MIX DESIGN OF STRUCTURAL SELF-COMPACTING CONCRETE USING VOID-BULK DENSITY METHOD

Self Compacting Concrete (SCC) was firstly developed in Japan in 1987. (Alternative: Pioneering works on Self Compacting Concrete eturns to 1980s in Japan) In recent years, much research has been conducted in other to achieve a reasonable and also suitable mix design method for controlling the compaction experiment and determination of the compliance particular trait of SCC. But, just a few researches have been done in to propose a mix design method that can have both of highly fluid state and good viscosity, simultaneously. SCC is a special kind of concrete that can flow through and fill the gaps of reinforcement and corners of molds without any need for vibration and compaction during the placement process. In this paper Void-Bulk Density mix design method for structural SCC is investigated. In this method, firstly, the relationship between the void volume (or density of combined aggregates) and coarse-to-total aggregate volume ratio is established by packing different amounts of coarse and fine aggregates following ASTM C 29/C 29M, using the void volume of the dry binary aggregate (fine and coarse), is determined. Then, based on the optimum ratio that results from minimum void of aggregate and minimum bulk density, mix design is accomplished and finally in order to increase the flowability of the concrete have been added, some excess paste via reducing ratio of volume aggregate in unit volume concrete. Obtained results of the experiments on fresh concrete (Slump flow, L-box, V-funnel) and hardened concrete (compressive strength, tensile strength, elastic moduli and durability) show that this method is appropriate for SCC. In this study nine different SCC mixtures having the volume of paste and the ratio between sand and gravel as variables were compared with eight different mixtures of conventionally vibrated concrete (CVC).