Geoscience Reference
In-Depth Information
254
255
254
'Semi-dry' sand:cement screed, showing quartz-rich
natural sand fine aggregate (mainly quartz, grey/white)
bound by a matrix of uncarbonated Portland cement
(black). A monofilament polypropylene fibre runs
through the field of view (brightly coloured). Air voids
appear dark green; XPT, ×35.
255
'Semi-dry' sand:cement screed, showing a cement-
rich lump that is the result of inadequate mixing (lower
right) and the remainder of the view exhibits abundant
entrapped air voids (yellow) caused by poor
compaction. Aggregate particles appear white, the
Portland cement matrix appears dark brown; PPT, ×35.
256
257
256
Very poorly compacted 'semi-dry' sand:cement
screed showing a very high abundance (40%) of
entrapped air voids (yellow). Natural sand fine
aggregate particles appear white/black and Portland
cement binder is shown dark brown; PPT, ×35.
257
Anhydrite screed comprising natural sand fine
aggregate including particles of quartz (white, grey),
flint (brown/grey), and glauconite (green), bound by a
hardened matrix of gypsum (grey); XPT, ×35.
258
259
258
Close view of anhydrite screed showing the
matrix of gypsum crystals (light brown). Fine aggregate
particles appear white and air voids are shown
yellow; PPT, ×300.
259
Same view as
258
in cross-polarized light, showing
the matrix of gypsum crystals (light grey) of an anhydrite
screed. Quartz fine aggregate particles appear grey and
air voids are shown dark green; XPT, ×300.
