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Where faulting takes place due to the absence of dowel bars and inadequate subbase support in jointed concrete pavement (JCP), dowel bar retrofit (DBR) is used to improve load transfer efficiency (LTE) and to prevent further faulting of slabs at transverse joints. Even though DBR generally improves LTEs and overall performance of JCPs, not all DBR projects have been successful. Faulting reoccurred within 2 years after DBR treatment on US59 in Texas. An investigation from the cores taken in the project revealed excessive voids under a dowel bar due to poor consolidation of the grouting material. A laboratory investigation was performed to determine the most critical factors for adequate consolidation of grouting materials in DBR. Typical rapid-setting grout materials widely used in DBR were selected and full-scale specimens were made for evaluations. Four testing variables for consolidation performance were investigated: time of placement after mixing, vibration time, slot width, and maximum aggregate size. Maximum aggregate size and slot width were not critical factors for consolidation performance of grout. The most significant factor was vibration time. Twenty s of vibration is recommended. Placement time was also an important factor, with grout materials placed after initial set performing poorly. Delayed placement of grout materials without vibration led to the most voids under the dowel bars. [ABSTRACT FROM AUTHOR]

In Texas, many miles of plain jointed concrete pavement (JCP) were constructed without proper load transfer devices such as dowels. After a number of years of service, some JCP sections without dowels showed distresses in the form of faulting at transverse joints. Some of the sections were designed in accordance with the AASHTO 1986 Guide, which required 50–75 mm thicker slabs in exchange for not using dowels. This pavement design did not work, with faulting at transverse joints that cause poor ride. Dowel bar retrofit (DBR) was performed on four projects to restore the pavement condition. Overall, DBR restored load transfer efficiency and resulted in improvement of ride quality. Even where the subbase stiffness is 5–10 times less than the minimum value required for proper performance of JCPs, properly installed DBR effectively restored pavement condition with minimum faulting after decades of service. Therefore, it indicated that DBR is able to minimize the faulting even where there is poor base/subgrade support. This is significant in that there are no effective and practical methods to improve subbase conditions in existing concrete pavement, whereas DBR can restore pavement conditions at a reasonable cost. However, not all DBR projects were successful. In one DBR project, faulting in the range of 6.4–9.5 mm occurred after less than 2 years of treatment. Forensic investigation revealed voids under the dowel bars, which indicates poor consolidation of the grout material. Efforts are currently underway in TxDOT to improve specifications for grout materials and DBR construction. [ABSTRACT FROM AUTHOR]