CN111548107A

CN111548107A - Alkali slag concrete construction method

Info

Publication number: CN111548107A
Application number: CN202010475907.9A
Authority: CN
Inventors: 杜玉荣
Original assignee: NO4 CONSTRUCTION Co Ltd OF CHONGQING CONSTRUCTION ENGINEERING GROUP; Chongqing Construction Engineering Group Co Ltd
Current assignee: NO4 CONSTRUCTION Co Ltd OF CHONGQING CONSTRUCTION ENGINEERING GROUP; Chongqing Construction Engineering Group Co Ltd
Priority date: 2020-05-29
Filing date: 2020-05-29
Publication date: 2020-08-18

Abstract

The invention discloses a construction method of alkali slag concrete, which relates to the field of alkali slag concrete, and in order to achieve the aim, the technical scheme of the invention comprises the following steps: 1) preparing materials; 2) stirring; 3) transporting; 4) pouring; 5) and (5) maintaining. The defects of high viscosity, short setting time, large early shrinkage and the like of the alkali slag concrete mixture can be effectively overcome, and the pouring quality of the alkali slag concrete can be obviously improved.

Description

Alkali slag concrete construction method

Technical Field

The invention relates to a construction method of alkali slag concrete, and mainly relates to the field of alkali slag concrete.

Background

Alkali slag is researched and developed by multiple countries as an environment-friendly material, is known as a novel cementing material with the most development potential in twenty-first century, but the structural engineering implemented in China in recent years is not many, and the construction technical result can not be referred. At present, only a single country has established the application technical rule of the material internationally. The alkali slag concrete applied in the method can not adopt a pouring mode of concentrated stirring automobile transportation and pumping in a commercial concrete station at present due to the characteristics of larger contractibility, large viscosity and the like, and can only be simply and automatically mixed on site and transported by a tower crane or a trolley. Thus greatly reducing the construction efficiency and increasing the environmental pollution.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides the alkali slag concrete construction method, which can effectively overcome the defects of large viscosity, short setting time, large early shrinkage and the like of an alkali slag concrete mixture and can obviously improve the pouring quality of the alkali slag concrete.

In order to achieve the purpose, the technical scheme of the invention is as follows: the method comprises the following steps: 1) preparing materials; 2) stirring; 3) transporting; 4) pouring; 5) and (5) maintaining.

The technical principle and the beneficial effects of the invention are as follows:

the method can effectively overcome the defects of high viscosity, short setting time, large early shrinkage and the like of the mixture of the alkali slag concrete, ensures the implementation of a front bin process of cast-in-place, can obviously improve the casting quality of the alkali slag concrete, improves the construction efficiency of the cast-in-place structure of the alkali slag concrete, and avoids material waste.

Preferably, the ingredients comprise the following: the raw materials comprise slag powder, an additive, stone powder, an alkali solution, sand and broken stones, the water content of the raw materials is rechecked in advance on the same pouring day, and if the water content is not adjusted according to the requirement, the situation that the change of the water content influences the proportion of the raw materials due to untimely use is avoided.

Preferably, the slag powder, the broken stone, the stone powder, the sand and the additive are discharged to the stirring machine in sequence during stirring, the materials are uniformly stirred in a charging barrel of the stirring machine, and through multiple tests, the dust flying can be reduced by mixing the materials in the sequence, so that the concrete is more favorably and uniformly stirred. Then adding an alkali solution, stirring until the gelled material is discharged to obtain alkali slag concrete, and manually adding the alkali slag concrete at a hopper of a stirrer so as to ensure accurate dosage.

Preferably, the dry mixing time is 20-50s, so that the raw materials can be uniformly mixed in a dry mode.

Preferably, the stirring time is 110-130s after the alkali solution is added, and the reaction of the cementing material is sufficient to achieve the working performance. The initial setting speed of the alkali slag concrete can be accelerated after long-term stirring, and the alkali slag concrete is not beneficial to use.

Preferably, the discharged alkali slag concrete needs to be subjected to spot inspection, and the spot inspection content comprises the following steps: whether the raw materials used for stirring are consistent with the mixing proportion and whether the slump of the discharged concrete meets the design requirement of the mixing proportion; and (5) reserving a concrete test piece to test whether the strength meets the requirement of preparation strength. The discharged alkali slag concrete can meet the construction conditions, and the influence on subsequent construction is avoided.

Preferably, the spot check content of the alkali slag concrete further comprises machine-out slump, which is kept between 200 and 220mm, and the spot check frequency of each work class is at least 2 times, so that the subsequent construction is facilitated, and the rapid initial setting or the permanent non-setting is avoided.

Preferably, if silicate cement mortar or cement concrete residues exist in the transport vehicle or the bucket during the transportation process, the alkali slag concrete can be loaded only after the silicate cement mortar or the cement concrete residues are thoroughly cleaned, and water is strictly forbidden to be added into the stirring tank or the transport equipment after the transport loading, so that the solidification is avoided.

Preferably, the time from the beginning of adding the alkali solution for mixing to pouring and vibrating for molding should not exceed 40min, the initial setting time of the alkali slag concrete is 40-60min at the temperature of 5-20 ℃, the time exceeding the initial setting time not only has too low concrete slump and can not enter a mold, but also can be quickly set after pouring, thus a dog hole can be formed or vibrating is not compact in the continuous pouring process. .

Preferably, the pouring comprises distributing, driving, vibrating and smoothing.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments will be briefly introduced below, it is obvious that the drawings in the following description are only three of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

FIG. 1 is a flow chart of an alkali slag concrete construction process according to an embodiment of the present invention;

FIG. 2 is a sequence diagram illustrating the feeding and stirring operations according to an embodiment of the present invention;

fig. 3 is a time line of a casting process according to an embodiment of the present invention.

Detailed Description

The technical solutions in the present invention will be described clearly and completely with reference to the accompanying drawings, and it is to be understood that the described embodiments are merely preferred embodiments of the present invention, rather than all 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, shall fall within the protection scope of the present invention.

Examples

As shown in fig. 1, the embodiment of the present invention is as follows:

1 preparation for construction

Technical preparation: the site layout principle is as follows: the equipment producing noise, dust and volatile gas is far away from residential areas as far as possible, and the stirrer is provided with a sound insulation board room covering device and an automatic feeding, proportioning and circulating heating device specially designed for the alkali solution storage tank.

Material preparation

1. And (5) compiling a material approach plan according to the design mixture ratio and the pouring plan, and advancing the material by 1d in advance according to the plan.

2. And (5) inspecting the water content of the sandstone when the sandstone enters a field, proposing a construction mixing ratio, and calculating the material consumption of each disc. The reference mixing ratio of C40 is as follows:

3. trial assembly is carried out according to the construction mixing proportion and the calculated material consumption of each plate, so that various materials can be effectively utilized, and the working performance of the concrete product meets the design requirement.

4. The slag powder, the admixture and the river sand have the waterproof and moistureproof requirements, and a material greenhouse is built or stored indoors; the alkali solution is prepared by a chemical factory with professional qualifications according to parameter indexes, and is transported to the site in advance to be stored in a circulating heat-preservation storage tank.

1.4 pour floor preparation

According to the requirements of construction drawings, a steel bar formwork is manufactured and installed, a supporting frame and an embedded part are checked, sawdust sundries on the formwork are cleaned, a cushion block is well cushioned, the elevation is well read, a stay wire is used for finding a slope, and hidden engineering acceptance is carried out according to the provisions of the concrete structure engineering construction Specification GB 50666.

Before pouring the alkali slag concrete, wetting the surface of the template by using an alkali solution, but not excessively accumulating liquid on the surface of the template.

1.4 pour floor preparation

2 ingredients

2.1 Water content by Re-examination

And (4) sampling and testing the water content 1h in advance on the casting day, and if the water content fluctuates obviously with the approach, temporarily adjusting the construction mix proportion. The change of the water content of the production sand is detected at random in the production process, and the time of each shift is not less than 1.

2.2 Material warehousing

And sequentially loading the water-quenched blast furnace slag powder, the broken stone, the stone powder and the sand into a No. 1-4 bunker of the proportioning machine for later use by a loader.

2.3 batching and feeding

1. According to the construction mixing proportion after rechecking, the discharge weight of each bin is set on a numerical control batching machine, and the materials are discharged in the sequence of 'water quenching blast furnace slag powder → broken stone → stone powder → sand', and are conveyed to a hopper of a stirring machine by a conveying belt for standby. Through a plurality of tests, the materials are prepared according to the sequence, so that the dust flying can be reduced, and the concrete can be stirred uniformly.

2. The special additive is customized by a manufacturer, is subpackaged into small bags, and is manually added at the hopper of the stirrer so as to ensure the accurate dosage.

3 stirring

As shown in fig. 2:

3.1 Dry mixing

And (3) putting the dry mixture prepared in the hopper of the stirrer into the charging barrel of the stirrer, and uniformly stirring for 30 s.

3.2 adding alkali solution and stirring

1. Setting the liquid outlet amount of each plate on a numerical control device of an alkali solution storage tank according to the construction mixing proportion after rechecking, and discharging the liquid after uniformly mixing the dry materials. The alkaline solution is conveyed along a feed line and flows into the drum from above the mixer drum.

2. The activity of the slag powder and the additive is activated from the moment of adding the alkali solution to form the gelled material. And adding the alkali solution, and stirring for 120s to ensure that the gelled material fully reacts to achieve the working performance. The stirring time is preferably 120s, and the initial setting speed of the alkali slag concrete can be accelerated after long-time stirring, so that the alkali slag concrete is not beneficial to use.

4 discharge and sampling test

1. The initial disc stirring of the alkali slag concrete needs to be subjected to disc opening identification, and the identification contents comprise: whether the raw materials used for stirring are consistent with the mixing proportion or not; whether the slump of the discharged concrete meets the design requirement of the mix proportion or not; and (5) reserving a concrete test piece to test whether the strength meets the requirement of preparation strength.

2. After the alkali slag concrete is mixed, the slump and the workability must be checked, and each work shift is not less than twice. Through actual measurement, the slump of the material discharged from the machine is generally controlled between 200 mm and 220mm by mixing according to the mixing proportion.

5 transport of

1. This engineering uses the cooperation of lifting bucket and tower crane to accomplish the transportation. Such as pouring terraces or roads, and can also be transported by using a small-sized dump truck.

2. If silicate cement mortar or cement concrete residues exist in the transport vehicle or the bucket, the alkali slag concrete can be loaded only after the silicate cement mortar or the cement concrete residues are thoroughly cleaned, and water is strictly forbidden to be added into the stirring tank or the transport equipment after the alkali slag concrete is transported and loaded.

3. The transport time of the concrete directly influences the pouring of the alkali slag concrete and the setting speed after pouring. And (4) summarizing through multiple times of actual measurement: the initial setting time of the alkali slag concrete is 40-60min, and the final setting time is 180-300min at the temperature of 5-20 ℃. The time from the beginning of adding the alkali solution for mixing to the pouring vibration molding should not exceed the initial setting time of the mixture, otherwise, the slump of the concrete is too low, the concrete cannot enter a mold, and the concrete is quickly condensed after pouring, so that a dog hole can be formed or the vibration is not compact in the continuous pouring process.

4. In general, when the slump of the alkali slag concrete discharged from the machine is measured to be between 180 and 220mm, a dump truck, a trolley or a tower crane can be adopted for transportation; when the slump of the alkali slag concrete discharged from the machine is actually measured to be between 120 and 180mm, the alkali slag concrete can be transported by a dump truck, and the alkali slag concrete is not suitable to be transported by a tower crane.

5. The alkali slag concrete mix cannot be exposed to high winds, rain and sun radiation during transport, and must be covered if this occurs.

6 pouring

As shown in fig. 3

6.1 distributing and driving flat

1. The processes are more in the stage from the concrete entering the formwork to the final setting, and operators and machines can influence the forming quality of the surface layer. In order to reduce the influence generated in the process, the casting is carried out from far to near according to the pre-divided casting area cloth. The concrete in the same area is continuously poured in a layered mode according to the sequence of the vertical structure and the horizontal structure; the pouring thickness of each layer of the vertical structure is preferably not more than 300-500 mm; when the floor slab is poured, the floor slab should be poured along the same direction of the short edges. The distance between post-cast strips is not more than 30 m.

2. The free height of the alkali slag concrete falling is not more than 2m, and when the free height is more than 2m, auxiliary tools such as a stringing barrel, a chute and the like are added.

3. The virtual pavement thickness of the paving alkali slag concrete is 1.1-1.2 times of the actual thickness. Because the viscosity of the alkali slag concrete is larger, a vibrating bar or a flat vibrator is used for dragging the concrete to be leveled, then a roller is used for rough leveling, and finally a trowel is used for trowelling and fine leveling.

6.2 vibrating

Vibrating by using an inserted high-frequency vibrating rod with the frequency of more than or equal to 180Hz, wherein the inserted distance is not more than the vibration action radius of the vibrating rod and is about 500 mm. When continuous multi-layer pouring is carried out, the vibrating rod is inserted into the mixture at the lower layer by about 50-100 mm, the vibrating time is before the initial setting of the lower layer, and the vibrating duration is preferably 20-40 s.

6.3 smoothing and leveling

1. Horizontal members such as beams and plates should be smoothed and polished by iron plates immediately after the vibration is finished. In order to solve the viscosity problem of the alkali slag concrete, a small amount of alkali solution can be used for pouring and spreading on the surface of the concrete and then the concrete is immediately polished, so that a better appearance effect can be achieved.

2. And (3) carrying out secondary plastering and pressing by using a flat vibrator when the concrete is close to the initial setting, and immediately covering by using a plastic film after plastering and pressing are finished.

The method combining the tight covering and the secondary plastering is one of important measures for preventing the alkali slag concrete structure from cracking, and the process must be strictly executed. The covering function is to reduce the water dispersion on the concrete surface to form plastic shrinkage cracks. The secondary plastering is to carry out timely sealing treatment on the existing plastic shrinkage micro cracks and defects on the surface of the secondary plastering so as to avoid development and expansion.

7 curing

1. The alkali slag concrete column, the shear wall and other vertical components doped with the retarder in the engineering are preferably maintained for not less than 72 hours with a mould. When the side mold is disassembled, the surface and edges of the alkali slag concrete member are not damaged due to the disassembly of the mold.

2. The method for moisturizing and maintaining after the form removal comprises the following steps:

after the surface covering material of the concrete is removed or the mould is removed, the concrete is treated by watering maintenance, when the surface of the concrete is in a wet state, the exposed surface of the concrete is quickly covered or wrapped by geotextile and other materials, and then the geotextile and other moisture-preserving materials are wrapped by plastic cloth. During coating, the coating should be intact and completely lap-jointed with each other, and the inner surface should have condensation beads. The coating moisture-retention curing time of the concrete is prolonged as much as possible under the condition that the moisture-retention curing time is not less than 14 days. In-place maintenance measures can reduce early shrinkage.

8 construction joint treatment

The construction joint should be left at the joint part between the alkali slag concrete and the common concrete, or because the construction joint is left after exceeding the initial setting time of the alkali slag concrete, before the alkali slag concrete is poured, the construction joint must be processed:

1. construction joint treatment conditions: determining that the compressive strength of the poured concrete must reach more than 1.2 MPa; the treatment can be started after about 300min when the ambient temperature is within 5-20 ℃.

2. On the hardened concrete surface, the cement slurry, loose stones and soft concrete layer are removed, at the same time, the concrete surface is roughened, the dust collector is used for sucking out the impurities, the alkali solution is used for fully wetting the interface, and the solution remained on the concrete surface is removed.

3. Laying a layer of alkali slag mortar or a special interface agent at the construction joint, wherein the thickness of a mortar connecting layer is not more than 30mm, the mixing proportion is the same as the components of the mortar in the concrete, and the special interface agent meets the requirements of the current standard.

4. When pouring is continued from the construction joint, attention is paid to avoid blanking directly close to the joint edge. Before the mechanical vibration, the construction joint is gradually pushed.

9 post-cast strip treatment

1. The concrete at the post-cast strip adopts micro-expansion concrete with the strength grade higher than that of the original concrete with an adjacent structure by one grade, and the anti-permeability grade is the same as that of the original component.

2. Post-cast strip construction process

Constructing concrete on two sides of the post-cast strip till the design stipulated time → cleaning sundries in a template of the post-cast strip and wetting the template → carrying out joint treatment on the post-cast strip → pouring the concrete of the post-cast strip in construction → detaching a bottom template of the post-cast strip after the concrete strength of the post-cast strip reaches 100%.

3. The joint treatment of the post-cast strip is the same as the joint treatment method of the construction joint.

10 cleaning and waste disposal

And after the pouring is finished on the same day, cleaning the stirrer and the transportation equipment by using clear water. The waste materials and the tank washing wastewater are collected by a special iron drum, and are sealed by a cover and are transported out in a centralized mode at regular time, so that the completion of work is completed.

The alkali slag concrete has the advantages of early strength, high strength, good frost resistance, good chemical corrosion resistance and the like, is particularly suitable for environments with special requirements on severe weather, severe chemical corrosion and the like, and has good application prospects in the aspects of solidification of electric poles, shield pieces and toxic wastes in sewage pipes and severe environments (such as high saline-alkali soil) and rapid rush repair of special engineering. Compared with the special cement used in the severe environment at present, the alkali slag cement has the advantages of excellent performance, less environmental pollution, low cost and good technical and economic benefits. Taking the sulfate resistance as an example, compared with the existing sulfate-resistant concrete, the sulfate-resistant concrete can save 50-100 yuan per m of 3 concrete, and the direct saving value of 10 ten thousand m of 3 alkali slag concrete applied to occasions with special performance requirements can reach 500-1000 ten thousand yuan per year. The construction efficiency of the alkali slag concrete cast-in-place structure is improved, and material waste is avoided.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims

1. The alkali slag concrete construction method is characterized by comprising the following steps:

1) preparing materials;

2) stirring;

3) transporting;

4) pouring;

5) and (5) maintaining.

2. The alkali slag concrete construction method according to claim 1, characterized in that: the ingredients comprise the following components: the raw materials comprise slag powder, an additive, stone powder, an alkali solution, sand and macadam, the water content of the raw materials is rechecked in advance on the same day of pouring, and the raw materials are adjusted if the water content is inconsistent.

3. The alkali slag concrete construction method according to claim 1 or 2, characterized in that: the stirring is to sequentially discharge the slag powder, the broken stone, the stone powder, the sand and the additive to a stirrer, uniformly stir in a charging barrel of the stirrer, then add the alkali solution and stir until the cementing material is discharged to obtain the alkali slag concrete.

4. The alkali slag concrete construction method according to claim 3, characterized in that: the dry mixing time is 20-50 s.

5. The alkali slag concrete construction method according to claim 3, characterized in that: the stirring time after adding the alkali solution is 110-130 s.

6. The alkali slag concrete construction method according to claim 3, characterized in that: the alkali slag concrete obtained by discharging needs to be subjected to spot inspection, and the spot inspection content comprises the following steps: whether the raw materials used for stirring are consistent with the mixing proportion and whether the slump of the discharged concrete meets the design requirement of the mixing proportion; and (5) reserving a concrete test piece to test whether the strength meets the requirement of preparation strength.

7. The alkali slag concrete construction method according to claim 3, characterized in that: the spot check content of the alkali slag concrete also comprises the machine-out slump, which is kept between 200 and 220mm, and the spot check frequency of each work class is at least 2 times.

8. The alkali slag concrete construction method according to claim 3, characterized in that: during transportation, if silicate cement mortar or cement concrete residues exist in the transport vehicle or the bucket, the alkali slag concrete can be loaded only after the silicate cement mortar or the cement concrete residues are thoroughly cleaned, and water is strictly forbidden to be added into the stirring tank or the transport equipment after the alkali slag concrete is transported and loaded.

9. The alkali slag concrete construction method according to claim 3, characterized in that: the time from the beginning of adding the alkali solution for mixing to pouring and vibrating for molding is not more than 40 min.

10. The alkali slag concrete construction method according to claim 1, characterized in that: and the pouring comprises distributing, leveling, vibrating and leveling.