Cementitious Syntactic Foam
The first three images are of pure cement paste. The composite material at hand is a cementitious syntactic foam. Glass Micro Balloons of average size 40um is used. Some of the larger and thinner walled glass micro balloon are visibly broken and infiltrated by the cement matrix. Also, calcium hydroxide (Portlandite) crystals are clearly visible in many of the images. In some images with high maginification, ettringite needles are also visible.