Important Raw Material—Coarse Aggregate - The Issues and Discussion of Modern Concrete Science - page 25

Fig. 2.1 Schematic diagram of formation process of sedimentary rock, igneous rock, and

metamorphic rock

CaCO 3 . Sometimes, limestone is called calcareous limestone, magnesia limestone,
and siliceous (argillaceous) limestone.
Sandstone is another typical sedimentary rock, including lake sedimentation and
sea sedimentation. Owing to different formation causes, color and density of
sandstone vary a lot from each other. As sedimentary and diagenetic time is short,
most sandstone in China possesses poor mechanical property and therefore cannot
be utilized for concrete aggregate. For example, sandstone, distributed in Shaoguan
in Guangdong Province, Enshi in Hubei Province, northern Shanxi, is unable to be
utilized as coarse aggregate for compressive strength is too low. The author has
never adopted sandstone as coarse aggregate and just seen individual part in China
uses sandstone as aggregate on some datum. Sandstone and limestone are shown in
Figs. 2.2 and 2.3 .

2. Igneous rock

Igneous rock can be divided into rapid cooling (magma ejected to ground, such
as basalt), slow cooling, and temporarily uncooled (magma buried deep in the
earth

s surface which are not ejected out, such as medium-grained or coarse-grained
granite) according to the differences in magma chemical composition, ejection time,
and cooling degree. As a result, performance gap between different igneous rocks
can be very big, just as shown in Fig. 2.4 . Fine-grained granite in Taishan Mountain
of China is a typical igneous rock, the density and strength of which is very high.

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