ACI Foundation Research Projects

Durability of GFRP Bars Extracted from Bridges with 15 to 20 Years of Service Life

Structural Response and Buckling Behavior of Slender Ultra-High Performance Concrete (UHPC) Columns

Towards Comparable Environmental Product Declarations of Concrete: Insights from a Meta-Analysis and Probabilistic Comparative LCA Approach

A Collaborative Study for the Development of a Standard Critical Chloride Threshold Test Method

Impact of Retarder-Induced Roughness on Shear Friction Capacity using Conventional and High-Strength Reinforcement

Shear Strength of Precast, Prestressed Steel Fiber Reinforced Concrete Hollow-Core Slabs

Recommendations for Unified Durability Guidance

Literature Review of Concrete Durability & Service Life Requirements in Global Codes and Standards

Development and Splice Lengths for High-Strength Reinforcement, Volume 1: General Bar Development

Development and Splice Lengths for High-Strength Reinforcement, Volume 2: Drift Capacity of Structural Walls with Lap Splices

Reinforced Concrete Coupling Beams with High-Strength Steel Bars

Acceptable Elongations and Low-Cycle Fatigue Performance for High-Strength Reinforcing Bars

Evaluating the Performance and Feasibility of Using Recovered Fly Ash and Fluidized Bed Combustion (FBC) Fly Ash as Concrete Pozzolan

Role of Microbial Induced Calcium Carbonate Precipitation on Corrosion Prevention

Guideline Development for Use of Recycled Concrete Aggregates in New Concrete

Prestandard for Performance-Based Wind Design

Low-Cycle Fatigue Effects on the Seismic Performance of Concrete Frame and Wall Systems with High Strength Reinforcing Steel

Ductile Reinforced Concrete Coupled Walls: FEMA P695 Study

Guidelines for Performance Based Seismic Design of Tall Buildings

Evaluation of Chloride Limits for Reinforced Concrete Phase A

Guide to Formed Concrete Surfaces

Setting Bar-Bending Requirements for High-Strength Steel Bars

High-Strength Steel Bars In Earthquake-Resistant T-Shaped Concrete Walls

Sustainable Concrete without Chloride Limits

Proposed Specification for Deformed Steel Bars with Controlled Ductile Properties for Concrete Reinforcement

Part 1 Materials: Defining Structurally Acceptable Properties of High-Strength Steel Bars through Material and Column Testing

Part 2 Columns: Defining Structurally Acceptable Properties of High-Strength Steel Bars through Material and Column Testing

Seismic Performance Characterization of Beams with High-Strength Reinforcement

Interface Shear Transfer of Lightweight Aggregate Concretes with Different Lightweight Aggregates

Serviceablility Behavior of Reinforced Concrete Discontinuity Regions

Evaluation of Seismic Behavior of Coupling Beams with Various Types of Steel Fiber-Reinforced Concrete

Brief Historical Overview of Yield Strength Determination in ACI 318

Determination of Yield Strength for Nonprestressed Steel Reinforcement

Reexamination of Punching Shear Strength and Deformation Capacity Corner Slab-Column Connection

Evaluation of Seismic Performance Factors and Pedestal Shear Strength in Elevated Water Storage Tanks

Mitigation of Steel Reinforcement Via Bioactive Agents

Modeling Parameters for the Nonlinear Seismic Analysis of Reinforced Concrete Columns Retrofitted Using FRP or Steel Jacketing

Improved Procedures for the Design of Slender Structural Concrete Columns

Assessing the Impact of Green Concrete Mixtures on Building Construction

Lab and Field Data for: Assessing the Impact of Green Concrete Mixtures on Building Construction

Transverse Reinforcement Requirements in Flexural Hinges of Large Beams of Special Moment Resisting Frames Subjected to Cyclic Loading - "Big Beam" Project

Development of Anchorage System for FRP Strengthening Applications using Integrated FRP Composite Anchors

Drift Capacity of Slab-Column Connections Reinforced with Headed Shear Studs and Subjected to Combined Gravity Load and Biaxial Lateral Displacements

Crack control and leakage criteria for concrete liquid containing structures

A Study of Static and Dynamic Modulus of Elasticity of Concrete

CLT and AE Methods of In-Situ Load Testing

Formwork Pressures for Self Consolidating Concrete

Assessing the Deicer Salt Scaling Resistance of Concrete Containing Supplementary Cementing Material

BIM Strategic Plan

2022 Funded Research

The ACI Foundation is committed to progress in the industry by funding needed research and will fund 10 research projects this year. Summaries of each project are below.

Alternative Supplementary Cementitious Materials from Local Agricultural Products 

PI: 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 and energy footprint, increased durability, and often 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.

Damage Classification of Reinforced Concrete Structures for Fire: Rebar Temperature

PI: Negar Elhami-Khorasani, University at Buffalo 

Co-PI: Ravi Ranade, University at Buffalo

Co-PI: Anthony Tessari, University at Buffalo

Concrete structures typically behave well during a fire event and do not collapse when subjected to moderate fires. However, these structures experience damage and require repair after the fire to resume function. The available guidelines on damage assessment of concrete structures after a fire are limited, and the evaluation is performed mostly on an ad hoc basis. Post-fire damage and repair classifications in the current guidelines rely on visual inspection, non-destructive testing, and sampling of material for laboratory testing. The information gathered by these common approaches can be supplemented with advanced modeling and analysis. If information on the fuel type and fire scenario can be collected, the response of the structure, e.g., in terms of sectional temperatures, can be simulated. Temperature thresholds within concrete sections and reinforcement can then be related to the level of damage. 

Repair and replacement of reinforcement in a damaged reinforced concrete structure is generally more complex and takes longer when compared to restoring or replacing concrete alone. In addition to the loss of strength at high temperatures, existing studies confirm that the interfacial bond between reinforcement and concrete influences the response of reinforced concrete structures under fire. However, there is no repair guideline for incorporating temperature-induced degradation of bond between reinforcement and concrete.

This research will study and propose rebar temperature thresholds for damage classification of reinforced concrete structures exposed to fire and will consider the temperature effects on material properties as well as on the rebar-concrete bond. This research will also directly benefit the work of ACI/TMS Committee 216 – Fire Resistance and Fire Protection of Structures by providing data for code requirements for concrete and masonry buildings as well as reinforced concrete structures such as bridges and tunnels. Project outcomes will be relevant to post-fire damage assessment and be used as performance objectives for designing or evaluating reinforced concrete structures for resilience against fire.

Development of a Phase Change Material-Based Heat-Absorbing Surface Covering for Concrete Pavements/Bridge Decks 

PI: Jung Heum Yeon, Texas State University

Co-PI: Togay Ozbakkaloglu, 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.

Evaluation of Early-Strength Development in Tension-Driven High Strength Concrete Formulations

PI: Matthew Gombeda, Illinois Institute of Technologyy

Co-PI: Nishant Garg, University of Illinois at Urbana-Champaign

The main objective of this research is to develop and subsequently facilitate the implementation of a framework for evaluating the progression of high-early tensile strength in non-proprietary, tension-driven high strength concretes. Development of high-early tensile strength attributes, such as modulus of rupture (MOR) for flexural considerations, is of particular importance for prefabricated concrete components to facilitate accelerated turnover of casting beds – while optimizing the use of formwork and/or shoring for certain cast-in-place applications. In contrast to ongoing research focusing solely on ultra-high-performance concretes (UHPC), a major focus of this research will be to evaluate mix formulations strategically detailed to exhibit high-early tensile strengths (and corresponding tensile ductility) greater than those of conventional high strength concretes without necessarily attaining UHPC-level performance. 

This research and the expected research products (mix design/batching framework for such formulations, proof-of-concept structural testing, and development of appropriate design guidelines) will serve a significant, intermediate market for structural applications not requiring or not able to easily attain UHPC-level performance. Relationships between high-early tensile strength development and corresponding compressive strengths will be closely examined and assessed relative to current applicable design provisions in ACI 318-19. The research results will also facilitate future revisions of applicable ACI reports focusing on early age strength development, high-strength concrete performance, and precast concrete structures. 

Fatigue Behavior of FRP Bars Embedded in Concrete 

PI: Christian Carloni, Case Western Reserve University

The objectives of this research are to investigate the mechanism of bond of glass fiber-reinforced polymer (GFRP) bars and the behavior of GFRP bars under cyclic (fatigue) loading. The development length of GFRP bars has been addressed using results from the database available in 2006 on different bond tests. This research will consider different bonded lengths for pull-out and notched beam tests, which will allow a homogenous set of data to fully capture the bond mechanism and therefore provide valuable information regarding the development length. Understanding the response of GFRP bars embedded in concrete under cyclic loading is crucial for bridge applications.

The lack of research in the area of fatigue behavior of GFRP bars embedded in concrete has forced engineers to limit the stress in the bar to low levels with respect to the tensile strength. This project will help us understand if the current limits are conservative or adequate for design and will allow ACI Committee 440 to improve or adjust the current limit for fatigue as well as identify any additional investigation on this subject. This research will also provide an in-depth understanding of the effect of the bonded length on the bond behavior, and the use of notched beam tests will provide valuable information on the crack opening under service loads.

How Much Consolidation Energy is Really Required to Create Concrete Specimens? 

PI: Dimitri Feys, Curators of the University of Missouri on behalf of Missouri University of Science and Technology

Co-PI: Kyle Riding, University of Florida

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. 

Maximum Reinforcing Ratio for Reinforced UHPC Beams: Towards Slender Elements 

PI: Yi Shao, University of California, Berkeley 

Co-PI: Claudia Ostertag, University of California, Berkeley 

This project will investigate the flexural and shear behavior of highly-reinforced slender UHPC beams and practical design guidance through full scale testing. Preliminary finite element simulation results show that compared to conventional concrete beams, highly-reinforced UHPC beams can reduce the section size, material usage and self-weight by over 50% while showing higher stiffness, strength, and ductility. This reduction in material usage can reduce the embodied carbon of concrete beams by over 23%, which improves the sustainability of concrete structure. The reduced self-weight will also (1) lower the deadload on beams themselves as well as columns and foundations, (2) extend the economic span of building frames and bridges, (3) reduce the seismic weight and thus improve the disaster resistance of concrete infrastructure, and (4) benefit the transportation and erection of prefabricated concrete members.

The research directly supports ACI Committee 239-0C, Structural Design on UHPC, ongoing efforts to develop UHPC structural design guidance. The work will also fulfill committee’s need to conduct blind prediction tests on full-scale UHPC beam tests in order to select appropriate UHPC material models and prediction models for both reinforced UHPC flexural and shear strength.

Multiscale Reinforcement of Hybrid Steel Fiber Reinforced Concrete 

PI: Xijun Shi, Texas State University 

Co-PI: Zachary Grasley, Texas A&M 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. 

Reliable Measurement and Speciation of Sulfur in Concrete Aggregates

PI: April Synder, RJ Lee Group

Co-PI: Michael Deible, RJ Lee Group

Over the past decade, significant localized outbreaks of concrete degradation caused by oxidation of the iron sulfide mineral pyrrhotite in concrete aggregates have occurred in Connecticut, Massachusetts, and Quebec. Thousands of residential structures were affected leading to new regulatory requirements in Connecticut for testing concrete aggregates.

This project addresses a critical need for a standardized method to test for sulfur in concrete aggregates. This is the first step in evaluating aggregates for their potential to degrade concrete through oxidation of pyrrhotite and other iron sulfide minerals. This is currently not addressed by ASTM. Testing concrete aggregates and aggregate sources for sulfur concentrations of interest and the distribution presents considerable analytical challenges. 

This project will consider a range of preparation and analytical methods, including those found in Annex P of CSA A23.1/A23.2 as well as existing ASTM test methods for sulfur in coal and will establish precision and bias data for the most promising test method. The work is aligned with the goals of Committees 201, Durability of Concrete and 221, Aggregates. These committees will be provided with draft language regarding the developed test methods that can be incorporated into revisions of ACI 201.2R, Guide to Durable Concrete, and ACI 221R, Guide for Use of Normal Weight and Heavyweight Aggregates in Concrete. The research team will collaborate with others currently working on pyrrhotite issues to also create guidance when interpreting and using the results provided by the developed test method(s). 

Shear Behavior of Ultra-High Performance Concrete (UHPC) Considering Axial Load Effects

PI: 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, 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.

Purdue University research project

Casting prestessed slender columns at Purdue University for the in-progress project, Improved Procedures for the Design of Slender Structural Concrete Columns. Photo credit to Ryan Jenkins and Robert Frosch.

Major Funder: Precast/Prestressed Concrete Institute

Minor Co-funders: ACI Foundation, Portland Cement Association, and Concrete Reinforcing Steel Institute

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