Crushed granite stone is produced in large amounts during the cutting and processing of granite rocks at manufacturing factories. Thus, an attempt has been made here to define the role of crushed granite in enhancing the geotechnical behaviour of expansive soil in order to make it suitable for construction. In addition, this study aims to assess the use of granite stone and incinerated waste ash to stabilize expansive soils for subgrade. On natural and stabilized expansive soils using a constant portion of crushed granite as 30% with an increment of incinerated waste ash portion with a varying range from 2% to 8%, extensive geotechnical tests such as Atterberg limits, compaction characteristics, California bearing ratio (CBR), and swelling percentage have been carried out. The outcomes demonstrated that crushed granite stone is a useful tool for controlling swelling behaviour and enhancing soil plasticity. Furthermore, the findings demonstrated that CBR rises when incinerated waste ash content increases and that this increase peaks at 6% with a maintained 30% of crushed granite stone before declining. Therefore, this sum might be considered the ideal value of incinerated waste ash and crushed granite stone respectively.