Monday, January 2, 2012

9 Questions Before Making Shotcrete Mix Design

Before making a mix design for shotcrete or sprayed concrete, it is needed to get sufficient information from the clients. Adequate support information will be resulted in technically and economically effect for the work. A proper mix design assure a successful trial and thus, successful application on site.

Hereafter is a list of 9 questions to the ask the clients prior to making a shocrete mix design:

1. The location of shotcrete to be applied? Slope stabilization, overhead and wall in tunnel
2. Wet or Dry process will be applied? Normally, dry process for slope stabilization, wet process for tunnel lining.
3. The requirement of early strength (8 hours, 72 hours, 7 days, 28 days) and the final strength at each location.
4. Slump requirement (for wet process only)
5. What accelerator admixture to be used? Please note that it would be better to use liquid admixture in rainy season.
6. What is the concrete spraying machine to be used? Rotor Machine (for both wet and dry process) or Pump Machine (wet process only)
7. What kind and type of cement to be used (cement should be super fine. Blain Surface fineness is greater than 4000 square centimeter per gram) PC cement is most suitable for early strength requirement.
8. A dispenser system need to be installed in case wet process is used. Is such liquid dosing unit available?
9. Any other information is helpful in designing shotcrete mix?

Once these question get answered, the mix designing process can be started. For shotcrete or sprayed concrete, trial is a must be prior to the issue of mix design for actual application.


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