difference between quartz and quartzitic gravel

huangyhg

difference between quartz and quartzitic gravel
the aci 224-01 8.3.2 states "typically, some concretes of highly quartzitic gravels have a low strain capacity and a high modulus of elasticity. concretes with a low strain capacity are much more sensitive to shrinkage due to drying (and to a decrease in temperature) and will be subjected to a greater amount of cracking."
however in the same aci 224-01 3.4.2 states "quartz, limestone, dolomite, granite, feldspar, and some basalts can be classified as higher-modulus aggregates, which result in lower shrinkage properties of concrete."
is quartz and quartzitic gravel the same thing? if so, aci is really contradicting themselves
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quartz is a crystalline mineral while quartzite is a metamorphic rock. both are formed from silica but are otherwise quite different.
ok thanks for the clarification