Experimental Evaluation of Cement-Stabilized Macadam’s Resilient Modulus Testing Methods and Their Influencing Factors

Cement-stabilized macadam is the most often utilized material in the base course of semirigid asphalt pavement, and precisely determining its resilient modulus is critical for calculating asphalt pavement’s mechanical response and evaluating its performance. However, due to the limitations of current semirigid material mechanics theory, testing protocol, and testing equipment, there is still not a unified method for determining the resilient modulus of cement-stabilized macadam; even some basic components of testing methods, such as the loading mode, loading amplitude, and loading frequency, still do not form a standard, which, to some extent, limits the development of cement-stabilized macadam in semirigid asphalt pavement. Considering this background, this paper proposed a kind of new testing method to determine cement-stabilized macadam’s modulus by using of four-point bending beam test and conducted a series of resilient modulus tests using various testing methods for cement-stabilized macadam; then this paper compared the difference of modulus testing results among these methods and analyzed the effect of the loading method, loading amplitude, and loading frequency on the determined resilient modulus so as to present some technical recommendations for unifying the test method. The research results indicate the following: (1) loading mode: the indirect tension test’s results are close to the direct compression test, and the conventional bending beam test’s testing results are close to those of the tension test; there is an obvious difference among these four testing methods, while the new bending beam method proposed by this paper that can simultaneously determine the material’s compression and tension modulus exhibits good regularity with conventional testing method. (2) Size of loading amplitude: loading size has an obvious influence on the cement-stabilized macadam’s modulus testing results; a range of 0.1–0.2 times the ultimate load is appropriate for the base materials’ resilient modulus testing. (3) Loading frequency: the effect of frequency on the modulus testing results is not too obvious; a range of 5–10 Hz is recommended with comprehensive consideration of the test results and actual pavement response frequency.