Light Weight Deflectometer Configurations for Testing Thin Asphalt Pavements

The light weight deflectometer (LWD) is used to determine fundamental soil properties such as deflection and modulus. Recently, the LWD has been investigated as a potential structural evaluation tool for thin flexible pavements to generate input data for structural performance prediction models of thin flexible pavements. The falling weight deflectometer (FWD) can be used for the evaluation of thin flexible pavements; however, the relatively high cost and logistics burden, which also may render FWD unsuitable for many local agencies, are disadvantageous for the rapid assessment of dispersed rural roadways. The LWD is a potential alternative; however, since various LWD models are available and multiple testing configurations are possible, this study focused on determining which LWD configuration(s) produce structural responses that most closely correspond to FWD. Ten different LWD combinations of base plate diameter, drop weight, and drop height were tested on two full-scale thin asphalt test sections under closely comparable temperature and moisture conditions. The LWD’s ability to indicate structural conditions was compared with that of the FWD through impulse stiffness modulus. The distribution of stress within the pavements was measured during testing. In addition, the LWD’s repeatability was assessed and found to be similar to that of the FWD. As a result, the small 5.91-in. plate diameter, 22-in. drop height, and largest available hammer weights for both LWD models obtained good repeatability and the closest correspondence to FWD when tested on thin flexible pavements.