CBR Values of Black Cotton Soil and Fly Ash Blend in Soaked and Unsoaked Conditions for Road Pavements

Abstract

The experimental research work brings out the effect of Raichur Fly Ash (RFA) and Nyveli Fly Ash (NFA) on California Bearing Ratio (CBR) of Black Cotton soil. For road construction this blend is useful. CBR of soil fly ash mixtures are calculated in compacted status and making blend subjected to soaking condition. In un-soaked conditions they show better readings because of extra added resistance from forces due to capillary action, for instance when 20% of RFA is blended along with B C soil under unsoaked condition, CBR found to be 10.38%. In presence of water, fly ashes capillary action reduces and gives lower CBR and CBR of 4.56% for addition of same quantity of RFA is revealed. Fly ash with mineral calcium, they can generate cementitious gel and adds strength to complex mix. By mixing of cement to RFA and calcium to NFA, the strengths of blends increases. CBR of soils with RFA shows peaks at fly ash doses of 20% and 80%. The CBR of soil by adding NFA, increases due to soaking. CBR of soil with NFA addition increases continuously with fly ash content. It is observed that when 20% NFA is mixed to soil, the CBR in unsoaked status is 11.46%, but for soaked condition it is seen that as 23.62%.

Keywords: Black cotton soil, Calcium, California bearing ratio (CBR), Capillary forces, Fly ash, Soaked, Unsoaked

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