Q: What is diamond grinding?
Diamond grinding is a process in which closely spaced diamond blades are used to remove surface imperfections such as faults, warp and curl to restore the surface to a smooth, level pavement and improve ride quality. The longitudinal texture that is created provides improved friction and low noise characteristics. The process is normally performed in conjunction with other Concrete Pavement Restoration (CPR) techniques such as full and partial depth repairs, dowel bar retrofit (DBR) and joint sealing and should be part of any comprehensive pavement preservation program.
Q: What is dowel bar retrofit?
Dowel bar retrofit is the process of placing load transfer devices across the joints and/or cracks of existing pavements that exhibit poor load transfer, heavy faulting, pumping and/or corner breaks. The load transfer devices generally consist of round steel dowel bars placed parallel to the centerline in the theoretical wheel paths of the roadway.
Q: How do I know if my road is a candidate for concrete pavement restoration (CPR)?
Good candidates for CPR are generally concrete roadways with various degrees and types of distress but still show an adequate level of structural integrity. It is important to keep the pavement in good condition from the beginning of its life cycle and manage the rate of deterioration by applying the right repair treatments at the right time. Although managing the pavement deterioration from early in the life cycle is preferred, the repair methods available today do provide options to restore older pavements exhibiting more severe deterioration. Both the extent and severity of the distresses need to be analyzed to determine the best possible repair methods. For long term repairs, chemistry problems such as alkali silica reaction (ASR) should not be present in the pavement. The types of deterioration to look for include poor ride quality, cracked slabs, corner breaks, joint pumping, faulting at transverse or longitudinal joints and joint sealant failure.
Q: What is the life expectancy of concrete pavement restoration (CPR)?
In generic terms, there is no universal answer as to how long a particular treatment will last. However, based on the condition of specific pavement sections, applying the right CPR treatment at the right time in the pavement's life cycle has been proven to extend the life of the pavement 10 to 20 years and even longer in many cases. See Long Term Performance of DBR in Washington State, The Effectiveness of Diamond Grinding Concrete Pavements in California and The Longevity and Performance of Diamond Ground Pavements.
Q: What are the benefits of CPR over other repair techniques (i.e. asphalt overlays)?
With CPR, you are able to target and fix the specific areas of deterioration rather than having to apply treatment to the entire roadway. Leaving the surface as exposed concrete will provide immediate access to future deterioration rather than allowing it to worsen over time when concealed by an asphalt overlay.
CPR has been shown to reduce wet weather accident rates and save lives.
CPR maintains the light reflective nature of concrete by minimizing lighting requirements, especially in urban environments. Additionally, the light colored surface reduces the heat island effect associated with asphalt pavements.
Unlike an asphalt overlay, diamond grinding and CPR do not raise the pavement's surface elevation. Consequently, there is no loss of gutter capacity, no loss of clearance at overhead structures and no issues with exisiting guardrail height adjacent to the sections undergoing repair.
Typical rutting issues associated with asphalt pavements at intersections and heavily trafficked corriders are eliminated.
CPR techniques actually fix the problems associated with the pavement deterioration rather than just hiding them under an asphalt overlay, which allows a problem to worsen.
The state of Georgia has used CPR with grinding for more than 30 years and has found it to be 3 to 4 times more cost effective than a 6 inch asphalt overlay.
Q: What is full depth patch repair?
Full depth repair is the removal and replacement of full slab thickness sections of deteriorated pavement. Length can vary based on conditions present. A common minimum patch size is four to six feet long and a full lane width wide. This type of repair can be completed on both jointed and continuously reinforced concrete pavement. On jointed pavement, the transverse construction joints at the patch ends are typically doweled and/or tied to restore load transfer across the joints. Additionally, on longer patch sections, dowel bar assemblies are placed at intervals to coincide with the existing transverse joint pattern present. On continuously reinforced concrete, the reinforcing steel pattern of the existing pavement is removed and replaced with new steel within the repair section. The transverse repair boundries are first sawed and jackhammered to expose approximately two feet (typical) of the existing steel to
facilitate the tying of the new reinforcement bars to the steel pattern in the existing pavement.
Q: What is partial depth patch repair?
Partial depth patch repairs are utilized to repair pavement deterioration in the top 1/3 to 1/2 of the slab. The repairs are generally located at the joints but can be placed anywhere surface defects occur. Two methods are commonly employed. One uses vertical saw cuts at the patch perimeter prior to placing the patch mix and the other method involves milling out the deteriorated pavement sections and placing the patch mix within the removal area. In both cases, the repair sections are sandblasted clean prior to the concrete placement and any existing joints are reestablished for the full depth and length of the repair.
Q: What is joint/crack resealing?
Joint/crack resealing involves the removal of old sealant and debris, cleaning of the joint faces and the installation of new sealant material in the joints and cracks of concrete roadways. The primary purpose of this process is to minimize moisture infiltration and prevent the intrusion of incompressibles into the joint reservoir which can lead to further and more significant pavement damage. The most common materials used to reseal concrete pavement joints are silicone and rubberized asphalt (hot pour).
Q: What is slab stabilization/undersealing?
Slab stabilization/undersealing is the pressure insertion of flowable material, usually a cementatious grout or urethane material, into existing voids beneath a concrete slab. Typically, there is a specified hole pattern on each panel into which the material is pumped. The process provides both short and long term reductions in pavement deflections and is most effective on pavements with minimal structural damage.
Please direct any technical questions you may have regarding the benefits and/or applications of any of the various CPR techniques to the staff at the IGGA. We are here to assist you and doing so allows for the discussion of all aspects of these processes to determine the proper mix of repair techniques to rehabilitate and preserve your concrete pavement investment. You may contact the IGGA at 518.731.7450.