US 5,015,351 A · Method for electrochemical treatment of porous building materials, particularly for drying and re-alkalization

Abstract

An electro-osmotic dewatering procedure is disclosed for removing water from saturated, porous building materials, such as concrete, brick and the like. A controlled, cyclical voltage is applied to an electrode system, to effect osmotic migration of water from an anode electrode, located within the structure or in contact with it, to a cathode electrode, typically spaced from the structure but in electrical circuit with it. The cycle of operations includes a first energy pulse in a direction to effect osmotic migration, followed by a substantially shorter but definite pulse of reverse polarity to prevent or minimize formation of insulating gas films and/or corrosion products. Transition from the primary pulse to the reverse pulse, and from the reverse pulse to the subsequent primary pulse, is at a controlled rate to permit discharge of stored voltage, as a function of inherent capacitance of the system, and to avoid generation of RFI radiations. For treating reinforced concrete, cycling is preferably controlled automatically, as a function of the monitored passivity or non-passivity of the internal reinforcement, so as to avoid creation of corrosion products. Certain aspects of the invention are applicable to other treatments of reinforced concrete, such as realkalization.

Claims18

Dependent claims

In a process for treating moist, porous building materials and the like, wherein positive electrode means are associated with the moist, porous material, negative electrode means are located remotely of and in electrical association with the positive electrode means through at least a portion of the porous material, and a voltage is applied to said electrodes to effect electrolytic action in the region between said electrodes, the improvement characterized by,

(a) impressing an electro-osmotically effective first voltage on said electrodes for a first portion of an operating cycle,
(b) thereafter impressing a second voltage of opposite polarity on said electrode means for a second portion of said operating cycle,
(c) effecting a time-controlled transition from said first voltage to said second voltage where the time rate of voltage change during said transition is such as to substantially avoid r.f.i radiations,
(d) said first and second voltages and said first and second portions of said operating cycle being so related that energy utilized in said first cycle portion is at least twice that utilized in said second cycle portion, and
(d) repeating said operating cycle continuously over a period of time to effect a predetermined treatment of said porous material.

2 more elements

In a process for reducing the moisture content of wet, porous building materials and the like, wherein positive electrode means are associated with the wet porous material, negative electrode means are located externally of the wet porous material and in electrical association with the positive electrode means through at least a portion of the porous material, and a voltage is applied to said electrode means to effect electro-osmotic movement of water from said porous material toward said negative electrode means, the improvement characterized by,

(a) impressing an electro-osmotically effective first voltage on said electrodes for a first portion of an operating cycle,
(b) effecting a time-controlled transition from said first voltage to a second voltage of reverse polarity over a sufficiently long period of time such that, during the transition interval, internal capacitance of the electrode-porous material system is discharged, and r.f.i. radiations are effectively avoided,
(c) impressing said second voltage during a second cycle portion to effect substantial dissipation of insulating gas films and/or corrosion forming products formed at said electrode means, and
(d) repeating said operating cycle continuously over a period of time to effect a removal of moisture from said porous material.

1 more element

In a process for treating moist reinforced concrete or the like, wherein first electrode means are associated with the moist concrete and second electrode means are spaced from and in electrical association with the first electrode means through at least a portion of the concrete, and wherein at least one of said electrode means comprises steel reinforcement material, and a voltage is applied to said electrode means to effect electrolytic action, in the concrete in the region between said electrode means, the improvement characterized by

(a) impressing a voltage of from about 20 to about 40 volts between said first and second electrode means during a first cycle portion and a voltage within a similar range of magnitudes but of opposite polarity during a second cycle portion,
(b) monitoring the passivity of the electrode means to which a positive voltage is applied during said first cycle portion,
(c) continuing the first cycle portion while the monitored electrode means remains passivated,
(d) discontinuing said first cycle portion and commencing said second cycle portion when the monitored electrode means has become substantially de-passivated and subject to corrosion, and
(e) discontinuing said second cycle portion and commencing said first cycle portion when the monitored electrode means has become substantially re-passivated.

2 more elements

Dependencies are inferred from the claim text.

Method for electrochemical treatment of porous building materials, particularly for drying and re-alkalization

Life of this patent

Method for electrochemical treatment of porous building materials, particularly for drying and re-alkalization

Life of this patent

Abstract

Claims18