Does usage of accelerators in Shotcrete affect its strength adversely?
The dosage of the accelerator is a very important aspect of shotcrete technology.
Normally all accelerating admixtures increase the early-age compressive strength when compared with the reference shotcrete. However, compressive strengths at later stage (say 28 and 56 days) show marked reductions for some mixtures when compared with the reference mixture.
It is therefore recommended to minimize the amount of set-accelerator added to any wet-mix shotcrete mixture to limit these long-term reductions in compressive strength.
Similar reductions in quality can be measured for absorption and drying shrinkage, where the values can be increased (while you want to keep them as low as possible) as much as 100 and 50%, respectively.