The advantages of the bonded overlays are lower cost and fewer problems in matching adjacent facilities. In airport pavements of Japan, however, a bonded overlay has not been in popular, because some information indicates that complete bonding is not obtained, and that bond characteristics have not been revealed.
　The purposes of this research are to investigate the critical factors that affect bonding and to propose some effective means that ensure higher bonding. As a result, the following main conclusions have been obtained.
　1 The method of surface preparation by shot blasting achieves considerable bond strength.
　2 The shearing strength of bonding has been extraordinarily low, even through the bending strength and the tensile strength have been sufficient.
　3 The proposed new bonding technique which is to groove on the surface of existing concrete slabs has showed a good effeciency to improve the shearing strength of bonding.
　4 It has been found that the anxiety about cracking by drying shrinkage of overlay concrete slabs can been reduced by the addition of expanision agents into overlay concrete.