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TECHNICAL PAPER

Figure 5: (a & b) Quarzitic aggregate; (c & d) Medium grained granite; (e, f, g & h) Fine to very fine rained texture of granite [22] ;
(i) Calcite [21] ; (j) Dolomite [21] ; (k) Calcite with different interferences [21] , and (l) Calcite with mineral chlorite [21]

particles of weathered siliceous rocks. Carbonaceous rocks may approximate estimation on the distribution of dark minerals
erode fast to the action of water and or surface abrasion with presents in the sand, the different colour interferences resemble
other rubbles due to their low abrasive resistance (Table 3). their state or degree of weathering. To obtain river sand thin
Feldspars, quartz, and high resistant heavy metal minerals may sections, cement mortars were prepared. Figure 6 (e) represents
be present in the river aggregates. Their state, and degree river sand in a thin section. The petrography of river sand is
of weathering provides special characteristics in thin sections typified by specks of weathered quartz, and feldspar with rusted
under polarized microscopy. Figure 6 (c and d) represents river or stained morphology. Figure 6 (f) illustrates a quartz grain
sand particles of 600 µm under CPL and PPL. Apart from an which is recrystallized due to weathering and exhibit different

THE INDIAN CONCRETE JOURNAL | AUGUST 2022 15