Is it critical for the early and intermediate compressive strength at 3 and 7 days, respectively, to be met for shotcrete applications for a rock fall face if the 28-day compressive strength is met?

Compressive strength at 1, 3, and 7 days can be important to all for subsequent operations. In general, 7-day strengths are a good indicator of the ultimate 28-day strength. The need for early strength is an engineering and construction sequence issue, not a normal or typical shotcrete requirement.