Abstract
Chemical additives are very important in determining the behavioral characteristics of self-compacting concrete. For this reason, determining the building materials that make up the chemical structure of self-compacting concrete and the interactions of these materials is of great importance. The present study pertains to the effects of the use of different chemical admixtures (high-range water-reducing, i.e., superplasticizer, hydration accelerating, air-entraining, shrinkage reducing, and hydration heat reducing admixtures) on the fresh and hardened properties of self-compacting concrete. The influence of using a single one or a hybrid combination of the air-entraining, hydration-accelerating, heat-reducing, and shrinkage-reducing admixtures on the mechanical properties of fresh and hardened SCC was investigated through a set of tests. For this purpose, sixteen different SCC mixtures with different combinations of chemical additives were prepared and tested. The properties of fresh concrete were examined as well as the compressive and tensile strengths of the mixtures. SCC mixtures with shrinkage-reducing admixtures were evaluated in terms of shrinkage development. The effect of the use of admixtures was found to be more pronounced on the early-age concrete strength. The use of any type of additive in addition to the shrinkage-reducing admixture increased the speed of flow of fresh concrete.
Highlights
Modern civil engineering applications require the economy and speed of construction
For this reason, determining the building materials that make up the chemical structure of selfcompacting concrete and the interactions of these materials is of great importance
The cast-in-place concrete construction is more preferable in a great majority of the structural systems [1,2], including the buildings, since the monolithic nature of the beam-column connections in this type of construction increases the degree of static indeterminacy of the overall structure and enables the redistribution of forces in the case of any structural damage
Summary
Modern civil engineering applications require the economy and speed of construction. In certain types of concrete structures, for instance, bridges, the use of precast concrete members facilitate the construction by reducing the required labor and construction time. The seismic design provisions encourage the cast-in-place concrete construction due to the higher ductility provided by this type as compared to precast concrete and structural steel construction These higher degrees of ductility can only be achieved by proper amounts and detailing of reinforcement in the bearing members of the structural system and the beam-column joints. Prolonged vibration duration for proper placement of concrete in these congested regions impairs the detailing, i.e., bar spacing and concrete cover, of the reinforcement and can result in the segregation of fresh concrete. To overcome these difficulties, a new type of concrete, namely the Selfcompacting concrete (SCC), is gaining popularity among designers and engineers. Due to its highly-flowable nature, SCC is effective in achieving good compaction and eliminating the undesired bleeding and segregation of concrete
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