Concrete pavement recycling is a relatively simple process that involves breaking, removing and crushing hardened concrete from an acceptable source to produce recycled concrete aggregate (RCA). The formal process of RCA production typically involves an initial evaluation of the existing source concrete; pavement preparation, which may include removal of an asphalt overlay; pavement breaking, removal and transport to a processing facility; removal of any embedded steel such as dowel bars, tie bars, reinforcing bar, or wire mesh; crushing and sizing operations similar to those used for virgin aggregate production; beneficiation to improve the quality of the RCA, if necessary; and stockpiling of the freshly produced RCA. If desired, the RCA also can be produced in-place in the field.
Quarry Process
The major steps in the production of recycled concrete aggregate (RCA) from concrete pavement are: evaluation of the source concrete; preparation of the slab; breaking and removing the concrete; removal of any embedded steel; crushing the concrete and sizing the RCA; beneficiation, if necessary; and stockpiling the RCA.
Beneficiation:
Beneficiation is the treatment of any raw material to improve its physical or chemical properties prior to further processing or use. This can be a necessary step in some aggregate processing operations to prevent the inadvertent inclusion of organic material, excessive dust, and other contaminants that would cause problems in the intended application of the aggregate. The degree of beneficiation required depends upon the condition and composition of the crushed concrete, as well as the intended use of the RCA.
Quarry Process
Crushing and Sizing
The same basic equipment used to process virgin aggregates also can be used to crush size and stockpile the RCA (ECCO 1999), although some equipment modifications may permit more efficient processing of most salvaged concrete pavements.
The three main types of crushers used in concrete recycling feature jaw, cone and impact designs, which differ in how they crush the concrete. While most concrete crushing plants are designed for high-production use by large contractors,mini concrete crushers" (capable of being towed behind a pick-up truck) also are available for small, local projects.
With appropriate adjustments, concrete crushing plants can be set up to produce almost any desired gradation, although there often is an excess of ne RCA produced.
Quarry Process
