CN114620986B - Concrete for open caisson and pouring method thereof - Google Patents

Abstract

The invention discloses concrete for an open caisson and a pouring method thereof, wherein the concrete comprises the following components in parts by weight: 180-260 parts of cement, 110-150 parts of fly ash, 400-800 parts of coarse aggregate, 450-570 parts of fine aggregate, 12-25 parts of composite anti-dispersant and 90-130 parts of water. The pouring method comprises the following steps: the concrete is poured by a vertical conduit method. The invention has good fluidity, does not need to be vibrated, has high construction speed, takes the recycled aggregate of the construction waste as the coarse aggregate, reduces the dependence on the natural aggregate and reduces the construction cost; meanwhile, the segregation resistance of the concrete is improved by adding the composite anti-dispersing agent, and the problems of poor pouring compactness and low strength of the deep-water open caisson concrete are effectively solved.

Description

Concrete for open caisson and pouring method thereof

Technical Field

The invention belongs to the technical field of open caisson construction, and particularly relates to concrete for an open caisson and a pouring method thereof.

Background

The open caisson is a well body structure which is manufactured in advance on the ground and is sunk to a certain depth underground by a method of removing the soil in the well. The open caisson construction method is a special and important construction method for building underground structures or deep foundation engineering. As the open caisson construction has the characteristics of smaller required construction operation surface, no serious influence on the surrounding environment in the construction process and the like, the open caisson construction is more and more widely applied to municipal engineering at present and shows the trend of wider application range.

The open caisson wall and the bottom sealing concrete are generally constructed in an underwater pouring mode, and the water depth can reach tens of meters generally when the open caisson concrete is operated underwater. It is known that although cement is a hydraulic material, when concrete mixture is directly poured into water, concrete aggregate is seriously separated from cement due to the flushing action of water during falling and flowing, and part of cement is carried away by water flow and is in a suspended state for a long time. When the cement subsides, it tends to set and lose its ability to bond the aggregate. Concrete mixture that directly pours like this in aqueous often demonstrates the condition of grit aggregate loose pile, the middle thin and very low cement flocculating constituent of intensity or cement sediment of inclusion, and to open caisson basis, this phenomenon very easily appears pouring at first, receives the more serious wall of a well root of a well of water washing, and the cooperation atress of direct influence filling concrete and outside wall of a well and the whole bearing capacity of structure cause the hidden danger for engineering construction quality. How to ensure the concrete to be compact and not to be separated becomes the subject of the research on the design of the underwater concrete mixing ratio of the well wall.

CN111364469A discloses an underwater concrete pouring device, a construction method and an application of the underwater concrete pouring device in an ultra-large deepwater open caisson foundation, wherein the underwater concrete construction method comprises the following steps: firstly, pouring anti-dispersion concrete to cover the well wall and the bottom of the base, and standing for 5-10min after finishing; then self-compacting concrete is poured. The concrete material composition of the anti-dispersion concrete comprises the following components in parts by weight: 300-400 parts of silicate or ordinary portland cement above 42.5 level, 0-100 parts of fly ash above II level, 0-60 parts of mineral powder above S95 level, 700-900 parts of river sand with fineness modulus of 2.3-3.0, 800-1000 parts of continuous graded or secondary graded broken stone with maximum particle size of less than or equal to 20mm, 180-220 parts of drinking water, 5-15 parts of anti-dispersing agent and 8-15 parts of polycarboxylic acid high-performance water reducing agent with water reducing rate of not less than 25 percent, wherein the self-compacting concrete comprises, by weight, 250-350 parts of silicate or ordinary portland cement above 42.5 level, 0-150 parts of fly ash above II level, 0-60 parts of mineral powder above S95 level, 700-900 parts of river sand with fineness modulus of 2.3-3.0, 800-1000 parts of continuous graded or secondary graded broken stone with maximum particle size of not less than 20mm, 160-190 parts of drinking water and 4-10 parts of polycarboxylic acid high-performance water reducing agent with water reducing rate of 25 percent. The underwater concrete construction method is suitable for construction of the ultra-large deep open caisson foundation, can effectively solve the problems that the underwater concrete of the ultra-large deep open caisson foundation is easy to wash and separate, the strength is obviously reduced, the pouring is not compact and the like, and ensures the engineering construction quality.

At present, a design method and a construction process for open caisson construction become mature day by day, but research on concrete special for the open caisson is relatively less, so that the concrete special for the open caisson is developed, good working performance of the concrete under a long-time underwater pouring construction condition is guaranteed, and the method has important significance.

Disclosure of Invention

In view of this, the invention provides a concrete for open caisson and a pouring method thereof.

In order to achieve the purpose, the invention adopts the following technical scheme:

the concrete for the open caisson comprises the following components in parts by weight: 180-260 parts of cement, 110-150 parts of fly ash, 400-800 parts of coarse aggregate, 450-570 parts of fine aggregate, 12-25 parts of composite anti-dispersant and 90-130 parts of water.

Preferably, the composite anti-dispersant comprises a flocculant, a swelling agent, soluble soy polysaccharide and silica fume.

Preferably, the mass ratio of the flocculating agent to the swelling agent to the soluble soybean polysaccharide to the silica fume is 3-7:1-3:2-4:1.

preferably, the flocculant is polyacrylamide.

Preferably, the expansion agent comprises a low alkali expansion, air entraining and set retarding component.

Further preferably, the mass ratio of the flocculant to the swelling agent to the soluble soybean polysaccharide to the silica fume is 5:2:3:1.

preferably, the cement is ordinary portland cement.

Preferably, the coarse aggregate is construction waste recycled material with the particle size of 5-20 mm.

Preferably, the fine aggregate is sand with the particle size of less than 5mm, and the sand is natural sand and/or machine-made sand.

The invention also provides application of the concrete in open caisson construction.

The invention also provides a concrete pouring method, which adopts a vertical conduit method to pour the concrete.

Preferably, the relationship between the radius of action of the conduit and the overpressure at the lower mouth of the conduit is as follows:

overpressure kPa	75	100	150	250
					Radius of action m of catheter	＜2.5	3.0	3.5	4.0

Preferably, the conduit is a phi 200PVC pipe.

Preferably, the pouring amount of the conduit is 6-8 cubic meters per hour per pipe.

The invention has the beneficial effects that:

the concrete for the well sinking has good fluidity, does not need vibration and has high construction speed, and meanwhile, the building waste recycled aggregate is used as the coarse aggregate, so that the dependence on natural aggregate is reduced, and the construction cost is reduced; the segregation resistance of the concrete is improved by adding the composite anti-dispersing agent, and the problems of poor pouring compactness and low strength of the concrete of the deepwater open caisson are effectively solved.

Detailed Description

To make the objects, technical solutions and advantages of the present invention clearer, the following embodiments of the present invention are described in conjunction with specific embodiments, and before the embodiments of the present invention are further described, it should be understood that the scope of the present invention is not limited to the specific embodiments described below; it is also to be understood that the terminology used in the examples is for the purpose of describing particular embodiments only, and is not intended to limit the scope of the present invention.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

The sources of the raw materials used in the present invention are not limited, and the raw materials used in the present invention are all those commonly available in the art unless otherwise specified. The adopted cement is 32.5 common portland cement, the adopted flocculant is polyacrylamide, the molecular weight is 3500 ten thousand, the expanding agent is a ZM-6 type multifunctional concrete expanding agent which is purchased from an Alum mineral accelerating agent factory in Anhui province, soluble soybean polysaccharide is overdue food-grade soluble soybean polysaccharide, coarse aggregate is a construction waste recycled material with continuous grading grain diameter of 5-20mm, fine aggregate is machine-made sand with continuous grading and grain diameter less than 5 mm.

1. Performance evaluation of concrete special for open caisson

1. The formula (parts by weight) of the special concrete for verifying the open caisson is shown in table 1.

TABLE 1

Wherein, in the composite anti-dispersant in the embodiment 1, the mass ratio of the flocculating agent to the swelling agent to the soluble soybean polysaccharide to the silica fume is 3:1: 4:1;

in the composite anti-dispersant of example 2, the mass ratio of the flocculant, the swelling agent, the soluble soybean polysaccharide and the silica fume is 4: 3:2:1;

in the composite anti-dispersant of example 3, the mass ratio of the flocculant, the swelling agent, the soluble soybean polysaccharide and the silica fume is 6:2:4:1;

in example 4, the mass ratio of the flocculant, the swelling agent, the soluble soybean polysaccharide and the silica fume in the composite anti-dispersant is 5:2:3:1;

in example 5, the mass ratio of the flocculant, the swelling agent, the soluble soybean polysaccharide and the silica fume in the composite anti-dispersant is 7:1:2:1;

in example 6, the mass ratio of the flocculant, the swelling agent, the xanthan gum and the silica fume in the composite anti-dispersant is 5:2:3:1.

2. the properties of the open caisson concrete are shown in table 2.

TABLE 2

The embodiment shows that the replacement of the recycled aggregate of the construction waste to the natural aggregate is realized by improving the components of the composite anti-dispersant and adjusting the using amounts of cement, fly ash, fine aggregate, coarse aggregate and the like, and the prepared concrete special for the open caisson has good fluidity, does not need vibration, has good segregation resistance and high strength.

The invention also provides application of the concrete in open caisson construction.

The invention also provides a concrete pouring method aiming at the concrete, which adopts a vertical conduit method to pour the concrete.

The method specifically comprises the following steps: a concrete pouring platform is built on the well surface, and phi 200PVC pipes are prepared to be used as concrete guide pipes, funnels, water-proof balls, lifting equipment, hole cleaning equipment, water jetting equipment and water pumping equipment.

The relationship between the effective radius of the conduit and the overpressure at the lower opening of the conduit is as follows:

overpressure kPa	75	100	150	250
					Radius of action m of catheter	＜2.5	3.0	3.5	4.0

Two points are poured simultaneously at a time, and the concrete of the example is poured by a vertical conduit method.

Before the concrete is poured, the concrete is guided into water by a water-stop ball tied by an iron wire, and the distance between the surface of the bottom of the conduit and the sand surface is 20cm.

The concrete pouring speed is uniform, and each point is guaranteed to have the pouring amount of 6-8 cubic meters per hour.

And after the concrete is poured, sending an underwater frogman to check the pouring quality, and pouring the loophole if the loophole exists.

The concrete for the well sinking has good fluidity, does not need vibration and has high construction speed, and meanwhile, the building waste recycled aggregate is used as the coarse aggregate, so that the dependence on natural aggregate is reduced, and the construction cost is reduced; the anti-dispersion property of the concrete is improved by adding the composite anti-dispersing agent, and the problems of poor pouring compactness and low strength of the deep water open caisson concrete are effectively solved.

It should be emphasized that the embodiments described herein are illustrative and not restrictive, and thus the present invention includes, but is not limited to, the embodiments described in the detailed description, as well as other embodiments that can be derived by one skilled in the art from the teachings herein.

Claims (7)

1. The concrete for the open caisson is characterized by comprising the following components in parts by weight: 220 parts of cement, 130 parts of fly ash, 600 parts of coarse aggregate, 510 parts of fine aggregate, 14 parts of composite anti-dispersant and 110 parts of water, wherein the mass ratio of the composite anti-dispersant is 6:2:4:1, flocculant, swelling agent, soluble soybean polysaccharide and silica fume; or

240 parts of cement, 140 parts of fly ash, 700 parts of coarse aggregate, 540 parts of fine aggregate, 12 parts of composite anti-dispersant and 120 parts of water, wherein the composite anti-dispersant is prepared from the following components in parts by mass: 2:3:1, flocculant, swelling agent, soluble soybean polysaccharide and silica fume;

the expanding agent comprises low-alkali expanding, air entraining and slow-setting components; the coarse aggregate is construction waste recycled material with the particle size of 5-20 mm.

2. The concrete of claim 1, wherein the flocculating agent is polyacrylamide.

3. The concrete according to claim 1, wherein the cement is ordinary portland cement.

4. The concrete according to claim 1, wherein the fine aggregate is sand having a particle size of less than 5 mm.

5. Use of a concrete according to any one of claims 1 to 4 in open caisson construction.

6. A method of casting concrete, characterized in that the concrete according to any one of claims 1 to 4 is cast by a vertical duct method.

7. The casting method according to claim 6,

overpressure kPa 75 100 150 250 Radius of action m of catheter ＜2.5 3.0 3.5 4.0

The relationship between the radius of action of the conduit and the overpressure at the lower opening of the conduit is as above.