Techniques for determining some microstructural parameters in glass reinforced cement

Two important parameters which control the fracture behaviour of glass fibres in cement composites, whether they contain one fibre type or are hybrids of two fibre types, are the perimeter of the glass strands in contact with hydrated cement and the way in which glass filaments fracture in multi filament strands. In scanning electron microscopy (SEM) observations, much improved images were obtained by detecting back scattered electrons rather than secondary electrons. This improvement gave good contrast between the fibre strands and the matrix, hence the perimeter of the glass strands could be determined using an image analyser. The progression of filament fracture within a strand was examined using two techniques, acid dissolution and light transmission through the filaments. These techniques showed that strands tend to fail progressively in hybrid composites containing glass and polypropylene fibres and that glass fracture continues to occur after the peak load has been reached.