Can concrete be poured into water. Will concrete harden in water? Pouring cement into groundwater

Can concrete be poured into water? Of course. Under the water concrete works produced in two ways: where the water depth is shallow and there is little excitement or no tides, the immersion of the solution through a funnel is done into spaces that are fenced off by bridges, or into the water directly; on the contrary, where there is strong waves and the water is deep, 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 should be removed, sheet pile rows are driven in and concrete is poured between them through a funnel. If the base is loose under the mortar and, for example, consists of a thrown stone, then to avoid seepage of the mortar into the crushed stone, with which the stone base is chipped, it is necessary to thoroughly split the surface of the base in advance and cover it with a canvas with the edges raised upward.

Having prepared the concrete, it is necessary to leave it to rest for a while, covering it with a tarp in case of sun or rain; this is necessary in order for the concrete to set a little, 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 immersed the already semi-hardened concrete mass in water in order to avoid high costs for the device to prevent the submerged solution from washing out with water before its mass had time to harden. To protect the outer surfaces of freshly poured mortar from the shock of waves and the pressure of flowing water, Kinipple covers these surfaces with a thick canvas. The core of the structure is usually made from an unsaturated solution, and the outer shell, one m thick, from a saturated one:

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

The time between stirring the solution and immersion in water must be commensurate with the properties of the solution used, which hardens quickly or slowly. It is necessary to calculate this time so that during immersion, on the one hand, part of the cement is not lost from erosion by water, and on the other hand, the concrete does not harden so much that it would lose the opportunity to bond 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 before it sinks. To compact the submerged concrete, a rammer is used, the top of which (located above the surface of the water) protrudes to receive the blows of the rammer. The compaction itself must be done carefully so that there is not a large shock of the movement of the water and the entire mass, which can contribute to the erosion of the concrete.

The mortar for this kind of concrete is obtained from 1 part of cement and 2.5 parts of clean sand.

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Second fill method

Along the strip where it is supposed to build some structure, for example a dam, two ditches are dug along the bottom with the help of dredging machines; into these ditches directly into the water in the form of two shafts, which are brought to the level low waters, semi-hardened concrete is poured. Depending on the state of the sea and the properties of the cement used for removing these shafts, the free concrete mass is immersed or lowered in coolers, since experience shows that such coolies are perfectly combined into one whole and form a single monolith. When the casting of concrete for the formation of shafts is completed, iron piles are hammered under a slope, which the slopes of the structure will have. To connect the piles to each other, iron rods with eyelets are put on. To keep the piles in the same inclined position, steel cables are put on their tops, which are fixed to dead anchors.

Boards, which are covered with a canvas on the inside of the structure in order to prevent the washing out of concrete by waves, are laid on the inside of the piles. Along the length of the structure, partitions are made of concrete massifs, which, with the help of submerged concrete that have already begun to set, are inseparably connected with the lower layers, forming a monolith; this is confirmed by many recent experiments, even with very lightly saturated concrete. From these experiments it turns out that in order to save costs, you can also use low-saturated concrete, observing only that its component parts mix well with each other, and there is no excess water, and also that it is possible to immerse the concrete mass without harm to the strength of the structure through a certain time after the setting process has begun. In case of strong waves and great depths, concrete work, as mentioned at the beginning, is carried out inside the caissons.

Usually, when the soil under the base is prepared, partitions with a thickness of 1 to 1.2 m are built around the entire chamber, to the roof from the very bottom, and their walls are made of boards that are placed vertically and after the concrete has hardened, they are taken away. The concrete under the very ceiling is hammered with a flat rammer. It is useful when filling concrete to lay it in layers and not lay the next one until the one laid before has hardened, which will take about 5 or 6 hours of time. The lowering of the concrete is done using special pipes with valves at the bottom and top.

Water is an important ingredient for cooking mortars for the construction of structures and finishing. It is no secret that not any liquid is suitable for mixing cement, but one that meets certain requirements. We will tell you what water should be for concrete and mortar and why you cannot use liquid from any faucet.

Source selection problem

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

The effect of water on the grade of concrete 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 quantity can reduce the rate of hardening, the final strength, and prevent the formation of molecular bonds in the structure of the stone.
2. Organic contaminants (silt, moldy fungi) harm concrete in fact and in the long term: they prevent mineral components from reacting and crystallizing qualitatively, over time, in a humid environment, organic matter develops and destroys the product throughout the entire volume.

Accordingly, you can only use water that meets state standards, that is, from water pipes, but laboratory-tested: unfortunately, a really good liquid rarely reaches the consumer due to the poor condition of the wire mains. The same applies to the flushing of aggregates and the watering of young, hardening concrete.

Standard

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

GOST describes in detail what kind of water is 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 ​​from tab. No. 3. If they match, water is used to mix concrete and cement-based products.

The influence of chemical compounds on the quality of concrete

There is a lot of water in concrete - from 155 liters per 1 m 3, depending on the fraction of crushed stone, sand, the expected brand of stone. The liquid interacts with each grain of sand and dust of cement, therefore, its quality affects the entire volume of the future structure. How chemical compounds in water affect the properties of concrete, if we neglect the established standards of GOST?

• Sugars and phenols delay concrete hardening and greatly impair 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 additives-improvers, they only slow down the hardening;
• Soluble salts of sulfate ions and chlorine ions crystallize in the pores of concrete, leading to corrosion of stone and reinforcement. For this reason, it is strictly forbidden to use water from the sea.

Waste, swamp and river waters can be used for mixing concretes and cements, but only after cleaning and checking by a sanitary-epidemiological station.

Amount of water

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

What determines the consumption of water in concrete:

• Fraction of sand and gravel;
• Cement grade and type;
• Expected grade of concrete.

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

Too little water content of the concrete solution will not allow mixing the components properly, and this will have minimal plasticity.

To obtain concrete with good plasticity and workability, use special plasticizers!

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

Work options

They can be done in two ways:

• at a shallow depth, where there are no tides, and there are minor waves, the solution is lowered through the funnel into the cavities, fenced with special bridges, or concrete is poured into the water;
• at a rather impressive depth, in places where waves can be very strong, caissons become a reliable assistant in concreting work. The concrete mass is transferred to such caissons through shafts 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 mortars? Let's take a closer look at this process.

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, rows of piles are hammered (sheet piles are used). This makes it possible to avoid drainage works.
2. Then concrete is thrown between them through a funnel.

Advice: if the base under the concrete mortar is not dense enough, for example, from thrown stones. In this case, it must first be chipped tightly, and then covered with a cloth, the edges of which will be bent upwards. Thanks to such measures, the solution will not be able to seep into the crushed stone, and the concreting will be much better.

Preparing concrete

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

If the solution is kept for the prescribed period, then it will reach the required consistency for immersion in water: it will set a little and will not be very washed out in water. This method of preparation of the solution was first used by Kinipple, an engineer from the UK.

In this way, he managed to avoid extra costs for the device of a system that allows you to protect the concrete solution from erosion. Kinipple dipped a solution under the water, which was already half-hardened.

In addition, the engineer provided technology for its protection from the force of waves and underwater currents. For this, he covered the outside concrete surface dense linen cloth(canvas).

Tip: for the core of such a structure, use an unsaturated solution, while the outer part requires a saturated one, 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 stirring it and moving it into the water. It is important to calculate the most optimal time so that the concrete does not erode too much during immersion. Otherwise, some of the cement will be lost, which will negatively affect the quality of the structure.

1. It is also important to make sure that the concrete mass does not become too hard, because in this case it will not bind tightly with the mortar that was immersed earlier and will not become monolithic. In those underwater areas that are subject to powerful shock waves, strong currents, before lowering the concrete into the water, add a small portion of the fast-setting cement.

1. Among other things, dipped in water. To ensure this, it is rammed. The top of the rammer is above the water level, taking the impact of the ramming tool. Remember that tamping must be done very carefully, because if you overdo it, too much vibration and waves will inevitably erode the concrete.

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

Advice: to the question - does concrete let water pass, you can answer - it depends on the composition, so you can use it to build water tanks.

Method number 2

1. Near the site where it is planned to build the necessary concrete structure, for example, a dam, with the help of dredgers, it is necessary to dig two ditches at the bottom. Semi-hardened concrete should be poured into them, 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 swamps. This idea is not accidental, their value lies in the fact that in the process they are able to form a monolith. After casting the cement for the shafts, the iron piles are driven in. Do it at an angle to create 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 on top, which you attach to the dead anchors.

Advice: so that during strong waves the concrete does not wash out, on inside piles, lay boards covered with canvas.

1. Install concrete partitions along the entire length of the building. The material for them should already be at the stage when it begins to dry out and harden. This will make it possible 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 lightly saturated concrete, it is important to know that its constituent parts must mix very well and form a homogeneous mass. In addition, be aware that if there is a lot of water in the concrete, its "adhesion" will be greatly impaired.

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

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

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

One takes 5-6 hours to harden. The concrete solution is lowered through special pipes, which are equipped with valves at the top and bottom.

Pipe

In underwater concreting, very important device is the pipe. By opening the top valve, you ensure that some of the concrete enters it, after which it should be closed.

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

Advice: if you do not know how much water per cube of concrete you need to spend, take average- 125 l.

After that, 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, simply pouring them from above. On the this moment the maximum depth of underwater concreting works is no more than 30 m.

Conclusion

Concreting in water - 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 described two methods of pouring - using piles and concrete shafts (ascending mortar).

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

Builders working at hydrogeological stations are often faced with the need to fill directly under water.

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

Drainage in such conditions is impossible. Such construction works can be classified as particularly complex. For concreting in water to be successful, decay must be excluded cement mix... Everyone knows that cement mortar includes a certain amount of water, but it should be exactly the same as when laying in normal conditions... No more, no less. If there is too much water, the solution will lose its strength, the construction simply will not be completed. Therefore, the whole difficulty of the work will be to prevent the ingress of water on the building material until it is fully adhered.

Typically, pouring in water is done in two ways: the ascending solution method and the ascending pipe method. The essence of these methods lies in the fact that around the solution, until it is completely solidified, it is enclosed closed space... No water ingress is possible. Whichever method is used, the work will be very hard. It is very difficult for one person to cope with it; at least two more assistants are needed.

Rising pipe method

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

To work, you need the following:

• mixture;
• pile platform;
• winch;
• pipe;
• hopper;
• traverse.

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

The scheme of concreting under water using the ascending mortar method: 1 - stone-crushed stone filling; 2 - solution; 3 - sheet pile formwork; 4 - fence; 5 - flooring; 6 - mine; 7 - pipe; 8 - winch; 9 - sleeve; 10 - mortar pump.

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

So, level by level, pouring under the reins takes place. Upper layer each level is considered the most unreliable because water can get there. Before filling a new layer, it is removed. If a large space is required to be concreted, then one pipe will not be enough. Then several pipes with a large diameter are used.

Ascending solution method

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 will need the following materials:

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

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

Free-flow filling. All work is done in the mine. There is a construction site in the center of the mine. A seamless pipe is placed around it. Under the action of the pressure of the pipe, concrete enters it and spreads as needed. Additional delivery head is not applied.

Filling with pressure. 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

Underwater concreting is a special technology for laying concrete mortar, used when it is not possible to pump out water or remove it in other ways. Most often, the method is in demand when building large iron concrete structures, the operation of which involves significant loads. Bridges, dams, other hydraulic structures, as well as power line supports, wells in rock are structures, during the construction of which, in many cases, they resort to underwater concreting.

Water concreting is also used in smaller projects. Inability to establish drainage from the pit when high level groundwater is a common situation during construction work.

There are several methods for pouring concrete into water:

• vertically moving tube (VTP) technology;
• BP or concreting, thanks to the ascent of the solution;
• ramming concrete mix;
• placing concrete with bunkers;
• bagging method.

The main thing to remember when performing concrete-laying work is that the main calculated mass of the solution should not come into contact with water in order to avoid washing out of the cement; the concreting process must go on continuously until the level specified by the project is reached.

Preparatory work

Before proceeding with the placement of concrete directly into the water, you need to draw up a project describing the procedure and progress of work, the amount of material, necessary equipment and rigging. As a rule, at considerable depths, divers are required, who outline a plan for clearing the area to be concreted or clean it manually, install the formwork, regulate the placement of pipes and hoses through which the grouting mixture flows.

Concrete mortar prepared at the plant in accordance with a certain recipe. For different techniques assuming pouring into water, the grade of concrete should be 10-20% higher than if the laying was carried out under normal conditions; in this case, it is necessary to reduce the ratio of water and cement in the finished solution. Water slows down the hardening process, therefore, it is desirable to introduce accelerators and plasticizers. Anti-erosion additives increase the resistance of structures to erosion.

Formwork also has special requirements. She must be:

1. impermeable to concrete mix, including at joints;
2. keep its shape well, despite the pressure of the water;
3. easy to install.

WITH outside the formwork is additionally reinforced with stone or sandbags.

Vertically movable pipe method

To fill in this way, you will need:

• concrete pumps or other equipment that provides 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;
• equipment of the platform above the place of concreting: traverse, winch, lifting mechanism.

The pipe is installed vertically, in contact with the lower point of concreting, while a small gap is allowed between the bottom and the edge of the pipe. A floating wad is placed inside, for example, burlap or wooden cork, which is subsequently pushed through by liquid concrete and displaces water and air. In more technologically advanced versions, the pipe ends are equipped with valves that open after the entire pipe is filled with concrete. The mortar 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 raised by one link, dismantled top element and the lower end must remain in the concrete. Pouring continues to the required volume. It should be noted that with the help of one pipe it is possible to pour 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 using the ascending mortar (BP) method

The method involves the preliminary filling of the object to be concreted with stone or crushed stone so that the voids make up 45% of the volume. A concrete solution is fed through pipes of small diameter 37-100 mm, which, rising upwards, naturally fills the voids in the backfill, completely displacing water. The area that can be poured with one pipe is determined by the radius of distribution of the mixture: R = 3 m when feeding the solution into the outline from the stone, 2 m - into the crushed stone fill. There are two methods of pouring: pressure and non-pressure.

Pressure or injection BP method

The pipes are installed directly into the rock or crushed stone fill. The cement slurry flows under pressure to the base of the sketch, then rises, ensuring monolithic adhesion with the aggregate. Pipes after completion of work remain in the concrete block, the excess is cut off.

Gravity or gravity method

It is realized with the help of a device in the 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. The concrete solution spreads under its own weight, the pipe links are removed one by one.

Shallow concrete placement

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, there is a method of placing concrete in bags to restore the integrity of a damaged structure, leveling the bottom or pouring a non-critical object.

Bags filled with fresh mortar and sewn up are placed on the base or sealed in large cavities of damaged structures. Burlap allows water to pass through, but prevents concrete from spreading. When concreting large space bags are sewn 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 cement mortar and the use of a vibrator for ramming the next batch of concrete, however, allows concreting of non-horizontal surfaces (for example, banks). In addition, no reinforcement is required and there are no high requirements for the class of concrete.

When pouring concrete into water, it must be remembered that this is a technologically complex process that requires careful preparation compiling project documentation and compliance with building codes. Accurate adherence to the laying technology will allow avoiding accidents both during the underwater concreting process and during the subsequent operation of the facilities.