Steel fiber equivalent hybrid analysis and evaluation method for reactive powder concrete

Abstract

The application discloses a kind of steel fiber equivalent mixed analysis and evaluation method of active powder concrete, and its benchmark group selects flat steel fiber as benchmark toughening steel fiber, and experimental group selects benchmark toughening steel fiber and mixes additional steel fiber of multiple flat or wave type.When experimental group mixes steel fiber of same kind, different specifications, if the ratio of the volume content of steel fiber of benchmark group and the diameter of steel fiber is less than or equal to the sum of the ratio of the volume content of various steel fiber in experimental group and the diameter of steel fiber, it is equivalent mixed;When experimental group mixes multiple steel fibers of different kinds, different specifications, if the product of the volume content of steel fiber of benchmark group and the adhesion coefficient is less than or equal to the sum of the ratio of the product of the volume content of various steel fiber in experimental group and the adhesion coefficient, it is equivalent mixed.The method of the application is scientific and accurate, simple and easy to understand, and has strong operability and accuracy.

Description

TECHNICAL FIELD

[0001] The present application relates to reactive powder concrete, in particular to a steel fiber equivalent mixing analysis and evaluation method of reactive powder concrete. BACKGROUND

[0002] Reactive powder concrete (RPC) improves the fineness and the number of active powder of material components, reduces the internal defects of the material, eliminates coarse aggregate, reduces the maximum size of the particles, reduces the transition zone, improves the uniformity of the material, optimizes the particle size distribution to achieve the optimal packing density, and realizes the low water-binder ratio, so as to realize the excellent performance of high strength, high toughness and high durability at the same time.

[0003] Steel fiber is an important toughening material in reactive powder concrete, which is characterized by random distribution in the system. The commonly used steel fibers include straight type, end hook type and wave type, and the materials include copper plating, zinc plating and stainless steel, etc. The toughening mechanism mainly relies on the interfacial frictional adhesion between steel fiber and matrix or the mechanical anchoring occlusion force of its physical structure.

[0004] At present, the method for equivalent mixing of steel fiber of reactive powder concrete mainly sets a reference group and a plurality of experimental groups with different mixing ratios, and analyzes and evaluates the mixing effect of steel fiber of reactive powder concrete according to the actual experimental data of the reference group and the experimental groups. This method does not have a complete scientific analysis guide method for the pre-analysis and evaluation of the equivalent mixing effect of steel fiber of reactive powder concrete, resulting in that the reference group and the experimental groups set by this method are too complex, and the experimental success probability is low. SUMMARY

[0005] The technical problem to be solved by the present application is that there is no specific analysis and evaluation method for the equivalent mixing of steel fiber of reactive powder concrete to guide people to reasonably and scientifically calculate and evaluate in the pre-experimental group. The present application provides a steel fiber equivalent mixing analysis and evaluation method of reactive powder concrete, which is simple and easy to operate, and has strong operability and accuracy.

[0006] To solve the above technical problems, the present application adopts the following technical scheme:

[0007] A steel fiber equivalent mixing analysis and evaluation method of reactive powder concrete, which sets a reference group and an experimental group, the reactive powder concrete of the reference group selects a certain straight steel fiber as the reference toughening steel fiber, and the reactive powder concrete of the experimental group selects the reference toughening steel fiber and 1-n additional straight or wave steel fibers for mixing, the steel fiber equivalent mixing analysis and evaluation method of the experimental group is:

[0008] When the reactive powder concrete in the experimental group was mixed with multiple steel fibers of the same type and different specifications, only those that met The steel fiber admixture in reactive powder concrete is equivalent to the admixture;

[0009] When different types and specifications of steel fibers were mixed into the active powder concrete of the experimental group, only those that met When the steel fiber admixture in reactive powder concrete is equivalent to that in the mixed concrete,

[0010] Where: ω0: the volume content of the benchmark toughening steel fiber in the benchmark reactive powder concrete, unit: kg / m 3 ;

[0011] d0: the average diameter of the benchmark toughening steel fibers in the benchmark reactive powder concrete, in mm;

[0012] η0: Bond coefficient of the benchmark toughened steel fiber in the benchmark reactive powder concrete, unit N / mm 2 ;

[0013] ω1, ω2......ω n : are the volumetric dosages of the benchmark toughening steel fiber and various additional steel fibers in the experimental group, in kg / m 3 ;

[0014] d1, d2......d n : are the diameters of the baseline toughening steel fibers and various additional steel fibers in the experimental group, in mm;

[0015] η1, η2......η n : are the bonding coefficients of the benchmark toughened steel fibers and various additional steel fibers in the experimental group, in N / mm 2 .

[0016] The bonding coefficient is in direct proportion to the product of the steel fiber anchoring factor, the material friction factor and the dispersion contribution factor.

[0017] The present application is based on the fact that the size (length / diameter) of the steel fiber determines the bonding area s of the interface between the steel fiber and the matrix, the volume content ω of the steel fiber determines the total number n of the steel fiber of this size, and the toughening mechanism of the steel fiber in the reactive powder concrete mainly relies on the interfacial frictional bonding force or the mechanical anchoring engagement force of the physical structure between the steel fiber and the matrix, so the total tensile force value ∑f of the steel fiber is in a proportional relationship with the product of the number b of the steel fiber, the bonding area s (i.e. the surface area of the steel fiber ignoring the end surface area) and the bonding coefficient η: ∑f∝ηns, wherein the bonding coefficient η is in a proportional relationship with the product of the shape (anchoring factor δ1) of the steel fiber, the material (friction factor δ2) and the dispersion degree (contribution factor δ3): η∝δ1δ2δ3.

[0018] After mixing several kinds of steel fibers, the total toughening effect of the mixed steel fibers on the reactive powder concrete should be the sum of the total tensile force values of the steel fibers, i.e. ∑f1+∑f2+......+∑f n According to the mixing equivalent principle, there is ∑f0≤∑f1+∑f2+......+∑f n That is, if the experimental group of the reactive powder concrete mixes multiple steel fibers of the same type but different sizes, only when ∑f0≤∑f1+∑f2+......+∑f is met, the steel fiber mixing of the reactive powder concrete is equivalent mixing.

[0019] If the experimental group of the reactive powder concrete mixes multiple steel fibers of different types and different sizes, only when ∑f0≤∑f1+∑f2+......+∑f is met, the steel fiber mixing of the reactive powder concrete is equivalent mixing, wherein ∑f0 is the total tensile force value of the reference toughening steel fiber in the reactive powder concrete of the reference group, and ∑f1, ∑f2,..., ∑fn are the total tensile force values of the reference toughening steel fiber and various additional steel fibers in the reactive powder concrete of the experimental group, respectively. n

[0020] Compared with the prior art, the present application has the following beneficial effects:

[0021] 1) The present application first proposes a steel fiber equivalent mixing analysis and evaluation method for reactive powder concrete;

[0022] 2) The steel fiber equivalent mixing analysis and evaluation formula for reactive powder concrete provided by the present application is derived based on the steel fiber toughening mechanism principle, and has strong scientificity and logicality;

[0023] 3) The steel fiber equivalent mixing analysis and evaluation method for reactive powder concrete of the present application starts from the steel fiber toughening mechanism principle, and can not only provide a more scientific preliminary analysis for the steel fiber mixing experiment of the reactive powder concrete, but also can systematically evaluate whether the mixed reactive powder concrete is equivalent mixing.​

[0024] 4) The present invention covers the equivalent mixing of steel fibers of the same type but different specifications and the equivalent mixing of steel fibers of different types but different specifications in reactive powder concrete, and has a wide applicability and can meet the application of most mixing situations. DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with specific preferred embodiments, but the scope of protection of the present invention is not limited thereby.

[0026] The basic formula calculation and derivation process of the steel fiber equivalent mixing analysis and evaluation method of the reactive powder concrete of the present invention are as follows:

[0027] 1) Taking the straight copper-plated fine steel fiber as the toughening material for reactive powder concrete as an example, the calculation formula for its single fiber volume υ (i.e. the volume of a single steel fiber) is as follows:

[0028]

[0029] Where: υ: the volume of the single fiber of the straight copper-plated fine steel fiber, unit: m 3 ;

[0030] d: diameter of straight copper-plated fine steel fiber, unit: mm;

[0031] l: Length of straight copper-plated fine steel fiber, unit: mm.

[0032] The calculation formula of its single fiber surface area s0 (i.e. the bonding area s between a single steel fiber and the matrix interface) is as follows:

[0033]

[0034] Where: s0: surface area of ​​straight copper-plated fine steel fiber (ignoring end surface area), unit: m 2 ;

[0035] d: diameter of straight copper-plated fine steel fiber, unit: mm;

[0036] l: Length of straight copper-plated fine steel fiber, unit: mm.

[0037] 2) If the volume content of the straight copper-plated fine steel fiber is ω, then based on the relationship between the volume content and the volume of the steel fiber monofilament, the number of steel fibers b at the content of ω can be calculated. The calculation formula is as follows:

[0038]

[0039] Where: b: the number of straight copper-plated fine steel fibers at the ω dosage, which is a dimensionless number;

[0040] ω: volume fraction of flat copper-coated micro steel fiber, unit kg / m 3 ;

[0041] d: diameter of flat copper-coated micro steel fiber, unit mm;

[0042] l: length of flat copper-coated micro steel fiber, unit mm.

[0043] 3) According to the toughening mechanism of steel fiber in reactive powder concrete, it mainly relies on the interfacial frictional adhesion or physical structure mechanical anchoring bite force between steel fiber and matrix, that is, the total tensile strength value of steel fiber ∑f and the number of steel fiber b, the bonding area s (the surface area s0 of steel fiber single wire) and the bonding coefficient η exist the following relationship:

[0044] ∑f∝ηns, that is, ∑f∝ηns0;

[0045] Wherein, ∑f is the total tensile strength value of reactive powder concrete, unit N;

[0046] b: the number of flat copper-coated micro steel fiber under ω fraction, dimensionless;

[0047] s0: surface area of flat copper-coated micro steel fiber single wire, unit m 2 ;

[0048] η: bonding coefficient of flat copper-coated micro steel fiber and matrix interface, unit N / mm 2 ; which is related to the shape of steel fiber (anchoring factor δ1), material (friction factor δ2) and dispersion degree (contribution factor δ3), that is, η∝δ1δ2δ3. When flat copper-coated micro steel fiber is selected, its anchoring factor δ1 can be 1.00.

[0049] 4) If the same kind (i.e. same material) and different specifications (i.e. different length-diameter ratio) of multiple steel fibers are mixed in reactive powder concrete, only when ∑f0≤∑f1+∑f2+......+∑f n , the steel fiber mixed in reactive powder concrete is equivalent mixing, so the following analysis and evaluation formula is derived:

[0050]

[0051] If different kinds and different specifications of multiple steel fibers are mixed in reactive powder concrete, the same reason is that only when ∑f0≤∑f1+∑f2+......+∑f n , the steel fiber mixed in reactive powder concrete is equivalent mixing, so the following analysis and evaluation formula is derived:

[0052] (n is a natural number greater than 1);

[0053] ∑f0 is the total tensile strength value of the reference toughening steel fiber in the reference group of reactive powder concrete;

[0054] ∑f1, ∑f2,..., ∑f n are the total tensile strength values of the reference toughening steel fiber and various additional steel fibers in the experimental group of reactive powder concrete, respectively;

[0055] ω0 is the volume content of the reference toughening steel fiber in the reference group of reactive powder concrete, in kg / m 3 ;

[0056] d0 is the diameter of the reference toughening steel fiber in the reference group of reactive powder concrete, in mm;

[0057] η0 is the adhesion coefficient of the reference toughening steel fiber in the reference group of reactive powder concrete, in N / mm 2 ;

[0058] ω1, ω2,..., ω n are the volume contents of the reference toughening steel fiber and various additional steel fibers in the experimental group of reactive powder concrete, in kg / m 3 ;

[0059] d1, d2,..., d n are the diameters of the reference toughening steel fiber and various additional steel fibers in the experimental group of reactive powder concrete, in mm.

[0060] η1, η2,..., η n are the adhesion coefficients of the reference toughening steel fiber and various additional steel fibers in the experimental group of reactive powder concrete, in N / mm 2 .

[0061] The application example 1 of the present application is as follows:

[0062] A reactive powder concrete currently uses a flat copper-plated micro steel fiber as the reference toughening steel fiber, which has a length of 13 mm, a diameter of 0.20 mm, and a volume content of 2%. Another flat copper-plated micro steel fiber is prepared to be mixed with the current steel fiber, which has a length of 8 mm, a diameter of 0.15 mm, and a volume content of 0.5%. The volume content of the reference steel fiber is adjusted to 1.5%. It is necessary to analyze and evaluate whether the steel fiber mixing scheme of the reactive powder concrete is reasonable.

[0063] According to the steel fiber equivalent mixing analysis and evaluation method of the reactive powder concrete of the present application, since the two steel fibers used for mixing are of the same type but different specifications, the following formula can be used for calculation:

[0064]

[0065] Substitute data, easy to get:

[0066]

[0067] Therefore, this mixing scheme meets the requirements of active powder concrete steel fiber equivalent mixing, and the strength of this mixing scheme is slightly higher than the benchmark group from the data.

[0068] Application Example 2:

[0069] There is a kind of active powder concrete which selects flat copper-plated micro steel fiber as the benchmark toughening steel fiber, the specification is 13mm in length and 0.20mm in diameter, and the volume content is 2%. Now another flat copper-plated micro steel fiber is prepared to be mixed with the existing steel fiber, the specification of the steel fiber is 10mm in length and 0.18mm in diameter, the volume content of the benchmark steel fiber is adjusted to 1.2%, and now it is necessary to analyze and evaluate the steel fiber mixing scheme of the active powder concrete, and determine the reasonable content of the steel fiber with length of 10mm and diameter of 0.18mm.

[0070] According to the steel fiber equivalent mixing analysis and evaluation method of the active powder concrete of the application, since the two steel fibers for mixing are of the same kind and different specifications, the following formula can be used for calculation:

[0071]

[0072] Substitute data, easy to get:

[0073]

[0074] Then:

[0075]

[0076] It can be seen that: the volume content ω2 of the steel fiber with length of 10mm and diameter of 0.18mm is greater than or equal to 0.72%, which can meet the requirements of active powder concrete steel fiber equivalent mixing.

[0077] Application Example 3:

[0078] A reactive powder concrete currently uses straight copper-coated fine steel fibers as the baseline toughening fibers. These fibers have a length of 13 mm, a diameter of 0.20 mm, and a volumetric content of 2%. A different type of corrugated copper-coated fine steel fibers, 10 mm in length and 0.15 mm in diameter, is now being mixed with the existing fibers. Based on CECS 13-2009, "Test Methods for Bond Strength of Steel Fibers to Cement Pastes," fiber-matrix bond performance tests were conducted using figure-eight specimens. Based on the distribution of the two types of steel fibers, the relationship between the bond coefficient η0 of the baseline straight steel fibers and the bond coefficient η1 of the corrugated steel fibers was determined: 1.3η0 = η1. The volumetric content of the baseline steel fibers was adjusted to 1%. An equivalent mixing analysis and evaluation of the steel fiber mixing scheme for this reactive powder concrete is required. What is the reasonable volumetric content of corrugated steel fibers with a length of 10 mm and a diameter of 0.15 mm?

[0079] According to the steel fiber equivalent blending analysis and evaluation method for reactive powder concrete of the present invention, since the two steel fibers used for blending are of different types and specifications, the following formula can be used for calculation:

[0080]

[0081] Substituting the data, we can easily get:

[0082]

[0083] but:

[0084]

[0085] It can be seen from this that the volume content of corrugated steel fiber with a length of 10 mm and a diameter of 0.15 mm ω2 ≥ 0.577% can meet the requirements of equivalent mixing of steel fibers in reactive powder concrete.

[0086] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can, without departing from the scope of the technical solution of the present invention, make many possible changes and modifications to the technical solution of the present invention using the technical content disclosed above, or modify it into an equivalent embodiment with equivalent changes. Therefore, any simple modification, equivalent change, and modification made to the above embodiment in accordance with the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for analyzing and evaluating the equivalent mixing of steel fibers in reactive powder concrete, comprising a baseline group and an experimental group, wherein the reactive powder concrete in the baseline group uses a certain straight steel fiber as a baseline toughening steel fiber, and the reactive powder concrete in the experimental group uses the baseline toughening steel fiber mixed with 1-n types of straight or wavy additional steel fibers, characterized in that: The steel fiber equivalent mixing analysis and evaluation method of the experimental group is as follows: If the experimental group of active powder concrete is mixed with multiple steel fibers of the same type but different specifications, only when When the steel fiber admixture in reactive powder concrete is equivalent to that in the mixed concrete, If the experimental group of active powder concrete is mixed with a variety of steel fibers of different types and specifications, only those that meet When the steel fiber admixture in reactive powder concrete is equivalent to that in the mixed concrete, Where: ω0: the volume content of the benchmark toughening steel fiber in the benchmark reactive powder concrete, unit: kg / m 3 ; d0: the average diameter of the benchmark toughening steel fibers in the benchmark reactive powder concrete, in mm; η0: Bond coefficient of the benchmark toughened steel fiber in the benchmark reactive powder concrete, unit N / mm 2 ; ω1, ω2......ω n : are the volumetric dosages of the benchmark toughening steel fiber and various additional steel fibers in the experimental group, in kg / m 3 ; d1, d2......d n : are the diameters of the baseline toughening steel fibers and various additional steel fibers in the experimental group, in mm; η1, η2......η n : are the bonding coefficients of the benchmark toughened steel fibers and various additional steel fibers in the experimental group, in N / mm 2 .

2. The steel fiber equivalent mixing analysis and evaluation method for reactive powder concrete according to claim 1, characterized in that: The bonding coefficient is in direct proportion to the product of the steel fiber anchoring factor, the material friction factor and the dispersion contribution factor.

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