CA-UHPC material preparation and premixing fine production process

Abstract

The invention discloses a preparation and premixing fine production process of a CA-UHPC material. The preparation and premixing fine production process comprises the CA-UHPC material, a preparation process, production equipment and an application part. According to the method, coarse aggregate and fine aggregate are screened for three times and two times respectively, the coarse aggregate, the fine aggregate, water, an additive and fibers are mixed according to the mix proportion design requirement, the CA-UHPC material which is stable in mechanical property, controllable in quality and stable in all performance is obtained, the disclosure of production equipment also enables the CA-UHPC premix to obtain balanced, stable and consistent output, the construction difficulty and the use cost are reduced, and the construction period is shortened. And the application universality of the material is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of concrete, in particular to a preparation of CA-UHPC material and a premixed fine production process. BACKGROUND

[0002] Ultra-high performance concrete (UHPC) has been widely used in bridge engineering construction in recent years due to its high mechanical properties and durability. However, the elastic modulus and volume stability of UHPC material are important bottlenecks restricting the further development of UHPC structure. If coarse aggregate is introduced into UHPC to form coarse aggregate ultra-high performance concrete (CA-UHPC) for material components with higher cross-sectional thickness, and river sand or machine-made sand of appropriate specification and gradation is used to replace quartz sand in UHPC, the high strength, high ductility and high durability of UHPC can be retained, and the elastic modulus can be further improved, the shrinkage and creep deformation can be reduced, and the skeleton effect of coarse aggregate can effectively reduce the shrinkage of UHPC, further improve the elastic modulus (more than 56GPa), and to a certain extent, reduce the use of active powder, improve the green economy and low-carbon environmental protection of material application.

[0003] However, the current CA-UHPC mixing scheme is conventional and fails to effectively control the quality stability of coarse aggregate and sand. The mix proportion application is not fine and environmentally friendly, and the process regulation and quality reliability still need to be improved. The current application scheme mainly includes four categories of raw materials: active powder concrete, coarse aggregate, river sand, and fiber. These raw materials are separately packaged in advance, then transported to the site, and then re-weighed and mixed. Alternatively, 6-9 kinds of active powder, coarse aggregate, river sand, and fiber are added and mixed on site through mature mixing equipment. According to the literature research results that can be widely investigated at present, the above two application schemes have the following shortcomings: ① The technical quality of coarse aggregate cannot be monitored in batches when it enters the site. The gradation specification, dust content, and silt content indicators fluctuate. The instability of the first two performance parameters will amplify the genetic defects of CA-UHPC inherent aggregate and fiber winding. ② The source of natural river sand is unstable and the supply is not guaranteed. The gradation specification, fineness modulus, and silt content indicators are difficult to control, which is a control difficulty for concrete quality and performance stability, resulting in large instability of CA-UHPC product quality. ③ The machine-made sand is currently basically medium-coarse sand, with a fineness modulus generally in the range of 2.8-3.5. The particles of >2.36 mm and <0.15 mm in machine-made sand are more, while the intermediate particles are less (especially 0.3 mm-1.18 mm). The <300 μm particles are too few, and the gradation is unreasonable, which will lead to the decrease of CA-UHPC product density and the deterioration of work performance. ④ The natural moisture content of coarse and fine aggregate will cause instability of the key mechanical properties of CA-UHPC product with extremely low water-binder ratio and extremely high sensitivity (when the moisture content of coarse aggregate and sand changes by ±1%, the actual water consumption of CA-UHPC will fluctuate by 8-10%: assuming that the composition ratio of 1 m³ CA-UHPC is: coarse aggregate 550 kg, sand 700 kg, cementitious material 1000 kg, standard design water-binder ratio 0.1400, and single water consumption 140 kg. When the moisture content of coarse aggregate and sand changes by +1%, the concrete will increase by 12.5 kg / m³ water consumption, with an increase of 8.9%, and the actual water-binder ratio will change to 0.1525); ④ The silt content naturally brought by coarse aggregate and river sand will have adverse effects on the shrinkage and creep of CA-UHPC. In addition, the actual large-scale and continuous pouring engineering conditions on site will also increase the quality control difficulty of all management links. In order to better protect the performance and quality of CA-UHPC, a targeted material design premixing technology needs to be developed. SUMMARY

[0004] To solve the foregoing problems, one of the purposes of the present application is to provide a preparation process of CA-UHPC material, which improves the static and dynamic elastic modulus of UHPC material, reduces the self-shrinkage deformation, reduces the later creep, improves the volume stability, obtains CA-UHPC material with stable mechanical properties and controllable quality, and improves the stability of the CA-UHPC mixing ratio quality, and realizes comprehensive improvement of the stability of all properties of CA-UHPC.

[0005] The second purpose of the present application is to provide an equipment for producing CA-UHPC material, which can realize the re-screening and re-combination of materials such as coarse aggregate, machine-made sand, river sand and the like to the level of 0.075mm particle size, reduces the influence of the unstable properties of natural materials on the quality of CA-UHPC, makes the CA-UHPC premix material obtain balanced and stable output, and solves the problem that the production of concrete has been plagued by the influence of aggregate quality.

[0006] The third purpose of the present application is to provide a CA-UHPC material, which reduces the dependence of UHPC industry development on scarce and expensive materials, promotes local material utilization, pays attention to solid waste resource utilization, and improves the technical and economic efficiency of material application.

[0007] The fourth purpose of the present application is to provide the application of CA-UHPC material in road pavement, airport pavement and bridge deck, which improves the material performance stability through fine processing of raw materials, close packing and accurate blending, simplifies the process of on-site mixing of CA-UHPC material, reduces the construction difficulty and use cost, and improves the universality of material application.

[0008] The specific technical solutions of the present application are as follows: The first aspect of the present application discloses a CA-UHPC material, which comprises the following raw materials in parts by weight: Cement 500-700 parts Silica fume 150-250 parts Fly ash 200-300 parts Mineral powder 0-150 parts Limestone powder 0-70 parts Metakaolin 0-50 parts 0~0.075mm sand 0-50 parts 0.075~0.2mm sand 0-200 parts 0.2~0.4mm sand 100-200 parts 0.4~0.6mm sand 100-250 parts 0.6~1.18mm sand 50-200 parts 1.18~2.36mm sand 0-200 parts 2.36~4.75mm sand 0-150 parts 4.75~7.1mm aggregate 150-250 parts 7.1~9.5mm aggregate 150-250 parts.

[0009] Further, the CA-UHPC material further comprises steel fiber, additive, water.

[0010] Preferably, the weight fraction of each raw material in the CA-UHPC material is: Cement 600 parts Silica fume 200 parts Fly ash 150 parts Slag 100 parts Limestone powder 40 parts Metakaolin 30 parts 0~0.075mm sand 30 parts 0.075~0.2mm sand 40 parts 0.2~0.4mm sand 80 parts 0.4~0.6mm sand 200 parts 0.6~1.18mm sand 200 parts 1.18~2.36mm sand 100 parts 2.36~4.75mm sand 50 parts 4.75~7.1mm aggregate 250 parts 7.1~9.5mm aggregate 200 parts.

[0011] The second aspect of the present application discloses a preparation process of the CA-UHPC material, comprising the following steps: After the continuous high-temperature drying and cold air cooling treatment of the coarse aggregate, the removal treatment of the dust content of <0.075mm is realized, the water content of the aggregate is 0%, the clay content is 0.3%, and the shaped treatment of the treated aggregate is realized, so that the needle flake content of the aggregate is 0%, and the roundness of all coarse aggregate particles basically reaches the above level of sub-spherical shape; The coarse aggregate is subjected to one-time probability screening to produce >8, 8~6.5, 6.5~5 / 4.75 / 4.5 / 4.25 / 4 three-grade specification materials, the aggregate smaller than 5 / 4.75 / 4.5 / 4.25 / 4 mm is subjected to secondary air screening to produce 4.75~2.36, 2.36~1.18, 1.18~0.600 and <0.600 four-grade ultra-fine specification materials, and the ultra-fine aggregate smaller than 0.600 mm is subjected to three-time swing screening to produce 0.600~0.425, 0.425~0.212, 0.212~0.075, 0.075~0 four-grade extremely fine specification materials; Fine aggregate treatment: after continuous high temperature drying and cold air cooling treatment of fine aggregate, the removal treatment of the content of <0.075 mm dust is realized, the moisture content of 0%, the clay content of 0.3%, and the sand equivalent of >85% are realized, and the aggregate after treatment is shaped; The fine aggregate is subjected to primary air screening to produce four grades of ultra-fine aggregate of 4.75~2.36, 2.36~1.18, 1.18~0.600 and <0.600, and the ultra-fine aggregate smaller than 0.600 mm is subjected to secondary swing screening to produce four grades of extremely fine aggregate of 0.600~0.425, 0.425~0.212, 0.212~0.075 and 0.075~0. The coarse aggregate and the fine aggregate are mixed to obtain premix, water and an additive are added to the premix according to the design requirements of the mixing ratio, and the premix is stirred for 3-4 min by frequency conversion; the fiber is added to the premix for 1.5-3 min to obtain the CA-UHPC.

[0012] Further, the primary probability screening of the coarse aggregate uses 9.5~7.1~5.5 / 5 / 4 three-layer screens, the secondary air screening of the coarse aggregate uses 4.75~2.36~1.18~0.600 four-layer screens, the third swing screening of the coarse aggregate uses 0.600~0.425~0.212~0.075 four-layer screens, the primary air screening of the fine aggregate uses 4.75~2.36~1.18~0.600 four-layer screens, and the secondary swing screening of the fine aggregate uses 0.600~0.425~0.212~0.075 four-layer screens.

[0013] Preferably, the fiber is one or more of steel fiber, basalt fiber, plant fiber, glass fiber and carbon fiber.

[0014] Preferably, the additive is one or more of mineral admixture, rheological control component, shrinkage inhibiting component, interface modifier, air entraining agent and water reducing agent.

[0015] The third aspect of the present application discloses an equipment for producing the CA-UHPC material, which comprises an aggregate treatment system, a powder treatment system and a mixing system, wherein: The aggregate treatment system comprises a feeding platform, an aggregate drying channel, a dust removal system, an aggregate shaping system, an aggregate lifting device, a screening system and an aggregate storage tank, the aggregate drying channel is connected with the feeding platform and the dust removal system at two ends, the aggregate lifting device is connected with the dust removal system through the aggregate shaping system, and the other end of the aggregate lifting device is connected with the screening system, the lifted aggregate falls into the screening system for screening, the screening system is connected with the aggregate storage tank through a plurality of channels, different levels of aggregate correspond to different channels and the aggregate storage tanks connected with the channels; The powder processing system is composed of a powder raw material lifting device and a powder storage tank, the powder raw material lifting device is connected with the powder storage tank, and the powder is transferred to the powder storage tank; The mixing system comprises a premixing stirring device, the premixing stirring device is connected with the aggregate storage tank and the powder storage tank, and after the quantitative aggregate and powder are mixed in the premixing stirring device, the aggregate and powder are transferred to a packaging system for discharging.

[0016] The equipment for preparing the coarse aggregate active powder UHPC further comprises a control system connected with the aggregate processing system, the powder processing system and the mixing system, and used for controlling the start and stop of each system, that is, the premixing ratio can be controlled by controlling the opening of the aggregate storage tank and the powder storage tank.

[0017] Preferably, the mixing system further comprises a packaging system composed of a sealing device and a transfer device, after the quantitative aggregate and powder are mixed in the premixing stirring device, the aggregate and powder are sealed by the sealing device and are transferred out of the packaging system by the transfer device.

[0018] The fourth aspect of the present application discloses the application of the preparation process of the CA-UHPC material in road pavement, bridge pavement and airport pavement. Through early fine processing of raw materials, close packing and accurate blending, the material performance stability can be improved; the process of on-site mixing of the CA-UHPC material is simplified, the construction difficulty and use cost are reduced, and the universality of the material application is improved.

[0019] The material obtained by the present application can achieve the following beneficial effects: (1) For the CA-UHPC structure of large volume and continuous pouring, the elastic modulus is significantly improved. By using the present process, the negative effects of the poor properties of the aggregate on the material performance can be completely eliminated, and the roundness of the aggregate is improved, so that the coarse and fine aggregates and the active powder are packed, and the theoretical best state of continuous and extremely close packing is achieved from the macro, meso and micro levels, and the elastic modulus of the prepared CA-UHPC can be improved by 20-60% (the elastic modulus is improved from 48-52 GPa to 56-80 GPa).

[0020] (2) The self-shrinkage of the continuously poured UHPC structure is significantly reduced, and the volume stability is improved. Figure 2 , Figure 3 As shown in the drawings, with the continuous increase of the volume content of the coarse aggregate, the dry shrinkage of the UHPC is obviously reduced, and the dry shrinkage of the UHPC can be reduced by 33.7% at most. By reducing the amount of cementitious material and playing the role of rigid skeleton, the coarse aggregate with a volume content of 32% can reduce the self-shrinkage of the UHPC by 20-38%, and by introducing 400 kg / m 3The coarse aggregate is prepared, the compressive strength of the prepared CA-UHPC is more than 200 MPa, the elastic modulus is more than 56 GPa, the shrinkage creep is reduced by 60%, and the cement consumption is reduced by 30%. The shrinkage rate of the quartz sand UHPC is the largest, and the 120d dry shrinkage reaches 568με. The 120d dry shrinkage rate of the river sand UHPC is reduced by 6.5% compared with that of the quartz sand UHPC. The coarse aggregate content has a significant effect on the shrinkage of the CA-UHPC. Compared with the UHPC without coarse aggregate, the self-shrinkage rate of the CA-UHPC with a content of 20% is reduced by 21.75%, and the total shrinkage rate is reduced by 28.12%. It is also found that when the content of the coarse aggregate increases from 0% to 20%, the proportion of the self-shrinkage of the CA-UHPC in the total shrinkage increases from 70% to 90%. Changing the type of the coarse aggregate can reduce the self-shrinkage rate of the CA-UHPC by about 4.47%.

[0021] (3) The use amount of the cement-based cementitious material is significantly reduced, and carbon emission is reduced. On the basis of guaranteeing mechanical properties, durability, elastic modulus and flexural strength, the use amount of the cementitious material can be reduced by 5.0%-9.0%; the total carbon emission of the CA-UHPC structure in the whole life cycle is further reduced, and remarkable ecological benefits are achieved.

[0022] (4) The high-priced quartz sand material is completely replaced, various types of mechanism sand or low-priced natural sand can be stably produced or supplied, and the economic benefits are great, the problem of dependence on scarce and expensive materials in the UHPC industry is solved, local materials are used, solid waste resource utilization is emphasized, and the technical economy of material application is improved. After the quartz sand is completely replaced by the low-priced mechanism sand or river sand or mountain sand, compared with the natural river sand, the market price of the quartz sand is about 900 yuan / ton, the market price of the mountain sand or river sand is about 190 yuan / ton, and the market price of the mechanism sand is about 150 yuan / ton. When the mountain sand or river sand is used to replace the quartz sand, the material cost of each cubic meter of CA-UHPC can be saved by 426-568 yuan; when the mechanism sand is used to replace the quartz sand, the material cost of each cubic meter of CA-UHPC can be saved by 450-600 yuan. Taking a large bridge as an example, the CA-UHPC consumption is about 10,000 square meters, and it is expected that at least 4.26 million yuan of cost can be saved.

[0023] (5) The mix proportion design method of the CA-UHPC in large-scale operation, micro-particle shaping, ultra-fine screening and prefabricated mixing is improved. The material provided by the application is composed of mountain sand or river sand or mechanism sand, coarse and fine aggregates after fine treatment and screening, external admixture powder and cement-based cementitious material, the dry mixing process and related control parameters are determined according to the uniformity of pre-mixing; the wet mixing process and related control parameters are determined according to the time-varying law of fluidity, so that the mixing quality of the concrete is ensured.

[0024] In addition, due to the production process provided by the present application, all key raw material fine processing, tight packing and accurate blending can be completed in the factory in advance, which can comprehensively improve the material performance stability; and simplify the on-site mixing process of the CA-UHPC material, reduce the construction difficulty and use cost, improve the universality of the material application; also effectively reduce the dust generated in the traditional UHPC production and mixing process, reduce the harm to the surrounding environment, and have significant green development effect. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is a design method schematic diagram of the CA-UHPC material.

[0026] Figure 2 is a self-shrinkage value comparison experiment result of the CA-UHPC material.

[0027] Figure 3 is the influence result of the coarse aggregate content of the CA-UHPC material on the total shrinkage of the UHPC.

[0028] Figure 4 is a top view of the coarse aggregate active powder UHPC production equipment.

[0029] Among them, 1 is a feeding platform, 2 is an aggregate drying channel, 3 is a dust removal system, 4 is an aggregate lifting device, 5 is a screening system, 6 is an aggregate storage tank, 7 is a raw material lifting device, 8 is a powder storage tank, 9 is a premixing stirring device, 10 is a packaging system, and 11 is an aggregate shaping system. DETAILED DESCRIPTION

[0030] The specific embodiments of the present application will be further described in detail below in combination with the drawings, examples and comparative examples. The following examples and comparative examples are only used to more clearly illustrate the technical solutions of the present application, so that those skilled in the art can well understand and utilize the present application, rather than limiting the protection scope of the present application.

[0031] The experimental methods, production processes, instruments and equipment involved in the embodiments and comparative examples of the present application are all conventional names in the art, and are very clear and explicit in the relevant application field. Those skilled in the art can understand the conventional process steps and apply the corresponding equipment according to the conventional conditions or the conditions recommended by the manufacturer.

[0032] The various raw materials or reagents used in the embodiments and comparative examples of the present application do not have special restrictions on the source, and are all conventional products that can be obtained by market purchase.

[0033] Example 1: Production device and preparation process of CA-UHPC.

[0034] AsFigure 4 The CA-UHPC material production equipment shown includes an aggregate processing system, a powder processing system, a mixing system, and a control system. The aggregate processing system consists of a feeding platform 11, an aggregate drying channel 2, a dust removal system 3, an aggregate shaping system 11, an aggregate lifting device 4, a screening system 5, and an aggregate storage tank 6. The powder processing system consists of a powder raw material lifting device 7 and a powder storage tank 8. The mixing system includes a pre-mixing device 9 and a packaging system 10.

[0035] In this embodiment, a probability screen is selected as the screening system 5, the aggregate drying channel 2 is set as a double-pass rotary drum dryer, and the premixing device 9 uses a plow-type mixer.

[0036] The feeding platform 11 is a conveying device with a certain inclination angle. The aggregate drying channel 2 is connected at both ends to the feeding platform 11 and the dust removal system 3, respectively. The aggregate lifting device 4 is connected to the dust removal system 3 through the aggregate shaping system 11. The other end of the aggregate lifting device 4 is connected to the screening system 5. The lifted aggregate falls into the screening system 5 for screening. The screening system 5 is connected to the aggregate storage tank 6 through several channels. Different grades of aggregate correspond to different channels and aggregate storage tanks 6 connected to the channels. Figure 4 As shown, the powder raw material lifting device 7 is connected to the powder storage tank 8, transferring the powder into the powder storage tank 8. The premixing device 9 is connected to the aggregate storage tank 6 and the powder storage tank 8. A fixed amount of aggregate and powder enters the premixing device 9 for mixing, and then is transferred to the packaging system 10 for discharge. The packaging system 10 consists of a sealing device and a transfer device. A fixed amount of aggregate and powder enters the premixing device 9 for mixing, then enters the sealing device for packaging and sealing, and is transferred out of the packaging system 10 by the transfer device.

[0037] The control system is connected to the aggregate processing system, powder processing system, and mixing system, and is used to control the start and stop of each system. That is, the premixing ratio can be controlled by controlling the opening of the aggregate storage tank 6 and the powder storage tank 8.

[0038] use Figure 4 The steps for producing CA-UHPC using the equipment shown are as follows: 1) The aggregate is transferred to the aggregate drying channel 2 via the feeding platform 11, and then transferred to the dust removal system 3 and aggregate shaping system 11 for further processing. The processed aggregate is transferred to the screening system 5 via the lifting device. In the screening system 5, the aggregate is screened into 0~0.075mm sand, 0.075~0.2mm sand, 0.2~0.4mm sand, 0.4~0.6mm sand, 0.6~1.18mm sand, 1.18~2.36mm sand, 2.36~4.75mm sand, 4.75~7.1mm coarse aggregate, and 7.1~9.5mm coarse aggregate, and placed into the aggregate storage tank 6 respectively.

[0039] 2) Open the aggregate storage tank 6 by using the control system, and make the following weights of materials enter the premixing and mixing system: 30 kg of 0~0.075 mm sand, 40 kg of 0.075~0.2 mm sand, 80 kg of 0.2~0.4 mm sand, 200 kg of 0.4~0.6 mm sand, 200 kg of 0.6~1.18 mm sand, 100 kg of 1.18~2.36 mm sand, 50 kg of 2.36~4.75 mm sand, 250 kg of 4.75~7.1 mm coarse aggregate, and 200 kg of 7.1~9.5 mm coarse aggregate, and mix them uniformly in the premixing and mixing system to obtain an aggregate mixture.

[0040] 3) Put cement, silica fume, fly ash, and mineral powder into the powder storage tank 8 by using the powder raw material lifting device 7, open the powder storage tank 8 by using the control system, and make 600 kg of cement, 200 kg of silica fume, 150 kg of fly ash, 100 kg of mineral powder, 40 kg of limestone powder, and 30 kg of metakaolin enter the premixing and mixing system, mix them uniformly with the aggregate mixture, and obtain a CA-UHPC product powder with a target mixing ratio.

[0041] 4) Open the channel between the premixing and mixing system and the packaging system 10, package and seal the CA-UHPC product powder.

[0042] 5) After the CA-UHPC product powder is transferred to the destination, 200 kg of steel fiber, 15 kg of additive, and 150 kg of water are added to 2200 kg of the CA-UHPC product powder, the mixture is stirred for about 3-5 min by using a vertical shaft planetary mixer, and the mixture is unloaded when the current is stable.

[0043] Example 2: Comparison experiment of screening accuracy

[0044] The concrete mixing ratio used by the CA-UHPC in this example and the following examples is shown in Table 1 (unit: Kg / m 3 );

[0045] This example compares the screening accuracy of the coarse aggregate screening part (aggregate processing system and powder processing system) in the equipment provided by the application with that of different types of sand and aggregate screening machines in the prior art, and the results are shown in Table 2.

[0046] In the comparison group 1, a certain drum-type sand and aggregate screening machine is used; In the comparison group 2, a certain vibrating screen-type sand and aggregate screening machine is used; In the comparison group 3, a certain multifunctional sand and aggregate screening machine with heating function is used; In the comparison group 4, a certain multifunctional sand and aggregate screening machine with dust removal function is used; The implementation group 1 is the equipment provided by the application, which is used for screening the coarse aggregate (aggregate processing system and powder processing system).

[0047] In this embodiment, the theoretical optimum water-binder ratio of the laboratory is 0.16, so 0.16 is taken as the target water-binder ratio in the bulk production of the construction site mixing station. All CA coarse aggregates are screened according to the six grades of particle size proposed in the application. After screening, the water content and silt content of all CA coarse aggregates are calculated.

[0048] From the data in Table 2, it can be seen that if the water content of the aggregate itself in the comparison group 2 is not dried, it will seriously affect the water-binder ratio in the CA-UHPC mixture (the water content increases from 0.1% to 2.5%, the water-binder ratio changes from the original 0.1607 to 0.1784, and the fluctuation range of the water-binder ratio is up to 11%), which seriously affects the stability of the material; in the comparison group 3, although the aggregate is dried, it is not effectively dusted, and the silt content is seriously over-standard (usually the silt content of the aggregate is required to be ≯0.5%), which will affect the strength of the concrete, and the mixing of the soil will greatly reduce the durability of the CA-UHPC material; from the comparison group 4, it can be seen that the screening machine only has the dust removal function but does not have the drying function, and due to the high water content, the silt adheres to the surface of the coarse particles and cannot achieve the dust removal purpose. Therefore, only the integrated machine with the functions of drying, dust removal and fine screening can effectively control the stability of the material, and then ensure the absolute accuracy of the mixture ratio.

[0049] Example 3: Comparison of water content index and performance.

[0050] In this embodiment, the CA-UHPC manufactured by using the grading and CA production method provided by the application and the water content index and performance of the CA-UHPC in other comparison groups are compared, which are shown in Table 3.

[0051] Among them, the comparison group 1 uses a certain roller type sand and stone aggregate screening machine; The comparison group 2 uses a certain vibrating screen type sand and stone aggregate screening machine; The comparison group 3 uses a certain multifunctional sand and stone aggregate screening machine with heating function; The implementation groups 1-6 are the equipment provided by the application, which is used for screening the coarse aggregate (aggregate processing system and powder processing system).

[0052] The sand in all cases in Table 3 is natural medium-coarse river sand produced in Nanjing, with a density (2477 kg / m 3), fineness modulus 3.3. The coarse aggregate used is crushed basalt. The mix proportion of the CA-UHPC of the comparative groups 1-3 and the implementation groups 1-3 is the mix proportion in Table 1, and the CA coarse aggregate grading selected is: 20 kg 0~0.075 mm sand, 30 kg 0.075~0.2 mm sand, 50 kg 0.2~0.4 mm sand, 150 kg 0.4~0.6 mm sand, 100 kg 0.6~1.18 mm sand, 200 kg 1.18~2.36 mm sand, 150 kg 2.36~4.75 mm sand, 150 kg 4.75~7.1 mm coarse aggregate, 300 kg 7.1~9.5 mm coarse aggregate. The mix proportion of the CA-UHPC of the implementation groups 4-6 is the mix proportion in Table 1, and the CA coarse aggregate grading selected is the coarse aggregate grading in the claims of the present application. Among them, the water content is calculated with reference to the standard “Standard for Quality and Test Methods of Sand and Stone for Ordinary Concrete” (JGJ 52-2006), and the performance indicators slump spread (mm), compressive strength (MPa), flexural strength (MPa), and elastic modulus (GPa) are tested and calculated with reference to the standards “Test Code for Cement and Cement Concrete in Highway Engineering” (JTG E30-2005), “Technical Requirements for Ultra High Performance Concrete (UHPC)” (T / CECS 10107-2020), and “Standard Test Methods for Physical and Mechanical Properties of Concrete” (GBT 50081-2019).

[0053] From the data of the comparative groups 1-3 and the implementation groups 1-3 in Table 3, when the sandstone aggregate screening method is the only variable, the water content of the implementation groups 1-3 using the sandstone aggregate screening method provided by the present application is significantly reduced. The average water content of the comparative groups 1-3 is 2.67%, and the water content of the implementation groups 1-3 is reduced by 43.82%, 51.37%, and 43.82%, respectively. The average compressive strength of the comparative groups 1-3 is 158.00 MPa, and the compressive strength of the implementation groups 1-3 is increased by 4.18%, 6.39%, and 3.99%, respectively. The average flexural strength of the comparative groups 1-3 is 21.57 MPa, and the flexural strength of the implementation groups 1-3 is increased by 14.51%, 15.44%, and 11.73%, respectively. The average elastic modulus of the comparative groups 1-3 is 52.2 GPa, and the elastic modulus of the implementation groups 1-3 is increased by 4.98%, 5.56%, and 4.21%, respectively.

[0054] As can be seen from the data of the implementation groups 1-3 and 4-6 in Table 3, when the gradation of the coarse aggregate is the only variable, the water content of the sandstone aggregate is further reduced using the CA coarse aggregate particle size provided by the application, and thus the error of the water-binder ratio of the CA-UHPC from the target value is further reduced. The average water content of the implementation groups 1-3 is 1.43%, and the water content of the implementation groups 4-6 is reduced by 44.05%, 37.06%, and 30.06%, respectively; similarly, the average compressive strength of the implementation groups 1-3 is 165.67 MPa, and the compressive strength of the implementation groups 4-6 is increased by 4.30%, 4.85%, and 1.47%, respectively; the average flexural strength of the implementation groups 1-3 is 24.56 MPa, and the flexural strength of the implementation groups 4-6 is increased by 4.23%, 4.64%, and 1.38%, respectively. In addition, the elastic modulus values of the implementation groups 1-3 and 4-6 are close.

[0055] Example 4: Comparison experiment of silt content index and performance

[0056] In this example, the silt content index and the performance of the CA-UHPC in the implementation groups 1-3 and 4-6 manufactured using the gradation and CA production method provided by the application and other comparative groups are compared, as shown in Table 4.

[0057] Among them, the comparative group 1 uses a certain roller-type sandstone aggregate screening machine; The comparative group 2 uses a certain vibrating screen-type sandstone aggregate screening machine; The comparative group 3 uses a certain multifunctional sandstone aggregate screening machine with heating function; The comparative group 4 uses a certain multifunctional sandstone aggregate screening machine with dust removal function.

[0058] The implementation groups 1-2 are the coarse aggregate screening part of the equipment provided by the application (aggregate processing system and powder processing system).

[0059] The sand of all cases in Table 4 is the same as Example 3, and the coarse aggregate used is crushed granite. The mix proportion of CA-UHPC of comparative groups 1-4 and implementation group 1 in Table 4 is the same as that in Table 1, and the CA coarse aggregate grading selected is: 20 kg of 0-0.075 mm sand, 30 kg of 0.075-0.2 mm sand, 50 kg of 0.2-0.4 mm sand, 150 kg of 0.4-0.6 mm sand, 100 kg of 0.6-1.18 mm sand, 200 kg of 1.18-2.36 mm sand, 150 kg of 2.36-4.75 mm sand, 150 kg of 4.75-7.1 mm coarse aggregate, and 300 kg of 7.1-9.5 mm coarse aggregate. The mix proportion of CA-UHPC of implementation group 2 is the same as that in Table 1, and the CA coarse aggregate grading selected is the coarse aggregate grading in Example 1. The mud content and the test and calculation method of the performance indicators of the CA-UHPC are the same as those in Example 3.

[0060] As can be seen from the data of comparative groups 1-4 and implementation group 1 in Table 4, when the sandstone aggregate screening method is the only variable, the mud content of implementation group 1 using the sandstone aggregate screening method provided by the application decreases significantly. The mud content of comparative group 1 is compared with the different forms of sandstone aggregate screening machines in comparative groups 1-4, and the mud content decreases by 60.53%, 57.14%, 68.09%, and 54.55%, respectively. Similarly, the compressive strength of implementation group 1 is increased by 18.82%, 15.16%, 24.78%, and 13.56% compared with the compressive strength of comparative groups 1-4, respectively. The flexural strength of implementation group 1 is increased by 7.69%, 6.25%, 10.70%, and 4.39% compared with the flexural strength of comparative groups 1-4, respectively. The elastic modulus of implementation group 1 is increased by 3.00%, 3.00%, 4.97%, and 1.87% compared with the elastic modulus of comparative groups 1-4, respectively.

[0061] As can be seen from the data of implementation group 1 and implementation group 2 in Table 4, on the basis of using the sandstone screening machine and method designed by the application, and using the CA coarse aggregate particle size of the CA-UHPC proposed by the application, the mud content of the sandstone aggregate will further decrease, and the performance parameters of the CA-UHPC will be further improved. For example, compared with implementation group 1, the mud content of implementation group 2 is reduced by 20.00%, and the compressive strength is increased by 5.70%.

[0062] Example 5: Performance comparison experiment of different mix proportions

[0063] In this example, the particle size of the CA coarse aggregate is further taken as a variable to verify the performance of the CA grading and production method provided by the application in different CA-UHPC mix proportions. The CA-UHPC mix proportions involved in this example are shown in Table 5.

[0064] The performance of CA-UHPC with different mixing ratios is shown in Table 6. In Table 6, the mixing ratio used by Comparative Group 1 and Implementation Group 1 is mixing ratio 1 in Table 5, and the CA grading used by Comparative Group 1 is 15 kg of 0-0.075 mm sand, 25 kg of 0.075-0.2 mm sand, 40 kg of 0.2-0.4 mm sand, 140 kg of 0.4-0.6 mm sand, 95 kg of 0.6-1.18 mm sand, 190 kg of 1.18-2.36 mm sand, 145 kg of 2.36-4.75 mm sand, 150 kg of 4.75-7.1 mm coarse aggregate, and 300 kg of 7.1-9.5 mm coarse aggregate; the mixing ratio used by Comparative Group 2 and Implementation Group 2 is mixing ratio 2 in Table 5, and the CA grading used by Comparative Group 2 is 50 kg of 0-0.2 mm sand, 50 kg of 0.2-0.4 mm sand, 150 kg of 0.4-0.6 mm sand, 100 kg of 0.6-1.18 mm sand, 200 kg of 1.18-2.36 mm sand, 140 kg of 2.36-4.75 mm sand, 150 kg of 4.75-7.1 mm coarse aggregate, and 300 kg of 7.1-9.5 mm coarse aggregate; the mixing ratio used by Comparative Group 3 and Implementation Group 3 is mixing ratio 3 in Table 5, and the CA grading used by Comparative Group 3 is 50 kg of 0-0.2 mm sand, 50 kg of 0.2-0.4 mm sand, 150 kg of 0.4-0.6 mm sand, 100 kg of 0.6-1.18 mm sand, 180 kg of 1.18-2.36 mm sand, 140 kg of 2.36-4.75 mm sand, 150 kg of 4.75-7.1 mm coarse aggregate, and 300 kg of 7.1-9.5 mm coarse aggregate. The CA grading used by all the implementation groups in Table 6 is the CA grading provided in Example 1 of the present application.

[0065] As can be seen from the data of Comparative Group 1 and Implementation Group 1 in Table 4, on the basis of using the sandstone screening machine and method designed by the present application, and using the CA coarse aggregate particle size of the CA-UHPC proposed by the present application, the compressive strength of the CA-UHPC is increased by 7.66%, the flexural strength is increased by 5.23%, and the elastic modulus is increased by 5.23%. 16.92% Similarly, as can be seen from the data of Comparative Group 2 and Implementation Group 2 in Table 4, using the technical solution of the present application, the compressive strength of the CA-UHPC is increased by 19.1%, the flexural strength is increased by 3.06%, and the elastic modulus is increased by 3.06%. 9.63% Similarly, as can be seen from the data of Comparative Group 3 and Implementation Group 3 in Table 4, using the technical solution of the present application, the compressive strength of the CA-UHPC is increased by 14.68%, the flexural strength is increased by 5.23%, and the elastic modulus is increased by 5.23%.12.98% Elasticity modulus is improved by 3.38%.

[0066] Example 6: Comparative experiment of technical indexes of CA-UHPC material

[0067] The CA-UHPC material of the present application is compared with the CA-UHPC material used in the completed projects (a certain bridge in Nanjing, a certain bridge in Guizhou, a certain bridge in Shanghai) in this example. All performance indexes are tested according to national standards. The results obtained by the test are shown in Table 7. It can be seen from the comprehensive comparison of the parameters in this example that the comprehensive performance of the material used in this example is more comprehensive in the scene with higher requirements for actual compressive strength, elasticity modulus, bending tensile strength, etc.

[0068] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, but not to limit them. Although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing examples, or make equivalent substitutions for part or all of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A CA-UHPC material, comprising the following raw materials in parts by weight: 500-700 parts cement 150-250 parts silica fume 150-300 parts fly ash 0-100 parts of mineral powder 0-70 parts limestone powder 0-50 parts of metakaolin 0~0.075mm sand 0-50 parts 50-150 parts of 0.075~0.2mm sand 100-200 parts of 0.2~0.4mm sand 100-250 parts of 0.4~0.6mm sand 50-200 parts of 0.6~1.18mm sand 0-200 parts of 1.18~2.36mm sand 0-150 parts of 2.36~4.75mm sand 150-250 parts of 4.75~7.1mm aggregate 150-250 parts of 7.1~9.5mm aggregate.

2. The CA-UHPC material according to claim 1, wherein the material further comprises steel fibers, additives, and water.

3. The CA-UHPC material according to claim 1, wherein the weight fraction of each raw material is: 600 parts of cement 200 parts silica fume 120 parts fly ash 60 parts of mineral powder 40 parts limestone powder 30 parts of metakaolin 20 parts of 0~0.075mm sand 50 parts of 0.075~0.2mm sand 80 parts of 0.2~0.4mm sand 200 parts of 0.4~0.6mm sand 200 parts of 0.6~1.18mm sand 100 parts of sand with a diameter of 1.18~2.36mm 50 parts of sand with a diameter of 2.36~4.75mm 250 parts of 4.75~7.1mm aggregate 200 parts of 7.1~9.5mm aggregate.

4. A preparation process for the CA-UHPC material according to claim 1, comprising the following steps: Coarse aggregate treatment: The coarse aggregate is continuously dried at high temperature and then cooled by cold air. The treated aggregate is then shaped. The coarse aggregate is subjected to a probability screening once, producing three grades of material: >8, 8~6.5, and 6.5~5 / 4.75 / 4.5 / 4.25 / 4 mm. The aggregate smaller than 5 / 4.75 / 4.5 / 4.25 / 4 mm is subjected to a second air screening, producing four grades of ultra-fine material: 4.75~2.36, 2.36~1.18, 1.18~0.600, and <0.

600. The ultra-fine aggregate smaller than 0.600 mm is then subjected to a third gyratory screening, producing four grades of extremely fine material: 0.600~0.425, 0.425~0.212, 0.212~0.075, and 0.075~0. Fine aggregate treatment: The fine aggregate is continuously dried at high temperature and then cooled by cold air. The treated aggregate is then shaped. Fine aggregates are subjected to a single air sieve to produce four grades of ultra-fine aggregates: 4.75~2.36, 2.36~1.18, 1.18~0.600, and <0.

600. Ultra-fine aggregates smaller than 0.600 mm are subjected to a second gyratory sieve to produce four grades of extremely fine aggregates: 0.600~0.425, 0.425~0.212, 0.212~0.075, and 0.075~0. The coarse and fine aggregates are mixed to obtain a premix. Water and admixtures are added to it according to the mix design requirements, and the mixture is stirred by frequency conversion for 3-4 minutes. Fiber is then added to it and stirred for 1.5-3 minutes to obtain CA-UHPC.

5. The preparation process of CA-UHPC material according to claim 4, wherein the primary probability sieving of the coarse aggregate uses a 9.5~7.1~5.5 / 5 / 4 three-layer sieve, the secondary air sieving of the coarse aggregate uses a 4.75~2.36~1.18~0.600 four-layer sieve, the tertiary gyratory sieving of the coarse aggregate uses a 0.600~0.425~0.212~0.075 four-layer sieve, the primary air sieving of the fine aggregate uses a 4.75~2.36~1.18~0.600 four-layer sieve, and the secondary gyratory sieving of the fine aggregate uses a 0.600~0.425~0.212~0.075 four-layer sieve.

6. The preparation process of CA-UHPC material according to claim 4, wherein the fiber is one or more of steel fiber, basalt fiber, plant fiber, glass fiber, and carbon fiber.

7. The preparation process of CA-UHPC material according to claim 4, wherein the additive is one or more of mineral admixtures, rheology modifiers, shrinkage inhibitors, interface modifiers, air-entraining agents, and water-reducing agents.

8. An apparatus for preparing the CA-UHPC material of claim 1, comprising an aggregate processing system, a powder processing system, and a mixing system, wherein: The aggregate processing system consists of a feeding platform, an aggregate drying channel, a dust removal system, an aggregate shaping system, an aggregate lifting device, a screening system, and an aggregate storage tank. The aggregate drying channel is connected to the feeding platform and the dust removal system at both ends, respectively. The aggregate lifting device is connected to the dust removal system through the aggregate shaping system, and the other end of the aggregate lifting device is connected to the screening system. The lifted aggregate falls into the screening system for screening, and the screening system is connected to the aggregate storage tank through several channels. The powder processing system consists of a powder raw material lifting device and a powder storage tank. The powder raw material lifting device is connected to the powder storage tank to transfer the powder into the powder storage tank. The mixing system includes a premixing device, which is connected to an aggregate storage tank and a powder storage tank. A certain amount of aggregate and powder enter the premixing device, are mixed, and then output.

9. The equipment according to claim 8 further includes a control system, wherein the control system is connected to the aggregate processing system, the powder processing system, and the mixing system.

10. The equipment according to claim 8, wherein the mixing system further includes a packaging system, the packaging system being connected to the premixing system and consisting of a sealing device and a transfer device, wherein a certain amount of aggregate and powder enters the premixing device for mixing, then enters the sealing device for packaging and sealing, and is transferred out of the packaging system by the transfer device.

11. The application of the CA-UHPC material according to claim 1 in road pavement, airport pavement, and bridge deck.

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