Low-shrinkage recycled aggregate ultra-high performance concrete, and preparation method and application thereof

Abstract

The application belongs to the technical field of ultra-high performance concrete, and particularly relates to a low-shrinkage recycled aggregate ultra-high performance concrete as well as a preparation method and application thereof. The low-shrinkage recycled aggregate ultra-high performance concrete is composed of the following raw materials in parts by weight: Portland cement 840-860 parts, silica fume 140-160 parts, natural river sand fine aggregate 320-480 parts, recycled fine aggregate 320-480 parts, natural basalt coarse aggregate 400-560 parts, recycled coarse aggregate 240-400 parts, water reducing agent 18-22 parts, carbon fiber 40-60 parts, steel fiber 140-160 parts, and water 420-640 parts. The replacement rate of the recycled fine aggregate to the natural river sand fine aggregate is 40%-60%, and the replacement rate of the recycled coarse aggregate to the natural basalt coarse aggregate is 30%-50%. The ultra-high performance concrete prepared by the application has good fluidity, good construction performance, low shrinkage, high strength, and high durability. The recycled aggregate used in the application can save energy and realize the recycling of waste materials. The method for processing the aggregate is energy-saving and emission-reducing, and is suitable for large-scale popularization and application.

Description

Technical Field

[0001] The present invention belongs to the technical field of ultra-high performance concrete, and in particular relates to a low-shrinkage recycled aggregate ultra-high performance concrete and a preparation method and application thereof. Background Art

[0002] Concrete has become the most widely used civil engineering material due to its excellent performance. Ultra-high performance concrete uses fly ash, slag, limestone powder, metakaolin and other industrial waste materials as admixtures, and is used with cement to improve performance while reducing cement usage. Compared to ordinary concrete, it has the advantages of higher strength, higher toughness, lower porosity, and greater environmental friendliness. However, with the continuous use of Earth's resources and the continuous development of the concrete industry, natural aggregates are constantly decreasing, and waste concrete materials are accumulating in large quantities. How to reduce the use of natural aggregates and how to reuse waste concrete have become hot research topics today.

[0003] Recycled aggregate ultra-high performance concrete (UHPC) is made by replacing natural sand with recycled fine aggregate. The difference between recycled aggregate UHPC and conventional UHPC lies in the aggregate used. By utilizing recycled aggregate from waste concrete and processing it, the use of recycled aggregate in UHPC reduces the use of natural aggregate, aligning with today's sustainable development strategies.

[0004] Patent application publication number CN 115490448 A discloses a method for reducing the autogenous shrinkage of ultra-high performance concrete, high-strength concrete, and high-strength mortar. Waste fired ceramics are crushed into waste ceramic regenerated sand, which is used as all or part of the fine aggregate for preparing ultra-high performance concrete, high-strength concrete, and high-strength mortar. However, the autogenous shrinkage of the waste ceramic regenerated sand is more than 50% after 7 days. Patent application publication number CN 108285310 A discloses an ultra-high performance concrete (UHPC) prepared using recycled fine aggregate from waste concrete and a preparation method thereof. The raw materials are: 570-630 parts of ordinary Portland cement, 270-320 parts of fly ash, 85-115 parts of silica fume, 25-35 parts of an expansive agent, 300-800 parts of recycled fine aggregate, 300-800 parts of river sand, 180-220 parts of microfilament steel fiber, 18-22 parts of a polycarboxylate superplasticizer, and 150-180 parts of water. While the recycled fine aggregate is used in varying proportions to replace more expensive natural fine aggregate, the concrete demonstrates improved compressive and flexural strengths, but its shrinkage properties have not been verified. Patent application publication number CN107235684A discloses a recycled fine aggregate ultra-high performance concrete and its use method. The recycled fine aggregate belongs to Class I recycled fine aggregate, with a particle size range of 0.15 to 1.18 mm or 0.15 to 4.75 mm. The recycled fine aggregate replaces natural sand, but does not replace natural coarse aggregate. The preparation method is complex and requires autoclaving. As can be seen, the recycled aggregate ultra-high performance concrete and its preparation method cannot achieve dense packing of concrete raw materials and also suffer from the disadvantage of large shrinkage. The workability and mechanical properties of the ultra-high performance concrete after the recycled aggregate is replaced are significantly altered, failing to meet the development requirements and application of concrete technology. Summary of the Invention

[0005] The purpose of the present invention is to provide a recycled aggregate ultra-high performance concrete and a preparation method and application thereof, so as to overcome the shortcomings of the existing technology. The recycled aggregate is pretreated and the pretreated recycled aggregate partially replaces the natural aggregate. The prepared recycled aggregate ultra-high performance concrete not only has good fluidity, good construction performance, low shrinkage, high strength and high durability, but also the recycled aggregate used can save energy and realize the recycling of waste. The method of treating aggregate saves energy and reduces emissions, and is suitable for large-scale promotion and application.

[0006] In order to achieve the above object, the technical solution of the present invention is:

[0007] In one aspect, the present invention provides a low-shrinkage recycled aggregate ultra-high performance concrete, comprising the following raw materials in parts by weight:

[0008] 840-860 parts of Portland cement, 140-160 parts of silica fume, 320-480 parts of natural river sand fine aggregate, 320-480 parts of recycled fine aggregate, 400-560 parts of natural basalt coarse aggregate, 240-400 parts of recycled coarse aggregate, 18-22 parts of water reducer, 40-60 parts of carbon fiber, 140-160 parts of steel fiber, and 420-640 parts of water.

[0009] The low-shrinkage recycled aggregate ultra-high performance concrete prepared by the present invention is easy to construct, has low shrinkage (about 10% lower than that of ordinary ultra-high performance concrete), and high strength (28-day compressive strength can reach 146 MPa, splitting tensile strength can reach 17 MPa, and elastic modulus can reach 45 MPa). In addition, the replacement rate of the recycled aggregate used to replace natural fine aggregate is 40% to 60%, and at this replacement rate, the impact on UHPC is relatively small, and the basic mechanical properties and working performance can be met.

[0010] The raw materials used in the present invention are obtained by crushing and screening concrete samples, and the aggregate in the concrete samples is a mixture of natural river sand fine aggregate and natural basalt. The present invention first calculates the particle size of natural fine aggregate river sand, natural basalt coarse aggregate, recycled fine aggregate, and recycled coarse aggregate through the closest packing density theory, optimizes the content of each particle size segment of each natural aggregate (natural fine aggregate river sand, natural basalt coarse aggregate) and recycled aggregate (recycled fine aggregate, recycled coarse aggregate) in the low shrinkage recycled aggregate ultra-high performance concrete raw material, and then obtains various combinations of each particle size and content of natural fine aggregate river sand, natural basalt coarse aggregate, recycled fine aggregate and recycled coarse aggregate as various particle sizes by screening, so that on the one hand, it plays a skeleton supporting role, and on the other hand, it optimizes the particle grading so that the components are closely stacked, and the gaps formed between the large particle size and the large particle size are filled by the smaller particle size, and the smaller particle size is filled by the aggregate of the smaller particle size, thereby reducing the porosity of the concrete and making its strength meet the requirements. For traditional ultra-high performance concrete, which does not contain coarse aggregate, the purpose of adding coarse aggregate is to reduce its shrinkage value because the shrinkage of coarse aggregate itself is negligible.

[0011] The calculation formula for the relative content of each particle size segment of the aggregate used is as follows:

[0012]

[0013] Where: P Di The particle size is smaller than D i The volume fraction of particles is %; q is the particle size distribution modulus; D max and D min are the maximum and minimum particle sizes of aggregate used in the preparation of low shrinkage recycled aggregate ultra-high performance concrete, μm.

[0014] The silica fume used as an admixture can reduce the amount of Portland cement used, thereby reducing CO2 emissions and saving energy.

[0015] The water reducer used is a polycarboxylic acid water reducer with a water reduction rate greater than 25%, which makes the cementitious material particles evenly dispersed, improves workability, increases fluidity, and reduces water consumption, thereby improving the mechanical properties and durability of the low-shrinkage recycled aggregate ultra-high performance concrete material.

[0016] The steel fibers used are steel fibers with a tensile strength greater than 25 GPa and a length of 8-12 mm; the carbon fibers are carbon fibers with a tensile strength greater than 30 GPa and a length of 0.18-0.22 mm.

[0017] Through the synergistic effect of the above raw material components, the prepared low-shrinkage recycled aggregate ultra-high performance concrete not only has good fluidity, good construction performance, low shrinkage, high strength and high durability, but also the recycled aggregate used can save energy, realize the recycling of waste, and the method of processing aggregates saves energy and reduces emissions.

[0018] In a second aspect, the present invention provides a method for preparing the low-shrinkage recycled aggregate ultra-high performance concrete according to the first aspect, comprising the following steps:

[0019] S1, adding a water reducer and carbon fiber to water and mixing evenly to obtain a first mixture;

[0020] S2, evenly mixing Portland cement and silica fume and adding them to the first mixture in S1 in batches, mixing evenly to obtain a second mixture;

[0021] S3, adding steel fiber to the second mixture in S2, mixing evenly, to obtain a third mixture;

[0022] S4, mixing the natural river sand fine aggregate and the recycled fine aggregate evenly, and adding the mixture to the third mixture in S3, mixing evenly, to obtain a fourth mixture;

[0023] S5, adding natural basalt coarse aggregate evenly to the fourth mixture in S4, mixing evenly, to obtain a fifth mixture;

[0024] S6. Evenly add the recycled coarse aggregate into the fifth mixture in S5, mix well, and obtain low shrinkage ultra-high performance concrete.

[0025] The raw material ratio and preparation method of the present invention follow the maximum packing density theory, and the different particle sizes of the constituent materials are formed into the most dense stacking in the optimal ratio, and are evenly mixed to obtain a low-shrinkage ultra-high performance concrete material. The carbon fiber is first added to the water, which is conducive to its better dispersion in the concrete and prevents the formation of agglomerates. Considering that the surface of the recycled coarse aggregate is relatively fragile relative to the natural aggregate, and the collision and friction between the two aggregates damage the recycled aggregate, the recycled coarse aggregate is added at the end to buffer the collision between the recycled coarse aggregate and the natural basalt aggregate, thereby reducing the impact on the mechanical properties and shrinkage properties of the prepared low-shrinkage ultra-high performance concrete material.

[0026] In order to further improve the replacement effect of recycled aggregates (recycled fine aggregate, recycled coarse aggregate) on natural aggregates (natural fine aggregate river sand, natural basalt coarse aggregate) and the coordination effect between the various components of the raw materials, this application pre-treats the recycled aggregates before re-mixing, namely, crushing, screening, wet treatment, acid treatment (recycled coarse aggregate) and carbonization treatment, so that the pre-treated recycled aggregates can meet the requirements of concrete working performance, mechanical properties and shrinkage performance.

[0027] In a third aspect, the present invention provides a use of the low-shrinkage recycled aggregate ultra-high performance concrete according to the first aspect in preparing ultra-high performance concrete with low shrinkage.

[0028] Beneficial effects of the present invention:

[0029] (1) The low-shrinkage recycled aggregate ultra-high performance concrete material involved in the technical solution of the present invention has a fluidity of about 220 mm, indicating good fluidity and reducing the difficulty of construction of the ultra-high performance concrete material.

[0030] (2) The technical solution of the present invention relates to a low-shrinkage recycled aggregate ultra-high performance concrete material with a 28-day compressive strength of up to 146 MPa, a splitting tensile strength of up to 17 MPa, and an elastic modulus of up to 45 MPa. It exhibits excellent mechanical properties and can significantly improve the material's safety performance. Its shrinkage is approximately 10% lower than that of ordinary ultra-high performance concrete, reducing the risk of cracking caused by concrete shrinkage.

[0031] (3) The technical solution of the present invention relates to a recycled aggregate ultra-high performance concrete material, in which silica fume from industrial waste is used as the cementitious material, thereby reducing the amount of cement used and allowing industrial waste to be reused, thereby saving energy and protecting the environment.

[0032] (4) The technical solution of the present invention relates to a recycled aggregate ultra-high performance concrete material, in which recycled aggregate partially replaces natural aggregate, thereby reusing waste aggregate generated by demolished buildings without reducing its mechanical properties and working performance, reducing the use of natural aggregate, and reflecting the country's current sustainable development strategy.

[0033] (5) The technical solution of the present invention involves a method for processing recycled aggregates, which saves energy and reduces emissions. The method of using CO2 to process recycled aggregates saves energy and reduces emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a flow chart for preparing low-shrinkage recycled aggregate ultra-high performance concrete according to Example 1 of the present invention. DETAILED DESCRIPTION

[0035] To address the problem of reduced mechanical and workability of ultra-high performance concrete produced by replacing natural aggregate with recycled aggregate, and the inability to obtain ultra-high performance concrete with low shrinkage, recycled aggregate, good fluidity, good workability, low shrinkage, high strength, high durability, and waste recycling, the present invention provides ultra-high performance concrete with low shrinkage, recycled aggregate, and its preparation method and application.

[0036] A typical embodiment of the present invention provides a low-shrinkage recycled aggregate ultra-high performance concrete, which is composed of the following raw materials in parts by weight:

[0037] 840-860 parts of Portland cement, 140-160 parts of silica fume, 320-480 parts of natural river sand fine aggregate, 320-480 parts of recycled fine aggregate, 400-560 parts of natural basalt coarse aggregate, 240-400 parts of recycled coarse aggregate, 18-22 parts of water reducer, 40-60 parts of carbon fiber, 140-160 parts of steel fiber, and 420-640 parts of water.

[0038] In some examples of this embodiment, the raw materials are composed of the following parts by weight: 850 parts of Portland cement, 150 parts of silica fume, 320-480 parts of natural river sand fine aggregate, 320-480 parts of recycled fine aggregate, 400-560 parts of natural basalt coarse aggregate, 240-400 parts of recycled coarse aggregate, 20 parts of water reducer, 50 parts of carbon fiber, 150 parts of steel fiber, and 440 parts of water;

[0039] Preferably, the Portland cement is Portland cement with a PO of not less than 42.5; and the SiO2 content in the silica fume is not less than 92 wt.%.

[0040] The water reducer is a polycarboxylate water reducer with a water reduction rate greater than 25%;

[0041] The steel fiber has a tensile strength greater than 25 GPa and a length of 8 to 12 mm;

[0042] The carbon fiber has a tensile strength greater than 30 GPa and a length of 0.18 to 0.22 mm.

[0043] In some examples of this embodiment, the particle size of the natural river sand fine aggregate and the particle size of the recycled fine aggregate are both 0.155 to 2.36 mm;

[0044] The particle size of the natural basalt coarse aggregate and the particle size of the recycled coarse aggregate are both 2.36 to 8.36 mm. In some examples of this embodiment, the composition of the natural river sand fine aggregate is as follows:

[0045] 80-120 parts of natural river sand fine aggregate with a particle size of 0.155-0.315 mm;

[0046] 112-168 parts of natural river sand fine aggregate with a particle size of 0.315-1.25 mm;

[0047] 128-192 parts of natural river sand fine aggregate with a particle size of 1.25-2.36 mm;

[0048] Preferably, the composition of the recycled fine aggregate is as follows:

[0049] 80-120 parts of recycled fine aggregate with a particle size of 0.155-0.315 mm;

[0050] 112-168 parts of recycled fine aggregate with a particle size of 0.315-1.25 mm;

[0051] 128-192 parts of recycled fine aggregate with a particle size of 1.25-2.36 mm;

[0052] Preferably, the composition of the natural basalt coarse aggregate is as follows:

[0053] 100-140 parts of natural basalt coarse aggregate with a particle size of 2.36-4.75 mm;

[0054] 140-196 parts of natural basalt coarse aggregate with a particle size of 4.75-6.12 mm;

[0055] 160-224 parts of natural basalt coarse aggregate with a particle size of 6.12-8.36 mm;

[0056] Preferably, the composition of the recycled coarse aggregate is as follows:

[0057] 60-100 parts of recycled coarse aggregate with a particle size of 2.36-4.75 mm;

[0058] 84-140 parts of recycled coarse aggregate with a particle size of 4.75-6.12 mm;

[0059] 96-160 parts of recycled coarse aggregate with a particle size of 6.12-8.36 mm.

[0060] In some examples of this embodiment, the composition of the natural river sand fine aggregate is as follows:

[0061] 120 parts of natural river sand fine aggregate with a particle size of 0.155-0.315 mm;

[0062] 168 parts of natural river sand fine aggregate with a particle size of 0.315 to 1.25 mm;

[0063] 192 parts of natural river sand fine aggregate with a particle size of 1.25 to 2.36 mm;

[0064] Preferably, the composition of the recycled fine aggregate is as follows:

[0065] 80 parts of recycled fine aggregate with a particle size of 0.155-0.315 mm;

[0066] 112 parts of recycled fine aggregate with a particle size of 0.315 to 1.25 mm;

[0067] 128 parts of recycled fine aggregate with a particle size of 1.25 to 2.36 mm;

[0068] Preferably, the composition of the natural basalt coarse aggregate is as follows:

[0069] 140 parts of natural basalt coarse aggregate with a particle size of 2.36 to 4.75 mm;

[0070] 196 parts of natural basalt coarse aggregate with a particle size of 4.75 to 6.12 mm;

[0071] 224 parts of natural basalt coarse aggregate with a particle size of 6.12 to 8.36 mm;

[0072] Preferably, the composition of the recycled coarse aggregate is as follows:

[0073] 60 parts of recycled coarse aggregate with a particle size of 2.36 to 4.75 mm;

[0074] 84 parts of recycled coarse aggregate with a particle size of 4.75 to 6.12 mm;

[0075] 96 parts of recycled coarse aggregate with a particle size of 6.12 to 8.36 mm.

[0076] In some examples of this embodiment, the composition of the natural river sand fine aggregate is as follows:

[0077] 100 parts of natural river sand fine aggregate with a particle size of 0.155-0.315 mm;

[0078] 140 parts of natural river sand fine aggregate with a particle size of 0.315-1.25 mm;

[0079] 160 parts of natural river sand fine aggregate with a particle size of 1.25 to 2.36 mm;

[0080] Preferably, the composition of the recycled fine aggregate is as follows:

[0081] 100 parts of recycled fine aggregate with a particle size of 0.155 to 0.315 mm;

[0082] 140 parts of recycled fine aggregate with a particle size of 0.315 to 1.25 mm;

[0083] 160 parts of recycled fine aggregate with a particle size of 1.25 to 2.36 mm;

[0084] Preferably, the composition of the natural basalt coarse aggregate is as follows:

[0085] 120 parts of natural basalt coarse aggregate with a particle size of 2.36 to 4.75 mm;

[0086] 168 parts of natural basalt coarse aggregate with a particle size of 4.75 to 6.12 mm;

[0087] 192 parts of natural basalt coarse aggregate with a particle size of 6.12 to 8.36 mm;

[0088] Preferably, the composition of the recycled coarse aggregate is as follows:

[0089] 80 parts of recycled coarse aggregate with a particle size of 2.36 to 4.75 mm;

[0090] 112 parts of recycled coarse aggregate with a particle size of 4.75 to 6.12 mm;

[0091] 128 parts of recycled coarse aggregate with a particle size of 6.12 to 8.36 mm.

[0092] In some examples of this embodiment, the composition of the natural river sand fine aggregate is as follows:

[0093] 80 parts of natural river sand fine aggregate with a particle size of 0.155-0.315 mm;

[0094] 112 parts of natural river sand fine aggregate with a particle size of 0.315 to 1.25 mm;

[0095] 128 parts of natural river sand fine aggregate with a particle size of 1.25 to 2.36 mm;

[0096] Preferably, the composition of the recycled fine aggregate is as follows:

[0097] 120 parts of recycled fine aggregate with a particle size of 0.155 to 0.315 mm;

[0098] 168 parts of recycled fine aggregate with a particle size of 0.315 to 1.25 mm;

[0099] 192 parts of recycled fine aggregate with a particle size of 1.25 to 2.36 mm;

[0100] Preferably, the composition of the natural basalt coarse aggregate is as follows:

[0101] 100 parts of natural basalt coarse aggregate with a particle size of 2.36 to 4.75 mm;

[0102] 140 parts of natural basalt coarse aggregate with a particle size of 4.75 to 6.12 mm;

[0103] 160 parts of natural basalt coarse aggregate with a particle size of 6.12 to 8.36 mm;

[0104] Preferably, the composition of the recycled coarse aggregate is as follows:

[0105] 100 parts of recycled coarse aggregate with a particle size of 2.36 to 4.75 mm;

[0106] 140 parts of recycled coarse aggregate with a particle size of 4.75 to 6.12 mm;

[0107] 160 parts of recycled coarse aggregate with a particle size of 6.12 to 8.36 mm.

[0108] Another typical embodiment of the present invention provides a method for preparing the low-shrinkage recycled aggregate ultra-high performance concrete in the first typical embodiment, comprising the following steps:

[0109] S1, adding a water reducer and carbon fiber to water and mixing evenly to obtain a first mixture;

[0110] S2, evenly mixing Portland cement and silica fume and adding them to the first mixture in S1 in batches, mixing evenly to obtain a second mixture;

[0111] S3, adding steel fiber to the second mixture in S2, mixing evenly, to obtain a third mixture;

[0112] S4, mixing the natural river sand fine aggregate and the recycled fine aggregate evenly, and adding the mixture to the third mixture in S3, mixing evenly, to obtain a fourth mixture;

[0113] S5, adding natural basalt coarse aggregate evenly to the fourth mixture in S4, mixing evenly, to obtain a fifth mixture;

[0114] S6. Evenly add the recycled coarse aggregate into the fifth mixture in S5, mix well, and obtain low shrinkage ultra-high performance concrete.

[0115] In some examples of this embodiment, in S4, the recycled fine aggregate is pretreated, and the specific processing steps are as follows:

[0116] (1) Crushing and screening concrete to obtain crushed recycled fine aggregate;

[0117] (2) mixing the recycled fine aggregate in step (1) with water for humidification treatment, and controlling the moisture content of the recycled fine aggregate;

[0118] (3) carbonizing the recycled fine aggregate after the humidification treatment in step (2) to obtain recycled fine aggregate with a particle size of 0.155 to 2.36 mm;

[0119] Alternatively, in S5, the recycled coarse aggregate is pretreated, and the specific processing steps are as follows:

[0120] (1) crushing and screening concrete to obtain crushed recycled coarse aggregate;

[0121] (2) mixing the recycled coarse aggregate in step (1) with water for humidification treatment, and controlling the moisture content of the recycled coarse aggregate;

[0122] (3) acid-treating, washing, and drying the recycled coarse aggregate after the humidification treatment in step (2) to obtain acid-treated recycled coarse aggregate;

[0123] (4) carbonizing the recycled coarse aggregate after the acid treatment in step (3) to obtain recycled coarse aggregate with a particle size of 2.36 to 8.36 mm;

[0124] Preferably, during the pretreatment of the recycled fine aggregate or recycled coarse aggregate, the carbonization treatment conditions are: 20-30°C, relative humidity 50-70%, and air pressure 0.5-1 mPa for 20-24 hours;

[0125] Preferably, during the pretreatment of the recycled fine aggregate or recycled coarse aggregate, after the humidification treatment, the moisture content of the recycled fine aggregate is 9-12 wt.%, and the moisture content of the recycled coarse aggregate is 2-5 wt.%;

[0126] Preferably, during the pretreatment of the recycled coarse aggregate, the acid treatment is performed by using 0.12-2 mol / L dilute hydrochloric acid for 20-24 hours.

[0127] Another typical embodiment of the present invention provides the use of the low-shrinkage recycled aggregate ultra-high performance concrete in the first typical embodiment in the preparation of ultra-high performance concrete with low shrinkage.

[0128] The present invention will be further described in detail below with reference to specific embodiments:

[0129] In the following examples, polycarboxylate water-reducing agent was purchased from Shandong Boke Chemical Co., Ltd., and retarder was purchased from Shanxi Zhengda Longqi Trading Co., Ltd.

[0130] Example 1

[0131] A low-shrinkage recycled aggregate ultra-high performance concrete material comprises the following raw materials in parts by weight: (recycled coarse aggregate replaces 30%, recycled fine aggregate replaces 40%)

[0132] 120 parts of natural river sand fine aggregate with a particle size of 0.155-0.315 mm;

[0133] 168 parts of natural river sand fine aggregate with a particle size of 0.315-1.25 mm;

[0134] 192 parts of natural river sand fine aggregate with a particle size of 1.25 to 2.36 mm;

[0135] 80 parts of recycled fine aggregate with a particle size of 0.155-0.315 mm;

[0136] 112 parts of recycled fine aggregate with a particle size of 0.315 to 1.25 mm;

[0137] 128 parts of recycled fine aggregate with a particle size of 1.25 to 2.36 mm;

[0138] 140 parts of natural basalt coarse aggregate with a particle size of 2.36 to 4.75 mm;

[0139] 196 parts of natural basalt coarse aggregate with a particle size of 4.75 to 6.12 mm;

[0140] 224 parts of natural basalt coarse aggregate with a particle size of 6.12 to 8.36 mm;

[0141] 60 parts of recycled coarse aggregate with a particle size of 2.36 to 4.75 mm;

[0142] 84 parts of recycled coarse aggregate with a particle size of 4.75 to 6.12 mm;

[0143] 96 parts of recycled coarse aggregate with a particle size of 6.12 to 8.36 mm;

[0144] 150 parts of silica fume;

[0145] Water-binder ratio 0.185;

[0146] 20 parts of polycarboxylate water reducer;

[0147] 150 parts of 8-12mm steel fiber;

[0148] 50 parts of 0.18-0.22mm nanofibers;

[0149] PO 42.5 cement 850 parts.

[0150] The method for preparing the above-mentioned low shrinkage recycled aggregate ultra-high performance concrete material is prepared according to the following steps:

[0151] S1. Mix the polycarboxylate water reducer, carbon fiber and water in a blender for 1 min to make the water reducer and carbon fiber more evenly dispersed;

[0152] S2, evenly mix Portland cement and silica fume and add them into S1 mixture in batches, mix and stir for 2 minutes;

[0153] S3, add steel fiber to S2 mixture and mix and stir for 2 minutes;

[0154] S4. Mix the natural river sand fine aggregate and the recycled fine aggregate of the laboratory concrete sample and stir them evenly, then add them to the S3 mixture and mix and stir for 1 minute;

[0155] S5. Add natural basalt coarse aggregate evenly into the S4 mixture and mix for 1 minute.

[0156] S6. Evenly add the recycled coarse aggregate of the laboratory concrete sample into the S5 mixture, mix and stir for 3 minutes to obtain a low shrinkage ultra-high performance concrete material.

[0157] Among them, in S4, the recycled fine aggregate is pretreated, and the specific processing steps are as follows:

[0158] (1) The concrete sample is crushed and mechanically ground to make the recycled fine aggregates collide and rub against each other to remove the surface mortar, thereby improving the particle shape of the recycled fine aggregates;

[0159] (2) The recycled fine aggregate in step (1) is mixed with water for humidification treatment, and the moisture content of the recycled fine aggregate is controlled; since the recycled aggregate has a high water absorption capacity, the humidification treatment is beneficial to ensuring its working performance, and can also be used for later internal curing of the concrete, which can reduce the shrinkage of the concrete. The moisture content of the recycled fine aggregate is controlled between 9% and 12%. The recycled aggregate within this moisture content control range can meet both the working performance and the mechanical and shrinkage performance requirements.

[0160] (3) The recycled fine aggregate subjected to the humidification treatment in step (2) is carbonized, and the substances generated by the reaction gradually precipitate on the surface of the recycled fine aggregate, thereby reinforcing and repairing the recycled fine aggregate to a recycled fine aggregate with a particle size of 0.155 to 2.36 mm.

[0161] Among them, in S5, the recycled coarse aggregate is pretreated, and the specific processing steps are as follows:

[0162] (1) The laboratory concrete samples were crushed and mechanically ground to make the recycled coarse aggregates collide and rub against each other to remove the surface mortar, thereby improving the particle shape of the recycled coarse aggregates;

[0163] (2) The recycled coarse aggregate in step (1) is mixed with water for humidification treatment, and the moisture content of the recycled coarse aggregate is controlled; since the recycled aggregate has a high water absorption capacity, the humidification treatment is beneficial to ensuring its working performance, and can also perform later internal curing of the concrete, which can reduce the shrinkage of the concrete. The moisture content of the recycled coarse aggregate is controlled between 2-5wt.%. The recycled aggregate within this moisture content control range can meet both the working performance and the mechanical and shrinkage performance requirements.

[0164] (3) soaking the recycled coarse aggregate treated with humidification in step (2) in a dilute hydrochloric acid solution with a concentration of 0.12 mol / L for 24 h, rinsing with distilled water after soaking to remove residual hydrochloric acid on the surface, and then drying to remove the old mortar layer on the surface of the particles;

[0165] (4) The recycled coarse aggregate treated with acid in step (3) is carbonized at 20° C., 50% relative humidity, and 0.5 MPa air pressure for 24 h. The substances generated by the reaction will gradually precipitate on the surface of the recycled coarse aggregate, thereby reinforcing and repairing the recycled coarse aggregate to obtain recycled coarse aggregate with a particle size of 2.36 to 8.36 mm.

[0166] Example 2

[0167] The difference from Example 1 is that the ratio of recycled aggregate replacing natural aggregate is different; other raw material proportions and preparation methods are exactly the same as those in Example 1.

[0168] The low shrinkage recycled aggregate ultra-high performance concrete material includes the following raw materials in parts by weight: (recycled coarse aggregate replaces 40%, recycled fine aggregate replaces 50%)

[0169] 100 parts of natural river sand fine aggregate with a particle size of 0.155-0.315 mm;

[0170] 140 parts of natural river sand fine aggregate with a particle size of 0.315-1.25 mm;

[0171] 160 parts of natural river sand fine aggregate with a particle size of 1.25 to 2.36 mm;

[0172] 100 parts of recycled fine aggregate with a particle size of 0.155 to 0.315 mm;

[0173] 140 parts of recycled fine aggregate with a particle size of 0.315 to 1.25 mm;

[0174] 160 parts of laboratory recycled fine aggregate with a particle size of 1.25 to 2.36 mm;

[0175] 120 parts of natural basalt coarse aggregate with a particle size of 2.36 to 4.75 mm;

[0176] 168 parts of natural basalt coarse aggregate with a particle size of 4.75 to 6.12 mm;

[0177] 192 parts of natural basalt coarse aggregate with a particle size of 6.12 to 8.36 mm;

[0178] 80 parts of recycled coarse aggregate with a particle size of 2.36 to 4.75 mm;

[0179] 112 parts of recycled coarse aggregate with a particle size of 4.75 to 6.12 mm;

[0180] 128 parts of recycled coarse aggregate with a particle size of 6.12 to 8.36 mm;

[0181] 150 parts of silica fume;

[0182] Water-binder ratio 0.185;

[0183] 20 parts of polycarboxylate water reducer;

[0184] 150 parts of 8-12mm steel fiber;

[0185] 50 parts of 0.18-0.22mm nanofibers;

[0186] PO 42.5 cement 850 parts.

[0187] Example 3

[0188] The difference from Example 1 is that the ratio of recycled aggregate replacing natural aggregate is different; other raw material proportions and preparation methods are exactly the same as those in Example 1.

[0189] Low shrinkage recycled aggregate ultra-high performance concrete material, comprising the following raw materials in parts by weight: (recycled coarse aggregate replaces 50%, recycled fine aggregate replaces 60%)

[0190] 80 parts of natural river sand fine aggregate with a particle size of 0.155-0.315 mm;

[0191] 112 parts of natural river sand fine aggregate with a particle size of 0.315-1.25 mm;

[0192] 128 parts of natural river sand fine aggregate with a particle size of 1.25 to 2.36 mm;

[0193] 120 parts of recycled fine aggregate with a particle size of 0.155 to 0.315 mm;

[0194] 168 parts of recycled fine aggregate with a particle size of 0.315 to 1.25 mm;

[0195] 192 parts of recycled fine aggregate with a particle size of 1.25 to 2.36 mm;

[0196] 100 parts of natural basalt coarse aggregate with a particle size of 2.36 to 4.75 mm;

[0197] 140 parts of natural basalt coarse aggregate with a particle size of 4.75 to 6.12 mm;

[0198] 160 parts of natural basalt coarse aggregate with a particle size of 6.12 to 8.36 mm;

[0199] 100 parts of recycled coarse aggregate with a particle size of 2.36 to 4.75 mm;

[0200] 140 parts of recycled coarse aggregate with a particle size of 4.75 to 6.12 mm;

[0201] 160 parts of recycled coarse aggregate with a particle size of 6.12 to 8.36 mm;

[0202] 150 parts of silica fume;

[0203] Water-binder ratio 0.185;

[0204] 20 parts of polycarboxylate water reducer;

[0205] 150 parts of 8-12mm steel fiber;

[0206] 50 parts of 0.18-0.22mm nanofibers;

[0207] PO 42.5 cement 850 parts.

[0208] Comparative Example 1

[0209] Low shrinkage recycled aggregate ultra-high performance concrete material, including the following raw materials in parts by weight:

[0210] 100 parts of natural river sand fine aggregate with a particle size of 0.155-0.315 mm;

[0211] 140 parts of natural river sand fine aggregate with a particle size of 0.315-1.25 mm;

[0212] 160 parts of natural river sand fine aggregate with a particle size of 1.25 to 2.36 mm;

[0213] 100 parts of recycled fine aggregate with a particle size of 0.155 to 0.315 mm;

[0214] 140 parts of recycled fine aggregate with a particle size of 0.315 to 1.25 mm;

[0215] 160 parts of laboratory recycled fine aggregate with a particle size of 1.25 to 2.36 mm;

[0216] 120 parts of natural basalt coarse aggregate with a particle size of 2.36 to 4.75 mm;

[0217] 168 parts of natural basalt coarse aggregate with a particle size of 4.75 to 6.12 mm;

[0218] 192 parts of natural basalt coarse aggregate with a particle size of 6.12 to 8.36 mm;

[0219] 80 parts of recycled coarse aggregate with a particle size of 2.36 to 4.75 mm;

[0220] 112 parts of recycled coarse aggregate with a particle size of 4.75 to 6.12 mm;

[0221] 128 parts of recycled coarse aggregate with a particle size of 6.12 to 8.36 mm;

[0222] 150 parts of silica fume;

[0223] Water-binder ratio 0.185;

[0224] 20 parts of polycarboxylate water reducer;

[0225] 150 parts of 8-12mm steel fiber;

[0226] 50 parts of 0.18-0.22mm nanofibers;

[0227] PO 42.5 cement 850 parts.

[0228] The difference from Example 2 is that the preparation method is as follows: the recycled fine aggregate and the recycled coarse aggregate are not pretreated, and all the raw materials of Example 2 are directly mixed at one time.

[0229] Comparative Example 2

[0230] Low shrinkage recycled aggregate ultra-high performance concrete material, including the following raw materials in parts by weight:

[0231] 400 parts of natural river sand fine aggregate with a particle size of 0.315-1.25 mm;

[0232] 400 parts of recycled fine aggregate with a particle size of 0.315 to 1.25 mm;

[0233] 480 parts of natural basalt coarse aggregate with a particle size of 4.75 to 6.12 mm;

[0234] 320 parts of recycled coarse aggregate with a particle size of 4.75 to 6.12 mm;

[0235] 150 parts of silica fume;

[0236] Water-binder ratio 0.185;

[0237] 20 parts of polycarboxylate water reducer;

[0238] 150 parts of 8-12mm steel fiber;

[0239] 50 parts of 0.18-0.22mm nanofibers;

[0240] PO 42.5 cement 850 parts.

[0241] The difference from Example 2 is that among the raw materials of the low shrinkage recycled aggregate ultra-high performance concrete material, all natural river sand fine aggregates are natural river sand fine aggregates with a particle size of 0.315 to 1.25 mm, all recycled fine aggregates are recycled fine aggregates with a particle size of 0.315 to 1.25 mm, all natural basalt coarse aggregates are natural basalt coarse aggregates with a particle size of 4.75 to 6.12 mm, and all recycled coarse aggregates are recycled coarse aggregates with a particle size of 4.75 to 6.12 mm. The other components and contents remain unchanged; the preparation method is the same as that of Example 2.

[0242] Comparative Example 3

[0243] Low shrinkage recycled aggregate ultra-high performance concrete material, including the following raw materials in parts by weight:

[0244] 100 parts of natural river sand fine aggregate with a particle size of 0.155-0.315 mm;

[0245] 140 parts of natural river sand fine aggregate with a particle size of 0.315-1.25 mm;

[0246] 160 parts of natural river sand fine aggregate with a particle size of 1.25 to 2.36 mm;

[0247] 100 parts of recycled fine aggregate with a particle size of 0.155 to 0.315 mm;

[0248] 140 parts of recycled fine aggregate with a particle size of 0.315 to 1.25 mm;

[0249] 160 parts of laboratory recycled fine aggregate with a particle size of 1.25 to 2.36 mm;

[0250] 120 parts of natural basalt coarse aggregate with a particle size of 2.36 to 4.75 mm;

[0251] 168 parts of natural basalt coarse aggregate with a particle size of 4.75 to 6.12 mm;

[0252] 192 parts of natural basalt coarse aggregate with a particle size of 6.12 to 8.36 mm;

[0253] 80 parts of recycled coarse aggregate with a particle size of 2.36 to 4.75 mm;

[0254] 112 parts of recycled coarse aggregate with a particle size of 4.75 to 6.12 mm;

[0255] 128 parts of recycled coarse aggregate with a particle size of 6.12 to 8.36 mm;

[0256] 150 parts of silica fume;

[0257] Water-binder ratio 0.185;

[0258] 20 parts of polycarboxylate water reducer;

[0259] 150 parts of 8-12mm steel fiber;

[0260] 50 parts of 0.18-0.22mm nanofibers;

[0261] PO 42.5 cement 850 parts.

[0262] The raw material composition is the same as that in Example 2. The difference from Example 2 is that in the preparation method, during the pretreatment of the recycled fine aggregate and the recycled fine aggregate, after pre-wetting treatment, the moisture content of the recycled coarse aggregate is 6wt.%, and the moisture content of the recycled fine aggregate is 8wt.%.

[0263] Comparative Example 4

[0264] Low shrinkage recycled aggregate ultra-high performance concrete material, including the following raw materials in parts by weight:

[0265] 100 parts of natural river sand fine aggregate with a particle size of 0.155-0.315 mm;

[0266] 140 parts of natural river sand fine aggregate with a particle size of 0.315-1.25 mm;

[0267] 160 parts of natural river sand fine aggregate with a particle size of 1.25 to 2.36 mm;

[0268] 100 parts of recycled fine aggregate with a particle size of 0.155 to 0.315 mm;

[0269] 140 parts of recycled fine aggregate with a particle size of 0.315 to 1.25 mm;

[0270] 160 parts of laboratory recycled fine aggregate with a particle size of 1.25 to 2.36 mm;

[0271] 120 parts of natural basalt coarse aggregate with a particle size of 2.36 to 4.75 mm;

[0272] 168 parts of natural basalt coarse aggregate with a particle size of 4.75 to 6.12 mm;

[0273] 192 parts of natural basalt coarse aggregate with a particle size of 6.12 to 8.36 mm;

[0274] 80 parts of recycled coarse aggregate with a particle size of 2.36 to 4.75 mm;

[0275] 112 parts of recycled coarse aggregate with a particle size of 4.75 to 6.12 mm;

[0276] 128 parts of recycled coarse aggregate with a particle size of 6.12 to 8.36 mm;

[0277] 150 parts of silica fume;

[0278] Water-binder ratio 0.185;

[0279] 20 parts of polycarboxylate water reducer;

[0280] 150 parts of 8-12mm steel fiber;

[0281] 50 parts of 0.18-0.22mm nanofibers;

[0282] PO 42.5 cement 850 parts.

[0283] The raw material composition is the same as that in Example 2. The difference from Example 2 is that in the preparation method, during the pretreatment of the recycled fine aggregate and the recycled fine aggregate, after humidification treatment, the moisture content of the recycled coarse aggregate is 1wt.%, and the moisture content of the recycled fine aggregate is 15wt.%.

[0284] Performance Testing

[0285] The standard specimens of the low-shrinkage recycled aggregate ultra-high performance concrete materials described in Examples 1 to 3 and Comparative Examples 1 to 4 were prepared and subjected to compressive strength, splitting tensile strength, elastic modulus, and shrinkage tests after 28 days of standard curing. The experimental data are shown in Table 1.

[0286] Table 1 Test data of low shrinkage recycled aggregate ultra-high performance concrete materials

[0287]

[0288] From Table 1, it can be seen that the compressive strength of all the embodiments of the present invention is greater than 120 MPa, the splitting tensile strength is greater than 10 MPa, and the elastic modulus is greater than 34 GPa, indicating that the mechanical properties are good. For ultra-high performance concrete, its apparent density is generally not less than 2500 kg·m 3 Generally speaking, a higher apparent density indicates a denser concrete, while a lower porosity indicates a higher compressive strength. The data from Examples 1-3 show that the low-replacement recycled aggregate in Example 1 exhibits relatively better mechanical properties and shrinkage values ​​than in Examples 2 and 3. The material ratios used in Example 2 of the present invention are optimal, making it more economical than in Example 1.

[0289] The reason for the performance decline in Comparative Example 1 relative to Example 2 is that, without pre-treating the recycled aggregate, some old mortar adheres to the surface of the recycled aggregate. Therefore, during mixing, the bond strength between the old mortar layer and the new mortar decreases, leading to performance decline. The main reason for the performance decline in Comparative Example 2 relative to Example 2 is that, without particle size grading, less aggregate is available to fill the gaps between the aggregates, resulting in greater porosity in the concrete and a decline in performance. Comparative Examples 3 and 4 also show performance decline relative to Example 2. The relatively minor performance decline is due to the fact that their moisture content is similar to that of the examples, meaning that the actual water-cement ratios in the comparative examples are similar to those in the examples.

[0290] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or to replace portions thereof with equivalents. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A low shrinkage recycled aggregate ultra-high performance concrete, characterized in that: It is composed of the following raw materials in parts by weight: 840-860 parts of Portland cement, 140-160 parts of silica fume, 320-480 parts of natural river sand fine aggregate, 320-480 parts of recycled fine aggregate, 400-560 parts of natural basalt coarse aggregate, 240-400 parts of recycled coarse aggregate, 18-22 parts of water reducer, 40-60 parts of carbon fiber, 140-160 parts of steel fiber, and 420-640 parts of water. The composition of the natural river sand fine aggregate is as follows: 80-120 parts of natural river sand fine aggregate with a particle size of 0.155-0.315mm; 112-168 parts of natural river sand fine aggregate with a particle size of 0.315-1.25 mm; 128-192 parts of natural river sand fine aggregate with a particle size of 1.25-2.36 mm; The composition of the recycled fine aggregate is as follows: 80-120 parts of recycled fine aggregate with a particle size of 0.155-0.315 mm; 112-168 parts of recycled fine aggregate with a particle size of 0.315-1.25 mm; 128-192 parts of recycled fine aggregate with a particle size of 1.25-2.36 mm; The composition of the natural basalt coarse aggregate is as follows: 100-140 parts of natural basalt coarse aggregate with a particle size of 2.36-4.75 mm; 140-196 parts of natural basalt coarse aggregate with a particle size of 4.75-6.12 mm; 160-224 parts of natural basalt coarse aggregate with a particle size of 6.12-8.36 mm; The composition of the recycled coarse aggregate is as follows: 60-100 parts of recycled coarse aggregate with a particle size of 2.36-4.75 mm; 84-140 parts of recycled coarse aggregate with a particle size of 4.75-6.12 mm; 96-160 parts of recycled coarse aggregate with a particle size of 6.12-8.36 mm; The recycled fine aggregate is prepared by pretreatment, and the specific pretreatment steps are as follows: (1) Crushing and screening concrete to obtain crushed recycled fine aggregate; (2) mixing the recycled fine aggregate in step (1) with water for humidification treatment, and controlling the moisture content of the recycled fine aggregate; (3) carbonizing the recycled fine aggregate after the humidification treatment in step (2) to obtain recycled fine aggregate with a particle size of 0.155 to 2.36 mm; The recycled coarse aggregate is prepared by pretreatment, and the specific pretreatment steps are as follows: (1) Crushing and screening concrete to obtain crushed recycled coarse aggregate; (2) mixing the recycled coarse aggregate in step (1) with water for humidification treatment, and controlling the moisture content of the recycled coarse aggregate; (3) acid-treating, washing, and drying the recycled coarse aggregate after the humidification treatment in step (2) to obtain acid-treated recycled coarse aggregate; (4) The recycled coarse aggregate after the acid treatment in step (3) is carbonized to obtain recycled coarse aggregate with a particle size of 2.36 to 8.36 mm.

2. The low shrinkage recycled aggregate ultra-high performance concrete according to claim 1, characterized in that: The material is composed of the following raw materials in parts by weight: 850 parts of Portland cement, 150 parts of silica fume, 320-480 parts of natural river sand fine aggregate, 320-480 parts of recycled fine aggregate, 400-560 parts of natural basalt coarse aggregate, 240-400 parts of recycled coarse aggregate, 20 parts of water reducer, 50 parts of carbon fiber, 150 parts of steel fiber, and 440 parts of water. The Portland cement is a Portland cement with a PO of not less than 42.5; the SiO2 content in the silica fume is not less than 92 wt.%; The water reducer is a polycarboxylate water reducer with a water reduction rate greater than 25%; The steel fiber has a tensile strength greater than 25 GPa and a length of 8 to 12 mm. The carbon fiber has a tensile strength greater than 30 GPa and a length of 0.18 to 0.22 mm.

3. The low shrinkage recycled aggregate ultra-high performance concrete according to claim 1 or 2, characterized in that: The particle size of the natural river sand fine aggregate and the particle size of the recycled fine aggregate are both 0.155-2.36 mm; The particle size of the natural basalt coarse aggregate and the particle size of the recycled coarse aggregate are both 2.36~8.36 mm.

4. The low shrinkage recycled aggregate ultra-high performance concrete according to claim 1, characterized in that: During the pretreatment of the recycled fine aggregate or recycled coarse aggregate, the carbonization treatment conditions are: 20-30°C, 50-70% relative humidity, and 0.5-1 mPa air pressure for 20-24 hours; During the pretreatment of the recycled fine aggregate or recycled coarse aggregate, after the humidification treatment, the moisture content of the recycled fine aggregate is 9-12wt.%, and the moisture content of the recycled coarse aggregate is 2-5wt.%; During the pretreatment of the recycled coarse aggregate, the acid treatment is performed by using 0.12-2 mol / L dilute hydrochloric acid for immersion for 20-24 hours.

5. The low shrinkage recycled aggregate ultra-high performance concrete according to claim 1, characterized in that: The composition of the natural river sand fine aggregate is as follows: 120 parts of natural river sand fine aggregate with a particle size of 0.155 to 0.315 mm; 168 parts of natural river sand fine aggregate with a particle size of 0.315 to 1.25 mm; 192 parts of natural river sand fine aggregate with a particle size of 1.25 to 2.36 mm; The composition of the recycled fine aggregate is as follows: 80 parts of recycled fine aggregate with a particle size of 0.155 to 0.315 mm; 112 parts of recycled fine aggregate with a particle size of 0.315 to 1.25 mm; 128 parts of recycled fine aggregate with a particle size of 1.25 to 2.36 mm; The composition of the natural basalt coarse aggregate is as follows: 140 parts of natural basalt coarse aggregate with a particle size of 2.36 to 4.75 mm; 196 parts of natural basalt coarse aggregate with a particle size of 4.75 to 6.12 mm; 224 parts of natural basalt coarse aggregate with a particle size of 6.12 to 8.36 mm; The composition of the recycled coarse aggregate is as follows: 60 parts of recycled coarse aggregate with a particle size of 2.36 to 4.75 mm; 84 parts of recycled coarse aggregate with a particle size of 4.75 to 6.12 mm; 96 parts of recycled coarse aggregate with a particle size of 6.12~8.36mm.

6. The low shrinkage recycled aggregate ultra-high performance concrete according to claim 1, characterized in that: The composition of the natural river sand fine aggregate is as follows: 100 parts of natural river sand fine aggregate with a particle size of 0.155 to 0.315 mm; 140 parts of natural river sand fine aggregate with a particle size of 0.315 to 1.25 mm; 160 parts of natural river sand fine aggregate with a particle size of 1.25 to 2.36 mm; The composition of the recycled fine aggregate is as follows: 100 parts of recycled fine aggregate with a particle size of 0.155 to 0.315 mm; 140 parts of recycled fine aggregate with a particle size of 0.315 to 1.25 mm; 160 parts of recycled fine aggregate with a particle size of 1.25 to 2.36 mm; The composition of the natural basalt coarse aggregate is as follows: 120 parts of natural basalt coarse aggregate with a particle size of 2.36 to 4.75 mm; 168 parts of natural basalt coarse aggregate with a particle size of 4.75 to 6.12 mm; 192 parts of natural basalt coarse aggregate with a particle size of 6.12 to 8.36 mm; The composition of the recycled coarse aggregate is as follows: 80 parts of recycled coarse aggregate with a particle size of 2.36 to 4.75 mm; 112 parts of recycled coarse aggregate with a particle size of 4.75 to 6.12 mm; 128 parts of recycled coarse aggregate with a particle size of 6.12~8.36mm.

7. The low shrinkage recycled aggregate ultra-high performance concrete according to claim 1, characterized in that: The composition of the natural river sand fine aggregate is as follows: 80 parts of natural river sand fine aggregate with a particle size of 0.155 to 0.315 mm; 112 parts of natural river sand fine aggregate with a particle size of 0.315 to 1.25 mm; 128 parts of natural river sand fine aggregate with a particle size of 1.25 to 2.36 mm; The composition of the recycled fine aggregate is as follows: 120 parts of recycled fine aggregate with a particle size of 0.155 to 0.315 mm; 168 parts of recycled fine aggregate with a particle size of 0.315 to 1.25 mm; 192 parts of recycled fine aggregate with a particle size of 1.25 to 2.36 mm; The composition of the natural basalt coarse aggregate is as follows: 100 parts of natural basalt coarse aggregate with a particle size of 2.36 to 4.75 mm; 140 parts of natural basalt coarse aggregate with a particle size of 4.75 to 6.12 mm; 160 parts of natural basalt coarse aggregate with a particle size of 6.12 to 8.36 mm; The composition of the recycled coarse aggregate is as follows: 100 parts of recycled coarse aggregate with a particle size of 2.36 to 4.75 mm; 140 parts of recycled coarse aggregate with a particle size of 4.75 to 6.12 mm; 160 parts of recycled coarse aggregate with a particle size of 6.12~8.36mm.

8. A method for preparing the low shrinkage recycled aggregate ultra-high performance concrete according to any one of claims 1 to 7, characterized in that: The steps include: S1, adding a water reducer and carbon fiber to water and mixing evenly to obtain a first mixture; S2, evenly mixing Portland cement and silica fume and adding them to the first mixture in S1 in batches, mixing evenly to obtain a second mixture; S3, adding steel fiber to the second mixture in S2, mixing evenly, to obtain a third mixture; S4, mixing the natural river sand fine aggregate and the recycled fine aggregate evenly, and adding the mixture to the third mixture in S3, mixing evenly, to obtain a fourth mixture; S5, adding natural basalt coarse aggregate evenly to the fourth mixture in S4, mixing evenly, to obtain a fifth mixture; S6. Evenly add the recycled coarse aggregate into the fifth mixture in S5, mix well, and obtain low shrinkage ultra-high performance concrete.

9. Use of the low-shrinkage recycled aggregate ultra-high performance concrete according to any one of claims 1 to 5 in preparing ultra-high performance concrete with low shrinkage.

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