- Author
- Petersen, P. H. | Watstein, D.
- Title
- Shrinkage and Creep in Prestressed Concrete.
- Coporate
- National Bureau of Standards, Washington, DC
- Report
- NBS BSS 013, March 22, 1968, 14 p.
- Keywords
- prestressed concretes | creep tests | shrinkage
- Identifiers
- relaxiation; loss of prestress; variable prestress
- Abstract
- The loss of prestress resulting from creep and shrinkage in concrete was investigated for concrete specimens made with Type I portland cement and with Type III portland cement. The primary variables in this study were: 1. Relative humidity at which the concrete was maintained while under observation; 2. Age of the concrete at the time it was prestressed; 3. Ratio of prestress to strength: variation of this parameter required that the ratio of reinforcement be a variable; 4. Mass ratio factor defined as the ratio of the cross-section area of concrete specimen to its surface area per unit length. Forty-nine sets of specimens were fabricated and tested; each set consisted of a prestressed specimen and an otherwise identical companion specimen without reinforcement. The length changes with time were observed at intervals up to an age of 500 days. These observations were made for concretes subjected to different levels of prestress, and for concretes prestressed at different ages. Length changes in nonreinforced companion specimens were also obtained. Thus this study is concerned with elastic deformation occurring at time of stress transfer, shrinkage or swelling, and creep.