Mon, March 30, 2020 4:00 PM - 6:00 PM, Grand G
Mixtures designated as self-consolidating concrete (SCC) may need a certain amount of consolidation to eliminate surface blemishes, to flow through congested areas, and to meet slump flow loss during construction. Care must be exercised in consolidating highly flowable mixtures such as semi SCC and SCC because they can lose stability. This session will address the consolidation needs of semi SCC and SCC and the effects of type and duration of vibration on the stability of these mixtures. There will be case studies and lessons learned. Researchers, engineers, contractors, and practitioners will benefit from the experience of the presenters.
(1) Discuss the effects of vibration on concrete with various consistencies including SCC;
(2) Explain when and how to apply vibration to SCC mixtures;
(3) Discuss vibration of SCC for surface aesthetics;
(4) Discuss the consolidation of highly flowable fiber reinforced concretes (FRC).
This session has been AIA/ICC approved for 2 CEU/PDH credits.
The Impact of Rheology on Self-consolidation and SCC’s Response to Consolidation Efforts
Presented By: Joseph Daczko
Affiliation: BASF Corporation
Description: This presentation will provide insight into how the rheological properties of SCC impact the characteristic of “self-consolidation” and SCC’s resistance to vibration induced segregation. Data will be presented as well as practical tips on how to evaluate and classify SCC mixtures.
Optimal Balance Between Consolidating Ability and Green Strength of Semi-flowable Self-consolidating Concrete (SF SCC)
Presented By: Surendra Shah
Affiliation: Northwestern University
Description: This study investigates the optimal balance between consolidation properties and shape stability of semi-flowable, self-consolidating concrete used for slip-form paving application. Different types and amounts of supplementary cementitious materials, water reducers, and additives were used to modify flowability and maintain green strength of the concrete. The results indicate that flowability and consolidation ability of a stiff concrete mixture can be significantly improved by addition of fine materials without significantly impairing the shape stability of the fresh concrete. Use of fly ash replacement for cement can further increase concrete flowability but it also reduces concrete green strength. The optimal balance between consolidating ability and green strength can be achieved when fly ash is used together with clay additives or propylene fibers.
Consolidation of Test Samples Made with Fiber-reinforced Superworkable Concrete
Presented By: Kassimi Fodhil
Affiliation: University of Sherbrooke
Description: The use of fibers to enhance the performance of superworkable concrete can hinder workability necessitating further mechanical consolidation that can lead to segregation. This paper evaluates the effect of mechanical consolidation on segregation, surface quality, and mechanical properties of fiber-reinforced superworkable concrete (FR-SWC) in an effort to recommend a protocol that can be employed for the preparation of test samples of FR-SWC. Mixtures prepared using polypropylene and steel fibers incorporated at a volume of 0.5% were tested. With each fiber type, test parameters involved the incorporation or omission of viscosity-modifying admixture and addition of high-range water reducer to assure a slump flow of 450 mm (17.7 in.) or 550 mm (21.7 in.). Test cylinders were cast in one layer and underwent different degrees of mechanical consolidation using a 10 mm (0.39 in.) steel rod. Vibrating table was also used to induce high consolidation effort during 20 and 25 seconds. Image analysis was carried out on longitudinally saw-cut surfaces of the concrete cylinders. Test results indicate that rodding enabled the reduction of honeycombing but did not affect mechanical properties and segregation. The use of vibration consolidation enhanced mechanical properties and surface quality but led to considerable increase in segregation, unless the concrete is highly stable. Casting test samples in one lift and consolidating them with 20 strikes of rodding can provide adequate consolidation energy to enhance mechanical properties and surface properties without segregation.
Consolidation Free SCC: A Close Look at Some Ready Mixed Concrete Applications
Presented By: Caroline Talbot
Affiliation: Euclid Chemical
Description: When deciding to use self-consolidating concrete, the promise of a surface with very little bugholes without using vibrating devices to put the concrete in place is often an important factor of the decision. While there are other reasons that influence this decision like the heavy reinforcement, the access or configuration of the element to be concreted, most people think about the improvement of the surface appearance and no vibration. This aspect being therefore so important in the decision making, it is very disappointing when it is realized that some form of vibration might be needed at one point or another. This presentation will review different applications, method of placements, mix design and plastic properties versus the use of vibration and type of vibration. Since many factors and job site conditions can influence the decision to use internal or external vibration we will look at the different field situations and requirements and compare the need or not of using vibration.
Consolidation of SCC in Precast/Prestressed Concrete
Presented By: Terrence Harris
Affiliation: GCP Applied Technologies
Description: SCC is used in most precast and prestressed concrete plants in North America. Applications vary from architectural pieces, underground utilities, double tees and beams for bridges. In many of these applications some vibration is necessary to achieve the desired result. The type and method of vibration in these applications is extremely important.