Characterization of cracks on ultra thin continuously reinforced concrete pavements

[摘要] ENGLISH ABSTRACT: The southbound screener lane of the Heidelberg Traffic Control Centre received structuralimprovements by means of an ultra thin continuously reinforced concrete pavement(UTCRCP) overlay. This experimental overlay forms part of the South African NationalRoads Agency Limited's innovative highway repair strategy on existing pavements that haveexceeded design life. The primary objective of this study was to characterize the UTCRCPoverlay with regard to crack spacing formation under accelerated pavement testing (APT).Characterization comprised of empirical modelling techniques, statistical analysis, nondestructive testing and software simulations. Pavement deflection responses wereempirically and linear elastically converted to input parameters. These parameters wereused in the mean crack spacing prediction model of the Mechanistic-Empirical PavementDesign Guide (M-E PDG). Observed cracking under APT was recorded and analyzed bymeans of descriptive statistics. The outcome of the M-E PDG's mean crack spacing and thestatistics of the observed cracking were evaluated against cncPave simulations.Initial shrinkage crack formations ranged from 500 mm to 900 mm, with a mean spacing of695 mm. Subsequent secondary cracking reduced the segments, delineated by initialcracking, to intervals consisting of 100 mm to 350 mm. A statistical analysis of the observedcracking indicated that traffic had little effect on the transverse crack spacing formation. Theobserved cracks yielded a mean spacing of 296 mm, compared to the 186 mm of the M-EPDG mean crack spacing calculation. cncPave simulations indicated that the expectedrange of cracking would fall between 237 mm and 350 mm with a probability of 50% thatcrack spacing would exceed 265 mm. The 50th percentile of the observed cracks resulted ina spacing of 233 mm. The APT project was limited to a single test section. No pavementfailures occurred during the APT project. A total of 2.8 million 80 kN load repetitions wereapplied to the UTCRCP. However circular crack formations regarded as a punchoutdevelopment have formed on the UTCRCP test section.Circular cracks formed around weaknesses in the pavement system. The prediction of thesepunchout formations incorporates the mean crack spacing result. Occurrence of mean crackspacing forms part of a crack spacing distribution defined by a range. Therefore designing apunchout prediction model for UTCRCP should include the characteristics and range of thecrack pattern and not merely the mean crack spacing value.Key Words: UTCRCP, APT, Mean Crack Spacing, Punchout, Descriptive Statistics,cncPave, M-E PDG, Transverse Cracks, Dense Liquid Foundation, Elastic Solid Foundation.

[发布机构] Stellenbosch University