Strengthening of soft subgrade soil using industrial waste iron powder and recycled plastic mesh
Construction of pavement on expansive or soft subgrade soil demands great deal of attention. It is more important to concentrate on strength of the soil layers underlying the surface course, because the strength, thickness and design life of pavement are mainly depends upon the subgrade strength. There are many alternative methods available in order to improve the strength of subgrade. Soil stabilization is an effective method of improving soil properties. Subgrade strengthening using geogrids, geotextiles, and geomembranes as soil reinforcement are most widely used methods. Now a days use of industrial wastes as admixtures for soil stabilization has become trendy method in order to reduce the environmental hazards. In the present study an attempt was made to strengthen the soft subgrade soil using industrial waste iron powder (IP) as an admixture and recycled plastic mesh as soil reinforcement. Black cotton soil was collected from kharanja dam, bidar district. First soil was blended with different percentages of iron powder i.e. 4,5,6,7 and 8% and for all those proportions compaction tests, atterberg limits and laboratory CBR tests were conducted for UnSoaked and soaked conditions. From the tests we got 6% as the optimum percentage of iron powder. Similar to geogrid, three types of recycled plastic meshes having different aperture sizes and colours i.e. black grid mesh (BG), light green mesh (LG), dark green mesh (DG) were used as soil reinforcement. Soil specimens reinforced by three layers of each type of plastic meshes were prepared and for all those specimens laboratory CBR tests were performed in both soaked and UnSoaked conditions. Further work is carried out to know the combined effect of iron powder and plastic mesh on soft subgrade soil. Finally in order to know the interaction of black cotton soil- iron powder- plastic mesh, soil specimens were prepared by combining the optimum percentage of iron powder i.e. 6% and plastic mesh with highest CBR value i.e. BG mesh. The combined proportions are as follows; BC soil+6% IP+ single layer of BG mesh positioned at the centre, 1/3rd from the top and 1/3rd from the bottom of the specimen respectively. BC soil+ 6% IP+ 2 layer of BG mesh positioned at 1/3rd points from both top and bottom of the specimen. BC soil+ 6% IP+ 3 layers of BG mesh positioned at the centre and 1/3rd points from both top and bottom of the specimen. The UnSoaked CBR values show considerable increase in strength than soaked CBR values.
Industrial waste iron powder, recycled plastic mesh, MDD, OMC, CBR