A number of test sections were laid during summer 1988 in the county of Värmland, western Sweden, to test new methods of using sand in the upper layers of a road being strengthened. Measurements were performed during 1988 before and after strengthening, and also during spring and autumn 1989 and 1990 to compare test sections in terms of bearing capacity and rutting. During 1991, registrations of cracks have been made, but no measurements. The results show that even after two years of use and two spring thaws, no rutting or noticeable change in the cross-profile has occurred, either on any test section or on the control sections. Neither has any rutting been observed on inspections of the test stretches in September 1991, although there was a cracked area on test stretch number 9 with two layers of geotextiles. As anticipated, cracks have occurred in cement-stabilised layers and are principally longitudinal. Similar cracks have also occurred to a lesser extent on a test section stabilised with bitumen emulsion. The roadbase (nominally 200 mm thick) on these test sections consists wholly of stabilised sand. Bearing capacity measurement with deflectometer also indicate a reduction in strength on the cement-stabilised sections, although the layer stiffness remained relatively high during autumn 1990. On unstabilised sections with and without reinforcement, the changes are less evident, but the bearing capacity closely follows the season. The layer stiffness of the roadbase varies between 216 and 465 MPa for unstabilised sections and between 489 and 857 MPa for stabilised sections. On unstabilised sections, the roadbase consists of 100 mm roadbase gravel laid on 100 mm sand which has been reinforced or mixed with rock flour and a waste-product filler respectively. (A)
Samenvatting