Enhancement of geotechnical properties of lateritic gravels from metamorphic rocks in Cameroon with quicklime to improve road construction material quality

Lateritic gravels are commonly used in road construction due to their favourable geotechnical properties, which can be enhanced with additives like quicklime. This study conducted geological, microstructural, and geotechnical analyses on medium-grade metamorphic rock-derived lateritic gravels (MS-DLG) and low-grade metamorphic rock-derived lateritic gravels (CS-DLG) to evaluate the impact of the genesis of lateritic gravels and quicklime addition on their geotechnical characteristics for road construction purposes. Pavement design using these materials was evaluated with Alizé III software. The results indicated that both materials are primarily composed of non-swelling minerals. CS-DLG exhibited higher plasticity (Plasticity Index, PI = 34%), a lower California Bearing Ratio (CBR = 42%), and greater compressive strength (UCS = 1.75 MPa) compared to MS-DLG, which had a PI of 27%, a CBR of 49%, and a UCS of 1.45 MPa. Despite silica/sesquioxides ratios favoring base layer applications, both materials can effectively serve as sub-base layers for pavements designed for all traffic volumes. After 7 days of curing, MS-DLG modified with 2 to 4% quicklime showed improved compaction and suitability for base layers, achieving a CBR exceeding 160%, while CS-DLG remained below this threshold. Both materials were found suitable for semi-rigid pavement structures supporting T2 traffic. For T3 traffic, MS-DLG with 2 to 4% quicklime met acceptable standards, while CS-DLG required a higher proportion of 4 to 6% quicklime for similar performance. Thus, quicklime-modified MS-DLG is more suitable for road construction than CS-DLG.