IMPROVEMENT OF THE SUB BASE MATERIAL WITH A CBR LOWER THAN 25% BY MIXING THE LIME STONE POWDER (CaCo3): Soil Modification

VERNSONE  PHENGSOULITH; KHAMSEUM  SOURIYAMATH; PHOUTHONE  SAIYASENH; ART  MALAVONG

doi:10.71026/ls.2025.02016

Authors

VERNSONE PHENGSOULITH Faculty of Engineering,National University of Laos Author
KHAMSEUM SOURIYAMATH Faculty of Engineering, National University of Laos Author
PHOUTHONE SAIYASENH Faculty of Engineering,National University of Laos Author
ART MALAVONG Faculty of Engineering,National University of Laos Author

DOI:

https://doi.org/10.71026/ls.2025.02016

Keywords:

Soil Modification, Sub Base Course, lime powder, Water Content, Plastic Index, California Bearing Ratio

Abstract

Sub base is the layer of aggregate material laid on the subgrade, on which the base course layer is located. It may be omitted when there will be only foot traffic on the pavement, but it is necessary for surfaces used by vehicles. The sub base material shall consist of hard durable particles or fragments of granular aggregates. Sub base mobilization by using limestone (CaCO₃) is intended to determine the change of the bearing capacity of the soil as California Bearing Ration (CBR) with a mixture of lime. Soil behavior is strongly influenced by the moisture or water content. According the requirements of pavement design, CBR of sub base materials must be greater than 25 to support the load from traffic vehicles that’s the reason it is really rare to be able to find from natural borrow pits to meet the requirements. ASTM standard was applied for lab activities. The results found that the plastic index (PI) was decreased and influenced to the increasing of CBR by amount of lime powder adding. From lab result shown that the PI of soil sample is 15% and CBR is 10, 12 and 14% at 95%, 98% and 100% of maximum dry density (OMC=14.2%; MDD=1.806kg/cm²) respectively. To meet the requirements of Sub Base material, lime was added (5%, 10% and 20%) to minimize the PI and strengthening the bearing capacity and found that the PI was decreased to 13%, 9% and 9% while CBR value were increased to 13, 16 and 18% when compacted at 95%, 98% and 100% of MDD respectively. The PI was continuously reduced to 9% when 10% of lime was added and CBR were increased to 20, 24 and 27% when compacted at 95%, 98% and 100% of MDD respectively. 20% of lime was applied and influenced the PI decreased to 9% and increased the CBR to 40, 51 and 59% when compacted at 95%, 98% and 100% of MDD respectively. From the result of the research adding from 10% of lime powder was near accountable to the requirements of sub base material from this sample.