go here http://fophs.org/president-messsage/december-2013-fophs-newsletter-is-posted-and-a-message-from-our-president/ Difference between Manufactured Sand and Crusher Dust:
http://tonovconstruction.com/dsc06242/ Quarry plants vary significantly in their degree of sophistication, in the range and extent of plant process controls and in the degree to which quarry raw feed is controlled to the plant. In simpler plant configurations the quarry raw feed, even when the raw feed is selected on some basis of quality, is processed through two, three or four stages of crushing and shaping and then is separated into a variety of sized aggregates. Usually all aggregate sizes are plus 5 mm and the fines removed at minus 5 mm are stockpiled as crusher dust. More-sophisticated plants will have the capacity to recover and reblend sized aggregates into graded products such as road bases or graded concrete or filter aggregates. Some plants will have the capacity to add stabilising agents, precoating agents or measured water to mixes to meet specific market demands. In rare cases plants will have the capacity to produce multiple products of similar grading but with different rock quality dependent on the source of quarry raw feed.
Most plants however direct the crushed fines to a single dust stockpile. Provided plant settings are not altered to any great extent and the quarry rock types do not vary excessively, the crusher dusts will settle to a relatively consistent product. Variation in the sizing of the product will result from screen and crusher wear, resetting, and the occasional errors such as a broken screen or screen overflow. Product quality will vary dependent on the range and quantity of different rock types within the quarry. For most market requirements these variations are acceptable.
Most crusher dusts of the type described have been used as a blend component in the production of road bases, although some plants produce high quality road bases by crushing quality raw feed into a full crusher run product where the fines are not separated. In road bases, if the crusher dusts contain a quantity of weathered or altered fines that result
in low levels of plasticity, this is usually accepted as being advantageous to the performance of the road base. Similarly, crusher dusts have been used as fills under slabs, where their ability to retain form, assisted by low levels of plasticity, enhances their ability to be compacted and yet to be fine enough that the fill pad can be easily trenched for drainage and service lines, making them useful construction products.
From suitable sources, some crusher dusts are used as the fines component in asphaltic concretes. Provided that the dust does not contain mineralogy that is water susceptible, the angular character and rough surface texture of the crusher dusts improve