Difference between Quartz and Quartzitic Gravel

[yahoo123]

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

 

[apsix]

Quartz is a crystalline mineral while quartzite is a metamorphic rock. Both are formed from silica but are otherwise quite different.

 

[yahoo123]

Ok thanks for the clarification