# A Comprehensive Review on Clay Soil Stabilization Using Rice Husk Ash and Lime Sludge
## 5 Results and Discussion  
Rice husk ash and lime sludge offer unique advantages and disadvantages in clay soil stabilization. RHA, rich in amorphous silica, provides excellent pozzolanic properties, enhancing soil properties while promoting environmental sustainability by recycling agricultural waste. Similarly, LS, high in calcium hydroxide, improves soil properties and offers a cost-effective stabilization solution by repurposing industrial byproducts. However, both materials have drawbacks. RHA can release airborne silica particles, posing health risks if improperly handled, and LS may contain heavy metals or cause pH imbalances in water bodies if not managed responsibly. This section presents the findings from the investigation into the stabilization of clay soil using RHA and LS. The results of standard Proctor compaction tests, unconfined compressive strength (UCS) tests, and California Bearing Ratio (CBR) tests are analyzed to evaluate the effects of varying proportions of RHA and LS on the clay soil characteristics. The discussion highlights the optimal proportions of RHA and LS for effective stabilization and their combined impact on improving clay soil performance. The standard Proctor compaction test results reveal significant impacts of adding RHA and LS on the OMC and MDD of clay soils. The addition of RHA increases the OMC of the clay soil, with a notable rise when 10-20% RHA is added due to the water-absorbing capacity of RHA particles. Similarly, including LS results in increased OMC values, with optimal performance observed up to 15% LS. Beyond this threshold, the OMC declines as the clay soil matrix becomes overly rigid, reducing water retention capacity. The combined addition of RHA and LS further enhances the OMC progressively with increasing amounts of admixtures. An inverse relationship is observed between MDD and the content of RHA and LS. The reduction in MDD is linked to the lower specific gravity of the admixtures compared to natural soil, resulting in less dense compacted samples. Although the reduction in MDD could indicate decreased matrix strength, this is compensated by improved cohesion and binding effects due to RHA and LS. The UCS tests show varied results based on the type and proportion of admixtures. Adding up to 4% LS enhances the UCS value, reflecting improved bonding between clay soil particles and lime. UCS increases with up to 10% RHA but decreases beyond this threshold. This decline is linked to a reduction in cohesion and internal friction, excess porosity, and unreactive RHA particles acting as fillers. The combination of RHA and LS has a synergistic effect, significantly improving UCS. However, the maximum UCS value is achieved with up to 6% RHA, indicating a lower optimal threshold when combined with LS. Higher LS proportions correlate with increased UCS, showcasing the stabilizing and strengthening potential of LS. The CBR test results highlight the influence of RHA and LS on the load-bearing capacity of clay soil samples. The addition of 4% LS and RHA leads to increased CBR values, while excessive RHA (>15%) results in decreased CBR, attributed to increasedporosity and reduced cohesive strength. Combining RHA and LS significantly enhances the CBR values overall, improving clay soil load-bearing capacity and reducing plasticity. While both RHA and LS improve CBR values, excessive usage (above optimal thresholds) can have adverse effects, emphasizing the need for precise mix proportions. The extracted results underscore the effectiveness of RHA and LS as stabilizing agents for clay soils. While each admixture has its independent impact, their combined use yields enhanced mechanical properties, including higher UCS and CBR values. However, the performance depends on maintaining optimal proportions to avoid adverse effects on clay soil strength. Regarding cost evaluation, RHA and LS are consistently more cost-effective alternatives to OPC and lime, as they are readily available byproducts from industrial and agricultural processes.