CN114953105A - Non-rib high-doping-amount steel fiber concrete segment and manufacturing method thereof - Google Patents
Non-rib high-doping-amount steel fiber concrete segment and manufacturing method thereof Download PDFInfo
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- CN114953105A CN114953105A CN202210743209.1A CN202210743209A CN114953105A CN 114953105 A CN114953105 A CN 114953105A CN 202210743209 A CN202210743209 A CN 202210743209A CN 114953105 A CN114953105 A CN 114953105A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B28—WORKING CEMENT, CLAY, OR STONE
- B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
- B28B1/00—Producing shaped prefabricated articles from the material
- B28B1/52—Producing shaped prefabricated articles from the material specially adapted for producing articles from mixtures containing fibres, e.g. asbestos cement
- B28B1/523—Producing shaped prefabricated articles from the material specially adapted for producing articles from mixtures containing fibres, e.g. asbestos cement containing metal fibres
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B28—WORKING CEMENT, CLAY, OR STONE
- B28C—PREPARING CLAY; PRODUCING MIXTURES CONTAINING CLAY OR CEMENTITIOUS MATERIAL, e.g. PLASTER
- B28C5/00—Apparatus or methods for producing mixtures of cement with other substances, e.g. slurries, mortars, porous or fibrous compositions
- B28C5/003—Methods for mixing
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/91—Use of waste materials as fillers for mortars or concrete
Abstract
The invention discloses a non-reinforced high-doping-amount steel fiber concrete duct piece and a manufacturing method thereof. The non-rib high-doping-amount steel fiber concrete segment manufactured by the method can greatly reduce the segment damage and the segment micro-crack quantity, and has good tensile and anti-cracking properties.
Description
Technical Field
The invention belongs to the technical field of tunnel engineering, and relates to a non-reinforced high-doping-amount steel fiber concrete segment suitable for a shield or TBM tunnel and a manufacturing method thereof.
Background
The shield (or TBM) tunnel lining mostly adopts common reinforced concrete segments, the reinforced concrete segments have reliable mechanical strength, good corrosion resistance and mature construction and manufacturing technology, but the problems of large steel consumption, low production efficiency, easy occurrence of brittle failure, high local damage rate and the like are exposed in the continuous use process. And steel fibers are doped into the reinforced concrete, so that the tensile property of the segment can be obviously improved, the toughness of the reinforced concrete is enhanced, and a plurality of problems of the common shield segment are solved.
The application of the steel fiber pipe piece can be divided into two types: the first kind is steel bar-steel fiber concrete pipe piece with steel fiber and steel bar combination stressed together; and in the second category, the non-reinforced steel fiber concrete pipe piece which uses steel fibers to completely replace stressed steel bars. When the geological condition of the stratum where the tunnel is located is good, the surrounding rock is stable, and the water and soil pressure is low, the internal force of the segment structure is relatively low, such as a composite shield tunnel and a TBM tunnel built in a hard rock stratum. In this case, a second type of non-reinforced fiber reinforced concrete segment may be used. The non-reinforced steel fiber concrete segment not only can make up the problem of insufficient crack resistance of a common segment, but also can completely save the complex processes of manufacturing and installing a reinforcement cage, greatly reduces the steel consumption while simplifying the preparation process, and is the main direction for applying the steel fiber concrete segment.
However, because the non-reinforced steel fiber concrete segment is not provided with stressed steel bars, in order to ensure that the non-reinforced steel fiber concrete segment has reliable bearing capacity, the steel fiber concrete needs to have higher post-crack strength, and the post-crack strength is stable and reliable, so the steel fiber mixing amount of the non-reinforced steel fiber concrete segment is always up to 40kg/m 3 ～55kg/m 3 High content of steel fibresThe problems of poor workability of concrete, uneven dispersion of steel fibers and the like are caused, the quality of the large-scale production of the duct piece is seriously influenced, and the method specifically comprises the following steps:
(1) after the steel fiber is doped into the concrete mixture, the steel fiber can play a role of supporting a framework in the mixture, increase the internal friction resistance of the mixture and prevent the mixture from flowing; meanwhile, with the increase of the mixing amount, the steel fiber has larger specific surface area, so that the slurry cannot well fill the aggregate gaps and wrap the surfaces of the aggregates and the fibers, and the workability of the mixture is obviously deteriorated.
(2) The steel fiber is made by cutting the base steel wire, and both ends of the steel fiber are provided with the turning end hooks, so that the finished product is often in a state of being extremely scattered and fluffy, and the gaps among the fibers are large, and the hooking degree is high. If the fiber is directly transported to a production site, the fiber mixed into the concrete is hooked into a cluster and cannot be effectively dispersed.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, and provides a non-bar high-doping-amount steel fiber concrete segment and a preparation method thereof, so that the problem of poor workability of concrete is solved, the number of damaged segments and micro-cracks is greatly reduced, the non-bar high-doping-amount steel fiber concrete segment with good tensile and cracking performance is prepared, and the requirements of a shield or TBM tunnel are met.
Firstly, the invention provides a new steel fiber concrete mix proportion design method-a specific surface area substitution method, and establishes a direct relation between the steel fiber mixing amount and the use amounts of a cementing material and coarse and fine aggregates. The method can ensure the thickness of the mortar among the coarse aggregates and reduce the skeleton effect and the internal friction force of the steel fibers after the steel fibers are added, thereby ensuring the workability to meet the requirements of construction such as on-site stirring, pouring, vibrating and the like.
The invention provides a method for manufacturing a non-reinforced high-doping-amount steel fiber concrete segment, which comprises the following steps of:
s1, determining steel fiber concrete ingredients; the method comprises the following steps:
s11, determining the basic mixing proportion of cement, fly ash, sand, gravel, water and a water reducing agent in concrete ingredients according to the designed compressive strength of the duct piece;
s12, regarding the steel fibers as coarse aggregates, and based on the principle that the surface area of the coarse aggregates is not changed, partially replacing the steel fibers and the coarse aggregates in the concrete according to a set steel fiber doping proportion to obtain an initial steel fiber concrete ingredient;
s13, determining the mass difference of each cubic meter of concrete ingredients before and after steel fiber replacement;
s14, determining the adjustment mass of each cubic meter of steel fiber concrete ingredient according to the mass difference obtained in the step S13 to obtain the final steel fiber concrete ingredient;
s2, manufacturing a steel fiber concrete open beam according to the steel fiber concrete ingredient obtained in the step S1, and performing a three-point bending test to judge whether the steel fiber concrete meets the mechanical property requirement; if the mechanical property requirement is met, the step S3 is entered, otherwise, the step S1 is returned;
and S3, manufacturing the unreinforced steel fiber concrete segment according to the steel fiber concrete ingredients obtained in the step S1.
The purpose of the step S1 is to determine the steel fiber concrete mix, which contains high-content steel fibers, and also takes into account the surface area of the coarse aggregate, and by adjusting the mix, the filling gap is reduced as much as possible, and key parameters such as water-cement ratio and sand ratio are ensured.
In step S11, the basic mix proportion (i.e., concrete mix) of cement, fly ash, sand, gravel, water, and water-reducing agent in the concrete is obtained according to the designed compressive strength of the duct piece by a conventional method, which is referred to herein as the weight ratio. For example, the basic mix proportion of concrete is determined according to the design rule of common concrete mix proportion (JGJ55), and specifically comprises the following steps: cement 377kg/m 3 77kg/m of fly ash 3 592kg/m of sand 3 1203kg/m of stones 3 143kg/m of water 3 And the water reducing agent is 7.20kg/m 3 . Here, stone is used as a coarse aggregate.
In step S12, i.e. according to S sf ＝S z Replacing the steel fibers and the stones S sf Denotes the total surface area, S, of the steel fibres to be replaced sf ＝m sf *s sf ，s sf Defined as the total surface area per unit mass of steel fibres, in cm 2 /g，m sf Representing the quality of the steel fiber to be replaced; s sf Representing the total surface area of the stones to be replaced per cubic meter of concrete, S z ＝△m z *s z ，s z Is defined as the total surface area of the stone per unit mass, in cm 2 /g，△m z Representing the mass of the replaced stone.
The proportion of the steel fiber replacing the pebble can be determined according to the ratio of the specific surface areas of the steel fiber and the pebble, thereby defining the steel fiber replacement ratio
Then the process of the first step is carried out,
in the formula, m z1 The amount of stones per cubic meter of concrete before replacement; m is z2 The amount of stones per cubic meter of concrete after replacement; m is sf The mixing amount of the concrete steel fiber is per cubic meter.
From this, the initial steel fibre concrete mix, i.e. the mix proportion of cement, fly ash, sand, pebbles, water reducing agent and steel fibres, can be determined.
In step S13, after the stones are replaced with the steel fibers, the volume and the total mass of the concrete are reduced, and the concrete needs to be added to keep the volume unchanged; the total mass of the concrete ingredients to be added in each cubic meter of the steel fiber concrete after the replacement of the steel fibers is calculated according to the following formula:
wherein: v 1 Expressed in unit volume, 1m 3 ；m 1 The total mass of the concrete ingredient per cubic meter before the steel fiber replacement; m is 2 The total mass of the steel fibre concrete mix (containing steel fibres) per cubic metre after replacement of the steel fibres,
in step S14, according to the mass difference of each cubic meter of concrete burden before and after the steel fiber replacement, the total mass of each cubic meter of concrete is adjusted and added to each component according to the principle that the proportion of each component is not changed, and the formula is:
wherein: m is i1 And m i2 The mass of each component (except for stones and steel fibers) of each cubic meter of concrete before and after adjustment; m is z The component quality of the adjusted stones is shown.
The doping amount of the steel fiber per cubic meter is 40-55kg/m 3 Through the steps S11-S14, the proportion of the steel fiber concrete is determined as follows: 40-55kg/m steel fiber 3 Cement 400-409kg/m 3 82-83kg/m of fly ash 3 628-642kg/m sand 3 Stone 1117-containing material 1084kg/m 3 152% of water and 155kg/m 3 And water reducing agent 7.64-7.81kg/m 3 。
The steel fiber concrete can ensure that the material used by the duct piece has better mechanical property after cracking only by meeting certain mechanical property, and is used for preparing the non-reinforced duct piece. Therefore, the invention further provides a method for testing the mechanical properties of the steel fiber concrete (i.e., step S2), which comprises the steps of determining the strength of the steel fiber concrete at each stage under the action of an external load through an open beam bending test of the steel fiber concrete, and determining whether the mechanical properties of the steel fiber concrete meet the preparation requirements for the non-reinforced pipe sheet through the strength ratio.
The step S2 includes the following sub-steps:
s21, preparing steel fiber concrete;
s22, manufacturing a steel fiber concrete open beam;
s23, carrying out three-point bending test on the steel fiber concrete open beam to obtain the maximum strength (namely proportional ultimate strength) f in the elastic range of the open beam Lop First residual strength f corresponding to 0.5mm of opening displacement after opening beam cracking R1 Second residual strength f corresponding to 2.5mm of opening displacement R3 ；
S24, judging whether the steel fiber concrete meets the following mechanical property requirements, if so, entering the step 3, otherwise, returning to the step S1:
(1)f R1 /f Lop ≥1.0；
(2)f R3 /f R1 ≥1.0。
the step S21 includes the following sub-steps:
s211, preparing materials according to the steel fiber concrete, measuring sand and stones, putting the sand and the stones into a conveying belt, and conveying the sand and the stones to a stirring device;
s212, steel fibers are weighed according to the steel fiber concrete ingredients, and the steel fibers and sand and stones on the conveying belt are simultaneously added into the stirring device through the vibration feeder;
s213, dry-mixing the steel fibers, the sand and the stones transported to the stirring device for at least 30 seconds, then sequentially adding the cement, the fly ash, the water and the water reducing agent, and continuously stirring for at least 90 seconds to obtain the steel fiber concrete.
In step S211, the sand used is clean medium sand, the fineness modulus is greater than 2.5, and the mud content is less than 3%. The used stones are mountain gravel with the maximum grain size not greater than 25mm, the grading is continuous, and the mud content is less than 1%.
In step S212, the steel fiber used should simultaneously satisfy the following requirements:
the method comprises the following steps that 1, the steel fibers are high-strength cold-drawing cut steel wire fibers, and the tensile strength of the steel fibers is not less than 1000 MPa;
condition 3, the relative length between the two ends of the steel fiber is 50-70mm, and the length-diameter ratio is 55-75;
and 4, producing and packaging the steel fibers by adopting a magnetization arrangement process.
In step S213, the total stirring time of the dry stirring time and the continuous stirring time is controlled to be 120-180 seconds.
The used cement is P.O 52.5 grade low alkali portland cement or low alkali ordinary portland cement (alkali content is less than or equal to 0.6%) whose quality conforms to GB175 specification, and the tricalcium aluminate content in the cement is controlled to be less than 8%. The fly ash is grade I fly ash which meets the GB1596 standard. The water reducing agent is low-chlorine low-alkali high-efficiency water reducing agent, such as polycarboxylic acid water reducing agent, melamine water reducing agent, etc.
In the step S22, the prepared steel fiber concrete is poured into a 150mm × 150mm × 550mm trabecula, and the side of the molded test piece is slit to form an open beam, wherein the slit has a depth of 25mm ± 1mm, a length of 150mm, and a width of 20-30 mm.
In the step S23, the maximum strength in the elastic range of the split beam is the maximum external load F in the section where the test curve is linear Lop The obtained intensity; the residual strength of the cracked open beam is that the open displacement in a test curve is 0.5mm and the external load F corresponding to 2.5mm 0.5 And F 2.5 The strength obtained can be calculated according to the following formula according to the corresponding test external load:
wherein L represents the span between two supports under the open beam in the three-point bending test, b represents the height of the cross section of the open beam, and h sp Indicating the height of the crack top to the top surface of the open beam after the open beam is cracked.
Finally, the invention also provides a step of manufacturing the duct piece by using the bar-free high-doping-amount steel fiber concrete meeting the mechanical property requirement, the prepared duct piece can improve the tensile and anti-cracking properties of the duct piece, reduce the steel consumption, simplify the preparation process, and also emphatically solve the problem that the steel fibers are not uniformly dispersed in the concrete in the preparation process of the high-doping-amount steel fiber concrete duct piece, and can be used for large-scale batch production of the duct piece.
The step S3 includes the following sub-steps:
s31, preparing steel fiber concrete;
s32, injecting the prepared steel fiber concrete into a duct piece mould, and opening a vibration table below the mould when discharging appears from a discharging opening to vibrate the steel fiber concrete in the mould until the steel fiber is uniformly dispersed in the concrete;
and after the S33 vibration is finished, the obtained steel fiber concrete pipe piece is subjected to the working procedures of surface plastering, steam curing, demoulding, secondary water curing and the like to obtain the reinforcement-free steel fiber concrete pipe piece.
The above step S31 is the same as the previous step S21 and will not be explained in detail here.
In the step S32, the duct piece mold feeding opening is located in the center of the molded duct piece arch, so that the steel fiber concrete flows naturally to both sides during feeding and vibration. The slump of the steel fiber concrete is measured to be between 70 and 90mm by sampling at a feed opening, and the fluidity is good. The vibration frequency is 12000-15000RPM, the vibration amplitude is below 2mm, and the vibration time is 120-150 seconds. And sampling in the mold after the vibration is finished, and measuring the dispersibility of the steel fiber concrete by adopting a water washing method.
In the step S33, the steel fiber concrete segment after vibrating still needs to undergo the processes of plastering, steam curing, demoulding, secondary water curing and the like, and the process is the same as that of a common concrete segment. And (5) after the demolded segment mold is cleaned, returning to the step S31 for continuous use.
The invention further provides the non-reinforced high-doping-amount steel fiber concrete pipe piece manufactured by the method.
Compared with the prior art, the manufacturing method of the non-reinforced high-doping-amount steel fiber concrete segment provided by the invention has the following beneficial effects:
(1) the non-rib high-doping-amount steel fiber concrete segment manufactured by the method can greatly reduce the segment damage and the segment micro-crack quantity, and has good tensile and anti-cracking properties.
(2) The reinforcement-free high-doping-amount steel fiber concrete pipe manufactured by the method has higher residual strength after cracking, is stable and reliable in a larger opening displacement range (0.5-2.5mm), and can be used for composite shield tunnels and TBM tunnels in hard rock strata.
(3) The reinforcement-free high-doping-amount steel fiber concrete segment manufactured by the method completely cancels the manufacturing and installation procedures of the reinforcement cage, simplifies the preparation process and reduces the consumption of steel.
(4) The method solves the problems of poor workability and uneven dispersion of steel fibers of high-content steel fiber concrete by adjusting the adding sequence of ingredients and combining with vibration operation, and is suitable for large-scale production of the duct piece.
Drawings
FIG. 1 is a schematic flow chart of a manufacturing method of the non-reinforced high-content steel fiber concrete segment of the present invention;
FIG. 2 is a schematic view of a process for determining the steel fiber concrete batching in the method for manufacturing the non-reinforced high-content steel fiber concrete segment of the present invention;
FIG. 3 is a schematic view of the mechanical property requirement judgment process in the method for manufacturing a non-reinforced high-content steel fiber concrete segment according to the present invention;
FIG. 4 is a schematic representation of a steel fiber shape;
FIG. 5 is a strength index obtained by a three-point bending test of a high-content steel fiber concrete open beam; wherein SF40 represents that the steel fiber content is 40kg/m 3 SF45 shows that the steel fiber content is 45kg/m 3 SF50 shows that the steel fiber content is 50kg/m 3 SF55 shows that the steel fiber content is 55kg/m 3 (ii) a The steel fiber content is 45kg/m 3 The method for manufacturing the high-content steel fiber concrete is shown in example 1, and the method for manufacturing the high-content steel fiber concrete with other steel fiber contents is similar to the method given in example 1, and only the corresponding high fiber contents are replaced.
Detailed Description
The technical solutions of the embodiments of the present invention are clearly and completely described below with reference to the accompanying drawings, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, belong to the present invention.
Example 1
The method for manufacturing the non-reinforced high-content steel fiber concrete segment, as shown in fig. 1 to 3, includes the following steps:
s1, determining steel fiber concrete ingredients; the method comprises the following steps:
s11, determining the basic mix proportion of cement, fly ash, sand, pebble, water and water reducer in the concrete ingredients according to the designed compressive strength of the duct piece.
In the step, the basic mix proportion of the concrete is determined according to the design compressive strength of the duct piece and the design rule of the mix proportion of the common concrete (JGJ55), and the concrete steps are as follows: cement 377kg/m 3 77kg/m of fly ash 3 592kg/m of sand 3 1203kg/m of stones 3 143kg/m of water 3 And the water reducing agent is 7.20kg/m 3 Total mass of 2399.2kg/m 3 . Here, stone is used as a coarse aggregate.
S12, regarding the steel fiber as coarse aggregate, and based on the principle that the surface area of the coarse aggregate is not changed, according to the set steel fiber doping proportion, carrying out partial replacement by using the steel fiber and the coarse aggregate in the concrete to obtain the initial steel fiber concrete ingredient.
In this step, i.e. according to S sf ＝S z Replacing the steel fibers and the stones S sf Denotes the total surface area, S, of the steel fibres to be replaced sf ＝m sf *s sf ，s sf Defined as the total surface area per unit mass of steel fibres, in cm 2 /g，m sf Representing the quality of the steel fiber to be replaced; s sf Representing the total surface area of the stones to be replaced per cubic meter of concrete, S z ＝△m z *s z ，s z Defined as the total surface area of the stone per unit mass, in cm 2 /g，△m z Representing the mass of the replaced stone.
In this example, the specific surface of the selected steel fibers and the aggregateThe product is respectively: s sf ＝6.79cm 3 G and s z ＝1.69cm 3 G, thereby defining the steel fiber replacement ratio
Then the process of the first step is carried out,
in the formula, m z1 The amount of stones per cubic meter of concrete before replacement; m is z2 The amount of stones per cubic meter of concrete after replacement; m is sf The mixing amount of the concrete steel fiber is per cubic meter.
From this, the initial steel fibre concrete mix, i.e. the mix ratio of cement, fly ash, sand, pebbles, water reducer and steel fibre, can be determined, i.e.: steel fiber 45kg/m 3 377kg/m of cement 3 77kg/m of fly ash 3 592kg/m of sand 3 1023kg/m stone 3 143kg/m of water 3 And the water reducing agent is 7.20kg/m 3 。
Thus, the total mass m per cubic meter of steel fibre concrete mix after replacement of the steel fibres 2 Comprises the following steps:
m 2 ＝2399.2-(4-1)×45＝2264.2kg/m 3 。
s13 determines the poor mass per cubic meter of concrete mix before and after the steel fiber replacement.
In step S13, after the stones are replaced with the steel fibers, the volume and the total mass of the concrete are reduced, and the concrete needs to be added to keep the volume unchanged; the total mass of the concrete ingredients to be added in each cubic meter of the steel fiber concrete after the replacement of the steel fibers is calculated according to the following formula:
wherein: v 1 Expressed in unit volume, 1m 3 ；m 1 For the total amount of concrete mix per cubic meter before replacement of steel fibresQuality; m is 2 The total mass of the steel fibre concrete mix (steel fibre contained) per cubic metre after replacement of the steel fibres.
S14, according to the mass difference obtained in the step S3, the adjustment mass of each cubic meter of the steel fiber concrete mixture is determined, and the final steel fiber concrete mixture is obtained.
In the step, according to the mass difference of concrete ingredients per cubic meter before and after the replacement of the steel fibers, the reduced total mass of the concrete per cubic meter is adjusted and added into each component according to the principle that the proportion of each component is not changed, and the formula is as follows:
wherein: m is i1 And m i2 The mass of each component (except for stones and steel fibers) of each cubic meter of concrete before and after adjustment; m is z The component quality of the adjusted stones is shown.
Therefore, the proportion of the final steel fiber concrete after the adjustment of each component is as follows: steel fiber 45kg/m 3 403kg/m of cement 3 82kg/m of fly ash 3 633kg/m of sand 3 1106kg/m of stones 3 153kg/m of water 3 And the water reducing agent is 7.70kg/m 3 。
S2, manufacturing a steel fiber concrete open beam according to the steel fiber concrete ingredient obtained in the step S1, and performing a three-point bending test to judge whether the steel fiber concrete meets the mechanical property requirement; and if the mechanical property requirement is met, the step S3 is carried out, otherwise, the step S1 is returned.
The method comprises the following steps:
s21 steel fiber concrete, comprising the following steps:
s211, proportioning the steel fiber concrete, measuring sand and stones, putting the sand and the stones into a conveying belt, and conveying the sand and the stones to a stirring device.
In the embodiment, the used sand is clean medium sand, the fineness modulus is more than 2.5, and the mud content is less than 3%. The used mountain gravel with the particle size of 5-25mm has continuous gradation and the mud content is 0.76 percent.
The stirring device here can be a conventional large stirring installation, for example a stirring tower.
S212, steel fibers are weighed according to the steel fiber concrete ingredients, and the steel fibers and the sand and the stones on the conveying belt are simultaneously added into the stirring device through the vibration feeder.
In this example, the steel fiber used was a high-strength cold-drawn cut steel fiber, and the tensile strength was 1500 Mpa. The shape of the steel fiber is shown in figure 4, the relative length between two ends is 50mm, the length-diameter ratio is 67, the middle part of the steel fiber is a straight section, and two ends of the steel fiber are folded to form a hook shape.
The steel fibers used in this example were produced and packaged using a conventional magnetization arrangement process.
S213, carrying out dry mixing on the steel fibers, the sand and the stones which are conveyed into the stirring device for 30 seconds, then sequentially adding the cement, the fly ash, the water and the water reducing agent, and continuously stirring for 90 seconds to obtain the steel fiber concrete.
The cement used in the present example is P.O 52.5 grade low alkali Portland cement with quality meeting GB175 specification. The fly ash is grade I fly ash which meets the GB1596 standard. The water reducing agent is a polycarboxylic acid water reducing agent, and the water reducing rate is 25%.
S22 manufacturing the steel fiber concrete open beam.
The prepared steel fiber concrete is poured into a trabecula with the thickness of 150mm multiplied by 550mm, and the side surface of a molding test piece is subjected to slotting treatment to prepare an open beam, wherein the slotting depth is 25mm, the length is 150mm, and the width is 20 mm.
S23, carrying out three-point bending test on the steel fiber concrete open beam to obtain the maximum strength (namely proportional ultimate strength) f in the elastic range of the open beam Lop First residual strength f corresponding to 0.5mm of opening displacement after opening beam cracking R1 Second residual strength f corresponding to 2.5mm of opening displacement R3 。
The test load-opening displacement relationship curve obtained in the three-point bending test is shown in fig. 5.
Maximum external load F in section with linear relation of maximum strength in elastic range of open beam to test curve Lop The strength thus obtained; the residual strength of the cracked open beam is that the open displacement in a test curve is 0.5mm and the external load F corresponding to 2.5mm 0.5 And F 2.5 The strength obtained can be calculated according to the following formula according to the corresponding test external load:
wherein L represents the span between two supports under the open beam in the three-point bending test, b represents the height of the cross section of the open beam, and h sp Indicating the height of the crack top to the top surface of the open beam after the open beam is cracked.
In this example, when the doping amount of the steel fiber is 45kg/m 3 When f is present Lop ＝5.66Mpa、f R1 ＝6.03Mpa、f R3 ＝6.53Mpa。
S24, judging whether the steel fiber concrete meets the following mechanical property requirements, if so, entering the step 3, otherwise, returning to the step S1:
(1)f R1 /f Lop ＝1.07>1.0, namely the strength of the steel fiber concrete after cracking is greater than the peak value of the linear strength before cracking;
(2)f R3 /f R1 ＝1.08>1.0, namely the residual strength of the steel fiber concrete with the opening displacement of 2.5mm is larger than that of the steel fiber concrete with the opening displacement of 0.5mm, and the post-crack strength is stable.
The steel fiber concrete can be used for manufacturing the non-reinforced duct piece.
And S3, manufacturing the non-reinforced steel fiber concrete pipe piece according to the steel fiber concrete ingredients obtained in the step S1.
In the embodiment, the steel fiber concrete prepared by the mixing proportion is adopted to carry out mass production of the non-reinforced steel fiber concrete segment, and the non-reinforced high-doping-amount steel fiber concrete segment 187 ring is produced for the TBM interval of a certain subway (the steel fiber concrete segment is used)Fibre concrete 1506m 3 )。
The method comprises the following steps:
s31 steel fiber concrete, comprising the following steps:
this step is the same as the previous step S21 and will not be explained in detail here.
S32, injecting the prepared steel fiber concrete into the segment mould, and opening a vibration table below the mould to vibrate the steel fiber concrete in the mould when discharging from a discharging opening.
In this embodiment, the steel fiber concrete that will stir the completion pours into special section of jurisdiction mould into with the mode of layering unloading into, opens the shaking table after the unloading. The duct piece die feed opening is positioned in the center of the molding duct piece arch back, so that the steel fiber concrete naturally flows to two sides in the process of feeding and vibration.
The slump of the steel fiber concrete is measured to be between 70 and 90mm by sampling at a feed opening, and the fluidity is good. The vibration adopts high-frequency low-amplitude vibration, the vibration frequency is 14500RPM, the vibration amplitude is below 2mm, and the vibration time is 120 seconds. Sampling in the mould after the vibration is finished, measuring the dispersibility of the steel fiber concrete by adopting a water washing method, and displaying that the steel fiber content of all samples is 42-46kg/m 3 The dispersibility was good.
And after the S33 vibration is finished, the obtained steel fiber concrete pipe piece is subjected to the working procedures of surface plastering, steam curing, demoulding, secondary water curing and the like to obtain the reinforcement-free steel fiber concrete pipe piece.
In this embodiment, the steel fiber concrete segment after vibrating still needs to undergo the processes of plastering, steam curing, demolding, secondary water curing and the like, and the process is the same as that of a common concrete segment. And (5) after the demolded segment mold is cleaned, returning to the step S31 for continuous use.
Comparative example
In order to prove that the quality and performance of the non-reinforced high-doping-amount steel fiber concrete segment are critical, the segments produced by different proportions and processes in the trial production are compared as follows:
(1) proportioning the components according to the embodiment of the invention (steel fiber 45 kg/m) 3 Cement 403kg/m 3 82kg/m of fly ash 3 633kg/m of sand 3 1106kg/m of stones 3 153kg/m of water 3 And the water reducing agent is 7.70kg/m 3 ) The slump of the blended high-dosage steel fiber concrete can be stabilized at 7-9cm, and the concrete has better workability.
The high-doped steel fiber concrete is calculated according to the assumed mass method in the existing standard steel fiber concrete (JG/T472) and comprises the following components: steel fiber 45kg/m 3 376kg/m of cement 3 77kg/m of fly ash 3 591kg/m of sand 3 1199kg/m of stones 3 143kg/m of water 3 7.18kg/m of water reducing agent 3 . Mixing according to the proportion, the slump is less than 5cm, and even the slump is 0.
(2) According to the preparation method of the duct piece, after the step S3 is completed, 3 samples of 150mm multiplied by 150mm are taken from the vault and two sides of the steel fiber concrete duct piece after vibration and are detected by a water washing method, and the error between the volume ratio of the steel fibers in 3 samples and the steel fiber mixing amount required by the mixing ratio does not exceed +/-5%.
It will be appreciated by those of ordinary skill in the art that the embodiments described herein are intended to assist the reader in understanding the principles of the invention and are to be construed as being without limitation to such specifically recited embodiments and examples. Those skilled in the art can make various other specific changes and combinations based on the teachings of the present invention without departing from the spirit of the invention, and these changes and combinations are within the scope of the invention.
Claims (10)
1. A manufacturing method of a non-reinforced high-content steel fiber concrete segment is characterized by comprising the following steps:
s1, determining steel fiber concrete ingredients; the method comprises the following steps:
s11, determining the basic mixing proportion of cement, fly ash, sand, gravel, water and a water reducing agent in concrete ingredients according to the designed compressive strength of the duct piece;
s12, regarding the steel fibers as coarse aggregates, and based on the principle that the surface area of the coarse aggregates is not changed, partially replacing the steel fibers and the coarse aggregates in the concrete according to a set steel fiber doping proportion to obtain an initial steel fiber concrete ingredient;
s13, determining the mass difference of each cubic meter of concrete ingredients before and after steel fiber replacement;
s14, determining the adjustment mass of each cubic meter of steel fiber concrete ingredient according to the mass difference obtained in the step S13 to obtain the final steel fiber concrete ingredient;
s2, manufacturing a steel fiber concrete open beam according to the steel fiber concrete ingredient obtained in the step S1, and performing a three-point bending test to judge whether the steel fiber concrete meets the mechanical property requirement; if the mechanical property requirement is met, the step S3 is entered, otherwise, the step S1 is returned;
and S3, manufacturing the non-reinforced steel fiber concrete pipe piece according to the steel fiber concrete ingredients obtained in the step S1.
2. The method for manufacturing the tendon-free high-content steel fiber concrete segment as claimed in claim 1, wherein in step S12, stone is used as coarse aggregate, and the aggregate is S sf ＝S z Replacing the steel fibers and the stones S sf Denotes the total surface area, S, of the steel fibres to be replaced sf ＝m sf *s sf ，s sf Defined as the total surface area per unit mass of steel fibres, in cm 2 /g，m sf Representing the quality of the steel fiber to be replaced; s sf Representing the total surface area of the stones to be replaced per cubic meter of concrete, S z ＝△m z *s z ，s z Defined as the total surface area of the stone per unit mass, in cm 2 /g，△m z Representing the mass of the replaced stone;
the proportion of the steel fiber replacing the pebble can be determined according to the ratio of the specific surface areas of the steel fiber and the pebble, thereby defining the steel fiber replacement ratio
Then the process of the first step is carried out,
in the formula, m z1 The amount of stones per cubic meter of concrete before replacement; m is z2 The amount of stones per cubic meter of concrete after replacement; m is a unit of sf The mixing amount of the concrete steel fiber is per cubic meter;
from this, the initial steel fibre concrete mix, i.e. the mix proportion of cement, fly ash, sand, pebbles, water reducing agent and steel fibres, can be determined.
3. The method for manufacturing the reinforcement-free high-content steel fiber concrete duct piece according to claim 1 or 2, wherein in the step S13, the mass difference of each cubic meter of concrete ingredients before and after the replacement of the steel fibers is calculated according to the following formula:
wherein: v 1 Expressed in unit volume, 1m 3 ；m 1 The total mass of the concrete ingredient per cubic meter before the steel fiber replacement; m is 2 The total mass of the steel fiber concrete ingredient per cubic meter after the replacement of the steel fiber,
4. the method for manufacturing the reinforcement-free high-content steel fiber concrete segment as claimed in claim 3, wherein in step S14, according to the mass difference of concrete ingredients per cubic meter before and after steel fiber replacement, the total mass of concrete reduced per cubic meter is adjusted and added to each component according to the principle that the proportion of each component is not changed, and the formula is as follows:
wherein: m is i1 And m i2 The mass of each component except stones and steel fibers of each cubic meter of concrete before and after adjustment; m is z The component quality of the adjusted stones is shown.
5. The method for manufacturing the reinforcement-free high-doping-amount steel fiber concrete duct piece according to claim 4, wherein the doping amount of the steel fibers per cubic meter is 40-55kg/m 3 Through the steps S11-S14, the proportion of the steel fiber concrete is determined as follows: 40-55kg/m steel fiber 3 Cement 400-409kg/m 3 82-83kg/m of fly ash 3 628-642kg/m sand 3 Stone 1117-containing material 1084kg/m 3 152% of water and 155kg/m 3 And water reducing agent 7.64-7.81kg/m 3 。
6. The method for manufacturing the tendon-free high-content steel fiber concrete duct piece according to claim 1, wherein the step S2 includes the following steps:
s21, preparing steel fiber concrete;
s22, manufacturing a steel fiber concrete open beam;
s23, carrying out three-point bending test on the steel fiber concrete open beam to obtain the maximum strength f in the elastic range of the open beam Lop First residual strength f corresponding to 0.5mm of opening displacement after opening beam cracking R1 Second residual strength f corresponding to 2.5mm of opening displacement R3 ；
S24, judging whether the steel fiber concrete meets the following mechanical property requirements, if so, entering the step 3, otherwise, returning to the step S1:
(1)f R1 /f Lop ≥1.0；
(2)f R3 /f R1 ≥1.0。
7. the method for manufacturing the tendon-free high-content steel fiber concrete duct piece according to claim 6, wherein the step S21 includes the following steps:
s211, preparing materials according to the steel fiber concrete, measuring sand and stones, putting the sand and the stones into a conveying belt, and conveying the sand and the stones to a stirring device;
s212, steel fibers are weighed according to the steel fiber concrete ingredients, and the steel fibers and sand and stones on the conveying belt are simultaneously added into the stirring device through the vibration feeder;
s213, dry-mixing the steel fibers, the sand and the stones transported to the stirring device for at least 30 seconds, then sequentially adding the cement, the fly ash, the water and the water reducing agent, and continuously stirring for at least 90 seconds to obtain the steel fiber concrete.
8. The method of claim 6, wherein in step S23, the maximum strength of the open beam in the elastic range is the maximum external load F in the section where the test curve is linear Lop The obtained intensity; the residual strength of the cracked open beam is that the open displacement in a test curve is 0.5mm and the external load F corresponding to 2.5mm 0.5 And F 2.5 The strength obtained can be calculated according to the following formula according to the corresponding test external load:
wherein L represents the span between two supports under the open beam in the three-point bending test, b represents the height of the cross section of the open beam, and h sp Indicating the height of the crack top to the top surface of the open beam after the open beam is cracked.
9. The method for manufacturing the tendon-free high-content steel fiber concrete duct piece according to claim 1, wherein the step S3 includes the following steps:
s31, preparing steel fiber concrete;
s32, injecting the prepared steel fiber concrete into a duct piece mould, and opening a vibration table below the mould when discharging appears from a discharging opening to vibrate the steel fiber concrete in the mould until the steel fiber is uniformly dispersed in the concrete;
and (S33) after the vibration is finished, the obtained steel fiber concrete segment is subjected to the working procedures of plastering, steam curing, demoulding and secondary water curing to obtain the reinforcement-free steel fiber concrete segment.
10. A non-reinforced high-content steel fiber concrete duct piece manufactured by the method of any one of claims 1 to 9.
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