Comparison of the actual costs during removal of concrete layer by high-speed water jets.
Hela, Rudolf ; Bodnarova, Lenka ; Novotny, Miloslav 等
1. Introduction
Renovation of concrete structures represents a great part of total
turnover of construction industry worldwide. Removal of degraded surface
and preparation of surface for renovation materials are very important.
As cost of energy and the input of materials grow, it is necessary to
look at ways of decreasing cost of removal of degraded concrete.
Therefore, it is necessary to choose an optimal and cost effective way
of removal of disrupted layers of concrete. The first step towards this
goal is to specify the cost of possible ways and technologies of
concrete removal for purposes of renovation.
Various types of concrete removal methods can be used. As removal
of degraded layers of concrete is costly and ecological aspects are
becoming more important than ever before, new technologies with low
environmental impact are being developed. Driven by cost, need, and
limited resources, the technology for concrete removal is rapidly
advancing. Partial removal of critical structural components for repair
rather than replacement, geographical constrains, access to structures
planned for removal, environmental regulations, and worker and structure
safety will continue to effect an evolution of developing methods and
equipment (ACI 555R-01 2001). ACI 555R-01 Removal and Reuse of Hardened
Concrete state these basic methods for removal hardened concrete:
* hand tools;
* hand-operated power tools;
* vehicle-mounted equipment;
* explosive blasting;
* drills and saws;
* nonexplosive demolition agents;
* mechanical splitters;
* heating and thermal tools;
* and hydrodemolition (water-jet blasting).
Total cost of removal of hardened concrete can be sumarized as
costs for removal method, partial or complete concrete removal, reuse,
transportation and waste disposal, and additional inspection and testing (ACI 555R-01 2001).
This paper describes the process of possible evaluation of costs of
hydrodemolition--using high speed water jet technology for concrete
removal methods.
2. Background
2.1. Research of high speed water jet technology--cooperation of
important institutions and practical use supported by the Government
Authors have been researching, developing and improving high speed
water jet technology for destruction and removal materials for purposes
of renovation of concrete structures for a long time. Research
institutions the Brno University of Technology, Faculty of Civil
Engineering and the Institute of Geonics AS CR, v. v. i. closely
cooperate on solving tasks in the research of high speed water jets,
interaction with concrete and evaluation of effectiveness of this
technology. Many companies focusing on the development of high speed
water jet technology cooperate in practical tests of disintegration of
various types of material as well as concrete (in particular the Company
NET Ltd.). The financial support of the Government, grants as well as
checking effectiveness of funding and fulfillment of targets are also
very important. Problems for research of high speed water jets have been
solved with the support of funding granted by Czech Science Foundation,
by the Academy of Sciences of the Czech Republic and by Research and
Development for Innovations Operational Program financed by Structural
Funds of the European Union and from the means of state budget of the
Czech Republic. This scheme of cooperation of the University, research
institutions, industrial companies and government follows the Triple
helix model.
The Triple helix model is the model of collaboration among
business, government and academic actors. The key event is the creation
of an entrepreneurial university, whether from an existing academic base
or a new foundation, which takes initiatives together with government
and industry in creating a support structure for firm formation,
regional growth and increasing the competitive advantage of economic
development (Etzkowitz, Klofsten 2005).
'Triple helix' model indicates a relationship among
academic authorities, industry and authorities as a merger of
overlapping areas reflecting an impact of each element on other spheres.
There are three main the most common configurations of the 'Triple
helix' model: in the first model the areas indicating elements of
the industry and academic public exist independently, without any
interaction, and the dominant role of an intermediary is played by the
authorities being the only element ensuring relations between the
sectors; the second model shows interactive relations of different
elements; the third model indicates close cooperation among separate
institutions of science, business and government (Chlivickas et al.
2009).
Mentioned subjects (Faculty of Civil Engineering, Brno University
of Technology, Institute of Geonics AS CR, v. v. i., and NET Ltd.)
strive to create the third type of Triple helix model for effective
cooperation and to reach innovation in the field of water jet. The third
model of 'Triple helix' is the most successful model for high
technologies development. This type of Triple helix model shows the
highest degree of cooperation among authorities, industry and academic
public as the configuration of 'Triple helix' model allows
solving all problems in implementation of innovations (Chlivickas et al.
2009).
During solving the problems of high speed water jet technology, the
research team registered the following national and international
patents:
* Foldyna, J. and Svehla, B.: Method of generation of pressure
pulsations and apparatus for implementation of this method. Czech patent
No. 299412, 2008.
* Foldyna, J. and Svehla, B.: Method of generation of pressure
pulsations and apparatus for implementation of this method. US patent
No. 07740188, 2010.
* Foldyna, J. and Svehla, B.: Method of generation of pressure
pulsations and apparatus for implementation of this method. EU patent
EP1863601, 2011.
* Bortolussi, Ciccu, Foldyna, Sitek: Treatment process of
materials, in particular stones, using pulsating jet technology and
apparatus to obtain that process. PCT Patent Application No.
PCT/IT2009/000184.
Results of the patents are currently used on the basis of licensed
cooperation between industrial party and the Institute of Geonics ASCR,
v. v. i. in Ostrava.
The research was supported by state budget of the Czech Republic
and from the European Union. In particular, the following projects were
realized:
* Development of novel technique for quarrying and cutting of
ornamental stones (GA CR No. 105/03/0183, evaluated as excellent).
* Novel technique for cleaning and removal of surface layers and
repair of concrete structures (ASCR No. 1QS300860501, evaluated as
excellent).
* Study of the process of generation and propagation of pressure
pulsations in high-pressure system (GA CR, No. 101/07/1451).
* Modelling of the disintegration process of degraded layer of
construction materials during their preparation for repair action (GA CR
No. 103/07/1662).
* Institute of clean technologies for mining and utilization of raw
materials for energy use, reg. No. CZ.1.05/2.1.00/03.0082 supported by
Research and Development for Innovations Operational Programme financed
by Structural Funds of the European Union and from the means of state
budget of the Czech Republic.
With respect to the success achieved as evidenced by the patents of
the research team and positive evaluation of finished research projects,
it can be stated that Triple helix model cooperation is valuable.
2.2. High-speed water jet technology
High-speed water jet represents a technology that is able to
disintegrate even the hardest materials due to high energy transmitted
to extremely small area (see e.g. Summers 1995). If we use water jets,
there is no mechanical tool-material interaction in the process of
disintegration. The erosion capability of the jets is widely used for
many applications in modern industry. Water jet technology achieved
significant progress during last decades in applications such as cutting
of wide range of materials, surface cleaning, removal of surface layers
and repair of concrete structures. Nowadays, a number of commercial high
pressure systems are available on the market, some of them generating
pressures up to 400 MPa, other delivering up to hundreds liters of water
per minute. Water jet cutting and/or cleaning equipment except the pump
is lightweight and the whole cutting process can be easily automated.
The technology is also very advantageous for the removal of damaged
concrete layers from buildings and structures (Hela et al. 2010). The
jet is able to remove the damaged layer selectively without the
introduction of any additional cracks to construction (in contrast to
traditional technologies like jackhammering, grit blasting, milling
etc.). Moreover, adhesion strength of coatings applied on surfaces
prepared by water jets safely comply with values specified in relevant
standards concerned with concrete surface treatment prior to repair
(Silfwerbrand 1990).
2.3. Hydrodemoliton (= concrete removal and cleaning)
The first serious approach to the use of water jets for concrete
hydrodemolition was probably that of McCurrich and Browne (1972). The
first commercial hydrodemolition unit was finally developed and
introduced after 10 years (Momber 2005). Hydrodemolition uses high speed
water jet technology. High speed water jet technology is a progressive
technology of removing damaged concrete used in civil engineering since
the 80's of 20th century. It has been changing and developing since
that time.
Equipment for high speed water jet technology ranges from hand-held
tools to large tractor mounted units and robots.
The effectiveness of a particular system depends on:
* Nozzle type;
* Nozzling pattern and distance to surface;
* Water pressure; and
* Contact time.
The nozzle is moving rapidly and continually over the area of
removed concrete, and excess water is allowed to drain away (ACI 555R-01
2001). The high speed water jet technology makes its destructive action
by means of three separate mechanisms:
* Direct impact;
* Pressurization of crack; and
* Cavitation (Medeot 1989).
2.4. Economical aspects of high-speed water jet technology
There is little information in literature devoted to the economic
comparison of the new technologies with traditional ones. Most of the
contributions are dealing with cutting technologies, which occupy the
largest volume of applications relative to the others. One of them
dealing with the economic analysis of lumber processing systems was
published by Manetsch and Huber (1993). Krastel and Drechsel (1999)
tested the economy of lasers integrated in a cutting machine during
material processing. They realized complete processing of a workpiece with different technologies in one setting. Rather successful
comparisons of non-conventional techniques for material cutting are
subject in the model by Vidova (2007): costs evaluation and costs
analysis is based on measurement of economic effectiveness of the
performance of different cutting machines.
Regarding the water jet technology, most of authors interested in
the comparison of the advantages of water jet technology with other
technologies concentrate solely on the observation of a typical
parameter of the technology and on the basis of such analysis then
predict the economic advantage or inconvenience. Axinte et al. (2009)
used abrasive water jet turning to profile and dress grinding wheels. It
was found that grinding wheel can be roughed and semi-finished at
considerable lower time compared to that required for employment of
conventional (e.g. mechanical) dressers. However, the authors do not
address the total cost of the manufacturing process associated with
water jet technology and mechanical preparation of grinding wheels
(Sitek 2009). Sitek et al. (2009) referred to the research on
disintegration of surface layers of corroded and non-corroded concrete
by high-speed flat water jets. This type of water jet innovates
continuous water jet. Results indicate that progressive type of water
jet--so called pulsating water jet--achieved higher efficiency in
comparison with the corresponding continuous one in every case.
Improvement of the technology follows from the fact that impact pressure
generated by the impact of bunch of water on a target is considerably
higher than corresponding stagnation pressure generated by a continuous
jet under the same operating conditions. Unfortunately, detailed
economic analysis is missing again. Study on money saving using pulsed
water jet was published by Yan et al. (2004) in the paper on delaminated
concrete removal by forced pulsed water jet. The use of pulsed technique
resulted in saving of $200/[m.sup.2] compared to the techniques used
earlier (chipping and sandblasting).
Thorough economic analysis of the costs of water jet technology was
presented for example by Zeng and Kim (1993). They developed a method
for cost prediction of abrasive water jet kerf cutting based on the
application of the predicted cutting speed. Their analysis was utilised
in the study of Singh and Munoz (1993). They point out that unlike other
technologies, using of water jet can save anywhere from 10 to 30% of
total operating costs. They highlighted that economic analysis of the
water jet cutting process is somewhat difficult due to three factors: a)
the same cutting results can be achieved by many different combinations
of cutting parameters, b) the process flexibility, its ability to cut
different profiles without hardware changes, is hard to evaluate in most
cases, c) different customers have different objectives and they may
evaluate various attributes differently. Thus a good economic analysis
model should account for these three factors.
This paper aims to compare comprehensively in economic terms the
costs of removing degraded layers of concrete road panel using the
technology of both continuous oscillating and pulsating oscillating
water jets. To generate a pulsating jet, much cheaper equipment (up to
2.4 times) can be used compared to the equipment for generation of
continuous jet preserving the same disintegration effects. But what are
the actual operational costs?
3. Experimental procedure and arrangement
Current study is focused on both continuous and pulsating water jet
removal of degraded surface layers of standard road reinforced concrete panel stored at normal outdoor exposure (influence of frost and
atmosphere vapours, no chemicals) for approximately 18 years. To
determine real volume of disintegrated material, the following types of
high speed water jet were used: continuous oscillating and pulsating
oscillating jets. A layer of concrete from a concrete panel was removed
by means of these two technologies.
The concrete panel was made from the concrete class C30/37 XF3
(compressive strength of about 40 MPa). Dense aggregate with maximum
size of grain 16 mm was used.
Surface layers were removed step by step from top side of the
concrete panel by both continuous oscillating and pulsating oscillating
jets. Surfaces with approximate dimensions of 470 mm x 130-250 mm were
treated by this method successively. Disintegrated volume was determined
as a measure of the performance of the jet. Tests were performed at
various water pressures (30-200 MPa) and nozzle diameters (standard
commercial nozzles StoneAge OS7 and MVT Type 916 with nozzle orifice diameter of 0.81, 0.97, 1.07, 1.2, 1.4, 1.5, 1.7, and 1.8 mm were used).
New water nozzles were used during the tests. Various high pressure
pumps were used. Because pulsating jet can be generated at roughly 3
times lower water pressure to disintegrate the same volume of concrete
compared to corresponding continuous jet (Sitek et al. 2009), much
cheaper equipment can be used to do the same work using pulsating
technique. Moreover, since surfaces prepared with pulsating water jet
demonstrate higher roughness and unevenness compared to the ones treated
by continuous jet, better adhesion of coatings and/or repair mortars to
substrates prepared by pulsating jet is expected (Sitek et al. 2002).
During experiments several couples of treated surfaces with
approximately the same value of disintegrated volume were compared to
one another. Example of appearance of two compared surfaces is shown in
Fig. 1.
[FIGURE 1 OMITTED]
Computational model based on the model presented by Vidova (2007)
is completed by specific parameters used during the evaluation of
technology of high-speed water jet, as formulated by Zeng and Kim (1993)
and Singh and Munoz (1993). The model comes from assumption that total
technological costs are the most important technical-economic indicator
of the operation of machinery and equipment and also a suitable
criterion for the comparison of variant solutions.
Total technological costs [C.sub.total] are specified as the sum of
total fixed costs [C.sub.fixed] and total variable costs
[C.sub.variable.] Let's consider the hourly costs for removing the
concrete layer. Total costs related to labor hour can be expressed as
[C.sub.total] = [C.sub.fixed] + [C.sub.variable]. (1)
In fixed costs [C.sub.fixed], there are included depreciations of
production equipment [C.sub.deepr], interests related to security of
funds for equipment purchase [C.sub.int], rent for production area
[C.sub.rent] and possibly insurance premium for production equipment
[C.sub.prem]:
[C.sub.fixed] = [C.sub.depr] + [C.sub.int] + [C.sub.rent] +
[C.sub.prem]. (2)
In variable costs [C.sub.variabie] there are included material
costs [C.sub.mat,] costs for workers' wages [C.sub.wage], consumed
energy [C.sub.energy], consumed assistant substance [C.sub.exc],
consumed spare parts and consumables [C.sub.spare], and costs for
maintenance and repairs [C.sub.main]
[C.sub.variable] = [C.sub.mat] + [C.sub.wage] + [C.sub.energy] +
[C.sub.exc] + [C.sub.spare] + [C.sub.main]. (3)
Structure of total costs items for computation model is
demonstrated in Fig. 2.
Breakdown of items for calculation of total fixed costs and total
variable cost for computation model are given in the following Table 1.
Based on equations (1) to (3), the total hourly costs of operation
of four different high pressure pumps have been calculated. The
following pumps can be used for the removal of desired amount of
concrete at desired quality: for low water pressures--Pratissoli HF18
and AQP AQH50, for high water pressures--Uraca KD716 and Uraca KD724.
The water jet parameters and results of calculations are given in Table
2. The results of calculations are also shown in Figs. 3 and 4.
[FIGURE 3 OMITTED]
[FIGURE 4 OMITTED]
4. Results and discussion
The results of the calculations clearly indicate that the use of
advanced technology of pulsating water jet can reduce significantly the
cost of the process of removing layers of damaged concrete in comparison
with traditional methods of concrete removal by continuous high-speed
water jets. While the same volume of concrete is removed, the total
hourly costs are at least 1.6 times lower using pulsating jet. At higher
pressures and water flows (resulting in higher amount of disintegrated
concrete per unit time), the use of pulsating technology further reduces
costs; the ratio reached 1.8 in our tests. Since both technologies are
similar (based on the same principles), the use of pulsating jets yields
greatest savings compared to the continuous ones in depreciation items
covering total price of the equipment and related costs for repair,
maintenance and spare parts. Also energy costs are lower when using
pulsating jets.
5. Conclusion
Two research institutions--e Brno University of Technology, Faculty
of Civil Engineering and the Institute of Geonics AS CR, v. v. i. and
the industrial company Net Ltd. closely cooperated on solving tasks in
the presented research of high speed water jets and the evaluation of
effectiveness of this technology. The research tasks have been solved
with the support of funding granted by Czech Science Foundation, by the
Academy of Sciences of the Czech Republic and by Research and
Development for Innovations Operational Program financed by Structural
Funds of the European Union and from the means of state budget of the
Czech Republic. This scheme of cooperation follows the Triple helix
model. The success achieved by the research team (emphasized by the
patents and positive evaluation of finished research projects) proves
that Triple helix model cooperation is valuable.
The paper is a contribution to cost evaluation and costs analysis
of water jet technology. This paper aims to compare comprehensively in
economic terms the costs of removing degraded layers of concrete using
the technology of both continuous oscillating and pulsating oscillating
water jets. The presented computation model is based on the model of
Vidova (2007), completed by specific parameters used during evaluation
of technology of high-speed water jet technology as formulated by Zeng
and Kim (1993) and Singh and Munoz (1993). This new model comes from the
assumption that total technological costs are the most important
technical-economic indicator of the operation of machinery and equipment
and also a suitable criterion for the comparison of variant solutions.
It should be pointed out that this particular example cannot be
applied generally. It cannot be claimed that pulsating jet technology is
more economical than other technologies considering wide diversity of
applications where water jet is used. It is necessary to evaluate an
actual case and then decide to apply one or the other technology.
Regardless, it should be taken into account that pulsating jet
technology is becoming a serious competitor to relatively widespread
continuous jet technology in many areas.
doi: 10.3846/16111699.2011.645866
Acknowledgements
The article was written in connection with the project of the
Institute of clean technologies for mining and utilization of raw
materials for energy use, reg. No. CZ.1.05/2.1.00/03.0082 supported by
Research and Development for Innovations Operational Programme financed
by Structural Funds of the European Union and from the means of state
budget of the Czech Republic. The work was supported also by the
Technology Agency of the Czech Republic, projects No. TA01010948 and
Ministry of Industry and Trade of the Czech Republic, project No.
FR-TI1/387.
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Rudolf Hela (1), Lenka Bodnarova (2), Miloslav Novotny (3), Libor
Sitek (4), Jiff Klich (5), Ivan Wolf (6), Josef Foldyna (7)
(1,2) Institute of Technology of Building Materials and Components,
Faculty of Civil Engineering, Brno University of Technology, Veveri
331/95, 602 00 Brno, Czech Republic (3) Institute of Building
Structures, Faculty of Civil Engineering, Brno University of Technology,
Veveri 331/95, 602 00 Brno, Czech Republic (4,5,7) Institute of Geonics
AS CR, v. v. i., ICT, Studentskd 1768, 708 00 Ostrava-Poruba, Czech
Republic (6) NET Ltd., Nddrazni 309, 788 32 Stare Mesto pod Sneznikem,
Czech Republic E-mails: (1) hela.r@fce.vutbr.cz (corresponding author);
(2) bodnarova.l@fce.vutbr.cz; (3) novotny.m@fce.vutbr.cz; (4)
libor.sitek@ugn.cas.cz; (5) jiri.klich@ugn.cas.cz; (6)
wolf@net-waterjet.cz; (7) josef.foldyna@ugn.cas.cz
Received 02 August 2011; accepted 29 November 2011
Rudolf HELA. Assoc. Prof. (*1959) graduated at the Brno University
of Technology, Faculty of Civil Engineering in 1983. He finished his
Ph.D. study at the field of Building technology in 1989. Since 2003 he
is Assoc. Prof. at the Institute of Technology of Building Materials and
Components in the Faculty of Civil Engineering at the Brno University of
Technology (Czech Republic). He is a deputy head of the Institute. He
specializes in the field of technology of manufacture of concrete and
concrete parts and in the field of diagnostics of reinforced concrete
structures. He is an expert in technology of concrete, designing of
concrete mix-designs, development of special concrete with respect to
frost resistance and resistance to corrosive environments, high-strength
concrete and self-compacting concrete as well as technology of
production of concrete construction elements--design of appropriate
technologies including testing finished products.
Lenka BODNAROVA. Ph.D. (*1971) graduated at the Brno University of
Technology, Faculty of Civil Engineering in 1994. She finished her Ph.D.
study at the field of Building Materials Engineering in 2000. From 1995
she works as a Research fellow/Instructor in the Institute of Technology
of Building Materials and Components in the Faculty of Civil Engineering
at the Brno University of Technology (Czech Republic). She is an expert
in composite materials in Civil engineering and possibilities of use of
technology of high speed water jet in civil engineering, in particular
in the phase of preparation of surface for renovation of concrete
structures.
Miloslav NOVOTNY. Assoc. Prof. (*1955) graduated at the Brno
University of Technology, Faculty of Civil Engineering in 1979. He
finished his Ph.D. study at the field of Building Structures in 1984.
Since 1999 he is Assoc. Prof. at the of Building Structures in the
Faculty of Civil Engineering at the Brno University of Technology (Czech
Republic). He is a head of the Institute and vicedean Faculty of Civil
Engineering. He specializes in the field of Rehabilitation of Building
Structures und Using of Microwawe Radiation.
Libor SITEK. Ph.D. (*1964) graduated at the Brno University of
Technology, Faculty of Mechanical Engineering in 1988. He finished his
Ph.D. study at the area of water jetting technology in 2000. From 1989
he works as a scientist at the Institute of Geonics ASCR, v. v. i. in
Ostrava (Czech Republic). His research activities are primarily oriented
at material disintegration by water jet technology as well as
fundamental research on generation and behaviour of water jets.
Jin KLICH. Mech. Eng. (*1984) graduated at the Technical
University--VSB in Ostrava, Faculty of Mechanical Engineering in 2009.
At present he is Ph.D. student at the area of water jetting technology.
From 2009 he works as a scientist at the Institute of Geonics ASCR, v.
v. i. in Ostrava (Czech Republic). His research activities are oriented
at water jet technology and analysis of surface quality.
Ivan WOLF. Mech. Eng. (*1959) graduated at the Nitra Agriculture
University, Faculty of Mechanical Engineering in 1983. In 1990 he
founded private company NET, Ltd., of which provide high-pressure
waterblasting and hydrodemolition work for industry. He closely
cooperates with various academic institutes on research activities at
the area of water jet.
Josef FOLDYNA. Ph.D. (*1958) graduated at the University of Mining
and Metallurgy in Ostrava, Faculty of Mechanical Engineering in 1983. He
finished his Ph.D. study at the area of water jet technology in 1997.
From 1986 he works as a scientist at the Institute of Geonics ASCR, v.
v. i. in Ostrava (Czech Republic), from 2006 as a head of Department of
Material Disintegration. His research activities are oriented recently
at the experimental research on generation of high-speed pulsating water
jets, and determination of crucial parameters influencing the
performance of pulsating jets.
Table 1. Example of items in computation model for
calculation of fixed and variable costs
Item Unit
1 Market entry price of device EURO
2 Market entry price of pump EURO
3 Market entry price of pulsing device EURO
4 Price of handling device for nozzle movement EURO
5 Depreciation period year
6 Effective time hour
7 Interest rate %
8 Cost of production area EURO
9 Insurance premium %
10 Hourly wage EURO
11 Wage coefficient 12
Monthly lump price for energy EURO
13 Labor hours per month hour
14 Hourly energy consumption kWh
15 Price of energy per kWh EURO
16 Price of assistant substance per liter EURO
17 Hourly consumption of assistant substance liter
18 Coefficient of spare parts %
19 Coefficient of maintenance and repairs %
20 Hourly price for hose and nozzles EURO
Table 2. Comparison of couples of surfaces treated by
continuous oscillating jet generated by high pressure and
pulsating oscillating jet generated by lower pressure and
total hourly costs for removal of specified volume when
using specified pump
Jet Type Suitable high Nozzle Water
pressure pump Diameter Pressure
[mm] [MPa]
Continuous Uraca KD716 0.81 180
Pulsating Pratisolli HF 18 1.5 50
Continuous Uraca KD724 0.97 200
Pulsating AQP AQH50 1.4 70
Continuous Uraca KD724 0.81 200
Pulsating AQP AQH50 1.2 70
Jet Type Disintegrated Total
Volume hourly
[[cm.sup.3]] costs
[EUR]
Continuous 0.8 55.86
Pulsating 0.8 35.39
Continuous 1.8 79.67
Pulsating 1.6 44.43
Continuous 0.8 73.65
Pulsating 0.8 42.15
Fig. 2.Structure of total costs items for
computation model
Total technological cost [C.sub.total]
in EURO (per hour)
Total fixed Total variable
costs [C.sub.fixed] [C.sub.variable]
Hourly depreciation Hourly wage cost
Hourly interests Cost of energy
Hourly rent Cost of assistant
substance
Hourly insurance Cost of spare parts
premium and consumables
Cost of maintenance
and repairs
