The two major exit ramps to Interstate 5 in downtown Seattle, Washington needed to be reconstructed. High volume of traffic and high incident of accidents required less closure time for construction. Therefore, paving was conducted with fast track concrete mix and maturity was monitored to determine opening strength for concrete.
Both maturity and fast track have been around for some time now. However, the idea of using concrete maturity values to determine the opening strength for pavement is a relatively new concept. Prior to the field application of fast track concrete mix and concrete maturity, numerous tests were conducted. Tests included the maturity value determination for an opening flexural strength of 400 psi and the insulating factor needed for fast track paving.
Test results showed that a maturity value of 400 degrees C-hour is needed for a flexural strength of 400 psi. And also, an insulating factor of 3 (R=3) is sufficient to obtain the opening flexural strength of 400 psi in eight to twelve hours after placement of concrete. With this test information, paving was performed at the ramps of the Albro St. and Spokane St. exits. Pavement achieved the required opening strength of 400 psi in eight to eleven hours after placement of concrete. Reconstruction of the ramps was completed in two days with fast track paving.