Abstract:
This study investigates the potential of sawdust ash and lime as soil stabilizers in road
construction, specifically addressing the challenges posed by soils with high clay and silt
content in the Karuruma to Jali Sector Headquarter road. The research aims to enhance the
engineering properties of soil to ensure stability and durability in road construction. The
specific objectives include assessing the effectiveness of sawdust ash and lime in
improving soil properties, evaluating their impact on strength and durability, determining
their sustainability and cost-effectiveness compared to traditional stabilizers, and
identifying optimal mix proportions for achieving desired engineering characteristics.
The problem of variable physical properties in clay-rich soils, which lead to instability and
structural failures, necessitates the use of stabilizers. Traditional methods using cement and
lime are widely adopted; however, the search for more sustainable alternatives is critical.
The study employs standardized laboratory tests, including sieve analysis, Atterberg limits,
compaction, and California Bearing Ratio (CBR) assessments, to analyze soil samples
from the designated road. Results indicate that untreated soil is classified as high plasticity
silt, presenting challenges for road stability.
Laboratory findings reveal that the incorporation of sawdust ash and lime significantly
improves compaction behavior, maximum dry density (MDD), and CBR values.
Specifically, optimal proportions of 6% lime and 10% sawdust ash result in enhanced soil
strength and reduced plasticity. The CBR values demonstrate marked improvement with
sawdust ash, while lime consistently enhances soil strength under varying moisture
conditions.
This research concludes that sawdust ash and lime are effective, sustainable, and cost-
effective alternatives for soil stabilization in road construction, highlighting their potential
to improve the engineering properties of lateritic soils in Rwanda. The findings support the
feasibility of implementing these materials in rural infrastructure projects. Future research
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should explore the long-term performance of stabilized soils under dynamic loading
conditions to fully assess their viability for large-scale applications.
