EVALUATION OF UNDERSEALING OF UNDOWELED PLAIN JOINTED PCC PAVEMENTS IN SOUTH DAKOTA. EXECUTIVE SUMMARY

Pumping and faulting of undoweled Portland cement concrete (PCC) pavements has become a serious problem in South Dakota. Repair techniques to correct these distresses include diamond grinding, full/partial depth repairs, load transfer restoration, installation of edge drains, crack sealing, joint resealing, and slab stabilization (undersealing). Undersealing can be described as a method where a flowable mixture is pumped under the slab to fill the voids and restore support to the pavement. There is a disagreement within the South Dakota Department of Transportation (SDDOT) as to the use and effectiveness of undersealing as a rehabilitation technique. The objectives of the research were to describe the deterioration of load transfer and the development of faulting on undersealed and nonundersealed PCC pavements, to determine the effectiveness of undersealing, to determine when and where undersealing is appropriate, and to develop design, construction, and inspection guidelines for undersealing. The work included a review of the literature relevant to undersealing; a national survey of current highway undersealing practices for PCC pavements; and field evaluation of four projects which were undersealed in South Dakota in 1987, 1989, 1992, and 1993. Research results indicate that all undersealed pavement sections performed better than nonundersealed pavements. Lower faulting and corner deflections, and higher load transfer efficiency values were generally obtained for the undersealed pavements. Best performance was obtained immediately after grouting and performance generally degraded with time. Undersealing was effective in filling voids beneath the slabs as evidenced by the removal of two concrete panels. However, the cement-fly ash grout was generally cracked, suggesting that the grout is not durable for long-term performance. Undersealing, when done in conjunction with other rehabilitation techniques, can provide more than seven years of service life until additional rehabilitation or complete reconstruction is warranted.