Chemistry: electrical and wave energy – Processes and products – Electrostatic field or electrical discharge
Patent
1991-09-26
1994-11-29
Niebling, John
Chemistry: electrical and wave energy
Processes and products
Electrostatic field or electrical discharge
204130, 204299R, B01D 1302
Patent
active
053687094
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method and means for controlling the relative humidity in concrete and masonry, including masonry wherein cement is used as a bonding agent. The structure may be reinforced or not, and the method may also be used in plaster, mortar in stone masonry and light concrete structures.
The object of the invention is a directional control of the migration path of the humidity, in or out of a structure by use of a DC current pulse in a determined sequence.
Thus it is desired to make a control of the relative humidity content in both small and large concrete structures, for instance to reduce the humidity from 100% to about 70% in order to maintain the most suitable conditions, also for a possible reinforcement and further to keep humidity away from the structure with a regard to fracturing by frost, the occurrence of fungi and wet rot, possibly high air humidity in rooms, so-called cellar odour, limit corrosion, slow down the carbonatization and vice versa.
By start-up of a device according to the invention the relative humidity will be high. By using a high voltage the dehumidification is accelerated. The relative current drawn and power are high. When 80% relative humidity is approached, the current drawn is reduced. The voltage will still provide a high power due to a reduced conductance. The process will nevertheless be relatively slower as the relative humidity is reduced. This is caused by the conductance of the concrete structure being reduced. A structure with a supposedly low relative humidity will maintain the achieved condition by the conductance increasing on renewed penetration of liquid.
The method is advantageously realized with a device which comprises a hybrid circuit which drives an attached power transistor stage, so that the latter is either wholly conductive or completely blocking. Also within the scope of the invention is a device wherein transistor stages are replaced by relays or thyristors. The device includes functions such as a monitoring system which informs of circuit breakage, short-circuits, current interruptions, blown fuses and normal operation.
The electronic device feeds the anodes (for instance reinforcement) or anodes provided in the structure with the particular pulse pattern of the invention and thereby creates an osmotic pressure due to said pulse pattern. This pressure drives humidity in the capillaries out of the concrete towards the externally provided ground cathode.
The improvement achieved comprises: increased power, a monitoring and alarm system, reduced drift when the temperature changes, reduced heat generation in the solid state power circuit, improved apparatus housing and power supply certified by the Authorities.
In order to optimize the device with regard to power consumption, the output stage is constructed as a bridged complementary stage, wherein saturation of transistors is made possible by predriver and driver stage having their own power supply, with compensation for voltage reduction in solid state circuitry in a push-pull complementary stage. This stage is bridged with a corresponding push-pull complementary stage.
The features characterizing the invention are as follows:
1. Due to safety reasons, a positive and negative pulse of 40 V is used.
2. Salts are driven out with the humidity, something which slows down the carbonatization process.
3. Anodes which are adapted to the pH values and the chemical conditions on the installation site are used.
4. Current and voltage is dependent on and self-regulated in dependence of the conductivity and the humidity of the concrete structure. The current drawn is limited by a predetermined boundary value.
5. The direction of the osmotic pressure is controlled.
According to the invention there may for instance be used DC current pulses with a positive pulse fed to the reinforcement of the structure or to an installed anode, the pulse having a controllable duration. Then a negative pulse is fed to the anode for about 1/6 of the duration of the positive pulse, followed by a interval with a dur
REFERENCES:
patent: 4600486 (1986-07-01), Oppitz
patent: 5015351 (1991-05-01), Miller
Elcraft A/S
Mayekar Kishor
Niebling John
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