CN115855624A - Full-scale test method for large-volume RPC reactive powder concrete - Google Patents

Abstract

The invention discloses a full-scale test method of large-volume RPC reactive powder concrete, which comprises the following steps: 1) Preparing and premixing RPC concrete raw materials; 2) Installing and debugging stirring equipment; 3) Installing a full-scale test block steel bar template; 4) RPC concrete production stirring; 5) RPC concrete pouring construction; 6) Dismantling the RPC concrete template and maintaining the RPC concrete template in a heat-preservation way; 7) And (5) carrying out a performance test experiment on the formed RPC concrete test block. The method provided by the invention creates a precedent of large-volume RPC application, solves the three problems of controlling the hydration heat release of the RPC, the shrinkage of the large-volume RPC and the regulation and control of the coagulation time of the RPC, successfully applies the method to the building construction of the cable-stayed bridge, lays a technical foundation for the use of RPC concrete in other construction projects in the future, and provides more possibilities and more diversified choices for the future building design.

Description

Full-scale test method for large-volume RPC reactive powder concrete

Technical Field

The invention relates to the technical field of concrete construction, in particular to a full-scale test method of large-volume RPC reactive powder concrete.

Background

Along with the requirement on the building of people is higher and higher, except that the functional requirement of the building itself is required to be satisfied, still need to combine original view demand, satisfy under the safe prerequisite of structure, make building structure's molding more do not have, realize building and all around environment's harmonious unity, this has proposed higher requirement with regard to the building, often need simple single structure to bear the high percentage load of building, the intensity of ordinary concrete can't satisfy the service standard of this kind of high requirement building, consequently need use the novel concrete that has high compressive strength and high tensile strength, in order to satisfy the service standard of modern building.

Reactive Powder Concrete (RPC) is a novel building material with excellent mechanical property and durability after high-strength and high-performance Concrete. It has been widely used in construction engineering, such as wet bridge joints, bridge deck pavement, bridge decks, prestressed box girders, bridge repair reinforcement, and the like. The application of RPC in the engineering structure can solve the defects of insufficient tensile strength, large brittleness, poor volume stability and the like of the existing high-strength and high-performance concrete, and can solve the problems of high investment, poor fireproof performance, easy corrosion and the like of a steel structure.

The RPC self-cementing material has very large dosage, so the self-shrinkage and hydration heat release of the RPC self-cementing material are far larger than those of common large-volume concrete, and the shrinkage stress and the temperature stress generated by the RPC self-cementing material can cause the cracking of the large-volume RPC. The large-size RPC has large pouring amount, the increase of hydration temperature rise can cause the shortening of the RPC condensation time, the construction cold joint is easy to generate in the pouring process, and the overall mechanical property of the prestressed RPC box girder is seriously influenced. The large-volume RPC has long pouring time, and has extremely high requirements on the initial fluidity and the working performance loss of the RPC, no additive capable of keeping the workability of the RPC for more than 3h is found in the current market, and the RPC is required to be realized without the fluidity loss for 3-4h through the additive technology. At present, no large-volume RPC application precedent exists at home and abroad, and the key points are three problems of controlling the hydration heat release of the RPC, the shrinkage of the large-volume RPC and the regulation and control of the coagulation time of the RPC.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a full-scale test method of the large-volume RPC reactive powder concrete, which is used for simulating each link of the large-volume RPC pouring through a full-scale test, determining control parameters of each link and laying a foundation for the later actual RPC pouring.

In order to achieve the purpose, the invention is realized by the following technical scheme: a full-scale test method of large-volume RPC reactive powder concrete comprises the following steps:

(1) Preparing and premixing RPC concrete raw materials;

(2) Installing and debugging stirring equipment;

(3) Mounting a full-scale test block steel bar template;

(4) RPC concrete production stirring;

(5) RPC concrete pouring construction;

(6) Dismantling the RPC concrete template and maintaining the RPC concrete template in a heat preservation way;

(7) And (4) carrying out a performance test experiment on the molded RPC concrete test block.

In order to better implement the method of the invention, further, in the step (1), the raw materials of the RPC concrete premix comprise cement, fly ash microbeads, granulated blast furnace slag powder, silica fume and fine aggregate.

In order to better implement the method of the present invention, further, in the step (2), the stirring devices installed and adapted are at least two vertical shaft planetary stirrers.

In order to better implement the method of the present invention, further, in step (3), the specific step of installing the full-scale test block steel bar formwork includes:

(3.1) determining a pouring forming scheme of the finally formed RPC concrete test block;

(3.2) cleaning the site, and performing measurement lofting;

(3.3) erecting a supporting template;

(3.4) arrangement of cooling water pipes;

(3.5) arranging temperature monitoring equipment and a strain monitoring instrument in advance to prepare for later-stage water temperature rise and structural deformation detection of the test block;

and (3.6) installing the steel bundle sleeve and the steel bar binding.

In order to better implement the method of the present invention, further, in the step (3.1), the casting scheme for determining the final molded RPC concrete comprises two types:

(3.1.1) setting a post-pouring strip, arranging a post-pouring strip between a tower beam consolidation section and a lower tower column, separating the tower beam consolidation section from the lower tower column without breaking a reinforcing steel bar, and after the tower beam consolidation section is poured, pouring the post-pouring strip by grouting, wherein the volume of a test block is 4m multiplied by 4m and is used for verifying the hydration heat release, stress strain deformation, temperature rise rule, pouring process and C60 interface binding power of large-volume RPC concrete; the verified parameters comprise temperature rise and temperature drop curves, stress-strain distribution and rules, deformation, pouring efficiency and interface bonding force;

(3.1.2) a cross parting post-pouring scheme, namely dividing the tower beam consolidation section into four blocks, reserving cross seam post-pouring belts, and pouring the post-pouring belts after the four blocks are demoulded; the volume of the test block is 4m multiplied by 2m, and the test block is used for verifying the block pouring, post-pouring belt treatment and prestress influence, and verifying the RPC pouring speed and steel fiber distribution; the verified parameters comprise the interface bonding effect of the post-cast strip, the blocking pre-stress effect, the influence of the cold joint, and the temperature control effect compared with the flow rate and the pouring effect of the RPC under the high reinforcement condition.

In order to better implement the method of the present invention, further, in the step (3.3), the concrete process of erecting the supporting formwork is as follows:

(3.3.1) installing pressing strips on the outer side of the bottom of the template;

(3.3.2) fixing the foundation bolt or the expansion bolt;

(3.3.3) installing a vertical template;

(3.3.4) reinforcing the template;

(3.3.5) tensioning the counter-pulling screw rod;

and (3.3.6) carrying out template acceptance.

In order to better implement the method of the invention, further, in the step (3.4), the outside diameter of the cooling water pipe is 48.3mm, the wall thickness is 3.5mm, the bent pipe part of the cooling water pipe is pretreated by a cold bending process, the cooling water pipes are tightly connected by all-welded joints, and the suspended part of the cooling water pipe needs to be welded with vertical ribs for fixing.

In order to better implement the method of the invention, further, in the step (5), a large-volume RPC pumping and joint surface performance test, a large-volume RPC flow rate test, a large-volume RPC pouring whole-process drill, and a large-volume RPC temperature control and shrinkage control are required to be performed in the RPC concrete pouring construction process.

In order to better implement the method of the present invention, further, in the step (6), (6) the concrete processes of the RPC concrete form demolition and the heat preservation maintenance include: covering and curing the concrete surface by using a film after the concrete surface is completely subjected to slurry collection, dismantling the template after the curing is carried out until the strength of the concrete reaches 90%, paying attention to the fact that corner concrete cannot be knocked down in the template dismantling process, and timely treating the corner concrete with the same grade if a corner defect occurs; after pouring is finished, manual finishing and trowelling are carried out, a layer of plastic film and a layer of heat-preservation straw curtain quilt are immediately covered, and then the heat-preservation cotton quilt, the film and the rock wool quilt are sequentially covered so as to ensure the surface temperature and the humidity of the test concrete, and the rock wool quilt is increased or decreased according to the temperature measurement condition.

In order to better implement the method of the present invention, further, in the step (7), the performing a performance test experiment on the molded RPC concrete test block specifically includes: hydration temperature rise test, mechanical property test and volume stability test.

Compared with the prior art, the invention has the following advantages and beneficial effects:

the method provided by the invention creates a precedent for large-volume RPC application, solves three problems of controlling the hydration heat release of the RPC, the shrinkage of the large-volume RPC and the regulation and control of the RPC setting time, successfully applies the method to the building construction of the cable-stayed bridge, lays a technical foundation for the use of RPC concrete in other construction projects in the future, and provides more possibilities and more diversified choices for the future building design.

Drawings

Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:

FIG. 1 is a flow chart of the RPC concrete full scale test construction process of the invention;

FIG. 2 is a schematic view of the arrangement of the vertical surface of a cooling water pipe in the scheme of the base mortar post-cast strip of the invention;

FIG. 3 is a schematic plan view of a cooling water pipe arrangement according to the present invention of a slurry-sitting post-cast strip;

FIG. 4 is a schematic view of the arrangement of the elevation of the cooling water pipes in the cross-shaped parting post-casting scheme of the invention;

FIG. 5 is a schematic plan view of cooling water pipes in the cross-seam post-cast solution of the present invention;

FIG. 6 is a schematic view of the arrangement of temperature measuring points of a test block in the scheme of the slurry-sitting post-cast strip of the invention;

FIG. 7 is a schematic view of vertical arrangement of temperature measuring points of test blocks in a base stock post-cast strip scheme according to the invention;

FIG. 8 is a schematic view of the arrangement of the temperature measuring points of the test block in the cross parting post-casting scheme of the invention

FIG. 9 is a schematic view of vertical arrangement of temperature measuring points of a test block in the cross-shaped parting post-pouring scheme of the invention;

FIG. 10 is a schematic plan view of strain monitoring points of a test block in the slurry-setting post-cast strip solution of the invention;

FIG. 11 is a schematic view of the vertical arrangement of strain monitoring points of a test block in the slurry-sitting post-cast strip scheme of the invention;

FIG. 12 is a schematic plan view of strain monitoring points of a test block in a cross parting post-cast scheme according to the present invention;

FIG. 13 is a schematic view showing the vertical arrangement of strain monitoring points of a test block in the cross-shaped parting post-casting scheme of the invention;

FIG. 14 is a schematic diagram of the arrangement of RPC concrete steel beam sleeves in the invention;

FIG. 15 is a schematic diagram of the RPC concrete bond performance test of the present invention;

FIG. 16 is a schematic view of a full-scale flow rate test of the present invention;

FIG. 17 is a schematic view of a temperature-raising environment test in the present invention.

Detailed Description

The present invention will be described in further detail with reference to the following examples for the purpose of making clear the objects, process conditions and advantages of the present invention, but the embodiments of the present invention are not limited thereto, and various substitutions and modifications can be made according to the common technical knowledge and the conventional means in the art without departing from the technical idea of the present invention described above, and the specific examples described herein are only for explaining the present invention and are not intended to limit the present invention.

Example 1:

the embodiment provides a full-scale test method for large-volume RPC reactive powder concrete, which comprises the following specific steps:

(1) Preparing and premixing RPC concrete raw materials;

(2) Installing and debugging stirring equipment;

(3) Installing a full-scale test block steel bar template;

(4) RPC concrete production stirring;

(5) RPC concrete pouring construction;

(6) Dismantling the RPC concrete template and maintaining the RPC concrete template in a heat preservation way;

(7) And (5) carrying out a performance test experiment on the formed RPC concrete test block.

Example 2:

the embodiment provides an engineering example of a certain cable-stayed bridge to show the specific implementation process of the method, the bridge adopts single-width open-deck bridge arrangement, the width of the bridge deck of a standard section of a single-width main bridge is 68m, the width of the bridge deck at the widest position is 79m, the cable-stayed bridge with the width exceeding the widest bridge in the world is an Egypt ROD EL FARAG cable-stayed bridge, and the cable-stayed bridge with the widest bridge deck in the world is provided.

The conventional cable-stayed bridge generally adopts plane pylons such as an H-shaped tower, an A-shaped tower, a gem-shaped pylon and the like, the construction and the application of a plurality of conventional pylons are mature, and the conventional cable-stayed bridge is widely known by the public as the image of the cable-stayed bridge pylon. The bridge adopts an ultra-wide cable-stayed bridge, combines landscape requirements, innovatively provides the space four-side special-shaped pyramid-shaped tower column on the premise of meeting the structural safety, has an attractive shape, and is harmonious and uniform with a bridge deck and the surrounding environment. Although the constructable use range of the cable-stayed bridge tower is further expanded by the four-side space special-shaped tower column, the technical difficulty is high, the ultra-large transverse load of the structure caused by the ultra-wide bridge floor is mainly reflected, and meanwhile, the large bridge tower column bears 90% of the full bridge load by combining a structural design control target and a calculation analysis conclusion. The main bridge of the bridge adopts a main span 280m space double-cable-side single-tower cable-stayed bridge and a tower-beam consolidation system; the main bridge is spanned, and the span is arranged to be 50+75+280=455m.

The large-size RPC tower beam consolidation section outer contour of the bridge adopts a streamline flat integral box beam section form with a top plate and a bottom plate communicated with each other. The concrete girder of the tower beam consolidation section is provided with a cross beam and a longitudinal beam at the corresponding positions of the tops of four limbs of the lower tower column, and a plurality of closed solid frame structures are formed on the plane. The height of the tower beam consolidation section is 4m, the thickness of a top plate of a standard section is 50cm, the thickness of a bottom plate and an arc bottom plate is 50cm, and the thickness of a straight web plate is 80cm.

The core area of the tower beam consolidation section is made of RPC140 concrete, and the rest is made of C60 steel fiber concrete. The tower beam consolidation section is positioned between the upper tower column and the lower tower column and is directly connected with the lower tower column through steel bars, and the tower beam consolidation section is strongly restrained by the lower tower column.

In order to solve a plurality of technical problems of the bridge, the bridge uses a plurality of novel materials, for example, steel fiber concrete is adopted in the ultra-large volume concrete structures of an upper tower column and a lower tower column, so that the strength and the durability of the tower columns are enhanced; in order to ensure the structure safety and reduce the construction difficulty, the steel-concrete combined section and the tower beam consolidation area adopt RPC reactive powder concrete.

The tower beam consolidation section of the bridge project is large-volume RPC reactive powder concrete, the length-diameter ratio of steel fibers doped in the RPC reactive powder concrete is 60, and the doping amount of the steel fibers is 120kg/m & lt 3 > the materials, the additives, the mixing proportion, the pouring process and the like of the composite material are determined by special test research, and meanwhile, the complex large-volume RPC temperature crack control, the shrinkage control and the stirring, pumping and pouring process control are involved in the construction process.

The girder in the construction stage range of the bridge girder and tower girder consolidation section S1-1 adopts RPC140 active powder concrete, the total amount is 6558.3m3, and the construction method relates to the large-volume construction of RPC. First, RPC has a very high requirement for the stirring supply capacity because of its extremely low water-to-gel ratio, which results in much longer stirring times than ordinary concrete. Secondly, because the pouring amount is large, the number of the cavities in the body type is complex, the top of the cavity is a herringbone slope with the gradient of 1.5%, the reinforcing bars are dense, and the construction is carried out in summer. In addition, the height of the main tower on the bank side and the casting position is 22.6m from the ground, a pipeline needs to be arranged for RPC pumping, the horizontal pumping distance is estimated to be 30m, and the pumping height is about 25 m. The above factors also put extremely high requirements on the workability of RPC.

In order to ensure that the bridge engineering is smoothly carried out, simulation of each link of large-volume RPC pouring is carried out through a full-scale test, control parameters of each link are determined, and a foundation is laid for later-stage actual pouring. The main purposes are as follows:

(1) Verifying theoretical model and obtaining key parameters

Before the full-scale test, the temperature stress of a full-scale test block and a solid structure and the deformation and cracking of the whole structure are simulated, the deformation influence of a tower beam consolidation section on a lower tower column is simulated, and a simulation result is obtained. And then, verifying in a full-scale test, acquiring key parameters including parameters such as a temperature rise curve, a temperature peak value, temperature stress, volume deformation and the like through the full-scale test, correcting the model according to the actually acquired parameters, and simulating the structural deformation and cracking conditions of the solid structure in the pouring, curing and cooling processes by adopting the corrected model for formulating a more detailed pouring scheme and guiding actual pouring and curing.

(2) Drilling and pouring process

And (4) verifying the pouring process of the tower beam consolidation section through a full-scale test. The pouring process of the tower beam consolidation section is to adopt 6 3-square mixers to stir on site, and prepare 3 pumps with 72 meters for pumping. Therefore, based on the actual pouring condition of the tower beam consolidation section, in a full-scale test, two 3-square machines and 1 72-meter-day pump are arranged, and meanwhile, a corresponding tank truck is equipped to perform the drilling of the whole pouring process. The parameters in the pouring process which need to be acquired include: the actual discharge amount of the stirrer for one hour, the pumping amount of the day pump for one hour, and the pumping performance parameters (viscosity, working performance, setting time, flow rate and the like) of the RPC are used for correcting the pouring scheme of the tower beam consolidation section.

After the acceptance of the RPC full-scale test reinforcing steel bars and templates of the bridge is qualified, the premix is stirred in a production stirring area and is transported to a pouring operation area through a tank car;

the RPC full-scale test construction of the bridge. The concrete construction process is as follows:

(1) RPC premix storage

The cement, the fly ash micro-beads, the granulated blast furnace slag powder, the silica fume and the fine aggregate in the RPC concrete raw material are stirred in a processing field to form pre-condensed materials, and the pre-condensed materials are bagged and then stored in a stock ground 7 kilometers away from the project site together with the steel fibers and the special RPC additives.

(2) Installing and debugging the vertical shaft stirrer: according to the scheme, according to the supply of the RPC full-scale test, the construction quality problem of the RPC is considered, the quality of the bridge is guaranteed, the RPC is stirred and supplied on site, and 2 platforms of 3m are arranged ³ The requirements of field stirring equipment options, production capacity, occupied area and the like of the vertical shaft planetary stirrer are shown in the following table:

(3) Installation and acceptance of RPC full-scale test block steel bar templates: and (3) measuring and lofting the plane position of the full-scale test block, performing bar planting and chiseling treatment on the original concrete ground, binding steel bars, erecting templates and arranging cold water pipes after cleaning, and entering the next procedure after the steel bars, the templates, the cold water pipes and other experience folding grids.

(4) RPC concrete production stirring: and (3) after the raw materials required by the full-scale test are transferred to the side of the stirrer, finishing all preparation and debugging work, and carrying out RPC production stirring. The municipal watering cart water is purchased uniformly by using field water, river water is not adopted, the river water is verified at the early stage, and the RPC prepared by the river water has insufficient strength; the on-site stirring is the premixed RPC premix, and only water, additives and steel fibers need to be metered on site. The purchased stirring equipment can automatically measure water and additives, the steel fibers are fed according to the package, and the weight of each package of steel fibers is fixed.

(5) RPC concrete pouring construction: and after the RPC production is stirred, the mixture is loaded and transported to a pouring construction area by using a tank car, and is poured to a full-scale test block pouring area through a top pump.

(6) Dismantling the RPC concrete template: after pouring is finished, manual flattening and smoothing are carried out, a layer of plastic film and a layer of heat-preservation straw curtain quilt are immediately covered, then the heat-preservation cotton quilt, the film and the rock wool quilt are sequentially covered, so that the surface temperature and the humidity of the test concrete are ensured, the rock wool quilt is increased or decreased according to the temperature measurement condition, and the full-scale test block can be disassembled after the test block reaches the disassembling strength through inspection and detection.

(7) And (3) maintaining the RPC concrete: and (3) continuously curing the RPC concrete to the designed strength, strengthening monitoring in the process, and taking temperature control measures.

And in the preparation stage, the first-level control network is retested at the same level, and the control network is encrypted according to the construction precision requirement. And accurately measuring the position of the construction part according to the control point and the level point of the measurement result, and after the design is rechecked, guiding the subsequent construction.

Example 3:

in this embodiment, for the construction of the cable-stayed bridge, a specific procedure of RPC full-scale test construction is performed after an experimental scheme is determined, as shown in fig. 1, specifically as follows:

1. construction preparation, measurement and lofting

All articles and sundries on the site are cleaned, the site is leveled, and the construction materials which are sanitary, clean, civilized and orderly and are not suitable for being carried away are required to be stacked orderly and the machines and tools are parked orderly.

After the on-site cleaning is finished, the on-site construction of the measuring team is used for lofting, the laid conducting wire points are rechecked before lofting, and lofting can be carried out only after rechecking is correct, so that quality accidents caused by lofting errors are avoided.

2. Formwork support

Form panel setting up:

setting up a flow: measuring lofting → installing side strips outside the bottom of the template → fixing anchor bolts (or expansion bolts → installing vertical templates → reinforcing the template → tightening the split screw → checking and accepting the template

And after the template is installed, reinforcing and correcting the template according to the designed elevation and size, carrying out self-checking after the template is corrected, and applying each party to check and accept after the self-checking is qualified. The template setup takes care of the following:

(1) The counter-pulling screw rods are arranged according to the figure, the longitudinal and transverse spacing is 800mm, the screw rod layer spacing is 800mm, after the template is fixed by the narrow side of the wood purlin, the double-row steel pipes are tightly attached to the other narrow side of the wood purlin, the double-row steel pipes are buckled back by the counter-pulling screw rod butterfly buckle, the nuts are tightened, and the outer sides of the template are connected and fastened by fasteners at the mutual connection positions in four directions of the reinforcing steel pipes;

(2) The layering uses a 10cm wide and 15mm thick wood template, the layering is fixed after the measurement and lofting, and then a vertical template is set up;

(3) The foundation bolts can be fixed by adopting 1m steel bars for bar planting or expansion bolts;

(4) Internal connection of opposite-pulling screw rod adopts

Welding the two sides of the steel bars, wherein the lapping length of the steel bars is 30cm;

(5) The template needs to adopt a brand new wood pattern, the abutted seam position is fixed by a small square bar with the width of 5cm, the splicing is tight, and the bottom of the template is filled and compacted by mortar;

(6) A release agent is uniformly coated on the inner side of the front template for pouring concrete, so that smooth template removal is ensured and the appearance quality of the concrete is ensured;

(7) The steel pipe has no cracks and depressions, and the steel pipe cannot be welded in a butt joint mode; the steel pipe is straight, two end faces are smooth, and inclined openings, burrs and corrosion do not need to be avoided; the surface of the component is smooth, casting defects such as cracks, air holes, shrinkage porosity, sand holes and the like cannot be caused, and the sand sticking, the casting head residue, fash, burrs, oxide skin and the like are removed; the stamping part cannot have the defects of cracks, burrs, oxide scales and the like; the member should be subjected to rust prevention treatment of spraying or dip-coating of rust-proof paint, and the rust-proof layer should be uniform and should not have the defects of paint piling, iron exposure and the like.

(8) In order to prevent the template from floating upwards and expanding the template at the bottom, a 6m long steel pipe is adopted to press the top of a pressing bar at the bottom of the template, and after the joints of the four steel pipes are connected by fasteners, vertical ribs are planted on the original ground and are firmly welded with the bottommost steel pipe;

(9) Strictly forbidding personnel to step on the steel pipe to operate in the template building process, adopting a movable door type operating frame according to the field condition, and strictly forbidding the operating frame to be connected with the template; when the construction requirements cannot be met by the movable operating frame above a certain height, a lifter or an overhead working truck can be adopted.

3. Cooling water pipe arrangement

The cooling water pipe adopts a pipe with the diameter of 48.3mm multiplied by 3.5mm (the outer diameter is 48.3mm, the wall thickness is 3.5 mm), has good heat conduction performance and meets the requirements of 'welded steel pipes for low-pressure fluid transportation' (GB/T3091-2018). The bent pipe part is pretreated by a cold bending process, and the pipes are tightly connected by all-welded joints. The suspended part of the water pipe needs to be welded with vertical ribs to fix the water pipe.

3 water pumps with power more than or equal to 5kw are prepared, and at least 1 spare pump is reserved. The water segregator is used for intensively segregating each layer of water pipes, is provided with independent water valves and flow meters in corresponding quantity to control the cooling water flow of each layer of water pipe, and is provided with a certain quantity of reducing valves to control the later water supply rate. The water passing time and the water passing flow rate of the cooling pipe are determined by a hydration heat test and the field condition. Before concrete pouring, a pressurized water test which is not shorter than half an hour is carried out, whether the water flow is proper or not is checked, and the phenomena of water leakage and water blocking of the pipeline are found and repaired in time until the pipeline can work normally. Certain protective measures are taken for the welding position of the water pipe, concrete is prevented from directly falling onto the cooling water pipe in the construction process, and constructors are strictly prohibited to step on the water pipe. Deep river water is extracted as cooling water in the early stage, the water temperature is regulated and controlled by the water collecting tank according to the temperature monitoring result in the later stage, the water inlet temperature and the highest temperature inside the concrete are smaller than 20 ℃, and the water flowing requirement of the concrete is shown in the table 1.

TABLE one Large volume RPC Water cut-through requirement

After the water pipe stops cooling by circulating water and is maintained, residual water in the water pipe is pressed out by an air compressor and the cooling water pipe is dried, and then micro-expansion cement mortar with the same strength as the concrete is injected into the water pipe by a grouting machine so as to close the pipeline.

4. Hydration temperature rise and structural deformation monitoring

The temperature stress is one of the main reasons for causing the surface cracking of the mass concrete, the internal temperature strain development change of the concrete test block is monitored, and corresponding test data is obtained, so that the method is one of the main purposes of the mass concrete simulation test. According to the construction Standard of Mass concrete (GB 50496-2018), a 1/2 symmetrical region of a test block is selected as a temperature monitoring region, a temperature monitoring probe and a strain monitoring instrument are arranged along a corresponding point position, the temperature change and the deformation of the Mass RPC after the pouring is started are monitored in real time, and data are recorded in detail.

The temperature monitoring adopts an HNTT (intelligent wireless) bulk concrete temperature measuring instrument (intelligent wireless) temperature measuring system, and monitoring equipment is shown as table II

Temperature monitoring equipment meter

At each temperature measuring point, a phi 48 multiplied by 3.5 steel pipe (a horizontal steel pipe @2000 is adopted to connect vertical steel pipes into a frame body) is erected in advance, small iron sheets are welded on the steel pipes according to the vertical arrangement intervals of the temperature sensors, then the temperature sensors are firmly bound on the small iron sheets, and the leads of the sensors extend out of the surface of the test block by 0.5m along the vertical steel pipes.

End condition of temperature measurement

The temperature measurement can be stopped when the following conditions are met:

(1) monitoring the mold-entering temperature of RPC concrete, wherein each vehicle must be monitored;

(2) the temperature rise value of the RPC concrete casting body on the basis of the mold-entering temperature is less than 60 ℃;

(3) the lining temperature difference (equivalent temperature without RPC shrinkage) of the RPC concrete is less than 45 ℃, and the early warning temperature of the simulation test is set to be 25 ℃;

(4) the cooling rate of the RPC concrete casting is less than 3 ℃/d;

(5) the temperature difference between the surface of the RPC concrete casting body and the atmosphere is less than 25 ℃.

Taking 1/2 of the full-scale model test block as a concrete strain monitoring area, and burying a strain sensor in the concrete. The strain sensors used in this test were unidirectional strain gauges, each capable of measuring strain in only one direction.

The instrument is suitable for strain measurement and monitoring, stress detection and monitoring of various linear elastic solid materials, and the strain measurement range is 0 to +/-400000 mu.

5. Steel bundle sleeve installation

The prestressed steel bundle sleeve is a C115 plastic corrugated pipe, although the prestressed steel bundle is not involved in the full-scale test block, the position of the steel bundle sleeve needs to be reserved to ensure that the position accords with the actual structural condition, and the distribution diagram of the test sleeve is shown in FIG. 14.

6. Reinforcement installation

(1) Binding reinforcing steel bar

The stressed main bars with the diameter larger than or equal to 22mm are connected by straight thread sleeves, the joint connection grade is I grade, the joint rate in the connection section is not more than 50 percent, the standard requirement of technical specification for mechanical connection of steel bars (JGJ 107-2016) is met, and cold extrusion mechanical sleeve connection can be preferentially considered.

(2) Fabrication of steel bar

(1) The variety and specification of the steel bars entering the field must meet the design and specification requirements. And the steel plates are respectively stacked according to different steel grades, specifications, brands and manufacturers. The steel bars are stored in a mode of arranging the lower cover and the upper cover, so that the steel bars are prevented from being rusted due to moisture;

(2) before the steel bar is bent, oil stain, paint stain, floating skin, rust and the like on the surface of the steel bar are removed. The steel bar is straight without local bending;

(3) the bending of the reinforcing steel bars and the hooks at the tail ends are processed according to design requirements, and the following regulations are met when the design requirements are not met:

A. when a right-angle hook is adopted as a design requirement at the tail end of the pulled hot-rolled ribbed steel bar, the bending diameter d of the hook is not less than 5 times of the diameter of the steel bar, and a straight line section which is not less than 3 times of the diameter of the steel bar is reserved at the hook end;

B. in order to ensure the manufacturing precision of the steel bar, the steel bar die is manufactured according to the drawing size, and the finished steel bar can be put into use after being inspected on the die to be qualified. Several reinforcing steel bars are forbidden to be bent at the same time, so that the distortion is avoided;

C. and the box girder steel bars are formed on the steel bar binding pedestal. During the binding construction of the box girder reinforcing steel bars, the binding construction is carried out in the sequence from the outer side to the inner box side, from bottom to top, from stirrups to main reinforcements to chamfer reinforcing steel bars to tie bars;

D. considering that the steel bar framework is higher, a certain construction scaffold is arranged outside the fixed pedestrian passageway arranged at the periphery of the binding jig frame according to the requirement so as to facilitate the operation;

E. after the bottom plate steel bars are bound, a top plate steel bar support frame can be arranged, so that the steel bar framework is prevented from deforming under the action of gravity and vertical construction load;

F. and binding the crossed points of the steel bars by using iron wires, wherein the redundant parts of the binding wires are inwards bent and do not exceed the outer surface of the steel bar framework.

(3) Installation of reinforcing bars

And (4) after the reinforcing steel bars are processed and molded according to design drawings, the reinforcing steel bars are transported to the site through a flat car according to the construction sequence and the quantity of binding, and are hoisted to corresponding positions by adopting a tower crane. Before the steel bar is bound, the bottom die of the steel bar construction is firstly finished and is lofted, serial numbers are marked according to the design, then the steel bars are placed in sequence, and the main bars are bound by hanging wires, so that the main bars are ensured to be straight. After the bottom plate is bound, binding web steel bars, paying attention to the installation of the corrugated pipe in the installation process of the steel bars, and adopting effective measures to prevent the corrugated pipe from shifting; and (5) erecting the internal mold of the box girder and binding the steel bars of the top plate. The errors are controlled within the allowable range of the specification. All transverse bridge-direction reinforcing steel bars are arranged along the normal line of the center line of the box girder, and the vertical reinforcing steel bars are arranged vertically.

(4) Considerations for installing reinforcing bars

(1) The steel bar protection layer is supported between the steel bars and the template by adopting prefabricated concrete cushion blocks with equal strength to the main beam, and the thickness of the protection layer is required to meet the design requirement;

(2) in the process of installing the reinforcing steel bar, the reserved hole channel and the embedded part are arranged in time according to the design requirement, the position is correct, and the reserved hole channel and the embedded part are firmly fixed;

(3) the installation model and the plane position of the steel bars are arranged according to a design drawing, if a small amount of conflict exists between the common steel bars and a cooling water pipe, a prestressed steel bundle sleeve or an embedded monitoring component, the position of the common steel bars can be properly adjusted, but the number of the common steel bars cannot be reduced or the common steel bars cannot be cut off; when the steel bars are welded, the steel strands and the metal corrugated pipeline are prevented from being burnt by electric welding, and the situation that the tensioning fracture and the pipeline are blocked by concrete so that grouting cannot be carried out is prevented;

(4) the manufacturing and binding of the reinforcing steel bars are strictly carried out according to the requirements of technical Specifications for highway bridge and culvert construction (JTG/T3650-2020). The technical standard of the connector of the steel bars is in accordance with the regulations of mechanical connection technical code of the steel bars (JGJ 107-2016) and the rolled straight thread steel bar connector (JTJ 63-2004).

7. Pouring of concrete

The test block is poured once, and the supervision engineer is applied for acceptance after the template and the steel bar are checked to be qualified, and the concrete can be poured after the supervision engineer approves the test block. Detection of pouring uniform and dense conditions for RPC: firstly, RPC working performance completely meets the requirement of self-compaction, secondly, the total pouring amount is calculated through the front and back pouring amount for checking, and thirdly, vibration work is done.

Using 2 stands of 3m ³ Pouring a full-scale test block by using a vertical shaft planetary stirrer, wherein the pouring is 3m ³ The vertical shaft planetary stirrer stirs according to the maximum volume of 83 percent, and the single stirring amount is 2.5m ³ The total amount of the full-length test block is 96.5m ³ The planned stirring volume is 110m, taking into account the loss of material during stirring and pumping ³ The stirring was carried out 44 times in total according to the amount of single stirring, and the concrete stirring schedule is shown in Table three.

TABLE TRI RPC stirring plan

Single feeding plus stirring time/min	Amount of single stirring/m 3	Number of times of stirring	Total stirring volume/m 3	Total stirring time/h
					12	2.5	44	110	4.4

The ultra-high performance concrete mixture with the RPC expansion degree of 700-900mm is preferably poured from one side of a template, and is not suitable for vibration molding after one-time pouring. For the mixture with the expansion degree of 500-700mm, step-type layered distribution is preferably adopted, the thickness of each layer is not more than 300mm, and the thickness is controlled by a level gauge; the pouring interval time between layers should be shortened as much as possible, and the vibration should be enhanced locally at the interface. For blends with a spread of less than 500mm, the formation should be carried out by vibration.

The RPC vibration should be selected according to the expansion degree, the vibration form should be flat plate vibrator, external mold vibrator and plug-in type vibrating rod (length is 4 m), and the vibration is ensured to be dense while avoiding segregation and layering. The adopted vibrating machinery and vibrating method should ensure that the fiber is uniformly distributed besides the compactness of the ultra-high performance concrete, and the fiber distribution meets the following regulations:

1 the displacement pitch of the surface vibrators is preferably not less than 100mm covering the vibrated section using a vibrator plate.

2, the arrangement distance of the attached vibrator is determined by tests according to the current situation of the structure and the performance of the vibrator.

3 the diameter of the vibrating rod of the plug-in vibrator is not too large, generally not more than 50mm, the displacement distance is not more than 1.5 times of the acting radius of the vibrator, the distance between the vibrating rod and the side mould is kept between 50mm and 100mm, and the depth of the vibrating rod inserted into the lower layer concrete is preferably between 50mm and 100mm.

4, the vibration test piece at each vibration point is not suitable to exceed 20s, and when the surface of the concrete mixture is subjected to slurry overflow, the concrete mixture is regarded as tamping.

The pouring vibration of the structural member should avoid the fibers from leaking out of the surface of the structural member, the sharp corners and edges of the template should be trimmed into fillets, and an attached vibrator can be adopted to carry out vibration outside the mold if necessary.

Concrete is vibrated by adopting an inserted vibrating spear, and the following points are noticed during vibration:

(1) When the inserted vibrating spear is used, the moving distance does not exceed 2 times of the action radius of the vibrator, the vibrating spear keeps a distance of 50-100 mm with the side die when vibrating, and the lower layer concrete is inserted into the vibrating spear by 50-100 mm; after each part is vibrated, the vibrating rod is lifted out slowly while vibrating, so that the vibrating rod is prevented from colliding with a template, a reinforcing steel bar and other embedded parts.

(2) For each vibration part, the vibration must be carried out until the concrete is compacted at that part. The dense mark is that the concrete stops sinking and no bubbles appear, and the surface is flat and is full of slurry.

After concrete pouring is finished, the surface of the concrete is trimmed and leveled in time, and after concrete is poured, the concrete is smeared for the second time and is polished.

8. Form removal and heat preservation maintenance

After the concrete surface is completely received, the thin film is used for covering and maintaining, the template can be dismantled when the concrete strength reaches 90% after maintenance, the corner concrete cannot be knocked down during the template dismantling process, and if the problem of corner failure occurs, the concrete with the same grade is used for processing in time.

(1) Thickness of thermal insulation layer

According to article c.0.1 of P31 according to the "large volume concrete construction standard" (GB 50496-2018):

in the formula: delta-the thickness (m) of the insulating layer on the concrete surface;

λ _i -selected thermal insulation coefficient (W/m. K)

Because the heat preservation adopts: 1 layer of straw curtain quilt, 1 layer of plastic film and 1 layer of rock wool quilt, and the heat conductivity coefficient is finally 0.03;

T _s -concrete surface temperature (° c);

T _q the average atmospheric temperature (DEG C) when the concrete reaches the highest temperature (3 d-5 d after pouring);

T _max highest temperature in the concrete casting (. Degree. C.)

Taking T when calculating _s -T _q ＝20、T _max -T _b ＝25；

λ ₀ The thermal conductivity of the RPC concrete is 2.29W/(m.K);

K _b the heat transfer coefficient is corrected to be 1.4 according to the actual condition of the heat insulation layer;

h is the actual thickness of the concrete structure, and 4m is taken;

then there are:

(2) Covering mode

After pouring is finished, manual finishing and trowelling are carried out, a layer of plastic film and a layer of heat-preservation straw curtain quilt are immediately covered, then the heat-preservation cotton quilt, the film and the rock wool quilt are sequentially covered, so that the surface temperature and the humidity of the test concrete are guaranteed, and the rock wool quilt is increased or decreased according to the temperature measurement condition.

Example 4:

on the basis of the above embodiments, the present embodiment provides a concrete test block pouring scheme for a full-scale test, which specifically includes the following steps:

a base slurry post-cast strip scheme: arranging a post-pouring belt between the tower beam consolidation section and the lower tower column, separating the tower beam consolidation section from the lower tower column without breaking steel bars, and grouting and pouring the post-pouring belt after the tower beam consolidation section is poured, wherein the volume of a test block is 4m multiplied by 4m and is used for verifying the hydration heat release, stress strain deformation, temperature rise rule, pouring process and C60 interface binding force of the large-volume RPC concrete; the verified parameters comprise temperature rise and temperature drop curves, stress-strain distribution and rule, deformation, pouring efficiency and interface bonding force.

The advantages are that: the tower beam consolidation section has good structural integrity, and four cross beams of the tower beam consolidation section are intact, so that the whole stress is favorably ensured.

The disadvantages are as follows: the post-cast strip mold process and the pouring process are complex, the free deformation of the tower beam consolidation section can generate horizontal shearing force on the connecting steel bars, and whether the steel bars are sheared or not is uncertain.

The tests to be carried out: calculating the free deformation of the tower beam consolidation section and the generated horizontal shear force; a specific formwork supporting process.

The arrangement of the cooling water pipes is shown in figure 2 and figure 3, 3 layers of cooling water pipes are arranged in the 4m multiplied by 4m solid section, the distance between the horizontal pipes of the water pipes is 100cm, the distance between the vertical pipes is 100cm, the distance between the first layer water pipe, the second layer water pipe and the third layer water pipe is 100cm, 200cm and 300cm away from the bottom surface of the solid section, and the distance between the water pipes and the side surface of the concrete is 100cm. A single pouring layer is provided with 1 set of water pipes, and each set of water pipe is provided with a water inlet and a water outlet. The water pipe position can be properly adjusted when the water pipe arrangement collides with the element stiff skeleton.

The temperature monitoring of the scheme is as follows:

the arrangement of the internal temperature measuring points is as follows:

11 temperature measuring points are arranged in a 1/2 symmetrical area of a 4m multiplied by 4m trial block, which is specifically shown in fig. 6 and fig. 7.

The strain monitoring of this scheme is as follows:

the strain gauge monitoring points are arranged in the interior, as shown in fig. 10 and fig. 11, in the figure, numbers in brackets represent the number of the strain gauge, two numbers in brackets represent the strain in the monitoring direction X, Y, and three numbers in brackets represent the strain in the monitoring direction X, Y, Z, wherein Z is in the thickness direction of a 4m test block.

15 strain monitoring points are arranged in a 1/2 symmetrical area of a 4m multiplied by 4m test block, and a plane layout diagram and a vertical layout diagram of each monitoring point are detailed. At each strain monitoring point, a phi 48 multiplied by 3.5 steel pipe (a frame body is formed by connecting vertical steel pipes by adopting a horizontal steel pipe @ 2000) is erected in advance, small iron sheets are welded on the steel pipes according to the vertical arrangement intervals of the strain sensors, then the strain sensors are firmly bound on the small iron sheets, and the leads of the sensors extend out of the surface of the test block by 0.5m along the vertical steel pipe.

Example 5:

on the basis of the above embodiments, the present embodiment provides another concrete test block pouring scheme for a full-scale test, which specifically includes the following steps:

the cross joint division post-pouring scheme comprises the following steps: and (3) dividing the tower beam consolidation section into four blocks, reserving the cross seam post-cast strip, and pouring the post-cast strip after the four blocks are demoulded.

The advantages are that: the construction operation is relatively simpler and the cold-shrink stress can be completely released.

The disadvantages are as follows: the integrity of the four cross beams is damaged, but the pre-stressed steel bars are used for controlling, and the bonding effect and the pre-stressed effect of the post-cast strip need to be verified.

The tests to be carried out: setting a post-cast strip shear groove, and verifying the binding force between RPC; verifying the binding power by adopting a steel plate shear nail form; and calculating the prestress applying effect after parting, and whether the whole stress of the structure can be guaranteed.

The specific experimental design of this protocol is as follows:

(1) a blocking scheme: dividing a test block of 4m (length) × 4m (width) × 2m (height) into 4 blocks according to a cross parting manner, wherein the size of each block is 1.5m × 1.5m × 2m, and a cross seam with the width of 1m is arranged in the middle of the four blocks;

(2) pouring mode: dividing the test block into 4 test blocks, wherein the test block 1 and the test block 2 adopt an integral one-step pouring mode without arranging a cooling water pipe; the test block 3 adopts an integral one-time pouring mode, but a cooling water pipe is arranged; the test block 4 is poured in two layers, the time interval between the two layers is more than 4 hours, so that a cold joint is formed, and the influence of the cold joint is verified;

(3) post-pouring belt interface treatment: a shear groove is arranged on the interface of the post-cast strip between the test block 1 and the test block 2; a steel plate shear nail is adopted between the test block 1 and the test block 3; a shear groove is also arranged between the test block 3 and the test block 4; roughening the test blocks 2 and 4; pouring micro-expansion RPC on the post-cast strip;

(4) and (3) prestress test: shear force grooves are arranged between the test block 1 and the test block 2, and between the test block 3 and the test block 4, so that the influence of the prestress can be compared, the prestress is arranged between the test block 1 and the test block 2, and the prestress is not arranged between the test block 3 and the test block 4.

The arrangement of the cooling water pipes is as shown in fig. 4 and fig. 5, 2 layers of cooling water pipes are arranged in the 4 mx 2m test block 3, the distance between the horizontal pipes of the water pipes is 50cm, the distance between the vertical pipes is 70cm, 60 cm and 70cm from top to bottom, and the distance between the first layer of water pipes and the second layer of water pipes is 70cm and 130cm from the bottom surface of the solid section respectively. The distance between the water pipe and the side face of the concrete is 50cm. A single pouring layer is provided with 1 set of water pipes, and each set of water pipe is provided with a water inlet and a water outlet. The water pipe position can be properly adjusted when the water pipe arrangement collides with the element stiff skeleton.

The temperature monitoring of the scheme is as follows:

the arrangement of the internal temperature measuring points is shown in figures 8 and 9.

The strain monitoring of this scheme is as follows:

the strain gauge monitoring points are arranged inside, and as shown in fig. 10 and fig. 11, 60 strain monitoring points are arranged in a 4m × 4m × 2m test block area. In the figure, the numbers in brackets represent the numbers of strain gauges, two numbers in brackets represent the strain in the direction of monitoring X, Y, and three numbers in brackets represent the strain in the direction of monitoring X, Y, Z, where Z is in the thickness direction of a 4m block.

Example 6:

based on the above embodiments, the present embodiment provides a specific test procedure of RPC concrete, which is specifically as follows:

the performance test of the bridge large-volume RPC140 comprises three aspects of mechanical property, volume stability and hydration temperature rise.

(1) Hydration temperature rise test

The full-scale test and the main structure are both large-volume RPC, the self-hydration heat release is high, and the subsequent mechanical property and the subsequent volume stability are both in a high-temperature environment generated by the self-hydration heat release, so the first step of the performance test of the RPC140 is mainly in the aspect of testing the hydration temperature rise. For hydration temperature rise test of a field full-scale test, enough temperature sensors are arranged in a full-scale test block, the heat preservation effect of a template is simultaneously well made, excessive internal and external temperature difference is prevented, the temperature change of the whole process from pouring to ambient temperature reduction of the full-scale test block is monitored, and a temperature change curve, a temperature peak and the time required for reaching the temperature peak in the whole process are collected.

(2) Mechanical Property test

The mechanical property tests included the compressive strength, tensile strength, elastic modulus of the RPC, and the bond strength between the RPC and C60 concrete. The testing environment aiming at the compressive strength, the tensile strength and the elastic modulus needs to be tested in a high-temperature environment, the hydration temperature rise generated in the early-stage simulation test can reach more than 100 ℃ due to the large heat release of the large-volume RPC hydration, and meanwhile, the whole temperature reduction process lasts for more than 15 days, so that the mechanical property is simulated and tested by maintaining in a steam curing environment at 80 ℃ for 15 days when the mechanical property is tested. Aiming at the bonding strength between the RPC and the C60 concrete, firstly, four surfaces of a field full-scale test block are processed in different modes (four modes of no processing, surface roughening, template internal wire scraping, pre-embedded stud embedding and the like) to observe the bonding property of the RPC and the C60 concrete, and secondly, a flat plate test is carried out in a laboratory to bond two kinds of concrete and test the bonding strength.

(3) Volume stability

For the volume stability of the large volume RPC, the test is divided into two parts. The first part is to test the shrinkage development of the RPC in a normal temperature environment, and the key point is to test the self-shrinkage between initial setting and final setting and the total shrinkage from final setting to a service stage to obtain the basic data of the RPC shrinkage. The second part is the volume stability under the high temperature environment of considering the self hydration heat release of large-volume RPC, and the deformation amount tested is not only the shrinkage deformation of the RPC material, but also the thermal expansion deformation of the RPC under the high temperature environment, and the specific volume stability parameter of the RPC in the actual environment is obtained through testing.

(1) Raw material and basic performance of RPC140 concrete

(1) Cement

Because the bridge project is located in metropolis, the performance index of the RPC material is higher than the requirement of the RPC material with the grade of 140, the bridge project is combined with a local urban material, and the Cheng P. O52.5R cement is adopted. All performance indexes of the cement meet the requirements of GB175 general Portland cement.

(2) Coal ash micro-bead

The high-quality fly ash micro-beads with low carbon, small water demand and high activity are selected, and the shape of the micro-beads is basically spherical particles under a microscope. All performance indexes of the fly ash micro-beads meet the requirements of GB/T1596 fly ash for cement and concrete and GB/T18736 mineral admixture for high-strength and high-performance concrete.

(3) Granulated blast furnace slag powder

From the viewpoint of reducing the shrinkage cracking of concrete, the specific surface area of the ground granulated blast furnace slag powder is not too large. In addition, the Chongqing city has mineral powder with excellent performance, and is beneficial to the local production of the RPC in the project. All performance indexes of the granulated blast furnace slag powder meet the requirements of GB/T18046 granulated blast furnace slag powder used in cement, mortar and concrete and GB/T18736 mineral admixture for high-strength high-performance concrete.

(4) Silica fume

According to the closest packing principle of RPC, the particle size of silica fume should be controlled to about 1 μm, and it is easy to disperse during the mixing process. All performance indexes of the silica fume meet the requirements of GB/T27690 silica fume for mortar and concrete and GB/T18736 mineral admixture for high-strength and high-performance concrete.

(5) Fine aggregate

The fine aggregate should be classified reasonably, uniform and firm, low in water absorption, small in void ratio, and the content of particles with nominal particle size larger than 5mm in sand and sand in classification II zone should be less than 1%, and the inactive clean natural river sand or machine-made sand produced by special machine set is qualified after base material inspection, and sea sand should not be used. All performance indexes of the fine aggregate meet the requirements of GB/T31387 reactive powder concrete and GB/T14684 construction sand.

(6) Steel fiber

The steel fiber adopts high-strength microfiber, the type of the steel fiber is YB/T151 steel fiber for concrete, and all performance indexes of the steel fiber meet the requirements of GB/T31387 reactive powder concrete.

(7) Special RPC additive

The RPC special additive is colorless or light yellow liquid, the solid content is 40 percent, and the pH value is 6-7; the water reducing rate is more than 40 percent; the method is suitable for an RPC (reactive powder concrete) gelling system with the water-gel ratio of 0.12-0.2, and the concrete expansion range is 500-850 mm. All performance indexes meet the requirements of GB8076-2008 concrete admixture.

(8) Water for mixing

The mixing water meets the requirements of JGJ 63.

(2) Design principle of mix proportion

According to the engineering design parameters, the RPC characteristics and GB/T31387 reactive powder concrete, the design requirements on the RPC mix proportion are as follows:

(1) the prestressed RPC box Liang Tiji required to be poured in the project is large, the pouring time is long, the hydration heat release and shrinkage rate of cement need to be controlled, and the RPC setting time is prolonged;

(2) the prestressed RPC box Liang Peijin is very dense, and the RPC has very good working performance;

(3) the strength grade of the prestressed RPC box girder body is RPC140, and standard culture 28-day strength is adopted for evaluation;

(4) RPC mix proportion design adopts an absolute volume method and follows the closest packing theory;

(5) the formulated strength should be more than 10% surplus to the specified strength rating.

(6) Other unexhausted requirements are processed according to the requirements of 'design Specifications for durability of concrete structures of highway engineering' (JTG/T3310-2019) and 'design Specifications for bridges and culverts of reinforced concrete and prestressed concrete' (JTG 3362-2018);

(3) RPC140 mix proportion Performance requirements

1. Sampling of the RPC140 blend should meet the following specifications:

(1) the sampling in the RPC engineering construction should meet the relevant regulations of the national current standard of 'acceptance of construction quality of concrete Structure engineering' GB 50204, and should be extracted from 1/4 to 3/4 of the discharge capacity of the same transport vehicle or bucket at random.

(2) The sample of the RPC construction site mixture formed by pouring is taken out from the ultra-high performance concrete which is stirred at the same time or transported by the same vehicle, and the sampling amount is not less than 1.5 times of the required amount of the sample and is not less than 20L.

(3) The RPC mixture is randomly sampled and tested at a pouring site to determine whether the fibers are agglomerated and the fiber content, and the fiber content deviation should not exceed +/-5% of the fiber content designed by the mix proportion.

(4) RPC test items should include the extension and its loss over time, clotting time. The inspection method should meet relevant regulations of the national current standard GB/T50080 of the common concrete mixture performance test method standard, and if the working performance of the RPC mixture reaches the working performance of the self-compacting concrete, the inspection method should meet relevant regulations of the national current standard JGJ/T283 of the self-compacting concrete application technical regulation. The time loss of the expansion degree should be checked once in 24h, the condensation time should be checked three times, and the checking frequency should be increased if the temperature change is large. And the expansion degree or the slump should be respectively sampled and checked at the stirring place and the pouring place, and when the time from the discharge of the concrete mixture from the stirrer to the pouring of the concrete mixture into the mold is not more than 15min, the expansion degree can be only sampled and detected at the stirring place.

2. RPC140 post-hardening Performance test

(1) When the RPC test piece is manufactured, the mixture is loaded into a test die at one time and is slightly higher than the upper opening of the test die. The mixture is shaken on a shaking table for 30 seconds or continuously until the surface of the mixture is slurried, and excess mixture is scraped off and trowelled. The prism and the trabecular test piece are molded horizontally.

(2) The axial tensile strength test of the RPC test piece is carried out according to the relevant regulations of the national current standard 'ultra-high performance concrete basic performance and test method' T/CBMF37-2018/T/CCPA 7-2018; the test of the mechanical properties such as compressive strength, bending tensile strength, elastic modulus and the like is in accordance with the relevant regulations of the national current standard GB/T31387; the test values of the compressive strength and the bending tensile strength are not multiplied by a size conversion coefficient.

(3) The drying shrinkage and early-age self-shrinkage of RPC should be checked according to the relevant regulations in the State Current Standard GB/T50082 "Standard for testing Long-term Performance and durability of ordinary concrete".

(4) Construction requirements of concrete

(1) Before concrete construction, a construction unit formulates measures and implementation detailed rules for ensuring the construction quality of concrete according to the design requirement of the corrosion resistance and durability of a concrete structure, carefully selects raw materials, performs concrete trial, preferably selects the mixing proportion of the concrete on the basis of laboratory tests, and performs trial pouring on site;

(2) the construction quality control of the durable concrete has the key points that: the concrete has the advantages of uniform vibration and compactness, maintenance of concrete, thickness of a concrete protective layer of a reinforcing steel bar and concrete crack control in a construction stage;

(3) carefully planning the construction sequence of the concrete structure to reduce the shrinkage stress and cracking of the newly cast concrete in the hardening process, the construction interval of layered casting and the like as much as possible;

(4) curing the concrete comprises controlling the humidity and the temperature of the concrete; the newly cast concrete should be maintained as soon as possible to avoid the evaporation of water; the wet maintenance is not interrupted, and the initial wet maintenance is particularly paid attention to, so that the surface of the newly poured concrete is prevented from being exposed in the air too early;

(5) Thickness requirement of steel bar protective layer

(1) Setting enough protective layer thickness according to the standard requirement, and adding measures such as ultrasonic detection and the like to ensure the construction quality if necessary, ensuring that all parties increase the attention on the protective layer thickness and take corresponding strengthening measures;

(2) the thickness standard of the main reinforced concrete net protection layer is as follows: not less than 1/2 of the nominal diameter of the steel bar or the diameter of the post-tensioned pipeline, and meets the following requirements: main reinforcement: 4 cm-4.5 cm; hooping: 2.5 cm-3.0 cm; surface anti-cracking steel bar: 2 cm-2.5 cm.

Example 7:

in order to better complete the full-scale test method, in this embodiment, a large-volume RPC pumping and joint surface performance test, a large-volume RPC flow rate test, a large-volume RPC pouring whole-process drill, and a large-volume RPC temperature control and shrinkage control are required to be performed in the RPC concrete pouring construction process.

1. Large volume RPC pumping and faying surface performance testing

The main test contents of the large-volume RPC pumping and pouring test are as follows: (1) high-temperature setting time test, (2) pumping performance test, and (3) interface bonding performance test. The large-batch pumping performance of the RPC is actually measured on site, and the influence of temperature rise caused by hydration heat on the RPC condensation time, particularly the cold joint problem between pouring layers is actually measured. One surface is reserved in each of four directions of the full scale for experimental observation, and the three directions are respectively as follows: performing no treatment, removing the mould, polishing the inner surface of the template, and pre-burying the studs; meanwhile, temperature and humidity monitoring of a field test is well carried out.

Different bonding performance tests are carried out on four surfaces of the full-scale test block, as shown in figure 15, different interface treatments are respectively carried out on four inner surfaces of the full-scale test block with the thickness of 4m multiplied by 4m, then C60 steel fiber concrete is poured after the treatment, and the interfaces of RPC and C60 steel fiber concrete are observed. The contact position of the C60 steel fiber concrete block and the RPC test block is the top, so a template support system (supported by a scaffold) needs to be made, and the size of the C60 steel fiber concrete block is 2m multiplied by 0.5m (the single weight is about 1.4 t). And (4) perforating the outer part of the RPC pouring front template to reserve a reinforcing steel bar for connecting post-poured C60 steel fiber concrete. And pouring C60 steel fiber concrete after the temperature of the RPC full-scale test block is reduced to the ambient temperature and the mould is removed.

The method mainly comprises the following steps:

(1) according to a reinforcement arrangement mode, extending the reinforcement to the outside of the template for connecting with the C60 steel fiber concrete reinforcement;

(2) in the pre-embedding scheme, the studs need to be pre-embedded in advance;

(3) removing the mould after the RPC full-scale test block is cooled to the ambient temperature, and then carrying out an interface bonding performance test.

And reinforcing bars are also arranged in the C60 steel fiber concrete, and the reinforcing bars are consistent with the reinforcing bars in the lower tower column structure. The steel bar of the interface of the C60 steel fiber concrete and the RPC,

the binding power of RPC and C60 steel fiber concrete and the binding power of RPC and RPC need to be verified respectively in the laboratory:

(1) the cohesive force test mainly tests the tensile strength and the compressive strength of the bonded test block;

(2) designing different shear groove forms, and testing the tensile strength and the breaking strength of the test block;

(3) the formed mini-beam tests for interface failure.

2. Large volume RPC flow rate test

The main structure of the tower beam consolidation section has high reinforcement ratio, and is densely provided with prestressed pipelines, which is not beneficial to the rapid flow of RPC,

it is therefore necessary to verify the flow rate of the RPC and the distribution of the steel fibres at the same time as the full-scale test.

(1) On-site protocol 1: full-scale test block: in the process of pouring the full-scale test block, the pump pipe is perpendicular to the center position of the test block, timing is started from the pouring, and the time of the RPC from the center position of the test block to the edge position is recorded, as shown in fig. 16.

(2) The field scheme is that 2: temperature rise environment simulation: the steel bar of 2m × 0.5m × 0.5m is made according to the full-scale test block reinforcement, pouring is carried out from one end, the time for the RPC to flow to the other end and the time for the whole test block to be poured are tested, and the change of the steel fiber content inside the pouring end and the end RPC is tested at the same time, as shown in FIG. 17.

3. Full-process drilling of large-volume RPC pouring

The one-time pouring amount of the full-scale test reaches 64m ³ And the casting amount is large, so that the whole solid structure casting process can be performed, and the main drilling contents are as follows:

(1) RPC stirring amount actual measurement drilling

Pouring a full-scale test block by adopting 2 3m3 vertical shaft planetary mixers, wherein 3m is ³ The vertical shaft planetary stirrer stirs according to the maximum volume of 83 percent, and the single stirring amount is 2.5m ³ The total amount of the full-scale test block is 96.5m3, the planned stirring amount is 110m3 in consideration of material loss in the stirring and pumping processes, and the stirring is required for 44 times according to the single stirring amount, and the specific stirring plan is shown in the fourth table: TABLE IV RPC concrete mixing plan

The stirring place is arranged opposite to the project part, the distance from the pouring place is about 1km, the carrying capacity of a single tank car is 8m & lt 3 & gt, the discharge capacity of a stirrer is combined, the stirring is carried out for 3 times, the single carrying capacity is 7.2m3, the total transportation is carried out for 11 times, and 4 tank cars are planned to be transported.

A day pump is adopted for pumping, the discharge amount per hour is 60-80m ³ The full-scale test block is completely pumped once in one hour, and in order to ensure the preview authenticity, the pump distance of the full-scale test block is 4m multiplied by 4m, and the full-scale stone block is at least about 40m.

4. Large volume RPC temperature control and contraction control

The main contents of the large-volume RPC temperature control and shrinkage test are as follows: based on the early-stage simulation result, the temperature control of the large-volume RPC is carried out by the following means: (1) reducing the mold-entering temperature of the RPC, (2) preparing the low-shrinkage RPC, and (3) arranging a cooling water pipe. And carrying out hydration heat release and deformation monitoring on the whole full-scale test block from the pouring of the full-scale test block to the formal construction of the structure. The main study content is decomposed as follows:

(1) Preparation of low-shrinkage low-hydration-heat RPC material

Preparing a low hydration heat and low shrinkage RPC material, controlling hydration temperature rise from a material end, controlling 28d shrinkage of RPC within 200 microstrain and early plastic shrinkage within 800 microstrain; the low hydration heat RPC is prepared by adopting a mode of a large-mixing-amount mineral admixture, and compared with the traditional RPC material, the self hydration heat is reduced by more than 30%, so that the hydration temperature rise control of the material end is realized.

(2) Mold-in temperature control

The stirring water temperature is reduced by adding ice blocks, the mold-entering temperature of the RPC is controlled at 20 ℃, and according to the previous simulation calculation, the temperature of the freshly-mixed RPC can be reduced by at least 1 ℃ every time 10kg of ice is added. The ice adding amount is changed according to the requirements of environment temperature and pouring temperature, the maximum ice adding amount is 50 percent of the water consumption, and the engineering is taken to be 80kg/m ³ . Considering the temperature rise in the concrete transportation, pumping and pouring processes, the pouring temperature can reach a control standard of less than or equal to 20 DEG CAnd (5) performing standard requirements.

While embodiments of the invention have been shown and described, it will be understood by those of ordinary skill in the art that: many changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of the invention is defined by the claims and their equivalents.

Claims (10)

1. A full-scale test method for large-volume RPC reactive powder concrete is characterized by comprising the following steps:

(1) Preparing and premixing RPC concrete raw materials;

(2) Installing and debugging stirring equipment;

(3) Mounting a full-scale test block steel bar template;

(4) RPC concrete production stirring;

(5) RPC concrete pouring construction;

(6) Dismantling the RPC concrete template and maintaining the RPC concrete template in a heat preservation way;

(7) And (5) carrying out a performance test experiment on the formed RPC concrete test block.

2. The full-scale test method of the large-volume RPC reactive powder concrete in the claim 1, wherein in the step (1), the raw materials of the RPC concrete premix include cement, fly ash micro-beads, granulated blast furnace slag powder, silica fume and fine aggregate.

3. The full-scale testing method of the large-volume RPC reactive powder concrete according to claim 1 or 2, wherein in the step (2), the stirring equipment is at least two vertical shaft planetary mixers.

4. The full scale test method for the large-volume RPC reactive powder concrete according to claim 1 or 2, wherein in step (3), the concrete steps of installing the full scale test block steel bar formwork include:

(3.1) determining a pouring forming scheme of the finally formed RPC concrete test block;

(3.2) cleaning the site, and performing measurement lofting;

(3.3) erecting a supporting template;

(3.4) arrangement of cooling water pipes;

(3.5) arranging temperature monitoring equipment and a strain monitoring instrument in advance to prepare for later-stage water temperature rise and structural deformation detection of the test block;

and (3.6) installing the steel bundle sleeve and the steel bar binding.

5. The full-scale test method for large-volume RPC reactive powder concrete according to claim 4, wherein in step (3.1), the casting scheme for determining the final RPC concrete is two:

(3.1.1) setting a post-pouring strip, arranging a post-pouring strip between a tower beam consolidation section and a lower tower column, separating the tower beam consolidation section from the lower tower column without breaking a reinforcing steel bar, and after the tower beam consolidation section is poured, pouring the post-pouring strip by grouting, wherein the volume of a test block is 4m multiplied by 4m and is used for verifying the hydration heat release, stress strain deformation, temperature rise rule, pouring process and C60 interface binding power of large-volume RPC concrete; the verified parameters comprise temperature rise and temperature drop curves, stress-strain distribution and rule, deformation, pouring efficiency and interface bonding force;

(3.1.2) a cross parting post-pouring scheme, namely dividing the tower beam consolidation section into four blocks, reserving cross seam post-pouring belts, and pouring the post-pouring belts after the four blocks are demoulded; the volume of the test block is 4m multiplied by 2m, and the test block is used for verifying the block pouring, post-pouring belt treatment and prestress influence, and verifying the RPC pouring speed and steel fiber distribution; the verified parameters comprise the interface bonding effect of the post-cast strip, the blocking pre-stress effect, the influence of the cold joint, and the temperature control effect compared with the flow rate and the pouring effect of the RPC under the high reinforcement condition.

6. The full-scale test method for the large-volume RPC reactive powder concrete according to claim 5, wherein in the step (3.3), the concrete process of erecting the supporting formwork is as follows:

(3.3.1) installing pressing strips on the outer side of the bottom of the template;

(3.3.2) fixing the foundation bolt or the expansion bolt;

(3.3.3) installing a vertical template;

(3.3.4) reinforcing the template;

(3.3.5) tensioning the counter-pulling screw rod;

and (3.3.6) carrying out template acceptance.

7. The full-scale test method for the large-volume RPC reactive powder concrete according to claim 5, wherein in the step (3.4), the outer diameter of the cooling water pipe is 48.3mm, the wall thickness of the cooling water pipe is 3.5mm, the bent pipe part of the cooling water pipe is pretreated by a cold bending process, the cooling water pipes are tightly connected by all-welded joints, and the suspended part of the cooling water pipe needs to be welded with vertical ribs to fix the cooling water pipe.

8. The full-scale testing method of the large-volume RPC reactive powder concrete in the claim 1 or 2, wherein in the step (5), the RPC concrete pouring construction process needs to be performed with a large-volume RPC pumping and joint surface performance test, a large-volume RPC flow rate test, a large-volume RPC pouring whole-process drilling, and a large-volume RPC temperature control and shrinkage control.

9. The full-scale test method for the large-volume RPC reactive powder concrete according to claim 1 or 2, wherein in the step (6), (6) the specific processes of RPC concrete form demolition and heat preservation maintenance are as follows: covering and curing the concrete surface by using a film after the concrete surface is completely subjected to slurry collection, dismantling the template after the curing is carried out until the strength of the concrete reaches 90%, paying attention to the fact that corner concrete cannot be knocked down in the template dismantling process, and timely treating the corner concrete with the same grade if a corner defect occurs; after pouring, the concrete is manually smoothed and trowelled, a layer of plastic film and a layer of heat-preservation straw curtain quilt are immediately covered, and then the heat-preservation cotton quilt, the film and the rock wool quilt are sequentially covered so as to ensure the surface temperature and the humidity of the test concrete, and the rock wool quilt is adjusted in an increasing or reducing mode according to the temperature measurement condition.

10. The full-scale testing method of the large-volume RPC reactive powder concrete according to claim 1 or 2, wherein the step (7) of performing a performance test experiment on the formed RPC concrete test block specifically comprises: hydration temperature rise test, mechanical property test and volume stability test.

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