Abstract
The main problem in working with fresh concrete is the aggregate segregation during filling of formwork. The segregation is strongly related to W/C (Water/Cement) ratio. The fresh concrete is usually considered as a Non-Newtonian fluid since it is a mixture of aggregate, cement and water. The flow behavior of the fresh concrete to W/C ratio plays a crucial role in the quality of the high performance concretes by affecting the flow behavior of the fresh concrete. The aggregates in the fresh concrete usually cause segregation in the final product depending on the flow condition. In this study, the mechanism of segregation in such systems was theoretically investigated. The mould filling of fresh concrete was numerically investigated and aggregates were considered as Lagrangian particles and segregation was identified from trajectories of such particles. It was found that the aggregates were trapped at the dead zones leading to segregation in the system. The particle size and geometry of the mould was found to have significantly affect the segregation in the system.
Highlights
Fresh concrete is usually employed to obtain steel reinforced concrete structures
The flow behavior of the fresh concrete to W/C ratio plays a crucial role in the quality of the high performance concretes by affecting the flow behaviour of the fresh concrete
Bois et al [4], investigating segregation from another point of view, have put forwarded that when concerned with aggregate segregation in a structure; in vertical position, coarse aggregate is an important parameter of segregation and for different coarse aggregate-to-cement ratios (Ca/C), aggregate density significantly affects aggregate segregation in fresh concrete
Summary
Fresh concrete is usually employed to obtain steel reinforced concrete structures. The parameters such as reinforcing steel, mould shape etc. prevent homogenous distribution of aggregates in the structure. The excess water in the fresh concrete or higher fluidity is known to be main parameter, leading to segregation, sedimentation and instability of concrete. Khayat and Guizani [2] stated that sedimentation of fines, the segregation of aggregate, and upward migration of bleed water affected surface settlement. They stated that bleeding, segregation, and settlement could cause anisotropy in the direction of casting and weaken the interface between the aggregate and cement paste, increasing the tendency to develop micro cracking in such regions, resulting a direct implication on permeability, durability, and strength. Several factors influence the segregation of concrete, such as the grading of the mix, the method of handling of the concrete, and the manner by which the concrete is placed
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