ABSTRACT
Use of carbon fibre reinforced plastic, CFRP, as prestressing reinforcement for concrete structures, has increased rapidly for the last ten years. The non-corrosive characteristics of CFRP reinforcement significantly increase the service life of the structures. In addition, CFRP prestressing reinforcement has the advantages of a high
Serviceability of prestressed CFRP beams 405
2.1 Material properties The concrete used for casting the ten beams was provided by a local supplier and the beams were cast 12 hours after jacking. The maximum aggregate size was 14 mm and the measured slump was typically 200 mm. The specified water/cement ratio was 0.37 and the cement content was 400 kg/m 3. The mix proportions by weight was 1 (portland cement) : 2.9 (coarse aggregate) : 1.7 (fine aggregate). Rheobuilt 1000 superplastisizer with 3 litre/m 3 was used to increase the concrete workability. The target compressive strength of the concrete was 30 MPa after 3 days. Twelve concrete cylinders were cast for each patch and were tested in compression before release and at the day of testing according to ASTM C39-86. The elastic modulus as well as the tensile strength of concrete were also evaluated at the day of testing based on ASTM C469-87a and C496-90, respectively. The measured compressive strength of the concrete cylinders varied between 37 to 50 MPa at the time of release and between 47 to 70 MPa at the time of testing. The average elastic modulus was ranging between 29,000 to 38500 MPa, while the average tensile strength, determined from beam test according to ASTM C78-84, was ranging from 5.1 to 7.5 MPa.
