All pertinent data and information collected at the NAPTF is arranged by construction cycles. A construction cycle includes test pavement and instrumentation layout, traffic pre and post-test plans, materials testing data, construction test data, traffic data and post-traffic testing (trenching activities and other tests), and pavement removal. A typical construction cycle at the NAPTF is shown below:
Each pavement test item is designated by its construction cycle (CC) number and three characters. The first character denotes the subgrade strength (L-low, M-medium, and H-high). The second character denotes the type of pavement (F-flexible or R-rigid). The third character denotes the type of base (S-stabilized, C-conventional, or on G- grade). For example, CC1, LRS refers to low-strength subgrade rigid pavement with stabilized base constructed during construction cycle 1. CC3, LFC refers to low-strength subgrade flexible pavement with conventional base constructed during construction cycle 3. LFS refers to low-strength subgrade flexible pavement with a stabilized base.
The pavement test items, locations of the sensors, and position of the vehicle load modules within the NAPTF are oriented in an east/west direction. An x, y, z coordinate system applicable to all construction cycles is used to uniquely identify the location of each of the test items, test vehicle components and sensor installations. The origin of this system is at the centerline of the pavement surface at the west (low-strength) end of the facility. The longitudinal coordinate x = 0 starts on the pavement centerline on the west end and increase to x = 900 feet (east). Transverse distances are measured relative to the centerline. Positive y coordinates increase to the south to y = 33 feet and negative coordinates increase to the north to y = -33 feet. Vertical (z) locations are measured from the top-of the original pavement surface. The z coordinate is positive downward (instrumentation in an overlay would reflect a negative z ).
The instrumentation at the NAPTF consists of over a thousand sensors of various types distributed among the test items. Sensors are divided into static sensors and dynamic sensors.
Static Sensors collect data on an hourly basis.
Dynamic sensors are triggered by movements of the load vehicle. Therefore, dynamic sensor responses are collected only on days when the load vehicle is in operation.
The various types of sensors used are displayed in the table below.
|Static Sensors||Dynamic Sensors|
|Temperature Gages||Multi-Depth Deflectometers (MDD)|
|Moisture Gages||Asphalt Strain Gages (ASG)|
|Resistance Gages||Concrete Strain Gages (CSG)|
|Humidity Gages||Joint Gages|
Construction Cycle data for CC1, CC2, CC3, CC4, and CC5 can be querried from the databases page.
The following images show the NAPTF though it various construction phases. Click on the thumbnail to view a larger image.
|Forms being prepared for P-501 Placement. View of deck finisher in the background.|
|Aerial view of NAPTF facility under construction.|
|20 mil membrane on the floor of the low-strength subgrade.|
|Start of asphalt paving. View from top of vehicle. Beam in foreground was used to support the CBR measurement equipment and a water spray bar.|
|View of the test vehicle from the top of the low-strength subgrade. The soil is drying after being tilled with the pulvermixer (10/25/98).|