Is it possible to pour concrete into water. Will concrete harden in water? Pouring cement into groundwater

Can concrete be poured into water? Sure. Concrete works under water are carried out in two ways: where the water depth is small and there is little excitement or no tides, immersion of the solution through the funnel is done in spaces that are fenced with lintels, or directly in the water; on the contrary, where there is great excitement and the depth of the water is large, work is carried out using caissons, into which concrete is lowered through pipes or shafts. Pouring into water is performed approximately as follows.

First fill method

In the first case, in the place where the concrete structure is to be erected, the sheet pile rows are driven in and concrete is thrown between them through the funnel. If the base is loose under the mortar and, for example, consists of scattered stone, then in order to avoid leakage of the mortar into the rubble with which the stone base is chipped, it is necessary to thoroughly crush the surface of the base and cover it with a cloth with the edges raised up.

Having prepared the concrete, it is necessary to leave it to mature for a while, covering it with a tarpaulin in case of sun or rain; this is necessary so that the concrete sets slightly, which will significantly reduce the loss from erosion of the solution when immersed in water. The English engineer Kinipple was the first to use the aforementioned curing of the mortar and dipped the already semi-hardened concrete mass in water in order to avoid high costs for the construction of means to prevent erosion of the immersed mortar before the water has time to harden its mass. To protect against the impact of waves and the pressure of flowing water, the outer surfaces of the freshly poured mortar Kinipple covers these surfaces with a thick canvas. The core of the structure is usually made of unsaturated solution, and the outer shell, one meter thick, from saturated:

• first: 6 parts of crushed stone per 1 part of cement, it remains to harden in air for 5 hours;
• second: 7 parts of crushed stone to 2 parts of Portland cement, remains in the air for 3 hours.

The time between mixing the solution and immersion in water must be commensurate with the properties of the used solution, hardening quickly or slowly. It is necessary to calculate this time so that when diving, on the one hand, a part of the cement is not lost from erosion by water, and on the other hand, the concrete is not hardened so much that it would lose the opportunity to contact tightly with the mass immersed before and become one monolith. When concrete is immersed in these places, which are subject to shock waves or strong currents, a small mass of rapidly hardening cement is added to its lowering. To compact the submerged concrete, a rammer is used, the top of which (located above the surface of the water) protrudes to take the blows of the ramming tool. Directly tamping must be done carefully so that there is no big concussion of the movement of water and the entire mass, which can contribute to the erosion of concrete.

The solution for this type of concrete is obtained from 1 part of cement and 2.5 parts of pure sand.

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Second fill method

Along the strip where some construction is planned to be erected, for example, a dam, two ditches are dug up along the bottom using excavating machines; semi-solidified concrete is poured into these ditches directly into the water in the form of two shafts, which are brought to a low water level. Depending on the state of the sea and the properties of the cement used to remove these shafts, the free concrete mass is immersed or lowered in coolants, as experience shows that such coolies are perfectly combined into one and form a single monolith. When the sketch of concrete for the formation of shafts is finished, they hammer in a slope, which will have slopes of the structure, iron piles. To connect the piles to each other, they put on iron rods with eyes. To keep piles in the same inclined position, steel cables are put on top of them, which are fastened to dead anchors.

Boards, which are covered with a cloth on the inside of the structure in order to prevent washing out by the waves of concrete, are laid on the inside of the piles. Partitions are made along the length of the structure from concrete arrays, which, using immersed and already started to set concrete, are connected inextricably with the lower layers, forming a monolith; This is confirmed by many experiments made recently, even with very low-saturated concrete. From these experiments it turns out that in order to save costs, it is possible to use low-saturated concrete, observing only that its components mix well with each other, and there is no excess water, and also that it is possible to immerse the concrete mass without harming the strength of the structure through a certain time after the setting process has begun. In the case of strong excitement and great depth, concrete work, as was said at the beginning, is carried out inside the caissons.

Usually, when the soil is prepared under the base, partitions of 1 to 1.2 m thick are built around the entire chamber, to the roof from the very bottom, and their walls are made of planks that are placed vertically and after hardening the concrete they are taken away. Concrete under the ceiling is pounded by a flat tamper. When filling concrete, it is useful to lay it in layers and do not lay down the next one until the previously laid one has hardened, which will take about 5 or 6 hours of time. The lowering of concrete is carried out using special pipes with valves from below and above.

Water is an important component for the preparation of mortars for the erection of structures and finishes. It is no secret that not any liquid is suitable for mixing cement, but that meets certain requirements. We will tell you what water should be for concrete and mortar and why you can not use liquid from any water tap.

Source selection problem

Concrete and other mortars on cement are distinguished by the strength of the finished product or coating. This property is provided by a special structure, which is formed as a result of hydration and chemical reactions of the components of the mixture with each other. The characteristics of the material are affected by the mineralogical composition of the solution, which is carefully selected.

The influence of water on the concrete brand cannot be underestimated - the liquid can both contribute to the acquisition of strength and other design parameters, and significantly reduce them due to the presence of such components in the composition:

1. Water with minerals in excess or insufficient amount can reduce the hardening rate, the final strength, prevent the formation of molecular bonds in the structure of the stone.
2. Organic contaminants (silt, mold) harm concrete in fact and in the long term: they prevent the mineral components from reacting and crystallizing qualitatively, over time, in a humid environment, organic matter develops and destroys the product throughout the volume.

Accordingly, you can only use water that complies with state regulations, that is, from water supply systems, but laboratory tested: unfortunately, a really good liquid rarely reaches the consumer due to the poor condition of the wired lines. The same applies to flushing fillers and watering young hardening concrete.

Standard

The quality of water for concrete and mortars is regulated by a special GOST 23732-2011 “Water for concrete and mortar. Technical conditions. " The document establishes restrictions on the presence in the environment of minerals and chemical compounds (tab. 1 GOST):

GOST describes in detail what water for concrete, as well as the criteria for assessing its quality during preliminary tests (tab. 3 of this standard):

If there is a convenient source of water supply before using the resource, a mandatory analysis is carried out and the obtained indicators are compared with the values \u200b\u200bfrom tab. Number 3. With their correspondence, water enters the work for mixing concrete and cement-based products.

The effect of chemical compounds on concrete quality

There is a lot of water in concrete - from 155 liters per 1 m 3, depending on the fraction of crushed stone, sand, and the expected grade of stone. The fluid interacts with every grain of sand and speck of cement, so its quality affects the entire volume of the future design. How do chemical compounds in water affect the properties of concrete, if we neglect the established standards of GOST?

• Sugar and phenols delay the hardening of concrete and greatly degrade its quality. The normalized content of these substances is 10 ml / liter;
• Petroleum products form a waterproof film on binder particles;
• Surfactants (soap residues) also envelop the components. Unlike improver improvers, they only give a hardening retardation;
• Soluble salts of sulfate ions and chlorine ions crystallize in the pores of concrete, leading to corrosion of stone and reinforcement. For this reason, water from the sea is strictly prohibited.

Wastewater, swamp and river water can be used for mixing concrete and cement, but only after cleaning and checking by the sanitary-epidemiological station.

Amount of water

The summary table shows the technological flow of water per cube in the production of concrete:

What determines the flow of water in concrete:

• Sand and gravel fraction;
• Brand of cement and its type;
• Expected concrete grade.

The volume of water in concrete should not exceed the norm - in the pursuit of plasticity, you can easily lose quality, excess fluid inhibits the hydration of cement, and concrete does not gain the expected strength. Accordingly, it is impossible to add it when mixing over the norm.

Too low water content of the concrete mortar will not allow the components to mix properly, and plasticity will be minimal.

To get concrete with good ductility and workability, use special plasticizers!

Is concrete poured into water? Yes, of course, and this can be done absolutely calmly, only works on underwater concreting have their own specifics. About whether concrete will harden in water and how to achieve this, and we will talk in the article below.

Work options

They can be carried out in two ways:

• at a shallow depth where there are no tides, and there are minor waves, the solution is lowered through a funnel into cavities enclosed by special jumpers, or concrete is poured into water;
• at rather impressive depths, in places where waves can be very strong, caissons become a reliable assistant in concreting work. Concrete mass in such caissons is moved through mines or pipes. Better not with your own hands, but with concrete pumps.

How is pouring carried out, what is the GOST for water for concrete and mortar? Consider this process in more detail.

Method number 1

The instruction is as follows:

1. It begins with the fact that in the place where the proposed structure will be erected, the rows of piles are clogged (sheet piles are used). This makes it possible to avoid sump operations.
2. Then concrete is thrown between them through a funnel.

Tip: if the base under the concrete mortar has insufficient density, for example, from scattered stones. In this case, it must first be densely chipped, and then covered with a cloth, the edges of which will be bent up. Thanks to such measures, the solution will not be able to seep into the rubble, and concreting will be much better.

We prepare concrete

After the base is ready, you need to prepare a solution. It is important to remember that he needs a certain time to mature. At the same time, direct sunlight or moisture should not fall on it.

If the solution is kept to the required time, then it will reach the desired consistency for immersion in water: it will set a little and will not be very eroded in water. This method of preparing the solution was first used by Kinipple, a British engineer.

In this way, he managed to avoid unnecessary costs for the installation of a system that allows to save concrete mortar from erosion. Kinipple dipped a solution under the water that was already half cured.

In addition, the engineer provided for the technology of its protection against the strength of waves and undercurrents. To do this, he covered the outside of the concrete surface with a dense linen cloth (canvas).

Tip: for a core of such a structure, use an unsaturated solution, while the outer part requires a saturated solution, while its thickness should be at least 1 m.

1. Depending on the characteristics of the speed, it is necessary to distribute the time between mixing it and moving it into water. It is important to calculate the time most optimally, so that when immersed, the concrete does not erode too much. Otherwise, some of the cement will be lost, which will negatively affect the quality of the structure.

1. It is also important to ensure that the concrete mass does not become too hard, because in this case it will not bond tightly with the solution that was previously immersed and will not become monolithic. In those underwater areas that are subject to powerful shock waves, strong currents, before lowering concrete into water, a small part of quick-hardening cement is added.

1. Among other things, dipped in water.  To ensure this, it is rammed. The top of the tamper is above the water level, taking the strokes of the tamping tool. Remember that tamping should be carried out very carefully, because if you overdo it, then too much vibration and waves will inevitably lead to erosion of concrete.

To obtain such concrete, you will need to mix cement with clean pitch in a ratio of 1 to 2.5.

Tip: the question of whether concrete passes water, you can answer - depends on the composition, so with it you can build water tanks.

Method number 2

1. Near the site where it is planned to build the necessary concrete structure, for example, a dam, using dredging machines, it is necessary to dig two ditches at the bottom. They should pour semi-hardened concrete, directly into the water. The result is two shafts that reach the low water level.

1. To remove these shafts, the concrete mass is immersed in water in the wings. This idea is not accidental, their value is that in the process they are able to form a monolith. After sketching cement for shafts, iron piles become clogged. Do it at an angle to get slopes.

1. Connect the piles to each other with special iron rods in which the eyes are made. To keep them at the right angle, put on a steel cable, which is attached to the dead anchors.

Tip: so that during strong waves concrete is not washed out, on the inside of the piles lay boards covered with a canvas.

1. Install concrete partitions along the entire length of the structure. The material for them should already be at the stage when it begins to dry out and harden. This will allow to form a monolithic part with the lower layers.

This technique allows you to save money, since solidity is guaranteed even with the use of low-saturated concrete. However, when working with low-saturated concrete, it is important to know that its components must mix very well and form a homogeneous mass. In addition, know that if there is a lot of water in concrete, its “seizure” is severely impaired.

Tip: immerse it in water after this mass has begun to set. If weather conditions are unfavorable (wind, strong waves) or concreting is carried out at great depths, work is carried out inside the caissons.

After the soil has been prepared for the base, install partitions 1-1.2 m thick around the chamber - from the roof to the very bottom. Make walls from vertically standing boards, which then remove as the concrete hardens. Under the ceiling, treat the mortar with a flat rammer.

Tip: it is best to lay concrete in layers, while you should not start the process of laying a new layer until the previous one has dried.

Hardening of one takes 5-6 hours. The concrete solution is lowered through special pipes, which are equipped with valves above and below.

Trumpet

In underwater concreting, a pipe is a very important device. Opening the top valve, you ensure that part of the concrete gets into it, after which it should be closed.

The air pressure in the device and in the chamber is equalized using a valve that connects them. Then you need to open the valve located below, so that the concrete falls under the water until its layer is sufficient to resist the pressure of the water.

Tip: if you don’t know how much water per cubic meter of concrete you need to spend, take an average of 125 liters.

After this, the solution is lowered through the mines. To reduce the consumption of material for filling the caisson, you can use stones from the bottom where the work is carried out, just pour them on top. At the moment, the maximum depth of underwater concreting works is no more than 30 m.

Output

Concreting in water is an important stage in the construction of hydraulic structures. With their help, it is possible to create dams, dams and other structures that do not collapse under the onslaught of waves. The article talked about two methods of pouring - using piles and concrete shafts (ascending solution).

The video in this article will help you find additional information on this topic.

Builders working at hydrogeological stations often face the need to fill directly under water.

Underwater concreting is the laying of a mixture under water without the use of a sump - suitable for the construction of underwater elements of bridges, bottoms of wells and other structures at a depth of 1.5 to 50 m.

Drainage under such conditions is impossible. Such construction work can be classified as particularly difficult. To concreting in water was successful, it is necessary to exclude the collapse of the cement mixture. Everyone knows that the cement mortar includes a certain amount of water, but it should be exactly the same as when laying under normal conditions. No more, no less. If there is too much water, the solution will lose its strength, construction simply will not be completed. Therefore, the whole complexity of the work will be to prevent water from entering the building material until it is fully adhered.

Usually, pouring in water is carried out by two methods: the ascending solution method and the ascending pipe method. The essence of these methods is that a closed space is enclosed around the solution until it completely hardens. Water cannot enter. Whatever method is used, the work will be very difficult. It’s very difficult for one person to cope with it; at least two more assistants will be needed.

Ascending pipe method

Scheme of concreting under water using the method of vertically moving pipes: 1 - formwork; 2 - working flooring; 3 - pipe links; 4 - loading funnel; 5 - vibrators; 6 - a rack; 7 - concrete; 9 - floating crane.

To work, you will need the following:

• mixture;
• pile site;
• winch;
• trumpet;
• hopper;
• traverse.

This method allows the construction of durable structures in water. Underwater work can be carried out at a depth of up to 50 meters. On the surface of the water directly above the construction site, a work platform is being built on stilts. A traverse must be installed there, a pipe of the required diameter is hung to it, but not less than 20 centimeters. A winch with workers should quickly lower and rise. This is necessary so that it is correct and that it does not fall into the water. The accuracy of lifting the pipe should not exceed 3 centimeters.

Scheme of concreting under water using the ascending mortar method: 1 - stone and gravel filling; 2 - solution; 3 - sheet pile formwork; 4 - fencing; 5 - flooring; 6 - mine; 7 - a pipe; 8 - winch; 9 - sleeve; 10 - mortar pump.

In order for concrete to get into the pipe, a bag is introduced into it. The mixture is poured into the bag through a special funnel. The base of the pipe under weight falls down, and water is forced out from under it. The filling continues until all the free space inside the pipe is filled. When the pipe is completely filled, pouring concrete is stopped. The pipe rises slightly, but so that its lower end is 1 cm below the beginning of concrete.

So, level by level, pouring under the reins takes place. The top layer of each level is considered the most unreliable, because water can get there. Before filling a new layer, it is deleted. If you need to concrete a large space, then one pipe will not be enough. Then apply several pipes with a large diameter.

The method of the ascending solution

The essence of this method: crushed stone is poured into the block, the free space is filled with a solution. The method can be divided into pressure and non-pressure. That is, concrete is poured under pressure and without it.

For work, you need the following materials:

• mixture;
• mine;
• coarse aggregate;
• seamless pipe;
• pump;
• sand.

Scheme of underwater concreting by ramming the mixture. For this method, a mixture with a draft of a cone of 5-7 cm is used.

Pressureless filling. All work is carried out in the mine. In the center of the mine is a construction site. A seamless pipe is placed around it. Under the pressure of the pipe, concrete enters into it and spreads as needed. No additional supply pressure is applied.

Pressure filling. Work is being done outside the mine. The pipe is immersed in stone or rubble under the action of pressure. A pump is used to increase the pressure. To

Concreting under water is a special technology for laying concrete mortar, used in the absence of the ability to pump out water or remove it in other ways. Most often, the method is in demand in the construction of large reinforced concrete structures, the operation of which involves significant loads. Bridges, dams, other hydraulic structures, as well as power transmission towers, wells in rock formations are structures that, in the construction of these structures, in many cases resort to underwater concreting.

Concreting in water is also used in projects of lesser scale. The inability to establish drainage from the pit with a high level of groundwater is a common situation during construction work.

There are several methods that allow pouring concrete into water:

• technology "vertically moving pipe" (VPT);
• BP or concreting due to climbing solution;
• ramming the concrete mixture;
• concrete laying with bunkers;
• bagging method.

The main thing to keep in mind when performing concrete laying works is that the main calculated mass of the mortar should not come into contact with water in order to avoid leaching of cement; the concreting process should go on continuously until reaching the level outlined by the project.

Preparatory work

Before you begin laying concrete directly in the water, you need to draw up a project that describes the order and progress of work, volumes of material, necessary equipment and equipment. As a rule, divers are required at considerable depths, who outline a plan for clearing the concrete site or clean it manually, set the formwork, and regulate the placement of pipes and hoses that feed the mixture.

Concrete mortar is prepared at the factory in compliance with a specific recipe. For different methods involving pouring into water, the concrete grade should be 10-20% higher than if laying were carried out under normal conditions; it is necessary to reduce the ratio of water to cement in the finished solution. Water slows down the hardening process, therefore the introduction of accelerators and plasticizers is desirable. Anti-erosion additives increase the erosion resistance of structures.

Special requirements apply to formwork. She must be:

1. not permeable to concrete mix, including at joints;
2. it is good to keep in shape, despite the pressure of water;
3. easy to install.

From the outside, the formwork is additionally reinforced with stone or sandbags.

Vertical Pipe Method

To fill in this way you will need:

• concrete pumps or other equipment providing a continuous supply of mortar;
• concrete pipes with a diameter of 200-300 mm, consisting of links up to 1 m long, equipped with quick-release locks;
• rigging of the site over the place of concreting: traverse, winch, lifting mechanism.

The pipe is installed vertically, in contact with the lower point of concreting, with a slight gap between the bottom and the edge of the pipe. A floating wad is placed inside, for example, burlap or a wooden cork, which is subsequently pressed through with liquid concrete and displaces water and air. In more technologically advanced versions, the ends of the pipe are equipped with valves that open after the entire pipe is filled with concrete. The solution is fed through a funnel until the layer of laid concrete reaches a height of 0.8-1.5 m from the lower edge of the pipe.

After that, the pipe is lifted by one link, the upper element is dismantled, and the lower end must remain in concrete. Filling continues to the required volume. It is worth noting that with the help of one pipe it is possible to fill an element with a radius of 6 m, therefore, if the concreting area is larger, a system of concrete pipes with a step of 10-11 m should be used.

How to pour concrete in an ascending solution (VR) way

The method involves pre-filling the concrete object with stone or gravel so that the voids account for 45% of the volume. Concrete mortar is supplied through pipes of small diameter 37-100 mm, which, rising up, naturally fills the voids in the dump, completely displacing the water. The area that can be poured with a single pipe is determined by the radius of the mixture: R \u003d 3 m when the solution is fed into a stone sketch, 2 m into a crushed stone dump. Two filling methods are used: pressure and non-pressure.

Pressure or injection method BP

Pipes are installed directly in the stone or gravel. Cement mortar under pressure flows to the base of the outline, then rises, providing a monolithic setting with aggregate. Pipes after completion of work remain in the concreted block, the excess is cut off.

Gravity or gravity method

It is realized by means of a device in a stone backfill of a mine, the walls of which are a permeable lattice. The pipe moves inside this shaft, which makes this method similar to the VPT method. Concrete mortar spreads under its own weight, the pipe links are alternately dismantled.

Concrete laying at shallow depths

The described methods have become widespread in the formation of concrete structures at a considerable depth, up to 50 m. Is it possible to pour concrete using simpler and less expensive methods, if the depth does not exceed 2 m, and the work itself is aimed at repairing existing monolithic structures? Indeed, to restore the integrity of the damaged structure, leveling the bottom or pouring a non-responsible object, there is a method of laying concrete in bags.

Bags filled with fresh mortar and sewn up are placed on the base or embedded in large caverns of damaged structures. Burlap allows water to pass through but prevents concrete from spreading. When concreting a large space, the bags are stitched together and reinforced.

Another method of underwater concreting at a depth of 1.5-2 m is the island or ramming method. The method requires a high feed rate of cement mortar and the use of a vibrator for ramming the next portion of concrete, however, it allows concreting non-horizontal surfaces (for example, shores). In addition, no reinforcement is required and there are no high requirements for concrete class.

When pouring concrete into water, it must be remembered that this is a technologically complex process that requires careful preparation, preparation of design documentation and compliance with construction standards. Exact adherence to the laying technology will allow avoiding emergencies both in the process of underwater concreting and during subsequent operation of the facilities.