Figure 5-2.-Conventional graphic soil symbols.Normally, the upper limit ofparticle sizes available is controlled bythe thickness of rock layers and thespacing of cracks or fracturesin therock. The amount of fine particlesproduced during rock crushing operationscan be highly variable. Generally, hard,tough rocks produce few fines, and soft,weak rocks produce large quantities offines. Weak sandstones and granitesusually produce large amounts of sand-sizematerials.Types of Quarry MaterialNatural sand and gravel are notalways available, and it is sometimesnecessary to produce aggregate byquarrying and processing rock. Quarryingnormally is performed only where othermaterials of adequate quality and sizecannot be obtained economically.Many rock types suitable forconstruction exist throughout the world;therefore, the quality and durability ofthe rock type selected depends on localconditions. The following rock types aregenerally easy to quarry, durable, andresistant to weathering, When these arenot available, it may be necessary to usesofter rocks for base courses andsurfacing on a temporary basis. The softerrocks will usually require little or noblasting .Granite.As a dimensionstone,granite is fairly durable and has atexture and color desirable for polishing.As a construction material for basecourses and aggregate, it is not asdesirable as some of the more dense, fine-grained igneous rock.Felsite–Rhyolite.This is durableand makes a good aggregate for basecourses. It is not suitable for concreteaggregate.Gabbro-Diorite. Gabbro and dioriteboth have good strength and durability.The mineral crystals of both rocks aredeeply intermeshed, making them very toughand excellent for construction aggregate.Basalt.The dense variety of basalt,when crushed, is excellent for use as abase course. It is very strong and durable.Sandstone.Few sedimentary rocks aredesirable for construction due to theirvariable physical properties; however,sandstone is generally durable. Because ofthe variable nature of the types of grainsand cement, each deposit must be evaluatedindividually.5-4
Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business