The soft subgrade imposes problems on geotechnical/pavement engineers when designing road pavements and construction platforms, as its modulus and bearing capacity do not meet the requirements to support the design load. The issues are more challenging when the soft subgrade consists of expansive clays that are widely spread in Queensland, Australia. The subgrade replacement, lime treatment, and a thicker granular cover over the subgrade are widely used to treat soft and expansive subgrades. However, these subgrade treatment methods impose numerous environmental and financial concerns as they use depleting natural resources producing dust and greenhouse gases. Therefore, the research on construction and demolition waste has suggested using recycled concrete aggregates (RCA) and recycled asphalt pavement (RAP) as natural gravel replacements, Further, ongoing research is investigating the use of waste such as fly ash, incinerated ash, and slug to treat the soft and expansive subgrades.