Slope Reinforcement using Shotcrete in Arizona

With more than 7,000 cubic yards (5,350 m3) of shotcrete to be used for slope reinforcement in the Mesa­Payson Highway expansion in Arizona, it may be the biggest shotcrete application in the country. The project consists of shotcreting thirteen freshly-cut mountainsides in the Kitty Joe Canyon of the Matazel Mountain Range on Highway 87 between the cities of Mesa and Payson. The total cost of the 17-mile (27 km) road expansion is $55 million. “The entire project will take more than seven months to complete,” said Mickey Garner, president of Shotcrete Specialties, the sub-contractor. “And we’d be done if it hadn’t been for a freak snow last spring,” she continued. The area had about 3 feet (1 m) of snow just as the company was starting the project.

New Mixture Design and Guide Specifications and Inspector’s Manual

Shotcrete has not traditionally been a material of choice for repair of bridge structures by many state highway departments. One reason for this is that bridge engineers have not been aware of advances in the quality and durability possible with high-performance shotcrete over the last 10 to 15 years. In 1995, an effort was made to help facilitate and encourage the use of shotcrete in bridge repair, especially where it is particularly advantageous: in overhead and vertical surfaces and in thin layers, or a combination of thin and highly reinforced thick layers. The effort was organized by the AASHTO-AGC-ARTBA Joint Committee.

Application and Testing of Shotcrete

In 1989, the Austrian Concrete Society pub-lished a Guideline on Shotcrete that subse-quently served as a reference work and a contractual basis for shotcrete works in tunnel con-struction in Austria and abroad. Other standards,such as DIN 18551, focused more strongly on shotcrete for concrete repair works. At the end of 1998, after several revisions, a new edition of the Austrian Guideline was published that also con-siders recent developments in the field of shot-crete technology. Dealing with a
whole range of issues, from base ma-

Shotcrete Red Hot in Peru

An1amina copper mine is a Sl.2 btltion projcc1 in lhe Andes Mountailh of Peru. The projeci. owned by Canadian mining gi3111S Norandll. J’cck and Rio Afgom, i.s one of the. single largest mining inveso:nents in 1be Americ:iô€€£ at this moment and oomprises the cons1ruction of an open pi1, a co11veyor runnel, a tailings dam. a mill and pon facilities for ¢1’por1 of processed concenlrllle all over the globe.

The Use of Steel Fiber-Reinforced Shotcrete for the Support of Mine Openings

What separates the support of mining open­ings from the support of similar civil engineering structures is the fact that mine openings have to survive large defonnations as a result of changing stress conditions induced by progressive mining. Steel fibers impart to concrete and shotcrete a high degree of ductility which not only allows the shotcrete and concrete linings to absorb important rock movements, but also to increase their bearing capacity by a redistribution of the loads.
The use of shotcrete for the support of under­ground excavations was pioneered by the civil engineering industry. In recent years, the mining industry ha,;; become a major user of shotcrete for underground support. The simultaneous working

Steel Fiber Reinforced Shotcrete, It is time to find out about it.

In an age when the building, tunneling, and in some areas, min­ing industry, is thriving in North America, we in the shotcrete industry should be looking for ways to increase productivity and save on ever-increasing labor costs. This type of thinking often requires the use of products that we either are not familiar with or have never used at all. Since we are in an industry where our chief concerns are keeping a safe workplace, while at the same time, trying to increase production or speeding up project comple­tion time, we are often times unwilling to try new technology because we are afraid of the unknown. We fear a decrease in pro­duction, having to buy new equipment, and worst of all, lost­time accidents.For this reason-the unknown-many shotcrete contractors and mine managers have shied away from the use of steel fibers in their shotcrete. Their arguments against using steel fibers are often the same. “We use mesh or rebar for reinforcement because we know for sure that the reinforcement is in place before we apply shotcrete. That way, we don’t have to worry whether or not we have added the correct amount of steel fibers, or if the steel fibers are mixed uniformly, or if the fibers will do the job at all.” Or, we hear the all too familiar response, “If it is not broken, don’t fix it.”
In my opinion, this “if it is not broken, don’t fix it” attitude is keeping a lot of shotcrete contractors from increased production and greater financial successes. Sure, the economy in North America is strong now in the

Big Bad Curves?, Pumping Fiber-Reinforced Wet-Mix Shotcrete

Making good pumpable concrete or wet­ mix shotcrete is not always easy, especially
when fibers are present Adding fibers to ordinary wet-mix shotcrete sometimes re­
results in nonpalpable or difficult-to-pump concrete. Simply adding superplasticizer 10 fiber-reinforced shotcrete does not always result in a workable mixture.