Mesh3 cards are suitable for measuring dosage in concrete and are specifically designed for MCNP simulations to accurately calculate radiation dose. Your friend's mention of mesh1 cards may be misleading, as they are primarily used for measuring neutron fluence rather than radiation dose. For clarity on usage, it's advisable to consult knowledgeable sources or explore online examples. Numerous resources exist that demonstrate the application of tmesh cards in MCNP simulations. Understanding the correct card type is essential for accurate dosage measurement in concrete.