Nanomechanical structure-property relations of dynamically loaded reactive powder concrete

Abstract

Low water-to-cement ratio ( w / c ) reactive powder concretes (RPCs) exhibit much higher compressive strengths compared to conventional concrete through optimized particle packing and specialized curing regimes. The high strain-rate impact behavior of RPCs was investigated at the macroscale. However, little work has been done to study the fundamental material behaviors and failure mechanisms of RPC under high strain impact and penetration loads at lower length scales. These high strain-rate loadings have many possible effects on RPCs at the microscale and nanoscale, including alterations in the composition and bonding present in hydrated phases such as calcium silicate hydrate (C-S-H), in addition to fracture and debonding. In this work, the possible chemical and physical changes of RPCs under high strain-rate impact and penetration loads were investigated using a novel technique wherein nanoindentation measurements were spatially correlated with chemical composition using electron microscopy. Results indicate that high strain-rate impacts degrade both the elastic modulus and indentation hardness of RPCs and, in particular C-S-H, with damage likely occurring due to microfracturing and debonding. Additional studies will be required to better understand degradation phenomena within C-S-H itself.

Nanoindentation and SEM/EDX characterization of the geopolymer-to-steel interfacial transition zone for a reactive porcelain enamel coating

“…This work builds upon previous research [1,[11][12][13][14][15][16][17][18][19][20][21][22][23][24] that focused on nanomechanical methods for characterizing cementitious materials.…”

“…Once fully cured, a high-precision diamond wafering saw using an oil-based cutting lubricant sectioned the segments. A manual polishing system with a 200 mm diameter platen performed step-wise polishing of the cylindrical samples according to the method described previously [14,19] that used alumina suspensions in ethylene glycol and ethanol (50/50 mixture by volume) down to a particle size of 0.05 µm. A final polish of 0.05 µm was chosen since previous research has shown that a final polish with a particle size of less than 1 µm produces a flat surface for nanoindentation of cementitious materials [1,14,19,20].…”