Studies on the engineering properties of different rock types provide a prior knowledge on the quality of such rock types as well
as potential locations of suitable sources for the industry. The property “soundness” of a material measures the tendency to split into
pieces similar to physical weathering during expansion and contraction processes within it. This soundness varies according to the
type of minerals in a rock and its’ origin. If rocks are using for aggregates for concrete or other applications the estimation of their
soundness is necessary. With the aim of that, fresh rock samples of different rock types were collected from quarries and exposed
rocks in different locali-ties in Sri Lanka to study the variation of soundness property in different rock aggregates. Samples were
tested in the geotechnical engineering laboratory using sodium sulfate solution according to the Standard Method ASTM C88-99a.
The rock types were Chranockite/charnockitic gneiss, garnet/hornblende/biotite gneiss, Microcline/Granitic gneiss, Garnet/biotite
gneiss, Marble, Hornblende biotite gneiss, Quartzite, pegmatite, pink granite and Miocene limestone. Accordingly charnockite/
charnockitic gneiss shows the lowest loss of weight percentage as the highly sound rock for aggregates. Miocene limestone is the
highly unfavorable rock.
Keywords: Soundness; Rock types; Aggregates; Constructions; Civil engineering