BACKGROUND
Shrinkage cracking poses a significant challenge to the durability of concrete infrastructure. The 2022 National Concrete Consortium survey ranked bridge deck cracking as a critical area requiring research. NCHRP Synthesis 500: Control of Concrete Cracking in Bridges emphasized the necessity for specifications to control shrinkage cracking and advocated for further investigation into shrinkage-reducing admixtures, cementitious materials, and internal curing to mitigate cracking in concrete mixtures. Existing test methods do not measure total shrinkage (autogenous plus drying) in concrete and often overlook field-specific variations in materials, construction practices, and restraint conditions.
Research on concrete shrinkage cracking is needed to develop informed design guidelines, optimize construction practices, and create more accurate performance predictive models and effective crack mitigation strategies, ultimately improving the long-term durability of concrete structures.
OBJECTIVES
The objectives of the research are to develop (1) a method(s) to measure total shrinkage of concrete (autogenous and drying) applicable to a variety of current and emerging binders and mixtures and (2) acceptance criteria for qualifying concrete mixtures by integrating test results with field-specific variations to predict cracking.
Accomplishment of the project objectives will require at least the following tasks.
TASKS
PHASE I – Planning
Task 1. Conduct a literature review of research related to shrinkage measurement test methods (e.g., autogenous, drying, restrained, unrestrained) for concrete mixtures. The review shall include domestic and international research from published and unpublished sources, as well as contacts with public and private organizations.
Task 2. Based on the literature review performed in Task 1, identify (a) limitations and strengths of the currently used test methods (e.g., accuracy, reliability, cost, practicality) and technologies (e.g., optical sensing, embedded sensors) to quantify concrete shrinkage in the laboratory and the field and (b) knowledge gaps with respect to existing shrinkage thresholds and acceptance criteria for qualifying concrete mixtures for various transportation infrastructure applications and field conditions to minimize cracking (e.g., existing mortar tests may not be directly applicable to the concrete mixture). These gaps should be addressed in the proposed work plan for execution in Phase II.
Task 3. Based on the work performed in Tasks 1 and 2, prepare a detailed research plan for execution in Phase II. At a minimum, the research plan shall include:
- Development of new or modified testing method(s) for measuring shrinkage to address the knowledge gaps found in the literature review.
- Development of a procedure with acceptance criteria for qualifying concrete mixtures. The proposed procedure can be based on predictive tools, decision trees, prescriptive models, or performance-based options.
- An experimental investigation incorporating both laboratory testing and field validation. Field validation shall be conducted against field-observed crack densities on various bridge deck and/or pavement projects to demonstrate the reliability of the proposed method(s) for predicting shrinkage cracking in the field.
- Specific details on key aspects of the proposed method(s), such as repeatability, reproducibility, and applicability to various concrete materials, mixtures, structures, construction practices, and climate conditions.
Task 4. Prepare Interim Report No. 1, which documents the research performed in Tasks 1 through 3 and provides an updated work plan for the remainder of the research, no later than 6 months after contract award. The updated plan must describe the process and rationale for the work proposed for Phases II and III.
PHASE II – Execution
Task 5. Execute the work plan based on the approved Interim Report No.1.
Task 6. Based on the developed method(s) and acceptance criteria, prepare draft languages for consideration by the American Association of State Highway Officials (AASHTO) to incorporate the research results in future editions of the AASHTO Standard Specifications for Transportation Materials and Methods of Sampling and Testing and AASHTO Provisional Standards (hereafter called the AASHTO Deliverables) (see Special Note B).
Task 7. Prepare Interim Report No. 2, which documents Tasks 5 and 6 and provides an updated work plan for the remainder of the research, no later than 23 months after approval of Phase I. The updated plan must describe the process and rationale for the work proposed for Phase III.
PHASE III – Final Deliverables
Task 8. Revise the draft AASHTO Deliverables based on the approved Interim Report No. 2.
Task 9. Prepare a stand-alone technical memorandum titled “Implementation of Research Findings and Products”.
Task 10. Prepare presentation materials for webinars, in PowerPoint or other formats, to facilitate the use and adoption of the AASHTO Deliverables.
Task 11. Submit the final deliverables, including (1) a final report that documents the entire research effort, (2) the AASHTO Deliverables, (3) the Implementation of Research Findings and Products, and (4) the presentation materials.
STATUS: Proposals have been received in response to the RFP. The project panel will meet to select a contractor to perform the work.
