QA/QC testing newly constructed pavements with geophysical or NDT methods is desirable because in-situ testing is possible within hours after concrete roads are poured. The methods used are aimed at determining linear elastic modulus (Young's modulus) and thickness. These measurements can also be used for maturity analysis to aid in deciding when a new road can be opened.
Quality Control (QC) may be defined as the implementation, measurement and enforcement of sound construction practices and jobsite inspections to ensure construction quality. In contrast, Quality Assurance (QA) may be defined as the inspection and testing of the completed product, in accordance with specifications intended to verify the quality of the completed pavement. These two activities are inter-related, though distinct processes.
QC programs intended to address construction quality of pavements routinely include (a) visual inspection at regular intervals during construction, and (b) careful field and laboratory testing of the quality of materials used in its construction. Results are carefully measured and archived as a permanent part of the job record, and/or used to modify field (construction and inspection) practices and take corrective action while construction is still underway.
QA programs intended to verify the quality of newly constructed or repaired pavements can incorporate geophysics with excellent accuracy, and provide a needed tool for ensuring compliance with construction requirements.
Baseline Condition Assessment
Baseline condition assessment is not a routinely practiced form of quality assurance; however, it is truly the only way to compare the overall as-built condition of a pavement to its future condition at various stages during its life. One way to establish a baseline condition where "as-built factors" can be eliminated or minimized from consideration during a future evaluation is to perform measurements on a new structure identical in nature to those that will be used for primary "screening" in the future. To establish a baseline condition assessment, only nondestructive evaluations that continuously sample the pavement surface along every centimeter or meter of its length are of value and warrant consideration. These full-coverage methods, such as ground penetrating radar (GPR), profilometers, rutting, crack-mapping (using lasers and accelerometers), or other measurements that can effectively cover a pavement along its entire length, provide baseline condition data on roughness, degree of rutting, cracking, etc. These methods are followed by point-sampling techniques such as integrated ultrasonic-seismic (SASW and impact-echo) to provide feedback about either initial quality of construction or condition as a pavement ages.
Other information about these additional methods in initial and future condition assessments is needed. Position, placement and density (PPD) of rebar or corrosion-related problems in pavements are secondary in nature to many other pavement problems. Providing a complete discourse on corrosion-induced deterioration is not appropriate to this topic.Ground Penetrating Radar (GPR)
Impact Echo (IE)
Spectral Analysis of Surface Waves (SASW) and Ultra Sonic Surface Wave (USW) Methods
Multichannel Analysis of Surface Waves (MASW) Method