Evaluation of the influence of compaction energy on the resilient behavior of lateritic soil in the field and laboratory

This article presents the study of the resilient behavior of three soil horizons from a deposit of lateritic soil employed in a pavement structure in Rio Grande do Sul, Brazil. The use of lateritic soils in pavement layers is a common practice in Brazil and due to its peculiarities, its behavior must be investigated. The methodology consisted of physical and chemical characterization and resilient modulus determination. Samples from the three horizons, compacted at standard, intermediate and modified energy, were analyzed. In addition, undisturbed samples extracted from the interior and top layer of the embankment were submitted to repeated load triaxial tests for resilient modulus determination. The results indicated that the soil exhibit good behavior for pavement subgrade applications, perhaps as subbase or base course layers. The compound and universal models yielded the best correlation coefficients. Furthermore, the results showed that as the compaction energy increased, the resilient modulus also increased, as long as they are within the optimum water content and compaction degree limit. However, when subjected to immersion in water for four days, the resilient behavior decreased about 73% in relation to unsaturated samples.

Deltaic Lateritic Soil in 1:5:11 Mix Design for Producing Controlled Low-Strength Material (CLSM) for Pavement Backfill

Deltaic lateritic soil obtained from Emohua in Rivers State, Nigeria was studied to ascertain its suitability as a substitute to sand in concrete for producing controlled low-strength material (CLSM). Cement, coarse aggregate, as well as lateritic soil which replaced sand was combined in ratio 1:5:11 to produce lateritic concrete using varying water-cement (w/c) ratios at varying curing durations. Variation in the w/c ratios ranging from 0.2 to 0.5 at 0.1 intervals and the curing periods which varied between 7, 14 and 28 days were examined. As with the case with conventional concrete, strength development, as well as cement hydration took place after casting over the curing periods. Recent applications using CLSM recommends that a compressive strength of 8.3 N/mm2 or less is required for materials used as conventional compacted backfill soil or structural fillings. In a situation where future excavation is envisioned, it is recommended that the maximum long-term compressive strength of CLSM should generally have an upper limit of 2.1 N/mm2 for compacted backfill material hence, the lateritic concrete produced in this study using the 1:5:11 mix design at 0.2 w/c ratio, cured for 28 days which gave strength of 5.3 N/mm2 can be used as CLSM which primarily, can be utilized as a substitute for compacted backfill to sub-base and/or subgrade of flexible pavements. Where necessary, super plasticizer can be introduced to increase flowability of the lateritic concrete.

Improvement of deltaic lateritic soil using river sand and cement for use as pavement construction material

This study examined the effect of mechanical and chemical improvement on deltaic lateritic soils in Warri East in Delta State, Nigeria. Mechanical stabilization was carried out by adding river sand to the natural soil in various proportions, while chemical stabilization was carried out using cement and a mixture of cement and sand. Compaction and CBR tests were conducted on the natural soil before and after stabilization. From the results obtained, it was seen that the mechanical stabilization method improved the strength properties of the soil making it suitable for use as subbase materials, though not as much as the chemical stabilization method or the mixed method of stabilization. It was concluded that using a combination of cement and sand as a stabilizing agent for deltaic lateritic soils can lead to significant reduction in the amount of cement required for soil stabilization thus saving costs.