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 . 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 . 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 , 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 . Hydration controlling admixtures can also be used to provide extended working life. Shrinkage reducing admixtures are also sometimes used . 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 . 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 . 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 . 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 . 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 . 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 . 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 . 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 . 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 . 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"  and the subsequent AASHTO-AGC-ARTBA "Guide Specification for Shotcrete Repair of Highway Bridges" . Dams and Hydraulic Structures Numerous dams and hydraulic structures have been repaired with sprayed concrete in North America. Heere et al.  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 . 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 . 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 : • • • • • • • • • • 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 , 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 , 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.