Lithium Treatment of an ASR-Affected Pavement on State Route 1 in Delaware

From 1998 through 2001, a section of portland cement concrete pavement on State Route1 in DE from I 95 to US Route 13 has been treated with topical applications of a lithium-based material in an effort to slow the progression of ongoing ASR-induced distress. Treatments were applied two times a year at a rate of 6 gal/1000ft 2 of pavement surface. The concrete thickness is a nominal 13 inches, with a very high alkali content cement (about 1.3% Na2Oe) and coarse aggregate now known to be reactive (a mixture of granodiorite and metadacite). Lithium penetration into the pavement was tested by taking cores with differing levels of distress, profile grinding the samples, and analyzing for lithium content. Penetrations of 20 to 30 mm were obtained in uncracked areas, and significant amounts of lithium were found at greater depths in areas with progressively greater distress. Impact echo readings were obtained annually with measurements indicating increased levels of distress in the control (untreated) sections compared with the treated sections. Furthermore, impact echo readings of extracted cores were compared with readings taken from the core locations prior to the removal of the cores. Significantly greater differences in these values for the control areas compared to the treated areas suggests lower stress levels in the treated areas. Finally, visual differences in control versus treated areas clearly show less distress in the treated areas.