Pulverization / Full Depth Reclamation / Stabilization
Did you know that asphalt is one of the most recycled products in the United States? There is no limit to the amount of times asphalt can be crushed into base materials or have a portion of it recycled into the new hot mix asphalt. Everyone talks about “going green” and limiting greenhouse gases but we often turn to outdated methods to address failing parking lots such as mill and fill, overlays, and traditional removal of the entire surface and replacement. These repair methods not only cost our budget but are not environmentally friendly.
The time to really “go green” is the present. Options exist in the asphalt industry to recycle your parking lot or roadway right on site. One of these options is pulverization where a large specialty machine arrives on site to crush and chew up the existing asphalt. Why is this better compared to traditional methods? The crushed material is compacted on site to create a sub base from the existing parking lot material. During pulverization a contractor has to remove only a fraction of the material compared to removing an entire parking lot in pieces to accommodate new hot mix asphalt. This saves on greenhouse gas emissions by reducing fuel consumption thanks to trucking out less material and trucking in less base material. Often catch basins and other secondary structures can be lifted so that when the lot is compacted and re-graded no material has to be hauled off site. This is a win-win situation as the cost savings are passed on to the customer and everyone involved has done their part to help the environment.
Poor sub base issues? The answer is simple. Full depth reclamation. Many times a roadway or parking lot that has failed under the age of 20-25 years is due to poor sub base soil conditions such as clay. The indicators of clay are heaving, sinking, deep rutting, and large separation of cracks. Traditionally when a situation arises such as this, the contractor has to break the bad news to the customer and inform he or she that soft areas will have to have the bad soil removed 12-18” deep and replaced with layers of stone prior to paving. This cost is above and beyond the original contract and it is not controlled. The cost can be an additional$3.00 a square foot or more. That equates to a 50,000 SF lot if in worse case scenario had to be completely undercut costing an additional $150,000.00 or more.
Full depth reclamation is a process completed simultaneously with pulverization to stabilize the sub base by having additional lime or concrete mixed in with the pulverized material along with water. Full depth reclamation (FDR) eliminates the need for undercutting the sub base and hauling out the spoils. This also eliminates the need for additional base material. The base becomes extremely hard and within hours to the point that a stake cannot be pounded into it. This hard base also decreases the chances of moisture from coming up from the parking lot below.
The stabilization process costs up to $1.50 per square foot and is a fixed cost therefore a 50,000 SF parking lot would An up front charge of $75,000.00 compared to a $150,000.00 change order in traditional repair methods. Also, the spoils do not have to be taken off site, no additional base material is required. If you have ever tried to get rid of clay, well no one wants it. Often a contractor must stock pile clay until later in the season until he can find someone willing to take it. This means trucking the spoils twice causing even more greenhouse gas emissions.