Statistical analysis of Nkoulou soils properties and suitability for earthen constructions

Abstract

The present work consists of sampling, characterizing, classifying, and studying the soils of the locality of Nkoulou for the manufacture of cement-stabilized compressed earth bricks (CEBs) and possible use in road building. 08 samples were taken on 02 sites. Chemical and mineralogical characterization identified these soils as ferric-dominated laterites consisting of quartz, illite, hematite, kaolinite, goethite, gibbsite, muscovite, and magnesite associated with trace minerals. The studied soils have an average natural water content of 11.73% and average values of specific gravity of 2.51 and 2.48 (respectively for site N°1 and site N°2). These soils are mainly composed of gravel followed by sand and are classified as Group B fine-grained soils according to the French Road Grading Manual (GTR). The natural water content (W) shows a good correlation with clay content (R = 0.75), and silt content (R = 0.73). The CBR Index (ICBR) meanwhile has a good correlation with the silt content (R = −0.69), similar between ICBR and maximum dry density (R = 0.73). According to CRATERRE Nkoulou soils can be used as well in the manufacture of CEBs as in the realization of road works in layers of fill. The cement stabilization of the compressed soil specimens allows the mechanical strength to increase with the stabilization rate, just as the water absorption of the specimens which also varies with the fines content, and the curing time according to the correlation study. These results allow us to establish the predictive model of compressive strength and flexural strength as a function of cement content and time with R2 = 0.75 and R2 = 0.93, respectively.