Yoon Suk Choi

A Study on the Optimum Material Mix Design for Vegetation Shotcrete Using Mineral Additive

In this paper, the material characteristics of field applied green slope soil for the development of vegetation shotcrete using mineral additive are evaluated. And, the effect of the moisture content of fertilizer on properties of the shotcrete soil using the mineral additives are investigated. From the results, it was found that when the compaction level increase, soil hardness and soil strength are increased. Moreover, after a certain level of consolidation is proceeded, soil hardness and soil strength are not affected by ages. However, in order to ensure slope stability, the cohesion of the field applied soil should be improved. When the mineral additive is mixed as a green shotcrete soil materials, it could be attributed to the increment of adhesion between green slope soil and slope face. And, when the moisture content of fertilizer increases, the soil hardness and soil strength is decreased. The moisture content of fertilizer increases, shrinkage decrease at early ages, however, shrinkage increased with ages. The optimum moisture content of fertilizer was about 60% from the view point of shrinkage and soil hardness of green shotcrete soil.

Comparison on Characteristics of Concrete Autogenous Shrinkage according to Strength Level, Development Rate and Curing Condition

In this study, autogenous shrinkage strain and prediction models of concrete specimens were compared with strength level and development rate. Also, concrete autogeneous shrinkage under various curing conditions was investigated. The results showed that autogeneous shrinkage increased as concrete strength increased. However, when the concrete strength was almost identical, the initial autogeneous shrinkage of OPC was larger than BFS, but the final autogeneous shrinkage of BFS was larger than OPC. Early wet curing reduced autogeneous shrinkage strain. Especially, when the early wet curing was applied for more than 24 hours, final autogeneous shrinkage was significantly reduced. The results showed that the existing EC2 models do not reflect concrete properties properly. Therefore, the revised model was proposed to better predict autogeneous shrinkage.In this study, autogenous shrinkage strain and prediction models of concrete specimens were compared with strength level and development rate. Also, concrete autogeneous shrinkage under various curing conditions was investigated. The results showed that autogeneous shrinkage increased as concrete strength increased. However, when the concrete strength was almost identical, the initial autogeneous shrinkage of OPC was larger than BFS, but the final autogeneous shrinkage of BFS was larger than OPC. Early wet curing reduced autogeneous shrinkage strain. Especially, when the early wet curing was applied for more than 24 hours, final autogeneous shrinkage was significantly reduced. The results showed that the existing EC2 models do not reflect concrete properties properly. Therefore, the revised model was proposed to better predict autogeneous shrinkage.