Fig. 7From: Synergetic Influence of Microcrystalline Quartz and Alkali Content in Aggregate on Deterioration of Concrete Railroad Ties Used for 15 Years in High-Speed RailwaysPhotographs taken by polarized light microscope of coarse aggregates from a Brand-new, b Non-cracked, c Longitudinal-cracked, and d Map-cracked. Quartz grains are highlighted by a solid line of circles, and feldspar grains are indicated by dashed ellipses.Back to article page