This lecture covers the application of Monte Carlo methods for multi-particle diffusion in cementitious materials. It explains the concept of a multi-particle Monte Carlo model, the calculation of self-diffusion coefficients, correlated motion effects on diffusion, and vacancy diffusion. The instructor demonstrates how to produce multi-particle, single species Monte Carlo simulations, the impact of site-blocking on correlated motion, and the computational efficiency of vacancy diffusion at high particle densities.