Originally published in 1998
By Jerry Daleiden, P.E. and Tim Martin, EIT, Brent Rauhut Engineering
AUSTIN-Non-destructive structural evaluations have proven to be a cost-effective tool for agencies to assess existing conditions of in-service pavements.
During a recent project at the Mesquite Airport, non-destructive testing practices were employed to evaluate a tie-down apron using an 8000E falling weight deflectometer (FWD) to conduct structural evaluations. The FWD test results allowed engineers to evaluate the structural capacity of the existing apron and locate areas of weakness in the pavement and subgrade. The joints of the concrete pavement were tested with the FWD to determine the joint transfer efficiencies, which indicate the effectiveness of the dowels to transfer the load from one slab to the other.
Geotechnical investigations were also conducted to ascertain the thickness of the pavement and determine the base and subgrade material properties. The geotechnical investigation provided site-specific conditions of the soils. This was valuable for determining the moisture content of the soil. The test results identified areas of weaknesses where moisture was pooling beneath the pavement surface. Once the extent of the weaknesses and their causes were determined, it was possible to recommend cost effective maintenance and rehabilitation strategies.
A remaining life analysis was also conducted to determine the amount of lightweight aircraft that could be applied before failure should be anticipated in the pavement. Failure of a pavement can be measured in many ways. In this particular investigation, failure was assessed on the basis of accumulated damage. This was calculated by determining the amount of damage applied by the stresses of one aircraft, before the accumulated stress exceeded the strength. Once the amount of allowable aircraft was determined, an estimate of the annual traffic was then med to calculate the number of years the pavement could be in-service before rehabilitation was required.