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Excavation and Hauling

Extra-heavy-duty and extra-large buckets are typically used for the excavation and removal of the broken cement debris. A specialized type of bucket, the riddle bucket (sometimes referred to as a shaker bucket) is used to separate large objects, such as bricks, rocks, or broken chunks of cement, from finer materials, such as soil. Once a cement structure, slab, or pavement has been broken up, it is often mixed with large quantities of soil or other materials. By using the riddle bucket to excavate out only the larger pieces of cement debris, a contractor can greatly increase the efficiency of cement excavation and the subsequent recycling effort. Riddle buckets are designed with large open slots that allow soil to fall out during excavation. Heavy-duty rib-backed models are suitable for rock and cement excavation.

The trucks used to haul the cement debris from the excavation site are similarly rugged, large, and heavy-duty. With a loose density of about 2,400 pounds per cubic yard, the truck's ratio of maximum load (measured in tons) to its heaped capacity (measured in yards) must be at least 1.05 and preferably 1.5 tons to cubic yards. These trucks should be able to withstand the impacts of large pieces of cement. Articulated dump trucks are preferred for onsite hauling but are less suitable for road travel. Cement chunks falling out of the back of a poorly secured truck bed represent a serious traffic safety concern.

Crushing and Steel Removal

Once the large chunks have been excavated and hauled away from the digging site, they can be sent to a mobile crusher unit that makes little chunks out of large ones. These crushing machines don’t just handle cement; they also crush asphalt, bricks, and rocks. What they can’t accept are non-rigid materials that don’t easily break and could clog their intakes (trash, wood, organic wastes, paper, etc.). No attempt is made to remove rebar before the crushing operation; the steel goes into the crusher along with the cement and comes out freed from its now-shattered cement encasements. Magnets remove the now-loosened rebar for resale as scrap metal. The steel-free cement is further processed by screening operations that separate small chunks from larger ones. Large chunks caught by the screen are fed back into the crusher for another round, and they keep going back until they have been reduced to an acceptable size.

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