Orange S. Marshall

Electro-Osmotic Pulse Technology for Corrosion Prevention and Control of Water Intrusion in Below Grade Concrete Structures

In below-grade buildings and buried structures, such as those constructed as hardened secure facilities and used for munitions storage on U.S. Army installations, water intrusion can cause serious damage and reduce penetration resistance. Inside the building active water and high humidity can result in corrosion of HVAC, electronic equipment, as well as damage or disrupt mission critical electronic equipment. In the adjacent backfill and the structure itself, excessive water can seriously compromise the structural hardening of the facility. Thus, it is vital to Army sustainability to control moisture in below-grade structures and eliminate corrosion of electrical mechanical equipment. This also prevents mold growth on the interior surface of below grade concrete walls and floors. Control of water movement involves both actively removing water in and around a building, and the use of barriers to prevent water from penetrating to interior spaces. A pumping system is typically required with the use of a barrier system to assist in controlling the movement of moisture into the structure. Conventional waterproofing technologies are expensive and often have short service life. A new approach is needed—a cost effective and robust solution—to the pervasive problem of water intrusion. Electro-Osmotic Pulse is a promising alternative solution presented here. Electro-Osmotic Pulse (EOP) technology uses pulses of electricity to reverse the flow of water seepage. The applied voltage causes moisture to flow out of the basement walls and away from the building. The technology works by alternately pulsating a direct electric field with an off period. The first part of the sequence consists of a pulse of positive voltage (as seen from the dry side of the concrete wall), followed by a pulse of negative voltage. This is followed by a period when no voltage is applied. Of the three parts, the positive voltage pulse has the greatest time duration. The amplitude of the positive signal is typically on the order of 20 to 40 Volts DC. This electrical pulse causes cations (e.g., Ca++) and associated water molecules to move from the dry side (anode) towards the wet side (cathode) against the direction of flow induced by the hydraulic gradient, thus preventing water penetration through buried concrete structures. Laboratory and field tests have shown an increase in calcium compounds at the cathode side of test specimens. The negative portion of the pulse increases the efficiency of moisture movement by depolarizing the electrodes. Electro-Osmotic Pulse (EOP) technology has been successfully installed in military structures such as family housing, steel reinforced deep structures, and tunnels. EOP has also been implemented on Civilian structures such as residential structures, D.C. Metro Tunnels, and an underground treasury vault. EOP has been shown to prevent moisture seepage into below-grade structures. It is effective at keeping concrete surfaces at or below 50 percent humidity content, meaning the treated space stays dry, indoor relative humidity stays low, and no mold or mildew can grow. This technology has received the 2002 international NOVA award for innovation in construction, and twice nominated for the CERF Pankow award (1999 and 2004). The ERDC research on this technology has also been recognized by the 2004 Army Research and Development Achievement Award.

Investigation of hydrophobic concrete additive for seawall replacement at Pililaau Army Recreation Center, Hawaii : final report on Project F09-AR05A

Department of Defense Corrosion Prevention and Control Program (U.S.) United States. Office of the Under Secretary of Defense for Acquisition, Technology, and Logistics.

In Situ Lining of a Pre-Action Fire Suppression System to Prevent Pitting Corrosion of the Carrier Pipe

A pre-action fire suppression system was installed in a portion of a US Army Reserve Component Headquarters building in the Southeastern United States, when the structure was constructed in 1995. A pre-action fire suppression system, which is normally kept at a standard internal air pressure using air compressors in the basement electrical-mechanical room, is designed to remain dry and only have water in it in the event of a fire. The installed pre-action system developed pinhole leaks due to what appeared to be galvanic corrosion. An in-situ epoxy lining technique was used to stop the corrosion and restore the integrity of the fire suppression system piping. The work included lining of all interior pre-action piping mains, risers, branch laterals and service piping to individual sprinkler head locations, installing new ½” sprinkler heads on the preaction system followed by recertification of the pre-action system. This presentation describes the in-place epoxy lining process and presents before and after photographs of the coated system used to eliminate the pin hole leak problem.

Rapid Soil Stabilization and Strengthening Using Electrokinetic Techniques

Abstract : The Army has a requirement to develop methods of strengthening soil to support rapid runway and roadway construction. A study was undertaken on the use of DC current applied to soil to form cementing phases in the soil. Preliminary work was on the use of zinc. aluminum. and iron in a variety of granular materials. Metal ions primarily form soft metal hydroxide gels that produce no immediate soil strengthening. Passing current through soil mixed with an alkali-reactive silicate produces rapid hardening with strength to 2,000 psi.