Dry density vs water content graph for different percentage (0% to 20%) of RHA treated soil is shown in Fig. 4. MDD and OMC value for different content of RHA treated soil are listed in Table 6. Variation of MDD and OMC for different percentage of RHA in organic soil are shown in Fig. 5. As per the data revealed in the Table 6 and the Fig. 5, it can be undoubtedly said that the MDD diminishes but OMC upsurges gradually with increase in different percent of RHA content in organic soil. The MDD value decreases from 16.66 kN/m3 to 13.08 kN/m3 whereas the OMC enhances from 12.23% to 16.88%. Parallel trends in OMC and MDD were reported by several previous studies (e.g: Sarkar et al., 2012; Alhassan, 2008; Ramesh and Kumar, 2009; Sabat and Pradhan, 2014; Gupta and Kumar, 2016; Okafor and Okonkwo).
The decrease in the MDD can be ascribed to the replacement of clay by the RHA in the mix. This is owing to relatively small specific gravity of RHA (2.18) than the specific gravity value of replaced soil (2.55) and another reason may be the preliminary synchronous flocculation and agglomeration of soil Particles due to cation interchange. In contrast, the OMC of stabilized soil increases as percent of RHA increases. This is due to the fact that the RHA particles are hollow and they require more water for their absorption and well lubrication.