Pure Phase Encode Magnetic Resonance Imaging of Concrete Building Materials

Pure Phase Encode Magnetic Resonance Imaging of Concrete Building Materials 

Concrete is a composite material composed of cement paste with interspersed coarse and fine aggregates. Cement paste is a porous material with pore sizes ranging from nanometers to micrometers in size. The large pores are known as capillary pores and the smaller pores are gel pores (i.e., pores within the hydrated cement gel). These pores contain water and within the water are a wide variety of dissolved ions. The most common pore solution ions are OH , K+ and Na+ with minor amounts of S042 and Ca2+. The microstructure of the cement paste is a controlling factor for durable concrete under set environmental exposure conditions. 

The sensitivity of Magnetic Resonance (MR) to the local concentration, molecular dynamics and molecular environment of these nuclei make it well suited for the study of deterioration processes in concrete materials. Hydrogen (water), lithium, sodium, chlorine and potassium are all MR sensitive nuclei and play an important role in cement chemistry. The ability of MRI to spatially resolve and non-destructively examine test samples as a function of treatment or exposure has the potential to provide new insight to better understand deterioration mechanisms and mass transport properties of concrete materials. 

The non-destructive nature of MRI is critical to undertaking long duration experiments that require measurements to be made at discrete points in time. 

For example, measuring the ingress of ions due to diffusion is a very slow process 

---