EP0111306B1 - Method of drying and protecting masonry against reocurring dampness - Google Patents

Abstract

1. Method for drying and protection of masonry from recurring dampness, in which the drying process is carried out by means of an electromotive apparatus and the seal is formed by means of a hydrophobic medium introduced into holes bored at an angle to the ground surface, characterized in that the upper row of electrodes is set into the masonry spaced from the negative electrodes by up 1 metre, and preferably in the neighbourhood of the earth surface, and in order to achieve even drying the spacing between the positive electrodes in a row is determined depending on the size of the dampened area and the electrodes are divided into groups which are supplied from separate sources, in that the holes for the hydrophobic medium are bored outside the zone of influence of the electrical field above the upper row of electrodes, and in that the hydrophobic medium is continuously introduced into these holes during the flow of current which, following the principal of continuity of current as well as capilliary and gravitational transport and convenyance, penetrates into the capilliaries and pores where it spreads out, where the electrokinetically downwardly-transported water is removed, so that a seal against dampness is formed.

Description

The invention relates to a method for drying and protecting masonry from re-moistening by capillary water drawing from the substrate.

Methods for drying masonry by electro-osmosis or impregnation of the masonry with various chemical agents to be introduced by gravitation or under pressure are known. The chemical agents introduced into the masonry by gravity or under pressure do not penetrate sufficiently into the water-filled pores and capillaries.

A process is known from PL-PS No. 103 633 which enables this goal to be achieved. In this process, the water is transported downwards and the hydrophobic agent is transported upwards. The change in the direction of transport of the liquid medium takes place by changing the polarity of the voltage which is applied to the electrodes compared to the polarity which ensures a downward water transport during drying. The introduction of the hydrophobic agent into the masonry is based on the principle of drawing the water upwards, which is caused by electroosmotic negative pressure which is directed upwards, this direction resulting from the change in the polarity of the voltage.

However, this method has a slight increase in the penetration area of the hydrophobic agent compared to gravitational impregnation. This results from the following phenomena. The water removal from the affected area preceding the hydrophobization process is associated with the penetration of air into the capillaries freed from the water. In this way, because of the large expansion capacity of the air, the factors which cause the development of the negative pressure are deteriorated, which enable the masonry to be effectively impregnated with the hydrophobic agent. In the capillaries from which the water is completely removed or only enters the walls of the capillaries, the negative pressure disappears almost completely. In this position, the introduction of the hydrophobic agent and its distribution in the masonry mainly takes place according to the gravitational principle. In addition, the air penetration effect occurs in the capillaries with the smallest diameters, i.e. Air plugs which make it difficult or even impossible for the hydrophobic agent to penetrate. The result of these phenomena is an unevenly hydrophobized masonry area, which is not always sufficient to completely prevent repeated water pulling from the floor. If the direction of the voltage applied to the electrodes is changed in the process, water which has previously been brought down is drawn up again, which is intensified by the effect of the electroosmotic transport. As a result, from the level of the negative electrode, the level of occurrence of the increased humidification, which prevents the penetration of the hydrophobic agent by gravity, is increased. At the same time, due to the ingress of air into the capillaries, the penetration area of the hydrophobic agent is not increased significantly above the level determined by capillary application of this agent. The change in the voltage applied to the electrodes of the electroosmotic system, which takes place during the hydrophobization, which is preceded by the drying, thus increases the penetration area of the hydrophobic agent only insignificantly and does not ensure that the possible sizes of the completely hydrophobized areas are reached.

On the other hand, from the point of view of the aim of the method, which consists in achieving the highest possible degree of saturation with the hydrophobic agent in the region from the pouring level downwards, the reversal of the voltage applied to the electrodes of the electroosmotic system leads to a reduction in the hydrophobized region compared to the region which is penetrated by gravity in the previously electro-osmotically dried masonry by the hydrophobic agent. In addition, this method does not allow the masonry areas below the earth to be secured. This results from the fact that after reversing the direction of the voltage applied to the system in this area, the capillary undergoing, reinforced by the electroosmotic transport, proceeds faster than the process of gravitational penetration of the hydrophobic agent, which is weakened by the electroosmotic transport which is opposite to the direction of gravitational penetration. In practice it has been found that this process is characterized by a rapid decrease in the drying effectiveness during the first days after the system has been operated.

During the rest of the drying time, the electroosmotic flows remain at a much lower level than during the initial period. The cause is the rapid decrease in the current flowing in the masonry during this time. This decrease results from the rapidly occurring polarization processes.

The method also does not protect against the effects, which specialists in the field of architectural monuments care have, which can be caused by changing the salt concentration in the wall. These changes are related to the ion current during the current flow through the masonry, the ionic conductivity, as well as the electrolysis of the water. Regarding the slow salt enrichment with saline solutions that are absorbed from the soil, which is sometimes some tens or even lasts a hundred years, these changes are erratic and, due to the inflow of migrating ions and electrolytic water decomposition to hydrogen and oxygen, cause an increase in the salt content in the area of the masonry in which the current flows. The progressive crystallization of the salts is the cause of the frequent formation of hard-to-remove stains and seizures on the surfaces of electro-osmotically dried masonry, in the immediate vicinity of the electrodes.

The question of the growing proportion of salt is associated with an even more dangerous phenomenon than eating. It has been found that the salts exert a destructive influence on the hydrophobic film which covers the walls of the capillaries, as a result of which it is detached from the substrate and its structure is destroyed. It is believed that the hydrophobization process must be repeated after several ten years. It can be concluded that the resistance of the hydrophobic barrier decreases with the increase in the proportion of salt in the masonry.

If the plus electrodes are arranged above the holes for hydrophobization after the masonry has been impregnated with a hydrophobic agent, the current flow through the hydrophobized area and the drying process are practically interrupted.

The invention has for its object to increase the penetration of the hydrophobic agent into the masonry, to increase the uniformity of its distribution in the hydrophobization zone, to increase the resistance of the hydrophobic film on the walls of the pores and capillaries and the time it takes to dry and Shutting off the moisture related technological processes.

According to the invention, the upper row of the plus electrodes is used in the masonry at a distance of up to 1 m from the minus electrodes, preferably in the vicinity of the floor surface. To achieve uniform drying, the distances between the electrodes within a row are determined depending on the size of the moistened area and divided into sections, which are fed by separate sources. The holes for the hydrophobic agent are drilled outside the area of influence of the electric field of the upper row of electrodes. The hydrophobic agent is continuously introduced into these holes during the current flow, which penetrates into the capillaries and pores according to the effect of the continuity of the current and the capillary and gravitational promotion and transmission and spreads where the electrokinetically transported water has been removed, which creates a barrier to moisture.

• a) Erniedrigung des Wertes der Polarisationsspannung des Systems Elektrode-Mauerwerk von den in der Praxis vorkommenden Werten von 6 bis 10 V auf unter 4 V,
• b) Erniedrigung des Anfangswertes der Resistenz des Bereiches des Mauerwerks zwischen den Elektroden um etwa 50 ⁰J₀.

The transport of the liquids (water and hydrophobic agent) in the masonry realized in this way is caused by electrokinetic pressures, the values of which are sufficiently large in this case by forcing the current values in the following way:

• a) lowering the value of the polarization voltage of the electrode-masonry system from the values occurring in practice from 6 to 10 V to below 4 V,
• b) lowering the initial value of the resistance of the area of the masonry between the electrodes by approximately 50 ⁰ J ₀ .

This is achieved by reducing the size of the system involved in the electrokinetic transport process and by virtue of the excellent arrangement of the holes provided for pouring the hydrophobic liquid.

The initially considerable inhomogeneity of the current density in the masonry is compensated to a sufficient extent in the first working hours of the system (thanks to the polarization effects that occur most quickly on the lines of the highest current density values).

• Bei der gegebenen Erzwingung, ist der größte Wert dieses Stromes sein Anfangswert, der beim Einschalten der Speiseeinrichtungen auftritt. Während des Stromflusses in einer Richtung erfolgen in dem Mauerwerk elektrochemische Polarisationserscheinungen, deren Effekt die Entstehung einer durch externe Erzwingung geladenen Zelle in dem Mauerwerk ist, deren Spannungsrichtung der der äußeren Speisequellen entgegengesetzt ist. Die Polarisationsspannung wächst stets mit dem Stromfluß durch das Mauerwerk. Anfangs wächst sie sehr rasch; sie nähert sich dann asymptotisch dem festgelegten Wert, der bei typischen elektroosmotischen Anlagen ca. 6 V beträgt, häufig aber bis 10 V reicht.

The method ensures an increase in the effectiveness of drying by the fact that the current appears in the circuit when the compulsory DC voltage is switched on and the drying process begins, the effectiveness of which increases with the current value:

• Given the enforcement, the greatest value of this current is its initial value, which occurs when the feed devices are switched on. During the current flow in one direction, electrochemical polarization phenomena occur in the masonry, the effect of which is the formation of a cell in the masonry which is charged by external force and whose direction of voltage is opposite to that of the external supply sources. The polarization voltage always increases with the current flow through the masonry. In the beginning it grows very quickly; it then asymptotically approaches the specified value, which is approx. 6 V in typical electroosmotic systems, but often reaches up to 10 V.

Accordingly, the electrochemical reaction of the masonry to the current flowing through it, which consists in the electrical charging of the masonry, corresponds to the principle of "action-reaction", a reduction in the current flowing through this masonry, which is particularly visible in the initial period of drying.

Because no effective method for depolarization of the masonry encompassed by the effect of an electroosmotic system is known to date, the aim is to limit the specified value of the polarization voltage as much as possible. In the method according to the invention, this is achieved by reducing the expansion of the polarization source. As a result, there is an excellent change in the ratio of the fixed value of the Polarization voltage to the voltage drop at the wall resistance; this results in an increase in the current density in the masonry of several ten percent (with unchanged enforcement), which in turn contributes to increasing the effectiveness of the drying.

The decrease in the polarization voltage and the decrease in the value of the resistance of the area of the masonry between the plus and minus electrodes, combined with the decrease in the distance between them, causes an increase in the current values in the effective range of the electric field, and thereby an increase in the electroosmotic flows, enables the conditions to be met that are sufficient for "sucking" the hydrophobic liquid even with moist masonry and thereby enables the hydrophobization work to be carried out in parallel with drying, which makes it possible to shorten the total duration of the implementation of the measure on the masonry.

The penetration area of the hydrophobic agent is expanded in relation to the area which is achieved by gravitation in previously dried masonry, and all the more in relation to the hydrophobization process according to PL-PS 103 633.

This is associated with the elimination of the harmful, renewed, electro-osmotic water-drawing from the soil, which takes place during hydrophobization, when the polarity of the voltage feeding the electro-osmotic system is reversed.

If the hydrophobization is carried out in parallel with drying, there is an additional advantage in the substantial reduction of the "air penetration" into the capillaries, which weakens the suction of the hydrophobic liquid.

The reduction in the area of the masonry located between the upper and lower electrodes enables the area where salinization occurs on the surface of the walls to be dried to be reduced and decreased. On the other hand, the hydrophobized area is more extensive, more stable and more workable because the introduction of the hydrophobic agents takes place outside the current flow area, that is to say at the point where no additional salinization associated with water electrolysis occurs. The final salinity is even smaller than the initial salinity because part of the salt is removed with the water.

The use of the division of the electrodes into sections, which comprise the wall sections, on which the moisture distribution is as constant as possible, as well as the feeding of these sections from separate sources makes it possible to create the conditions for the electrokinetic transport with maximum effectiveness simultaneously in the whole masonry area occurs, on which the drying and protective work are carried out.

The invention is explained in more detail using exemplary embodiments.

example 1

The moistened masonry is divided into sections along which the plus electrodes are placed, which form independent sections, which are connected to mutually independent feeding devices, depending on the amount of moisture and performance of the feeding devices.

In a building without a basement, which was moistened by capillary water drawing from the floor, plus electrodes were distributed on the masonry at a height of 30 cm above the floor area at a distance of 40 cm. The electrodes were divided into two sections, each of which was connected to a positive pole of a separate supply device with a voltage of up to 24 V and a current of up to 1 A. A common minus electrode was connected to the minus poles of the feed devices. The minus electrode was placed in the ground around the building at a depth of 50 cm below the surface of the earth. The electrode was in the form of a galvanized flat iron, which was in the floor at a distance of 60 cm from the outer walls.

At a distance of 20 cm above the plus electrodes, holes with a diameter of 20 mm were drilled for the introduction of the hydrophobic agent. These holes were drilled every 20 cm at an angle of 30 ° to the horizontal and with a depth of 30 cm with a wall thickness of 51 cm.

During the current flow, a hydrophobic liquid, which was prepared on the basis of silicone resins, was poured into these holes. After a month since the completion of the work, the initial moisture had dropped from 12 to 18% to 7 to 10% and after three months to less than 5%.

Example 2

In a building in which the amount of moisture in the walls averaged 14% and was distributed relatively evenly, plus electrodes with 60 cm intervals were used and divided into four sections, each 50 m long, which consisted of four identical feeding devices with max. Power of 18 V voltage and a current of 0.7 A were fed. Minus electrodes made of galvanized steel tubes with a diameter of 25 mm and a length of 1.5 m were used, which were hammered into the ground every 10 m around the building and were connected to each other by a cable, which resulted in a common minus Electrode for the whole building was formed.

The individual sections of the plus electrodes were connected to the plus poles of the separate feed devices and the common minus electrode to the minus poles of the feed devices.

Holes with a diameter of 24 mm were drilled at a distance of 20 cm above the plus electrodes in order to introduce the hydrophobic agent. The holes were drilled at an angle of 40 ° to the horizontal at a distance of 20 cm and with a depth of 45 cm with a wall thickness of 65 cm. During the operation of the plant, the hydrophobic agent, which was prepared on the basis of silicone resins, was introduced into the holes. After one month since the completion of the work, the amount of moisture in the walls had dropped from the initial value to 8 to 10% and was less than 5% after four months.

The results achieved indicate a significant reduction in the drying time of the masonry in the building. In addition, the chemical compounds were salted out intensively below the plus electrodes, specifically outside the zone of the hydrophobic barrier. In this way, not only is an acceleration of the drying process and an increase in the thickness of the hydrophobized zone in the masonry achieved, but also a substantial increase in the resistance of the hydrophobic barrier.

Claims (1)

1. Method for drying and protection of masonry from recurring dampness, in which the drying process is carried out by means of an electromotive apparatus and the seal is formed by means of a hydrophobic medium introduced into holes bored at an angle to the ground surface, characterised in that the upper row of electrodes is set into the masonry spaced from the negative electrodes by up to 1 metre, and preferably in the neighbourhood of the earth surface, and in order to achieve even drying the spacing between the positive electrodes in a row is determined depending on the size of the dampened area and the electrodes are divided into groups which are supplied from separate sources, in that the holes for the hydrophobic medium are bored outside the zone of influence of the electrical field above the upper row of electrodes, and in that the hydrophobic medium is continuously introduced into these holes during the flow of current which,following the principal of continuity of current as well as capilliary and gravitational transport and convenyance, penetrates into the capilliaries and pores where it spreads out, where the electrokinetically downwardly-transported water is removed, so that a seal against dampness is formed.