Water-tight concrete: a method of measurement and methods

What is impermeability to water - I think, no need to explain. We have to figure out what, for example, is the water resistance of W8 concrete and how it is calculated. In addition, for obvious reasons, we are interested in methods for improving water resistance, both at the preparation stage of the mortar and in the finished structure.

What it is

First, let's clearly state the meaning of the term. Yes, it is intuitive; however, it is better to be sure that your intuition was not mistaken in the wording.

Definition: waterproofing is the ability to not pass water under excessive pressure.

Measurement

Слово «определение» в русском языке многозначно: под ним понимается как точная формулировка, так и способ измерения того или иного параметра.

Способы, которыми выполняется определение водонепроницаемости бетона, описываются отечественным стандартом ГОСТ 12730-5-84. Документ предлагает испытание бетона на водонепроницаемость методами «по мокрому пятну» и «по коэффициенту фильтрации». На практике чаще используется первый способ - просто потому, что он требует гораздо меньших временных затрат.

Прибор для определения водонепроницаемости бетона должен представлять собой устройство с как минимум шестью гнездами для крепления образцов фиксированного размера, позволяющее подвести к их нижней поверхности воду и ступенчато повысить ее давление. Образцы - цилиндрические, диаметром 150 mm и высотой 30, 50, 100 и 150 millimeters.

Instructions on the test procedure is also contained in GOST.

1. Acquired strength samples are maintained in the laboratory during the day. The goal is to equalize their humidity with atmospheric.
2. They are then installed in the gauge sockets and securely fixed there.. The diameter of the open end surfaces must be at least 130 mm.
3. Water is supplied to the bottom surface of concrete samples.. Its pressure increases in increments of 0.2 MPa. The test pressure change is smooth, it takes up to 5 minutes. The test time at each pressure stage is different for each thickness.

For each sample, the signal to stop the test is the appearance of a wet spot or water droplets on its surface.

Wherein:

• The water resistance of the sample is evaluated by the pressure at which its surface remained dry.
• For a group of six samples, the result is estimated by the pressure of water, at which moisture on four of them has not yet manifested from above.

How is a brand determined by test results? According to the following table:

Influence

How important is water resistance for concrete structures located above the groundwater level and not related to hydraulic engineering? Why, for example, is this property a concrete basement of a residential building?

High water permeability means that a certain amount of moisture falling out in the form of precipitation will be kept inside the base material.

Practical consequences are rather unpleasant:

• The fall of the insulating ability of the structure. The thermal conductivity of wet concrete is much higher than dry.
• The appearance of mold and moss, accelerating the destruction of the material.

When the temperature of the structure drops below zero, the situation is aggravated by the crystallization of water. Ice is known to have a larger volume compared to water; during crystallization, the pores of the concrete will expand, and the entire structure will collapse at an accelerated pace.

Conclusion: the water resistance of any material is linearly related to its frost resistance.

Increased water tightness

So, how to change the relevant properties of concrete? We analyze solutions for the preparation of concrete and for the processing of finished structures.

Cooking

Probably the most common solution is the modification of concrete with sodium liquid glass. Mass fraction of liquid glass is about 5%; since the price of the material is low (in bulk from 30-40 rubles / kilogram), an increase in the water resistance of the structure will not hit the construction budget.

The downside of using this modifier is a significant decrease in the solution lifetime. It has to be used within half an hour after the introduction of the additive, which is not always convenient.

Fortunately, deprived of this disadvantage, concrete additives for waterproofing can be easily found in hardware stores.

Let's get acquainted with a few sentences.

• Penetron Admix increases the water resistance of the material to mark B20. Not only that: it significantly increases the mechanical compressive strength of concrete and rather effectively protects it from the negative effects of aggressive media.

• Bisil And - жидкая добавка, снижающая пористость на стадии приготовления. Brand of concrete повышается до AT 12; добавка может применяться как для приготовления собственно конструкционных материалов, так и для изготовления защитных штукатурных растворов, заделки швов и т.д.
• Hydrohyte Additive - сухая смесь, содержащая цемент и, по словам производителя, «специальные химические компоненты». Опять-таки предназначена для увеличения влагостойкости растворов.

It is more than simple to prepare waterproof concrete with your own hands with this material: it is enough to mix Hydrohit with water in a 1.5: 1 ratio, mix thoroughly and pour into concrete. The additive must be present in the solution in the amount of 1% by weight of cement; if its exact value is not known, 4 kilograms of dry mix is ​​added to a cubic meter of concrete.

Processing of finished structures

How to make concrete waterproof after it gained strength?

A cheap solution in this case will be sodium liquid glass. It is diluted with water in a ratio of 1: 1 and is used for priming the surface.

However: the depth of penetration of such a soil is limited to only a few millimeters.

A somewhat more effective solution is silicone water repellents. They fill the pores with resins already at a depth of 10 centimeters, completely blocking the access of water from the surface into the structure.

Finally, for penetrating waterproofing materials Penetron and their numerous analogs, the depth of penetration is up to a meter. Their distinctive feature is that the lime contained in the concrete itself is used to block the pores: when wetted, the mixture of Penetron and calcium salts forms moisture-resistant crystals.

Treatment

What and how to handle waterproof concrete?

In general, an ordinary punch or abrasive wheel will perform its functions in this case as well. However, diamond tools are more preferable. So, cutting of reinforced concrete with diamond circles is much faster than conventional abrasive ones, and does not require replacement of the circle when the reinforcement passes.

Diamond drilling holes in concrete, in contrast to the traditional Pobedite drills and crowns, does not leave chips.

Conclusion

Надеемся, что предложенная информация окажется полезной читателю (см.также статью «Brand of concrete по водонепроницаемости: характеристики и область применения»).

Additional materials on how frost resistance and water resistance of concrete can be improved can be found in the video in this article. Successes!