|TO:||K. N. Kirker|
|DATE:||September 27, 1994|
|SUBJECT:||Determination of Class of Concrete for Bridge Design During Preparation of the Preliminary Bridge Plan|
The following elements should be incorporated into Preliminary Bridge Plan development on all future projects:
There have been past operational problems in acquiring the concrete class specified in the contract. The problem has to do with a rural suppliers ability to produce the higher-strength concrete consistently. The result has been low concrete strengths (which we usually accept anyway), WSDOT/contractor/supplier conflict, increased construction costs, and in many cases a situation in which rural suppliers will not bid WSDOT bridge projects.
For major project with a large volume of concrete or a unique project, it is suggested that the preliminary bridge plan development include a documented meeting with the Service Center Materials Lab concerning the concrete class to be used for the contract. For future projects the Bridge Design Section should strive to minimize the number of different concrete classes and utilize concrete strengths for design that are consistent with the realistic production capability of the local concrete suppliers. This will probably mean exclusive use of Class 4000 cast in concrete for the typical prestressed girder bridge and the use of Class 5000 cast in place concrete for the typical post-tensioned bridge.
I would like to see preliminary bridge plan development procedures for these concrete issues put together and implemented by November 1, 1994.
cc: Y. A. Mhatre
R. T. Shaefer
W. A. Whitney
J. A. Weigel, 7354
R. H. Gietz, 7365