BACKGROUND

Recent transportation industry studies have highlighted a growing uncertainty regarding the availability of Class F fly ash along with a trend towards incorporating alternative supplementary cementitious materials (SCMs) like raw or calcined natural pozzolans (e.g., calcined clay) and waste products (e.g., reclaimed/harvested coal ashes and ground ashes). Within the next 5 years, the industry is expected to face an urgent need for integrating these alternatives to produce sustainable and durable concrete for diverse highway applications. However, current standards may not allow the use of alternative SCMs or may not adequately evaluate their efficacy in mitigating durability issues such as alkali-silica reactivity (ASR), corrosion, freeze-thaw cycles, and oxychloride formation. 

Research under NCHRP Project 10-104, “Recommendations for Revision of AASHTO M 295 Standard Specification to Include Marginal and Unconventional Source Coal Fly Ashes,” proposed a research plan to enhance the AASHTO M 295 (ASTM C 618) specifications and to develop effective tests for measuring SCM reactivity, thus addressing issues related to unburned carbon, and ensuring uniformity. By improving the acceptance criteria, these efforts will promote the efficient utilization of traditional and alternative SCMs. However, the effects of alternative SCMs on vital concrete properties like workability, durability, and performance have not been comprehensively studied.

To address these challenges, a comprehensive research approach is needed to help state departments of transportation (DOTs) and the transportation industry evaluate concrete mixtures containing alternative SCMs. 

OBJECTIVE

The objective of this research is to develop a framework and complementary tools for state DOTs and the transportation industry to evaluate concrete mixtures containing alternative SCMs that provide a high probability of meeting specified requirements in highway applications. At a minimum, the research shall (1) investigate alternative SCMs' impact on concrete properties, (2) identify critical properties based on intended applications, and (3) propose appropriate test methods.

Accomplishment of the project objective will require at least the following tasks.

TASKS

PHASE I – Planning and Data Collection

Task 1. Conduct a comprehensive literature review of relevant research related to the utilization of alternative SCMs for concrete in highway applications through durability-based performance evaluation. The review shall include:

• The availability of classes of SCMs to be used in highway applications within the United States;
• Published and unpublished research conducted through the NCHRP; Federal Highway Administration (FHWA); other national, international, state, and pooled-fund sponsored research; and
• Current state DOTs mix designs.

Task 2. Identify alternative SCMs available for testing and propose a comprehensive approach to characterize these materials including:

• Use of appropriate tests, such as within those of AASHTO M 295 / ASTM C 618 to determine bulk oxide composition, moisture content, fineness, soundness, density, and strength activity index (SAI); and
• Advanced characterizations (e.g., particle size distribution (PSD) by a laser particle size analyzer and phase identification and quantification by quantitative x-ray diffraction).

Task 3. Identify knowledge gaps of the results from Tasks 1 and 2 relative to the effects of alternative SCMs on concrete properties and limitations within current testing methods. These knowledge gaps should identify sections of the AASHTO Standard Specifications for Transportation Materials and Methods of Sampling and Testing (Materials Standards) that could be impacted by the results of the research findings.

Task 4. Propose a research plan to be executed in Phase II to achieve the research objective. At a minimum, the research plan shall include:

• Investigating the effects of alternative SCMs on key fresh properties, hardened and durability properties, and dimensional stability;
• Determining properties of a concrete mixture critical to its success based on intended application and exposure conditions;
• Assessing and recommending appropriate test methods for the defined properties, along with valid tolerances and pass/fail limits; and
• A preliminary sampling of concrete mixture designs utilizing alternative SCMs for testing.

Task 5. Develop a performance testing matrix based on the findings from Tasks 1 and 2 to be conducted in Phase II. At a minimum, the matrix shall include testing for:

• Fresh properties (e.g., workability, air content, setting time, and water demand);
• Strength properties (e.g., compressive strength, flexural strength, modulus of elasticity);
• Dimensional stability; and
• Durability properties (e.g., freeze/thaw durability, transport properties, alkali-silica reaction (ASR) mitigation, delayed ettringite formation (DEF), sulfate attack, chloride-induced corrosion of reinforcing steel, and joint deterioration due to formation of oxychloride).

Task 6. Prepare Interim Report No. 1 that documents Tasks 1 through 5 and provides an updated work plan for the remainder of the research. The updated work plan must describe the process and rationale for the work proposed for Phases II through IV.

PHASE II – Testing and Matrix Validation

Task 7. Execute the research plan according to the approved Interim Report No.1.

Task 8. Perform the testing proposed in Task 5 according to the approved Interim Report No.1 as it relates to:

• Task 8A – Fresh properties;
• Task 8B – Dimensional stability and strength properties; and
• Task 8C – Durability properties.

Task 9. Propose a preliminary outline for the framework and complementary tools (e.g., flowchart, decision tree, spreadsheet) based on the research findings from Phases I and II.

Task 10. Prepare Interim Report No. 2 that documents Tasks 7 through 9. The updated work plan must describe the work proposed for Phases III through IV.

PHASE III – Framework Development

Task 11. Develop the framework and the complementary tools according to the approved Interim Report No. 2.  

Task 12. Develop draft language for consideration by AASHTO to incorporate the research findings in the next update of the appropriate AASHTO specifications, hereafter called the AASHTO Deliverable.

Task 13. Prepare Interim Report No. 3 that documents Task 11 and 12.

PHASE IV – Final Products

Task 14. Revise the framework, the complementary tools, and the AASHTO Deliverable after consideration of the panel’s review comments.

Task 15. Submit the draft final deliverables including (1) a final research report documenting the entire research effort and findings; (2) framework and the complementary tools; (3) the AASHTO Deliverable; (4) prioritized recommendations for future research; (5) presentation material and resources; and (6) technical memorandum on implementation.

STATUS: Proposals have been received in response to the RFP. The project panel will meet to select a contractor to perform the work.