Recruiting, training, and retaining skilled shotcrete nozzlemen is mission-critical for a company’s success. Virtual, immersive training offers an effective, engaging mode of learning that supports the modern trainee. For beginning nozzlemen, virtual reality training gives them a safe, repeatable experience that can be completed in a classroom, free of job costs. Practice without cost or risk also helps improve job performance and satisfaction. These disruptive virtual reality (VR) technologies can provide safe, hands-on learning experiences without the field costs associated with hands-on training. Virtual learning is also valuable in today’s socially distanced world with its shifting remote learning requirements. Interactive digital tools will deliver meaningful, adaptive training for skilled trades now and in the future. Though some level of hand nozzling experience is still needed the best nozzlemen will be trained, in part, using virtual reality.
Y Not Try a Double Nozzle System
Although many shotcrete workers “claim” to be capable of placing massive amounts of concrete in a daily shift, or shooting with the pump turned “wide open,” in reality, the nozzleman tends to ultimately be the limiting factor on production speed and daily placement volume. Plain and simple they get tired. Shooting too fast diminishes accuracy and overall quality.
Can carbon nanotubes be used in shotcrete?
Shotcrete is a placement method for concrete so most admixture or supplemental cementitious materials that can be used in cast concrete will work with shotcrete placement. In fact, shotcrete contractors have been some of the most innovative adopters of new concrete technologies. Silica fume (microsilica) is a ultrafine particle 100 times smaller than cement that enjoys early and wide use in shotcrete due to its ability to make concrete stickier and more cohesive. This facilitates overhead placements and can provide thicker layers. Shotcrete has also used other ultrafine and nanoparticles, like colloidal silica, clay-based particles and the carbon nanotubes you mentioned.
The ultrafine and nanoparticles can provide many benefits to fresh concrete, as well as hardened properties. This may include:
• Improve the pumpability of wet-mix concrete;
• Reduce rebound and dust due to increased “stickiness”;
• Ease the finishing process;
• Reduced permeability by filling pores between cement in the paste;
• Enhanced corrosion resistance for embedded reinforcement;
• Enhanced resistance to chemical attack.
Can a gunite bridge surface be painted? And if so, what preparation/materials are recommended.
Yes, shotcrete is a placement method for concrete, so any coating appropriate for concrete would be applicable specify new concrete should be a certain age before applying their coating. Generally, the concrete surface should be clean and dry before coating. The surface texture provided on the shotcrete can affect the coating application. A hard, smooth steel trowel finish will tend to be quite slick, and the coating may not bond as well as a floated or sponge finish. A light abrasive blast may be considered to roughen the surface and give more bond. If using a gun or rodded finish for the shotcrete, the coating will generally require quite a bit more material to be able to fill the depressions in the surface.
The ASA Contractor Qualification Program (CQP) is a straight-forward program that helps establish a shotcrete contractor’s qualifications by review of the contractor’s previous work. This review is conducted by the Review Task Group within the Contractor Qualification Committee, whose members have extensive experience in successful shotcrete work. This qualification program provides a distinct service to the industry by assuring specifiers that shotcrete contractors reviewed here have a proven work record for completion of successful projects of similar work and scope. This qualification program is based on the ASA Board Position Paper, “Qualifications of the Shotcrete Construction Team.”
Levels of Qualification:
There are two levels of qualification, Level I and Level II in the process(es), i.e. wet-mix or dry-mix, appropriate to the work performed by applicant.
- Shotcrete Contractor (Level I) – Representative projects which have thin, lightly-reinforced shotcrete sections that can be easily accessed and placed would be considered “Level I”.
- Shotcrete Contractor (Level II) – Representative projects which have thick, heavily-reinforced sections or sections with difficult access would be considered “Level II”.
Program Requirements:
- Identify a Qualifying Individual (QI) to attend the required CQ Seminar and successfully complete the required written exam. Please contact ASA for the next available seminar: [email protected] | 248/983.1702. (The seminar will also provide helpful insights for completion of the CQ application.)
- Documentation of company equipment and shotcrete staff, including list of certified nozzlemen
- Documentation of FIFTEEN (15) projects successfully completed in the last 3 – 5 years (per level pursued) representative of the level of qualification pursued in the application.
Click here to review the full policy for help in completing your application
If you have any questions, please contact ASA at 248.983.1702 or [email protected]
Copyright © American Shotcrete Association
All Those Small Numbers We Ignore – What Do They Mean?
We have all seen those small letters and numbers that mark practically everything we use in construction. To most, these are meaningless markings that are meant for someone else. However, with shotcrete, nothing could be farther from the truth.
Getting Back to Work
The COVID-19 Pandemic affected our lives in ways none of us have ever experienced in our lifetimes. I’ve been in construction for 45 years and I have never seen our economy shut down, businesses closed, or people required to stay at home. In 2001, the attacks of September 11th temporarily shut down air travel and the stock market, but the American economy remained intact and air travel resumed within a couple of weeks. However, COVID-19, has affected our lives in ways that we could never have imagined. Schools and universities were closed; professional, collegiate and high school sports seasons were suspended and canceled; and restaurants and businesses were closed. We were told to stay home and work remotely, if possible, and businesses across the country followed those directives.
OSHA’s Respirable Crystalline Silica Rule on Shotcrete Operations – Revisited
This is a revised version of the original article printed in the Summer 2016 of Shotcrete magazine before the OSHA rule was put in place. This revision has added site measured values for air monitoring of crew members on shotcrete projects, as well as ASA’s response to OSHA’s request for information in August 2019. Also, included is a short section on applicable respirators. With this revision our intent is to put the current information you need about the OSHA rule and its impact on shotcrete operations in one place for ready reference.