Technology Showcase: Integrated Design of Chemical Admixture Systems for Ultradurable, Low CO2 Alternative Binder Chemistries via Machine Learning
Presented by Newell Washburn, Carnegie Mellon University; and Kimberly Kurtis, Georgia Institute of Technology
Alternative binder chemistries (ABCs), having extremely high durability, low embodied CO2, and good mechanical properties have been identified; among ABCs, the most commercially promising include limestone calcined clay (LC3) and calcium sulfoaluminate belite (CSAB) cements. Recent findings have demonstrated that further improvements to these systems can be realized through increased blending with low-impact minerals and through the addition of polymers. However, such ABC design optimization and their practical implementation at scale are limited by a critical need for novel chemical admixture systems to robustly meet workability, reactivity, and durability metrics. The enormous complexity of customizing such systems for disparate ABCs is daunting.
A recent award from the Advanced Research Projects Agency at the Department of Energy (ARPA-E) will fund the development of an artificial intelligence tool for the design of highly durable cementitious materials having significantly lower embodied energy as well as comparable characteristics and cost as portland cement. The research will be based on the extensive experience in the Kurtis group at Georgia Tech in the development of advanced infrastructure materials and machine learning tools developed at CMU by the Washburn and Póczos groups for chemical admixtures. This presentation will describe the work being undertaken under this ARPA-E award as well as the potential impact in the concrete industry.
Technology Showcase: Integrating Traditional Civil Engineering Practices with Artificial Intelligence: A Hybrid Approach to Enhancing our Understanding of Structural Behavior
Presented by Stephanie Paal, Texas A&M University
A fundamental understanding of the knowledge that can be gained from artificial intelligence when applied within the realm of civil engineering will have a translational impact on the analysis, design, maintenance, and construction of civil infrastructure. With models firmly grounded in real-world data, material and structural properties and behavior can be precisely predicted from each other without computationally expensive analytical or empirical evaluations. Moreover, by integrating artificial intelligence and physics-based models, transformative insights into the behavior of materials and structures and their relation to one another can be discovered, actuating next-generation modeling approaches, experimental methods, empirical relations, designs, and construction methods. In this presentation, a general framework for AI-based understanding of structural performance will be demonstrated and novel AI models aimed at predicting the seismic performance of reinforced concrete components, even when large amounts of data are not available will be introduced. A comprehensive comparison of the novel AI-based approaches with traditional empirical and modeling approaches popularly used in the field will also be presented.
Technology Showcase: Machine Learning - Prediction of Concrete Performance from Mixture Proportions
Presented by Gaurav N. Sant, University of California Los Angeles
The use of statistical and machine learning approaches to predict the compressive strength of concrete based on mixture proportions, on account of its industrial importance, has received significant attention. However, previous studies have been limited to small, laboratory-produced data sets. This study presents the first analysis of a large data set (> 10,000 observations) of measured compressive strengths from actual (job-site) mixtures and their corresponding actual mixture proportions. Predictive models are applied to examine relationships between the mixture design variables and strength, and to thereby develop an estimate of the (28-day) strength. Furthermore, to illustrate the value of such models beyond simply strength prediction, they are used to design optimal concrete mixtures that minimize cost and embodied CO2 impact while satisfying imposed target strengths. The outcomes have substantial implications on enhancing the sustainability and profitability of the concrete construction sector without affecting supply chains, manufacturing processes or construction codes.
Technology Showcase: Strengthening Bridges and Existing Concrete Structures Using Titanium
Presented by Jill Adkins, Perryman Company
Perryman Company has been pioneering the use of titanium in the infrastructure market since 2012. Older concrete bridges in the United States were not built for today’s standards. These bridges have inadequate steel reinforcement and were not designed for the current higher legal truck load demands. The options include replacement or rehabilitation when the bridges are rated deficient. Due to the lack of funding in the US, it is often more practical and cost effective to consider rehabilitation to extend the bridge life.
Titanium near surface mounts (NSM) have been shown to increase the shear and flexural strength of reinforced concrete in bridge girders. The original research was performed at Oregon State University with full size beam testing to prove this technology. In NSM strengthening, grooves are cut into the concrete at a shallow depth to avoid the internal steel. Then a bar or strip is placed in the groove and held in place with epoxy. With titanium, the technique is unique because it includes 90-degree anchorage hooks on both ends of the bar, resembling a staple. These anchorage hooks provide additional strength without being completely dependent upon the epoxy bond with the concrete. Titanium has high strength and good ductility along with complete corrosion resistance. It can survive in harsh environments with little or no concrete cover. In this application, titanium is actually more cost effective than the competing materials. This is a proven application and has been used on a number of bridges, with the state of Oregon leading the way. A design guide and an ASTM specification are available to assist design engineers.
Technology Showcase: Fiber-Reinforced Polymer Macrofibers Used in Precast Concrete
Presented by Alvin C. Ericson, an independent technical marketing consultant
A new type of FRP composite macrofiber is now available worldwide after being introduced in Europe less than 10 years ago. It is essentially a wire-size version of FRP rebar and can be made with any microfiber. This macrofiber bridges the current categories of synthetic and steel fibers since it is non-metallic, but with the structural performance of steel while also providing the function of crack control. It eliminates most or all secondary reinforcing such as WWR mesh and shear steel. In addition to being more durable, it enhances ductility and can reduce cross sections for lighter weight, less labor and a lower carbon footprint. Several applications from precast architectural and insulated wall panels to tunnel segments will be shown. Also, slab-on-grade projects and initial results from a recent test program on bridge decks at Utah State University will be presented.
Presentation: Engineering Analysis for FRP Composite Solutions Using ACI 440.1R & ACI 544.4R Design Guides by Robert Slade
Presented by Robert Slade, Eriksson Technologies, Inc.
Fiber reinforced concrete (FRC) has been used for crack control and durability enhancement for decades. Internationally, concrete design codes and building codes have begun formally recognizing the structural benefits of FRC. Recent advancements in fiber and concrete material properties have allowed FRC to be used more effectively. Similarly, FRP-rebar has been used in commercial and transportation applications for years and is widely accepted in applications where steel reinforcement is prone to corrosion. By combining the two materials into a “hybrid” design, the benefits of each material complement each other to provide a system with many possible applications. This design process will be reviewed, and areas where ACI document provisions hinder the adoption of this technology will also be discussed.
Panel Presentations: Use of Non-Metallic Reinforcement
Moderated by Randall W. Poston, Pivot Engineers, and presented by Antonio Nanni, University of Miami; Steven Nolan, Florida Department of Transportation; Doug Gremel, Owens Corning Infrastructure Solutions; Steve Sieracke, Black Swamp Steel, Inc.; Mohammed Al Mehthel, Saudi Aramco
The use of non-metallic reinforcement will be discussed from the viewpoints of private owner, public owner designer, contractor, manufacturer and researcher. Speakers will cover the state of research and development; activities by ACI, ASTM and AASHTO; and constructability, productivity and risk.
Technology Showcase: TyBot – An Autonomous Rebar Tying Robot
Presented by Stephen M. Muck, Brayman Construction Corporation
The construction industry is facing unprecedented labor shortages while the global demand is rapidly growing. At the same time, the next industrial revolution centered around robotics and artificial intelligence is accelerating in other markets. TyBot is leading this technology revolution for the construction industry by proving robots can reliably, safely, and competently work together with crews on-site using existing construction operations and practices. Tying rebar intersections continuously in rain or on the night-shift, TyBot represents a reliable and scalable solution to meet labor needs. TyBot provides a genuine return on investment through enhanced productivity, improved safety, increased profits, and reduced schedule risk.
Presentation: Value Proposition of GFRP Rebar in Bridge Decks
Presented by Doug Gremel, Owens Corning Infrastructure Solutions
The use of Fiberglass rebar or GFRP Rebar in bridge structures has moved beyond the research phase and into commercial adoption. Maturation of design codes and material standards means a more economical implementation as conservatism in initial standards are being relaxed. Core samples from bridge structures using GFRP Rebar with 20 to 25 year performance history show little or no degradation. The inherent light weight of the material means productivity and health and human safety benefits also bring cost savings to the job site. Improvements in material properties further push the economic implementation to a point where on an installed cost basis GFRP Rebar is competing on first cost with coated steel alternatives.
Presentation: Research Update & Code Changes for High Strength Steel Reinforcement
Presented by Gregory M. Zeisler, American Concrete Institute
High-strength reinforcing steel (steel with yield strengths greater than 60 ksi) was identified by the SDC as a technology that was critical to the industry due to potential benefits of high strength reinforcement to improve the cost efficiency and constructability of buildings. The ACI-318-14 Building Code limited the use of high-strength reinforcing steel to lateral ties for confinement and shear reinforcement. Incorporation of high strength reinforcement into the ACI 318 Building Code Requirements for Structural Concrete required extensive code changes and the research to support such changes.
The ACI Foundation via its Strategic Development and Concrete Research Councils has co-funded some of the research that provided data to overcome knowledge gaps and helped to develop code change proposals. This update will summarize the nature of the code change proposals, outline which proposals were adopted for the ACI 318-19 Code, and describe the benefits afforded to the industry because of adoption.
It will also address whether other high-strength reinforcement knowledge gaps still exist in the ACI 318-19, the importance of those and potential for the need for additional research.
Presentation: Research Update & Dissemination Efforts for Reduced Cracking
Presented by David Darwin, University of Kansas, Lawrence
Cracking has been a problem for as long as concrete has been used as a construction material. Cracks reduce durability, affect appearance, may represent a major structural problem, and are costly to repair. Volume change in concrete represents a major contributor to cracking and understanding how to control cracking induced by volume changes in plastic and harden concrete is critical to the overall industry. This study addresses the field implementation and evaluation of a wide range of crack-reduction technologies – supported by laboratory work. The research objective is to implement cost-effective combinations of materials and construction techniques to minimize cracking in highly crack-susceptible structures and compare the performance of structures constructed using these techniques with that of structures constructed without of crack-reducing technologies. The technologies include shrinkage-reducing and shrinkage compensating admixtures, fibers, mineral viscosity modifying admixtures, load transfer devices, and internal curing, and where possible, the latter combined with slag cement or slag cement and silica fume as partial replacements for portland cement. Originally planned to include 20 projects, the study now has 40 projects were underway, 27 dealing with new crack-reduction technologies and 13 serving as controls. The key findings will be summarized and plans for dissemination will be described.