Subgrade CBR improvement with fly ash as mineral and NaOH as a chemical admixture

Increase in the rate of traffic volume and heavy vehicle loads gave a revolution in highway construction technology, this increase is due to continuous growth in economic activities. Therefore, it is necessary to construct highly durable and serviceable road structures on any type of soil. In continuation, a good subgrade can influence the thickness of road structure, increases the strength pavement, and reduce the cost of road structure construction. California bearing ratio (CBR) is a generally used in-direct method to estimate the strength of sub-grade and it directly gives the pavement thickness in pavement analysis and design work. So, if increasing in the CBR value results thicknesses of the pavement will decrease and it, in turn, reduces the construction cost of the pavement structure. In the present investigation, the collected soil samples are Black Cotton soils from Dharmapuri, Vizianagaram, AP. Same soil stabilized with various replace percentages of Fly ash (i.e.10, 20, 30, and 40%) and NaOH (i.e. 3, 5, and 7%). The Atterberg limits, Free swell Index, and CBR tests were completed on original and stabilized soils. Finally, authors observed that the considered BC soil stabilized with mineral admixture (Fly ash) and chemical admixture (NaOH) results in more than 400% increase in CBR with 40% decrease in pavement thickness, and 25% decrease in pavement construction cost.