Waste drilling slurry from cast-in-place pile construction, after dewatering and stabilisation processes, could be reused as pavement foundation materials. One of the most important factors that influence the strength of the stabilised drilling slurry is the moisture content of the dewatered drilling slurry before stabilisation, which, however, is difficult to control in engineering practice. In this paper, dewatered drilling slurry from a construction site was prepared at different moisture contents and treated with various contents of cement. Through a series of unconfined compressive strength tests and CBR tests, it was found there was a linear relationship between cement content and material strength at any specific moisture content. A contour plot was also developed, which can be used to guide the stabilisation of the dewatered drilling slurry at various moisture contents to achieve a target strength. This was then applied to the treatment of the drilling slurry in an on-site plant and the results match prediction.