USACERL TR-98/68

6. Wiring is run from the EOP Control Unit to both the anodes and cathodes.
This wire may be installed in several different ways:

a. Surface mounted and enclosed in plastic wire mold
b. Enclosed in either metal or plastic conduit and junction boxes

c. Buried in the concrete wall with the grooves patched with mortar, creating a
flush wall finish.

7. The EOP Control Unit is turned on, adjusted and calibrated. The system is
now operational.

Fort Jackson

The first Army EOP demonstration was conducted at Fort J ackson, SC, during
FY94. To advertise this demonstration, a sign was placed near the installation.
Figure 7 shows Mr. Frank Cooper, Chief, Operations and Maintenance Division,
Directorate of Public works Fort Jackson standing next to the sign.

f. UNTED, STATES ARMY CORPS OF ENGINEERS -
¥ CONSTRUCTION ENGMEERING

DEMONSTRATION PROJECT

FACILITY ENGINEER APPLICATION PROGRAM
PROJECT NO, FEAP-FM-FO4
“0 BROVECT TITLE:
DENONSTRATION OF ELECTRO-OSMOTIC
PULSE TECHNOLOGY :

FOR THE CONTROL OF SEEPAGE
IN CONCRETE STRUCTURES

us Ai PERFORMING Lap:

z Y CERL-CHAMPAIGH, FLLINDIS.

OPRINGARAL INVESTIGATORS: ~
VINCENT F. HOCK

HENRY §, CARDENAS .

PERFORMING CONTRACTOR:

Figure 7. Demonstration project sign.



USACERL TR 98/68

Appendix: Data Logged From Building 5,
McAlester AAP, OK

The following table contains data recorded by the logger at Building 5, McAlester
AAP, OK. The data most important to tracking the progress of the EOP system
are those labeled “Watts DC,” “Wall RH,” “Well,” and “Rainfall.” These report the
DC output power from the EOP power supply, the relative humidity within a wall
cavity, the water table depth, and rainfall, respectively.

Outdoor
AC AC DC Watts Rom | Room} Wall Wall Temp Outdoor RH
Date Volts _| Amps | (Computed) | Temp RH Temp RH | Well | Rainfall | (Average) | (Average)

11/6/96 | 209.67 | 0.00 * 74.45 | 56.89 | 71.51 95.80 ‘ 1.97 66.10 84.00
11/7/96_| 208.92 | 0.15 22.56 73.70 | 45.05 | 71.41 95.79 * 1.08 50.30 71.00
11/8/96 | 209.18 | 0.25 42.85 71.34 | 37.61 | 71.26 _ | 95.88 * 0.00 45.20 58.00
11/9/96 | 209.27 | 0.24 40.54 69.83 | 44.27 | 71.01 95.74 |-15.26| 0.00 50.10 59.00
11/10/96 | 209.47 | 0.23 39.17 69.15 | 40.46 | 70.87 | 95.65 |-15.31| 0.00 46.80 52.00
11/11/96 | 209.61 | 0.23 38.26 68.28 | 41.83 | 70.59 | 95.55 |-15.36] 0.00 49.30 62.00
11/12/96 | 208.98 | 0.22 37.17 69.03 | 4277 | 70.46 | 95.43 |-15.54] 0.00 45.40 74.00
14/13/96 | 209.07 | 0.22 36.54 69.38 | 49.32 | 70.38 | 95.32 |-15.40] 0.00 48.20 89.00
11/14/96 | 209.04 | 0.22 36.15 70.05 | 56.58 | 70.46 | 95.21 |-15.20] 0.00 54.20 88.00
11/15/96 | 209.56 | 0.22 35.86 70.04 | 60.33 | 70.53 | 95.19 |-15.06] 0.05 58.50 77.00
11/16/96 | 209.50 | 0.21 35.36 70.94 | 63.58 | 70.65 | 95.18 }-14.86] 1.41 62.70 86.00
14/17/96 | 209.44 | 0.21 35.24 70.29 | 56.43 | 70.63 | 95.19 |-15.27| 0.00 41.50 77.00
11/18/96 | 209.11 0.21 34.47 69.81 | 49.67 | 70.42 | 95.13 |-15.12] 0.00 44.70 79.00
11/19/96 | 209.15 | 0.21 34.10 70.89 | 52.69 | 70.51 95.06 |-14.83] 0.00 55.30 90.00
11/20/96 | 209.39 | 0.21 33.88 72.40 | 58.83 | 70.81 95.04 |-14.71| 0.00 62.50 89.00
11/21/96 | 209.30 | 0.21 33.42 72.22 | 50.83 | 70.97 | 95.09 |-15.06} 0.00 51.30 81.00
11/22/96 | 209.75 | 0.20 33.12 70.14 | 47.37 | 70.75 | 95.05 }-15.19} 0.00 50.10 69.00
11/23/96 | 200.51 | 0.20 32.30 70.22 | 51.97 | 70.64 | 94.99 |-14.91| 0.94 56.60 80.00
11/24/96 | 209.45 | 0.20 31.77 68.58 | 45.78 | 70.38 | 94.97 |-15.09| 1.72 33.10 92.00
11/25/96 | 209.16 | 0.19 30.74 65.21 | 43.79 | 69.61 94.86 |-15.13| 0.00 29.40 92.00
11/26/96 | 208.95 | 0.19 30.00 63.80 | 44.76 | 68.82 | 94.72 |-15.52| 0.07 30.20 87.00
11/27/96 | 208.94 | 0.19 29.20 62.99 | 44.39 | 68.19 | 94.54 |-15.56] 0.25 30.70 88.00
11/28/96 | 208.37 | 0.18 28.65 63.61 | 44.55 | 68.00 | 94.36 |-15.27] 0.41 36.20 75.00
11/29/96 | 209.34 | 0.18 28.24 64.88 | 51.89 | 67.96 | 94.24 |-1470] 1.52 44.80 92.00
11/30/96 | 209.51 | 0.18 27.95 66.46 | 54.48 | 68.08 | 94.19 |-14.57] 0.04 48.50 92.00
12/1/96 | 209.46 | 0.18 27.68 66.68 | 46.06 | 68.15 | 94.14 |-14.89] 0.00 41.00 63.00
12/2/96 | 209.55 | 0.18 27.44 67.10 | 43.65 | 68.19 | 94.09 |-14.82| 0.00 48.10 58.00
12/3/96 | 209.04 | 0.17 26.90 75.52 _} 31.81 68.77 _{ 94.02 |-15.16] 0.00 42.30 64.00



USACERL TR 98/68

wells, report requirements, and certain extra experimental requirements have
been eliminated from the base costs).

The prices in Table 7 reflect the costs of the EOP system and labor only. Next,
the price of the EOP system based on installed costs and linear foot of wall must
be calculated. As for installation, both sites required some degree of interior
access to the basement level, but neither excavation nor damp-proofing were
required. Installation of the probes is generally based on a 18-in. spacing and
about 4 in. to 8 in. from the floor level. The price includes the EOP Control Unit,
anodes, ground rods, and all the wiring and labor for installation (Table 8).

The installer, Drytronic, Inc., estimates life cycle of the equipment and the
pulsing technology system to be greater than 10 years. Therefore, one could
assume a normal cycle with almost zero maintenance for that period of time.
The system does consume energy in the equivalent of a 60W light bulb left on all
the time. At $0.06/kWh national electrical cost, this cost is minimal and is
disregarded in this study. In most basement seepage conditions, one option often
tried is a sump pump (with a 10 year life) and associated piping. The resulting
energy costs would be a “wash” over time. Keep in mind that one is dealing with
extreme dampness conditions that probably have had many interim repairs, from
caulking and grouting to exterior impregnation of the soil with cement binders
and polymers to stop water migration. Obviously the life cycle of these “fixes”
was very short, or the engineer would not be considering trenching or EOP
technology.

Table 6. Standard approach cost estimate.

Action Cost per If
Site dewatering $67.53
Wood shoring $10.60
Excavation and backfill $222.00
Drain tile installation $4.20
Damp-proofing $8.00
Backfilling $1.10
Landscaping restoration $1.86
Total $315.20

Table 7. Costs of EOP technology installation.

Location Cost
McAlester AAP $18,071
Fort Jackson $20,729



USACERL TR-98/68

Chief of Engineers
ATIN: CEHEC-IMLH (2)
ATTN: CEHEC-IMLP (2)
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ATTN: CECC-P
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ATTN: CECW
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ATTN: CERD-C
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ATTN: CERD-M (2)

‘ACS(IM) 22060
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276

3/98

‘YCUS. GOVERMENT PRINTING OFFICE: 1998 - 646-081/80022


USACERL TR-98/68

k——_—__—— 2 sec < T < 10 sec

Figure 3. Generic EOP voltage waveform.

+Volts
0)
Volts

+ Pulsed DC Power Supply ~ © Cathode: Copper Ground
Rod Embedded In Soil 3 to
| 5 feet from Basement Wall
Anode: ® Al
Mortared te DC electric field promotes movement of
And/Or Floor cations (+), and associated water molecules
towards the cathode. This creates
counterflow and associated osmotic
pressure differential across concrete
section. The shorter time duration of the
negative pulse allows some moisture to be
retained within the concrete matrix
preventing overdrying of the concrete.
Inside Surface Soil Side of
of Basement Basement
Wall :
a

Basement Wall Cross Section

Figure 4. Cross section showing the EOP process.



22 USACERL TR-98/68

40° N

>)
I Lo (OX)

Figure 11. Locations of moisture meters and rebar
specimens in basement of Building 3265.

Table 2. Concrete moisture readings in Building 3265.

Moisture Meter Location
Date of Reading A B c D
08/23/94 94 92 98.3 97.6
01/10/95 44 43 68.3 64.3
08/15/96 72.5 72.14 76.3 76.8

Rebar Corrosion Potentials

In addition to concrete moisture measurements, the corrosion of rebar specimens
was investigated. Several small (~2-in. long) sections of 0.5-in. steel rebar were
embedded in various locations in the walls of the basement at Fort Jackson.
Table 3 lists the locations of these rebar specimens and Figure 11 shows the
locations of three specimens.



USACERL TR-98/68

Outdoor
AC AC DC Watts Rom | Room} Wall Wall Temp Outdoor RH
Date Volts_| Amps | (Computed) | Temp | RH Temp RH__| Well _| Rainfall | (Average) |_ (Average) _|
12/4/96 | 209.14 | 0.17 26.78 81.23 | 23.94 | 69.95 | 94.11 |-15.05| 0.01 42.70 72.00
12/5/96 | 209.28 | 0.17 26.79 83.52 | 24.36 | 70.99 | 94.18 |-14.74] 0.10 46.50 66.00
12/6/96 | 209.64 | 0.17 26.73 84.06 | 24.01 | 71.85 | 94.21 |-14.56] 0.00 54.60 50.00
12/7/96 | 209.61 | 0.17 26.45 84.75 | 21.72 | 72.52 | 94.29 |-15.03] 0.00 47.10 58.00
12/8/96 | 209.51 | 0.17 26,25 84.82 | 20.43 | 72.93 | 94.27 |-15.18} 0.00 45.00 57.00
12/9/96 _| 209.22 | 0.17 26.11 87.51 | 22.05 | 7353 | 94.21 |-14.96} 0.00 56.90 51.00
12/10/96 | 209.32 | 0.17 26.12 86.62 _| 32.81 74.15 | 94.27 |-14.72| 0.00 64.70 71.00
12/11/96 | 209.40 | 0.17 25.98 79.20 | 39.96 | 73.79 | 94.23 |-14.70| 0.00 61.10 69.00
12/12/96 | 209.28 | 0.17 25.66 76.63 | 34.11 73.19 | 94.12 |-15.04] 0.00 49.10 80.00
12/13/96 | 209.76 | _ 0.17 25.25 74.04 | 38.79 | 72.61 93.97 | -15.20] 0.00 53.60 79.00
12/14/96 | 209.64 | 0.16 24.83 73.69 | 45.72 | 72.30 | 93.88 |-15.07} 0.66 §7.20 87.00
12/15/96 | 209.73 | 0.16 24.64 71.76_| 37.83 | 71.85 | 93.82 {-15.32] 0.01 39.10 66.00
12/16/96 | 209.24 | 0.16 24.03 70.67 | 31.77 | 71.28 | 93.72 [-15.01} 0.00 36.00 69.00
12/17/96 | 209.08 | 0.16 23.59 68.46 | 31.62 | 70.73 93.60 |-15.13} 0.00 27.90 77.00
12/18/96 | 208.83 | 0.15 22.90 65.02 | 29.74 | 69.71 | 93.44 {-15.31] 0.00 20.60 60.00
12/19/96 | 208.96 | 0.15 22.15 62.50 | 29.89 | 68.65 | 93.24 |-15.35| 0.00 18.50 63.00
12/20/96 | 209.28 | 0.15 21.54 61.72_| 32.57 | 67.90 | 9299 |-15.22] 0.00 30.10 54.00
12/21/96 | 209.39 | 0.15 21.02 62.94 | 44.20 | 67.73 _| 92.82 |-14.87] 0.00 48.10 68.00
12/22/96 | 209.77 | 0.14 20.88 66.06 | 57.39 | 68.11 92.68 |-14.86} 0.00 62.60 75.00
12/23/96 | 209.50 | 0.14 20.77 68.22 | 56.15 | 6853 | 92.73 |-14.90] 0.00 50.40 72.00
12/24/96 | 209.24 | 0.14 20.39 65.24 | 35.63 | 68.16 | 92.78 |-15.42| 0.00 23.70 60.00
12/25/96 | 209.23 | 0.14 19.90 63.53 | 32.19 | 67.62 | 92.72 |-15.24] 0.00 33.50 57.00
12/26/96 | 209.35 | 0.14 19.62 65.60 | 39.59 | 67.71 92.57 _|-14.98] 0.00 41.70 64.00
12/27/96 | 209.45 | 0.14 19.46 65.33 | 44.00 | 67.73 | 92.53 |-14.93] 0.00 44.40 80.00
12/28/96 | 209.61 | 0.14 19.40 66.75_| 51.58 | 67.91 92.48 |-14.86] 0.00 54.60 77.00
12/29/96 | 209.54 | 0.14 19.22 67.56 | 43.34 | 6810 | 92.48 |-15.09] 0.00 46.90 69.00
12/30/96 | 209.42 | 0.14 19.05 69.90 | 4865 | 6843 | 9253 |-15.15} 0.00 56.00 83.00
12/31/96 | 209.52 | 0.14 19.14 70.39 | 53.64 | 68.83 | 92.62 |-15.19] 0.00 55.40 92.00
11/97 _| 209.94 | 0.14 19.26 71.01_| 54.33 | 69.07 | 92.70 |-15.08} 0.00 59.80 91.00
1/2/97 _| 209.82 | 0.14 19.08 72.18 | 55.88 | 69.33 | 92.78 |-14.95] 0.00 63.80 83.00
4/3/97 _|} 209.79 | 0.14 19.08 72.90_| 57.59 | 69.76 | 92.91 |-14.68} 0.00 68.00 77.00
1/4/97 _| 209.95 | 0.14 19.10 73.57 | 50.20 | 70.08 | 93.04 |-14.72| 0.00 60.60 60.00
1/5/97_| 209.56 | _0.13 18.75 71,78 | 37.63 | 70.03 | 93.08 |-15.20} 0.00 42.40 52.00
1/6/97 _| 209.15 | 0.13 18.55 69.31 | 32.59 | 69.65 | 93.06 |-15.44] 0.00 33.00 50.00
1/7/97_| 209.18 | 0.13 18.18 67.18 | 29.67 | 69.03 | 92.89 |-15.44] 0.00 35.00 40.00
1/8/97 _| 209.13 | 0.13 17.48 65.88 | 35.33 | 68.60 | 9271 |-1513] 0.00 32.50 81.00
1/9/97_| 209.26 | 0.13 17.33 65.16 | 39.89 | 68.26 | 9253 |-14.93] 0.44 35.00 79.00
10/97 | 209.36 | 0.12 16.79 63.88 | 32.48 | 67.84 | 92.43 |-15.15] 0.00 25.10 53.00
111/97 | 209.15 | 0.12 16.50 61.50 | 20.10 | 67.10 | 92.33 |-15.44] 0.00 16.80 56.00
1297 | 209.33 | 0.12 15.90 59.50 | 29.72 | 66.26 | 92.17 |-15.68} 0.00 15.70 67.00
1497 | 209.02 | 0.12 14.96 64.72 | 22.75 | 65.96 | 91.91 |-15.75} 0.00 18.10 61.00
44/97 | 209.08 | 0.11 14.76 72.78 | 17.45 | 67.03_| 91.87 [-15.39} 0.00 26.30 60.00
1/15/97 | 209.16 | 0.11 14.79 76.28 | 20.54 | 68.06 | 91.88 |-14.95] 0.02 34.70 71.00
46/97 | 208.97 | 0.11 14.48 77.40 _| 15.32 | 68.84 | 91.98 |-15.54] 0.00 23.10 48.00
47/97 | 209.39 | 0.11 14.38 76.81 | 13.28 | 69.07 | 91.93 |-15.52} 0.00 22.40 48.00
118/97 | 209.62 | 0.11 14.39 77.98 _| 14.87 | 69.48 | 91.88 [-15.36] 0.00 30.60 53.00

1/19/97

14.38

42.90



USACERL TR 98/68

Contents

List of Figures and Tables

1 INtrOdUCtiON .........sssecsseeseeesnseessee

2 Description of EOP Technology
Electro-Osmotic Velocity
Pulsating Electro-Osmosis....

3 Pre-Installation Site Inspection .

Building 3265, Fort Jackson.
Building 5, McAlester AAP ...........:sssssssssesecesssssssseesseseeeececsscaecessecassucesesessesseeseeneeneeneenses

4 EOP System Installation and Field Testing
Typical Floor Installation
Typical Wall Installation
Fort Jackson .
McAlester AAI

5 —_Cost/Benefit Analysis
Background.
Estimating the Cost of the Standard Approac
Standard Approach Estimate.............
Estimating the Cost of EOP Technolog)
Payback for EOP Technology

6 Conclusions and Recommendations

References
Appendix: Data Logged From Building 5, McAlester AAP, OK..........sssssssssssssssssesses 39

Distribution



USACERL TR 98/68

Estimating the Cost of the Standard Approach

Since many installations have serious seepage problems that do not respond to
simple mitigation problems, i.e., caulking, grouting, and interior damp-proofing
paint, the next (and more difficult solution) is to prepare the site for excavation
and tiling for drains (many older buildings were constructed without drains at
all). References from Means Cost Estimating Guides, Walker Estimating Guide,
and the National Construction Estimator Handbook can be used to estimate
material costs. All of these guides give costs that can be adjusted for regional
applications. The focus of this estimate is a standard basement about 8-ft deep
with a concrete exterior.

The standard estimate is drawn from construction cost guides, which is then
compared to the results of the Army test sites. The following sections note
adjustments and explain cost variances.

Standard Approach Estimate

The following is a breakdown of the cost for mitigation without using the EOP
system:

1. Site Dewatering: Where there is serious seepage, a dewatering system must
be installed before excavation. This consists of well points, drain headers,
and rented pump equipment (usually for 30 days or more).

2. Wood Shoring: Assuming the structure has an 8-ft deep foundation wall with
wet soil, at least 25 percent will have to be wood shored (maybe more to
provide access and protect workers).

8. Excavation and Backfill: Generally, in a constructed facility with
underground utilities and limited mechanical access, one will have to hand-
excavate adjacent to the walls and to the utility lines. Assuming the building
will still be occupied during this process, some disruption of normal services
will likely occur. National Construction Cost Estimator gives $117 to $144/cu



USACERL TR 98/68

19

Installation

On arrival at the site on 22 August 1994, the technicians from Drytronic (the
company contracted for the installation of the EOP system) found that
approximately one-third of the floor was covered with water, in some areas to a
depth of 1 in. Before installing the EOP system, the larger cracks were
waterproofed by chiseling out those areas above the water table where there
were cracks and resealing those areas with hydraulic cement. For the EOP
system, 83 rubber-graphite electrodes (anodes) were coated with a graphite-
mortar mixture and inserted into holes drilled into all four walls, approximately
5 in. from the floor and 18 in. apart. Figure 8 shows a rubber-graphite anode.
Twenty-four ft of rubber-graphite conductive cable was installed around the base
of a concrete pad that supported steel water tanks in the room. Three copper
grounding rods (cathodes) were driven into the exterior ground.

A Drytronic self-monitoring EOP Control Unit was mounted on one wall and all
wiring from the anodes and cathodes was enclosed and wired into the unit.
Additional work included patching holes in wall areas where equipment had
been removed, and removing unneeded steel pipes and conduit. The control unit
was activated on 26 August 1994.

Figure 8. Rubber graphite anode.



USACERL TR 98/68

Table 5. Average monthly precipitation data, Columbia, SC.

Total Total
Date Precipitation (in.) Date Precipitation (in)
August 1994 5.31 July 1995 7.86
September 1994 3.27 August 1995 6.69
October 1994 4.74 September 1995 5.51
November 1994 3.08 October 1995 3.61
December 1994 5.83 November 1995 2.89
January 1995 449 December 1995 2.19
February 1995 6.70 January 1996 2.90
March 1995 1.70 February 1996 1.16
April 1995 0.98 March 1996 6.52
May 1995 1.69 April 1996 2.38
June 1995 10.74 May 1996 2.68

McAlester AAP

Installation

On 23 July 1996, installation began at McAlester. Figure 13 shows a layout of
the basement in Building 5. During a walk-through of the building the previous
day, standing water was seen in several areas of the basement. The locations of
water infiltration were determined. These were in rooms A, B, and C. No
intrusion was noted in the boiler room and under the stairwell, so the EOP
system was not installed in these locations. In the unexcavated areas of the
structure (crawl spaces), labeled “J” and “K” in the figure, it was noted that
water had entered through a horizontal cold jointTM approximately 2 ft from the
top of the foundation walls. To prevent further water intrusion into these
unexcavated areas, the cold joint was chiseled out and replaced with caulk.

The Drytronic technicians chiseled out an area of the concrete along the floor-
wall juncture in the Industrial Hygiene Office (designated as “A” in the figure)
where a horizontal crack was discovered. This area was patched over with new
concrete. Concrete and soil resistivity tests were performed and the anode and
cathode locations determined.

* “cold joint’ results when fresh concrete has been poured over set concrete.



USACERL TR 98/68

EOP Control Unit Operating Data

The EOP power supply is configured to first generate a long duration positive
direct current (DC) pulse between the anodes and cathodes followed by a much
shorter negative pulse. The final pulse in the sequence is a zero voltage, or
“rest,” pulse. The pulse sequence and the individual pulse lengths are both
programmable. Typical settings are 6 seconds for the pulse sequence, 4.8 seconds
(or 80 percent of the sequence length) for the positive pulse, 0.3 seconds (or 5
percent of the sequence length) for the negative pulse, and 0.9 seconds (or 15
percent of the sequence length) for the rest period. Figure 3 shows an example
EOP voltage waveform.

The EOP Control Unit power supply current load was within acceptable limits,
varying from 0.75 Amps for a high humidity environment to less than 0.2 Amps
for a low humidity environment. This is a result of the characteristics of the
EOP system. The EOP power supply produces a voltage pulse of constant
amplitude (i.e., a constant voltage power supply). The resistivity of the concrete
is inversely proportional to the amount of water present in the concrete. As the
water is slowly driven out, the resistivity of the concrete increases, dropping the
current load of the power supply, since current is inversely proportional to
resistance (Ohm’s Law). Table 1 shows the current and voltage outputs of the
EOP power supply. The slight increase in output current is due to the higher
water table during July and August 1996.

Concrete Humidity Readings

During installation of the EOP system, concrete moisture readings were taken at
different locations on the walls. The exact locations of these readings (and the
locations of the three rebar specimens mentioned in the following section) are
shown in Figure 11. Table 2 lists the moisture measurements taken at three
different times: (1) at the time of installation, (2) at the 5-month performance
check, and (3) 2 years after installation. The data are presented as percent
relative humidity. All measurements were made at the concrete surface, not
internally. The most suitable humidity for concrete structures is ~70 percent.
Note the direct correspondence between the power supply current (Table 1) and
the concrete humidity (Table 2).

Table 1. DC power supply output.

Date of Reading DC Volts DC Amps
1/10/95 +37 0.2
8/15/96 +30 0.75



34 USACERL TR-98/68

yd" as a base range, depending on soil conditions. One can use an average
estimated at $125/cu yd.

4. Install Drain Tile: Assuming a retrofit common action of plastic perforated
drain tile in a gravel bed at the edge of the footing, one can assume a range
from $4.19 to $4.31/linear foot (If) including O&P (1993 Means Cost
Estimating Guide). Note that steel, clay and concrete pipe are reasonable,
but more expensive alternates.

5. Damp-proofing: Common practice is to apply a coating to the exterior surface
of the exposed foundation wall. Alternate approaches based on soil conditions
and water content might be a fluid elastomeric at 1.61/sq ft, a bituminous
coating at $0.69/sq ft, or in more serious leakage situations, an EDPM
membrane applied to the wall at $1.44 to $1.96/sq ft. For estimating,

$1.00/sq ft will be used.

6. Backfilling: In the process of excavation, one assumes hand work and placing
the soil adjacent to the trench. For backfilling, one can assume mechanical
backfilling with some tamping of the soil ($1.10/f in Means Building
Construction Cost Data).

7. Landscaping Restoration: Most areas adjacent to existing buildings will have
mature grass or greenery that will have been disrupted by the excavation
process. Restoration consists of reseeding, fertilizing, and replanting shrubs
for the building perimeter.

Table 6 gives the breakdown of the costs for each facet listed above, including the
approximation of the cost per linear foot (If) of the exterior foundation wall. This
assumes a contract for the whole building and standard depth of 8 ft with
average, but wet soil conditions.

Estimating the Cost of EOP Technology

The original contracts to the EOP installer were analyzed and adjustments were
made to the contract prices to reflect generic installations (i.e., travel, monitoring

* 14 cuyd = 0.765 m’; 1 sq ft = 0.093 m*.



16 USACERL TR-98/68

4 EOP System Installation and Field
Testing

Typical Floor Installation

Below is a generic procedure for a typical floor installation of the EOP system as
used by Drytronic of North America:

1. Repair any cracks or voids where obvious water penetration is occurring with
either mortar, grout, foams, or epoxies (depending on conditions). These
materials must be compatible with the EOP System.

2. A resistivity test of the concrete and soil is done to determine both the
pattern of the anode cable (positive electrode) and the number and locations
of the cathodes (negative electrodes). One anode and cathode are temporarily
installed in the concrete floor and soil, respectively, and are connected to an
EOP Control Unit. The voltage and current in the circuit are measured and
used to compute the concrete/soil resistivity. A lower resistance requires a
more dense anode cable pattern and/or a higher number of cathodes. (The
objective is to achieve a certain current density in the concrete.)

3. Grooves are cut into the floor in the pattern that was determined from
resistivity testing. These grooves will vary in width and depth depending on
the type of anode cable to be installed in the floor. The anode cable is placed
in these floor grooves.

4. Cathodes are installed below the floor and, if necessary, outside the structure.
Floor installation is done by drilling holes through the floor at the locations
determined by resistivity testing. The cathodes can then be installed into the
soil through the floor. Cathodes can be installed outside the structure by
driving them into the ground like an electrical ground rod or by installing
through the wall in a manner similar to the floor installation.

5. The EOP Control Unit is mounted in a location suitable to both the user and
the installer.



8 USACERL TR-98/68

2 Description of EOP Technology

If ions of one sign are preferentially adsorbed at a solid solution interface, a net
charge or electric potential difference develops across the interface. This
phenomenon is referred to as electro-osmosis. (The basic physics and chemistry
of electro-osmosis can be found in several textbooks and treatises: W.H. Hamill
et. al. 1966; S. Glasstone, 1946; K.P. Tikhomolova, 1993) It was found that when
a potential difference is applied to electrodes immersed into an electrolyte
solution on opposite sides of a porous plug or fine capillary tube, a flow of the
solution results. Similarly, when a solution is forced through such a barrier by
hydrostatic pressure, a potential difference develops between the solution on one
side of the barrier and that on the other. This is called the streaming potential.

Descriptions of these phenomena are based on the concept of electric double
layer. A layer of ions (which is approximately a single ion in thickness) of one
sign is firmly adsorbed on the solid surface or particle, the sign of the charge
depending on the nature of the surface and other conditions. The region as a
whole is electrically neutral, and an equal number of opposite electric charges
are present in an adjacent ionic atmosphere which, as the term implies, becomes
more attenuated as distance from the surface increases. This is called the diffuse
layer. When the solid surface and fluid are in relative motion, there exists a
velocity gradient, and a thin film of solution, together with the ions it contains, is
immobilized near the wall. Part of the ion atmosphere moves with the solution,
and part (together with adsorbed ions) effectively belongs to the surface. As a
result, the liquid phase and the wall have different net electric charge, and the
application of an external electric field produces relative motion.

For example, electro-osmosis occurs in clay soils when cations in the diffuse layer
are driven by the application of an external electric field. As a result, a velocity
field in the pore fluid develops (Figure 1). The velocity distribution changes
rapidly near the particle’s surface, but then becomes flat at the edge of the
diffuse layer. Hence, electro-osmotic flow appears as plug flow through the pores
of soil.



USACERL TR 98/68

31

5 Cost/Benefit Analysis

Background

EOP technology should be used selectively. A properly designed and constructed
building foundation with appropriate damp-proofing will correct most water
problems inherent in the traditional designs of many foundation systems.
However, severe problems in existing basements may require a more serious
approach to mitigate moisture damage. In these selective problem areas, the
common approach to mitigation is to excavate to expose the wall area and the
base of the foundation, and then to replace the damp-proofing on the wall surface
and install a drain tile system around the building or affected area. This is a
costly endeavor. Furthermore, most contractors severely limit their warrantee
against future seepage in areas with high water tables.

In buildings with daily occupancies and mature landscaping, retrofitting (by
“trenching and draining”) a foundation is not easy. (In the case of McAlester, 30
percent of the wall faced an exterior crawl space. Mechanical equipment could
not perform in so tight a space, so hand digging would have been required.) Any
interior application that can mitigate water-related problems will save the cost of
excavation. Further, if the alternative can mitigate corrosion damage to
mechanical equipment along with humidity and mold problems, it will yield
benefits beyond the initial cost savings.

How to best estimate the initial cost savings for purposes of decisionmaking
must be based on experience and standard construction industry reference cost-
estimating guides. The comparison of the standard waterproofing technology to
EOP technology is based on field experience at Fort Jackson and at McAlester
AAP. Figures 17 and 18 show the results of EOP application at Fort Jackson and
McAlester AAP.



USACERL TR-98/68

TekRoll: 250 Sfs Sample

30 pg:
20F--f::
10
0 a
10 bt
-20
-30

Voltage (Volts)

i i i i i

wy 1s

Ts chi 7

Figure 14. EOP unit output waveform recorded at McAlester AAP, November 1996.

Ambient room humidity and temperature sensors are monitoring the Industrial
Hygiene Office. A well was installed to monitor the level of the water table
outside the basement. In addition to these sensors and probes, the electrical
power consumption of the EOP system is monitored to determine the power
output of the power supply and the cost of operation. Most of these monitoring
devices are fed into a datalogger that is installed on site and is remotely
accessible via modem. The data is collected and stored in the datalogger until
downloaded to a computer.

The parameters being remotely monitored in Building 5 are:

The EOP Control Unit AC input voltage

The EOP Control Unit AC input current

The room temperature of the Industrial Hygiene Office (IHO)
The relative humidity of the IHO

oF ew ye

The temperature within the 6 in. cavity of the east wall of the THO



USACERL TR 98/68

1

Introduction

Background

Groundwater intrusion through a building’s foundation (i.e., a “wet basement
problem”) can cause serious damage that is expensive to correct. Basement
dampness can ruin expensive equipment, e.g., Heating Ventilation, and Air-
Conditioning (HVAC) equipment, which is often located in basement space; can
increase maintenance requirements (through frequent repainting or cleaning to
combat mold growth); and can make affected areas uninhabitable or even
unusable (e.g., as a result of poor air quality).

In fact, a properly designed original foundation with appropriate damp-proofing
will avoid most water problems. However, in older buildings, such as those
common on U.S. Army installations, severe damp-basement problems call for
immediate action to mitigate water damage. In selective problem areas, the
usual approach is to “trench and drain,” in other words, to: (1) excavate to
expose the wall area and the base of the foundation, and (2) replace the damp-
proofing on the wall surfaces and install a drain tile system around the building
or affected area. This expensive process is further complicated by the fact that
most contractors limit their warrantees against future seepage in areas with
high water tables.

Electro-osmotic pulse (EOP) technology offers an alternative that can mitigate
some water-related problems from the interior of affected areas without the cost
of excavation. The EOP alternative can further mitigate corrosion damage to
mechanical equipment along with humidity and mold problems.

Electro-osmosis is not a new discovery although new applications for this
technology are still being developed. In 1809, F-F. Reuss originally described
electro-osmosis in an experiment that showed that water could be forced to flow
through a clay-water system when an electric field was applied to the soil.
Research since then has shown that flow is initiated by the movement of cations
(positively charged ions) present in the pore fluid of clay or similar porous media
such as concrete; the water surrounding the cations moves with them. Electro-



USACERL TR-98/68

List of Figures and Tables

Figures
1 Movement of cations in a soil pore by electro osmosis.

2 Arresting contaminant migration in an earthen landfill liner. ......-.--ssseseesesseeeeensen

3 Generic EOP voltage waveform

4 Cross section showing the EOP proceSS. .......s:ssssssssssessssssssseesestenesstensentensersenten

5 Standing water in basement of Building 3265, Fort JACKSON. .......---ssssesesnseeeseess

6 Standing water in basement of Building 5, McAlester AAP. ....

7 Demonstration project SIGN. .........-s+ 18

8 Rubber graphite anode. ...........ssee 19

9 Layout of EOP installation at Fort Jackson. +20

10 Mr. Cooper demonstrating the operation of the EOP control unit. .... +20

141. Locations of moisture meters and rebar specimens in basement of Building 3265. ....22

12 Hydrograph line from monitoring well Fort JACKSON. .ocssecsecssesseersecseesscsseessesseeeesessseesnees OA

13 Basement of Building 5 at McAlester AAP........-.ss-sscssssssssssesesseseneensesneensesnnssseennesanesenes

14 EOP unit output waveform recorded at McAlester AAP, November 1996...

15 Power consumption of EOP system in relation to relative humidity in the wall

16 Water table with respect to the basement floor for McAlester AAP.......

17 Dry floor in basement of building 3265, Fort Jackson, following EOP application. ......32

18 Dry floor in basement of Building 5, McAlester AAP, following EOP application. .........32
Tables

1 DC power supply output...... suessucsuessscsuccsscsseccesseeneecarenssssesssessecrssssseesseesness 2d

2 Concrete moisture readings in Building 3265. ........ssssssecssceecereeenseenssssesssssesssssessssens OO

3 Location of rebar SPECIMENS. .......sssssessssseecssenterneesteensesesssssessnseneenvenasennssaseenssnnecnnssaneeste

4 Specimen corrosion potentials. .............+.

5 Average monthly precipitation data, Columbia, SC. 25

6 Standard approach cost estimate. 35

7 Costs of EOP technology installation

8 Calculation of EOP System Based on Installed Costs and If of Wall. .......--s-sssesssessees 36



USACERL TR 98/68 17

6. Wiring is run from the EOP Control Unit to both the wire anodes and the
cathodes. By using properly insulated wires, these wires can be embedded in
the grooves that are in the floor.

7. After all wiring is placed in the grooves, mortar is used to fill the grooves to
within 4 to % in. of the surface. Then a leveling agent is used to completely
fill the groove and level the surface.

8. The EOP Control Unit is turned on, adjusted, and calibrated. The system is
now operational.

Typical Wall Installation

Below is a generic procedure for a typical wall installation of the EOP system as
used by Drytronic of North America:

1. Repair any cracks or voids where obvious water penetration is occurring with
either mortar, foams, or epoxies depending on conditions. These materials
must be compatible with the EOP System.

2. A resistivity test of the concrete and soil is done to determine both the
number and locations of the anodes (positive electrodes) and the cathodes
(negative electrodes). One anode and cathode are temporarily installed in the
concrete wall and soil, respectively, and are connected to an EOP Control
Unit. The voltage and current in the circuit are measured and used to
compute the concrete/soil resistivity. A lower resistance requires a higher
number of anodes and/or a higher number of cathodes. (The objective is to
achieve a certain current density in the concrete.)

8. Once an anode distribution is determined, %-in. holes are drilled into the
concrete wall where needed. The depth of these holes is determined by the
thickness of the concrete. The holes are drilled in a pattern that will avoid
making contact with the rebar. Anodes are placed in the %-in. holes and
packed with a mortar compatible with the EOP System.

4. Cathodes are installed. The cathodes may be placed around the exterior of
the building when conditions permit, or may be installed through the concrete
wall. Cathodes can be installed outside the structure by driving them into
the ground like an electrical ground rod or by installing through the wall in a
manner similar to the floor installation.

5. The EOP Control Unit is mounted in a location suitable to both the user and
the installer.



USACERL TR 98/68

4. Asecond EOP system was installed in Building 5 at McAlester during July
1996. A remote monitoring system, including a water table monitoring well,
was installed at the same time. The monitoring well was installed by the
Tulsa District, Corps of Engineers (COE) for the U.S. Army Construction
Engineering Research Laboratories (CERL).

5. Most data from the McAlester site is downloaded on a periodic basis to CERL
through a dedicated modem and phone line. The site is being monitored for
12 months (FY96-97) to validate seasonal water table levels. Life-cycle costs
and benefits will be calculated and technology transfer materials will be
completed during FY97.

Mode of Technology Transfer

AFEAP Ad Flyer and User Guide will be published, to be distributed through the
U.S. Army Center for Public Works (USACPW), Alexandria, VA. The user guide
will include specifications and procedures for equipment selection, procurement,
and use. The EOP technology will also be presented in CERL’s annual corrosion
and building technology courses and articles will be published in the USACPW’s
Public Works Digest, FEAP Bulletin, and related trade journals such as the
National Association of Corrosion Engineers’ (NACE’s) Materials Performance.
Lastly, the EOP technology will be presented by USACPW during site assistance
visits.



USACERL TR 98/68

Table 3. Location of rebar specimens.

Wall Depth to
Specimen #__| Location Back of Specimen

1 9 ft N of SW corner 7¥%in.
2 16 in. N of SW corner 7 Yin.
3 28 in. E of SW corner 7%in.
4 9 % in. E of SW corner 7%in.
5 16 in. W of SE corner 7¥%in.
6 12 ft N of SE corner 6 Bin.
7 15 % ft N of SE corner 6 win.
8 8 ft S of NE corner 4in.

9 6 ¥ ft W of NE corner 4in.

10 13 ft S of NW corner 4in.

Table 4. Specimen corrosion potentials.

Potential (Volts DC)
Specimen Minimum Maximum Average
3 -0.190 -0.200 -0.195
5 ~0.204 -0.224 0.214
9 0.145 0.154 0.15

The purpose of these specimens was to document whether any change occurs in
the native corrosion potential of steel rebar that might be embedded in a concrete
structure when the EOP system is operating. The corrosion potential of the
specimens was tracked and compared to the average corrosion potential for
reinforcing steel in concrete, which is approximately -0.2 VDC. Table 4 lists the
corrosion potentials for some of the specimens. These potentials were taken at
the 5-month performance check on 10 January 1995. The data show no
significant difference in the corrosion potential from the native potential for the
rebar specimens, however, these are just two time samples of a dynamic system.
A larger record is needed to fully document the EOP system effect on rebar
corrosion potential.

Monitoring Well

Another way to document the effectiveness of the EOP system is to track the
groundwater table outside the basement wall. This is accomplished by using a
monitoring well. The purpose of these measurements is simple: if the water
table is above the floor of the basement and the basement remains dry, then the
EOP system is fulfilling its purpose. Figure 9 shows the location of the
monitoring well relative to the basement.



TECHNICAL
REPORT

—
—, =
FEAP Technical Report 98/68 i EZ7I

FACILITIES ENGINEERING

April 1998
APPLICATIONS PROGRAM

Demonstration of Electro-Osmotic Pulse

Technology for Groundwater Intrusion
Control in Concrete Structures

by
Vincent F. Hock, Michael K. McInerney, and Erik Kirstein
U.S. Army Construction Engineering Research Laboratories
Champaign, IL 61826-9005

811 9001966)

Approved for Public Release; Distribution Is Unlimited.

U.S. Army Center Public Works

Alexandria, VA 22315-3862

Innovative Ideas for the Operation, Maintenance, & Repair of Army Facilities

Leco [OAMTTY INSPECTED 4



USACERL TR-98/68

the zeta potential*

the concentration of constituent i in free solution
the equivalents/mole of constituent i

Faraday’s constant

the universal gas constant

the absolute temperature.

When Eq 1 is integrated with the boundary conditions,

V=0 at y=0

x

Vi.=Vy at y>>0 [Eq 3]

x

The velocity V, is then obtained:

us [Eq 4]

Of the four independent variables in Eq 4, E, can be controlled to redirect the
movement of the solution. Figure 2 shows how E, can be controlled for this
purpose. Without electro-osmosis, the flux of species i consists of an advective
flux (J,) and a diffusive flux (J,).

Contaminated Liquid (Leachate)

dai Jai Jei

Figure 2. Arresting contaminant migration in an earthen landfill liner.

“The difference of potential between the plates of a hypothetical capacitor used to model the diffuse layer.



USACERL TR 98/68

Figure 1. Movement of cations in a soil pore by electro osmosis.

Electro-Osmotic Velocity

The velocity profile reaches a constant value (V,) a short distance from the
particle’s surface. To determine V,, a steady-state equation of motion is:

H e Pee Bye # =0
oy ¥ [Eq 11
where:

np = the viscosity of the solution
Vx = the velocity of the solution parallel to the particle surface
y = the distance orthogonal to the particle surface
E, = the externally applied electric field gradient
€ = the permitivity of the solution
= the electrical potential gradient.

By the Debye-Hiickel approximation, $ is written as:

_ 2n°Z?F2
Cc) | WRT

[Eq 2]



42 USACERL TR-98/68

Outdoor
AC AC DC Watts Rom | Room] Wall Wall Temp Outdoor RH
Date Volts_}| Amps _| (Computed) | Temp | RH Temp RH__| Well | Rainfall | (Average) |_ (Average)
3/8/97 | 209.65 { 0.10 11.95 89.46 | 23.22 | 77.13 | 90.06 |-14.90] 0.10 53.30 88.00
3/9/97 | 209.63 | 0.10 11.94 90.42 | 28.22 | 77.40 | 90.08 |-14.84} 0.21 59.90 78.00
3/10/97 | 209.31 0.10 1.91 90.39 | 20.64 | 77.51 90.11 |-14.84{ 0.00 54.70 60.00
3/11/97 _| 209.41 0.10 11.89 90.94 | 22.05 | 77.69 | 90.08 |-14.76| 0.00 58.80 64.00
3/12/97 | 209.33 | 0.10 11.87 91.65 | 2282 | 78.00 | 90.08 |-14.74| 0.58 56.50 77.00
3/13/97 | 209.37 | 0.10 11.90 91.74 | 28.85 | 7816 | 90.08 |-14.44] 0.52 57.60 93.00
3/14/97 | 209.50 | 0.10 11.79 89.32 | 18.24 | 77.78 | 90.06 |-14.94] 0.00 38.30 58.00
3/15/97 | 209.40 | 0.10 11.59 87.61 | 15.60 | 77.39 | 89.97 |-15.09} 0.00 39.20 50.00
3/16/97 | 209.50 | 0.10 11.08 87.34 | 18.89 | 77.13 | 89.79 |-14.93] 0.00 44.50 55.00
3/17/97 | 209.33 | 0.10 10.79 87.78 | 26.71 | 77.06 | 89.64 |-14.69} 0.00 57.10 85.00
9/18/97 _| 209.29 | 0.09 10.64 89.23 | 29.76 | 77.38 | 89.67 {-14.68} 0.00 58.70 83.00
3/19/97 | 209.14 | 0.09 10.51 88.52 | 21.44 | 77.38 | 89.74 |-14.89] 0.04 41.10 86.00
3/2097 | 209.12 | 0.09 10.15 88.21 | 21.52] 77.19 | 89.62 |-14.68| 0.00 52.50 65.00
9/21/97 | 209.65 | 0.09 10.25 90.49 | 2344 | 77.55 | 89.58 |-14.44] 0.00 68.70 46.00
3/22/97 | 209.74 | 0.09 10.18 91.56 | 1865 | 78.00 | 89.67 |-14.68| 0.00 57.50 45.00
3/23/97 | 209.73 | 0.09 10.13 91.88 | 18.19 | 78.24 | 89.62 |-14.70] 0.00 58.90 47.00
3/24/97 | 209.48 | 0.09 10.44 92.16 | 22.25 | 78.46 | 89.56 |-14.59] 0.00 68.20 54.00
9/25/97 | 209.66 | 0.10 11.45 91.86 | 24.44 | 78.36 | 89.50 |-14.71] 0.77 52.30 72.00
3/26/97 | 209.32 | 0.10 11.75 90.13 | 17.39 | 77.79 | 89.47 |-14.95| 0.00 49.40 59.00
3/27/97 | 209.34 | 0.10 11.13 91.25 | 21.62 | 7818 | 89.38 |-14.60} 0.00 61.60 57.00
3/28/97 | 209.83 | 0.10 10.83 92.32 | 23.67 | 78.67 | 89.42 |-14.41] 0.00 63.70 54.00
3/29/97 | 209.73 | 0.09 10.40 92.55 | 19.25 | 78.91 89.45 |-14.60] 0.15 62.10 49.00
3/30/97 | 209.81 | 0.09 10.29 92.62 | 18.49 | 79.16 | 89.44 |-14.91] 0.00 53.10 59.00
9/31/97 _| 209.33 | 0.09 10.06 91.88 | 16.44 | 79.11 89.35 |-14.97| 0.00 55.20 44.00
4/1/97} 209.39 | 0.09 9.98 92.03 | 1695 | 79.20 | 89.27 |-14.81] 0.00 62.20 37.00
4/2/97} 209.30 | 0.09 9.78 92.41 | 21.54 | 79.33 | 89.18 |-14.86] 0.00 65.90 49.00
4/3/97 _} 209.55 | 0.09 10.01 87.41 | 27.91 | 79.17 | 89.21 |-14.72| 0.09 65.70 46.00
4/4I97_| 210.12 | 0.09 9.80 79.47 | 47.66 | 77.78 | 89.06 |-14.32] 0.76 62.70 92.00
4/5/97 _| 210.04 | 0.09 9.39 7710 | 46.44 | 76.55 {| 88.92 |-14.29] 0.18 63.80 59.00
4/6/97_| 210.10 | 0.09 9.22 75.33 | 40.39 | 75.62 | 88.82 |-14.86] 0.00 51.40 47.00
4(7197_| 209.79 | 0.09 9.19 73.58 | 40.52 | 74.80 | 8872 |-15.03) 0.00 53.90 52.00
4/8/97_| 209.70 | 0.09 9.18 72.42 | 39.22 | 7413 | 88.62 |-14.98] 0.20 50.00 73.00
4/9/97_| 209.57 | 0.09 9.16 69.92 | 39.75 | 73.27 | 88.52 |-15.03] 0.00 49.60 80.00
4/10/97 | 209.61 | 0.09 9.17 69.60 | 40.38 | 72.66 | 88.33 |-14.75] 0.00 61.70 55.00
411/97 | 209.97 | 0.09 9.20 69.67 | 44.33 | 7232 | 88.28 |-14.63] 0.88 49.00 83.00
412/97 | 209.72 | 0.09 9.15 66.76 | 35.98 | 71.28 | 88.15 |-14.92} 0.00 35.90 68.00
4/13/97 | 209.91 | 0.09 9.17 65.20 | 35.03 | 70.58 | 88.03 |-14.98] 0.00 39.40 65.00
4/14/97 | 209.29 | 0.09 8.92 64.93 | 36.90 | 70.01 87.87 |-14.96] 0.00 47.70 57.00
4/15/97 | 209.70 | 0.09 8.72 65.80_| 38.30 | 69.80 | 87.75 |-14.91] 0.00 56.30 51.00
4/16/97 | 209.67 | 0.08 8.45 67.91 | 42.19 | 69.81 87.69 |-14.96] 0.04 52.40 83.00
4/17/97 _| 209.71 0.08 8.66 68.75 | 98.68 | 69.93 | 87.72 |-14.93} 0.00 55.90 62.00
4/18/97 | 210.03 | 0.08 8.32 68.37 | 44.40 | 69.86 | 87.75 |-14.67| 0.00 62.30 62.00
4/19/97 | 210.01 | 0.08 8.08 69.16 | 50.37 | 69.89 | 87.78 |-1453| 0.00 65.30 67.00
4/20/97 | 210.26 | 0.08 8.18 70.24 | 51.83 | 70.02 | 87.83 |-14.45| 0.02 68.90 69.00
4/21/97 | 209.92 | 0.08 8.23 71.24 | 50.80 | 70.23 | 87.95 |-14.44| 0.00 64.40 72.00
4/22/97 | 209.40 | 0.08 7.96 71.29 | 4585 | 70.36 | 88.06 |-14.55| 0.29 60.30 68.00
4/23/97 | 209.11 | 0.08 7.45 69.85 | 40.27 | 70.21 | 88.08 |-14.68| 0.00 53.50 71.00



USACERL TR-98/68

50 100

45

40 96
3° g
5 30 92 z
B25 Wall Humidity E
é A
= 0 ss 3
Fis 2

10 84

5 DC Power

0 80

November December January February March April

Month

Figure 15. Power consumption of EOP system in relation to relative humidity in the wall.

Depth (ft)

-10
“2 Basement Floor
“ NO PAA Ji TANI OT
-16 4

‘November December January February March April

Month

Figure 16. Water table with respect to the basement floor for McAlester AAP.



USACERL TR 98/68

6. The relative humidity within the 6-in. cavity of the east wall of the IHO
7. The level of the water table directly outside of the THO.

The EOP control Unit DC output power is being computed from the AC input
power and the known power consumption of the unit’s control electronics.

Rebar potentials are being sampled about every 4 months. Unfortunately they
could not be sampled remotely; they must be measured on site.

The daily rainfall, average outdoor temperature, and average outdoor relative
humidity at McAlester are obtained from the Oklahoma Climatological Survey
(Data is downloaded monthly from their INTERNET site). Sample data are
included in the Appendix to this report.

Figure 15 shows some of the recorded data, and highlights the power
consumption of the EOP system in relation to the relative humidity in the wall,
as measured by the wall probe. Figure 15 shows that, initially, as the power
consumption drops (as a result of the decrease in current as the water is driven
out), the concrete humidity drops as well. This shows that the EOP system is
decreasing the moisture content in the concrete and is decreasing its power
requirements, both excellent indicators that the system is working properly.
Figure 16 shows the water table with respect to the basement floor. (Figure 16
gives the same information for McAlester that Figure 12 gives for Fort Jackson.)
Unlike the conditions recorded at Fort Jackson the water table at McAlester AAP
does not rise above the basement floor. Therefore the water intrusion problem at
McAlester is due entirely to periodic saturation of the nearby soil. This
conclusion is further supported by the building’s occupants, who stated that the
water came in following rainstorms.



6 USACERL TR-98/68

osmosis has been used in civil engineering to dewater dredgings and other high-
water content waste solids, consolidate clays, strengthen soft sensitive clays, and
increase the capacity of pile foundations. It has also received significant
attention in the last 5 years as a method to remove hazardous contaminants from
groundwater or to arrest water flow.

A system has been developed to apply electro-osmotic pulse (EOP) technology
commercially within concrete structures by applying a pulsating electric field
combined with an off-period. The pulsating electro-osmotic sequence consists of
a pulse of positive voltage (as seen from the dry side of the concrete wall), a pulse
of negative voltage, and a period of rest when no voltage is applied. The pulse of
positive voltage has the greatest duration. The amplitude of the signal is
typically on the order of 20 to 40 volts DC. The electrical pulse causes cations
(e.g., Ca”) and associated water molecules to move from the dry side towards the
wet side against direction of flow induced by the hydraulic gradient, thus
preventing water penetration through buried concrete structures. Field testing
tests the feasibility and cost effectiveness of EOP technology, in comparison with
conventional (“trench and drain”) dampness mitigation techniques, at selected
Army installations.

Objective

The objective of this study was to demonstrate and document the effectiveness of
EOP technology to control groundwater intrusion in concrete structures at Fort
Jackson, SC and McAlester Army Ammunition Plant (AAP), OK.

Approach

1. In the summer of fiscal year 1994 (FY94), Bldg. #3265 at Fort Jackson, SC
was chosen as a candidate basement structure due to its history of water

seepage.
2. In August 1994, an EOP system was installed in the basement of Bldg. 3265.

3. The effectiveness of the installed EOP system was monitored over a 2-year
period (FY95-96), including the following parameters: (a) power supply
output, (b) effect of EOP on the corrosion potential of rebar, (c) concrete
moisture, (d) water table level, and (e) monthly rainfall.



20 USACERL TR-98/68

Figure 9 shows the basement mechanical room schematically, and highlights the
locations of the EOP Control Unit, anodes, and cathodes. Figure 10 shows Mr.
Cooper demonstrating the operation of the EOP control unit.

Continuaus Wiremold
Mounted 5° Above Floor _v— -

EOP Electrodes 18° OC

a a
2x2 r
8x8 Equi pment -
Equipment -
Pad 's

Anode Cable Around
Equipment Pad -

18’

Moni toring Well [L

LLEDP Control Unit

45" above Floor Ax
Equipment ft
Pad
| = T 1 + | TT T TT ’T 1 +t 1 TT T TT
LAL
x=——--—-- Cathodes ne

Figure 9. Layout of EOP installation at Fort Jackson.

Figure 10. Mr. Cooper demonstrating the operation of the EOP control unit.



USACERL TR 98/68

6 Conclusions and Recommendations

Based on the results of demonstrations and validations, this study concludes that
the application of EOP technology for control of water seepage in concrete
basement structures is an acceptable alternative to conventional trenching and
tiling.

The EOP technology installed in the mechanical room of Building 3265, Fort
Jackson, SC successfully prevented water seepage and reduced the relative
humidity of the concrete to 70 percent. The cost of installation has been
determined to be 40 percent lower than the cost of the conventional trench and
drain approach. The operating or energy cost of the EOP system is negligible —
equivalent to the expenditure of burning a 60W light bulb.

It is recommended that the EOP technology be transferred for Army-wide
implementation as a cost effective alternative to the “trench/drain” approach for
control of moisture in concrete basement structures. Technology transfer should
be facilitated through the publication of a FEAP user guide and ad flyer. Draft
EOP specifications should be prepared and submitted for incorporation into the
Corps of Engineers Guide Specifications.



38 USACERL TR-98/68

References

Hamill, W.H., R.R. Williams, and C. MacKay, Principles of Physical Chemistry, 2d ed. (Prentice-
Hall, Inc., Englewood Cliffs, NJ, 1966).

Glasstone, S., Textbook of Physical Chemistry, 2d ed. (D. Van Nostrand Company, Inc., Princeton,
NJ, 1946).

Tikhomolova, K.P., Electro-Osmosis (Ellis Horwood Limited, Chichester, West Sussex, England,
1993).

Means Cost Estimating Guides (R.S. Means Company, Inc., Construction Publishers and
Consultants, 100 Construction Plaza, P.O. Box 800, Kingston, MA 12364-0800).

Walker Estimating Guide (Frank R. Walker Company, Publishers, 5030 N. Harlem Ave., Chicago, IL
60656).

National Construction Estimator Handbook (Craftsman Book Company, 6058 Corte del Cedro, PO
Box 6500, Carlsbad, CA 92018-6500).



26 USACERL TR-98/68

i oe eZee
+ Anodes
a 20'-10° .
q 7 [ . | J Moni toring Weli * Cathodes
- TIN © EP Control Unit
i ond Detalagger

1
| § Room Temperature

K | and Humility
8] Sensors

® In-Wall Humidity
and Rebar
Corrosion
Potential
Sensors

cai!

7
|

a

Liz -art-—tor 4"

Figure 13. Basement of Building 5 at McAlester AAP.

Technicians then fastened a plastic wire mold onto the inside of the exterior
concrete walls of the rooms where the EOP system was to be installed. These
rooms are designated on Figure 13 as “A” (Industrial Hygiene Office), “B”
(Medical Supply Storage Room), and “C” (Electrical Room). This wire mold was
mounted 5 in. above the floor and conceals the anodes and system wiring.
Junction boxes were placed every 15 ft along the wire mold. Holes were then
drilled through this wire mold and into the concrete walls. These holes, to
accommodate the anodes, were drilled 6 in. into the concrete walls, 5 in. above
the floor and 11 in. on center. The total number of anodes is 95 and the number
of anodes for each wall is: 20, 15, 24, 9, 19, and 8, respectively, starting with the
east wall in room A, and moving clockwise around the basement. Rubber-
graphite anodes were coated with a graphite-mortar mixture and inserted into
the holes. The anodes were wired in segments of about 20 anodes. The segments
were then connected in a parallel and redundant manner (connected at both
ends) to the power supply. All wiring was enclosed in the wire mold.

Copper-clad steel grounding rods (cathodes), 8 ft long, were driven into the
ground in selected areas. This project required five cathodes and they were
placed as indicated in Figure 13. Wiring from the cathodes was installed and
placed in the wire mold. To differentiate the wires, blue wire connected the
anodes and black the cathodes. The covering for the wire mold was then secured

in place.



USACERL TR-98/68

Foreword

This study was conducted for U.S. Army Center for Public Works (USACPW)
under the Facilities Engineering Application Program (FEAP); Work Units FM-
F95 and FL-F96, “A Demonstration of Electro-Osmotic Pulse (EOP) Technology
for Control of Seepage in Concrete Structures.” The technical monitors were
Fidel Rodriguez, CECPW-EB and Malcolm McLeod, CECPW-ES

The work was performed by the Materials Science and Technology Division
(FL-M) of the Facilities Technology Laboratory (FL), U.S. Army Construction.
Engineering Research Laboratories (CERL). The CERL principal investigator
was Vincent F. Hock. The contributions of the following CERL personnel are
gratefully acknowledged: Hannon Maase and Henry Cardenas. The assistance
provided by Frank Cooper, ATZJ-PWO, Fort Jackson, SC; Gary Reasoner,
SIOMC-DEO, McAlester Army Ammunition Plant; Dr. Charles Lozar of
Architects Equities Research Group; and Roger Hayes, Arild Ottersen, Egil
Bjerke, and Micheal Connor, Drytronic (formerly know as Dry-Tec of North
America), was essential to the successful completion of this work. Dr. Ilker R.
Adiguzel is Acting Chief, CECER-FL-M; Larry M. Windingland is Acting
Operations Chief, CECER-FL; and Dr. Alan W. Moore is the responsible
Technical Director, CECER-TD. The CERL technical editor was William J. Wolfe,
Technical Resources.

COL James A. Walter is Commander and Dr. Michael J. O’Connor is Director of
CERL.



USACERL TR 98/68
Outdoor

AC AC DC Watts Rom | Room} Wall Wall Temp Outdoor RH

Date Volts | Amps | (Computed) | Temp | RH Temp RH__| Well _| Rainfall | (Average) | __ (Average)
4/24/97 | 209.38 | 0.08 7.38 68.40 | 41.62 | 69.87 | 88.09 |-14.79] 0.09 51.60 76.00
4/25/97 | 209.71 | 0.08 7.16 67.71 | 45.50 | 69.70 | 88.08 |-14.92] 0.64 51.50 85.00
4/26/97 | 209.84 | 0.07 6.64 66.83_| 50.35 | 69.38 | 88.05 |-1487] 0.26 52.00 92.00
427/97 _| 209.78 | 0.07 6.30 66.51 | 50.45 | 69.12 | 87.98 }-1473] 0.05 54.00 81.00
4/28/97 | 209.41 | 0.07 6.10 66.92 | 48.88 | 68.97 | 87.98 |-14.65] 0.00 57.20 65.00
4/29/97 _| 209.31 | 0.07 6.09 67.76 | 54.01 | 68.95 | 88.03 |-14.66] 0.00 65.30 66.00
4/30/97 | 209.18 | 0.07 6.07 68.80 | 54.62 | 69.08 | 88.10 |-1460} 0.00 65.10 65.00



USACERL TR 98/68

13

Pre-Installation Site Inspection

Two sites were selected for the EOP technology demonstration: (1) Fort Jackson,
SC and (2) McAlester AAP, OK. In both cases, the location of the groundwater
intrusion was through the floor and walls of the poured concrete basements. The
EOP system was installed in Building 3265 at Fort Jackson and Building 5 at
McAlester.

Groundwater intrusion into basements leads to various problems, including
concrete degradation, rebar corrosion, and personal health and safety hazards.
Also, because of the high humidity conditions associated with ever present
standing water, corrosion of peripheral building mechanical equipment, pumps,
boilers, and associated systems is accelerated, minimizing the opportunities for
extending the useful life of those facilities. Lastly, current management practices
for the disposal of standing or subterranean water raises additional
environmental concerns. For instance, water pumped from a sump pit in a
mechanical room often has to be treated as “mixed waste” because of oil
droppings and lubricants mixing with water from the mechanical systems.

Building 3265, Fort Jackson

Building 3265 had a history of water seepage into the concrete basement
mechanical room. The mechanical room had experienced water levels within the
structure as high as 14 in.” On the average, there existed about 2 in. of standing
water. In addition, there was seepage from cracking in the wall, efflorescence,
and poor air quality as a result of the high indoor humidity. This seepage
initiated corrosion of the mechanical equipment located in the basement. Figure
5 shows the standing water in the basement mechanical room before the EOP
system installation.

“4 in, = 25.4 mm; 1 ft= 0.304 m.



USACERL TR 98/68

15

Figure 6. Standing water in basement of Building 5, McAlester AAP.


REPORT DOCUMENTATION PAGE Te eset 188

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources,
gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this,
collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for information Operations and Reports, 1215 Jefferson
Davis Highway, Suite 1204, Arlington, VA 22202-4302, and to the Office of Management and Budget, Paperwork Reduction Project (0704-0188), Washington, DC 20503.

1. AGENCY USE ONLY (Leave Blank) | 2. REPORT DATE 3. REPORT TYPE AND DATES COVERED
April 1998 Final
4. TITLE AND SUBTITLE 5. FUNDING NUMBERS
Demonstration of Electro-Osmotic Pulse Technology for Groundwater Intrusion FEAP
Control in Concrete Structures FM-F95 and FL-F96
6. AUTHOR(S)

Vincent F. Hock, Hannon T. Maase, Michael K. McInerney, and Erik Kirstein

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION
U.S. Army Construction Engineering Research Laboratories (USACERL) REPORT NUMBER
P.O. Box 9005 TR98/68

Champaign, IL 61826-9005

9. SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSORING / MONITORING
U.S. Army Center for Public Works (USACPW) AGENCY REPORT NUMBER
ATTN: CECPW-EB
7701 Telegraph Road
Alexandria, VA 22312-3862

11. SUPPLEMENTARY NOTES
Copies are available from the National Technical Information Service, 5285 Port Royal Road, Springfield, VA 22161.

12a. DISTRIBUTION / AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE

Approved for public release; distribution is unlimited.

13. ABSTRACT (Maximum 200 words)
Groundwater intrusion through a building's foundation (i.e., a "wet basement problem") can cause serious damage that is
expensive to correct. In older buildings, such as those common on U.S. Army installations, severe damp-basement
problems call for immediate action to mitigate water damage. Electro-osmotic pulse (EOP) technology offers an alternative
to the "trench and drain" approach that can mitigate some water-related problems from the interior of affected areas
without the cost of excavation. The EOP alternative can further mitigate corrosion damage to mechanical equipment along
with humidity and mold problems.

This study demonstrated and document the effectiveness of EOP technology to control groundwater intrusion in concrete
structures at Fort Jackson, SC and McAlester Army Ammunition Plant (AAP), OK. The cost of installation was determined
to be 40 percent lower than the cost of the conventional trench and drain approach. The operating or energy cost of the
EOP system was shown to be negligible — equivalent to the expenditure of burning a 60W light bulb.

14, SUBJECT TERMS 15. NUMBER OF PAGES
electro-osmotic pulse technology maintenance and repair 44
groundwater building maintenance 76. PRICE CODE
concrete structures
17. SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION 19. SECURITY CLASSIFICATION 20. LIMITATION OF
OF REPORT OF THIS PAGE OF ABSTRACT ABSTRACT
NSN 7540-01-280-5500 Standard Form 298 (Rev. 2-89)

Prescribed by ANSI Std 239-18
298-102



USACERL TR-98/68

Table 8. Calculation of EOP System Based on Installed Costs and If of Wall.

Location Linear Feet installed Cost per Linear Foot
McAlester AAP 95 $190.22
Fort Jackson 113 $186.75
Average Cost of EOP Installation for Both Sites $188.49

Payback for EOP Technology

The percent savings based on capital costs is basically a comparison between the
cost of trenching, damp-proofing, backfilling, and installed EOP technology. The

comparison is:

EOP per If } 100 ( #18849)
= 100

% first cost saved = 100 x | 1 - ———~—— 1-
Trench & Drain per If $315.20

Payback is based on a calculation of time taken to recoup the original
investment. One can determine how long it would take to save investment

moneys for EOP over a comparable spending for a trench and drain system. This
is called Payback Upon Price Comparison (Ppc):

1 1 1
Pre = French & Drain per if BOP per if = $126.71 ~ o@7 = “497°”
EOP per lf $188.49

This is an internal return on investment, based solely on initial costs. It does not
represent the savings over time.

One might also consider some intangible (certainly difficult to quantify) benefits:

1. There is minimal disruption of the building activity during the drying out
process, e.g., no digging, minor noise, and a small amount of waste.

2. Illnesses caused by allergies or other sensitivities will be reduced, thereby
increasing health and productivity of the building occupants.

In summary, both the economic benefits based on conservative estimates from
field data, and the intangible benefits, point to a very positive return-on-
investment for EOP technology.



24 USACERL TR-98/68

Each month, Davis & Floyd (the contractor responsible for monitoring the water
table) reported the results of the water table data relative to the basement floor.
Also recorded was the groundwater temperature. (Groundwater temperature
was included in the standard monitoring well “package,” it was not needed for
this particular study.) Figure 12 shows the hydrograph from Davis & Floyd. The
results for the monitoring well began in September 1995 and ended in September
1996. Note there are several times during the recording period when the water
table exceeded the basement floor level, yet because of the EOP system the
basement remained dry.

Rainfall data were taken monthly at Fort Jackson to track the months when
there would be a greater potential for a higher water table. These data can be
correlated to the monitoring well data points, as greater rainfall would result in
a higher water table. (Specifically, note the correlation between the high rainfall
during March 1996 and the rise in the water table during that month.) Table 5
shows the rainfall data at Fort Jackson up to May 1996.

Water Level, Ft.

i

g

joraug.26 #

13-Sep-95.
14-0ct95 |
14-Nov-95
5-Dec 95 |

15-Jan-96
15-Feb-96
17-Mar-96
17-Apr-96
May-96
Jun-96
19-Jul-96

Date of Measurement

Figure 12. Hydrograph line from monitoring well Fort Jackson.



The contents of this report are not to be used for advertising, publication,
or promotional purposes. Citation of trade names does not constitute an
official endorsement or approval of the use of such commercial products.
The findings of this report are not to be construed as an official

Department of the Army position, unless so designated by other authorized
documents.

DESTROY THIS REPORT WHEN IT IS NO LONGER NEEDED

DO NOT RETURN IT TO THE ORIGINATOR



32 USACERL TR-98/68

Figure 17. Dry floor in basement of building 3265, Fort Jackson, following
EOP application.

Figure 18. Dry floor in basement of Building 5, McAlester AAP, following EOP
application.



USACERL TR 98/68 41
Outdoor
AC AC DC Watts Rom | Room} Wall Walt Temp Outdoor RH
Date Volts_| Amps | (Computed) | Temp RH Temp RH __| Well | Rainfall | (Average) | (Average)
1/20/97 | 209.54 | 0.11 14.39 82.31 | 23.67 | 70.95 | 91.88 |-15.09} 0.00 50.60 77.00
1/21/97 | 209.46 | 0.11 14.44 84.78 | 32.36 | 71.97 | 92.00 |-14.90] 0.01 60.60 88.00
1/22/97 | 209.41 | 0.11 14.49 86.04 | 2450 | 72.75 | 9218 |-14.98] 0.00 52.70 62.00
1/23/97 | 209.23 | 0.11 14.49 85.93 | 21.26 | 73.22 | 92.28 }-15.03| 0.00 50.90 67.00
1/24/97 | 209.62 | 0.11 14.70 86.68 | 24.00 | 73,71 92.30 |-14.94] 0.00 50.00 73.00
1/25/97 | 209.42 { 0.11 14.47 85.33 | 16.21 | 73.77 | 92.33 |-15.39| 0.00 34.60 65.00
1/26/97 | 209.49 | 0.11 14.42 85.26 | 20.68 | 73.82 | 92.19 |-15.09] 0.00 54.00 58.00
1/27/97 | 209.17 | 0.11 14.39 85.57 | 2219 | 74.18 | 92.15 |-15.24| 0.00 39.50 77.00
1/28/97 | 209.04 | 0.11 14.34 81.74 | 1242 | 73.47 | 92.07 |-15.74] 0.00 18.10 59.00
1/29/97 | 209.16 | 0.11 14.32 80.99 | 12.78 | 7298 | 91.80 |-15.49} 0.00 30.10 49.00
1/30/97 | 209.10 | 0.11 14.25 81.69 | 15.37 | 7297 | 91.63 |-1532} 0.00 40.20 45.00
4/31/97 | 209.52 | 0.11 14.25 83.37_| 17.67 | 73.30 | 91.58 |-14.94} 0.00 52.00 34.00
2/97 | 209.55 | 0.11 14.18 84.41 | 19.62 | 73.63 | 91.52 |-14.88] 0.00 52.50 53.00
2/2/97 | 209.52 | 0.11 14.12 85.77_| 20.80 | 73.98 | 91.48 |-15.04] 0.00 53.80 55.00
2/3/97 _| 209.30 | 0.11 14.17 87.32_| 25.45 | 74.65 | 91.53 |-15.07] 0.61 53.40 87.00
2/4/97 _| 209.19 | 0.11 14.26 87.72 _| 20.40 | 75.09 | 91.67 |-1537| 0.00 45.80 67.00
25/97 _| 209.19 | 0.11 14.22 86.70 | 16.57 | 75.11 91.62 |-15.61] 0.00 40.60 64.00
es7_| 209.22 | 0.11 14.09 86.04 | 19.82 | 75.09 | 91.52 |-1542] 0.53 39.70 92.00
27i97_| 209.55 | 0.11 13.85 85.11 | 19.98 | 74.87 | 91.42 |-15.31] 0.71 36.40 93.00
297 _| 209.37 | 0.11 13.34 84.28 | 17.80 | 74.63 | 91.31 [-1551] 0.00 34.20 81.00
29/97_| 209.53 | 0.11 13.04 83.69 | 17.51 | 74.43 | 91.20 |-15.41] 0.00 35.50 77.00
210/97 | 209.02 | 0.10 12.70 83.71} 18.11 74.36 | 91.09 |-15.37] 0.00 37.30 75.00
211/97 | 209.13 | 0.10 12.51 83.71 | 17.94 | 7428 | 90.99 |-15.21] 0.00 39.80 72.00
22/97 | 209.11 0.10 12.37 84.61 | 18.84 | 74.47 | 90.88 |-15.07] 0.05 41.30 72.00
23/97 | 209.09 | 0.10 12,20 84.21 | 19.28 | 74.45 | 90.86 [-14.99] 0.22 37.10 88.00
24/97 | 209.47 | 0.10 12.18 84.60 | 19.54 | 74.52 | 90.78 |-15.16] 0.00 40.20 79.00
215/97 | 209.52 | 0.10 12.02 84.91 _| 18.04 | 74.60 | 90.73 |-15.25| 0.00 44.90 62.00
26/97 | 209.56 | 0.10 11.97 85.95 _| 17.87 | 74.90 | 90.68 |-15.34} 0.00 47.90 56.00
2/17/97 | 209.68 | 0.10 12.01 86.83 | 18.31 | 75.19 | 90.68 |-15.20} 0.00 56.60 45.00
218/97 _| 209.33 | 0.10 11.96 88.07_| 22.57 | 75.67 | 90.68 |-14.98} 0.00 58.00 64.00
2/19/97 _| 209.51 0.10 12.04 89.28 | 27.65 | 76.18 | 90.70 |-14.95| 0.39 60.60 83.00
2/20/97 | 209.46 | 0.10 12.15 89.96 | 32.02 | 76.56 | 90.78 |-14.56] 1.88 61.90 92.00
2/21/97 | 209.66 | 0.10 12.10 89.29 | 23.92 | 76.48 | 90.85 |-14.68] 0.06 46.60 84.00
2/22/97 | 209.62 | 0.10 11.99 87.88 | 18.90 | 76.30 | 90.82 |-15.23] 0.00 41.30 73.00
2/23/97 | 209.72 | 0.10 11.98 87.53 | 17.02 | 76.24 | 90.72 |-15.28} 0.00 46.80 56.00
2/24/97 | 209.17 | 0.10 11.92 87.89 | 17.12 | 76.32 | 90.62 |-15.25| 0.00 51.80 46.00
2/25/97 | 209.27 | 0.10 11.93 88.11 | 20.41 76.47_| 90.55 |-14.96| 0.27 48.30 76.00
2/26/97 | 209.19 | 0.10 11.92 88.61 | 23.75 | 76.50 | 90.48 |-14.41| 0.73 47.40 91.00
2/27/97 | 209.41 | 0.10 11.94 87.86_| 20.88 | 76.27 | 90.39 |-14.65| 0.00 44.90 72.00
2/28/97 | 209.75 | 0.10 11.98 88.11 | 23.84 | 76.29 | 90.34 |-14.54] 0.00 50.80 88.00
1/97 _| 209.70 | 0.10 11.97 89.54 | 28.73 | 76.62 | 90.34 |-14.60} 0.00 58.70 84.00
3/2/97 _| 209.69 | 0.10 11.97 88.66 | 20.54 | 76.67 | 90.38 |-1478| 0.17 42.40 78.00
9/3/97_| 209.33 | 0.10 11.93 88.71 | 20.72 | 76.56 | 90.32 |-14.64| 0.00 50.30 67.00
3/4/97 _| 209.36 | 0.10 11.93 90.50 | 23.02 | 77.02 | 90.28 |-14.66| 0.00 62.70 54.00
5/97 _| 209.20} 0.10 14.91 89.54 | 17.94 | 77.12 | 90.33 |-15.03] 0.00 42.50 62.00
6/97 _| 209.23 | 0.10 11.91 88.54 | 16.58 | 76.91 90.22 |-15.19| 0.00 46.30 53.00
7/97_| 209.50 | 0.10 11.94 88.76 _| 17.55 | 76.95 | 90.12 |-14.96} 0.00 50.80 50.00



USACERL TR 98/68

Drytronic technicians drilled holes at several places in the basement walls for
sensors: holes were drilled perpendicular to the wall surface in three different
locations to accommodate 6-in. long rebar specimens; a horizontal groove
measuring 16 in. long by 1.5 in. deep was chiseled 8 in. above the floor into the
south wall of the Industrial Hygiene Office to hold a long steel rebar specimen; a
hole was drilled at a 45 degree angle downward into the wall behind this groove
for a corrosion reference cell; and finally a hole was drilled in the south wall near
the southeast corner of the Industrial Hygiene Office to accommodate a
temperature and humidity sensor. The rebar specimens were used by CERL to
monitor rebar corrosion potential and the temperature and humidity probe was
used to monitor moisture in the concrete wall. Finally, the EOP Control Unit
was mounted on the north wall of the electrical room (labeled “C” in Figure 13).
The relative humidity in the Industrial Hygiene Office was 70 percent at this
time. The installation portion of this project was completed on 31 July 1996.

The EOP waveform was recorded by an oscilloscope on several occasions. The
oscilloscope provides a real-time picture of the waveform and shows the
maximum, average, and minimum voltage values and the point at which the
voltage goes to zero. Figure 14 shows a waveform taken from the EOP unit at
McAlester AAP, November 1996. The normal operating voltage range, peak to
peak, is ~60 Volts DC (VDC). The positive voltage peak was =30 VDC. During
the positive pulse, the water is forced in the direction of the cathode or to the
exterior surface of the concrete.

Monitoring System

Many of the same parameters that were recorded at Fort Jackson are being
recorded at McAlester. The corrosion potential is taken using a 13-in. long piece
of 0.5-in. steel rebar that was grouted into the wall along with a Ag/AgCl
reference cell. The cell was installed so as to be behind the rebar, and separated
from it by about 2 in. of concrete. The humidity of the concrete is sampled, but
not with the same technique used at Fort Jackson. A small cavity
(approximately 6-in. long) was made in the concrete wall for the insertion of a 4-
in. long dual humidity/temperature probe. After the probe was inserted into the
cavity, the cavity was sealed off from the room air. Since the cavity is sealed, this
probe monitors the temperature and humidity of the cavity, giving an indication
of the progress of the EOP system as it operates. The humidity of the cavity
should be proportional to the moisture content of the concrete.



USACERL TR 98/68

Both of these fluxes drive contaminants downward. An electro-osmotic flux (J,)
can be applied to counter these fluxes:

Jei = ne VoCi* ne ne Ex [Eq 5]

where C, is the concentration of constituent i, and n, is the effective soil porosity.

To stop or reverse the movement of constituent i, E, is adjusted so that:
Jaz Sait Sai [Eq 6]

Pulsating Electro-Osmosis

The pulsating electro-osmotic technique consists of a positive voltage pulse, a
negative voltage pulse, and a period when no voltage is applied. Figure 3 shows
an example waveform for the pulsating electro-osmotic pulse or EOP system. The
positive voltage pulse has the longest interval and the negative voltage pulse has
the shortest interval. As a result of this, the pore fluid moves (on the average) in
one direction.

Currently, the reasons for the increased performance of the EOP system over
standard DC electro-osmosis for drying concrete are not well understood.
However, it is speculated that the change in polarity results in the reversal of
some of the chemical reactions occurring during electrolysis. It is also believed
that the rest phase (no applied voltage) allows the system to equilibrate. As a
result of these effects, undesirable side effects such as acid production and
increased corrosion are avoided. Also, use of a pulse sequence might prevent the
concrete from becoming too dry.

An EOP system is realized by inserting anodes (positive electrodes) into the
concrete wall or floor on the inside of the structure and by placing cathodes
(negative electrodes) in the soil directly outside the structure. The density of the
anode and cathode placement is determined from an initial resistivity test of the
concrete and soil. The objective is to achieve a certain current density in the
concrete. Figure 4 illustrates the EOP process.



14 USACERL TR-98/68

Figure 5. Standing water in basement of Building 3265, Fort Jackson.

Building 5, McAlester AAP

The basement of Building 5 had standing water in several areas. Problems
similar to the basement at Fort Jackson were prevalent: water seepage from
cracking in the wall, efflorescence, and high indoor humidity (70 percent). The
reduction of the indoor air humidity through the EOP system is very important,
as one of the rooms is the Industrial Hygiene Office, occupied by an individual 40
hours a week. Standing water can be seen in one of the corners of the office
(Figure 6).