Monday, June 25, 2012

Shotcrete Mix Designs

Following are two typical mix designs for shotcrete, one for dry process and one for wet process.As a fact concrete, shotcrete production is a “local” business, the admixture product range may differ from one country to another. And this especially due to the type and quality of cement.

Dry process

Quantities in bulk as dry process
Cement 350 kg.
Sand and Aggregate: 1650 kg (58% Water: to be added at the nozzle with at leas 2 bars more pressure than delivery pressure but not less than 5 bars
Powder type Sigunit D 54 AF (3 to 6%) to be added while mixing dry component at the BP as long as moisture of plain mix is < 5%. Mix to be used within the 2 hours. Or direct dosage by hand in the hopper Liquid type: Sigunit L 54 AF or Sigunit L 553MY (as well non caustic accelerator). L 54 AF or L 53 MY as alternative of L14AF as show a higher Specfic Gravity then L14AF)

Wet process

 (typically 5 MPa after 8 hours, > 30 MPa at 28 days = underground preliminary support concept)
Cement: 470 kg/m3 (min if PCB = blended cement is considered)
W/C < 0,45
Sikament 163EX: 1,0 to 1,2%
Sand & Aggregate: 1650 – 1700 kg/m3 (58% < S/A < 65%)
Only Liquid type: Sigunit L 54 AF or Sigunit L 553MY (as well non caustic accelerator)
Liquid dosing unit eg Aliva AL 403 required as accelerator added at the nozzle or 3 m back from nozzle.

Note: depending on equipment use, required slump when discharging should be about 180 mm for rotor machine and about 150 for pump. Therefore the dosage of SM 163 EX in combination with a W/C < 0,45 and suitable grading curve should be adjust to obtain this slump.


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