Chen – A Coupled Nanoindentation/SEM-EDX Study on Low Water/Cement Ratio Portland Cement Paste – Evidence for C-S-H/Ca(OH)2 Nanocomposites

J. J. Chen, L. Sorelli, M. Vandamme, F.J. Ulm, and G. Chanvillard

A low water/cement ratio (w/c = 0.20) hydrated Portland cement paste was analyzed by grid-nanoindentation coupled with SEM-EDX analysis at each indentation point. Results indicate that, in microvolumes where C–S–H and submicron Ca(OH)2 are present, increasing fractions of Ca(OH)2 increase the local indentation modulus (and hardness), yielding values above those reported for high-density (HD) C–S–H. Micromechanical analyses furthermore indicate that the C–S–H/Ca(OH)2 composite is not a simple mixture of two independent phases, but, in fact, an intimate nanocomposite where the nanoscale Ca(OH)2 reinforces C–S–H by partially filling the gel pores of C–S–H.



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