Investigation of paver screed on compaction characteristics of mixture

In order to improve the compaction efficiency of asphalt paver and obtain high compacting effect, a forced vibration damped system composed of paving material and vibration screed equipped in asphalt paver was analyzed. The relationships among resonance region, the frequency ratio and damping ratio were obtained by investigating the interaction mechanism and dynamics between screed and paving material. Based on the resonance theory, a simulation model of mechanical-material system reflecting the relationships among paving material compactness, vibration parameters, system parameters were established to obtain variation curve of paving compactness-screed frequency. According to the analyses of the models for different paving materials, the best vibration frequency and effective frequency range were determined, and the simulation calculations and full-scale experiments about two typical mixtures including SMA-13 and AC-20 were used to verify the frequency characteristics of the paving compactness. The results show that for gap-graded mixture SMA-13, passing rate of 4.75 mm sieve is 24.3%, asphalt content (mass fraction, same in the following content) is 6.37%, and the best vibration frequency is about 30 Hz. For continuous gradation mixture AC-20, passing rate of 4.75 mm sieve is 40.3%, asphalt content is 4.31%, and the best vibration frequency is about 35 Hz. With the increase of asphalt content and proportion of coarse aggregate in mixtures, the best vibration frequencies reduce. The simulation calculation results and experiment results have the basically same change rule. When the excitation frequency is greater than 75% of the best vibration frequency, screed shows efficient compacting effect for the mixtures. The research results can provide the basis for efficient compaction for asphalt mixtures. © 2016, Editorial Department of China Journal of Highway and Transport. All right reserved.