Method for mix proportion design of wet-mix shotcrete based on regulation of plasma membrane layer thickness

Abstract

This invention discloses a mix design method for wet-mix shotcrete based on the control of the slurry film thickness. It relates to the field of wet-mix shotcrete technology for underground hydraulic caverns and includes the following steps: S1, selecting or preparing stone powder, micro-stone powder with a particle size of less than 0.08 mm, and artificial sand; S2, selecting low-density submicron silica; S3, incorporating the micro-stone powder with a particle size of less than 0.08 mm, the low-density submicron silica, and cement into the slurry film layer, and determining the target values ​​tp,targ for the slurry film thickness covering the aggregate surface. This invention solves the quantitative design problem of suitable slurry volume for wet-mix shotcrete that matches aggregate particle size, gradation, and dosage; and "slurry film thickness" replaces "slump" as a quantitative characterization of the effective volume of the slurry, further quantifying the impact of aggregate particle size, gradation, and dosage on the effective volume of the slurry. The slurry film thickness can better characterize the pumping and spraying performance of concrete.

Description

Technical Field

[0001] This invention belongs to the field of wet sprayed concrete technology for underground caverns in hydraulic engineering, specifically relating to a mix design method for artificial sand wet sprayed concrete based on the control of the thickness of the slurry film layer. Background Technology

[0002] Wet-shot concrete is a major support material for water conservancy and hydropower projects such as tunnels, slopes, and underground powerhouses, accounting for as much as 30% to 40% of the total concrete volume. The amount of cementitious material used in wet-shot concrete is generally above 460 kg / m3. As the main building material for the first layer of composite lining structures, its technical requirements for strength grade, impermeability grade, and frost resistance grade are relatively low, but the material cost is very high. Cost reduction and efficiency improvement have always been one of the important tasks in optimizing the mix proportion of wet-shot concrete.

[0003] Conventional mix design primarily uses strength and slump as indicators, determining key parameters such as water-cement ratio, water consumption, sand ratio, and aggregate gradation, resulting in consistently high binder usage per cubic meter. The wet-mix shotcrete construction process generally consists of two stages: pumping and spraying. To meet the dual requirements of easy pumping and adhesion, a certain thickness of slurry layer composed of cementitious materials and water needs to be coated on the aggregate surface, which is the main reason for the high binder usage. In recent years, my country's wet-mix shotcrete technology has largely achieved the replacement of natural aggregates with artificial aggregates, providing a new approach to optimizing cementitious material usage. Artificial sand contains a large amount of micro-stone powder with a particle size of less than 0.08mm, comparable to that of cement. If this micro-stone powder is used as part of the slurry layer, it can replace cement to a certain extent, achieving the technical effect of reducing concrete costs.

[0004] However, when using artificial sand and micro-aggregate powder to partially replace cement in the preparation of wet-mixed shotcrete, three key issues still need to be addressed:

[0005] Firstly, there is a lack of refined design methods for determining the suitability of concrete slurry volume. In current practice, the amount of slurry used is mainly judged based on measured slump and visual observation of aggregate encapsulation. This method is highly subjective and experience-dependent, and does not quantitatively assess the matching between slurry volume and aggregate particle size, gradation, and dosage. This results in significant fluctuations in cementitious material usage, exhibiting the characteristics of a slurry-rich system and persistently high cementitious material consumption.

[0006] Secondly, there is a lack of mature design calculation methods when including micro-aggregate powder with a particle size of less than 0.08 mm in the cementitious material slurry component. Specifically, if this portion of micro-aggregate powder needs to be separated and included in the cementitious material system, the calculation boundary between the total amount of cementitious material slurry and the amount of fine aggregate must be clearly defined. However, existing mix design methods cannot effectively separate and calculate these two components.

[0007] Third, the utilization of artificial sand and gravel powder faces challenges. As an inert filler, the paste layer formed after stone powder replaces cement will reduce the overall activity of the cementitious material system, which is detrimental to the development of compressive strength and setting and hardening speed of wet-sprayed concrete. It may even reduce the thickness of a single spraying and increase the rebound rate. It is necessary to explore a suitable activity compensation mechanism to ensure engineering performance. Summary of the Invention

[0008] The purpose of this invention is to provide a mix design method for wet-mix shotcrete using artificial sand based on the control of the slurry film thickness, thereby solving technical problems in related technologies. To achieve the above objective, this invention provides the following technical solution: a mix design method for wet-mix shotcrete using artificial sand based on the control of the slurry film thickness, comprising the following steps: S1, selecting or preparing stone powder, micro-stone powder with a particle size of less than 0.08 mm, and artificial sand; S2, selecting low-density submicron silica; S3, including the micro-stone powder with a particle size of less than 0.08 mm, the low-density submicron silica, and cement together in the slurry film layer, and determining the target values ​​tp,targ for the thickness of the slurry film layer covering the aggregate surface; S4, with a sand ratio of 60%... Under the conditions of -65% (artificial sand including stone powder with a particle size of less than 0.08mm) and 8%-10% low-density submicron silica content, the initial design mix proportion parameters for wet-mixed shotcrete are as follows: water-cement ratio W / B, cement mass mc, low-density submicron silica mass msi, water content mw, water-reducing agent mass mwr, saturated surface-dry coarse aggregate mass ma,c, and saturated surface-dry artificial sand mass ma,f. S5. Collect cement density ρc, water density ρw, water-reducing agent density ρwr, and saturated surface-dry coarse aggregate mass... Apparent density ρa,c, apparent density of saturated surface-dry artificial sand ρa,f (density of micro-stone powder below 0.08mm is approximately considered the same as the apparent density of saturated surface-dry artificial sand), mass fraction of each particle size range of artificial sand mPa,i, aggregate porosity VFa,v, and other raw material parameters; S6, remove micro-stone powder with a particle size below 0.08mm from the artificial sand, do not include it in the aggregate, and calculate the effective aggregate quantity na,e, effective aggregate radius ra,e, and effective aggregate absolute volume Va,e; S7, remove micro-stone powder with a particle size of 0. Micro-stone powder and low-density submicron silica (below 0.8mm) are included in the slurry film layer along with cement. The slurry volume Vp is calculated, and the slurry film thickness tp,cal is obtained. S8. The calculated slurry film thickness tp,cal is compared with the target value tp,targ. If the two values ​​are consistent, the mix design is completed. If the two values ​​are inconsistent, the water consumption per cubic meter (mw) and / or sand ratio (SP) are adjusted, and the mix design is recalculated until the calculated value tp,cal is consistent with the target value tp,targ. Then the mix design is completed.

[0009] The above-mentioned method for designing the mix proportion of wet-mix shotcrete using artificial sand based on the control of the slurry film thickness, wherein the expression for calculating the slurry film thickness is:

[0010] ;

[0011] In the formula: - Calculated thickness of the slurry film (including stone powder less than 0.08 mm), mm; - The volume of grout (including stone powder smaller than 0.08mm) in a single cubic meter of concrete, in m³ 3 ; -Effective aggregate absolute volume (excluding stone powder smaller than 0.08mm), m 3 ; - Aggregate porosity (excluding stone powder smaller than 0.08mm), % - Quantity of effective aggregate (excluding stone powder smaller than 0.08mm), pieces; - Effective aggregate radius (excluding stone powder smaller than 0.08mm), mm.

[0012] The above-mentioned method for mix design of wet-mix shotcrete based on slurry film thickness control, wherein the volume of slurry in a unit volume of concrete is... The calculation expression is:

[0013] ;

[0014] In the formula: -Water consumption per cubic meter of concrete, kg; - Cement mass in a single cubic meter of concrete, kg; - Mass of low-density submicron silica in a single cubic meter of concrete, kg; - Mass of manufactured sand (including stone powder smaller than 0.08mm) in a single cubic meter of concrete, kg; The percentage of stone powder smaller than -0.08mm in the mass of manufactured sand, % - Mass of water-reducing agent in a single cubic meter of concrete, kg; -Air volume in a single cubic meter of concrete, m 3 ; -Water density, kg / m³ 3 ; - Cement density, kg / m³ 3 ; -Density of low-density submicron silica, kg / m³ 3 ; -Saturated surface-dry apparent density of manufactured sand, kg / m³ 3 ; - Density of water-reducing agent, kg / m³ 3 .

[0015] The above-mentioned method for mix design of wet-mix shotcrete based on the control of slurry film thickness, wherein the effective aggregate absolute volume The calculation expression is:

[0016] ;

[0017] In the formula: - Mass of coarse aggregate in a single cubic meter of concrete, kg; -Saturated surface-dry apparent density of coarse aggregate, kg / m³ 3 .

[0018] The above-mentioned method for designing the mix proportion of wet-mixed shotcrete using artificial sand based on the control of the slurry film thickness, wherein the effective aggregate quantity... The expression is: ;

[0019] In the formula: -Mass fraction of each particle size range of manufactured sand, % - Upper limit of particle size for each aggregate size class, mm; -Lower limit of aggregate size for each size fraction, in mm.

[0020] The above-mentioned method for designing the mix proportion of wet-sprayed concrete using artificial sand based on the control of the slurry film thickness, wherein the effective aggregate radius... The expression is:

[0021] .

[0022] The above-mentioned method for designing the mix proportion of wet sprayed concrete using artificial sand based on the control of the slurry film thickness involves experimentally measuring the aggregate porosity VFa,v. Artificial sand and coarse aggregate are weighed according to the mass sand ratio, and microstone powder smaller than 0.08mm in the artificial sand is sieved out. The remaining artificial sand is then mixed with the coarse aggregate to prepare test samples for testing.

[0023] The above-mentioned method for mix design of wet-mix shotcrete based on slurry film thickness control, wherein the calculated value of the slurry film thickness is... With the target value of the film thickness The two are consistent if the relative deviation between the calculated value and the target value does not exceed 15% of the target value.

[0024] In the above-mentioned method for designing the mix proportion of wet sprayed concrete based on the control of the slurry film thickness, in step S1, the stone powder content is selected or prepared to be 15%-18%, and the content of artificial sand is 8%-10%.

[0025] In the above-mentioned method for designing the mix proportion of wet sprayed concrete using artificial sand based on the control of the slurry film thickness, in step S2, low-density submicron silica with a density of 2100kg / m3-2200kg / m3, a volume average particle size D(4,3) of 100nm-200nm, and a 28d activity index of over 150% is selected.

[0026] The beneficial effects of this invention are:

[0027] 1. This invention solves the quantitative design challenge of determining the appropriate amount of slurry for wet-mix shotcrete that matches aggregate particle size, gradation, and dosage. Conventional mix design methods can only quantify the relative volume of slurry and aggregate, but cannot precisely design the amount of slurry coating the aggregate surface. This invention proposes the technical parameter "slurry film thickness" to replace "slump," providing a quantitative characterization of the effective volume of the slurry. It further quantifies and evaluates the impact of aggregate particle size, gradation, and dosage on the effective volume of the slurry. The slurry film thickness can better characterize the pumping and spraying performance of concrete.

[0028] 2. This invention includes micro-stone powder with a particle size less than 0.08 mm in manufactured sand into the cementitious material slurry component, and proposes calculation methods for the slurry volume including micro-stone powder, the average particle size of manufactured sand and coarse aggregate after deducting micro-stone powder, and the thickness of the slurry layer coating the aggregate surface. This solves the design calculation problem of separating the slurry volume from the aggregate volume when micro-stone powder is included in the cementitious material.

[0029] 3. This invention utilizes inert artificial sand and gravel powder, taking advantage of the low cost of microstone powder and the high activity and large volume of low-density submicron silica, to achieve multiple mixing ratio design effects such as low cementitious material usage, low material cost, and low rebound rate. It also takes into account the thickness, activity, and cost of the slurry layer coating on the aggregate surface, thus achieving the technical goal of cost reduction and efficiency improvement.

[0030] Of course, any product implementing this invention does not necessarily need to achieve all of the above advantages at the same time. Attached Figure Description

[0031] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This invention relates to a flowchart of a method for designing mix proportions of wet-mix shotcrete using artificial sand based on the control of the slurry film thickness.

[0033] Figure 2 The diagram shows the preliminary mix design results of C20 wet sprayed concrete based on the artificial sand wet sprayed concrete mix design method involving the control of the slurry layer thickness.

[0034] Figure 3 The mix design diagram for C20 wet sprayed concrete is shown in the example of the artificial sand wet sprayed concrete mix design method based on the control of the slurry film thickness.

[0035] Figure 4The diagram shows the preliminary mix design results of C30 wet sprayed concrete based on the artificial sand wet sprayed concrete mix design method involving the control of the slurry film thickness.

[0036] Figure 5 This is a mix design diagram for C30 wet sprayed concrete based on the artificial sand wet sprayed concrete mix design method involving the control of slurry layer thickness. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] like Figure 1-5As shown, this invention provides a mix design method for wet-mix shotcrete based on the control of the slurry film thickness, comprising the following steps: S1, selecting or preparing stone powder, specifically micro-stone powder with a particle size of less than 0.08 mm, and artificial sand; S2, selecting low-density submicron silica; S3, including the micro-stone powder with a particle size of less than 0.08 mm, the low-density submicron silica, and cement together in the slurry film layer, and determining the target values ​​tp,targ for the thickness of the slurry film layer covering the aggregate surface; S4, with a sand ratio of 60%-65% (in artificial sand... Including stone powder with a particle size of less than 0.08mm and low-density submicron silica content of 8%-10%, the initial design parameters for wet-mixed sprayed concrete include the water-cement ratio W / B, cement mass mc, low-density submicron silica mass msi, water content mw, water-reducing agent mass mwr, saturated surface-dry coarse aggregate mass ma,c, and saturated surface-dry manufactured sand mass ma,f, etc.; S5, collect cement density ρc, water density ρw, water-reducing agent density ρwr, and saturated surface-dry coarse aggregate apparent density ρa. c. Apparent density ρa,f of saturated surface-dry manufactured sand (density of micro-stone powder below 0.08mm is approximately considered the same as the apparent density of saturated surface-dry manufactured sand), mass fraction (mPa,i) of each particle size range of manufactured sand, aggregate porosity (VFa,v), and other raw material parameters; S6. Remove micro-stone powder below 0.08mm from the manufactured sand, excluding it from the aggregate, and calculate the effective aggregate quantity na,e, effective aggregate radius ra,e, and effective aggregate absolute volume Va,e; S7. Remove micro-stone powder below 0.08mm from the manufactured sand, excluding it from the aggregate, and calculate the effective aggregate quantity na,e, effective aggregate radius ra,e, and effective aggregate absolute volume Va,e; Micro-stone powder and low-density submicron silica (below m) are included in the slurry film layer along with cement. The slurry volume Vp is calculated, and the slurry film thickness tp,cal is obtained. S8. The calculated slurry film thickness tp,cal is compared with the target value tp,targ. If the two values ​​are consistent, the mix design is completed. If the two values ​​are inconsistent, the water consumption per cubic meter mw and / or sand ratio SP are adjusted, and the mix design is recalculated until the calculated value tp,cal is consistent with the target value tp,targ. Then the mix design is completed.

[0039] The formula for calculating the thickness of the slurry film layer is as follows:

[0040] ;

[0041] In the formula: - Calculated thickness of the slurry film (including stone powder less than 0.08 mm), mm; - The volume of grout (including stone powder smaller than 0.08mm) in a single cubic meter of concrete, in m³ 3 ; -Effective aggregate absolute volume (excluding stone powder smaller than 0.08mm), m 3 ; - Aggregate porosity (excluding stone powder smaller than 0.08mm), % - Quantity of effective aggregate (excluding stone powder smaller than 0.08mm), pieces; - Effective aggregate radius (excluding stone powder smaller than 0.08mm), mm.

[0042] The volume of slurry in the single cubic meter concrete The calculation expression is:

[0043] ;

[0044] In the formula: -Water consumption per cubic meter of concrete, kg; - Cement mass in a single cubic meter of concrete, kg; - Mass of low-density submicron silica in a single cubic meter of concrete, kg; - Mass of manufactured sand (including stone powder smaller than 0.08mm) in a single cubic meter of concrete, kg; The percentage of stone powder smaller than -0.08mm in the mass of manufactured sand, % - Mass of water-reducing agent in a single cubic meter of concrete, kg; -Air volume in a single cubic meter of concrete, m 3 ; -Water density, kg / m³ 3 ; - Cement density, kg / m³ 3 ; -Density of low-density submicron silica, kg / m³ 3 ; -Saturated surface-dry apparent density of manufactured sand, kg / m³ 3 ; - Density of water-reducing agent, kg / m³ 3 .

[0045] The absolute volume of the effective aggregate The calculation expression is:

[0046] ;

[0047] In the formula: - Mass of coarse aggregate in a single cubic meter of concrete, kg; -Saturated surface-dry apparent density of coarse aggregate, kg / m³ 3 .

[0048] The effective aggregate quantity The expression is:

[0049] ;

[0050] In the formula: -Mass fraction of each particle size range of manufactured sand, % - Upper limit of particle size for each aggregate size class, mm; -Lower limit of aggregate size for each size fraction, in mm.

[0051] The effective aggregate radius The expression is:

[0052] .

[0053] The aggregate porosity VFa,v was measured experimentally. Artificial sand and coarse aggregate were weighed according to the mass sand ratio. Microstone powder smaller than 0.08mm in the artificial sand was removed by sieving. The remaining artificial sand and coarse aggregate were then mixed to prepare test samples for testing.

[0054] The calculated value of the thickness of the slurry film layer With the target value of the film thickness The two are consistent if the relative deviation between the calculated value and the target value does not exceed 15% of the target value.

[0055] In step S1, the stone powder content is selected or prepared to be 15%-18%, and the artificial sand content is 8%-10%.

[0056] In step S2, low-density submicron silica with a density of 2100kg / m3-2200kg / m3, a volume average particle size D(4,3) of 100nm-200nm, and a 28d activity index of over 150% is selected.

[0057] The relevant specific embodiments of the present invention are as follows:

[0058] Example 1:

[0059] S1. Select limestone artificial sand with a stone powder content of 16% and a micro stone powder content of less than 0.08mm as the key material for mix design;

[0060] S2, Select a density of 2160 kg / m³ 3 Volume average particle size D （4,3） 172nm, 28d activity index 166% low-density submicron silica is used as a key material in mix design;

[0061] The low-density submicron silica was provided by Changchun Dongkan New Building Materials Co., Ltd.

[0062] S3. Incorporate micro stone powder with a particle size of less than 0.08 mm, low-density submicron silica, and cement into the slurry film layer, and determine the target value of 0.030 mm for the thickness of the slurry film layer covering the aggregate surface.

[0063] S4. For the mix design of wet-mix shotcrete with strength grade C20 and slump of 160mm~200mm, under the conditions of sand ratio of 64% (artificial sand including stone powder with a particle size of less than 0.08mm) and low-density submicron silica content of 10%, the initial design wet-mix shotcrete water-cement ratio is 0.48 and cement mass is 377kg / m³. 3 Low-density submicron silica, mass 42 kg / m³ 3 Water consumption: 201 kg / m³ 3 Water-reducing agent mass: 4.19 kg / m³ 3 614 kg / m³ of coarse aggregate in saturated surface-dry state 3 The mass of saturated surface-dry artificial sand is 1091 kg / m³. 3 ;

[0064] S5, Cement density collected: 3.08 g / cm³ 3 Water density 1.00 g / cm³ 3 Water-reducing agent density 1.02 g / cm³ 3 The apparent density of coarse aggregate in its saturated surface-dry state is 2.67 g / cm³. 3 The apparent density of saturated surface-dry artificial sand is 2.64 g / cm³. 3 (The density of micro-stone powder below 0.08mm is approximately considered to be the same as the apparent density of saturated surface-dry manufactured sand). In the mass fraction of each particle size range of manufactured sand, 2.5mm-5mm manufactured sand accounts for 4.8%, 1.25mm-2.5mm manufactured sand accounts for 15.5%, 0.63mm-1.25mm manufactured sand accounts for 26.8%, 0.315mm-0.63mm manufactured sand accounts for 23.6%, 0.16mm-0.315mm manufactured sand accounts for 13.3%, 0.08mm-0.16mm manufactured sand accounts for 6.4%, and 0-0.08mm manufactured sand accounts for 9.6%. The aggregate porosity is 34.6%. Preliminary mix design results are shown below. Figure 2 As shown.

[0065] The cement is P·O42.5 ordinary Portland cement produced by Shangzhi Jinshi Cement Co., Ltd. The parent rock for both the crushed stone coarse aggregate and the artificial sand is limestone. The coarse aggregate particle size ranges from 5mm to 10mm; the artificial sand particle size ranges from 0mm to 5mm, with a fineness modulus of 3.0. The water-reducing agent is a standard high-performance water-reducing agent provided by Changchun Dongkan New Building Materials Co., Ltd., with a dosage of 1.0% and a water reduction rate of 29.6%.

[0066] S6. Remove the microstone powder with a particle size of less than 0.08 mm from the artificial sand, do not include it in the aggregate, calculate the effective aggregate quantity as 39,130,970 pieces, the effective aggregate radius as 1.5444 mm, and the effective aggregate absolute volume as 603 L.

[0067] S7. Microstone powder with a particle size of less than 0.08 mm, low-density submicron silica and cement are included in the slurry film layer. The slurry volume is calculated to be 392 L and the slurry film thickness is calculated to be 0.060 mm.

[0068] S8. Comparing the calculated thickness of the slurry film layer of 0.060 mm with the target value of 0.030 mm, the calculated value is too large, exceeding 100% of the target value and greater than 15%, and the two do not match.

[0069] Adjust the unit water consumption from 201 kg / m³ 3 Reduced to 185 kg / m 3 The sand ratio remains unchanged at 64%; the water-cement ratio is 0.48; and the cement mass is 347 kg / m³. 3 Low-density submicron silica, mass 39 kg / m³ 3 Water consumption: 185 kg / m³ 3 Water-reducing agent mass: 3.85 kg / m³ 3 640 kg / m³ of coarse aggregate in saturated surface-dry state 3 The mass of saturated surface-dry artificial sand is 1138 kg / m³. 3 Aggregate porosity 34.6%, effective aggregate quantity 40,810,863, effective aggregate radius 1.5444 mm, effective aggregate absolute volume 629 L; slurry volume (Including stone powder smaller than 0.08mm) 367L, calculate the thickness of the slurry coating on the aggregate surface, i.e. the thickness of the slurry film layer, and get a calculated value of 0.028mm.

[0070] The calculated thickness of the slurry film layer is 0.028 mm, which has a relative deviation of 7% from the target value of 0.030 mm. Since this deviation is less than 15%, the calculated value is considered to match the target value, and the mix design is complete. Figure 3 As shown.

[0071] Example 2:

[0072] S1. Select limestone artificial sand with a stone powder content of 16% and a micro stone powder content of less than 0.08mm as the key material for mix design;

[0073] S2, Select a density of 2160 kg / m³ 3 Volume average particle size D （4,3） 172nm, 28d activity index 166% low-density submicron silica is used as a key material in mix design;

[0074] The low-density submicron silica was provided by Changchun Dongkan New Building Materials Co., Ltd.

[0075] S3. Incorporate micro stone powder with a particle size of less than 0.08 mm, low-density submicron silica, and cement into the slurry film layer, and determine the target value of the slurry film layer thickness covering the aggregate surface as 0.050 mm.

[0076] S4. For the mix design of wet-mix shotcrete with strength grade C30 and slump of 160mm~200mm, under the conditions of sand ratio of 60% (artificial sand including stone powder with a particle size of less than 0.08mm) and low-density submicron silica content of 10%, the initial design wet-mix shotcrete water-cement ratio is 0.42 and cement mass is 386kg / m³. 3 Low-density submicron silica, mass 43 kg / m³ 3 Water consumption: 180 kg / m³ 3 Water-reducing agent mass: 4.29 kg / m³ 3 701 kg / m³ of coarse aggregate in saturated surface-dry state 3 The mass of saturated surface-dry artificial sand is 1051 kg / m³. 3 ;

[0077] S5, Cement density collected: 3.08 g / cm³ 3 Water density 1.00 g / cm³ 3 Water-reducing agent density 1.02 g / cm³ 3 The apparent density of coarse aggregate in its saturated surface-dry state is 2.67 g / cm³. 3 The apparent density of saturated surface-dry artificial sand is 2.64 g / cm³. 3 (The density of micro-stone powder below 0.08mm is approximately considered to be the same as the apparent density of saturated surface-dry manufactured sand). In the mass fraction of each particle size range of manufactured sand, 2.5mm-5mm manufactured sand accounts for 4.8%, 1.25mm-2.5mm manufactured sand accounts for 15.5%, 0.63mm-1.25mm manufactured sand accounts for 26.8%, 0.315mm-0.63mm manufactured sand accounts for 23.6%, 0.16mm-0.315mm manufactured sand accounts for 13.3%, 0.08mm-0.16mm manufactured sand accounts for 6.4%, and 0-0.08mm manufactured sand accounts for 9.6%. The aggregate porosity is 34.9%. Preliminary mix design results are shown below. Figure 4 As shown.

[0078] The cement is P·O42.5 ordinary Portland cement produced by Shangzhi Jinshi Cement Co., Ltd. The parent rock for both the crushed stone coarse aggregate and the artificial sand is limestone. The coarse aggregate particle size ranges from 5mm to 10mm; the artificial sand particle size ranges from 0mm to 5mm, with a fineness modulus of 3.0. The water-reducing agent is a standard high-performance water-reducing agent provided by Changchun Dongkan New Building Materials Co., Ltd., with a dosage of 1.0% and a water reduction rate of 29.6%.

[0079] S6. Remove the microstone powder with a particle size of less than 0.08 mm from the artificial sand, do not include it in the aggregate, calculate the effective aggregate quantity as 37,705,204 pieces, the effective aggregate radius as 1.5799 mm, and the effective aggregate absolute volume as 622 L.

[0080] S7. Including micro stone powder with a particle size of less than 0.08 mm, low-density submicron silica, and cement in the slurry film layer, the slurry volume is calculated to be 373 L, and the slurry film thickness is calculated to be 0.032 mm.

[0081] S8. Comparing the calculated thickness of the slurry film layer (0.032 mm) with the target value (0.050 mm), the calculated value is too large, exceeding the target value by 36% and by more than 15%, and the two do not match.

[0082] Adjust the unit water consumption from 180 kg / m³ 3 Increased to 183 kg / m 3 The sand ratio was increased from 60% to 65%, the water-cement ratio was 0.42, and the cement mass was 392 kg / m³. 3 Low-density submicron silica, mass 44 kg / m³ 3 Water consumption: 183 kg / m³ 3 Water-reducing agent mass: 4.36 kg / m³ 3 608 kg / m³ of coarse aggregate in saturated surface-dry state 3 The mass of fine aggregate in saturated surface-dry state is 1129 kg / m³. 3 Aggregate porosity 34.6%, effective aggregate quantity 40,484,938, effective aggregate radius 1.5360 mm, effective aggregate absolute volume 614 L; slurry volume (Including stone powder smaller than 0.08mm) 382L, calculate the thickness of the slurry coating on the aggregate surface, i.e. the thickness of the slurry film layer, and get a calculated value of 0.046mm.

[0083] The calculated thickness of the slurry film layer is 0.046 mm, which has a relative deviation of 8% from the target value of 0.050 mm. Since this deviation is less than 15%, the calculated value is considered to match the target value, and the mix design is complete. Figure 5 As shown.

[0084] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for mix design of wet-mix shotcrete using artificial sand based on the control of slurry film thickness, characterized in that, Includes the following steps: S1. Select or prepare stone powder, micro stone powder with a particle size of less than 0.08 mm, and artificial sand; S2. Select low-density submicron silica; S3. Incorporate micro stone powder with a particle size of less than 0.08 mm, low-density submicron silica, and cement into the slurry film layer, and determine the target values ​​tp, targ for the thickness of the slurry film layer covering the aggregate surface. S4. Under the conditions of sand ratio of 60%-65% (artificial sand includes stone powder with a particle size of less than 0.08mm) and low-density submicron silica content of 8%-10%, design the initial selection of mix proportion parameters for wet sprayed concrete, such as water-cement ratio W / B, cement mass mc, low-density submicron silica mass msi, water content mw, water-reducing agent mass mwr, saturated surface-dry coarse aggregate mass ma,c, and saturated surface-dry artificial sand mass ma,f. S5. Collect cement density ρc, water density ρw, water-reducing agent density ρwr, apparent density of coarse aggregate in saturated surface-dry state ρa,c, apparent density of artificial sand in saturated surface-dry state ρa,f (the density of micro stone powder below 0.08mm is approximately regarded as the same as the apparent density of artificial sand in saturated surface-dry state), mass fraction of artificial sand in each particle size range mPa,i, aggregate porosity VFa,v and other raw material parameters. S6. Remove micro-stone powder with a particle size of less than 0.08 mm from the artificial sand, do not include it in the aggregate, and calculate the effective aggregate quantity na,e, effective aggregate radius ra,e, and effective aggregate absolute volume Va,e. S7. Incorporate micro-stone powder and low-density submicron silica with a particle size of less than 0.08 mm into the slurry film layer along with cement, calculate the slurry volume Vp, and obtain the calculated value tp,cal of the slurry film layer thickness. S8. Compare the calculated value tp,cal of the slurry film thickness with the target value tp,targ. If the two values ​​are consistent, the mix design is complete. If the two values ​​are inconsistent, adjust the unit water consumption mw and / or sand ratio SP, and recalculate the mix design until the calculated value tp,cal is consistent with the target value tp,targ. Then the mix design is complete.

2. The method for mix design of wet-mix shotcrete based on the control of slurry film thickness according to claim 1, characterized in that, The formula for calculating the thickness of the slurry film layer is as follows: ； In the formula: - Calculated thickness of the slurry film (including stone powder less than 0.08 mm), mm; - The volume of grout (including stone powder smaller than 0.08mm) in a single cubic meter of concrete, in m³ 3 ; -Effective aggregate absolute volume (excluding stone powder smaller than 0.08mm), m 3 ; - Aggregate porosity (excluding stone powder smaller than 0.08mm), % - Quantity of effective aggregate (excluding stone powder smaller than 0.08mm), pieces; - Effective aggregate radius (excluding stone powder smaller than 0.08mm), mm.

3. The method for mix design of wet-mix shotcrete based on the control of slurry film thickness according to claim 2, characterized in that, The volume of slurry in the unit volume concrete The calculation expression is: ； In the formula: -Water consumption per cubic meter of concrete, kg; - Cement mass in a single cubic meter of concrete, kg; - Mass of low-density submicron silica in a single cubic meter of concrete, kg; - Mass of manufactured sand (including stone powder smaller than 0.08mm) in a single cubic meter of concrete, kg; The percentage of stone powder smaller than -0.08mm in the mass of manufactured sand, % - Mass of water-reducing agent in a single cubic meter of concrete, kg; -Air volume in a single cubic meter of concrete, m 3 ; -Water density, kg / m³ 3 ; - Cement density, kg / m³ 3 ; -Density of low-density submicron silica, kg / m³ 3 ; -Saturated surface-dry apparent density of manufactured sand, kg / m³ 3 ; - Density of water-reducing agent, kg / m³ 3 .

4. The method for mix design of wet-mix shotcrete based on slurry film thickness control according to claim 3, characterized in that, The absolute volume of the effective aggregate The calculation expression is: ； In the formula: - Mass of coarse aggregate in a single cubic meter of concrete, kg; -Saturated surface-dry apparent density of coarse aggregate, kg / m³ 3 .

5. The method for mix design of wet-mix shotcrete based on the control of slurry film thickness according to claim 4, characterized in that, The effective aggregate quantity The expression is: ； In the formula: -Mass fraction of each particle size range of manufactured sand, % - Upper limit of particle size for each aggregate size class, mm; -Lower limit of aggregate size for each size fraction, in mm.

6. The method for mix design of wet-mix shotcrete based on slurry film thickness control according to claim 5, characterized in that, The effective aggregate radius The expression is: 。 7. The method for mix design of wet-mix shotcrete based on slurry film thickness control according to claim 6, characterized in that, The aggregate porosity VFa,v was measured experimentally. Artificial sand and coarse aggregate were weighed according to the mass sand ratio. Microstone powder smaller than 0.08mm in the artificial sand was removed by sieving. The remaining artificial sand and coarse aggregate were then mixed to prepare test samples for testing.

8. The method for mix design of wet-mix shotcrete based on the control of slurry film thickness according to claim 7, characterized in that, The calculated value of the thickness of the slurry film layer With the target value of the film thickness The two conditions are met if the relative deviation between the calculated value and the target value does not exceed 15% of the target value.

9. The method for mix design of wet-mix shotcrete based on the control of slurry film thickness according to claim 1, characterized in that, In step S1, the stone powder content is selected or prepared to be 15%-18%, and the artificial sand content is 8%-10%.

10. The method for mix design of wet-mix shotcrete based on the control of slurry film thickness according to claim 1, characterized in that, In step S2, low-density submicron silica with a density of 2100kg / m3-2200kg / m3, a volume average particle size D(4,3) of 100nm-200nm, and a 28d activity index of over 150% is selected.

Images