- What is a hydroseal
- Selection and purchase issues
- How does the composition work
- Sealing gaps and cold joints in a monolith
- Sealing joints and tool joints
- Liquidation of pressure leaks
One of the best ways to seal leaks in concrete walls or a well is with a water seal, which is fairly cheap and easy to use. Not only in dilapidated concrete structures one has to deal with leaks, this is also true for new buildings, where the technology of pouring or assembling reinforced concrete structures was violated.
What is a hydroseal
There are two ways in which moisture penetrates through capital structures such as masonry and concrete. One of them is capillary migration, which occurs as a consequence of the material’s ability to absorb water. This natural defect can be corrected by blocking the labyrinth of pores and microcracks, that is, simply filling all internal cavities. Methods of penetration and injection waterproofing perfectly cope with such tasks..
Today we will consider another, more specific path for moisture through the enclosing structures – through leaks. The bottom line: a seemingly monolithic structure has a gap or fistula through which water flows freely under pressure. The throughput of this channel can be completely different: from a crack through which drops appear to a crack from which water gushes under pressure.
The main means for eliminating defects of the second kind are seals. It is a special plastic filler that demonstrates excellent adhesion to concrete and stone, high hydrophobicity, and very fast setting time. Hydro-seals can be used both for emergency repairs and as a preventive measure – for processing structures in which gaps appear as a specific deficiency in production or construction technology. A classic example of the latter is the treatment of seams in precast concrete structures, as well as monolithic concrete barriers, in which so-called cold seams are present..
Selection and purchase issues
Hydro-seals are in high demand, which has resulted in an extensive list of brands and types of mixtures. Taking this opportunity, handicraft manufacturers attribute absolutely fantastic qualities to the already effective means, but today there will be no talk of this kind of “herbalife”. It will be about the materials recommended by professional craftsmen in the realities of Russian construction.
Henkel traditionally holds the palm in this regard with Ceresit CX 1. The composition has one of the highest setting rates, and does not contain chlorides and aggressive compounds that can damage steel reinforcement. Moreover, this seal has successfully passed the test for contact with drinking water, that is, the product can be used to waterproof wells and storage tanks.
When eliminating leaks in septic tanks, technical tanks and foundations, agents from the middle price category, known under such names as “Aquatron”, “Penetron” or “Peneplag”, can be used. Nothing negative can be said about these seals: in their total mass, they correspond to the declared characteristics. But we repeat: with such tasks as blocking cracks, seams between reinforced concrete products or places of technological passages, the budget line copes quite well, the main thing is to correctly determine the degree of moisture saturation and the pressure of the surrounding waters.
In order not to break the promises of silence about counterfeits and low-quality products, we will give only a few tips on how to avoid an unequivocally unprofitable purchase:
- Do not consider mixtures for which such characteristics as water permeability grade, range of base material, setting time, bond strength, operating temperature range, and others are not declared.
- Do not purchase goods that do not have a specified production time, or in manual packaging.
- Do not expect that a more or less high-quality hydraulic seal will cost less than 200-250 rubles. per kg.
- If the manufacturer of the mixture is not verified by personal experience, first purchase a trial portion and test the product in real conditions.
How does the composition work
According to the principle of its action, the hydro-seal is a fast-setting cement-based composition with the addition of a wide range of modifiers and plasticizers. The method of curing the mixture is hydration, and the process is accelerated by a high concentration of active compounds. In other words, the tighter the contact of the mixture with the liquid, the faster the curing process proceeds..
The hardness of the seal increases abruptly, after 40–300 seconds from the moment the dry mixture is mixed with water. In this aspect of use, it is very important to read the instructions: the compositions have a different dependence of the curing time on the degree of initial wetting. The curing speed should always be selected individually, depending on the size of the hole and the complexity of its shape..
The course of chemical reactions in the composition of the seal is possible only if certain conditions are met, in particular the temperature regime of use is important. Some types of fillings are designed for use at low, but not negative temperatures – from +2 to +5 ° C. However, it should be remembered that in such conditions the curing rate inevitably decreases and this should be taken into account when planning the work technology, for example, to develop methods for holding the filling until it is completely cured..
A characteristic feature of hydraulic seals is considered to be zero shrinkage, and for the highest quality compositions – a moderate and normalized increase in volume. It is also important that the plug material does not form a breeding ground for algae and microorganisms, which cannot be said about natural materials. Additionally, we note that the application of this method of waterproofing does not require additional equipment and professional qualifications, it is enough to understand the principle of operation and apply it correctly depending on the conditions of use..
Sealing gaps and cold joints in a monolith
There are three categories of through holes in structures, which differ not only in size and characteristics of genesis, but also in the period of operation of a building or technological structure. Fistulas and cracks can be either one of the processing stages, or a component of the installation and construction process, and they can also occur in an emergency.
You don’t have to go far for an example: provided that a hydraulic seal is used, it is allowed to pour concrete products in portions with a time interval of more than 8-12 hours, depending on the grade of concrete. In technological manuals for the manufacture of concrete products, this method does not provide the proper waterproofing qualities, which can be compensated for by the elimination of cold seams after solidification of the reinforced concrete mass..
How is this done? Of the necessary requirements, one can single out the provision of access to both surfaces of the enclosing structure. That is, almost all NZLF projects are suitable for the use of hydraulic seals, which makes the requirement for one-stage filling not so strict with relatively small additional investments. However, it is important that the requirement for water resistance and frost resistance of the bulk of concrete is observed, otherwise the use of a hydraulic seal will do nothing.
To install a hydraulic seal in a seam, it must first be cut. On both sides, a groove is cut in the concrete along the cold seam line. The groove should have edges beveled under a reverse taper (aka “dovetail”) at an angle of about 5 °. For the manufacture of such a profile, it is required to make three parallel cuts: two beveled extreme ones, forming the edges, and also the third, designed to remove material from the groove. The further technique is clear: according to the instructions, the mixture is diluted to a consistency that has a curing time of 200–250 seconds, after which the filling material is tightly hammered into the groove, the protruding excess is scraped off to align the seal flush with the main surface.
Sealing joints and tool joints
In precast concrete structures, a slightly different sequence of use is required. The main difficulty is that the absence of a monolithic connection between structural elements causes the risk of movement and displacement. Another feature is the high length and depth of the seams, while the seal can only be prepared in small portions, based on the hardening time.
Seam sealing in precast concrete and reinforced concrete structures is facilitated by the possibility of preliminary preparation. Blocks, rings and other products can be processed before they are assembled – it is elementary to chamfer edges 15–20 mm wide. When installing blocks, the most preferred way to immobilize them is to lay two or three reinforcing pins driven into pre-drilled and cleaned holes. Additionally, a groove can be cut exactly in the center for laying a bentonite cord: it will not eliminate capillary leaks, but it will almost guaranteed to cope with pressure leaks.
Otherwise, the use of a hydraulic seal in such cases is in many ways similar to filling cracks in a concrete monolith. We have a groove with a triangular cross-section, which is quickly sealed with a filling in sections of 30–40 cm, while the composition is prepared thicker, with the expectation of curing in 60–90 seconds. Beforehand, do not miss the opportunity to thoroughly wash the joints from concrete dust, at the same time moistening them well. When applying hydro-seals, small protrusions remain at the joints, which do not clean off, just as they are applied, they are slightly stretched in both directions from the joint, which achieves a better adhesion. It should also be remembered that if wells or storage tanks are treated with a hydraulic seal, the composition must be designed for use in contact with drinking water.
Liquidation of pressure leaks
If water flows from a gap in a concrete fence under pressure, this defect is eliminated, respectively, with a pressure seal. It will not be superfluous to at least pre-calculate the height of the water column and determine the pressure at the leak. Modern seals confidently cope with water flow up to 5-8 atm.
As a rule, water does not flow along the entire length of the crack, but only in the place where the through fistula has formed. It is necessary to widen the hole, otherwise working with a rigid plastic compound will not be comfortable enough. Expansion is carried out by drilling to a diameter of 30–35 mm, the tool is protected by a mudguard membrane. If there is access to the back of the container wall, the hole can be temporarily closed with a piece of plastic wrap.
The filling is prepared after drilling, because it is impossible to predict how long it will take to expand the hole. The composition is mixed to the consistency of plasticine, with the expectation of hardening within 30-40 seconds. A cone is formed from the wetted mixture, having a diameter in its wide part that is twice the width of the hole. The resulting plug is forcefully driven into the channel, which can be done even when water flows under pressure, and then tamped tightly into the hole until the plasticity decreases too much.
After that, it is necessary to stabilize the seal – press it with a flat solid object to the concrete surface and hold it for about 20-30 seconds. Elimination of pressure leaks requires a certain skill, at the same time, the technology does not prohibit expanding the hole again and repeating the filling operation.