Project Title:Performance-Based Specifications for Self-Consolidating Concrete

Project Title:Performance-Based Specifications for Self-Consolidating Concrete

PIs:Anton K. Schindler (P.I.) and Robert W. Barnes (co-P.I.)

Institution:Auburn University

Cost:$93,212

Background

Self-consolidating concrete (SCC) is an emerging material that can result in cost savings and improved durability in many transportation applications, especially Accelerated Bridge Construction. SCC is preferable to conventional concrete because SCC is placed rapidly without mechanical consolidation. The most critical performance requirement for SCC is that itremain stable (i.e. resist segregation) during transportation and placement. The Visual Stability Index (VSI) is the most commonly used measure of stability; however, the outcome of this procedure is subjective because it is based on a visual assessment. This subjectivity makes it problematic to determine mixture acceptance or rejection based on a limiting VSIvalue.

As an alternative to the VSI, the surface settlement test was recommended in NCHRP Report 628 (Khayat and Mitchell 2009) as the primary stability test for SCC. This test involves precisely measuring the surface settlement of a sample of fresh concrete as itsets. The test has been shown to give a good measurement of the development of bleeding segregation; however, the required measurement precision and sensitivity to external stimuli make the test impractical for on-site quality assurance during SCC production.

The sieve stability testfor SCC stability is commonly used in Europe (EPG 2005).It involves placing fresh SCC in a bucket for 15 minutes, then pouring a sample from the bucket onto a sieve, and allowing the SCC sample to rest on the sieve for 2 minutes. The percentage (by weight) of the SCC sample that passes through the sieveis a quantitative outcome that correlates well with the degree of segregation as well as the resulting performance of the hardened concrete. Furthermore, this test is practical for on-site use (Keske, Schindler, and Barnes 2011).

Neither the surface settlement test nor the sieve stability test is currently standardized in the United States. There is a need to standardize a test method to provide an on-site quantitative and rapid assessment of the stability of SCC. Criteria also need to be established that allow the appropriate degree of stability to be specified and assessed.With this information available, unified requirements for performance-based specifications for SCC can be developed for implementation in variety of cost-efficient DOT applications.

Objective and Work Description

Theobjectives of this proposed project aretheidentification and evaluation of the method best suited for rapid on-site stability testing of SCC as well as the development of an AASHTO/ASTM specification for this test method. Criteria for this test method will be established based on correlation with the segregation measured in various full-scale hardened concrete specimens, as well as the degradation of structural performance that results from this segregation. Guide performance-based specifications for SCC will be developed for DOT implementation in ready-mixed and precast/prestressed concrete applications. The resulting SCC will result in more rapidly built—and more durable—transportation infrastructure components.

The proposed research addresses the Performance measures and performance management research topic under the Secretary of Transportation’s State of Good Repair strategic goal. It directly addresses the suggested area under this topic titled Methods and criteria to measure performance of new materials and methods.

Why is your team best for this project?

Drs. Schindler and Barnes have led four DOT-sponsored studies of SCC properties, behavior, and performance in precast, prestressed, and cast-in-place concrete infrastructure components.They edited a 2007 book ofpeer-reviewed papers titled Self-Consolidating Concrete for Precast Prestressed Applications and have authored several SCC-related, peer-reviewed papers.Dr. Schindler has taught FHWA-sponsored SCC workshops in 15 states to over 900 engineers and contractors. He is currently the secretary of ACI Committee 237 (SCC) and has served as panel member on NCHRP 18-12 (SCC for Precast, Prestressed Concrete Bridge Elements). This team has demonstrated the expertise and experiencenecessary to perform the proposed research.

References

Keske, S.D., A.K. Schindler, and R.W. Barnes, 2011. Evaluation of self-consolidating concrete stability test methods during the production of precast, prestressed bridge girders, in Proceedings of the 2011 Precast/Prestressed Concrete Institute Convention, Salt Lake City, Utah.

EPG (Self-Compacting Concrete European Project Group). 2005. The European guidelines for self-compacting concrete. Farnham, UK: EFNARC.

Khayat, K.H., and D. Mitchell. 2009. National Cooperative Highway Research Program (NCHRP) Report 628: Self-consolidating concrete for precast, prestressed concrete bridge elements. Washington, DC: Transportation Research Board.