Improvement of characteristics of sand mixing with natural coir fiber

For expansion of land transportation system in India large number of road constructions is being made through different Government schemes. Such constructions require massive quantity of good brickbats for construction of subbase as per conventional method. Farming lands, which contribute soil for brick manufacturing is becoming scarce in India because of low per capita land holding and also use of agricultural lands encourages sociological problems in the neighbourhood. Further for burning brick large energy is consumed while in India conservation of energy is of highest priority. In view of this Government of India is emphasizing on use of alternate material to replace brickbats for construction of subbase.

Also, use of natural fiber materials, from coir, jute, etc. as reinforcing materials in soil is well-known for a long time for their use as soil reinforcement (additive material) and they are largely used in many countries like India, Ceylon, Philippines, etc. The main advantage of these materials lies in the fact that they are very cheap, eco-friendly and are also easily available in abundance in many countries. They can be used as additive material in the sub base course employing sand to have increased strength and decreased deformability.

Due to high permeability, sand is conventionally being used as mineral filter in layer along with conventional subbase. Due to restriction of use of brick bats in making subbase, search for alternative material for brick bats in construction of subbase is going on. Possibility of using solely reinforced sand in place of conventional subbase is worthwhile because natural fibers and sand are available in many locations.

In view of above, a systematic experimental program was undertaken with different sand coir fiber composites to be used in such cases. Standard Proctor tests were carried out on mixing natural coir fiber in various proportions and various lengths with three different types of sand i.e. fine brown sand, medium brown sand, and fine whitish gray sand to find optimum moisture content (OMC) and maximum dry density (MDD) of each case. California Bearing Ratio (CBR) tests were conducted at optimum moisture content of each case. The results indicate that CBR value is maximum for 5 mm Coir fiber length for all types of sand. It is observed that Optimum percentage of fiber inclusion is 1.5% of the dry weight of sand for fine brown sand, and fine whitish gray sand while for medium brown sand optimum percentage of fiber inclusion is 1.0% of the dry weight of sand, beyond which the CBR value starts to decrease.