1. Benefits of Using High-Frequency Forced
Pulsed Waterjet for Refurbishing Delaminated
Concrete Structures
Figure 1 shows the photographs of the work done on
refurbishing the delaminated (deteriorated) concrete ceiling,
using VLN’s patented high-frequency forced pulsed waterjet
(FPW J) machine. The location was underground parking
garage, Lester B Pearson Building, Ottawa. The success of
the job is quite evident from the photographs.
Prior to awarding this contract to VLN, Public
W orks Canada (PW C) was getting the job done by employing
a chipper (hammer & chisel), sandblaster, at a cost of
$40/sq.ft. W ith the employment of VLN’s machine,
sandblasting was eliminated, and as removing the deteriorated
concrete was so fast (see Fig. 2), the cost was reduced to
about $10/sq.ft! Furthermore, there was no need to shut the
entire parking garage because, as shown in Fig. 1 (C), it was Fig. 1. Refurbishing of delaminated (deteriorated) concrete from the
only necessary to isolate working areas one at a time. ceilings of underground multi-story buildings.
(A) Usual appearance of the ceiling with loose concrete and rusted
Before taking the R&D contract work for the PW C, steel bars.
laboratory tests were conducted on several types of concrete. (B) V LN’s forced pulsed waterjet (FPW J) at the underground
Sample results on cutting with FPW J and the corresponding parking garage of External Affairs Building (Lester B Pearson) for
continuous waterjet (CW J) are illustrated in Fig. 2. W hile refurbishing delaminated concrete.
FPW J removed 0.283-m 3/hr of hard concrete (not (C) FPW J in the process of removing and cleaning the steel bars.
deteriorated), CW J removed only 0.037-m 3/hr after four (D) Appearance of the refurbished delaminated area, showing the
adjacent passes, both operating at identical conditions clean steel bars.
(20,000-psi and power). In other words, to remove 1-m 3 of
concrete, FPW J took only 3.5-hrs, compared to 27-hrs by the
CW J. At a nominal wage of $25/hr, the contractor employing
the ubiquitous CW J pays $675, and a visionary contractor,
who would use FPW J, pays only $87.5 for the job of
removing 1-m 3 of concrete. The savings does not end here!
Savings in cost of Energy Consumption:
Total energy consumed by FPW J: 387-kW.hr
Total energy consumed by CW J: 2,490-kw.hr!
At the rate of $3.25/kW .hr (based on the rate charged
to VLN by Ottawa Hydro, which includes delivery charge, Fig. 2. These results clearly show the benefit of using FPW J
GST, etc), the contractor would save a staggering $6,800 to compared to continuous waterjet (CW J), both operating at identical
remove 1-m 3 of concrete! AND, operating conditions (pressure, power, etc).
Abatement of Pollution (Based on the Data Provided by
CANM ET)
According to CANMET (a Department of Government of Canada), based on diesel fuel, CO 2 loading of the environment is: 71-
kg/GJ of energy comsumption. Therefore:
CO 2 emission by the use of FPW J: 99,000-kg
CO 2 emission by the use of FPW J: 636,400-kg (staggering!)
This reduction, resulting by using FPW J, must make any environmentalist happy (how about the proponents of Kyoto?)
Note: These results apply to all applications VLN has investigated, ranging from cutting rocks to rem oving hard coatings of paints.
Prepared by: M ohan Vijay, Ph.D., P.Eng., President, VLN Advanced Technologies, Ottawa, Canada (www.VLN-Tech.com).