ON THE DEVELOPMENT OF ESTIMATING METHOD FOR RELATIVE DENSITY IN COMPACTING LAYER OF ROLLER COMPACTED CONCRETE

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This research project aims to develop the method for estimating the distribution of relative density in roller compacted concrete layer. Main experiments and computation in this research were carried out on the propagation of acceleration from surface vibrator to concrete, on the visualized experiment of concrete compaction and on the inverse analysis for identifying the mechanical constant of freshly mixed extremely dry concrete. And we developed a simulation program for estimating the distribution of relative density in roller compacting concrete layer. The results from this research are as follows.To develop a simulation program of surface compaction, the extremely dry concrete is represented by Voigt model, the compacting layer is represented by multi-layers of Voigt models and the base is represented by spring model. The structural model of computation is combined directly every element of a vibrator, compacting layer and supporting base. When a tensile stress is calculated in a model under computation, the node is disjoined between the vibrator and the top layer, then recalculated. This calculation technique was able to simulate the jumping behavior of a surface vibrator. The stiffer the supporting base is, the lower the relative density of bottom layer becomes by surface vibration. Also the difference in density between top and bottom layer becomes larger. The more elastic support makes the uniform density of layer.The compacting energy was calculated from the estimated acceleration in the structural model of computation. And the relative densities of every layer were derived from the compacting function of used concrete. The results of computation simulated the measured density with good accuracy.6. The developed simulation program of surface compaction is able to estimate the relative density of every layer under given vibrating and supporting condition, and to contribute to reduce the experiment at job site.