This paper discusses for the first time the use of noninvasive and nondestructive microwave spectroscopy to analyze the effect of chemical treatment on the absorption properties of waste rubber aggregate material when it is reacted and heated with bitumen. Oxidation and cross-linking was used to treat the waste rubber aggregates. The surface properties of oxidized rubber were analyzed using scanning electron microscopy. The bitumen samples obtained from treated and untreated rubber-bitumen blends were analyzed using microwave spectroscopy. This technique was to measure instantaneously the reduction in absorption properties of rubber when it is reacted with bitumen after treatment, compared with the bitumen samples obtained from untreated rubber-bitumen blends before treatment. The results of the scanning electron microscopy analysis show that the surface properties of waste rubber have been changed, developing surface roughness after the oxidation process. This was consistent with the microwave spectroscopy results in which the chemical treatment successfully reduced the absorption of light fractions from bitumen to rubber. Thus, residual bitumen from treated rubber-bitumen blends is comparable with the pure bitumen in its behavior and operation. This finding will have a huge impact on industry for real-time measurement.