The Tuscarora Mountain Tunnels in Pennsylvania have a fascinating history. The older of the two tunnels, built between 1938 and 1940, was designed to carry a railroad that never came into service. Industrialists of the day, William Henry Vanderbilt and Andrew Carnegie, were backers of the scheme which was halted when they struck a deal with rival railroad owners.
SHOTCRETE VS FIRE AND WATER REPLACEMENT OF FLUME 4/5/6 AND 30
On August 14, 2021, the Caldor Fire started in Northern California near Pollock Pines, CA. The fire ended up consuming almost 222,000 acres (90,000 hectares) and seriously threatened South Lake Tahoe. Besides the over 1000 structures that were lost, the fire also burned along a major portion of the El Dorado Irrigation District’s Canal (EID) which provides drinking and irrigation water to numerous communities throughout the area
Honorable Mention Project
Outstanding Repair & Rehabilitation Project
Board Position Statement
I have a project with a segmental retaining wall. The project is located in Maryland. The CMUs of the retaining wall have significantly deteriorated in several areas. The geo-grid fabric appears to be in good condition in the areas where it could be observed. I suspect the deterioration is caused by saltwater runoff during snow events combined with the freeze/thaw cycles. There are some localized areas where the masonry units have completely disintegrated. The largest area being approximately 4 ft2 (0.37 m2). Is it feasible to remove the deteriorated masonry material, down to a sound surface, and shotcrete the face to restore (or exceed) the structural integrity of masonry units? If so, will this restore the structural integrity of the segmental retaining wall?
Shotcrete is routinely used for the repair of deteriorated concrete masonry and brick. Shotcrete should easily have a minimum compressive strength of 4000 psi (28 MPa) when properly shot and cured. According to the National Concrete Masonry Association, current CMU units have a minimum 2000 psi (14 MPa) compressive strength. Older CMU had a lower 1500 psi (10 MPa) minimum. Thus, the shotcrete placement will be significantly stronger and less permeable than the in-place CMU. This should give the wall better resistance to saltwater and freeze-thaw exposures thus extending useful life.
Depending on the depth of the new shotcrete placement, you may consider mechanically tying the shotcreted layer back to the sound CMU with epoxy or mechanically embedded anchors or j-bolts. Thicker sections may also benefit from the use of a steel wire mesh or fibers.
When shooting onto existing CMU sections, the surface must be properly prepared and then shotcreted with proper shotcrete materials, equipment, and placement techniques. Shotcrete placed onto an existing CMU surface will provide an excellent bond IF the following conditions are met:
- Make sure the surface is roughened and clean.
- The amplitude of roughness should be +/- 1/8th in. (3 mm) or more.
- A high-pressure water blaster (5000 psi [34 MPa] or more) or abrasive blasting can help to roughen and clean the surface.
- Bring the CMU surface to a saturated surface dry (SSD) condition. This means the surface feels damp, but water is not picked up on a hand.
- Make sure the shotcrete placement is properly executed with high-velocity placement and quality materials.
- The shotcrete should have a minimum 28-day compressive strength of 4000 psi (28 MPa).
- Be sure the shotcrete contractor is using an air compressor able to produce at least 185 CFM (5.2m3/min) for wet-mix and 375 CFM (10.6 m3/min) for dry-mix (gunite) of air flow at 100 to 120 psi (0.7 to 0.8 MPa).
- Use of an ACI-certified shotcrete nozzleman is recommended.
- No bonding agent should be used. It will interfere with the natural bonding characteristics of shotcrete placement.
Finally, without details on the loading conditions, and structural details of the original construction, we cannot comment on the structural integrity of the repaired wall. You should contact a professional engineer experienced in concrete repair to evaluate the structural integrity of the wall when repaired.
Board Position Statement
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DownloadASA Outstanding Shotcrete Awards Program
The ASA Outstanding Shotcrete Project Awards Program exists to recognize excellence and innovation on projects in which the application of shotcrete has played a significant role.
ASA’s Annual Outstanding Shotcrete Project Awards Program provides an exciting real-world demonstration of the exceptional advantages of placing concrete via the shotcrete process. Many sustainability advantages are also inherent in the shotcrete process and play a significant role in winning projects as well as the project owner’s ultimate decision to use shotcrete as the method of concrete placement. Projects must be completed between January 1, 2021, through September 1, 2023, and can be submitted in the following areas: Architecture │ New Construction, Infrastructure, International Projects, Pool & Recreational, Rehabilitation & Repair, Underground.
To assist in your submission, we have provided submission resources to inform you of the submission guidelines, a list of questions, and a copy of the owner release form. Please email any questions to [email protected].
Award Archive
2023 – Nineteenth Annual Outstanding Shotcrete Project Awardees
Outstanding Architecture | New Construction Project
American Museum of Natural History, Gilder Center | New York, NY
Project Name:
American Museum of Natural History, Gilder Center
Location:
New York, NY
Shotcrete Contractor:
COST of Wisconsin Inc.
Architect/Engineer:
Studio Gang
Material Supplier/Manufacturer:
Tec-Crete Transit-Mix Corp
Equipment Manufacturer:
REED Shotcrete Equipment
General Contractor:
AECOM Tishman
Project Owner:
American Museum of Natural History
Outstanding Infrastructure Project
Ross Street Underpass | Salmon Arm, BC, Canada
Project Name:
Ross Street Underpass
Location:
Salmon Arm, BC, Canada
Shotcrete Contractor:
Ocean Rock Art Ltd and LRutt Contracting Ltd.
Architect/Engineer:
Binnie Civil Engineering Consultants
Material Supplier/Manufacturer:
Salmon Arm Ready Mix
Equipment Manufacturer:
REED Shotcrete Equipment
General Contractor:
Kingston Construction
Project Owner:
City of Salmon Arm, BC
Outstanding International Project
Shotcrete as Roadside Slope Protection in Brazil | SP 333 Highway, São Paulo, Brazil
Project Name:
Shotcrete as Roadside Slope Protection in Brazil
Location:
SP 333 Highway, São Paulo, Brazil
Shotcrete Contractor:
Unicom Construções e Tecnologias and Construtivas LTDA
Architect/Engineer:
APG Assessoria Projetos Geotecnia
Material Supplier/Manufacturer:
MCC Muriam Concreto LTDA
Equipment Manufacturer:
Schwing Stetter / Tunelmak
General Contractor:
Entrevias Concessionária de Rodovias S.A
Project Owner:
Entrevias Concessionária de Rodovias S.A.
Outstanding Pool & Recreational Project
Shaw Residence | Duck, NC
Project Name:
Shaw Residence
Location:
Duck, NC
Shotcrete Contractor:
Artisan Pools NC
Architect/Engineer:
Waterforge and Kitty Hawk Engineering
Material Supplier/Manufacturer:
CnL Concrete
Equipment Manufacturer:
REED Shotcrete Equipment
General Contractor:
Artisan Pools NC
Project Owner:
Greg and Vicky Shaw
Outstanding Repair & Rehabilitation Project
O’Hare Plaza West Drive and Executive Garage Restoration | Chicago, IL
Project Name:
O’Hare Plaza West Drive and Executive Garage Restoration
Location:
Chicago, IL
Shotcrete Contractor:
Bulley & Andrews Concrete Restoration
Architect/Engineer:
WGI
Material Supplier/Manufacturer:
Sika STM/Glenrock;
Equipment Manufacturer:
REED Shotcrete Equipment
General Contractor:
Bulley & Andrews Concrete Restoration
Project Owner:
JLL
Outstanding Underground Project
Rondout Bypass Tunnel | New York, NY
Project Name:
Rondout Bypass Tunnel
Location:
New York, NY
Shotcrete Contractor:
Patriot Shotcrete
Architect/Engineer:
DELVE Underground
Material Supplier/Manufacturer:
Bonded Concrete
Equipment Manufacturer:
Western Shotcrete Equipment
General Contractor:
Kiewit Shea Constructors, AJV
Project Owner:
New York Department of Environmental Protection
Honorable Mention Project
The Neville Island Bridge | Coraopolis, PA
Project Name:
The Neville Island Bridge
Location:
Coraopolis, PA
Shotcrete Contractor:
Sofis Company Inc.
Architect/Engineer:
SAI Consulting Engineers
Material Supplier/Manufacturer:
The Quikrete Companies
Equipment Manufacturer:
Gunite Supply & Equipment Co.
General Contractor:
Trumbull Corporation
Project Owner:
Pennsylvania Department of Transportation
Honorable Mention Project
Moyie Dam Repair | Bonner’s Ferry, ID
Project Name:
Moyie Dam Repair
Location:
Bonner’s Ferry, ID
Shotcrete Contractor:
S & L Underground
Architect/Engineer:
JUB Engineering
Material Supplier/Manufacturer:
Oldcastle Precast and REED Concrete Pumps
Equipment Manufacturer:
REED Shotcrete Equipment
General Contractor:
S & L Underground
Project Owner:
City of Bonner’s Ferry, ID
Shotcrete Consultant/Quality Inspections:
Leo Waddell, Shotcrete Consulting
Honorable Mention Project
Water’s Edge | Greenwich, CT
Project Name:
Water’s Edge
Location:
Greenwich, CT
Shotcrete Contractor:
Drakeley Pool Company
Architect/Engineer:
James Doyle Design Associates
Material Supplier/Manufacturer:
O&G Industries
Equipment Manufacturer:
Schwing America
General Contractor:
Drakeley Pool Company
Project Owner:
Nordic Custom Builders
Enhancing Efficiency and Safety in Concrete Shaft Restoration: A Shotcrete Success Story
In September 2021, American Concrete Restorations Inc. was contracted to perform 60 yd³ (46 m³) of concrete repairs to an existing shaft that is used to access an underground tunnel system in a southern suburb of Chicago, IL. The job was for the Metropolitan Water Reclamation District of Greater Chicago, Thornton Construction Shaft. The dimensions of the shaft are 250 ft (76 m) deep and 30 ft (9 m) in diameter, and the only access is from the top using a crane basket. The project specifications called for the use of a polymer-modified, bagged product using the formand-pour method to replace the old concrete.