A method for producing self-compacting concrete mixed with tailings

Abstract

The present invention provides a method for producing and preparing self-compacting concrete mixed with tailings, which is composed of coarse aggregate, tailings sand, fly ash, cement, water and admixtures. The coarse aggregate is determined according to the volume step-by-step filling method to determine the mixing ratio of each grade, and the coarse aggregate is wrapped by the fine aggregate without interfering with each other. According to the particle size synthesis method, the tailings sand and fly ash mixing ratios are determined, and the mortar material wraps the coarse aggregate and the filler to completely fill the remaining gaps in the self-compacting concrete. The volume change before and after the coarse aggregate and the filler are wrapped with a certain thickness of mortar film is calculated to calculate the amount of mortar film, and then determine the amount of raw materials for the self-compacting concrete. The materials of the present invention do not interfere with each other in space, ensure volume stability, and the cement mortar wraps the coarse aggregate and the filler to form an optimal strength state. By adjusting the relevant parameters, the performance of the self-compacting concrete is controllable, and solid waste materials such as tailings sand and fly ash are added to achieve the recycling of solid waste.

Description

Technical Field

[0001] The invention belongs to the technical field of recycling of waste materials, and in particular relates to a method for producing self-compacting concrete mixed with tailings sand. Technical Background

[0002] Self-compacting concrete refers to concrete that can flow and compact under its own weight, completely filling the formwork even in the presence of dense rebar, while achieving excellent homogeneity and requiring no additional vibration. Compared to ordinary concrete, self-compacting concrete has the characteristics of high fluidity, good penetration ability, and good stability. It has the ability to overcome resistance and flow within the formwork, flowing and filling every corner of the formwork. It does not segregate during flow, reduces bleeding, and has good anti-segregation capabilities. As a high-performance concrete, self-compacting concrete is commonly used as a joint connection material, component grouting material, bridge reinforcement and maintenance material, etc., and has been widely used in highway engineering, railway engineering, and construction engineering.

[0003] At present, the preparation process of self-compacting concrete completely refers to the mix design method in the "Technical Specifications for the Application of Self-compacting Concrete". This method piles up the raw materials step by step according to the recommended volume range based on the volume stacking theory, without considering the interaction between the materials. At the same time, the drying shrinkage of self-compacting concrete after hardening is large, and the amount of binder added must be scientifically controlled to reduce the shrinkage while ensuring strength. On the other hand, self-compacting concrete has a high demand for sand, generally above 40%. With the increasing pressure on environmental protection, the mining of natural sand is severely restricted, and there is an urgent need to find a substitute for natural sand and gravel. Therefore, using industrial solid waste tailings sand and fly ash instead of natural sand, and starting from the interaction mechanism between the raw materials, a self-compacting concrete production and preparation method with optimal density and strength and reduced shrinkage cracks is proposed. This is a problem that needs to be solved urgently. Summary of the Invention

[0004] The object of the present invention is to provide a method for producing and preparing self-compacting concrete mixed with tailings sand. The proportion of each grade of coarse aggregate is determined according to a step-by-step filling method in which fine aggregate is filled in the gaps of coarse aggregate. The cement gel material wraps the coarse aggregate and filler in the densest state, giving full play to the interaction between the coarse aggregate, cement and filler to achieve complete zero-void filling and optimal strength formation. The blending ratio of fly ash and tailings sand is determined according to the particle size synthesis theory of medium sand, thereby realizing the resource recycling of industrial waste materials, thereby providing a method for producing and preparing self-compacting concrete with superior performance.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for producing self-compacting concrete mixed with tailings comprises the following steps:

[0007] (1) The self-compacting concrete comprises: coarse aggregate, tailings sand, fly ash raw materials, as well as cement, water, and admixtures;

[0008] (2) Fill 1m with coarse aggregate first 3 The volume of the coarse aggregate in each cubic meter of self-compacting concrete is determined by the partial volume of concrete. The coarse aggregate is filled according to the theory of gradual encapsulation. The first-level coarse particles are completely surrounded by the first-level fine particles. The gradation curve of the coarse aggregate is determined. The mixing ratio of each level of aggregate is determined according to the gradation method.

[0009] (3) Filling a portion of the volume with a filler consisting of tailings sand and fly ash, calculating the fineness modulus based on the screening results of the tailings sand and fly ash, and synthesizing the tailings sand and fly ash into medium sand according to the fineness modulus according to the particle size synthesis method, thereby determining the blending ratio between the tailings sand and fly ash;

[0010] (4) The remaining volume is filled with a gel material composed of water and cement, which wraps the coarse aggregate, tailings sand, and fly ash. The gel material is converted into a sphere of corresponding diameter according to the specific surface area. The gel material wraps the coarse aggregate, tailings sand, and fly ash spheres with a certain film thickness. The volume change before and after wrapping is used to calculate the volume of the gel material.

[0011] (5) Determine the water-binder ratio based on the designed strength of the prepared self-compacting concrete;

[0012] (6) According to the volume composition method, calculate 1m 3 The volume of coarse aggregate, filler and gel material in self-compacting concrete is calculated based on the calculated volume usage, material composition and material density. 3 The amount of coarse aggregate, tailings sand, fly ash, cement and water in self-compacting concrete is as follows: aggregate, tailings sand, fly ash, cement, water and admixtures are mixed in a mixer to prepare self-compacting cement concrete.

[0013] Further technology of the present invention:

[0014] Preferably, the coarse first-level particles are completely surrounded by fine first-level particles, and the gradation curve is determined according to the following formula, and the coarse aggregates of each grade are graded to determine their blending ratios:

[0015] The mixing ratio of each grade of aggregate is determined according to the grade composition.

[0016]

[0017] V' i+1 =V i '-V i

[0018]

[0019] Where:

[0020] V i '——the volume of aggregate to be filled in the i-th level, %, where V1 is 100%; V i ——Volume filling rate of aggregate in the i-th grade, %;

[0021] V' i+1 ——the volume of the next finer aggregate in the i-th grade to be filled, %; d i ——Sieve size of the i-th gear, mm; d i+1 ——Size of the next finer sieve hole of the i-th sieve, mm; a i ——Residue on the sieve at level i.

[0022] Preferably, according to the particle size synthesis method, the tailings sand and fly ash are synthesized into medium sand by the fineness modulus M, and the blending ratio between the tailings sand and the fly ash is determined according to the following formula:

[0023] P w +P f =100

[0024] P w ×M w +P f ×M f =M z

[0025]

[0026] Where:

[0027] P w ——The proportion of tailings sand in filler, %; M w ——fineness modulus of tailings sand;

[0028] P f ——The proportion of fly ash in filler, %; M f —fineness modulus of fly ash;

[0029] M z ——The fineness modulus of medium sand should be 2.3 to 3.0;

[0030] A 0.15 、A 0.3 、A 0.6 、A 1.18 、A 2.36 、A 4.75 are the cumulative percentages of residue on the corresponding sieves.

[0031] Preferably, the coarse aggregate, tailings sand, and fly ash are converted into spheres of corresponding diameters according to the following formula according to the same specific surface area, the gel material is wrapped with a film thickness of 0.02 to 0.04 mm to convert the volume of the spheres, and the volume change before and after wrapping is calculated according to the following formula:

[0032]

[0033]

[0034] S A =0.41+0.0041a+0.0082b+0.0164c+0.0287d+0.0614e

[0035] +0.1229f+0.3277g

[0036] Where:

[0037] D q ——diameter of a sphere of equal surface area, mm; ρ q ——Density of the raw material of the sphere to be converted, kg / m 3 ; V jt ——Volume of gel material wrapping the raw material of the converted sphere, m 3 ; V c ——Volume of raw materials, m 3 ; u - gel material film thickness, taken as 0.02 ~ 0.04mm; a, b, c, d, e, f, g are the pass rates of sieve holes of 4.75mm and below respectively.

[0038] Preferably, according to the volume composition method, 1m is calculated according to the following formula 3 The volume of coarse aggregate, filler and gel material in self-compacting concrete, and then determine the amount of coarse aggregate, tailings sand, fly ash, cement and water:

[0039] V0+V s +V j =1m 3

[0040] Where:

[0041] V0——Volume of coarse aggregate, m 3 ; V s ——Volume of packing, m 3 ; V j ——Gel material volume, m 3 .

[0042] Preferably, the tailings sand is one type of tailings sand or a mixture of two or more types of tailings sand.

[0043] Preferably, the admixture includes a water reducer accounting for 1.5-2% of the total mass of the gel material, a defoamer accounting for 1-1.5% of the total mass of the gel material, a heavy calcium powder accounting for 13-18% of the total mass of the gel material, and an air entraining agent accounting for 1-1.5% of the total mass of the gel material.

[0044] Compared with the prior art, the present invention has the following technical effects:

[0045] 1. The present invention provides a method for producing and preparing tailings-added self-compacting concrete, wherein each grade of coarse aggregate is filled in a step-by-step manner, wherein the coarse aggregate of the first grade is completely surrounded by the fine aggregate of the first grade. The coarse aggregate mixing ratio is determined according to the step-by-step volume filling method, and the volumes of the coarse aggregates of the different grades in the concrete do not interfere with each other, thereby preventing the added coarse aggregates from expanding the volume structure of the concrete and ensuring the density of the concrete.

[0046] 2. The present invention provides a method for producing and preparing self-compacting concrete mixed with tailings. The coarse aggregate and filler are converted into spheres of equal volume, and the converted spheres are wrapped with cement gel material with an optimal film thickness. The amount of cement gel material is accurately calculated through volume changes, and the interaction between the cement gel material, coarse aggregate and cement is fully utilized. After the cement gel material wraps the aggregate and filler, the entire concrete space is completely filled, so that it has better strength and higher density.

[0047] 3. The present invention provides a method for producing and preparing self-compacting concrete mixed with tailings, which adopts tailings sand and fly ash instead of natural sand, and uses tailings sand and fly ash according to functional requirements and particle size synthesis method, thereby ensuring that the self-compacting concrete has better performance and realizing the resource utilization of solid waste.

[0048] 4. The present invention provides a method for producing and preparing self-compacting concrete mixed with tailings. The method calculates the amount of raw materials through volume change and material space composition theory to ensure the performance of the self-compacting concrete. At the same time, the concrete performance can be controlled through parameter adjustment.

[0049] Other features and advantages of the present invention will be described in detail in the following detailed description. DETAILED DESCRIPTION

[0050] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further explained below with reference to specific embodiments.

[0051] All raw materials in the present invention are not particularly limited in their sources and can be purchased from the market or prepared according to conventional methods well known to those skilled in the art.

[0052] There is no particular limitation on the purity of all raw materials in the present invention. The present invention preferably uses analytically pure materials or materials of conventional purity used in the field of composite materials.

[0053] Example 1

[0054] The following uses phosphate tailings, cement, fly ash, water, coarse aggregate and admixtures to prepare 1m3 of strength C40. 3 For self-compacting concrete, the coarse aggregate includes three grades of aggregate, namely 1#, 2# and 3#. The density of the raw materials is shown in Table 1.

[0055] Table 1: Apparent density of raw materials

[0056] Material <![CDATA[Density (kg / m 3 )]]> Coarse aggregate (5~10mm) 2900 Coarse aggregate (10~15mm) 2980 Coarse aggregate (15~20mm) 3000 Phosphate tailings 2860 fly ash 2800 cement 3010

[0057] The cement used in the mixture is 42.5 ordinary Portland cement. According to the requirements of the Technical Specifications for the Application of Self-compacting Concrete, the volume of coarse aggregate in each cubic meter of concrete is 0.3m 3 According to the following formula, the volume filling rate Vi of each level of coarse aggregate is calculated one by one. (When calculating the volume percentage of i+1 level particles, the volume percentage of i level particles must be deducted from the total volume V that i+1 level particles need to fill.) The coarse aggregates used are 5-10mm, 10-15mm, and 15-20mm. The sieve openings of the three levels of aggregate in the specification are similar to 4.75mm, 9.5mm, 16mm, and 19mm. The theoretical gradation of coarse aggregate is calculated according to the following formula:

[0058]

[0059] ''

[0060] V i+1 =V i -V i

[0061]

[0062] (i=1{19}, 2{16}, 3{9.5}, 4{4.75})

[0063] Table 2: Theoretical gradation curve of coarse aggregate

[0064]

[0065] The coarse aggregate is grade 3 aggregate. The results of screening the grade 3 coarse aggregate, tailings sand and fly ash are shown below:

[0066] Table 3: Raw material screening results

[0067]

[0068] The coarse aggregate is graded according to the above grading curve, and the results are as follows:

[0069] Table 4: Coarse aggregate grade mix results

[0070]

[0071] According to the screening results of tailings sand and fly ash, the cumulative sieve residue percentage is:

[0072] Table 5: Calculation of filler sieve residue percentage

[0073]

[0074] Calculate the fineness modulus according to the following formula: Fly ash and tailings sand fineness modulus M w =3.15, M f =1.43.

[0075]

[0076] Take the fineness modulus M of medium sand z is 2.5, and the graded composition is carried out according to the following formula. The proportions of tailings sand and fly ash in the filler are 62% and 38% respectively.

[0077] P w +P f =100

[0078] P w ×M w +P f ×M f =M z

[0079] According to the screening results of coarse aggregate, tailings sand and fly ash, the specific surface area is calculated as follows:

[0080] S A =0.41+0.0041a+0.0082b+0.0164c+0.0287d+0.0614e

[0081] +0.1229f+0.3277g

[0082] Table 6: Calculation results of specific surface area of raw materials

[0083]

[0084] Convert coarse aggregate, tailings sand, and fly ash into spheres of corresponding diameters according to the following formula:

[0085]

[0086] Table 7: Raw material equivalent specific surface area sphere diameter

[0087]

[0088] The Technical Specifications for the Application of Self-Compacting Concrete require that the volume of coarse aggregate in each cubic meter of concrete be 0.3m 3 According to the mixing ratio of coarse aggregates 1#, 2#, and 3#, as well as the mixing ratio of tailings sand and fly ash in the filler, the volume ratio of coarse aggregates 1#, 2#, and 3# is 49.5%, 27%, and 23.5% respectively. The volume ratio of tailings sand and fly ash in the filler is 61.5% and 38.5% respectively.

[0089] The thickness of the gel material film is 0.03 mm, and the volume of the wrapped gel material is calculated as:

[0090]

[0091] Table 8: Volume of gel material wrapped in equivalent sphere of raw materials

[0092]

[0093] According to the volume of self-compacting concrete, 1m 3 Concrete consists of coarse aggregate, filler, and cement paste. The volume of filler and cement paste is calculated according to the following formula. The volume of filler is 0.402m 3 :

[0094] V0+V s +V j =1m 3

[0095] The volume of the gel material is 0.298m 3 , according to the C40 grade self-compacting concrete design, according to the method in the "self-compacting concrete application technical regulations", determine the water-binder ratio to be 0.35. According to the volume and density of raw materials, calculate 1m 3 The raw material dosage of self-compacting concrete is as follows:

[0096] Table 9: 1m 3 Raw material dosage of self-compacting concrete

[0097] Material Dosage Coarse aggregate (5~10mm) 204kg Coarse aggregate (10~15mm) 245kg Coarse aggregate (15~20mm) 445kg tailings sand 707kg fly ash 433kg cement 446kg water 240kg

[0098] The admixtures are water reducer, defoamer, heavy calcium powder and air entraining agent. The dosage is as follows:

[0099] Table 10: 1m 3 Dosage of self-compacting concrete admixture

[0100] Material Dosage water reducer 11.6kg defoaming agent 7.08kg Heavy calcium powder 102kg air-entraining agent 7.21kg

[0101] Aggregate, tailings sand, fly ash, cement, water, and admixtures were mixed in a mixer to produce self-compacting cement concrete. The properties of the concrete were measured, and the test data are shown in Table 11.

[0102] Table 11: Self-compacting concrete performance test results

[0103] Initial expansion / mm 24h compressive strength / MPa 3d compressive strength / MPa 820 32 45

[0104] The basic principles, main features, and characteristics of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above-described embodiments. The above-described embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for producing self-compacting concrete mixed with tailings, characterized in that: The steps include: (1) The self-compacting concrete comprises: coarse aggregate, tailings sand, fly ash raw materials, as well as cement, water, and admixtures; (2) Fill 1m with coarse aggregate first 3 The volume of the coarse aggregate in each cubic meter of self-compacting concrete is determined by the partial volume of concrete. The coarse aggregate is filled according to the theory of gradual encapsulation. The first-level coarse particles are completely surrounded by the first-level fine particles. The gradation curve of the coarse aggregate is determined. The mixing ratio of each level of aggregate is determined according to the gradation method. The coarse first-level particles are completely surrounded by fine first-level particles. The gradation curve is determined according to the following formula. The coarse aggregate of each grade is graded to determine its mixing ratio: The mixing ratio of each grade of aggregate is determined according to the grade composition; V' i+1 =V i '-V i Where: V i '——the volume of aggregate to be filled in the i-th level, %, where V1 is 100%; V i ——Volume filling rate of aggregate in the i-th grade, %; V' i+1 ——the volume of the next finer aggregate in the i-th grade to be filled, %; d i ——Sieve size of the i-th gear, mm; d i+1 ——Size of the next finer sieve hole of the i-th sieve, mm; a i ——Residue on the sieve of the i-th gear; (3) Filling a portion of the volume with a filler consisting of tailings sand and fly ash, calculating the fineness modulus based on the screening results of the tailings sand and fly ash, and synthesizing the tailings sand and fly ash into medium sand according to the fineness modulus according to the particle size synthesis method, thereby determining the blending ratio between the tailings sand and fly ash; (4) The remaining volume is filled with a gel material composed of water and cement, which wraps the coarse aggregate, tailings sand, and fly ash. The gel material is converted into a sphere of corresponding diameter according to the specific surface area. The gel material wraps the coarse aggregate, tailings sand, and fly ash spheres with a certain film thickness. The volume change before and after wrapping is used to calculate the volume of the gel material. (5) Determine the water-binder ratio based on the designed strength of the prepared self-compacting concrete; (6) According to the volume composition method, calculate 1m 3 The volume of coarse aggregate, filler and gel material in self-compacting concrete is calculated based on the calculated volume usage, material composition and material density. 3 The amount of coarse aggregate, tailings sand, fly ash, cement and water in self-compacting concrete is as follows: aggregate, tailings sand, fly ash, cement, water and admixtures are mixed in a mixer to prepare self-compacting cement concrete.

2. The method for producing a self-compacting concrete mixed with tailings according to claim 1, wherein: According to the particle size synthesis method, tailings sand and fly ash are synthesized into medium sand through the fineness modulus M. The blending ratio between tailings sand and fly ash is determined according to the following formula: P w +P f =100 P w ×M w +P f ×M f =M z Where: P w ——The proportion of tailings sand in filler, %; M w ——fineness modulus of tailings sand; P f ——The proportion of fly ash in filler, %; M f —fineness modulus of fly ash; M z ——The fineness modulus of medium sand should be 2.3 to 3.0; A 0.15 、A 0.3 、A 0.6 、A 1.18 、A 2.36 、A 4.75 are the cumulative percentages of residue on the corresponding sieves.

3. The method for producing a self-compacting concrete mixed with tailings according to claim 1, wherein: According to the following formula, coarse aggregate, tailings sand, and fly ash are converted into spheres of corresponding diameters according to the same specific surface area. The volume of the spheres is converted by wrapping the gel material with a film thickness of 0.02 to 0.04 mm. The volume of the gel material is calculated according to the volume change before and after wrapping according to the following formula: S A =0.41+0.0041a+0.0082b+0.0164c+0.0287d+0.0614e+0.1229f+0.3277g Where: D q ——diameter of a sphere of equal surface area, mm; ρ q ——Density of the raw material of the sphere to be converted, kg / m 3 ; V jt ——Volume of gel material wrapping the raw material of the converted sphere, m 3 ; V c ——Volume of raw materials, m 3 ; u - gel material film thickness, taken as 0.02 ~ 0.04mm; a, b, c, d, e, f, g are the pass rates of sieve holes of 4.75mm and below respectively.

4. The method for producing a self-compacting concrete mixed with tailings according to claim 1, wherein: According to the volume composition method, calculate 1m according to the following formula 3 The volume of coarse aggregate, filler and gel material in self-compacting concrete, and then determine the amount of coarse aggregate, tailings sand, fly ash, cement and water: V0+V s +V j =1m 3 Where: V0——the volume of coarse aggregate, m3; V s ——Volume of packing, m 3 ; V j ——Gel material volume, m 3 .

5. The method for producing self-compacting concrete mixed with tailings according to claim 1, wherein: The tailings sand is one type of tailings sand or a mixture of two or more types of tailings sands.

6. The method for producing self-compacting concrete mixed with tailings according to claim 1, wherein: The external admixtures include a water reducer accounting for 1.5-2% of the total mass of the gel material, a defoamer accounting for 1-1.5% of the total mass of the gel material, heavy calcium powder accounting for 13-18% of the total mass of the gel material, and an air entraining agent accounting for 1-1.5% of the total mass of the gel material.

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