How Concrete is Recycled
Products (aside from base course) are high quality aggregate, processed in steps with time and effort involved in crushing, pre-sizing, sorting, screening and contaminant elimination. The denominator is to start with clean, quality rubble in order to meet design criteria easily and ultimately yield a quality product that will go into end use.
Crushing and screening systems start with primary jaws, cones and/or large impactors taking rubble from 30 inches to 4 feet. A secondary cone or impactor may or may not need to be run, and then primary and secondary screens may or may not be used, depending upon the project, the equipment used and the final product desired. A scalping screen will remove dirt and foreign particles. A fine harp deck screen will remove fine material from coarse aggregate.
Further cleaning is necessary to ensure the recycled concrete product is free of dirt, clay, wood, plastic and organic materials. This is done by water floatation, hand picking, air separators, and electromagnetic separators.
Occasionally asphalt overlay or patch is found. A mixture of asphalt and concrete is not recommended but small patches are not detrimental.
The more care that is put into the quality, the better product you will receive. With sound quality control and screening you can produce material without having to wash it as with virgin aggregate which may be ladened with clay and silt.
Value Engineering Benefits:
1. Produce specification sized recycled aggregates at your location
2. Avoid haul-off costs and landfill disposal fees
3. Eliminate the expense of aggregate material imports and exports
4. Increase project efficiency and improve job cost - recycled concrete aggregates yield more volume by weight (up to 15%)
5. Minimize impact to community infrastructure by reducing import and export trucking
Most PopularTypes of crushers
a. Jaw Crushers - Jaws compress the concrete between a stationary and moveable plate. Concrete is reduced in size as it travels down the length of the wedge between the two plates. Jaws are used as primary crushers and typically produce a 4" to 8" minus product usually used as fill.
b. Impact Crushers - Impactors have a spinning rotor with bars or hammers that fling the concrete into a solid plate, several plates, or rods. Impactors can be used as primary, secondary, and even tertiary crushers and produce a product typically 2" minus used as base material in some parts of the country.
c. Cone Crushers - Cones are also compression type machines with the concrete being compressed between two cone shaped plates. Concrete feed to a cone is typically 6" minus as they are used mostly as secondary crushers behind a Jaw or Impact Primary. Cones typically produce products of 1-1/2" minus.
All of the above crusher types are available in Portable, Mobile, and Stationary configurations
