Ultra-high performance concrete and preparation method thereof

Abstract

The invention discloses ultra-high-performance concrete (UHPC) and a preparation method thereof.The ultra-high-performance concrete is prepared from metal oxide, phosphate, magnesium chloride, nano calcium carbonate, fine aggregate, hybrid fibers and water, and the ultra-high-performance concrete is prepared by adding a multi-element cementing system and a nano calcium carbonate nucleating material into the UHPC; the UHPC has ultrahigh early strength and no volume shrinkage, and meanwhile, the three-dimensional hybrid fibers are doped, so that the tensile strength of the UHPC can be greatly improved, shrinkage cracks or temperature cracks are reduced, the structural performance is enhanced, the bonding force between the UHPC and external structures such as steel plates and old concrete is improved, and the problems of insufficient early strength, cracking, void and the like of the concrete are prevented.

Description

Technical Field

[0001] The present application relates to the technical field of building materials, and in particular to an ultra-high performance concrete and a preparation method thereof. Background Art

[0002] Ultra-High Performance Concrete (UHPC) is a major achievement in the field of building materials. With its excellent mechanical properties and durability, it has shown great application potential in many fields. However, in the pursuit of higher performance and wider application range, UHPC still faces a series of challenges, especially in the application of rapid construction and special engineering fields, where its limitations are particularly obvious.

[0003] From the perspective of strength development, although the later strength of UHPC has been significantly improved, its early strength development after pouring is relatively slow, especially within two hours after pouring, the strength generally does not exceed 50MPa. This feature makes it difficult for UHPC to meet the demand for rapid hardening of materials in rapid construction projects, thus limiting its application in emergency repair scenarios such as airport rapid repair, road rapid maintenance, and emergency repair of fortifications. The early strength of ordinary UHPC is generally low, and when early strength agent or early strength cement is used, the cement hydration strength develops too quickly, which is easy to produce a large volume shrinkage in a short time, resulting in voids or cracks inside the structure, and insufficient bonding between UHPC and structures such as steel bars and old concrete, which leads to problems such as degassing, cracking or slipping of the structure, seriously reducing the durability, fatigue resistance and safety stability of the overall structure. In addition, the tensile strength of UHPC is relatively low, generally not exceeding 15MPa, which hinders the application of UHPC in new or rapid repair projects such as large-span structures and fortifications with high tensile strength and high impact toughness. Summary of the invention

[0004] In view of the above-mentioned shortcomings of the current UHPC, the present application provides an ultra-early-strength, high-tensile, shrinkage-free UHPC, which can greatly improve the early strength and tensile strength of UHPC, avoid slurry shrinkage, improve the tensile strength and toughness of UHPC itself, and its adhesion with other structures, thereby preventing problems such as voiding, cracking or slipping in the concrete structure.

[0005] To achieve the above objectives, the embodiments of the present application adopt the following technical solutions:

[0006] An ultra-high performance concrete, comprising the following components in parts by weight:

[0007] 100 parts of metal oxide;

[0008] 3-5 parts of phosphate;

[0009] 10-15 parts of magnesium chloride;

[0010] 0.5-1 part of nano calcium carbonate;

[0011] 100-120 parts of fine aggregate;

[0012] 30-40 parts of three-dimensional fiber;

[0013] 200-230 parts of water.

[0014] During emergency repairs of special projects, ordinary UHPC has low early strength, while the use of early strength agents or early strength cement is prone to shrinkage and cracking. By adopting magnesium phosphate and magnesium oxychloride multi-component cementing system and reasonable proportion, early rapid hydration reaction is generated to generate reaction products mainly composed of magnesium phosphate salt and 5Mg(OH)2·MgCl2·8H2O (5 phases), which can give full play to the characteristics of ultra-early strength, shrinkage compensation and high bonding strength of the binder, so that UHPC has ultra-high hourly strength. At the same time, it effectively controls the volume change of UHPC caused by rapid chemical reaction, maintains good volume stability, reduces shrinkage cracks, and improves the bonding strength with external structures such as steel plates and old concrete, thereby preventing cracking, slippage or hollowing of concrete structures. Further, by adding nano calcium carbonate to UHPC, these particles are evenly distributed in the slurry, play a stable nucleus role, promote the generation of hydration products, form an interconnected crystalline network matrix, and further improve the development of UHPC's early strength. In addition, the incorporation of three-dimensional fibers greatly improves the bonding strength between a single fiber and the matrix, while the three-dimensional network composed of three-dimensional fibers further improves the tensile strength and toughness of UHPC, meeting the use requirements of high tensile and impact-resistant structures.

[0015] Preferably, the metal oxide is a mixture of dead-burned magnesium oxide and light-burned magnesium oxide, the weight ratio of the dead-burned magnesium oxide to the light-burned magnesium oxide is 2:8, and the Blaine specific surface area is 300-350m 2 / kg. Among them, the calcination temperature of dead-burned magnesium oxide is 1000-1200℃, the purity is greater than or equal to 98wt%, and the active magnesium oxide content is 20-30%. Among them, the calcination temperature of light-burned magnesium oxide is 600-800℃, the purity is greater than or equal to 95wt%, and the active magnesium oxide content is 80%-90%. The blending ratio of dead-burned magnesium oxide and light-burned magnesium oxide and the active magnesium oxide content are controlled to make the early reaction speed of UHPC moderate, which can ensure that UHPC has a half-hour service life and has ultra-high hourly strength. At the same time, the remaining magnesium oxide in the reaction slowly hydrates to form magnesium hydroxide with a slightly expanded volume, so that UHPC maintains good volume stability during its service life.

[0016] Preferably, the phosphate is ammonium dihydrogen phosphate, potassium dihydrogen phosphate or sodium dihydrogen phosphate, and the purity of the phosphate is greater than or equal to 99wt%.

[0017] Preferably, the magnesium chloride is anhydrous magnesium chloride with a fineness of 100-120 meshes, and the purity of the magnesium chloride is greater than or equal to 99wt%.

[0018] Preferably, the particle size of the nano calcium carbonate is in the range of 20 to 50 nm, and the purity of the nano calcium carbonate is greater than or equal to 98 wt %. The nano calcium carbonate particles of the fineness play a filling effect and a crystal nucleus effect, and can provide crystal nuclei for hydration products such as magnesium phosphate, 5Mg(OH)2·MgCl2·8H2O (5 phases) in the cementing system, accelerate their nucleation and growth speed, and promote the strength development of UHPC.

[0019] Preferably, the fine aggregate is composed of a mixture of quartz sands of different finenesses, wherein the proportion of quartz sands of different finenesses is: 40-60 mesh: 60-80 mesh: 80-120 mesh = 5:4:1, the SiO2 content of the fine aggregate is greater than or equal to 99wt%, and the bulk density is greater than or equal to 2000kg / m 3 The fine aggregate adopts a reasonable dense gradation to provide the most compact stacking skeleton for UHPC, which can reduce the amount of slurry while making the UHPC have good fluidity, strength and durability.

[0020] Preferably, the three-dimensional fiber is a spiral copper-plated steel fiber, the length of the three-dimensional fiber is 12±10% mm, the fiber diameter is 0.2±10% mm, the spiral diameter is 5 mm, the pitch is 10 mm, and the tensile strength of the three-dimensional fiber is not less than 2800 MPa. The three-dimensional fiber is in a single spiral space three-dimensional shape, which can increase its anchoring force and bonding force with the matrix, greatly improving the tensile and compressive properties of UHPC. At the same time, the surface of the three-dimensional fiber has a rust-proof copper coating, which can effectively prevent the steel fiber from being corroded by rust and increase the durability of UHPC.

[0021] The method for preparing UHPC as described above comprises the following steps:

[0022] 100 parts by weight of metal oxide, 3-5 parts by weight of phosphate, 0.5-1 parts by weight of nano calcium carbonate, and 100-120 parts by weight of fine aggregate are uniformly stirred to obtain a first mixture;

[0023] 10 to 15 parts by weight of magnesium chloride and 200 to 230 parts by weight of water are fully mixed and stirred until the magnesium chloride is completely dissolved to obtain a second mixture;

[0024] Mixing the first mixed material and the second mixed material, stirring evenly, to obtain a third mixed material;

[0025] 30 to 40 parts by weight of three-dimensional fibers are sieved into the third mixture through a 10 mm sieve, and the mixture is mixed evenly to obtain ultra-high performance concrete.

[0026] The preparation method of the metal oxide is as follows:

[0027] The magnesite ore is calcined at 1000-1200℃ for 3 hours to obtain dead-burned magnesium oxide. After grinding, the Blaine specific surface area is 300-350m 2 / kg, active magnesium oxide content 20-30%;

[0028] The magnesite ore is calcined at 600-800℃ for 2 hours to obtain light-burned magnesium oxide. After grinding, the Blaine specific surface area is 300-350m 2 / kg, control the active magnesium oxide content to 80% to 90%;

[0029] The heavy burned magnesium oxide and the light burned magnesium oxide are mixed in a mass ratio of 2:8 to obtain the metal oxide.

[0030] Compared with the prior art, this application has the following technical effects:

[0031] 1) This application uses metal oxides, phosphates and magnesium chloride in a reasonable ratio, especially metal oxides formed by mixing dead-burned magnesium oxide and light-burned magnesium oxide of different activities, so that UHPC can react quickly in the early stage, and accurately control the generated products to be mainly high-strength magnesium phosphate and 5Mg(OH)2·MgCl2·8H2O, which can give full play to the characteristics of ultra-early strength, no volume shrinkage and high bonding force of multi-component binders, so that UHPC has ultra-high hourly strength, and the 2h compressive strength can reach more than 80MPa, meeting the needs of fast repair and construction projects. At the same time, the UHPC matrix has no shrinkage, avoiding the common problems of chemical shrinkage caused by excessively fast reactions in the early stage and cracking, degassing, slipping, etc. caused by drying shrinkage in the later stage.

[0032] 2) The nano calcium carbonate described in this application can effectively improve the compactness and ultra-early strength performance of UHPC. It has a filling effect and a nucleation effect, improves the compactness of UHPC, accelerates the nucleation and staggered growth of hydration products, improves the interface transition zone, promotes the early strength development of UHPC, and further improves durability.

[0033] 3) The three-dimensional fiber described in the present application is a spiral copper-plated steel fiber, which is in a single spiral spatial three-dimensional shape, further increasing the anchoring force and bonding force with the high bonding matrix. The preferred fiber length, diameter, spiral diameter, and pitch greatly improve the tensile strength of UHPC, and the 28d ultimate tensile strength reaches more than 20MPa. At the same time, the reasonable spiral diameter and pitch also avoid problems such as uneven fiber dispersion and agglomeration. DETAILED DESCRIPTION

[0034] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below in conjunction with specific implementation methods.

[0035] The technical solutions in the embodiments of the present application are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.

[0036] The raw material purchasing information used in the following examples is as follows:

[0037] The preparation method of the metal oxide is as follows: calcining magnesite at 1000-1200°C for 3 hours to obtain dead-burned magnesium oxide, which has a Blaine specific surface area of ​​300-350 m 2 / kg, active magnesium oxide content 20-30%; calcining magnesia ore at 600-800℃ for 2 hours to obtain light-burned magnesium oxide, which has a Blaine specific surface area of ​​300-350m after grinding. 2 / kg, controlling the active magnesium oxide content to 80% to 90%; then mixing the dead-burned magnesium oxide and the light-burned magnesium oxide in a mass ratio of 2:8 to obtain the metal oxide used in this application.

[0038] Other raw materials and specifications shall be subject to those described in the specific embodiments.

[0039] The performance test methods in the following embodiments are as follows:

[0040] Determination of mechanical properties: in accordance with the relevant provisions of GB / T 31387 "Reactive Powder Concrete" and T / CBMF 37 "Basic Properties and Test Methods of Ultra-High Performance Concrete".

[0041] Determination of fluidity: in accordance with the relevant provisions of GB / T 50080 "Standard for test methods for properties of ordinary concrete mixtures".

[0042] Volume stability and durability: in accordance with the relevant provisions of GB / T 50082 "Standard for Test Methods for Long-term Performance and Durability of Ordinary Concrete".

[0043] The preparation methods of the ultra-early-strength high-tensile non-shrinkage UHPC in the following embodiments are as follows:

[0044] Step 1: Mix metal oxide, phosphate, nano calcium carbonate and fine aggregate to obtain a first mixture;

[0045] Step 2: fully mixing and stirring magnesium chloride and water until the magnesium chloride is completely dissolved to obtain a second mixture;

[0046] Step 3: Mix the first mixed material and the second mixed material, and stir them evenly to obtain a third mixed material;

[0047] Step 4: Sieve the three-dimensional fiber into the third mixture through a 10 mm sieve, mix evenly, and obtain ultra-early strength, high tensile strength, and shrinkage-free UHPC.

[0048] Example 1

[0049] An ultra-early-strength, high-tensile, shrinkage-free UHPC is composed of the following components in parts by weight: 100 parts of metal oxide, 3 parts of phosphate, 10 parts of magnesium chloride, 0.5 parts of nano calcium carbonate, 100 parts of fine aggregate, 30 parts of three-dimensional fibers and 200 parts of water.

[0050] The metal oxide is a mixture of dead-burned magnesium oxide and light-burned magnesium oxide, wherein the weight ratio of the dead-burned magnesium oxide to the light-burned magnesium oxide is 2:8, and the Blaine specific surface area is 300m 2 / kg, wherein the calcination temperature of heavy-burned magnesium oxide is 1000°C, the purity is 98wt%, the active magnesium oxide content is 20%, the calcination temperature of light-burned magnesium oxide is 600°C, the purity is 95wt%, and the active magnesium oxide content is 80%; the phosphate is ammonium dihydrogen phosphate, and the purity of the phosphate is 99wt%; the magnesium chloride is anhydrous magnesium chloride, the fineness is 100 mesh, and the purity is 99wt%; the particle size range of nano calcium carbonate is 20-50nm, and the purity is 98wt%; the fine aggregate is composed of a mixture of quartz sands of different finenesses, wherein the matching ratio of quartz sands of different finenesses is: 40-60 mesh: 60-80 mesh: 80-120 mesh = 5:4:1, the SiO2 content of the fine aggregate is 99wt%, and the bulk density is 2000kg / m 3 The three-dimensional fiber is a spiral copper-plated steel fiber with a fiber length of 12±10% mm, a fiber diameter of 0.2±10% mm, a spiral diameter of 5 mm, a pitch of 10 mm, and a tensile strength of 2800 MPa.

[0051] Example 2

[0052] An ultra-early-strength, high-tensile, shrinkage-free UHPC is composed of the following components in parts by weight: 100 parts of metal oxides, 5 parts of phosphates, 15 parts of magnesium chloride, 1 part of nano calcium carbonate, 120 parts of fine aggregates, 40 parts of three-dimensional fibers and 230 parts of water.

[0053] The metal oxide is a mixture of dead-burned magnesium oxide and light-burned magnesium oxide, the weight ratio of the dead-burned magnesium oxide to the light-burned magnesium oxide is 2:8, and the Blaine specific surface area is 350m 2 / kg, wherein the calcination temperature of heavy-burned magnesium oxide is 1200°C, the purity is 99wt%, the active magnesium oxide content is 30%, the calcination temperature of light-burned magnesium oxide is 800°C, the purity is 98wt%, and the active magnesium oxide content is 90%; the phosphate is potassium dihydrogen phosphate, and the purity of the phosphate is 99wt%; the magnesium chloride is anhydrous magnesium chloride, the fineness is 120 mesh, and the purity is 99wt%; the particle size range of nano calcium carbonate is 20-50nm, and the purity is 99wt%; the fine aggregate is composed of a mixture of quartz sands of different finenesses, wherein the matching ratio of quartz sands of different finenesses is: 40-60 mesh: 60-80 mesh: 80-120 mesh = 5:4:1, the SiO2 content of the fine aggregate is 99wt%, and the bulk density is 2100kg / m 3 The three-dimensional fiber is a spiral copper-plated steel fiber with a fiber length of 12±10% mm, a fiber diameter of 0.2±10% mm, a spiral diameter of 5 mm, a pitch of 10 mm, and a tensile strength of 2950 MPa.

[0054] Example 3

[0055] An ultra-early-strength, high-tensile, shrinkage-free UHPC is composed of the following components in parts by weight: 100 parts of metal oxide, 4 parts of phosphate, 13 parts of magnesium chloride, 0.8 parts of nano calcium carbonate, 110 parts of fine aggregate, 35 parts of three-dimensional fibers and 210 parts of water.

[0056] The metal oxide is a mixture of dead-burned magnesium oxide and light-burned magnesium oxide, the weight ratio of the dead-burned magnesium oxide to the light-burned magnesium oxide is 2:8, and the Blaine specific surface area is 330m 2 / kg, wherein the calcination temperature of heavy-burned magnesium oxide is 1100°C, the purity is 98wt%, the active magnesium oxide content is 25%, the calcination temperature of light-burned magnesium oxide is 700°C, the purity is 97wt%, and the active magnesium oxide content is 85%; the phosphate is sodium dihydrogen phosphate, and the purity of the phosphate is 99wt%; the magnesium chloride is anhydrous magnesium chloride, the fineness is 110 mesh, and the purity is 99wt%; the particle size range of nano calcium carbonate is 20-50nm, and the purity is 99wt%; the fine aggregate is composed of a mixture of quartz sands of different finenesses, wherein the matching ratio of quartz sands of different finenesses is: 40-60 mesh: 60-80 mesh: 80-120 mesh = 5:4:1, the SiO2 content of the fine aggregate is 99wt%, and the bulk density is 2200kg / m 3 The three-dimensional fiber is a spiral copper-plated steel fiber with a fiber length of 12±10% mm, a fiber diameter of 0.2±10% mm, a spiral diameter of 5 mm, a pitch of 10 mm, and a tensile strength of 2950 MPa.

[0057] The weight proportions of the raw materials of the ultra-early-strength, high-tensile, shrinkage-free UHPC described in Examples 1 to 3 are shown in Table 1.

[0058] The performance test results of Examples 1 to 3 are shown in Table 2.

[0059] Table 1:

[0060] Example Metal oxides Phosphate Magnesium chloride Nano Calcium Carbonate fine aggregate Three-dimensional fiber water 1 100 3 10 0.5 100 30 200 2 100 4 13 0.8 120 35 230 3 100 5 15 1 110 40 210

[0061] Table 2:

[0062]

[0063]

[0064] From the above data, it can be seen that the 2-hour ultimate tensile strength of the ultra-early-strength high-tensile shrink-free UHPC described in this application is above 9MPa, and the compressive strength is above 80MPa, which is significantly higher than the 2-hour compressive strength of "no more than 50MPa" in the prior art. Moreover, the drying shrinkage rate is only -25×10 -6 It is about 400×10 -6 The drying shrinkage rate is significantly reduced, reducing the risk of shrinkage cracking, improving the bonding strength with adjacent structures such as steel plates, sleeves, and old concrete, and improving the volume stability and reliability of the structure in UHPC construction applications. The UHPC described in this application has a 28d ultimate tensile strength of more than 20MPa, and a frost resistance grade of more than F800. It has the characteristics of ultra-early strength, no shrinkage, ultra-high tensile strength and good durability, and has excellent comprehensive performance. It is suitable for fast repair and construction projects with high tensile strength and high reliability requirements.

[0065] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0066] Obviously, those skilled in the art can make various changes and modifications to the invention without departing from the spirit and scope of the invention. Thus, if these modifications and variations of the invention fall within the scope of the claims of the invention and their equivalents, the invention is also intended to include these modifications and variations.

Claims

1. An ultra-high performance concrete, characterized in that: The ultra-high performance concrete is composed of the following components in parts by weight: 100 parts of metal oxide; 3-5 parts of phosphate; 10-15 parts of magnesium chloride; 0.5-1 part of nano calcium carbonate; 100-120 parts of fine aggregate; 30-40 parts of three-dimensional fiber; 200-230 parts of water.

2. The ultra-high performance concrete according to claim 1, characterized in that: The metal oxide is a mixture of dead-burned magnesium oxide and light-burned magnesium oxide, the weight ratio of the dead-burned magnesium oxide to the light-burned magnesium oxide is 2:8, and the Blaine specific surface area is 300-350m 2 / kg; wherein the calcination temperature of the heavy-burned magnesium oxide is 1000-1200°C, the purity is greater than or equal to 98wt%, and the active magnesium oxide content is 20-30%; the calcination temperature of the light-burned magnesium oxide is 600-800°C, the purity is greater than or equal to 95wt%, and the active magnesium oxide content is 80%-90%.

3. The ultra-high performance concrete according to claim 1, characterized in that: The phosphate is ammonium dihydrogen phosphate, potassium dihydrogen phosphate or sodium dihydrogen phosphate, and the purity of the phosphate is greater than or equal to 99wt%.

4. The ultra-high performance concrete according to claim 1, characterized in that: The magnesium chloride is anhydrous magnesium chloride with a fineness of 100-120 meshes, and the purity of the magnesium chloride is greater than or equal to 99wt%.

5. The ultra-high performance concrete according to claim 1, characterized in that: The particle size of the nano calcium carbonate is in the range of 20 to 50 nm, and the purity of the nano calcium carbonate is greater than or equal to 98 wt %.

6. The ultra-high performance concrete according to claim 1, characterized in that: The fine aggregate is composed of a mixture of quartz sands of different finenesses, wherein the proportion of quartz sands of different finenesses is: 40-60 mesh: 60-80 mesh: 80-120 mesh = 5:4:1, the SiO2 content of the fine aggregate is greater than or equal to 99wt%, and the bulk density is greater than or equal to 2000kg / m 3 .

7. The ultra-high performance concrete according to claim 1, characterized in that: The three-dimensional fiber is a spiral copper-plated steel fiber. The length of the three-dimensional fiber is 12±10% mm, the fiber diameter is 0.2±10% mm, the spiral diameter is 5 mm, the pitch is 10 mm, and the tensile strength of the three-dimensional fiber is greater than or equal to 2800 MPa.

8. The method for preparing ultra-high performance concrete according to any one of claims 1 to 7, characterized in that: The steps include: 100 parts by weight of metal oxide, 3 to 5 parts by weight of phosphate, 0.5 to 1 part by weight of nano calcium carbonate, and 100 to 120 parts by weight of fine aggregate are uniformly stirred to obtain a first mixture; 10 to 15 parts by weight of magnesium chloride and 200 to 230 parts by weight of water are fully mixed and stirred until the magnesium chloride is completely dissolved to obtain a second mixture; Mixing the first mixed material and the second mixed material, stirring evenly, to obtain a third mixed material; 30 to 40 parts by weight of three-dimensional fibers are sieved into the third mixture through a 10 mm sieve, and the mixture is mixed evenly to obtain ultra-high performance concrete.

9. The method for preparing ultra-high performance concrete according to claim 8, characterized in that: The preparation method of the metal oxide is as follows: The magnesite ore is calcined at 1000-1200℃ for 3 hours to obtain dead-burned magnesium oxide. After grinding, the Blaine specific surface area is 300-350m 2 / kg, active magnesium oxide content 20-30%; The magnesite ore is calcined at 600-800℃ for 2 hours to obtain light-burned magnesium oxide. After grinding, the Blaine specific surface area is 300-350m 2 / kg, control the active magnesium oxide content to 80% to 90%; The heavy burned magnesium oxide and the light burned magnesium oxide are mixed in a mass ratio of 2:8 to obtain the metal oxide.

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