Cement sheath integrity is very important in drilling and completion. Several additives are used to aid the process of preparing flow able cement slurry, gaining sufficient strength over time. Sheaths need to be elastic and resilient and withstand several temperature and pressure cycles over the life of the well. Today's technology has made available very sophisticated experimental methods for the assessment of the behavior of slurries under various harsh well conditions. Here, we present a comprehensive laboratory assessment of the properties of two different non-foamed cement slurries, by combining initial tests, such as rheology, fluid loss, and thickening time, with strength, ultrasonic and advanced Nuclear Magnetic Resonance (NMR) measurements, at both room and elevated pressure and temperature. In this way it is possible to correlate cement microstructure with the mechanical properties of cement at borehole conditions, acquiring critical information for designing better sheath integrity. A very good correlation was found between the microscopic NMR data that probe the evolution of the average pore size and consequently the kinetics of hydration with macroscopic compressive strength data. In view of this approach, the multifunctional effect of a latex based additive on the hydration properties of class G cement was investigated.