Study of the variability of lateritic gravels for pavement construction in tropical countries: A case study from Burkina Faso

Lateritic gravels are soils formed through intense physical and chemical weathering of bedrock under tropical climates. Their formation is influenced by various factors, such as geology, climate, topography, the time and biological activity. These factors affect the physical properties and contribute to a wide range of lateritic soil types, each with distinct mechanical behavior. Due to their availability and characteristics, lateritic gravels are widely used as key materials in road construction across tropical regions. However, the absence of a standardized process for selecting and applying lateritic gravels often leads to the use of unsuitable materials or inappropriate application conditions. This results in construction delays, increased costs, and compromised road quality. Although international standards for soil classification exist, they often lack the precision needed to effectively guide the selection of lateritic gravels under the specific context of many sub-Saharan countries. Moreover, there has rarely been scientific research addressing this challenge. This research aims to investigate lateritic soils from Burkina Faso in order to better understand their variability and provide pratical recommendations for their improved use in road pavement construction. A total of 661 lateritic samples were collected analyzed using statistical methods. These samples were also classified according to four international soil classification systems and subjected to laboratory testing. The results indicate a low variability of lateritic gravels at the scale of the country under the four international classification systems, except for the Brazilian system. So, an approach combining mainly Brazilian classification system, the other classification systems and the local practises were adjusted for lateritic soils classification in Burkina Faso. This approach is more suitable and highlights more groups of lateritic soils t. It also considered critical parameters, as particles size distribution (PSD), plasticity index (PI), CBR index, the fragmentability (FR) and the friability (FS) indexes, affecting the performance of lateritic gravels.