Status

Sequential Number

Identification Number

Matching Research Agency

Precast/Prestressed Concrete Institute

Principal Investigator

Student Involvement

Project Objective

1. Compare the results of the newer NASP Bond Test to the traditional Moustafa Pullout Test and evaluate the NASP test as a potential replacement for the Moustafa test, and

2. Evaluate the ability of the NASP Bond Test to predict the transfer and development lengths of strand in unconventional concretes, such as SCC and HVFA concrete.

Project Abstract

The bond of prestressing strand to concrete is an important part of a strand’s ability to develop passable transfer lengths and development lengths. While some tests have been recommended for testing bond of prestressing strand, there is currently no ASTM standard bond test. The Moustafa Pullout Test has typically been used to evaluate bond, but recently, a newer bond test from the North American Strand Producers (NASP) has been gaining popularity. However, it is still unclear how the NASP test compares to the Moustafa test. In addition to the uncertainty regarding the most suitable test method, another problem with bond testing is the limited applicability of the results. The recommended procedures for both of these tests specify a mix or mortar for the specimens, and while this procedure is adequate for comparing the relative bond of different strands from different sources, the results do not give a definitive indication of how the strands will perform in actual conditions, especially if the strand is in an unconventional concrete, such as self-consolidating concrete (SCC) or high-volume fly ash (HVFA) concrete.

Many ambiguities surround bond testing of prestressing strand, and consequently, further research is needed to compare the two current tests and then apply bond test methods to the realistic conditions that the prestressing strand will experience. The results of this research will aid in the design of prestressed concrete members constructed with unconventional concrete.

Task Description

N/A

Anticipated Benefits

Development of a standard test to predict the bond and development length of prestressing strand in pre-tensioned concrete members, resulting in safer and more reliable designs.

Modal Orientation

Milestones

Relationship to other Research/Projects

This project is supplemental to two other research projects currently underway for the Missouri Department of Transportation. One project on self-consolidating concrete for infrastructure elements, and one project on design and evaluation of high-volume fly ash concrete.

Technology Transfer Activities

The technology transfer activities will include a final research report and dissemination of the findings through a national conference via technical presentation(s) and publication(s).

Transportation Research Board Keywords

Prestressed Concrete, Strand Bond, Transfer Length, Development Length, Self-Consolidating Concrete, High-Volume Fly Ash Concrete, Transportation Infrastructure