# Evaluation of the Impact of Fines on the Performance of Sub-Base Materials
## 5 Conclusions  
The current study was carried out to study the effect of fines on the performance of sub-base materials. Classification and quality assessment tests were performed on composite sub-base samples. The laboratory test results were utilized to design a pavement following AASHTO 1993 guidelines. On the basis of the study, the following conclusions were drawn:  
1. The impact of blending fines with sub-base materials on the compaction characteristics is subtle as the maximum dry unit weight decreased only by about 4%, whereas the optimum moisture content increased by about 3% with the addition of fines up to 15%.
2. The permeability characteristics of sub-base materials showed a drastic change with the increase in fines and the drainage characteristics of the blended samples changed from fair to very poor. The plasticity of the fines present in the sub-base materials has a significant impact on the prediction of the drainage characteristics of the sub-base materials.
3. The California bearing ratio (CBR) of the sub-base materials decreased with the increase in fine content. The sub-base materials exhibited a maximum strength and fair drainage characteristics at a 0% fine content. With the addition of non-plastic fines up to 10%, the sub-base material exhibited a good strength (CBR > 30); however, the drainage characteristics were poor. With the addition of 15% of non-plastic fines and more than 5% of medium-plasticity fines, the strength was substantially reduced (CBR < 30) with very poor drainage characteristics, thus making the material unsuitable for road construction. The addition of only 5% of high-plasticity fines or more than 10% of medium-plasticity fines resulted in very poor strength/stiffness and drainage characteristics of the sub-base material.
4. The results of the pavement design using AASHTO 1993 guidelines using the composite samples of the sub-base materials depict that the required thickness of the base course layer increases by 72\(\sim\)118% with the respective addition of 5\(\sim\)15% of plastic fines as compared to the case of not adding fines. However, the same amount of non-plastic fines results in a 27-55% increase in the base course thickness.
5. Based on the overall evaluation, we conclude that the mixing of non-plastic fines with a sub-base material up to 5-6% results in improved compaction, good strength, fair drainage, and a minimum requirement of increased base course thickness.  
Figure 11: Thickness of the various pavement layers for gradation C.  
Furthermore, the composite samples prepared as per the AASHTO gradation \"B\" exhibited a better strength and drainage characteristics compared to the composite samples prepared as per the AASHTO gradation \"C\".  
K.F.: conceptualization, formulation of the methodology and top supervision of the entire study. H.M.: formal analysis and writing--original draft preparation. [PERSON] provided his input for the investigation and data curation. S.Z.A. contributed to the writing--review and editing. [PERSON] carried out the final review and visualization. [PERSON] performed the visualization and writing--review and editing. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The authors highly acknowledge the support of the Department of Civil Engineering, University of Engineering and Technology, Lahore, Pakistan, for providing laboratory facilities, library access, and a research environment to accomplish the study.  
The authors declare no conflict of interest.