Waterproof concrete w4 - properties and application. brand

As a building material, concrete has many advantages and useful qualities, thanks to which it received its wide distribution. One of them is water resistance, which is understood as the ability not to pass moisture under pressure of a certain size. In this article, we consider the types of concrete that can withstand moisture.

Methods for determining

According to GOST 12730.5-84 there are several methods that allow determining the permeability of concrete W:

Since the first two methods are fairly time consuming (for example, W8 concrete using the “wet spot” method will have to be checked a week), the last two options are most often used in practice.

Brand of concrete for water resistance

GOST 26633 implies 10 concrete grades depending on the degree of their water resistance (W2, W4, ... W18, W20).

The instructions for determining each brand are as follows:

• a concrete sample cylinder O150 mm is taken;
• it is supplied with water under pressure;
• make observation and measurements.

Each of the brands must withstand a certain pressure. For example, concrete W6 should be resistant to pressure up to 6 atmospheres (0.6 MPa), and W4 - 0.4 MPa.

Considering the characteristics of concrete W4, it can be noted:

• low production cost;
• with age, its water resistance increases, in particular, concrete B15 F150 W4 showed a 6-fold increase during the year;
• material thickness of 200 mm is ideal for creating waterproofing, which allowed him to become a leader in civil engineering;
• When B75 F75 W4 is added to expanding cements or sealing components, the water tightness can be increased without losing the main characteristics of the material.

To assess the permeability of concrete products can be used:

• direct methods (water tightness or filtration coefficient);
• indirect (water / cement ratio and water absorption).

The effect of material age

An interesting fact is that with increasing age of concrete, its waterproof qualities only increase. However, a significant and intensive increase in such indicators seems possible only with special care for it (constant moistening).

An example is concrete made with Portland cement. If it is constantly moisturized or a positive temperature is reached, at which moisture will not evaporate, its water resistance will rapidly increase over the course of six months. This will significantly increase the overall life.

Tip: concretes that freeze at constant moistening and compliance with the required temperature, have a water resistance index several times higher than concretes, the solidification process of which was carried out in an environment with low relative humidity or was accompanied by significant moisture loss.

For example, if you take a material, which solidification after stripping took place with constant moistening throughout the month, and compared with that which after solidifying was hardened in conditions of insufficient humidity (at the level of 50-60%), the latter will need about six months to achieve watertightness indicators first.

From this we can conclude that the concrete will most quickly become water resistant if it hardens in conditions of sufficient humidity.

At the same time, even if watering is rare or completely absent, and the relative humidity of the environment will approach the 100% mark, the waterproof qualities will also increase in the first six months or a year, then their indicator will stabilize. When moisture evaporates from concrete or it hardens in conditions of insufficient relative humidity, the growth of water resistance decreases.

In situations where the base is eaten, it will lose a huge amount of moisture, the process may stop altogether or go in the opposite direction. This may lead to the fact that after a certain time, the water resistance of the concrete will be lower than the original.

Tip: the characteristics of W8 concrete fully meet the objectives for the construction of a conventional foundation, but only with waterproofing works.

Ways to improve water resistance

Since concrete has a capillary-porous structure, under the influence of a certain value of water, it is permeable to it. Many factors influence this indicator, incl. nature and degree of porosity. The connection thus turns out to be such - with an increase in porosity, water permeability decreases, and vice versa, the more dense the material, the higher this index will be.

Tip: concrete B25 W4 F75 has a frost resistance of 75 cycles.

Pores can occur in the material due to a variety of reasons, the main of which are:

• weak compaction;
• excess mixing water;
• shrinkage of concrete, which occurs after its drying and is characterized by a decrease in volume.

To achieve the desired effect, the concrete must be well mixed and compacted with a vibrator. It is worth remembering that the process of joining water to cement is called hydration and it can last for a long time.

For full hydration it is necessary to strictly observe the proportions - for every 10 kg of cement 4 liters of water should be used. However, only slightly more than half (60%) of this water directly react with cement.

Conclusion

Each type of concrete has its own characteristics, especially waterproof. When developing a construction plan, this parameter must be taken into account. The article described in detail what waterproofing is and how it is checked.

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