at 60 °C for 2 hours. Then, take the welan gum coating solution 2 and spray it onto the surface of the porous basalt coarse aggregate. The spraying amount is 2 - 3 g of welan gum coating solution / 100 g of aggregate, and cure it with hot air at 60 °C for 30 minutes to form a continuous film layer with a thickness of 1 - 2 μm, thus preparing the modified porous basalt coarse aggregate 6.

[0042] Preparation Example 17 Add the expansion modifier 2 to water at a solid content of 20%, add 1% by mass of sodium polyacrylate and stir and mix, and collect the mixed slurry; Mix the mixed slurry with the porous basalt coarse aggregate, stir and mix them, and apply pressure. After maintaining the pressure for 30 minutes, dry them with hot air until there is no visible free water on the surface, and then dry them at 60 °C for 2 hours. Then, take the welan gum coating solution 3 and spray it onto the surface of the porous basalt coarse aggregate. The spraying amount is 2 - 3 g of welan gum coating solution / 100 g of aggregate, and cure it with hot air at 60 °C for 30 minutes to form a continuous film layer with a thickness of 1 - 2 μm, thus preparing the modified porous basalt coarse aggregate 7.

[0043] Examples Example 1 A low-viscosity, low-shrinkage, ultra-high-strength concrete comprises the following substances by weight: 30 kg of cement, 80 kg of porous basalt coarse aggregate, 60 kg of fine aggregate, 10 kg of water, and 0.1 kg of water reducer.

[0044] A preparation method of a low-viscosity, low-shrinkage, ultra-high-strength concrete comprises the following steps: Take cement, basalt coarse aggregate and fine aggregate, mix them and place them in a stirring device, stir and mix them, and collect the mixture; Inject water reducing agent and water into the mixture in three times, stir and mix them, and collect the slurry; Take the slurry, pour it, and perform natural curing for 28 days to prepare low-viscosity, low-shrinkage and ultra-high-strength concrete.

[0045] Example 2 A low-viscosity, low-shrinkage and ultra-high-strength concrete comprises the following substances by weight: 40 kg of cement, 100 kg of porous basalt coarse aggregate, 70 kg of fine aggregate, 15 kg of water and 0.2 kg of water reducing agent.

[0046] A preparation method of a low-viscosity, low-shrinkage and ultra-high-strength concrete comprises the following steps: Take cement, basalt coarse aggregate and fine aggregate, mix them and place them in a stirring device, stir and mix them, and collect the mixture; Inject water reducing agent and water into the mixture in three times, stir and mix them, and collect the slurry; Take the slurry, pour it, and perform natural curing for 28 days to prepare low-viscosity, low-shrinkage and ultra-high-strength concrete.

[0047] Example 3 A low-viscosity, low-shrinkage and ultra-high-strength concrete comprises the following substances by weight: 50 kg of cement, 120 kg of porous basalt coarse aggregate, 80 kg of fine aggregate, 20 kg of water and 0.3 kg of water reducing agent.

[0048] A preparation method of a low-viscosity, low-shrinkage and ultra-high-strength concrete comprises the following steps: Take cement, basalt coarse aggregate and fine aggregate, mix them and place them in a stirring device, stir and mix them, and collect the mixture; Inject water reducing agent and water into the mixture in three times, stir and mix them, and collect the slurry; Take the slurry, pour it, and perform natural curing for 28 days to prepare low-viscosity, low-shrinkage and ultra-high-strength concrete.

[0049] Example 4 A low-viscosity, low-shrinkage and ultra-high-strength concrete comprises the following substances by weight: 30 kg of cement, 80 kg of porous basalt coarse aggregate 1, 60 kg of fine aggregate, 10 kg of water and 0.1 kg of water reducing agent.

[0050] A preparation method of a low-viscosity, low-shrinkage and ultra-high-strength concrete comprises the following steps: Take cement, basalt coarse aggregate and fine aggregate, mix them and place them in a stirring device, stir and mix them, and collect the mixture; Inject water reducing agent and water into the mixture in three times, stir and mix them, and collect the slurry; After taking the slurry and pouring it, perform natural curing for 28 days to prepare a low-viscosity, low-shrinkage, ultra-high-strength concrete.

[0051] Example 5 A low-viscosity, low-shrinkage, ultra-high-strength concrete comprises the following substances by weight: 30 kg of cement, 80 kg of porous basalt coarse aggregate 2, 60 kg of fine aggregate, 10 kg of water, and 0.1 kg of water reducer.

[0052] A method for preparing a low-viscosity, low-shrinkage, ultra-high-strength concrete comprises the following steps: Take cement, basalt coarse aggregate, and fine aggregate, mix them and place them in a stirring device, stir and mix them to collect a mixture; Inject the water reducer and water into the mixture in three portions, stir and mix them to collect a slurry; After taking the slurry and pouring it, perform natural curing for 28 days to prepare a low-viscosity, low-shrinkage, ultra-high-strength concrete.

[0053] Example 6 A low-viscosity, low-shrinkage, ultra-high-strength concrete comprises the following substances by weight: 30 kg of cement, 80 kg of porous basalt coarse aggregate 3, 60 kg of fine aggregate, 10 kg of water, and 0.1 kg of water reducer.

[0054] A method for preparing a low-viscosity, low-shrinkage, ultra-high-strength concrete comprises the following steps: Take cement, basalt coarse aggregate, and fine aggregate, mix them and place them in a stirring device, stir and mix them to collect a mixture; Inject the water reducer and water into the mixture in three portions, stir and mix them to collect a slurry; After taking the slurry and pouring it, perform natural curing for 28 days to prepare a low-viscosity, low-shrinkage, ultra-high-strength concrete.

[0055] Example 7 A low-viscosity, low-shrinkage, ultra-high-strength concrete comprises the following substances by weight: 30 kg of cement, 80 kg of porous basalt coarse aggregate 4, 60 kg of fine aggregate, 10 kg of water, and 0.1 kg of water reducer.

[0056] A method for preparing a low-viscosity, low-shrinkage, ultra-high-strength concrete comprises the following steps: Take cement, basalt coarse aggregate, and fine aggregate, mix them and place them in a stirring device, stir and mix them to collect a mixture; Inject the water reducer and water into the mixture in three portions, stir and mix them to collect a slurry; After taking the slurry and pouring it, perform natural curing for 28 days to prepare a low-viscosity, low-shrinkage, ultra-high-strength concrete.

[0057] Example 8 A low-viscosity, low-shrinkage, ultra-high-strength concrete comprises the following substances by weight: 30 kg of cement, 80 kg of porous basalt coarse aggregate 5, 60 kg of fine aggregate, 10 kg of water, and 0.1 kg of water reducer.

[0058] A method for preparing a low-viscosity, low-shrinkage, ultra-high-strength concrete comprises the following steps: Take cement, basalt coarse aggregate, and fine aggregate, mix them, and place them in a stirring device. Stir and mix them to collect a mixture. Inject the water reducer and water into the mixture in three portions, stir and mix them, and collect a slurry. Take the slurry, pour it, and then perform natural curing for 28 days to prepare the low-viscosity, low-shrinkage, ultra-high-strength concrete.

[0059] Example 9 A low-viscosity, low-shrinkage, ultra-high-strength concrete comprises the following substances by weight: 30 kg of cement, 80 kg of porous basalt coarse aggregate 6, 60 kg of fine aggregate, 10 kg of water, and 0.1 kg of water reducer.

[0060] A method for preparing a low-viscosity, low-shrinkage, ultra-high-strength concrete comprises the following steps: Take cement, basalt coarse aggregate, and fine aggregate, mix them, and place them in a stirring device. Stir and mix them to collect a mixture. Inject the water reducer and water into the mixture in three portions, stir and mix them, and collect a slurry. Take the slurry, pour it, and then perform natural curing for 28 days to prepare the low-viscosity, low-shrinkage, ultra-high-strength concrete.

[0061] Example 10 A low-viscosity, low-shrinkage, ultra-high-strength concrete comprises the following substances by weight: 30 kg of cement, 80 kg of porous basalt coarse aggregate 7, 60 kg of fine aggregate, 10 kg of water, and 0.1 kg of water reducer.

[0062] A method for preparing a low-viscosity, low-shrinkage, ultra-high-strength concrete comprises the following steps: Take cement, basalt coarse aggregate, and fine aggregate, mix them, and place them in a stirring device. Stir and mix them to collect a mixture. Inject the water reducer and water into the mixture in three portions, stir and mix them, and collect a slurry. Take the slurry, pour it, and then perform natural curing for 28 days to prepare the low-viscosity, low-shrinkage, ultra-high-strength concrete.

[0063] Comparative Example 1 A low-viscosity, low-shrinkage, ultra-high-strength concrete, compared with Example 1, uses traditional basalt coarse aggregate instead of porous basalt coarse aggregate, and the other components and steps are the same as those in Example 1.

[0064] Comparative Example 2 A low-viscosity, low-shrinkage, ultra-high-strength concrete, compared with Example 1, uses traditional basalt coarse aggregate instead of porous basalt coarse aggregate and adds 0.1 kg of expansion modifier 1, and the other components and steps are the same as those in Example 1.

[0065] Performance testing Compressive strength: GB / T 50081-2019, specimen size 100 mm × 100 mm × 100 mm, loading rate 0.5 MPa / s.

[0066] Dry shrinkage rate: GB / T 50082-2009, specimen size 100 mm × 100 mm × 515 mm, cured under constant temperature and humidity (20°C, RH 60%).

[0067] Slump: GB / T 50080-2016, slump cone method, testing initial fluidity.

[0068] The test results are shown in Table 1 below: Table 1 Performance test table It can be found from the comparison between Examples 1-3 and Comparative Example 1 that the technical solution of this application replaces traditional aggregates with porous basalt coarse aggregates, uses their internal pore structure to reduce the density of concrete and optimize the interfacial bonding between aggregates and paste, and at the same time limits the mixing ratio range of cement, fine aggregate, water and water reducer to ensure that high strength and low viscosity are achieved under a low water-binder ratio. The introduction of porous aggregates can also reduce dry shrinkage through the water absorption-desorption balance of pores.

[0069] Combined with the comparison between Examples 4-7, Comparative Example 2 and Examples 1-3, it shows that the technical solution of this application fills the pores of porous basalt aggregates with expansion modifiers to compensate for shrinkage through chemical expansion. After the expansion agent absorbs water, it undergoes a hydration reaction, generating expansion stress in the early stage of concrete hardening to offset the chemical shrinkage and dry shrinkage of the cement matrix. The pores act as a "storage depot" for the expansion agent, controlling the release rate of the expansion agent to make its expansion peak synchronous with the concrete shrinkage process.

[0070] Finally, combined with the comparison between Examples 8-10 and Examples 4-7, it further shows that this application coats the surface of porous aggregates with a xanthan gum layer, which gradually hydrolyzes in the early stage of concrete hardening and slowly releases the expansion agent in the pores, avoiding ineffective expansion caused by premature water absorption. The pseudoplastic behavior of xanthan gum reduces the yield stress of the paste, making the pumping viscosity of the concrete meet the requirements of self-compacting. The utilization rate of the expansion agent is increased through the xanthan gum coating layer, meeting the requirements of super high-rise pumping construction.

[0071] This specific embodiment is only an interpretation of the present application and does not limit the present application. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions as needed, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A low-viscosity, low-shrinkage, ultra-high-strength concrete, characterized in that, It includes the following substances in parts by weight: Cement: 30 - 50 parts; Basalt coarse aggregate: 80 - 120 parts; Fine aggregate: 60 - 80 parts; Water: 10 - 20 parts; Water reducing agent: 0.1 - 0.3 part; The basalt coarse aggregate is a porous basalt coarse aggregate with a pore diameter of 1 - 50 μm and a porosity of 5 - 15%.

2. The low-viscosity, low-shrinkage, ultra-high-strength concrete according to claim 1, wherein The porous basalt coarse aggregate is also filled with an expansion modifier.

3. A low-viscosity, low-shrinkage, ultra-high-strength concrete according to claim 1, characterized in that, The expansion modifier is fly ash and basalt chopped fibers mixed in a mass ratio of 1:(3 - 5).

4. A low-viscosity, low-shrinkage, ultra-high-strength concrete according to claim 3, characterized in that, The aspect ratio of the basalt chopped fibers is 800 - 1200, and the diameter is 1 - 20 μm.

5. A low-viscosity, low-shrinkage, ultra-high-strength concrete according to claim 3, characterized in that, The basalt chopped fibers are surface - treated basalt chopped fibers, and the surface treatment steps include: Take a silane coupling agent and add it to ethanol, stir and mix to collect a modified liquid; Immerse the basalt chopped fibers in the modified liquid, after impregnation treatment, dry naturally to obtain the surface - treated basalt chopped fibers.

6. The low-viscosity, low-shrinkage, ultra-high-strength concrete according to claim 3, characterized in that, The surface of the porous basalt coarse aggregate is also coated with a xanthan gum coating layer.

7. A low-viscosity, low-shrinkage, ultra-high-strength concrete according to claim 3, characterized in that The xanthan gum coating layer is prepared by coating with a xanthan gum coating liquid, and the xanthan gum coating liquid includes the following substances in parts by weight: Xanthan gum: 20 - 50 parts; Dispersant: 5 - 10 parts; Penetration promoter: 1 - 5 parts.

8. A low-viscosity, low-shrinkage, ultra-high-strength concrete according to claim 7, characterized in that, The xanthan gum is xanthan gum after enzymatic modification, and the enzymatic modification includes the following steps: Take xanthan gum and dissolve it in a 1% phosphate buffer solution with pH = 6, add cellulase for enzymatic hydrolysis treatment to obtain xanthan gum after enzymatic modification; The molecular weight of the xanthan gum after enzymatic modification is 80 - 100 kDa.

9. The preparation method of a low-viscosity, low-shrinkage, ultra-high-strength concrete according to claims 1-8, characterized in that, It includes the following preparation steps: Take cement, basalt coarse aggregate and fine aggregate, mix them and place them in a stirring device, stir and mix to collect a mixture; Inject the water reducing agent and water into the mixture in three times, stir and mix to collect a slurry; Take the slurry, pour it, and perform curing treatment to obtain low - viscosity, low - shrinkage, ultra - high - strength concrete.

Images