This study investigated the gradation and compaction properties of lateritic soil treated with plantain peel ash (PPA). PPA was used to improve lateritic soil with up to 10% PPA by dry weight of soil. Tests carried out to include specific gravity, particle size distribution, consistency tests, and compaction (using British Standard light, BSL and West African Standard, WAS) compaction energies. XLSTART 2018 Software was used to develop regression models for the test conducted between the self-determining factors and the dependent factors. The results of the study show that the specific gravity of the soil significantly decreased from its natural value of 2.55 to 2.43 at 4% PPA and thereafter increased to 2.48 at 10 % PPA. The fines content reduced from 59.9 % at the 0 % PPA to 5% at 10% PPA respectively. MDD (BSL and WAS) reduced to 1.76 Mg/m3, 1.84 Mg/m3 at 4%, 6 % PPA content and subsequently increased to 1.91 Mg/m3, 2.0 Mg/m3 at 10 % PPA content respectively. OMC for BSL decreases to 11.8 % at 10 PPA content while WAS was decreased to 8.6 % at10 % PPA content. Regression models for MDD show that self-determining factors, primarily influence the MDD of treated soil. However, in the case of OMC model, Gs and CE with higher coefficients have much more effect on the OMC compared to other variables. Based on the obtained results Gs, CE and PPA significantly affect grading and compaction characteristics of PPA treated the soil.                                                                                      Keywords—Compaction Characteristics, Grading Properties, Lateritic soil, Plantain Peel Ash, Regression Models

This study investigated the compaction effect of unmodified and modified lateritic soil using cement-mango leaf waste ash (C- MLWA). The lateritic soil used was classified as A-7-6 (9) and CL using AASHTO soil classification and USCS respectively. The soil was treated with a blended cement of 1%, 2 % and 6 % mango leaf waste ash by dry weight of the soil sample. Effect of cement- mango leaf ash on the modified soil was studied with respect to compaction characteristics, plasticity characteristics, particle size distribution, California bearing ratio, and unconfined compressive strength. Compactive efforts used were British Standard Light (BSL) and West African Standard and the results were examined utilizing analysis of variance (ANOVA) Method. The research shows an increase in MDD with the corresponding decrease in OMC as the percentages of cement content increase with a constant 6% mango leaf waste ash for all the tests carried out for the sample. This was due to the agglomeration of large particles (sand and gravel) consuming bigger space with a comparable drop in dry density and in light of additional moisture needed for the hydration of cement and the pozzolanic response of mango leaf waste ash.

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A first-order reliability method (FORM)was employed to assess the compaction water content, CWC (i.e optimum moisture content) of residual lateritic soil mixed with plantain peel ash (PPA) and compacted with British Standard Light (BSL)and British Standard Heavy (BSH)energies, for flexible pavement applications. A Multi-linear regression model was generated from values obtained via laboratory tests using Mini-tab R15 software, which served as a performance function that was applied for the analysis. Using the regression models for CWC, established distributions for the relevant soil factors, safety index (SI) was computed using CWC as a dependent factor and the soil factors Plantain Peel Ash (PPA); Plasticity Index (PI); Percentage File (PF); Specific Gravity (Gs) and Compactive Effort (CE)as self-determining factors). The results revealed that the safety index is sensitive to changeability in the soil factors. Outcome from the analysis show that Gs and CE are greatly affected by alteration in the coefficient of variation (COV), and so it is essential to control Gs and CE in lateritic soil–PPA mixes in road pavements. From the safety index values it reveals that PPA content has a minimal consequence as its value virtually remained constant at all COV used. Stochastically, lateritic soil mixed with PPA produces an acceptable safety index value of 1.0, as mentioned by the Nordic Committee on Building Regulation (NCBR) at 10% COV for BSH of compaction water content only. Therefore a more effective additive such as cement, lime, or bitumen is recommended for modeling CWC of lateritic soil-PPA mixes for road pavement at 10–100% series of COV. Keywords: Coefficient of variation; compaction water content; lateritic soil; plantain peel ash; reliability index