Rock Stabilization of Two Historically Sensitive Rock Slopes using Shotcrete

The need to stablize these rock slopes was driven by the construction of the Hudson-Bergen Light Rail Project, which was being extended into Weehawken, NJ. The location of the light rail was along the base of the Palisades in Hoboken and Weehawken. The need to stablize these rock slopes was driven by the construction of the Hudson-Bergen Light Rail Project, which was being extended into Weehawken, NJ. The location of the light rail was along the base of the Palisades in Hoboken and Weehawken.

Silica Fume in Shotcrete

Silica fume is a highly pozzolanic mineral admixture that has been used mainly to improve concrete durability and strength and as portland cement replacement. Silica fume has been used primarily in the United States, Canada, and the Scandinavian countries, but is now finding increasing use elsewhere in the world.

Steep Slope Stabilization with Fiber-Reinforced Shotcrete

For the past 150 years or so, roads have been built through the mountain passes in the western U.S. and Canada. Sometimes these roads led to mines; sometimes they started as logging roads. Some were built for access roads for the railroad. Many were built so that people could drive wagons, stagecoaches, and later, automobiles to their destinations. As time went on, some of these roads were abandoned, while others were turned into highways and scenic byways. These roads can be seen on maps, criss-crossing through mountain passes, valleys, and wherever passage was possible. Many of these roads were constructed along mountain slopes, carved out using the largest equipment available at the time, sometimes by hand work, and sometimes by blasting through rocky areas. Road conditions in some of these areas can change dramatically throughout the year. In the mountains, vast amounts of snow can accumulate during the course of just a few days. Sometimes there are heavy rain storms. There can be snow avalanches and mudslides from the rain and snow. In times of drought, vegetation might dry out and die, leaving slopes exposed to erosion, increasing the probability of avalanches and mudslides. Because of varying climactic conditions, freezing-and-thawing cycles, radical changes in the amount and nature of moisture, steepness of slopes, and other factors, slopes need to be stabilized so that rocks, trees, debris, and other factors not listed do not unearth them-selves and become hazards to all things below them. One of many ways to secure and stabilize highway slopes is by the use of fiber-reinforced shotcrete (FRS), usually along with either rock bolts or some other mechanical device drilled into the rock or slope. This paper provides an overview of why fiber-reinforced shotcrete is an excellent choice in lieu of plain shotcrete reinforced with either welded wire mesh or rebar mats for such slope stabilization work.

Specification of Shotcrete Toughness

Fiber-reinforced shotcrete has become an established material for ground support in tunnelling and mining applications as well as in new construction and infrastructure repair. Designers and specifiers frequently require such shotcrete to maintain some quantifiable postcrack strength or toughness. Until the newly published round panel test method (ASTM C 1550-03)1 becomes more widely used, North American designers and specifiers will likely continue to refer to toughness parameters as determined by the beam test method (ASTM C 1018).2 The following sections discuss various toughness parameters associated with this beam test and their significance.

Shotcrete Repair Saves Baltimore Bridges

This Shotcrete Classic was selected for reader interest. While first published 23 years ago, most of the dry-mix shotcrete technology described for repair of bridges still remains relevant today. There are a few areas where things have changed. Small line wet-mix shotcrete equipment is now available with suitable start and stop characteristics for small volume wet-mix shotcrete repair of bridges and other structures and is now also widely used for this purpose. Also, with proper surface preparation and the incorporation of silca fume in shotcrete, bonding agents are now seldom used, or needed. Good guidance regarding current recommendations for shotcrete repair of bridges can be found in the AASHTO-AGC-ARTBA Task Force 37 Report œGuide Specification for Shotcrete Repair of Highway Bridges, published in 1998 by AASHTO in Washington, DC.

Architectural Finishes for Retaining Walls

What kind of architectural finishes are possible with shotcrete? From the most basic natural gun finish to exotic carved sculptures, from the gray color of regular portland cement concrete to custom-colored and stained mixtures, shotcrete can take on many different types of finished appearance. Today™s designers are continually challenged to provide quality finishes that fit the surroundings; and in many applications, shotcrete can fill these needs. Cut and Finish Methods Achievement of an architectural finish starts with the establishment of the final surface plane. Perimeter forms and guide wires are used to

Jefferson Street Bridge: The “Million Dollar Bridge” Listed on the National Register of Historic Places

Dubbed the “million dollar bridge” by town residents, referring to the cost of building the structure in 1921, the Jefferson Street Bridge in Fairmount, WV, is a three-span reinforced concrete arch bridge that crosses the Monongahela River. Listed on the National Register of Historic Places, the bridge was originally designed by The Steel Engineering Company of New York and was dedicated to the town of Fairmont on May 20, 1921. The John F. Casey Company of Pittsburgh completed the original construction.
Having been used by Fairmont residents for more than 70 years, the Jefferson Street Bridge needed restoration work to ensure the continued safety of the structure. The goal of the restoration project was to take down 80% of the structure with only the original arches remaining intact, reconstruct the bridge with new materials, and retain the same appearance as the original 1921 design.
In 1998, the Mosites Construction Company of Pittsburgh began the two-year restoration project. Working with architectural firm Howard Needles Tammen & Bergendoff (HNTB) of Alexandria, VA; engineering firm Gannett-Fleming of Pittsburgh; and RCS Consulting of Ripley, WV, Mosites Construction Company had to overcome numerous challenges related to the design and location of the bridge. Before any demolition could be done, precautions were taken to protect a communi-cations fiber optic cable that ran under the south sidewalk of the bridge. Also, to preserve the six original arches, special engineering methods were employed to keep the demolition of other areas of the bridge from harming the arches. To duplicate the original appearance of the structure parapet and light poles, special architectural precast forms were designed.
To help restore the piers and arches, Mosites Construction Company turned to The QUIKRETE® Companies for its high-quality commercial-grade products. Using 6400 m2 (69,000 ft2) of 37.5 mm (1.5 in) thick pneumatically applied QUIKRETE® Gunite MS®, Mosites successfully restored all four sides of the existing arches.

Shotcrete for Ground Support: Current Practices in Western Canada

Historically, in Western Canada, the stabilization of rock slopes and construction of excavations have been achieved using methods such as soldier piles and lagging or construction of cast-in-place concrete retaining walls. In the case of reinforced cast-in-place concrete, there is a requirement for erection of formwork, fixing of reinforcement, pouring the concrete mixture, and vibration to ensure good concrete consolidation and steel encapsulation. These methods have proven to be relatively ineffi-cient and costly in many cases. In recent decades, however, the use of shotcrete for ground support has seen increased use, as shotcrete has allowed