Environmental and Social Impact Assessment - Gibe III

Gibe III – Environmental and Social Impact Assessment 300 ENV R CS 002 C - A9003099
Photo 3.3: Trachyte materials from the diversion tunnels
3.15.5 Pozzolanic materials (ashes, ignimbrite)
The pozzolanic materials found on site will constitute a relevant portion of the cementitious materials
required for the RCC dam.
Two suitable materials are available: natural ashes and ignimbrite.
Tests have been carried to confirm the properties of these materials as RCC cementitious materials. The
results show properties quite similar to these of a commercial fly ash.
Both ignimbrite and ashes will be mainly quarried in the left side being the ignimbrite layer on the top just
above ashes layer.
The following photo 3.4 shows the overlapping between ignimbrite and ashes in the stratigraphic succession
typical in the area.
The ignimbrite might be possibly used also as an additional aggregate source for the RCC even if in small
quantities.
The sub-horizontal layer permits a regular quarrying without the opening of high fronts. This set up will
facilitate the recovering of natural vegetation once the quarry will be abandoned.
CESI SpA - Mid-Day International Consulting Engineers Page 69