Michael K. McInerney

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.

Use of Small-Scale Electro-osmotic Systems in Controlling Groundwater Movement Around Structures

Small-scale electro-osmotic systems for use around commercial and residential structures are becoming increasingly common as a method of controlling the water seeping through concrete foundations or seeping into basements and other underground structures. These systems are designed for continuous use in moving water out of the soil adjacent to the structures. There is little engineering guidance on the selection and installation of the components for these small-scale systems. Features such as soil conditions, positioning of electrodes, operating voltages, operating patterns for decreasing polarization problems, and selecting the types of electrodes are critical in assuring efficient operation and a long service life. By screening sites to make sure that the geological conditions are appropriate and tailoring the system to fit the site, electro-osmotic dewatering can be applied safely and effectively, giving a property owner a method other than conventional drains for controlling groundwater problems on a building site.

Demonstration and validation of single-well electro-osmotic dewatering systems for corrosion mitigation : final report on Project F10-AR07

When precipitation, runoff, and snowmelt percolate into soil and overload existing drainage infrastructure, the water table around building foundations can rise and infiltrate through cracks and joints. When infiltration exceeds sump pump capabilities, standing water and residual dampness can corrode or ruin fixtures, equipment, and stored supplies, also promoting mold growth that can make workers ill. The conventional solution—trenching and installing drainage tiles—is expensive, disruptive, and often ineffective. This paper documents the development and demonstration of a patented electro-osmotic dewatering technology that works with outdoor wells and pumps to lower the water table around subgrade structures, thereby reducing or eliminating damage to building contents and the subgrade structure. Following a site-selection procedure, an optimized prototype system was installed for an administrative building at Blue Grass Army Depot, KY. The system was able to nominally lower the water table, and electro-osmotic flow was confirmed to positively impact pumping rates. However, site-specific drainage issues allowed rainwater to bypass the system and infiltrate the basement. Given less problematic site conditions, the projected return on investment for the technology is 9.97. Recommendations are offered for further development that could significantly increase technology effectiveness.

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.

Combined Structure Geometry and Anode Placement Effects on Cathodic Protection Effectiveness

An impressed current cathodic protection system was applied to an uncoated test sample. The test sample was chosen to represent an essential right angle feature of a common structure. Anode placement was quantitatively shown to affect the resulting surface polarization distribution. Two distinct types of local polarization depletion zones have been demonstrated. These regions of lesser polarization represent a locally insufficient amount of cathodic protection compared to criteria designated values. Conversely, for geometrically complex structures containing sharp features, the possibility of locally evolving hydrogen gas is also discussed.

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.