New Approaches to Architectural UHPC
Presented By: Larry Rowland
Affiliation: Ceentek North America
Description: Architectural UHPC is a sustainable and structural building material that is growing in popularity and availability. For over three decades architectural applications for this unique class of concrete have benefitted from the high tensile strength, durability and toughness of this innovative product provides. This presentation will review many of the standard architectural UHPC applications including facade panels, balconies, stairs, rain screens, and as components of curtain wall systems. It will also highlight lessons learned from the field in regard to finishes and installation to advance the state of the art and promote innovation.
The IOT of UHPC
Presented By: Vic Perry
Affiliation: ceEntek North America
Description: The Internet of Things (IoT) is the connection of things (i.e.: concrete infrastructure) to the internet for the purpose of monitoring the performance of the infrastructure (i.e.: bridges) in real time. The data collected in real time provides infrastructure builders or operators with an understanding on how the piece of infrastructure is performing in real-time and enables the ability to make smart decisions on the construction or maintenance of the infrastructure. In the past 20 years, approximately 300 bridges have been constructed or rehabilitated with Ultra-High-Performance Concrete (UHPC). It has been utilized in bridge construction across North America in various applications such as precast bridge elements, field cast connections, overlays, pier jacketing, repair, and seismic retrofit. Bridge owners are frequently faced with the need to replace structural elements of existing bridges and are asked to accelerate the works to minimize traffic impacts to the general public during construction. UHPC with its ultra-high strength, excellent bond development and durability offers a great solution for the use as overlays and field cast UHPC connections for precast concrete bridge elements. The use of this material technology permits the acceleration of construction and rehabilitation and provides longer lasting robust rehabilitations compared to other conventional methods. The synergies obtained from combining IoT and UHPC through the use of wireless sensors embedded into the UHPC during construction can connect the UHPC bridge projects with decision makers who can use this real-time data to decide when the UHPC has attained sufficient strength to open the bridge to construction or traffic loads, without the delays normally associated with conventional methods of determining strength. The presentation will show examples of UHPC Bridge projects (Overlays, Connections, others) completed using the Maturity Method, wireless Bluetooth Sensors through the IoT.
UHPC Overlay Installation Methods – Contractor Perspective
Presented By: Peter Seibert
Affiliation: UHPC Solutions
Description: UHPC overlays are an ideal solution for bridge owners to preserve, repair and improve bridge conditions cost effectively. Throughout the last couple of years, multiple UHPC overlays were installed to improve the service life and performance of deteriorating bridge structures across the US. These projects taught the North American UHPC industry many lessons on the proper mix preparation, material movement, curing, and finishing overlay surface.
This presentation will discuss several UHPC overlay projects and installation methods from a contractor’s perspective. Lessons learned for a successful UHPC overlay installation and the use of a Thin Lift UHPC Overlay paving machine capable of paving lanes in widths from 8‘(2.4 m) to 30‘(9.1 m) will be reviewed. Innovative Thin Lift UHPC Paving machines help bridge agencies to accelerate bridge deck repairs by shortening the total construction schedule, by minimizing traffic interruptions, and by reducing the overall project costs.
Several project overviews, surface preparation and innovative construction techniques of multiple successfully completed UHPC overlay projects across the USA will be described.
Effect of Thixotropic UHPC on Interfacial Properties as an Overlay
Presented By: Jiang Du
Affiliation: Stevens Institute of Technology
Description: Thixotropy is a time-dependent shear thinning property of the non-Newtonian fluid that behaves as the solid under the static condition and changes to the fluid by agitating or vibrating. This study evaluates the effect of Nanoclay (NC) and ambient temperatures on thixotropy of ultra-high-performance concrete (UHPC) made with 0.23 water-to-binder ratio. A new type of liquid well-dispersed attapulgite Nanoclay was first used in this study. The paste mixtures were proportioned with a fixed high-range water reducer (HRWR) content and varying NC content between 0 and 0.20%, by mass of binders. Besides, the ambient temperatures were varied to mimic the typical environmental temperature in practice (i.e., 10?, 25?, and 35?). Test results show that the thixotropy of UHPC pastes with various NC content between 0 and 0.20% were in the range of 0.091~3.147 Pa/min (10?), 3.327~72.604 Pa/min (25?), and 54.945~681.183 Pa/min (35?), respectively. On the other hands, higher thixotropy decreased the bonding strength between UHPC overlay and substrate concrete. This was related to the increased entrapped air and porosity on the interface. The use of vibration is demonstrated to effectively improve the bonding properties of thixotropic UHPC overlay. Higher vibration amplitude reduce the vibration time to achieve the optimal interfacial properties. Results show that, for NC-0.20% at 25?, the bonding strength was increased from 1.22 MPa to 1.63 MPa by 33.6% when 45s vibration under 1.59 mm amplitude or 60s vibration under 0.79 mm amplitude are applied, respectively.
Seismic Performance of Reinforced Concrete Columns Strengthened with Ultra-High-Performance Fibre-Reinforced Concrete
Presented By: Adel Al Ekkawi
Affiliation: University of Calgary
Description: Earthquakes resulted in the collapse and damage of most concrete structures due to the inability of their supporting RC columns to experience large displacements due to their limited ductility. Researchers attributed this limited ductility to the inadequate old code seismic provisions that some RC columns still possess till our recent days, even after updating such code requirements. Such provisions include insufficient transverse reinforcements and inadequate lap splice length, in which both causes were the primary reasons for making RC columns vulnerable to earthquakes. As a result, seismic strengthening of deficient RC columns gained more focus in the last two decades, where a lot of efforts were made in developing efficient strengthening systems to enhance the seismic performance of RC columns. Such enhancement provided the column with more ductility, higher lateral strength, and more efficient energy dissipation. Moreover, strengthening systems helped limit the damage level that RC columns usually sustain during and after earthquakes. Correspondingly, the presentation will include some research works related to the seismic strengthening of RC columns with UHPC material. Furthermore, the presentation will include a trace of works over decades that happened worldwide and their corresponding research results. This will identify the ability of the UHPC to enhance the seismic performance of RC columns due to its high tensile strength and strain hardening behaviour that is achieved by its fibre reinforcements such as steel fibres and nanofibers. Moreover, the presentation will briefly discuss the shortcomings of using UHPC in the seismic area and how those shortcomings can be solved. This will help identify potential research gaps that direct the future of research in strengthening and repairing deficient RC columns with UHPC.
Field Implementation of UHPC Beam End Repair in CT
Presented By: Alexandra Hain
Affiliation: University of Connecticut
Description: Corrosion at beam ends is a pressing challenge in the maintenance of aging steel bridges. To tackle this challenge, the Connecticut Department of Transportation has partnered with the University of Connecticut to develop a UHPC repair method that can restore the original bearing capacity while protecting the beam end from continued deterioration. The repair involves welding shear studs to the intact portions of the web and encasing the beam end with UHPC. This provides an alternate load path for bearing forces that bypasses the corroded regions of the beam. The structural viability of the repair has been extensively studied both experimentally and analytically. This presentation will cover the lessons learned from the field implementation of the repair and will show data collected from fully instrumented beam ends.
Sprayed UHPC for Structural Reinforcement or Protection
Presented By: Sebastien Bouteille
Description: A major step forward has been made by successfully spraying ultra-high-performance concrete in every orientation. Over the past four years, the innovative technique of sprayed UHPC has been developed and improved as a result of several recent projects. The characteristics typically obtained will be presented, as well as the methods used to justify the structures and the lessons learnt from 6 repair sites of corrugated steel culvert, which have suffered from corrosion without being excessively deformed. Broader fields of application will be discussed and prospects for development will be opened up. Aspects related to innovations, material and structural design; application potentials will thus be covered.