The mission of the International Concrete Repair Institute (ICRI) is to be a leading resource for education and information to improve the quality of repair, restoration, and protection of concrete and other structures.
Overhead Dry-Mix Shotcrete
In overhead shotcreting, it is important to first make sure that the reinforcing steel and/or mesh is tightly tied and anchored in place.
Structural Shotcrete Overhead
As a contractor, I have frequently been asked if shotcrete can be used for overhead applications.
Overhead Shotcrete
When you say overhead, people invariably think of fixed costs, salaries, and the general costs of running a business.
Shotcrete for Structural Repair of Key Light Rail Facility in Boston
In 1922, the Boston Transit Commission built Shawmut Junction, a ?yover located in Boston, MA.
Curing Silica Fume Shotcrete with Wet-Sprayed Cellulose
Chloride-induced corrosion is the primary cause of deterioration in many concrete bridges in Canada and the northern United States. For corrosion to take place, the chloride ions permeate through the interconnected pores of the concrete toward the embedded steel reinforcement and attack the passive layer that forms around the steel during the hydration process of concrete. Once this passive layer is destroyed, corrosion proceeds, resulting in a reduction in the structural integrity of the structure in addition to the onset of spalling of the concrete cover. To restore the serviceability of the structure and extend its service life, the deteriorated concrete is usually removed, the reinforcement is replaced if necessary, and the concrete is replaced with a durable repair material that has high resistance to chloride ion transport. In the province of Ontario, Canada, partially deteri-orated concrete bridge sofï¬ts are typically repaired with shotcrete containing silica fume.
Quality Management of Shotcrete in North America
As for all construction materials, a proper program of quality management should be implemented in shotcrete construction to protect the owner™s investment. This article briefly examines typical shotcrete Quality Management (QM) practice in North America. QM can be considered to be comprised of Quality Assurance (QA) and Quality Control (QC) functions.
Specified Dilemmas
On shotcrete sites, it is not unusual to hear comments starting with œIn a perfect world, … Of course, in a perfect world,there wouldn™t be any shotcrete because there wouldn™t be anything to repair or strengthen. Fortunately, there are plenty of imperfections in the jurisdiction where most of my work comes from. We ï¬nd them on cracked and ï¬ssured rock slopes next to highways, in ground to be tunneled for infrastructure improvements, in old masonry walls, washed-out bridge foundations, and in marine piers where the chloride concentration at the rebar level in the concrete exceeds the reasonable limit set for the onset of corrosion.
Shotcrete – The Repair Solution for the Memorial Tunnel
In 1953, the Memorial Tunnel in Standard, WV, was constructed as a two-lane, 2800 ft (853 m) tunnel with semi-transverse ventilation. The owner operated the tunnel until the mid-1980s when a four-lane bypass was constructed to upgrade the turnpike to current Interstate standards. The tunnel was abandoned until 1989 when the Federal Highway Administration (FHWA), in conjunction with the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE), embarked on the Tunnel Fire Ventilation Test Program using funding from the Central Artery Project.
The test program consisted of performing controlled test ï¬res up to 100 megawatts. These intense ï¬res then provided valuable information for the design of ceiling wall partitions and the protection of facilities for power, ventilation, and lighting. In addition, it provided the opportunity to develop and evaluate methods of proper ventilation control of a tunnel under various ï¬re scenarios.
Parsons Brinckerhoff was retained to perform the test program. As part of that test program, an evaluation of the structural condition of the tunnel was performed and structural repairs were designed. A critical part of the design was to insulate structural portions of the tunnel for temperatures in excess of 2000 °F (1143 °C).
The rehabilitation program for the reuse of the tunnel required the sealing of all cracks in the tunnel liner because the bedrock around the tunnel contained low-flashpoint cannel coal. In addition to sealing the cracks, extensive structural rehabil-itation of the liner was performed to repair damage caused by the excavation for the bypass on the adjacent highway. Numerous products were evaluated to determine which would provide suitable fire protection for the structural elements of the ceiling and for mechanical equipment anchorages. The test program included the use of traditional venti-lation with a tunnel ceiling and tests with the ceiling removed for the use of jet fans. The construction contract for the rehabilitation of the tunnel and the removal of the ceiling had a projected cost of $10 million.
During the test program of 98 ï¬res, routine inspection of the tunnel was performed to evaluate the performance of the ï¬reprooï¬ng. Based on the performance of certain structural elements, changes were made in the use of structural ï¬re-prooï¬ng and code requirements for the protection of equipment. After the test program in 1991, the