Yellow river sand UHPC and preparation process thereof

Abstract

The invention discloses Yellow River sand UHPC (Ultra High Performance Concrete) and a preparation process thereof. The Yellow River sand UHPC is prepared from Portland cement, a defoaming agent, mixed sand, a high-activity admixture, a water reducing agent and fibers. The Yellow River sand is adopted to manufacture the UHPC, and the UHPC has the performance advantages of high strength, high toughness and high durability, so that Yellow River sand resources can be fully utilized, the problem of shortage of river sand resources can be solved, resources and energy can be saved, and the ecological environment of the Yellow River basin can be protected. According to the Yellow River sand UHPC manufacturing process, the Yellow River sand is modified, the defect that the Yellow River sand is low in strength is overcome, the grain composition of the Yellow River sand is optimized and the fluidity of the UHPC is improved by adding the mineral admixture, and different grades of UHPC can be produced according to needs by adjusting the proportion matching of the quartz sand and the machine-made sand which are the same in composition and different in strength. The method has the advantages of short research and development period, low time consumption of production ingredients, good quality control, high production efficiency and low cost.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials, and more specifically, to a Yellow River sand UHPC and a preparation process thereof. Background Art

[0003] At present, Yellow River sand is mainly used to replace machine-made sand in various proportions to prepare concrete raw materials, such as UHPC. UHPC (Ultra-High Performance Concrete) components have been vigorously developed in recent years due to their excellent mechanical properties, durability, applicability and economy. It is one of the important fixed materials for construction in component systems. It is a high-performance fluid mortar composed of high-performance cementitious materials, early strength aggregates, functional admixtures and additives, with the characteristics of ultra-high fluidity, ultra-high strength and ultra-high durability.

[0004] However, Yellow River sand is a very fine sand, with a fineness of about 0.15-0.3mm, a relatively simple gradation, and a mud content of 6%-20%, far below the 2% technical specification required by the national standard. For untreated Yellow River sand, there are the following disadvantages: The disadvantages of Yellow River sand concrete mainly include unreasonable gradation, large mud content, low strength, high impurity content, water-absorbing adsorption admixtures, etc. Directly using Yellow River sand as a concrete raw material will greatly reduce the quality and strength of the concrete and shorten the service life of the project.

[0005] The existing technology lacks pretreatment or insufficient pretreatment of the Yellow River sand, resulting in a low amount of Yellow River sand used in a single UHPC, the need to use a large amount of other high-quality materials, and difficulty in producing UHPC with excellent performance.

[0006] In view of the above situation, how to utilize the Yellow River sand as a resource with higher value has become a research topic for many building materials researchers. Summary of the invention

[0007] The invention discloses a Yellow River sand UHPC, which comprises the following raw materials calculated by weight: 30-46 parts by weight of Portland cement, 0.08-0.26 parts by weight of a defoamer, 38-46 parts by weight of mixed sand, 14-38 parts by weight of a high-activity admixture, 0.2-0.7 parts by weight of a water reducer, and 1-8 parts by weight of fiber.

[0008] Preferably, the mixed sand is prepared by compounding pretreated Yellow River sand, graded quartz sand and graded machine-made sand;

[0009] The gradation ratio of the pretreated Yellow River sand is 1.18-2.36 mm: 1.18-0.1 mm = 1: (0.2-0.3), and the fineness modulus is 0.8;

[0010] The graded quartz sand is composed of quartz sand with a particle size range of 0.1 to 4.75 mm, and the grading ratio is 2.36 to 4.75 mm: 1.18 to 2.36 mm: 1.18 to 0.1 mm = 1: (2.8 to 3.2): (0.5 to 1), and the fineness modulus is 2.3 to 3.1;

[0011] The graded machine-made sand is composed of sand with a particle size range of 0.1-4.75 mm, a gradation ratio of 2.36-4.75 mm: 1.18-2.36 mm: 1.18-0.1 mm = 1: (2.8-3.2): (0.5-1), and a fineness modulus of 2.3-3.1.

[0012] Preferably, the silica content of the quartz sand is ≥90%, the mud content is ≤0.5%, and the crushing value is ≤10.

[0013] Preferably, the crushing value of the graded machine-made sand is ≤15, and the mud content is ≤0.5%.

[0014] Preferably, the high-activity admixture is S105 mineral powder, SF90 silica ash or Class I fly ash; and the water reducer is TH-928 polycarboxylate water reducer with a water reduction rate of ≥40%.

[0015] Preferably, the fibers are steel fibers or polyvinyl alcohol fibers.

[0016] A preparation process of Yellow River sand UHPC includes the following steps:

[0017] Step S1: sieving the Yellow River sand to remove impurities;

[0018] First, the Yellow River sand is washed, and then screened through a 0.075mm sieve to remove impurities and obtain dry sand with a mud content of less than 0.3%;

[0019] Step S2: high temperature burning;

[0020] The Yellow River sand is fully burned with natural gas at high temperature, and the temperature is controlled between 850 and 1500°C;

[0021] Step S3: preparing modified Yellow River sand;

[0022] Yellow River sand, bentonite, sodium thiosulfate, polymerized polyol and silane coupling agent are treated by homogenization, high pressure heating and cyclone dust collector to obtain modified Yellow River sand;

[0023] Step S4: adding mineral admixtures;

[0024] Adding graded mineral admixtures to the modified Yellow River sand, wherein the mineral admixtures are one or more of lithium slag, modified limestone powder, limestone powder, zeolite powder, kaolin, rice husk ash, glass microbeads or ceramic micropowder;

[0025] Step S5: compounding the mixed sand;

[0026] Mixing Yellow River sand, graded machine-made sand and graded quartz sand treated and added with mineral admixtures in a certain proportion to prepare mixed sand;

[0027] Step S6: preparing UHPC;

[0028] The silicate cement, mixed sand, high-activity admixture and water reducer are pre-dry mixed using a fixed-speed forced mixer, and then water, defoamer and other liquid materials are added for wet mixing, and then the fiber is added and stirred evenly to obtain the UHPC mixture; the total mixing time is controlled between 5 and 15 minutes.

[0029] Preferably, in step S6, the stirring process includes the following steps:

[0030] First, medium-speed dry mixing of Portland cement, mixed sand, highly reactive admixtures and water reducer is used for 0.5 to 2 minutes;

[0031] Then, add two-thirds of the water and all the water reducer, and stir until the mixture is dough-like;

[0032] Next, add the remaining water and stir rapidly for 1 to 2 minutes until the gelling material and admixture are fully dispersed and mixed evenly;

[0033] Afterwards, stir slowly and add the fibers evenly at the same time. After all the fibers are added, stir slowly for 1 to 3 minutes.

[0034] Preferably, in step S6, the stirring process includes the following steps:

[0035] First, dry mix the Portland cement, mixed sand, highly active admixture and water reducer for 1 to 2 minutes;

[0036] Then, add water, defoamer and other liquid materials for wet mixing. The wet mixing time should not be less than 5 minutes, until the mixture is close to the target fluidity;

[0037] After that, slowly add the fibers. After all the fibers are added, continue stirring for at least 2 minutes until the fibers are evenly dispersed in the mixture.

[0038] Preferably, in step S3, the temperature of high pressure heating is controlled between 220 and 360° C., and the pressure is controlled between 12 and 20 MPa.

[0039] The Yellow River sand UHPC of the present invention is prepared from silicate cement, defoamer, mixed sand, high-activity admixture, water reducing agent and fiber; by using Yellow River sand to make UHPC, and having the performance advantages of high strength, high toughness and high durability, it can not only make full use of Yellow River sand resources, but also solve the problem of scarce river sand resources, which is beneficial to saving resources and energy, and protecting the ecological environment of the Yellow River Basin. The Yellow River sand UHPC production process of the present invention solves the disadvantage of low strength of Yellow River sand by modifying Yellow River sand, and the addition of mineral admixture optimizes the particle gradation of Yellow River sand and improves the fluidity of UHPC. By adjusting the proportion of quartz sand and machine-made sand with the same grading and different strengths, UHPC of different grades can be produced according to needs, which has the advantages of short R&D cycle, less time-consuming production and batching, good quality control, high production efficiency and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0041] Figure 1 The figure is a schematic diagram of the process of a Yellow River sand UHPC and its preparation process according to the present invention. DETAILED DESCRIPTION

[0042] The present invention discloses a Yellow River sand UHPC and a preparation process thereof. The UHPC is made of Yellow River sand and has the performance advantages of high strength, high toughness and high durability, which can not only make full use of the Yellow River sand resources, but also protect the ecological environment of the Yellow River Basin. The Yellow River sand treated by the preparation process can improve the fluidity and strength of UHPC, meet the high-performance construction requirements, and reflect the application value of the Yellow River sand resources. The application field is broad, including industrial and civil construction, municipal administration, bridges and tunnels, oceans and other environments.

[0043] The following is a clear and detailed description of the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] The invention discloses a Yellow River sand UHPC, which comprises the following raw materials calculated by weight: 30-46 parts by weight of Portland cement, 0.08-0.26 parts by weight of a defoamer, 38-46 parts by weight of mixed sand, 14-38 parts by weight of a high-activity admixture, 0.2-0.7 parts by weight of a water reducer, and 1-8 parts by weight of fiber.

[0045] UHPC (Ultra-High Performance Concrete) is ultra-high performance concrete. UHPC has extremely high compressive strength, tensile strength and excellent durability, and can maintain stable performance in various extreme environments. High strength: The compressive strength of UHPC can usually reach more than 150MPa, which is much higher than the compressive strength of ordinary concrete. This means that structures built with UHPC can withstand greater pressure and load, greatly improving the safety and stability of the structure. High durability: Due to the dense microstructure of UHPC, its impermeability, freeze-thaw resistance, chemical corrosion resistance and other properties are better than ordinary concrete. This enables UHPC to maintain good performance for a long time in harsh natural environments and extend the service life of the structure. High toughness: By adding steel fibers or synthetic fibers, the tensile strength of UHPC has been significantly improved. This enables UHPC to show better ductility and toughness when subjected to external forces, reducing the risk of structural damage due to brittle fracture. Excellent working performance: UHPC has good fluidity, is easy to cast and form, and has a fast hardening speed, shortening the construction period. At the same time, the self-compacting property of UHPC allows it to achieve a high density without vibration, which improves construction efficiency. UHPC and its components have been vigorously developed in recent years due to their excellent mechanical properties, durability, applicability and economy, and are one of the important fixing materials for construction in high-performance component systems.

[0046] The Yellow River sand UHPC of the present invention makes its microstructure more compact by precisely controlling the proportions of various raw materials, thereby improving its mechanical properties. The addition of high-activity admixtures optimizes the particle grading of the mixed sand, achieves the most effective filling effect, and is beneficial to improving the fluidity of UHPC. In addition, the addition of water reducers reduces the water-cement ratio and improves the strength and durability of UHPC. By introducing fibers, the tensile strength and toughness of UHPC are improved. These fibers form a stable three-dimensional network structure in UHPC, which effectively prevents the expansion and extension of cracks. Compared with UHPC premixes prepared with traditional single-category sand and traditional conventional admixtures, the working performance, mechanical properties and durability of the Yellow River sand UHPC of the present invention are significantly improved.

[0047] Preferably, the mixed sand is prepared by compounding pretreated Yellow River sand, graded quartz sand and graded machine-made sand; the grading ratio of the pretreated Yellow River sand is 1.18-2.36 mm: 1.18-0.1 mm = 1: (0.2-0.3), and the fineness modulus is 0.8; the graded quartz sand is composed of quartz sand with a particle size range of 0.1-4.75 mm, and its grading ratio is 2.36-4.75 mm: 1.18-2.36 mm: 1.18-0.1mm = 1: (2.8-3.2): (0.5-1), the fineness modulus is 2.3-3.1; the graded machine-made sand is composed of sand with a particle size range of 0.1-4.75mm, and its grading ratio is 2.36-4.75mm: 1.18-2.36mm: 1.18-0.1mm = 1: (2.8-3.2): (0.5-1), and the fineness modulus is 2.3-3.1. The traditional mode is to produce different grades of premixes by adjusting the proportion of different admixtures, the proportion of cement dosage and admixtures, the proportion of ultra-fine sand and medium-grade sand (such as quartz sand), and the proportion of admixtures and cementitious materials (cement, admixtures). This has the disadvantages of long research and development time, long production and batching time, low quality control and production efficiency, and high cost. In this embodiment, UHPC of different grades can be produced by adjusting the proportion of intermediate sand (quartz sand and machine-made sand) of the same gradation but different costs.

[0048] Preferably, the silica content of the quartz sand is ≥90%, the mud content is ≤0.5%, and the crushing value is ≤10.

[0049] Preferably, the crushing value of the graded machine-made sand is ≤15, and the mud content is ≤0.5%.

[0050] Preferably, the high-activity admixture is S105 mineral powder, SF90 silica ash or Class I fly ash; and the water reducer is TH-928 polycarboxylate water reducer with a water reduction rate of ≥40%.

[0051] Preferably, the fibers are steel fibers or polyvinyl alcohol fibers.

[0052] A preparation process of Yellow River sand UHPC includes the following steps:

[0053] Step S1: sieving the Yellow River sand to remove impurities;

[0054] The Yellow River sand is first washed, then screened with a 0.075mm sieve to remove impurities and obtain dry sand with a mud content of less than 0.3%; this step can remove some soluble impurities, some light materials with a density less than water and most of the mud, and most of the soluble harmful compounds.

[0055] Step S2: high temperature burning;

[0056] The Yellow River sand is fully burned with natural gas at high temperature, and the temperature is controlled between 850 and 1500°C; high-temperature burning is beneficial to remove most impurities and a small amount of harmful compounds.

[0057] Step S3: preparing modified Yellow River sand;

[0058] Yellow River sand, bentonite, sodium thiosulfate, polymerized polyol and silane coupling agent are treated by homogenization, high-pressure heating and cyclone dust collector to obtain modified Yellow River sand; through this step, the morphology of Yellow River sand particles can be effectively improved, the strength of Yellow River sand particles can be increased, and most of the light material impurities can be removed.

[0059] Step S4: adding mineral admixtures;

[0060] Graded mineral admixtures are added to the modified Yellow River sand, and the mineral admixtures are one or more of lithium slag, modified limestone powder, limestone powder, zeolite powder, kaolin, rice husk ash, glass beads or ceramic powder; the addition of mineral admixtures optimizes the particle grading of the Yellow River sand and achieves the most effective filling effect. At the same time, the lubricating effect of the mineral composition and particle morphology of some mineral admixtures can further improve the fluidity of UHPC.

[0061] Step S5: compounding the mixed sand;

[0062] Mixing Yellow River sand, graded machine-made sand and graded quartz sand treated and added with mineral admixtures in a certain proportion to prepare mixed sand;

[0063] Step S6: preparing UHPC;

[0064] The silicate cement, mixed sand, high-activity admixture and water reducer are pre-dry mixed using a fixed-speed forced mixer, and then water, defoamer and other liquid materials are added for wet mixing, and then the fiber is added and stirred evenly to obtain the UHPC mixture; the total mixing time is controlled between 5 and 15 minutes.

[0065] The existing technology for the application of Yellow River sand in UHPC mainly replaces machine-made sand with various proportions of Yellow River sand to prepare UHPC. Yellow River sand is a very fine sand with a fineness of about 0.15 to 0.3 mm, a relatively simple gradation, and a mud content of 6% to 20%, which is far from the 2% technical specification required by the national standard. In addition, the strength of Yellow River sand is low and the impurity content is high. Using Yellow River sand as a concrete raw material will greatly reduce the quality and strength of the concrete and shorten the service life of the project.

[0066] In this preparation process, the Yellow River sand is pretreated and improved to address the above shortcomings of the Yellow River sand, and then the improved Yellow River sand is made into UHPC with excellent performance. This improves the existing technology and realizes the resource utilization of the Yellow River sand to solve environmental problems. Specifically:

[0067] In response to the problem of unreasonable gradation of Yellow River sand: the gradation of Yellow River sand is relatively simple, which means that its particle size distribution is uneven, affecting the homogeneity and strength of concrete. This preparation process adopts screening and then adds mineral admixtures for improvement.

[0068] Yellow River sand has a high mud content: Yellow River sand has a high mud content, generally between 6% and 20%, while the relevant standards require that the mud content should not exceed 3%. High mud content will increase the water absorption of concrete and may affect the solidification and hardening process of concrete. Most of the mud can be effectively removed by washing.

[0069] The strength of Yellow River sand is low: Due to the low strength of Yellow River sand, the strength of concrete made from it will also be reduced accordingly, affecting the bearing capacity and durability of the building structure. This preparation process uses high-temperature burning to remove insoluble organic matter from impurities, washing to remove soluble impurities, and air separation to remove light materials and then remove the low-strength parts of the sand. Modifiers such as coupling agents increase the strength of sand and improve the adhesion of the sand surface.

[0070] Yellow River sand contains many impurities: Yellow River sand contains many impurities, which will affect the uniformity and stability of concrete and reduce the quality of concrete. Therefore, this preparation process removes insoluble organic matter from impurities by high temperature, removes soluble impurities by washing, and removes insoluble and high temperature resistant light material impurities by air separation.

[0071] Water absorption and adsorption of admixtures: Yellow River sand has strong water absorption and may absorb admixtures in concrete, affecting the effect of admixtures and further affecting the performance of concrete. After the preparation process uses washing and high temperature treatment to remove impurities and volatile compounds, the adsorption of Yellow River sand to admixtures is greatly reduced. At the same time, the particles of the modified Yellow River sand are more rounded and the fluidity is further increased, which greatly reduces its water absorption.

[0072] In general, the preparation process is improved mainly in the following three aspects:

[0073] First, modify the Yellow River sand to improve its strength and particle morphology, and solve the disadvantage of low strength of the Yellow River sand. In this preparation process, the silane coupling agent has two groups with different properties. Different groups can react with chemical groups on the surfaces of different materials (such as glass, fly ash and other silicon-containing materials) to form strong chemical bonds. Even the organophilic groups can react or physically entangle with organic molecules, thereby achieving chemical bonding at the interface between organic and inorganic materials and greatly improving the bonding strength. Compared with the unsoaked Yellow River sand soaked in an active agent with silane coupling agent KH-570 as the main ingredient, the strength can be increased by 12 to 28.

[0074] Secondly, the use of mineral admixtures can optimize and improve the gradation of modified Yellow River sand. The addition of mineral admixtures optimizes the particle gradation of Yellow River sand and achieves the most effective filling effect. At the same time, the lubrication effect of the mineral composition and particle morphology of some mineral admixtures can further improve the fluidity of UHPC.

[0075] Finally, the three types of sand are used in combination to quickly and easily adjust the strength grade of UHPC. This preparation process only needs to adjust the proportion of intermediate sand (such as quartz sand, machine-made sand) of the same grading and different strengths to produce different grades of UHPC. The traditional model is to produce different grades of UHPC by adjusting the proportion of different admixtures, the proportion of cement dosage and admixtures, the proportion of ultra-fine sand and intermediate sand (such as quartz sand), and the proportion of admixtures and cementitious materials (cement, admixtures). This has the disadvantages of long R&D time, long production and batching time, low quality control and production efficiency, and high cost.

[0076] Compared with the UHPC premix prepared with traditional single-category sand and conventional admixtures, the Yellow River sand UHPC produced by the preparation process of the present invention has significantly improved working performance, mechanical properties and durability.

[0077] It should be pointed out that the use of river sand from other regions to produce and manufacture UHPC has been widely used. However, the reserves of river sand from other regions are not as much as those of the Yellow River sand, and the use of other river sand often damages the ecological environment, while the resource utilization of the Yellow River sand improves the ecological environment. The quality stability of other ultra-fine sands is not as good as that of the Yellow River sand. The frequency of debugging of the compounding process of different production batches is relatively high, and the cost of purchasing raw materials is high. Unmodified ultra-fine sand can be combined with particularly high-quality admixtures to produce high-performance UHPC. The preparation process provided by the present invention is precisely aimed at improving the inherent defects of the Yellow River sand. Using this preparation process, high-quality UHPC can be produced, which greatly alleviates the dilemma of insufficient supply of other river sands, improves the utilization rate of the Yellow River sand mineral resources, and also protects the ecological environment of the Yellow River Basin.

[0078] Preferably, in step S6, the stirring process includes the following steps:

[0079] First, medium-speed dry mixing of Portland cement, mixed sand, highly reactive admixtures and water reducer is used for 0.5 to 2 minutes;

[0080] Then, add two-thirds of the water and all the water reducer, and stir until the mixture is dough-like;

[0081] Next, add the remaining water and stir rapidly for 1 to 2 minutes until the gelling material and admixture are fully dispersed and mixed evenly;

[0082] Afterwards, stir slowly and add the fibers evenly at the same time. After all the fibers are added, stir slowly for 1 to 3 minutes.

[0083] In step S6, the ultra-high performance concrete mixture should be stirred by a forced mixer, and a fixed-speed forced mixer should be used for stirring. The order of adding materials can be adjusted according to the type and dosage of the fiber used. Specifically, the following stirring procedure can be adopted: first, dry-mix cement and other powders at a medium speed for 0.5 to 2 minutes; then add 2 / 3 of the water and all the water reducers, and stir until the mixture is dough-like; then add the remaining water and stir quickly for 1 to 2 minutes until the cementitious material and admixture are fully dispersed and mixed evenly; then, stir slowly and add the fibers evenly at the same time, and stir slowly for 1 to 3 minutes after all the fibers are added. Each stirring time should be appropriately adjusted according to the flow state of the mixture.

[0084] Preferably, in step S6, the stirring process includes the following steps:

[0085] First, dry mix the Portland cement, mixed sand, highly active admixture and water reducer for 1 to 2 minutes;

[0086] Then, add water, defoamer and other liquid materials for wet mixing. The wet mixing time should not be less than 5 minutes, until the mixture is close to the target fluidity;

[0087] After that, slowly add the fibers. After all the fibers are added, continue stirring for at least 2 minutes until the fibers are evenly dispersed in the mixture.

[0088] Preferably, in step S3, the temperature of high pressure heating is controlled between 220 and 360° C., and the pressure is controlled between 12 and 20 MPa.

[0089] The following is described through multiple embodiments:

[0090] Example 1

[0091] Step S1: Yellow River sand is screened to remove impurities; the Yellow River sand is first washed, and then screened through a 0.075 mm sieve to remove impurities to obtain dry sand with a mud content of less than 0.3%; this step can remove some soluble impurities, some light materials with a density less than water and most of the mud, and most of the soluble harmful compounds.

[0092] Step S2: high-temperature burning; the Yellow River sand is fully burned with natural gas at high temperature, and the temperature is controlled between 850 and 1500° C.; high-temperature burning is conducive to removing most impurities and a small amount of harmful compounds.

[0093] Step S3: preparing modified Yellow River sand; subjecting Yellow River sand, bentonite, sodium thiosulfate, polymeric polyol and silane coupling agent to homogenization, high-pressure heating and cyclone dust collector treatment to obtain modified Yellow River sand; through this step, the particle morphology of Yellow River sand can be effectively improved, the particle strength of Yellow River sand can be increased, and most of the light material impurities can be removed.

[0094] Step S4: adding mineral admixtures; adding graded mineral admixtures to the modified Yellow River sand, wherein the mineral admixtures are one or more of lithium slag, modified limestone powder, limestone powder, zeolite powder, kaolin, rice husk ash, glass microbeads or ceramic micropowders; the addition of mineral admixtures optimizes the particle grading of the Yellow River sand and achieves the most effective filling effect. At the same time, the lubricating effect of the mineral composition and particle morphology of some mineral admixtures can further improve the fluidity of UHPC.

[0095] Step S5: Compounding mixed sand: Mixing the Yellow River sand that has been processed and added with mineral admixtures, graded machine-made sand and graded quartz sand in a certain proportion to obtain mixed sand;

[0096] Step S6: preparing UHPC; using a constant speed forced mixer, pre-dry-mixing 30-46 parts by weight of silicate cement, 38-46 parts by weight of mixed sand, 14-38 parts by weight of high-activity admixture, and 0.2-0.7 parts by weight of water reducer, then adding water, 0.08-0.26 parts by weight of defoamer and other liquid materials for wet mixing, and then adding 1-8 parts by weight of fiber and stirring evenly to obtain a UHPC mixture; the total stirring time is controlled between 5 and 15 minutes.

[0097] Embodiment 2:

[0098] Step S1: Yellow River sand is screened to remove impurities; the Yellow River sand is first washed, and then screened through a 0.075 mm sieve to remove impurities to obtain dry sand with a mud content of less than 0.3%; this step can remove some soluble impurities, some light materials with a density less than water and most of the mud, and most of the soluble harmful compounds.

[0099] Step S2: high-temperature combustion; the Yellow River sand is fully burned with natural gas at high temperature, and the temperature is controlled between 850°C; high-temperature combustion is conducive to removing most impurities and a small amount of harmful compounds.

[0100] Step S3: preparing modified Yellow River sand; subjecting Yellow River sand, bentonite, sodium thiosulfate, polymeric polyol and silane coupling agent to homogenization, high-pressure heating and cyclone dust collector treatment to obtain modified Yellow River sand; through this step, the particle morphology of Yellow River sand can be effectively improved, the particle strength of Yellow River sand can be increased, and most of the light material impurities can be removed.

[0101] Step S4: adding mineral admixtures; adding graded mineral admixtures to the modified Yellow River sand, wherein the mineral admixtures are one or more of lithium slag, modified limestone powder, limestone powder, zeolite powder, kaolin, rice husk ash, glass microbeads or ceramic micropowders; the addition of mineral admixtures optimizes the particle grading of the Yellow River sand and achieves the most effective filling effect. At the same time, the lubricating effect of the mineral composition and particle morphology of some mineral admixtures can further improve the fluidity of UHPC.

[0102] Step S5: Compounding mixed sand: Mixing the Yellow River sand that has been processed and added with mineral admixtures, graded machine-made sand and graded quartz sand in a certain proportion to obtain mixed sand;

[0103] Step S6: preparing UHPC; using a constant speed forced mixer, pre-dry-mix 30 parts by weight of Portland cement, 38 parts by weight of mixed sand, 14 parts by weight of high-activity admixture, and 0.2 parts by weight of water reducer, then adding water, 0.08 parts by weight of defoamer and other liquid materials for wet mixing, and then adding 1 part by weight of fiber and stirring evenly to obtain a UHPC mixture; the total stirring time is controlled between 5 minutes.

[0104] Example 3

[0105] Step S1: Yellow River sand is screened to remove impurities; the Yellow River sand is first washed, and then screened through a 0.075 mm sieve to remove impurities to obtain dry sand with a mud content of less than 0.3%; this step can remove some soluble impurities, some light materials with a density less than water and most of the mud, and most of the soluble harmful compounds.

[0106] Step S2: high-temperature combustion; the Yellow River sand is fully burned with natural gas at high temperature, and the temperature is controlled between 1175°C; high-temperature combustion is conducive to removing most impurities and a small amount of harmful compounds.

[0107] Step S3: preparing modified Yellow River sand; subjecting Yellow River sand, bentonite, sodium thiosulfate, polymeric polyol and silane coupling agent to homogenization, high-pressure heating and cyclone dust collector treatment to obtain modified Yellow River sand; through this step, the particle morphology of Yellow River sand can be effectively improved, the particle strength of Yellow River sand can be increased, and most of the light material impurities can be removed.

[0108] Step S4: adding mineral admixtures; adding graded mineral admixtures to the modified Yellow River sand, wherein the mineral admixtures are one or more of lithium slag, modified limestone powder, limestone powder, zeolite powder, kaolin, rice husk ash, glass microbeads or ceramic micropowders; the addition of mineral admixtures optimizes the particle grading of the Yellow River sand and achieves the most effective filling effect. At the same time, the lubricating effect of the mineral composition and particle morphology of some mineral admixtures can further improve the fluidity of UHPC.

[0109] Step S5: Compounding mixed sand: Mixing the Yellow River sand that has been processed and added with mineral admixtures, graded machine-made sand and graded quartz sand in a certain proportion to obtain mixed sand;

[0110] Step S6: preparing UHPC; using a constant speed forced mixer, pre-dry-mixing 38 parts by weight of Portland cement, 42 parts by weight of mixed sand, 26 parts by weight of high-activity admixture, and 0.45 parts by weight of water reducer, and then adding water, 0.17 parts by weight of defoamer and other liquid materials for wet mixing, and then adding 4.5 parts by weight of fiber and stirring evenly to obtain a UHPC mixture; the total stirring time is controlled between 10 minutes.

[0111] Example 4

[0112] Step S1: Yellow River sand is screened to remove impurities; the Yellow River sand is first washed, and then screened through a 0.075 mm sieve to remove impurities to obtain dry sand with a mud content of less than 0.3%; this step can remove some soluble impurities, some light materials with a density less than water and most of the mud, and most of the soluble harmful compounds.

[0113] Step S2: high-temperature burning; the Yellow River sand is fully burned with natural gas at high temperature, and the temperature is controlled between 1500°C; high-temperature burning is conducive to removing most impurities and a small amount of harmful compounds.

[0114] Step S3: preparing modified Yellow River sand; subjecting Yellow River sand, bentonite, sodium thiosulfate, polymeric polyol and silane coupling agent to homogenization, high-pressure heating and cyclone dust collector treatment to obtain modified Yellow River sand; through this step, the particle morphology of Yellow River sand can be effectively improved, the particle strength of Yellow River sand can be increased, and most of the light material impurities can be removed.

[0115] Step S4: adding mineral admixtures; adding graded mineral admixtures to the modified Yellow River sand, wherein the mineral admixtures are one or more of lithium slag, modified limestone powder, limestone powder, zeolite powder, kaolin, rice husk ash, glass microbeads or ceramic micropowders; the addition of mineral admixtures optimizes the particle grading of the Yellow River sand and achieves the most effective filling effect. At the same time, the lubricating effect of the mineral composition and particle morphology of some mineral admixtures can further improve the fluidity of UHPC.

[0116] Step S5: Compounding mixed sand: Mixing the Yellow River sand that has been processed and added with mineral admixtures, graded machine-made sand and graded quartz sand in a certain proportion to obtain mixed sand;

[0117] Step S6: preparing UHPC; using a constant speed forced mixer to pre-dry mix 46 parts by weight of silicate cement, 46 parts by weight of mixed sand, 38 parts by weight of high-activity admixture, and 00.7 parts by weight of water reducer, and then adding water, 0.26 parts by weight of defoamer and other liquid materials for wet mixing, and then adding 8 parts by weight of fiber and stirring evenly to obtain a UHPC mixture; the total stirring time is controlled between 15 minutes.

[0118] The Yellow River sand UHPC of the present invention is prepared from silicate cement, defoamer, mixed sand, high-activity admixture, water reducing agent and fiber; by using Yellow River sand to make UHPC, and having the performance advantages of high strength, high toughness and high durability, it can not only make full use of Yellow River sand resources, but also solve the problem of scarce river sand resources, which is beneficial to saving resources and energy, and protecting the ecological environment of the Yellow River Basin. The Yellow River sand UHPC production process of the present invention solves the disadvantage of low strength of Yellow River sand by modifying Yellow River sand, and the addition of mineral admixture optimizes the particle gradation of Yellow River sand and improves the fluidity of UHPC. By adjusting the proportion of quartz sand and machine-made sand with the same grading and different strengths, UHPC of different grades can be produced according to needs, which has the advantages of short R&D cycle, less time-consuming production and batching, good quality control, high production efficiency and low cost.

[0119] The Yellow River sand UHPC and its preparation process provided by the present invention are introduced in detail above. For those skilled in the art, according to the ideas of the embodiments of the present invention, there may be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A Yellow River sand UHPC, characterized in that: The invention comprises the following raw materials calculated by weight: 30 to 46 parts by weight of silicate cement, 0.08 to 0.26 parts by weight of defoamer, 38 to 46 parts by weight of mixed sand, 14 to 38 parts by weight of high-activity admixture, 0.2 to 0.7 parts by weight of water reducing agent and 1 to 8 parts by weight of fiber.

2. The Yellow River sand UHPC according to claim 1, characterized in that: The mixed sand is prepared by compounding pre-treated Yellow River sand, graded quartz sand and graded machine-made sand; The gradation ratio of the pretreated Yellow River sand is 1.18-2.36 mm: 1.18-0.1 mm = 1: (0.2-0.3), and the fineness modulus is 0.8; The graded quartz sand is composed of quartz sand with a particle size range of 0.1 to 4.75 mm, and the grading ratio is 2.36 to 4.75 mm: 1.18 to 2.36 mm: 1.18 to 0.1 mm = 1: (2.8 to 3.2): (0.5 to 1), and the fineness modulus is 2.3 to 3.1; The graded machine-made sand is composed of sand with a particle size range of 0.1-4.75 mm, a gradation ratio of 2.36-4.75 mm: 1.18-2.36 mm: 1.18-0.1 mm = 1: (2.8-3.2): (0.5-1), and a fineness modulus of 2.3-3.

1.

3. The Yellow River sand UHPC according to claim 2, characterized in that: The silica content of the quartz sand is ≥90%, the mud content is ≤0.5%, and the crushing value is ≤10.

4. The Yellow River sand UHPC according to claim 2, characterized in that: The crushing value of the graded machine-made sand is ≤15, and the mud content is ≤0.5%.

5. The Yellow River sand UHPC according to claim 1, characterized in that: The high-activity admixture is S105 mineral powder, SF90 silica ash or Class I fly ash; the water reducer is TH-928 polycarboxylic acid water reducer with a water reduction rate of ≥40%.

6. The Yellow River sand UHPC according to claim 1, characterized in that: The fiber is steel fiber or polyvinyl alcohol fiber.

7. The process for preparing Yellow River sand UHPC according to any one of claims 1 to 6, characterized in that: The following steps are included: Step S1: sieving the Yellow River sand to remove impurities; First, the Yellow River sand is washed, and then screened through a 0.075mm sieve to remove impurities and obtain dry sand with a mud content of less than 0.3%; Step S2: high temperature burning; The Yellow River sand is fully burned with natural gas at high temperature, and the temperature is controlled between 850 and 1500°C; Step S3: preparing modified Yellow River sand; Yellow River sand, bentonite, sodium thiosulfate, polymeric polyol and silane coupling agent are treated by homogenization, high pressure heating and cyclone dust collector to obtain modified Yellow River sand; Step S4: adding mineral admixtures; Adding graded mineral admixtures to the modified Yellow River sand, wherein the mineral admixtures are one or more of lithium slag, modified limestone powder, limestone powder, zeolite powder, kaolin, rice husk ash, glass microbeads or ceramic micropowder; Step S5: compounding the mixed sand; The Yellow River sand, graded machine-made sand and graded quartz sand which have been processed and added with mineral admixtures are mixed in a certain proportion to prepare mixed sand; Step S6: preparing UHPC; The silicate cement, mixed sand, high-activity admixture and water reducer are pre-dry mixed using a fixed-speed forced mixer, and then water, defoamer and other liquid materials are added for wet mixing, and then the fiber is added and stirred evenly to obtain the UHPC mixture; the total mixing time is controlled between 5 and 15 minutes.

8. The process for preparing Yellow River sand UHPC according to claim 7, characterized in that: In step S6, the stirring process includes the following steps: First, medium-speed dry mixing of Portland cement, mixed sand, highly reactive admixtures and water reducer is used for 0.5 to 2 minutes; Then, add two-thirds of the water and all the water reducer, and stir until the mixture is dough-like; Next, add the remaining water and stir rapidly for 1 to 2 minutes until the gelling material and admixture are fully dispersed and mixed evenly; Afterwards, stir slowly and add the fibers evenly at the same time. After all the fibers are added, stir slowly for 1 to 3 minutes.

9. The process for preparing Yellow River sand UHPC according to claim 7, characterized in that: In step S6, the stirring process includes the following steps: First, dry mix the Portland cement, mixed sand, highly active admixture and water reducer for 1 to 2 minutes; Then, add water, defoamer and other liquid materials for wet mixing. The wet mixing time should not be less than 5 minutes, until the mixture is close to the target fluidity; After that, slowly add the fibers. After all the fibers are added, continue stirring for at least 2 minutes until the fibers are evenly dispersed in the mixture.

10. The process for preparing Yellow River sand UHPC according to claim 7, characterized in that: In step S3, the temperature of high pressure heating is controlled between 220 and 360° C., and the pressure is controlled between 12 and 20 MPa.

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