Improved calibration procedure for British pendulum tester

Abstract

Regular periodic calibration is important to ensure the accuracy of measurements of British pendulum test (BPT). The current standard calibration procedures of BS EN 13036 and ASTM E303 are widely adopted by pavement engineering community. Studies by different research groups have shown that test results of BPT devices complying with standard calibration requirements have good repeatability, but could have deviations of 10%or more. The present research presents a detailed examination of the impact of the limiting values of the main calibration parameters of BPT devices. Since it is difficult to study by means experimental measurements the impact of any pendulum parameter value within the allowable range on BPN (British pendulum number), a finite element model was adopted in this research based on the mechanics of the BPT test process. The simulation results showed that BPT devices satisfying the calibration requirements of any standard could produce measurements with uncertainty of more than 23% of their mean test value. By tightening the calibration parameter range according to the actual needs of the user, this study shows that the uncertainty of the BPT measurements can be controlled within an acceptable range.