Resolution of fine fibrous C-S-H in SEM backscatter

Secondary electron mode SEM images of hardened cement paste (obtained on fracture surfaces) have been published since the early 1970s. Most such images emphasized fine fibrous or dendritic C-S-H structures, which are commonly found in porous areas preferentially exposed by fracturing. Such fibrous structures are not generally seen in backscatter-mode SEM images obtained on polished surfaces. Examination with a high-resolution field-emission SEM (FE-SEM) instrument in the backscatter mode resolves these fibrous C-S-H structures, and suggests that failure to image them in conventional backscatter SEM is primarily due to inadequate resolution. (C) 2005 Elsevier Ltd. All rights reserved.