An ultra-high performance concrete prepared by using waste slurry of a concrete mixing plant and a design method of a mix proportion thereof

Abstract

The application discloses a kind of super high performance concrete prepared by using concrete mixing plant waste slurry, mainly by the following mass fraction of raw materials: waste slurry 380-460, cement 580-650, silica fume 80-155, fly ash 80-275, fine quartz sand 550-750, coarse quartz sand 250-430, liquid admixture 30-50, tap water 50-60, steel fiber 140-160.The design method of the mix proportion of the super high performance concrete is also disclosed;The application provides a new way for the recycling of concrete mixing plant waste slurry, which reduces the emission of construction waste, reduces the comprehensive cost of concrete production, realizes resource recycling, meets the standards and requirements of green production, and achieves the purpose of environmental protection.It has good economic and environmental benefits.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to an ultra-high performance concrete using waste slurry from a concrete mixing plant as raw material and its mix design method. Background Technology

[0002] Concrete batching plants generate a large amount of waste slurry during concrete production, and its direct discharge not only has a serious impact on the ecological environment but also represents a waste of resources. Ultra-high performance concrete (UHPC) has broad application prospects due to its superior properties such as ultra-high strength, high durability, and environmental friendliness; however, traditional UHPC raw materials are costly. Utilizing waste slurry as one of the raw materials for preparing UHPC could achieve the dual benefits of waste recycling and reduced UHPC costs, meeting the requirements of green production. However, the waste slurry has a high impurity content, complex composition, and a highly alkaline liquid environment. A key challenge is how to design UHPC mix proportions using waste slurry to ensure that the molded components meet UHPC performance requirements. Summary of the Invention

[0003] The purpose of this invention is to provide an ultra-high performance concrete prepared using waste slurry from a concrete mixing plant.

[0004] The present invention also aims to provide a design method for the mix proportion of ultra-high performance concrete prepared using waste slurry from concrete mixing plants.

[0005] The final objective of this invention is to provide a method for preparing the aforementioned ultra-high performance concrete.

[0006] This invention rationally utilizes and transforms waste slurry generated during concrete production into one of the raw materials for UHPC (Ultra-High Performance Concrete), ensuring that the ultra-high performance concrete prepared using this waste slurry meets or approaches traditional UHPC standards in key properties such as strength, durability, and workability. Simultaneously, it significantly reduces the emission of engineering waste, achieves resource recycling, lowers the overall cost of ultra-high performance concrete production, and achieves the goals of green, low-carbon, and environmentally friendly practices.

[0007] The first objective of this invention can be achieved by the following technical solution: an ultra-high performance concrete prepared using waste slurry from a concrete mixing plant, mainly composed of the following raw materials in parts by weight: waste slurry 380-460, cement 580-650, silica fume 80-155, fly ash 80-275, fine quartz sand 550-750, coarse quartz sand 250-430, liquid admixture 30-50, tap water 50-60, and steel fiber 140-160, wherein the solid content of the waste slurry is 60%-70%.

[0008] Preferably, the solid components of the waste slurry are mainly hydrated and unhydrated cement, silica fume, fly ash and fine sand, and the mass ratio of cement, silica fume, fly ash and fine sand is 5-6:1-2:1-2:4-5; the liquid component of the waste slurry is mainly wastewater, and the pH value of the wastewater is 8-10.

[0009] The solid content of mud is the percentage of dry weight in the mud.

[0010] Preferably, the waste slurry of the present invention is prepared by the following method:

[0011] (1) Drainage ditches and collection pools are set up in the concrete mixing and molding area. The collected concrete is mixed, produced, cleaned and the site is washed to obtain preliminary waste slurry.

[0012] (2) Use a screen to remove stones and coarse sand particles from the initial waste slurry, and then filter it further through a filter screen and a filter press to remove fine suspended solids, thus obtaining the waste slurry after impurity removal.

[0013] (3) The waste slurry after impurity removal is diluted with tap water and acidic agents are added for preparation to obtain the waste slurry.

[0014] In this invention, the cement used is ordinary Portland cement, preferably ordinary Portland cement with a strength grade of 52.5, which can reduce the heat released by the hydration reaction.

[0015] The ultra-high performance concrete (UHPC) prepared from waste slurry from a concrete mixing plant, provided by this invention, comprises 380-460 parts, preferably 400-460 parts, of waste slurry. This invention selects waste slurry as one of the raw material components of UHPC, utilizing the filling and stacking effects of fine particles in the waste slurry to optimize the microporous structure of UHPC, improve its density, and enhance its workability; utilizing the alkaline environment in the waste slurry to accelerate the hydration rate of the UHPC cementitious material; and utilizing the nucleation effect and induction effect of ions in the waste slurry to improve the degree of hydration of the UHPC cementitious material. This achieves a certain degree of recyclability of water, cementitious materials, and sand, reducing the production cost of UHPC, realizing green production, and achieving the goal of low-carbon and environmental protection.

[0016] Based on 380-460 parts by weight of waste slurry, the ultra-high performance concrete provided by this invention includes 580-650 parts of cement, preferably 600-630 parts, and more preferably 610-620 parts. Due to the addition of waste slurry, this invention can reduce the amount of cement used, thereby reducing production costs and making it more environmentally friendly.

[0017] In this invention, the cement used is ordinary Portland cement, preferably ordinary Portland cement with a strength grade of 52.5, which can reduce the heat released by the hydration reaction.

[0018] Based on 380-460 parts by weight of waste slurry, the ultra-high performance concrete provided by this invention includes 80-155 parts of silica fume, preferably 100-125 parts, and more preferably 110-115 parts. In this invention, the silica fume can undergo a secondary hydration reaction with calcium hydroxide, a cement hydration product, to generate more gel, fill the pores, and improve the density of UHPC. Simultaneously, it improves the internal structure of UHPC, resulting in better bonding between the matrix and fibers, strengthening the fiber's constraint on the matrix, and improving the material's toughness.

[0019] In this invention, the silica fume has a particle size of 0.15-0.25 μm. This invention fills the pores between UHPC particles by adding extremely fine silica fume, making the slurry more uniform, improving fluidity, and facilitating molding.

[0020] Based on 380-460 parts by weight of waste slurry, the ultra-high performance concrete provided by this invention includes 80-275 parts of fly ash, preferably 110-240 parts, and more preferably 150-205 parts. In this invention, the fly ash is preferably Grade I fly ash, and the silica fume has a particle size of 0.15-0.25 μm. The Grade I fly ash particles added in this invention are spherical with a smooth surface, acting as "ball bearings" in the UHPC mixture, reducing inter-particle friction, significantly improving the fluidity of the mixture, and facilitating casting and molding. Simultaneously, fly ash can reduce the alkali content in the concrete, reducing the possibility of alkali reaction with reactive aggregates, lowering the risk of alkali-aggregate reaction damage to UHPC molded components, and extending the service life of the components.

[0021] Based on 380-460 parts by weight of waste slurry, the ultra-high performance concrete provided by this invention includes 550-750 parts, preferably 600-700 parts, of fine quartz sand and 250-430 parts, preferably 300-400 parts, of coarse quartz sand. The particle size of the fine quartz sand is 0.2-0.6 mm; the particle size of the coarse quartz sand is 0.6-1.2 mm. In this invention, the aggregate is selected as fine quartz sand and coarse quartz sand, and the ratio of the two is 1:0.45-0.57. In this invention, the mixed use of fine quartz sand and coarse quartz sand makes the particle size distribution more reasonable. The coarse sand forms the skeleton, and the quartz sand fills the pores, reducing interparticle friction and cohesion, improving the fluidity of the mixture, and facilitating better filling of the mold during the molding process of UHPC. At the same time, the multi-level particle structure formed by the mixture of coarse and fine quartz sand makes the cohesiveness of the mixture more suitable.

[0022] Based on 380-460 parts by weight of waste slurry, the ultra-high performance concrete provided by this invention includes 30-50 parts of liquid admixture, preferably 35-45 parts, and more preferably 38-42 parts. In this invention, the liquid admixture is a polycarboxylate superplasticizer with a solid content of 30%-40%. The polycarboxylate superplasticizer added in this invention has a high water reduction rate, which can significantly reduce the water requirement of the UHPC mixture, and still maintain good fluidity of the mixture at a low water-cement ratio.

[0023] Based on 380-460 parts by weight of waste slurry, the ultra-high performance concrete provided by this invention includes 140-160 parts, preferably 145-155 parts, of steel fiber. The steel fiber is copper-plated linear steel fiber with a diameter of 0.18-0.22 mm, a length of 6-19 mm, and a tensile strength of 1800-2200 MPa. The steel fiber added in this invention can tightly bind with the cement slurry in UHPC, enhancing the cohesiveness of the mixture and preventing segregation and bleeding during transportation and pouring, thus ensuring the uniformity of the mixture. Simultaneously, it improves the ability of the molded component to resist bending deformation, giving the molded component better impact and vibration resistance.

[0024] Based on 380-460 parts by weight of waste slurry, the ultra-high performance concrete provided by this invention includes 50-60 parts by weight of tap water.

[0025] The second objective of this invention can be achieved through the following technical solution: the method for designing the mix proportion of ultra-high performance concrete prepared using waste slurry from a concrete mixing plant includes the following steps:

[0026] (1) Select raw materials for preparing ultra-high performance concrete, including waste slurry, cement, silica fume, fly ash, fine quartz sand, coarse quartz sand, liquid admixtures, tap water and steel fibers.

[0027] (2) Design the mix proportions of each raw material in ultra-high performance concrete, including:

[0028] (2.1) Determine the proportion of cement, silica fume and fly ash in ultra-high performance concrete, and calculate the material relationship between cement, silica fume and fly ash;

[0029] (2.2) Determine the ratio of fine quartz sand to coarse quartz sand in ultra-high performance concrete;

[0030] (2.3) Determine the mortar ratio of ultra-high performance concrete to obtain the material ratio between cement, silica fume, fly ash, fine quartz sand and coarse quartz sand. The mortar ratio is a binder material, which includes cement, silica fume and fly ash. The sand in the mortar ratio is fine quartz sand and coarse quartz sand.

[0031] (2.4) Determine the water-cement ratio of ultra-high performance concrete and the dosage of waste slurry, liquid admixtures and steel fibers;

[0032] (2.5) Determine the amount of cement used and calculate the amounts of waste slurry, silica fume, fly ash, fine quartz sand, coarse quartz sand, liquid admixture, tap water and steel fiber.

[0033] Preferably, the mass ratio of cement to silica fume and fly ash in step (2.1) is 1:0.14-0.24:0.14-0.4.

[0034] Preferably, the mass ratio of fine quartz sand to coarse quartz sand in step (2.2) is 1:0.45-0.57.

[0035] Preferably, the mortar-mortar ratio in step (2.3) is 0.9-1:1.

[0036] Preferably, the water-to-glue ratio in step (2.4) is 0.05-0.07:1.

[0037] Preferably, the amount of waste slurry added in step (2.4) is 40%-50% of the total mass of cementitious materials, silica fume, and fly ash.

[0038] Preferably, the amount of liquid admixture in step (2.4) is 4%-4.8% of the total mass of cementitious materials, silica fume, and fly ash.

[0039] Preferably, the amount of steel fiber in step (2.4) is 14%-18% of the total mass of cementitious materials, silica fume, and fly ash.

[0040] This invention provides a mix design method for ultra-high performance concrete (UHPC) prepared using waste slurry from concrete mixing plants. It rationally utilizes and transforms waste slurry generated during concrete production into one of the raw materials for UHPC, while simultaneously determining the appropriate proportions of waste slurry, cementitious materials, sand, and steel fibers. By leveraging the filling and packing effects of fine particles in the waste slurry, the microporous structure of UHPC is optimized, and its density is improved. Furthermore, the alkaline environment and ion-induced nucleation effect in the waste slurry accelerate the hydration rate and degree of hydration of the UHPC cementitious materials, resulting in UHPC prepared using waste slurry with mechanical properties far exceeding those of traditional concrete materials. The invention also presents a universally applicable process adaptable to waste slurry of different sources and properties, not limited to specific production lines, and easily promoted in various concrete production scenarios, accelerating the industry's green transformation and reducing the overall cost of concrete production.

[0041] The last objective of this invention can be achieved by the following technical solution: the above-mentioned method for preparing ultra-high performance concrete includes the following steps:

[0042] (1) Preparation of waste slurry;

[0043] (2) Cement, silica fume, fly ash, fine quartz sand, coarse quartz sand and steel fiber are mixed to obtain a mixed dry material;

[0044] (3) Mix water, waste slurry and liquid additives to obtain mixed wet material;

[0045] (4) Mix the dry material and the wet material to obtain ultra-high performance concrete prepared using waste slurry from the concrete mixing plant.

[0046] In step (2) of this invention, cement, silica fume, fly ash, quartz sand, and steel fibers are mixed to obtain a mixed dry material. In this invention, the mixing is preferably pre-stirred; the pre-stirring time is preferably 180 seconds. This invention ensures that the solid raw material particles and steel fibers are fully mixed through pre-stirring.

[0047] In step (3) of this invention, water, waste slurry, and liquid additives are mixed to obtain a mixed wet material. In this invention, the mixing is preferably carried out under stirring conditions.

[0048] After obtaining the dry and wet mixtures, this invention further mixes them to obtain ultra-high performance concrete prepared using waste slurry from a concrete mixing plant. In this invention, the mixing is preferably carried out under stirring conditions; the stirring time is preferably 480 seconds. This invention ensures that the dry and wet mixtures are uniformly mixed and fully reacted through stirring.

[0049] The present invention has the following advantages: The ultra-high performance concrete provided by the present invention innovatively utilizes and transforms the waste slurry generated in the concrete production process into one of the raw materials of UHPC, which not only reduces the emission of engineering waste, but also realizes the recycling of resources, reduces the overall cost of ultra-high performance concrete production, and achieves the goal of green, low-carbon and environmental protection, and has good application prospects. Detailed Implementation

[0050] The present invention will be further described below with reference to specific embodiments. The following embodiments are for illustrative purposes only and should not be construed as limiting the invention. Unless otherwise specified, the raw materials and equipment used in the following embodiments are obtained through conventional commercial means.

[0051] The solid content of the waste slurry of this invention is 60%-70%. The solid components of the waste slurry are mainly hydrated and unhydrated cement, silica fume, fly ash and fine sand. The mass ratio of cement, silica fume, fly ash and fine sand is 5-6:1-2:1-2:4-5. The liquid component of the waste slurry is mainly wastewater, and the pH value of the wastewater is 8-10.

[0052] The method for obtaining waste slurry in this invention includes, but is not limited to, the following:

[0053] Special drainage ditches and collection pools are set up in the concrete mixing and molding area of ​​the concrete batching plant to collect waste slurry generated from concrete production, cleaning, site washing, etc.

[0054] Larger particles such as stones and sand are removed from wastewater by using a bar screen, and then fine suspended solids are further filtered through a filter screen.

[0055] The waste slurry is diluted with municipal tap water to achieve a water content of 30%-40% and a solid content of 60%-70%. Acidic agents such as sulfuric acid and hydrochloric acid are added to bring the pH value to 8-10.

[0056] The present invention provides a method for mix design of ultra-high performance concrete prepared using waste slurry from a concrete mixing plant, comprising the following steps:

[0057] (1) Select raw materials for preparing ultra-high performance concrete, including waste slurry, cement, silica fume, fly ash, fine quartz sand, coarse quartz sand, liquid admixtures, tap water and steel fibers.

[0058] (2) Design the mix proportions of each raw material in ultra-high performance concrete, including:

[0059] (2.1) Based on the simple particle close packing formula, the proportion of cement, silica fume and fly ash in ultra-high performance concrete is determined, and the material relationship between cement, silica fume and fly ash is calculated.

[0060]

[0061] In the formula: G(R) is the percentage (%) of particles with a maximum diameter of R in the total volume; R max The maximum particle size D of each raw material particle max Half of (m); n is the number of each type of raw material particle; m is the amount of raw material solid particles used (parts); ρ is the density of each type of raw material solid particles (parts / m³). 3 ).

[0062] The mass ratio of cement, silica fume, and fly ash is 1:(0.14-0.24):(0.14-0.4).

[0063] (2.2) Determine the ratio of fine quartz sand to coarse quartz sand in ultra-high performance concrete;

[0064] The mass ratio of fine quartz sand to coarse quartz sand is 1:(0.45-0.57).

[0065] (2.3) Determine the mortar ratio of ultra-high performance concrete to obtain the material ratio between cement, silica fume, fly ash, fine quartz sand and coarse quartz sand. The mortar in the mortar ratio is the cementing material, which includes cement, silica fume and fly ash. The sand in the mortar ratio is fine quartz sand and coarse quartz sand.

[0066]

[0067] In the formula: B / A is the mortar ratio, with a value of (0.9-1):1; m B The amount (parts) of cementitious material used; m A This refers to the amount (parts) of quartz sand used.

[0068] (2.4) Determine the water-cement ratio of ultra-high performance concrete and the dosage of waste slurry, liquid admixtures and steel fibers;

[0069]

[0070] In the formula: W / B is the water-to-binder ratio, with a value of (0.05-0.07):1; m B The amount (parts) of cementitious material used; m w This refers to the amount of water used (in portions).

[0071] The dosage of liquid admixtures is 4%-4.8% of the total mass of the cementitious materials.

[0072] UHPC mortar was prepared based on waste slurry, cement, silica fume, fly ash, fine quartz sand, coarse quartz sand, water, and liquid admixtures. Flowability and slump tests were conducted by controlling different amounts of waste slurry. It was found that when the flowability of the UHPC mortar was 200–220 mm and the slump was 220–260 mm, the waste slurry content was 40%–50% of the total mass of the cementitious materials.

[0073] The amount of steel fiber is 14%-18% of the total mass of cementitious materials.

[0074] (2.5) Determine the amount of cement used and calculate the amounts of waste slurry, silica fume, fly ash, fine quartz sand, coarse quartz sand, liquid admixture, tap water and steel fiber.

[0075] This invention provides a mix design method for preparing ultra-high performance concrete (UHPC) using waste slurry from concrete mixing plants. Based on the theory of close packing of particles, the method determines the material relationships between cementitious materials and further determines the dosage of waste slurry, sand, water, liquid admixtures, and steel fibers based on the binder-to-mortar ratio, water-to-binder ratio, and mortar tests. UHPC prepared using this method efficiently solves the problem of waste slurry recycling, fully utilizing the filling and packing effects of fine particles in the waste slurry to optimize the microporous structure of UHPC and improve its density. This method saves raw materials, reduces production costs, enhances the mechanical and durability properties of UHPC, and is environmentally friendly and meets the requirements of green production. Given its excellent performance and environmental advantages, this method can be widely promoted in various engineering production scenarios, helping to accelerate the green transformation process of related industries.

[0076] This leads to the formulation of ultra-high performance concrete prepared using waste slurry from a concrete mixing plant, which is mainly composed of the following raw materials in parts by weight: waste slurry 380-460, cement 580-650, silica fume 80-155, fly ash 80-275, fine quartz sand 550-750, coarse quartz sand 250-430, liquid admixture 30-50, tap water 50-60, and steel fiber 140-160.

[0077] The ultra-high performance concrete of this invention can be prepared by the following method:

[0078] (1) Preparation of waste slurry: The waste slurry generated in concrete production is pretreated as described above to obtain pretreated waste slurry;

[0079] (2) Mix cement, silica fume, fly ash, quartz sand and steel fiber to obtain a mixed dry material;

[0080] (3) Mix water, pretreated waste slurry and liquid additives to obtain mixed wet material;

[0081] (4) Mix the dry material and the wet material to obtain ultra-high performance concrete prepared using waste slurry from the concrete mixing plant.

[0082] The present invention employs the above-described preparation sequence, which can improve the uniformity of stirring while shortening the stirring time.

[0083] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0084] Example 1

[0085] The ultra-high performance concrete prepared using waste slurry from a concrete mixing plant in this embodiment is made from the following raw materials in parts by weight: 390 parts pretreated waste slurry, 600 parts ordinary Portland cement with a strength grade of 52.5, 100 parts silica fume with a particle size of 0.2μm, 200 parts grade I fly ash, 600 parts quartz sand with a particle size of 0.2-0.6mm, 300 parts quartz sand with a particle size of 0.6-1.2mm, 40 parts polycarboxylate superplasticizer with a solid content of 30%-40%, 60 parts tap water, and 150 parts copper-plated straight steel fibers with a length of 15mm, a diameter of 0.2mm, and a tensile strength of 2000MPa.

[0086] Preparation method:

[0087] Cement, silica fume, fly ash, fine quartz sand, coarse quartz sand, and steel fibers are added to a drum mixer and dry-mixed for 180 seconds to obtain a mixed dry material.

[0088] Waste slurry, water, and polycarboxylate superplasticizer are added to a mixing tank and stirred for 180 seconds with a stirring rod to obtain a mixed wet material.

[0089] Slowly add the mixed wet material to the above-mentioned dry mixed material and stir for 480 seconds to obtain ultra-high performance concrete prepared using waste slurry from a concrete mixing plant.

[0090] Example 2

[0091] The ultra-high performance concrete prepared using waste slurry from a concrete mixing plant in this embodiment is made from the following raw materials in parts by weight: 420 parts of pretreated waste slurry, 600 parts of ordinary Portland cement with a strength grade of 52.5, 100 parts of silica fume with a particle size of 0.2μm, 200 parts of Class I fly ash, 600 parts of quartz sand with a particle size of 0.2-0.6mm, 300 parts of quartz sand with a particle size of 0.6-1.2mm, 55 parts of tap water, 40 parts of polycarboxylate superplasticizer with a solid content of 30%-40%, and 150 parts of copper-plated straight steel fibers with a length of 15mm and a diameter of 0.2mm.

[0092] Preparation method:

[0093] Cement, silica fume, fly ash, fine quartz sand, coarse quartz sand, and steel fibers are added to a drum mixer and dry-mixed for 180 seconds to obtain a mixed dry material.

[0094] Waste slurry, water, and polycarboxylate superplasticizer are added to a mixing tank and stirred for 180 seconds with a stirring rod to obtain a mixed wet material.

[0095] Slowly add the mixed wet material to the above-mentioned dry mixed material and stir for 480 seconds to obtain ultra-high performance concrete prepared using waste slurry from a concrete mixing plant.

[0096] Example 3

[0097] The ultra-high performance concrete prepared using waste slurry from a concrete mixing plant in this embodiment is made from the following raw materials in parts by weight: 450 parts of pretreated waste slurry, 600 parts of ordinary Portland cement with a strength grade of 52.5, 100 parts of silica fume with a particle size of 0.2μm, 200 parts of Class I fly ash, 600 parts of quartz sand with a particle size of 0.2-0.6mm, 300 parts of quartz sand with a particle size of 0.6-1.2mm, 50 parts of tap water, 40 parts of polycarboxylate superplasticizer with a solid content of 30%-40%, and 150 parts of copper-plated straight steel fibers with a length of 15mm and a diameter of 0.2mm.

[0098] Preparation method:

[0099] Cement, silica fume, fly ash, fine quartz sand, coarse quartz sand, and steel fibers are added to a drum mixer and dry-mixed for 180 seconds to obtain a mixed dry material.

[0100] Waste slurry, water, and polycarboxylate superplasticizer are added to a mixing tank and stirred for 180 seconds with a stirring rod to obtain a mixed wet material.

[0101] Slowly add the mixed wet material to the above-mentioned dry mixed material and stir for 480 seconds to obtain ultra-high performance concrete prepared using waste slurry from a concrete mixing plant.

[0102] Comparative Example 1

[0103] The ordinary ultra-high performance concrete of this comparative example is made from the following raw materials in parts by weight: 800 parts of ordinary Portland cement with a strength grade of 52.5, 200 parts of silica fume with a particle size of 0.2μm, 200 parts of Class I fly ash, 700 parts of quartz sand with a particle size of 0.2-0.6mm, 400 parts of quartz sand with a particle size of 0.6-1.2mm, 240 parts of tap water, 40 parts of polycarboxylate superplasticizer with a solid content of 30%-40%, and 180 parts of copper-plated straight steel fibers with a length of 15mm and a diameter of 0.2mm.

[0104] Preparation method:

[0105] Cement, silica fume, fly ash, fine quartz sand, coarse quartz sand, and steel fibers are added to a drum mixer and dry-mixed for 180 seconds to obtain a mixed dry material.

[0106] Add water and polycarboxylate superplasticizer to a mixing tank and stir with a stirring rod for 180 seconds to obtain a mixed wet material.

[0107] Slowly add the mixed wet material to the above-mentioned dry mixed material and stir for 480 seconds to obtain ultra-high performance concrete prepared using waste slurry from a concrete mixing plant.

[0108] The performance test results of the ultra-high performance concrete prepared in Examples 1-3 and Comparative Example 1 after 28 days are shown in Table 1. The test standard is "Standard for Test Methods of Physical and Mechanical Properties of Concrete" (GB / T 50081-2019).

[0109] Table 1. 28-day performance of ultra-high performance concrete prepared in Examples 1-3

[0110] serial number Compressive strength / MPa Flexural strength / MPa Tensile strength / MPa Example 1 124.76 27.67 7.43 Example 2 131.44 28.12 9.01 Example 3 121.97 25.74 6.92 Comparative Example 1 128.44 28.24 8.54

[0111] As shown in Table 1, the compressive strength, flexural strength, and tensile strength of the specimens in Examples 1, 2, 3, and Comparative Example 1 all meet the requirements for ultra-high performance concrete in the "Technical Specification for Reactive Powder Concrete Structures" (JGJ / T 413-2019). A comparative analysis of Examples 1, 2, and 3 reveals that the appropriate amount of waste slurry incorporated enhances the mechanical strength of the UHPC formed using waste slurry.

[0112] The carbon emissions generated during the concrete production process in Examples 1-3 and Comparative Example 1 are shown in Table 3. The calculation standard is the "Standard for Calculation of Carbon Emissions in Buildings" (GB / T 51366-2019).

[0113] Table 2 shows the carbon emissions generated during the UHPC production process in Examples 1-3 and Comparative Example 1.

[0114] serial number <![CDATA[Carbon emissions (k, gCO2)]]> Example 1 1030 Example 2 1030 Example 3 1030 Comparative Example 1 1340

[0115] As shown in Tables 1 and 2, under the same level of mechanical strength, the carbon emissions generated when producing UHPC using waste slurry (such as Examples 1, 2, and 3) are significantly lower than those generated when producing ordinary UHPC (Comparative Example 1), reducing CO2 by approximately 300 kg. This indicates that the incorporation of waste slurry can greatly reduce the carbon emissions generated during the production process. The UHPC formed using waste slurry from concrete mixing plants in this invention meets the requirements of green and low-carbon concrete.

[0116] Example 4

[0117] Unlike Example 1, the ultra-high performance concrete prepared using waste slurry from a concrete mixing plant provided in this example is made from the following raw materials in the indicated mass ratios: 455 parts waste slurry, 650 parts ordinary silicate cement, 130 parts silica fume, 130 parts fly ash, 666 parts fine quartz sand, 333 parts coarse quartz sand, 50 parts tap water, 40 parts polycarboxylate superplasticizer, and 130 parts steel fiber.

[0118] Example 5

[0119] Unlike Example 1, the ultra-high performance concrete prepared using waste slurry from a concrete mixing plant provided in this example is made from the following raw materials in the indicated mass ratios: 410 parts waste slurry, 620 parts ordinary silicate cement, 140 parts silica fume, 140 parts fly ash, 680 parts fine quartz sand, 320 parts coarse quartz sand, 60 parts tap water, 43 parts polycarboxylate superplasticizer, and 147 parts steel fiber.

[0120] Example 6

[0121] Unlike Example 1, the ultra-high performance concrete prepared using waste slurry from a concrete mixing plant provided in this example is made from the following raw materials in the indicated mass ratios: 400 parts waste slurry, 590 parts ordinary silicate cement, 90 parts silica fume, 220 parts fly ash, 690 parts fine quartz sand, 310 parts coarse quartz sand, 55 parts tap water, 42 parts polycarboxylate superplasticizer, and 160 parts steel fiber.

[0122] This invention utilizes waste slurry from concrete mixing plants to prepare ultra-high performance concrete (UHPC). By designing the mix proportions based on the close packing theory formula using waste slurry generated during concrete production, and preparing the concrete according to the given method, the resulting UHPC exhibits mechanical properties that meet current standards and achieves the required strength for UHPC. This invention, through a scientific and reliable mix design method, rationally utilizes and transforms waste slurry generated during concrete production into a raw material for UHPC, enabling the UHPC prepared using this waste slurry to reach or approach traditional UHPC standards in key properties such as strength, durability, and workability. It provides a new approach for the recycling of waste slurry from concrete mixing plants, reduces the emission of construction waste, achieves resource recycling, and realizes the goals of environmental protection, green and low-carbon development, while simultaneously reducing the overall production cost of UHPC. It has significant economic, environmental, and social benefits.

[0123] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A type of ultra-high performance concrete prepared using waste slurry from a concrete mixing plant, characterized in that, It is mainly made from the following raw materials in parts by weight: waste slurry 380-460, cement 580-650, silica fume 80-155, fly ash 80-275, fine quartz sand 550-750, coarse quartz sand 250-430, liquid admixture 30-50, tap water 50-60, and steel fiber 140-160; the solid content of the waste slurry is 60%-70%, and the solid components of the waste slurry are mainly hydrated and unhydrated cement, silica fume, fly ash, and fine sand, and the mass ratio of cement, silica fume, fly ash, and fine sand is 5-6:1-2:1-2:4-5; the liquid component of the waste slurry is mainly wastewater, and the pH value of the wastewater is 8-10.

2. The ultra-high performance concrete prepared using waste slurry from a concrete mixing plant according to claim 1, characterized in that, The waste slurry is prepared by the following method: (1) Drainage ditches and collection pools are set up in the concrete mixing and molding area. The collected concrete is mixed, produced, cleaned and the site is washed to obtain preliminary waste slurry. (2) Use a screen to remove stones and coarse sand particles from the initial waste slurry, and then filter it further through a filter screen and a filter press to remove fine suspended solids, thus obtaining the waste slurry after impurity removal; (3) The waste slurry after impurity removal is diluted with tap water and acidic agent is added for preparation to obtain the waste slurry.

3. The ultra-high performance concrete prepared using waste slurry from a concrete mixing plant according to claim 1, characterized in that, The cement is ordinary Portland cement with a strength grade of 52.5; the silica fume has a particle size of 0.15-0.25μm; the fly ash is Grade I fly ash; the fine silica sand has a particle size of 0.2-0.6mm; the coarse silica sand has a particle size of 0.6-1.2mm; the steel fiber is copper-plated linear steel fiber with a diameter of 0.18-0.22mm, a length of 6-19mm, and a tensile strength of 1800-2200MPa; the liquid admixture is polycarboxylate superplasticizer.

4. The method for mix design of ultra-high performance concrete prepared using waste slurry from a concrete mixing plant as described in any one of claims 1-3, characterized in that, Includes the following steps: (1) Select raw materials for preparing ultra-high performance concrete, including waste slurry, cement, silica fume, fly ash, fine quartz sand, coarse quartz sand, liquid admixtures, tap water and steel fibers; (2) Design the mix proportions of each raw material in ultra-high performance concrete, including: (2.1) Determine the proportion of cement, silica fume and fly ash in ultra-high performance concrete, and calculate the material relationship between cement, silica fume and fly ash; (2.2) Determine the ratio of fine quartz sand to coarse quartz sand in ultra-high performance concrete; (2.3) Determine the mortar ratio of ultra-high performance concrete to obtain the material ratio between cement, silica fume, fly ash, fine quartz sand and coarse quartz sand. The mortar ratio is a binder material, which includes cement, silica fume and fly ash. The sand in the mortar ratio is fine quartz sand and coarse quartz sand. (2.4) Determine the water-cement ratio of ultra-high performance concrete and the dosage of waste slurry, liquid admixtures and steel fibers; (2.5) Determine the amount of cement used and calculate the amount of waste slurry, silica fume, fly ash, fine quartz sand, coarse quartz sand, liquid admixture, tap water and steel fiber.

5. The method according to claim 4, characterized in that, The mass ratio of cement to silica fume and fly ash in step (2.1) is 1:0.14-0.24:0.14-0.4; the mass ratio of fine quartz sand to coarse quartz sand in step (2.2) is 1:0.45-0.57; and the mortar ratio in step (2.3) is 0.9-1:

1.

6. The method according to claim 4, characterized in that, The water-to-glue ratio mentioned in step (2.4) is 0.05-0.07:

1.

7. The method according to claim 4, characterized in that, The amount of waste slurry mentioned in step (2.4) is 40%-50% of the total mass of cementitious materials, silica fume and fly ash.

8. The method according to claim 4, characterized in that, The amount of liquid admixture in step (2.4) is 4%-4.8% of the total mass of cementitious materials, silica fume and fly ash; the amount of steel fiber is 14%-18% of the total mass of cementitious materials, silica fume and fly ash.

9. The method for preparing ultra-high performance concrete according to any one of claims 1-3, characterized in that, Includes the following steps: (1) Preparation of waste slurry; (2) Cement, silica fume, fly ash, fine quartz sand, coarse quartz sand and steel fiber are mixed to obtain a mixed dry material; (3) Mix water, waste slurry and liquid additives to obtain mixed wet material; (4) Mix the dry material and the wet material to obtain ultra-high performance concrete prepared using waste slurry from the concrete mixing plant.

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