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Voids under a concrete slab are common in composite pavement because of difficulties in controlling grouting treatment. To evaluate grouting treatment for composite pavement accurately and then to optimize the grouting scheme, the modulus of subgrade reaction (the k-value) was proposed as the evaluation criteria of grouting treatment. Based on deflection basin data acquired by a falling weight deflectometer (FWD) on a test road, k-values under slabs were backcalculated and various treatment schemes were compared by statistical methods. Results show that grouting treatment makes the average support strength in the first and second lanes of test road increase by 11.21 % and 13.16 %, respectively. Grouting under the center of a slab has a negative effect on pavement strength. Hence, a four-hole grouting scheme is recommended instead of the five-hole grouting scheme. Besides, pavement grouting can also significantly strengthen the support under adjacent slabs that are not treated directly.

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