Construction Cycle 2 (CC-2) Test Items
The CC2 main test items were constructed in 2004 and tested during the period April – December 2004. The CC-2 test items replaced the CC-1 test items in the medium strength subgrade area of the NAPTF. The new items consisted of three rigid pavement types: portland cement concrete (PCC) on conventional base (MRC); PCC on grade (MRG); and PCC on the existing Econocrete stabilized base (MRS). Three existing transitions between test items were also rebuilt, and two of these were relocated. A fourth transition was built up to final grade with a thin concrete overlay. The work covered a length of 325 ft. and a width of 66 ft. Limits of the test areas were as follows: Transition 4, station 300 to 325; MRC, station 325 to 400; Transition 5, station 400 to 425; MRG, station 425 to 500; Transition 6, station 500 to 525; MRS, station 525 to 600; and Transition 7, station 600 to 625 (station numbers are in feet, measured from the origin at the west end of the NAPTF). Test item construction was completed on April 30, 2004.
The test items were designed with overall dimensions of 75 ft. in length and 60 ft. in width. Each test item contained 20 individual slabs forming 4 longitudinal lanes with 5 slabs in each lane. The slabs were 15 ft. by 15 ft. by 12 in. in thick. The concrete specifications called for 50% class C fly ash in the cementitious mix. The fly ash was introduced to lower the flexural strength of the concrete and thereby permit the use of a greater slab thickness. The greater slab thickness helped to mitigate upward curling of the slab corners and avoid premature top-down cracking under loading. Target flexural strength was 750 psi, allowing a possible slab thickness of as much as 12 inches. Test items were designed to produce about 10,000 passes to failure under the expected loads.
Slabs in the inner lanes were connected with steel dowels on all four sides. The slabs in the outer lanes were doweled on three sides, leaving only the free outer edges undoweled. The dowels were introduced in order to provide a uniform distribution of gear loading and to minimize damage in the event that premature top-down cracking occurred at the slab corners.
A total of 282 sensors were embedded in the test slabs for data collection. The sensors were of two types, static and dynamic. Static sensors were used to monitor temperature, relative humidity, and moisture. Moisture sensors were actually placed in the subgrade. Dynamic sensors measured concrete strains and horizontal and vertical displacements. Test vehicle operations triggered data retrieval from the dynamic sensors at an increased sampling rate. Sensor data collected during both traffic and non-traffic time periods were processed and stored in a computer database maintained on-site. The CC2 database can be searched online using the tools below.
Summary of Daily Traffic Repetitions
Traffic data for the rigid pavement test items are available. Daily and monthly traffic repetitions, as well as current traffic totals, are given for each test item. It is strongly recommended that users consult this table to become familiar with the trafficking history before searching the static and dynamic data.