close

Вход

Забыли?

вход по аккаунту

?

rarocs.34051.0056

код для вставкиСкачать
CLOSING
PAPER
Downloaded by [ Griffith University] on [25/10/17]. Copyright © ICE Publishing, all rights reserved.
REPAIR AND RENOVATION OF CONCRETE STRUCTURES IN
NORTH AMERICA USING SPRAYED CONCRETE
D R Morgan
AMEC Americas Limited
Canada
ABSTRACT. Sprayed concrete has been used for infrastructure repair and renovation in
North America for over 90 years. There have, however, been several innovations in both
shotcrete materials and application technology in the last two decades, which have provided
enhancements in the use of sprayed concrete for remedial work. This paper provides an
overview of these developments with specific discussion of: sprayed concrete materials; mix
design; batching, mixing and application and finishing. Data is provided regarding typical
modern wet and dry-mix sprayed concrete mix designs and the plastic and hardened
properties of such material. Finally, some typical examples of sprayed concrete repair and
renovation of infrastructure in North America are presented. These examples are mainly
taken from projects on which the writer acted as a consultant.
Keywords: Sprayed concrete, Infrastructure repair, Silica fume, Steel fibre, Synthetic fibre.
D R Morgan, PhD, P Eng, FACI, FCAE is Chief Materials Engineer with AMEC Earth &
Environmental, a division of AMEC Americas Limited. He is a civil engineer with over
35 years experience in concrete technology and the evaluation and rehabilitation of
infrastructure. Dr. Morgan is a fellow of the Canadian Academy of Engineering and the
American Concrete Institute (ACI). He is Secretary of ACI Committee 506, Shotcrete. He is
a member of several ACI, ASTM, and Canadian Standard Association (CSA) technical
committees, and is a founding member of the American Shotcrete Association. Dr. Morgan
has provided consulting services on concrete and sprayed concrete projects throughout North
America and around the world. He has over 70 publications in technical journals and
conference proceedings relating to the use of sprayed concrete in infrastructure rehabilitation
and other applications and has chaired international conferences on sprayed concrete for
underground support.
Downloaded by [ Griffith University] on [25/10/17]. Copyright © ICE Publishing, all rights reserved.
486 Morgan
INTRODUCTION
The concept of pneumatically projecting cementitious mortars was first developed by Carl E.
Akeley, in Chicago in 1910, when he adapted this process to spray cement mortars in the
production of animal models for exhibitions. Over the decades, which have followed, this
technology has undergone significant advances in many areas including choice of materials;
mix formulations, equipment technology, method of application and usage. By the 1950's,
larger size aggregates started to be used in dry-mix sprayed concrete, and also by the 1950's,
wet-mix sprayed concrete was being used [1]. Today, large volumes of both dry-mix and
wet-mix sprayed concrete are being applied in many projects in North America and
worldwide. The increased usage of specialized sprayed concrete equipment and mix designs
has enabled the efficient production of high quality sprayed concrete installations for
infrastructure repair and renovations [2].
Sprayed concrete has gained wide acceptance as the preferred concrete placement method in
a variety of new construction and repair applications. This is due to the versatile and flexible
nature of sprayed concrete, which in many instances can result in cost savings in situations
such as the following:
•
•
•
•
Where formwork is impractical, or can be reduced or eliminated,
Where access to the work area is difficult,
Where thin layers and/or variable thickness is required,
Where normal casting techniques cannot be employed.
In particular, there has been a rising demand for the use of sprayed concrete in the repair and
rehabilitation of infrastructure. Its ease of application, start/stop capability (particularly for
dry-mix sprayed concrete) and thin layer application method have proven to be very distinct
advantages over other types of repair methods. One of the major attributes of sprayed
concrete is the usually excellent bond to the substrate materials. Sprayed concrete has thus
been the selected repair method for a wide variety of concrete structures including
deteriorated bridges, reinforced concrete buildings, tunnels, dams, cooling towers, tanks,
canals, aquaducts and various industrial structures.
This article provides an overview of the use of sprayed concrete in North America for repair
and renovation of infrastructure. Sprayed concrete materials, properties and application
processes are described, followed by examples of repair and rehabilitation projects in North
America.
MATERIALS
The materials used in sprayed concrete are essentially the same as those used in conventional
cast concrete. There are however some differences in the proportioning of ingredients.
Higher than normal cementing materials contents (400 to 500 kg/m3) are typically used, and
the gradation of aggregates usually falls within the limits specified by ACI 506R-90 (95) (1).
These gradations contain considerably less coarse aggregate and finer composite aggregate
gradations than conventional cast concretes, since conventional cast concretes would have
excessive rebound of coarse aggregates if sprayed.
Downloaded by [ Griffith University] on [25/10/17]. Copyright © ICE Publishing, all rights reserved.
Repair and Renovation of Concrete 487
Over the past two decades, significant developments in materials technology have led to a
wider range of applications for sprayed concrete. These developments include:
•
•
•
The use of supplementary cementing materials such as fly ash and silica fume [3], In
ternary blends of cementing materials (Portland cement, fly ash and silica fume), the fly
ash increases paste volume thereby improving pumpability and shootability, and the silica
fume enhances adhesion and cohesion of the mix and reduces rebound. Silica fume
(typically at between 7 to 12% by mass of cement) also provides the ability for greater
build up thicknesses in a single pass, particularly in overhead applications, and improves
hardened properties such as strength and durability [4 and 5].
The use of chemical admixtures to improve the plastic properties of wet-mix sprayed
concrete. Water reducers and superplasticizers are commonly used at dosages similar to
those in conventional concretes to control the water demand of mixes particularly those
containing silica fume. Air entraining admixtures are also employed to achieve higher
than normal air contents (8 to 10%) for enhancement of the pumpability and shootability
of the mix [6]. Hydration controlling admixtures can also be used to provide extended
working life. Shrinkage reducing admixtures are also sometimes used [7].
The use of steel and synthetic fibres. Steel fibres have been commonly used at addition
rates between 40 to 60 kg/m3 in tunnelling and mining applications. Synthetic fibres at
high volume addition rates (up to 1.5% by volume) have found increasing use in a wide
range of applications. The post-crack toughness imparted by synthetic fibres can be
equivalent or even superior to that provided by steel fibres or welded wire mesh fabric
[8]. In addition, their chemically inert nature, lightweight and non-abrasive properties
have made them a material of choice for many new sprayed concrete construction and
repair applications.
Caustic accelerators have traditionally been used in sprayed concrete to improve the thickness
of build-up, reduce time to initial set and accelerate early age strength gain. However, the
long-term detrimental effects of many of these caustic accelerators on strength, shrinkage and
durability are well known. Fortunately, with the advent of silica fume, it is no longer
necessary to rely solely on accelerators, unless it is essential to the process. If early age
strength development is necessary, new non-caustic accelerators with little negative effect on
the properties of the hardened sprayed concrete are now available.
SHOTCRETE PROPERTIES
Properly designed and applied shotcrete can have good compressive, tensile and bond
strength, rendering sprayed concrete an excellent repair material. Given the higher
cementitious material content than conventional concretes, the following consequences for
the repair sprayed concrete, compared to the concrete in the structure being repaired, can
usually be expected:
•
•
•
Higher compressive and flexural strengths;
Higher water demand, resulting in higher drying shrinkage capacity in the repair material,
unless shrinkage compensating cements, or shrinkage reducing admixtures are used in the
sprayed concrete formulation;
Good durability if proper mix design and application procedures are employed.
Dry-mix sprayed concrete can develop 28-day compressive strengths of around 50 MPa for
plain sprayed concrete and 60 MPa for silica fume modified sprayed concrete. Wet-mix
sprayed concrete, using silica fume and superplasticizers, can be formulated, if required, to
Downloaded by [ Griffith University] on [25/10/17]. Copyright © ICE Publishing, all rights reserved.
488 Morgan
achieve strengths in excess of 80 MPa at 28 days. Flexural strength of 6 MPa at 28 days is
quite common in high strength dry-mix and wet-mix sprayed concretes. Lower strength
formulations can, of course, be produced where compatibility with substrate original
concretes is appropriate.
Long-term freeze-thaw durability of shotcretes can be assessed by determining ASTM C457
air void system parameters from extracted cores. In dry-mix sprayed concrete, it appears that
the natural air content, specific surface and spacing factor are such that freeze-thaw durable
sprayed concrete can be produced. The resistance of dry-mix and wet-mix sprayed concrete
to frost attack and scaling from exposure to de-icing chemicals can be enhanced by addition
of air-entraining admixtures [9].
ASTM C642 boiled absorption and volume of permeable voids values are commonly used in
sprayed concrete specifications to identify shotcrete that is less than adequately consolidated
or that has been damaged by excessive use of accelerators or improper curing. Limits of a
maximum of 8% for boiled absorption and 17% for the volume of permeable voids are
commonly specified. There is good correlation between these ASTM C642 parameters and
frost durability and de-icing salt scaling resistance of sprayed concrete [9].
One of the major attributes of sprayed concrete is the usually excellent bond to the substrate
material. Depending on the sprayed concrete characteristics and the nature of substrate, bond
strengths of between 1.0 MPa to as much as 2.5 MPa are attainable, provided that proper
surface preparation has been done [9, 10]. This has made sprayed concrete particularly well
suited for repair of vertical and overhead concrete surfaces.
APPLICATION OF SHOTCRETE IN REPAIRS
The first stage in the repair of deteriorated structures is to perform diagnostic investigations
to examine the cause(s) of damage in the structure. These causes could range from freezethaw damage, to fire damage, to carbonation of the cover concrete, to chloride attack of the
reinforcement, or to physical causes such as impact damage or overstressing. The cause of
damage influences the nature and extent of preparatory work and type of sprayed concrete
application required.
Thorough preparation of the substrate to be repaired is essential. Any contaminated concrete
must be removed and any problems with the reinforcement must be resolved. In general,
damaged, microcracked, chloride-contaminated and unsound concrete must be removed by
appropriate methods such as chipping, scarifying, hydrodemolition, or sandblasting. If
chipping or scarifying is used, it should be followed by hydroblasting or sandblasting to
remove the mechanically damaged "bruised" surface layer. If the cause of deterioration is
reinforcement corrosion, it is important to remove all loose corrosion products by
hydroblasting or sandblasting. Half-cell potential testing is useful to determine the locations
and probability of reinforcement corrosion. A gap of at least 25 mm behind the bars should
be allowed to provide mechanical anchorage for the repair material and encapsulation of the
rebar with the protective alkaline-sprayed concrete. If no reinforcement is exposed, it is
prudent to provide additional mechanical anchorage such as grouted dowels in conjunction
with mesh or fibre reinforcement. Sacrificial zinc anodes are sometimes installed in the repair
area to mitigate the problem of the "anodic ring effect" in the reinforced concrete surrounding
the repair area.
Downloaded by [ Griffith University] on [25/10/17]. Copyright © ICE Publishing, all rights reserved.
Repair and Renovation of Concrete 489
Prior to application of sprayed concrete, all loose material or dust should be removed and any
running water must be controlled. The substrate concrete must be in a saturated surface dry
(SSD) condition at the time of application of sprayed concrete. Excess free moisture (seen as
a glisten or sheen of wetness on the surface) will increase the water/cement ratio at the
interface and reduce the interfacial bond strength. Excessively dry concrete substrates will
also result in reduced bond strengths.
Either dry-mix or wet-mix sprayed concretes can be employed with the choice depending on
production volumes, equipment availability, environmental considerations and logistical
constraints. The mixtures can be batched by any of the following systems: a) central batching
with transit mix supply; b) transit mix batched and supply; c) site batching using either
volumetric or mass batching methods; or d) dry-bagged materials. While site-batched
methods tend to produce the most economical sprayed concrete, dry-bagged materials,
supplied in either bulk bin bags or 30-kg bags, provide a number of benefits over other
batching techniques, including uniform and consistent quality material, allowance for
innovative formulations, easier access and storage for remote locations and the convenience
of start/stop applications. Silica fume and in many instances, products such as powdered air
entraining admixtures, shrinkage compensating materials or shrinkage reducing admixtures,
as well as fibres, can be included in the dry-bagged materials.
In dry-mix sprayed concrete, the nozzleman must be able to control the amount of water
added at the nozzle and the application technique, including the distance to the receiving
surface, nozzle orientation and nozzling motion. In wet-mix sprayed concrete, the nozzleman
controls the amount of air added at the nozzle as well as the shooting technique. Care must
be taken to not entrap any rebound and to not apply new sprayed concrete over overspray that
has hardened. Good guidance to nozzling is provided by ACI 506R-90 (95) (1). An
increasing trend in the present sprayed concrete industry is to pre-qualify nozzlemen through
the shooting of preconstruction mock-ups. The purpose of this is to demonstrate the
nozzleman's ability to produce a sprayed concrete consistent with project demands.
Nozzlemen are assessed for their ability to produce well-compacted sprayed concrete with
good encapsulation of reinforcement in configurations expected in the project. In addition,
organizations such as the American Shotcrete Association (www.shotcrete.org) are now
offering sprayed concrete training schools and the ACI offers nozzleman certification
programs to enhance the quality of sprayed concrete construction.
The finished surface is normally best left "as shot" unless aesthetics dictate otherwise. In
some instances, a flash coat containing sand as the only aggregate can by applied to the base
coat of sprayed concrete to provide a smoother surface that can be screeded and trowelled to
provide the required surface finish and texture. Moist curing afterwards is essential to control
drying shrinkage cracking [7].
EXAMPLES OF SHOTCRETE REPAIR OF INFRASTRUCTURE
Both dry-mix and wet-mix sprayed concrete have been successfully applied in a wide variety
of infrastructure repair projects in North America. Several case history examples from the
writer's project files and a few other reference sources [13, 19] follow.
Downloaded by [ Griffith University] on [25/10/17]. Copyright © ICE Publishing, all rights reserved.
490 Morgan
Marine Structures
Between 1983 and 1985, about CAN $2 million was spent in sprayed concrete repair of Pier
B-C in Vancouver Harbour, which presently supports the Canada Place Trade and
Convention Centre and Pan Pacific Hotel [4]. Dry-mix sprayed concrete was utilized to
repair deteriorated cast-in-place reinforced concrete sea walls, pile caps, beams, stringers and
deck slab soffits. The work was started using a conventional plain dry-mix sprayed concrete,
but because of the need for enhanced productivity when working in intertidal zones, silica
fume was subsequently employed in the mix. This resulted in improved adhesion and
cohesion and resistance to sagging and sloughing, as well as excellent wash-out resistance of
the freshly applied sprayed concrete. Figure 1 shows a view of the sprayed concrete repaired
beams. This pioneering project marked the first use of silica fume in dry-mix sprayed
concrete for remedial work in Canada, and has since led to the routine use of silica fume in
sprayed concrete for the repair of marine and other infrastructure throughout North America.
Figure 1 View of sprayed concrete repaired beams at the Canada Place Trade and
Convention Centre in Vancouver Harbour
In 1986, an annual repair program for berth faces at the Port of Saint John, New Brunswick
was initiated and subsequently continued for over 10 years [11]. Deterioration of the mass
concrete berth faces was caused by an aggressive environment including mechanical damage
from ship impact, exposure to strong currents laden with salt and abrasive sediments, alkaliaggregate reactivity and, most significantly, between 200 to 300 freeze-thaw cycles per year
over an 8.5 m tidal range. Between 1986 and 1996, approximately 1600 lineal metres of the
10m high berth face was repaired using tied-back and anchored wet-mix, air-entrained, steel
fibre reinforced silica fume modified sprayed concrete. A condition survey conducted in
1995 revealed that the sprayed concrete had excellent freeze-thaw durability after exposure to
over 2000 freeze-thaw cycles and was generally in a very good condition in such a harsh
marine environment. Figure 2 shows a view of the berth faces after 10 years in service.
Downloaded by [ Griffith University] on [25/10/17]. Copyright © ICE Publishing, all rights reserved.
Repair and Renovation of Concrete 491
Figure 2 Sprayed concrete repaired ship berth faces at the Port of Saint John, New
Brunswick after 10 years in service
Figure 3 Sprayed concrete repair of shipping berth faces underway at the Port of Montreal,
St. Lawrence River, Quebec
Downloaded by [ Griffith University] on [25/10/17]. Copyright © ICE Publishing, all rights reserved.
492 Morgan
In 1995, a prototype repair program was undertaken of berth faces at the Port of Montreal in
the St. Lawrence River [12]. The combined effects of frost damage, alkali-aggregate
reactivity and de-icing chemical attack had caused severe deterioration of the concrete
structure. In some places, the concrete was turning into rubble. Repairs were carried out by
removing disintegrated material and applying a tied-back and anchored wet-mix,
air-entrained, silica fume sprayed concrete. About two-thirds of the berth face, 122 m long
and 7.1 m high, was repaired using 11.4kg/m 3 of polyolefin fibre reinforced sprayed
concrete. The remaining third of the berth face was repaired using 60 kg/m3 of steel fibre
reinforced sprayed concrete. Figure 3 illustrates the repairs of the shipping berth faces
underway. The sprayed concrete has performed well and the comparative behaviour of the
steel and polyolefin fibre reinforced sprayed concrete sections is being monitored.
Bridges
One of the most widespread uses of sprayed concrete in North America has been for the
repair of bridges. An example of such work is the F G Gardiner Expressway in Toronto
where a latex-modified sprayed concrete was used for the repair of prestressed concrete box
beams at locations where prestressing strands had rusted [13]. All spalled and delaminated
concrete was removed together with areas where the chloride content was unacceptably high.
Delaminated areas were removed and the strands were exposed for determination of section
loss. Concrete removal extended into sound areas until at least 50 mm of clean strand was
exposed. The cut out areas extended for a minimum of 20 mm behind rusted steel and all
cracks were chased out. The rust was then removed by grit blasting and the cut out areas
were sprayed with latex-modified sprayed concrete. Figure 4 shows the sprayed concrete
repairs to the expressway.
Figure 4 Latex-modified sprayed concrete repairs to the F G Gardiner Expressway,
Toronto, Ontario
Downloaded by [ Griffith University] on [25/10/17]. Copyright © ICE Publishing, all rights reserved.
Repair and Renovation of Concrete 493
Substantial efforts have been made by organizations such as the Transportation Association
of Canada and the Federal Highways Administration (FHWA) in the USA to evaluate the
performance of existing sprayed concrete repairs to highway bridges, with a view to
ascertaining the necessary requirements for the production of durable sprayed concrete
repairs to highway bridges. Morgan and Neill conducted a condition survey of a total of 61
highway bridges repaired with sprayed concrete in four different provinces across Canada as
part of the Canadian Strategic Highway Research Program [14]. Repairs ranged in age from
1 to 30 years, but were mostly about 5 to 10 years old. Repairs had been conducted with a
variety of different types of sprayed concrete, including wet-mix and dry-mix sprayed
concrete, with and without fibre reinforcement and latex additives. Of the bridges
investigated, 62% of the repairs were rated as being in good to excellent condition, 25% in
fair condition, 10% in poor condition and only 3% were found to have failed. The ratings of
poor and failed conditions were mainly attributed to poor sprayed concrete workmanship,
placement during unfavourable weather conditions, or failure of the substrate concrete. The
findings of this study were incorporated in a C-SHRP "Recommended Practice for Shotcrete
Repair of Highway Bridges" [15] and the subsequent AASHTO-AGC-ARTBA "Guide
Specification for Shotcrete Repair of Highway Bridges" [18].
Dams and Hydraulic Structures
Numerous dams and hydraulic structures have been repaired with sprayed concrete in North
America. Heere et al. [16] provides an overview of the performance of sprayed concrete
repairs to five British Columbia Hydro dams. The earliest repairs dated back to 1954 and
used a conventional dry-mix sprayed concrete, while more recent repairs in 1989 used steel
fibre reinforced, silica fume modified dry-mix sprayed concrete. Heere et al. provide
recommendations for the construction of durable sprayed concrete repairs to dams. Figure 5
illustrates a view of the completed sprayed concrete repairs to the Ambursen buttress dam at
the Jordan River Dam in Vancouver Island, British Columbia.
Figure 5 Completed sprayed concrete repairs to the Ambursen buttress dam at the Jordan
River Dam, Vancouver Island, British Columbia
Downloaded by [ Griffith University] on [25/10/17]. Copyright © ICE Publishing, all rights reserved.
494 Morgan
In 1994, a major seismic retrofit program was carried out on the Littlerock Dam in southern
California [17]. This multiple-arch dam provides vital water supply for both the Palmdale
Water District and the Littlerock Creek Irrigation District. Its location just 2.4 km south of
the San Andreas Fault raised concerns about the adequacy of the dam and its stability in the
event of an earthquake. To provide seismic strengthening, an air-entrained, silica fume
modified, steel fibre reinforced wet-mix sprayed concrete was applied at a nominal thickness
of 100 mm over of 4500 m 2 surface area, together with over 3400 anchors. Figure 6 shows
the sprayed concrete repair on the dam face in progress. Quality control testing indicated
excellent sprayed concrete performance (compressive strength, bond pull-off strength,
consolidation, toughness, boiled absorption and volume of permeable voids). On completion
of the project, the sprayed concrete was observed to be essentially crack-free, in spite of the
work being completed in a desert climate, where the ambient temperatures rose as high as
40°C during the daytime and, by project end, fell below zero at night. The work was
successfully completed on time and on budget to the satisfaction of the owner.
Figure 6 Seismic retrofit of Littlerock Dam, Palmdale, California, using wet-mix, steel fibre
reinforced silica fume sprayed concrete
Fibre reinforced sprayed concrete has also been frequently used by the British Columbia
Ministry of Transportation to stabilize creek beds and protect concrete bridge piers and
abutments which have been eroded by scour from flooding and debris flows in steep
mountainous terrain. Large riprap boulders have been stacked and fibre reinforced sprayed
concrete applied (in lieu of slush grouting) to provide a "toughened" system, which reduces
the potential for damage from boulder impact, hydraulic uplift forces, and general scour and
erosion. Both steel and synthetic fibre reinforced sprayed concrete have been successfully
used in this kind of work. Figure 7 illustrates the stabilization of the creek bed at Harvey
Creek, Lions Bay, British Columbia, using wet-mix steel fibre reinforced sprayed concrete.
Downloaded by [ Griffith University] on [25/10/17]. Copyright © ICE Publishing, all rights reserved.
Repair and Renovation of Concrete 495
Figure 7 Stabilization of creek bed at Harvey Creek, Lions Bay, British Columbia, using
wet-mix steel fibre reinforced sprayed concrete
Figure 8 Completed sprayed concrete lining in Wachusetts
Downloaded by [ Griffith University] on [25/10/17]. Copyright © ICE Publishing, all rights reserved.
496 Morgan
In 2001-2002 the historic 11 km long Wachussett Aquaduct in Eastern Massachusetts was
rehabilitated with wet-mix sprayed concrete. The original aquaduct was constructed between
1897 and 1903 and was the primary source of drinking water for the city of Boston. The
original aquaduct was horseshoe shaped and 3.35 m high. The sidewalls up to the "spring
line" and invert were constructed of dressed brick ashlars masonry. The crown of the original
aquaduct (from 9 o'clock to 3 o'clock) was constructed of un-reinforced concrete. In the
1960's new water supply systems were developed for Boston and the aquaduct ceased to be
used. By 1999, however, water demand in the area required the Wachussetts aquaduct to be
put back into service [19]. The restoration project primarily consisted of application of
75 mm of wire mesh reinforced sprayed concrete lining the entire surface of the 11 km long
aquaduct. Over 11,500 cubic meters of wet-mix sprayed concrete were applied. The sprayed
concrete lining was designed to strengthen and control water inflow into the aquaduct, and
provide a smooth tunnel surface to maximize the volume of water flowing through the tunnel.
The lining was finished to an exacting east-concrete equivalent finish. Figure 8 shows the
finished tunnel lining. The sprayed concrete lining was completed within 18 months and the
smooth sprayed concrete lining provided better water flow capacity than originally designed,
in spite of the reduction in cross-section volume, because of the improved lining smoothness.
Miscellaneous Sprayed Concrete Repairs
In addition to the shotcrete repairs described above, the writer has been involved in numerous
other repair and strengthening works, such as [4]:
•
•
•
•
•
•
•
•
•
•
Jacketing and strengthening of cracked and leaking grain silos,
Repair of corrosion damaged bulk shipping facilities such as potash, coal and sulphur
load-out dumper pits, loading towers and conveyors,
Repair of seismic upgrading of heritage and other masonry and reinforced concrete
structures [20],
Repair of chimney stacks and cooling towers,
Repair and strengthening of large diameter corrugated metal culverts,
Repair of water and sewer pipes and prestressed concrete pressure pipes,
Repair of deteriorated aqueducts, pressure headrace tunnels, canals and other water
conveyance systems,
Repair of deteriorated and leaking swimming pools, water reservoirs, sumps, pits and
other liquid containing facilities,
Repair of 50-year old lightweight concrete ships now used as breakwaters in British
Columbia [21],
Repair of pulp and paper mills and other industrial structures.
CLOSURE
Over the past decades, sprayed concrete has been selected as the repair method of choice for
a variety of structures in North America and around the world. Its versatility, unique method
of application and cost effectiveness has made it the material of choice for many concrete
repair projects. It's proven record as a high quality and durable repair material has been well
demonstrated in a number of concrete rehabilitation projects by excellent performance after
decades of exposure in severe environments. Continuing changes and improvements in mix
formulations and application technology together with enhancement of nozzleman skills and
an increase of design engineers familiarization with this construction process has lead to
increasing use of this versatile technology for concrete infrastructure repair and rehabilitation.
Downloaded by [ Griffith University] on [25/10/17]. Copyright © ICE Publishing, all rights reserved.
Repair and Renovation of Concrete 497
REFERENCES
1. ACI 506R-90 (95), Guide to Shotcrete.
1990,41pp.
American Concrete Institute, Detroit,
2. MORGAN, D.R., Shotcrete Repair of Infrastructure
Beton-Instandsetzung 1997, Igls, Austria, January 1997, 17 pp.
in
North
America.
3. MORGAN, D.R., Use of Supplementary Cementing Materials in Shotcrete. Proceedings,
International Workshop on the Use of Fly Ash, Slag, Silica Fume and other Siliceous
Materials in Concrete, W.G. RYAN, Concrete Institute of Australia. Sydney, Australia,
July 4-6, 1988, pp. 403-432
4. MORGAN, D.R., Dry-Mix Silica Fume Shotcrete in Western Canada, Concrete
International: Design and Construction, Vol. 10, No. 1, January 1988, pp. 24-32
5. MORGAN, D.R., NEILL, J., MCASKILL, N., DUKE, N., Evaluation of Silica Fume
Shotcrete, CANMET/CSCE International Workshop on Silica Fume in Concrete,
Montreal, Quebec, May 4-5, 1987, 34 pp.
6. BEAUPRE, D., MINDESS, S., Compaction of Wet Shotcrete and Its Effect on
Rheological Properties, Proceedings, International Symposium on Sprayed Concrete,
Fagernes, Norway, October 1993, pp. 167-181
7. MORGAN, D.R, CHAN, C , Understanding and Controlling Shrinkage and Cracking in
Shotcrete. Shotcrete Magazine, Vol. 3, No. 3, 2001, pp. 26-30
8. MORGAN, D.R., HEERE, H., MCASKILL, N., CHAN, C , System Ductility of Mesh
and Synthetic Fibre Reinforced Shotcrete, 3rd International Symposium on Sprayed
Concrete, Gol, Norway, September 26-29, 1999
9. BEAUPRE, D., TALBOT, C , GENDREAU, M., PIGEON, M., MORGAN, D.R., Deicer
Salt Scaling Resistance of Dry- and Wet-Process Shotcrete, ACI Materials Journal, Vol.
91, No. 5, September-October 1994, pp. 487-494
10. OPSAHL, O.A., Study of a Wet-Process Shotcreting Method - Volume 1, Division of
Building Materials, University of Trondheim, Report No. BML 85.101,
November 1985
11. GILBRIDE, P., MORGAN, D.R. AND BREMNER, T.W. Performance of Shotcrete
Repairs to Berth Faces at the Port of Saint John. Odd Gjorv Symposium, CANMET/ACI
International Conference on Performance of Concrete in Marine Environment, St.
Andrews-by-the-Sea, New Brunswick, August 4-9, 1996, pp. 163-171.
12. MORGAN, D.R., LOBO, A. AND RICH, L.D. About Face—Repair at the Port of
Montreal. Vol. 20, No. 9, September, 1998, pp. 66-73.
13. TORKE, A. Rehabilitation of Prestressed Concrete Box Beam Deck of an Elevated
Expressway. Canadian Journal of Civil Engineering, Vol. 16, No. 1, 1989.
Downloaded by [ Griffith University] on [25/10/17]. Copyright © ICE Publishing, all rights reserved.
498 Morgan
14. MORGAN, D.R. AND NEILL, J. Durability of Shotcrete Rehabilitation Treatments of
Bridges.
Transportation Association of Canada Annual Conference, Winnipeg,
Manitoba, September, 15-19, 1991.
15. CANADIAN STRATEGIC HIGHWAY RESEARCH PROGRAM (C-SHRP).
Recommended Practice for Shotcrete Repair of Highway Bridges. Transportation
Association of Canada, June, 1992, pp. 84.
16. HEERE, R., MORGAN, D.R., BANTHIA, N. AND YOGENDRAN, Y. Evaluation of
Shotcrete Repaired Concrete Dams in British Columbia. Concrete International, Vol. 18,
No. 3, March, 1996, pp. 24-29.
17. FORREST, M.P., MORGAN, D.R., OBERMEYER, J.R., PARKER, P.L. AND
LAMOREAUX, D.D. Littlerock Dam Seismic Retrofit using Bonded Shotcrete Overlay.
ACI Concrete International, Vol. 17, No. 11, November, 1995, pp. 30-36.
18. AASHTO-AGC-ARTBA TASK FORCE 37 REPORT. Guide Specification for Shotcrete
Repair of Highway Bridges. FHWA, Washington, D.C., February 1988, pp. 117.
19. TOWN, R. Restoring the century-old Waschusett Aquaduct. Shotcrete Magazine, Vol. 6,
No. 3, Summer, 2004, pp. 2-4.
20. HEERE, R., MORGAN, D.R., MCASKILL, N. AND KNOWLTON, T. Shotcrete
Rehabilitation of a Vancouver, BC Historic High Rise Building. Shotcrete Magazine,
Vol. 1, No. 4, November 1999, pp. 10-13.
21. MCASKILL, N. AND HEERE, R. Shotcrete Repair of WWII Concrete Hulks, Shotcrete
Magazine, Vol. 6, No. 3, Summer 2004, pp. 10-14.
Downloaded by [ Griffith University] on [25/10/17]. Copyright © ICE Publishing, all rights reserved.
Документ
Категория
Без категории
Просмотров
1
Размер файла
2 239 Кб
Теги
0056, rarocs, 34051
1/--страниц
Пожаловаться на содержимое документа