When we stripped a shotcreted wall we found sand along the base which was unbonded or only lightly bonded. What happened?
This sounds like rebounded sand which collected at the base. Sometimes the rebound hits the back side of reinforcement and is prevented from being thrown clear of the wall. This may collect at the base or at inside corners. Great care is needed in shotcreting to prevent rebound from collecting in the work. Particular attention must be given to shotcreting in the neighborhood of pipes, reinforcement or other obstacles. The use of large reinforcement should be avoided if possible.