The ACI Foundation is committed to progress in the industry by funding needed concrete research and will fund 10 research projects in 2022 in the “ACI Foundation Research Awards for 2022“. A. Dean, ISCP, broke out 5 of the 10 research projects that pertain to concrete pavements (green header w/blue title) and included the description of the research from the ACI awards page (see link below). Summaries of each of those 5 projects are included. Please see the list of the remaining 5 research projects (at the bottom … pertain more to structural concrete), as well as the link to the awards page. Sources: American Concrete Institute Foundation, Farmington Hills, Mich.; CP staff
PCMs & Heat Absorbing:
1—Phase change material (PCM) based heat-absorbing lightweight surface covering to prevent excessive temperature rise in concrete pavements/bridge decks during curing in hot weather—could be beneficial to reduce the risk of early-age thermal cracking and later-age distress without compromising the mechanical properties and durability of concrete
• “Development of a Phase Change Material-Based Heat-Absorbing Surface Covering for Concrete Pavements/Bridge Decks” Jung Heum Yeon, Texas State University
Most state DOTs regulate the maximum concrete temperature for concrete paving operations. Such temperature restrictions significantly limit the construction time windows for concrete pavements/bridge decks. The restriction is rooted in a perceived notion that higher concrete setting temperature results in a higher early-age cracking risk, wider crack width, and more distress in concrete pavements/bridge desks in the long run.
Various material- and design-related methods have been proposed to control early-age cracking during paving in hot weather, including low heat cement, supplementary cementitious materials (SCMs), retarder, precooling of ingredients, and nighttime concrete placement. Such methods, however, may adversely affect the mechanical and durability performance of concrete and construction cost-effectiveness, and they may also cause construction delays.
This research aims to develop a phase change material (PCM) based heat-absorbing lightweight surface covering to prevent excessive temperature rise in concrete pavements/bridge decks during curing in hot weather, which could be beneficial to reduce the risk of early-age thermal cracking and later-age distress without compromising the mechanical properties and durability of concrete. A phase change material (PCM) is a functional substance with a high heat of fusion that absorbs and releases heat during its phase transformation whilst its temperature remains constant. With this latent heat function, a material system with PCMs exhibits enhanced thermal inertia, thereby effectively regulating the amplitude of thermal cycling and preventing abrupt temperature changes.
Ultra-high performance concrete:
2—Ultra-High Performance Concrete (UHPC) is being applied in several structural systems and expanding into new applications in North America:
• “Shear Behavior of UHPC Considering Axial Load Effects”
Under Principal Investigator: Dimitrios Kalliontzis, University of Houston
As Ultra-High Performance Concrete (UHPC) is being applied in several structural systems and expanding into new applications in North America—a variety of items for bridges, like girders, waffle panels, thin bonded overlays, joint fills, and more; precasts, etc. Understanding its shear behavior is critical to avoid failures that could be induced by diagonal cracks. Shear-dominated mechanisms in a number of applications can be affected by the tension and compression fields within the UHPC members. Assessing the vulnerability of UHPC members to combined shear and axial loads is important for the development of structural design guidance and key to UHPC’s wider acceptance in practice.
This project will utilize the unique capabilities of the Universal Panel Tester at the University of Houston with the objective to understand the shear behavior of UHPC members under axial load effects and assist in the development of UHPC shear design equations. The Universal Panel Tester enables testing under any configuration of loading, including the proposed combination of shear and axial loads of this research. To determine a broader range of design variables, the experimental results will be supplemented with parametric computational studies.
This research is expected to produce results that will facilitate the ongoing effort by ACI Subcommittee 239-C to develop a UHPC structural design guide. This ACI document will include design equations for beam shear. However, there is a lack of experimental data associating the shear capacity of UHPC with axial load effects. This research will assist in addressing this issue toward a shear model for UHPC members.
According to the website “UHPC Solutions”, UHPC is a new class of concrete that has been developed in recent decades for its exceptional properties of strength and durability. This high performance concrete can be utilized in structural rehabilitation and accelerated bridge construction in addition to several other applications. UHPC was first used by the U.S. Army Corps of Engineers in the late 1980’s and became available in the US in 2000. The commercial availability of UHPC allowed the Federal Highway Administration (FHWA) to start investigation in order to use UHPC for highway infrastructure. The FHWA investigations led to additional research from universities and demonstration projects. The result was a body of publications on UHPC and a long list of “bridge applications” including: • Prestressed girders • Precast waffle panels for bridge decks • Field-cast closure pours for prefabricated bridge elements (Joint-Fills) • Precast concrete piles • Seismic retrofits of bridges • Thin bonded overlays of bridge decks • Security and blast mitigation applications… 12 other countries have used UHPCs. UHPC is a material that has a projected 100-year life span with exceptional strength, durability, flexibility and longevity…To read on to learn more about the history of UHPC, its composition and applications, please go to the UHPC Solutions website: www.uhpcsolutions.com/blog/what-is-ultra-high-performing-concrete
Fly Ash Benefits & Natural/Alternative SCMs:
3—Fly ash provides significant benefits to concrete and questions on viability of using corn, soy, and hemp biomass to create low-cost alternative SCMs capable of supplementing existing SCM availability:
• “Alternative Supplementary Cementitious Materials from Local Agricultural Products”
Lisa Burris, Ohio State University
As a result of changes in power generation and emissions technologies in recent years, the supply of fly ash has been reduced to less than demand in many markets. Fly ash provides significant benefits to concrete including:
• reduction in carbon
• reduction of energy footprint
• increased durability
• cost reductions
Development of pozzolanic materials to supplement fly ash supply that can produce similar concrete properties are necessary in order to continue to produce sustainable, durable, and cost-effective concrete infrastructure.
The U.S. is the world’s largest producer of corn and second-largest producer of soybeans. Previous work has shown that agricultural biomass ashes produced from corn stover can be utilized to create alternative supplementary cementitious materials (SCMs), thus ash created from agricultural residue may provide a readily available supplement to fly ash. However, many gaps in understanding remain regarding the use of biomass ash in concrete. Better understanding of the changes occurring in agricultural products during processing, and the links between composition and performance, processes and product selection must be optimized to provide materials capable of producing high quality concrete.
The key objective of this research is to address remaining questions prohibiting assessment of the viability of using corn, soy, and hemp biomass to create low-cost alternative SCMs capable of supplementing existing SCM availability. Results from this study will determine the procedures required to obtain effective SCM products from common Midwest U.S. agricultural residue materials and will compare performance of cementitious mixtures containing biomass ash, blends of ashes, and industrially produced biomass ash to performance in fly ash-cement concrete. Results will also determine the ability of biomass SCMs to supplement supplies of traditional SCMs in concrete, guide usage of biomass in concrete regarding OPC replacement rates and expected properties and changes in admixture requirements. The results will also help determine if existing standards, such as ASTM C618, for quality control of biomass ash materials, and recommended uses of biomass materials by state DOTs are suitable. Research will add to the discussions of biomass as a pozzolan in documents such as ACI 232.1, Report on the Use of Raw or Processed Natural Pozzolans in Concrete, or allow a new report specifically focused on use of biomass ash materials in concrete to be created.
Hybrid Fiber System for Concrete Overlays
4—This research will investigate the feasibility of using a hybrid fiber system for concrete overlay applications.
• “Multiscale Reinforcement of Hybrid Steel Fiber Reinforced Concrete”
Xijun Shi, Texas State University
With the rapid development of the tire recycling industry, waste tire processors in the US have employed better processing technology to extract recycled steel fibers (RSF) with good quality. This technical enhancement along with a growing level of awareness of sustainability warrants the potential utilization of the RSF to reinforce concrete for thin concrete overlays.
This research will investigate the feasibility of using a hybrid fiber system for concrete overlay applications. The amount of the RSF extracted from scrap tires can account for 15% of the total weight of the tire waste. Unfortunately, the RSF has conventionally been treated as ready-to-melt steel, which is a less economical and environmentally friendly application in comparison to direct reuse. The increased understanding of the material behavior of the RSF based FRC mixtures and the sustainability implication gained from this project will greatly advance knowledge in this field and create thrust into new markets.
Research results, conclusions, and recommendations on the use of RSF in reinforced concrete overlays will be published and widely disseminated across the U.S. Results will also be submitted to ACI Committee 555, Concrete with Recycled Materials, for consideration of inclusion in a new ACI document that is focused on the use of RSF in concrete. We will also work with ACI Committee 544, Fiber Reinforced Concrete, to include the results in committee documents.
Consolidation Procedure to make specimens & perform fresh concrete tests:
5—The significance of this research is the generation of a better understanding of the relationship between consolidation, concrete composition and workability, transforming the consolidation process into a 21st century technique, adjusted for current and future concrete mixtures.
• “How Much Consolidation Energy is Really Required to Create Concrete Specimens?”
Dimitri Feys, Missouri University of Science and Technology
The consolidation procedure to make specimens and to perform tests on fresh concrete is over a century old. However, concrete technology has evolved tremendously over the last century, and it can be questioned whether the standard procedure is providing adequate consolidation energy for different concrete types. The objective of this research is to adjust the current procedures to consolidate concrete, listed in ASTM C31, C138, C173, C231 and others, based on mix design and fresh concrete properties. The effect of various consolidation efforts will be characterized through hardened concrete density and strength to detect entrapped air, as well as penetration for fresh concrete stability identification.
The significance of this research is the generation of a better understanding of the relationship between consolidation, concrete composition and workability, transforming the consolidation process into a 21st century technique, adjusted for current and future concrete mixtures. The research results on creating specimens and performing fresh concrete tests can be extrapolated beyond this project to concrete placement procedures which should reduce variability in concrete quality, allow for less restrictive requirements on concrete workability, while enhancing the implementation of more diverse concrete types. Understanding the consolidation – composition – workability interaction will allow for machine learning and automation in consolidation processes. That data can be added to slip-forming processes or 3D printing technology or deliver prediction tools for in-situ concrete properties, dependent on the consolidation effort and the concrete mixture.
After the research results are available, the advisory team which includes members of ACI 309, Consolidation and ACI 238, Workability, will engage in drafting a joint Technote for rapid dissemination of the results. The Technote and other research publications can also be used to update ACI Committee 309 documents, as well as sections pertaining to entrapped air content, consolidation and segregation in ACI Committee 238 documents. The team also hopes there will be industry support to propose fresh concrete classifications with ideal consolidation parameters to ASTM C-09 suggesting the adoption of ASTM C31 and other standards for fresh concrete tests using similar consolidation techniques.
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Remaining 2022 projects and investigators:
• “Damage Classification of Reinforced Concrete Structures for Fire: Rebar Temperature”
Negar Elhami-Khorasani, University of Buffalo
• “Maximum Reinforcing Ratio for Reinforced UHPC Beams: Towards Slender Elements”
Principal Investigator: Yi Shao, University of California-Berkeley:
• “Evaluation of Early-Strength Development in Tension-Driven High Strength Concrete Formulations”
Matthew Gombeda, Illinois Institute of Technology
• “Fatigue Behavior of FRP Bars Embedded in Concrete”
Christian Carloni, Case Western Reserve University
• “Reliable Measurement and Speciation of Sulfur in Concrete Aggregates” April Synder, RJ Lee Group
For additional information about each of 2022’s awarded projects, including funding partners, research team, ACI Committee involvement, and project details, please go to: https://www.acifoundation.org/research/researchprojects.aspx
For the Concrete Products article, please go to: https://concreteproducts.com/index.php/2022/05/16/aci-foundation-funds-uhpc-scm-concrete-specimen-research/