Benefits of Using High-Frequency ForcedPulsed 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

(FPWJ) 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

Works Canada (PWC) was getting the job done by employing

a chipper (hammer & chisel), sandblaster, at a cost of

$40/sq.ft. With 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

only necessary to isolate working areas one at a time.

Before taking the R&D contract work for the PWC,

laboratory tests were conducted on several types of concrete.

Sample results on cutting with FPWJ and the corresponding

continuous waterjet (CWJ) are illustrated in Fig. 2. While

FPWJ removed 0.283-m /hr of hard concrete (not3

deteriorated), CWJ removed only 0.037-m /hr after four3

adjacent passes, both operating at identical conditions

(20,000-psi and power). In other words, to remove 1-m of3

concrete, FPWJ took only 3.5-hrs, compared to 27-hrs by the

CWJ. At a nominal wage of $25/hr, the contractor employing

the ubiquitous CWJ pays $675, and a visionary contractor,

who would use FPWJ, pays only $87.5 for the job of

removing 1-m of concrete. The savings does not end here!3

Savings in cost of Energy Consumption:

Total energy consumed by FPWJ: 387-kW.hr

Total energy consumed by CWJ: 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,

GST, etc), the contractor would save a staggering $6,800 to

remove 1-m of concrete! AND,3

Abatement of Pollution (Based on the Data Provided by

CANMET)

2According to CANMET (a Department of Government of Canada), based on diesel fuel, CO loading of the environment is: 71-

kg/GJ of energy comsumption. Therefore:

2CO emission by the use of FPWJ: 99,000-kg

2CO emission by the use of FPWJ: 636,400-kg (staggering!)

This reduction, resulting by using FPWJ, 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 removing hard coatings of paints.

Prepared by: Mohan Vijay, Ph.D., P.Eng., President, VLN Advanced Technologies, Ottawa, Canada (www.VLN-Tech.com).

Fig. 1. Refurbishing of delaminated (deteriorated) concrete from the

ceilings of underground multi-story buildings.

(A) Usual appearance of the ceiling with loose concrete and rusted

steel bars.

(B) VLN’s forced pulsed waterjet (FPWJ) at the underground

parking garage of External Affairs Building (Lester B Pearson) for

refurbishing delaminated concrete.

(C) FPWJ in the process of removing and cleaning the steel bars.

(D) Appearance of the refurbished delaminated area, showing the

clean steel bars.

Fig. 2. These results clearly show the benefit of using FPWJ

compared to continuous waterjet (CWJ), both operating at identical

operating conditions (pressure, power, etc).