Self-Consolidating Lightweight Concrete Beams in a VDOT Structure
Presented By: Celik Ozydilirim
Affiliation: VDOT
Description: Lightweight concrete (LWC) has been used successfully in VDOT structures over the years. In addition to its lower density, LWC provides several beneficial characteristics, including a lower modulus of elasticity, a reduced coefficient of thermal expansion, and internal curing from water absorbed in lightweight aggregates. These properties contribute to more durable bridge structures. Self-consolidating concrete (SCC) further enhances performance by offering a highly workable mixture that can be placed in areas with congested reinforcement and intricate geometry without vibration, reducing large air voids and improving uniformity and permeability. VDOT has used lightweight SCC in beams, where the mixture has improved placement and overall workability. This presentation highlights a successful application of self-consolidating lightweight concrete in beams for a two-span VDOT structure built in 2012. Condition surveys indicate that these beams continue to perform well. These findings emphasize the value of lightweight SCC mixtures for long-span structures, areas with congested reinforcement, and projects where reduced dead load and improved durability are desired.
Challenges when using SCC in New Nuclear Construction
Presented By: Boris Haranki
Affiliation: Baker Concrete Construction, Inc.
Description: Self-consolidating concrete does not automatically produce defect-free surfaces in nuclear construction, even when the mixture proportioning meets the guidelines in ACI 237R. This case study presents challenges associated with the use of SCC in the construction of members serving a shielding function, the troubleshooting process, mix design adjustments, and pumpability trials.
Evaluation of Pumpability of Steel Fiber-reinforced Concrete for High-rise Building Applications
Presented By: Gustavo Parra-Montesinos
Affiliation: University of Wisconsin-Madison
Description: Steel fiber-reinforced concrete (SFRC) has been used in the past two decades in earthquake-resistant coupling beams of high-rise coupled wall systems as a means to simplify reinforcement detailing and construction of these members. Another potential use of SFRC in high-rise buildings that is currently being investigated at the University of Wisconsin-Madison is the lower portion of walls for which extensive reinforcement detailing in the wall boundaries is required for adequate deformation capacity. For SFRC to be applied in walls, however, the material needs to be pumpable, which could be a challenge when large fiber dosages are used. The pumpability of SFRC for potential use in earthquake-resistant walls was evaluated by pumping a self-consolidating SFRC mixture with a fiber dosage of 105 lbs/yd3 through a 400-ft horizontal line. The steel fibers were 2.4 in. long and 0.035 in. in diameter, while the pipe diameter in the horizontal line was 5 in. Spread measured on concrete samples right off the truck was slightly greater than 20 in. Inspection of the concrete after it went through the horizontal pipe circuit indicated an even distribution of fibers and high workability, with a spread value of approximately 15 in.
Self-compacting, Fast-strength-gaining, Slip-formed SFRC Tunnel Lining segments: Full Scale Testing Validated Materials and Structural Design
Presented By: Liberato Ferrara
Affiliation: Politecnico di Milano
Description: The progressive automation of the construction sector is gaining increasing importance, driven by the need to enhance productivity, foster innovation, and meet the evolving demands of contemporary society. Within this framework, the present study investigates and validates, through full-scale testing and numerical modelling, a slip-forming technique for the refurbishment of existing tunnels using a self-compacting “extrudable” steel fibre reinforced concrete (SFRC). This approach provides a novel and efficient solution for the maintenance of highway and railway infrastructures. Four full-scale tunnel lining mock-ups were produced using the aforesaid Extruded Tunnel Lining Regeneration (ETLR) technology and tested under two different loading combinations reproducing the main service action combinations. The experimental campaign was conducted at the ELSA Laboratory of the European Commission’s Joint Research Centre in Ispra, in the framework of the OPENLAB ETLR project (Research Infrastructure Access Agreement Nr. 3 6506-1 / 2021-1-RD-ELSA-ReactionWall). The tests provided an initial validation of the adopted design assumptions and confirmed the structural reliability of the proposed system. Prior to testing, a non-destructive investigation was performed on all the tested mock-ups to characterise the distribution and orientation of the steel fibres, as affected by the manufacturing process, and assess their influence on the structural performance as well as calibrate the pathway to include it in the design predictions, as also validated through a tailored numerical modeling.
Onboard Sensor and In-transit Management of SCC
Presented By: Nathan Tregger
Affiliation: Verifi LLC
Description: Self-consolidating concrete (SCC) delivers exceptional flowability and placement efficiency, but its performance is highly sensitive to subtle changes in mixture proportions, moisture variability, temperature, admixture dosing, and transport conditions. As a result, maintaining consistent quality from batching to placement remains a significant challenge for producers and contractors. Traditional quality control methods (e.g. slump flow, visual stability index, and J-ring tests) only capture material behavior at discrete points in time and cannot reflect the changes in slump flow that occur during transport. This gap often leads to variability in viscosity, segregation resistance, and overall workability, increasing the risk of defects, rejections, and costly adjustments onsite. A combination of onboard sensors and In-transit management offers a transformative solution by continuously measuring the slump flow inside the mixer drum during delivery. For SCC, which relies on a narrow performance window to achieve proper placement, this continuous feedback is particularly valuable. This presentation will discuss the use slump flow management in Australia.