Optimization of Rheological Properties of Self-Consolidating Concrete by Means of Numerical Simulations, to Avoid Formwork Filling Problems in Presence of Reinforcement Bars

Self-Consolidating Concrete (SCC) is a relatively new type of concrete which does not require any energy for consolidation. Consequently, the hardened properties of the cast structural element are largely influenced by the flow pattern of SCC in the formwork. Several examples are available in literature showing the existence of dead-zones, dynamic segregation induced by high shear rates, filling of formworks as a function of the concrete yield stress, lower mechanical properties due to multi-layer casting, etc. All these examples were predicted by means of numerical, single fluid simulations, in which the concrete is assumed to be a fluid without particles. However, numerical simulations that take into consideration the influence of reinforcement bars on local patterns in SCC flow have not been reported extensively. Preliminary simulations have shown that a vertical bar creates additional zones with very low and very high shear rates, compared to the flow in non-reinforced elements. In this project, the influence of reinforcement on the flow of SCC in a vertical wall is studied. Different structural parameters, such as the formwork width, reinforcement bar diameter, concrete cover (distance between rebar and wall) and the distance between the rebars (to investigate group effects) will be considered in the investigation, in combination with the flow rate. The objective of the project is to identify, for each situation, minimum and maximum limits for the rheological properties (yield stress and plastic viscosity) to obtain a good formwork filling. In other words, the rheological properties will be varied for each formwork and reinforcement condition to identify any dead zones, in which the concrete is at rest, or any zones with very high shear rates, which might cause segregation of the concrete. In the dead zone, entrapped air bubbles are less likely to evacuate, reducing the mechanical properties of the concrete and potentially the bond between the concrete and the rebars. Coarse aggregates might migrate away from the zone with high shear rate, increasing the concentration of coarse aggregates in other zones, potentially leading to blocking further downstream the formwork.

Language

  • English

Project

  • Status: Completed
  • Funding: $16052.00
  • Contract Numbers:

    DTRT06-G-0014

    00042528

  • Sponsor Organizations:

    Research and Innovative Technology Administration

    University Transportation Centers Program
    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590

    Missouri University of Science and Technology, Rolla

    328 Butler-Carlton Hall
    1401 N. Pine Street
    Rolla, MO  United States  65401
  • Principal Investigators:

    Feys, Dimitri

  • Start Date: 20130515
  • Expected Completion Date: 0
  • Actual Completion Date: 20131231
  • Source Data: RiP Project 34930

Subject/Index Terms

Filing Info

  • Accession Number: 01517405
  • Record Type: Research project
  • Source Agency: Center for Infrastructure Engineering Studies
  • Contract Numbers: DTRT06-G-0014, 00042528
  • Files: UTC, RiP
  • Created Date: Mar 7 2014 1:01AM