Causes of Longitudinal Cracks on Newly Rehabilitated Jointed Concrete Pavements

This paper documents the analyses of the underlying causes for longitudinal cracks (LCs) on newly rehabilitated jointed concrete pavement (JCP) on the basis of the field investigations on two projects of rehabbed JCPs in Guangdong, China, as well as a series of tests. Investigation of Qinglian Highway focused on performance of four strategies used to rehabilitate the old Qinglian Road, while performance of three types of separation layer (SL) applied in the rehabbed JCP was the focus of investigation on Jiaoling Project. Furthermore, several other common factors were investigated in both projects, including materials and construction quality during rehabilitation, overloaded truck traffic volume on rehabbed pavements, etc. The findings of the investigations indicated that subgrade replacement caused more LCs on the newly rehabbed JCP than rubblization and break-and-seat which had been used to rehab old QingLian Road because it seemed to have caused plastic deformation and nonuniform compaction of the replaced subgrade attributable to diversity of replacing materials, variances in moisture content of replacing materials, and some problems related to construction. The plastic deformation and nonuniform compaction, in turn, led to uneven settlement of the replaced subgrade and then voids underneath new surface slabs. Voids combined with overloaded truck traffic were attributed to most of LCs on Qinglian Highway. While in Jiaoling Project, SL of 3 cm soft asphalt concrete (AC) with penetration numbers 200–300 performed better in stopping cracking than SL of geotextile and no SL if the original slabs and subgrade were stable because AC could generate higher strain under loading, more efficiently reducing the modulus of elasticity at the interface between base and surface slab and counteracting stresses SL of AC effectively broke the bond between base and surface slab so as to decrease early age cracks. Meanwhile, in both projects, over 80% of cracks were observed on the southbound lanes in which over 80% of overloaded trucks were running, although both directions of each pavement section had been rehabbed with the same structure and same materials. Thus, heavy truck traffic has been one of the major factors causing distresses of highways in China.