Characterization of granitic rock laterites in Bamendou (West-Cameroon) : significance in the sustainable pavements design

Abstract

Abstract This research focuses on the impact of cement addition on the improve the bearing capacity of sub-base soils and the lifespan of pavements in Bamendou-Western Cameroon. To carry out this study, nine lateritic soil samples were selected and taken. Following this, several tests were carried out on them in order to determine their geotechnical parameters. The results obtained show that they have an average plasticity index of 12.13. The average percentage of fines is 44.53% for a dry density of 1.58 g/cm3. The average CBR value is 8.29%.The multiple linear regression performed between CBR, percentage of fines and plasticity index shows a correlation coefficient of 0.72; however, a correlation between CBR value, liquidity limit and plasticity index shows a correlation coefficient of 0.85, characteristic of a strong correlation between the variables. Following these results, Cement stabilisation was carried out at proportions of 2%, 4%, 6% and 8% in order to improve the bearing capacity of the soils studied. The results obtained show that for a change from 2–4% cement, the average CBR value obtained is doubled, from 21.27–42.77%. Moreover, this average value increases with the increase of the stabilizer rate, but no longer to a great extent. It was concluded that cement modifies the geotechnical properties of the treated materials, making them more able to withstand overloads. Once the CBR values of the improved soils had been obtained, the pavements were sized using the Alizé-LCPC software. The thickness of pavement layers decreases with increasing cement content. Following the reverse calculation, the gain in terms of service life of the structure for an addition of 2% cement is 4.40 years. It was possible to make proposals for the prescription of a cement stabilisation rate for use as a pavement subgrade; it was found that from an economic and technical point of view, the best stabilisation rate for engineers is 6% cement.