ABSTRACT:- The best method for improving the physical properties of soil like; increasing strength such as shear strength, bearing capacity, etc. is the process of Soil Stabilization. This procedure includes addition of the admixtures into the soil in order to increase the properties of the soil. The admixtures such as; cement, lime and waste materials like fly-ash, phosphor gypsum, etc. are very expensive materials. The cost of these kind of admixtures is increasing day by day as the technology is improving around the every corner of the society. In recent technology and research, utilization of waste materials likes plastic, bamboo etc. The widely used thing in today's society is the plastic. The disposal of these plastic wastes causes the ecological hazards, a big threat to our surroundings but we have a solution, we have found in this research work that the waste plastic is a useful thing in stabilization. In the modern world, there is a scarcity of a good soil. Since the low availability of un-stabilized soils makes it difficult for the construction. To avoid problems like these, we will have to overcome them, for this we will have to add suitable admixtures to the soil. This research work includes the addition of the suitable admixtures such as plastic waste like bottles. These plastic waste materials like plastic bottles are used in this project. For this to happen the plastic bottles are cut down into small strip like pieces. The addition of these small strips in the soil by different percentage and conduct tests such as liquid limit, plastic limit, compaction test, CBR test etc. Then soil becomes stabilized i.e. increasing the load bearing capacity of the soil and also strength properties such as shear strength with a controlled compaction. Soil stabilization by using waste plastic bottles which significantly enhance the strength properties of the soil.
Sub grade Stability
Sub grade stability is a function of a soil's strength and its behaviour under repeated loading. Both properties significantly influence pavement construction operations and the long-term performance of the pavement.
The sub grade should be sufficiently stable to:
1. Prevent excessive rutting and shoving during construction;
2. Provide good support for placement and compaction of pavement layers;
3. Limit pavement rebound deflections to acceptable limits; and
4. Restrict the development of excessive permanent deformation (rutting) in the sub grade during the service life of the pavement. When the sub grade does not possess these attributes, corrective action in the form of a sub grade treatment is needed.
The life of road depends on strength of the sub grade soil and traffic density. The sub grade soil is not uniform throughout the alignment of the road. Generally the poor sub grade soil having soaked Indian Bearing Ratio (IBR) value less than 2% is replaced by good quality sub grade material. The additive like RBI Grade 81is used to improve the properties of sub grade soil. The cost of construction of road increases, if only RBI Grade 81 is used as a stabilizer. The IBR value of sub grade soil can be improved by using moorum with RBI Grade 81and cost of construction can be reduced to certain extent. From IBR test, it is found that the soaked CBR value of soil is improved by 476.56% i.e. 2.56% to 14.76% by stabilizing soil with 20% moorum and 4% RBI Grade 81. The various mixes of soil: moorum: RBI Grade 81 for the different 8 proportions were tested for maximum dry density (MDD), optimum moisture content (OMC) and soaked IBR value.RBI Grade?81 has been invented to provide comprehensive and irreversible soil stabilization specifically for road construction. Treated soil is water resistant & prevents damage to the road foundation and provides better ride-ability & longer durability leading to reduced pavement maintenance cost.
WEAK SUB GRADE AND TREATMENT
The sub grade in flexible pavement is more vulnerable to failure under the vehicular traffic loading due to non- uniform distribution of the load from overlying layers and the presence of high moisture contents. This layer gets less emphasis compared to other layers in pavement, despite the fact that most of the pavement failure is being caused due to the bearing capacity failure of the sub grade layer. Some sub grade soils, especially clayey soils, have great strength at low moisture content; however they become very weak and less workable with the increase in water content beyond the optimum value. Such soil should be either replaced with superior quality fill material or treated with suitable treatment process (Prusinski and Bhattacharja, 1999). The replacement of the sub grade soil might not always be the best option due to associated hauling cost of the excavated materials as well as the imported quality materials. In some developing regions or even urban areas, the unviability of the aggregate or the shortage of the suitable fill materials makes replacement of weak sub grade soil uneconomical. In such conditions, the strength/stiffness properties of the existing weak sub grade soil can be improved by the use of proper compaction technique as well as by using some chemical stabilizers. Portland cement, lime and fly ash are the most common types of chemical stabilizers used by most of states to stabilize the weak sub grades; thus creating a proper working platform and/or sub base layer for pavement construction.
Flexible pavements are so named because the total pavement structure deflects, or flexes, under loading. A flexible pavement structure is typically composed of several layers of material. Each layer receives the loads from the above layer, spreads them out and then passes these loads to the next layer below. Typical flexible pavement structure shown in plate 1.1 consisting of:
a) Surface course: This is the top layer and the layer that comes in contact with traffic. It may be composed of one or several different HMA sub-layers. HMA is a mixture of coarse and fine aggregates and asphalt binders with or without additives.
b) Base course: This is the layer directly below the HMA layer and generally consists of aggregate (either stabilized or un-stabilized).
c) Sub-base course: This is the layer (or layers) under the base layer. A sub-base is not always needed.
d) Sub grade course: The sub grade is the material upon which the pavement structure is placed. Although there is a tendency to look at pavement performance in terms of pavement crust structure material, mix design and thickness but the sub-grade can often be the overriding factor in the overall pavement performance. The IBR value of the sub grade material is generally used to design the total pavement crust thickness as per IRC: 37-2013-2015 guidelines.
A flexible pavement structure is typically composed of several layers of material with better quality materials on top where the intensity of stress from traffic loads is high and lower quality materials at the bottom where the stress intensity is low. Flexible pavements can be analyzed as a multilayer system under 10 loading and are constructed by using different layers such as Bituminous concrete (BC), Dense Bituminous Macadam (DBM), Bituminous Macadam (BM), Wet Mix Macadam (WMM) and Granular Subbase (GSB) as per the MORTH specifications with the designed thickness as per the IRC: 37-2013-2015
Raw Plastic Bottle Strips
Plastic is a non-renewable source and bio-degradable. The disposal of waste plastic bottles causes environmental pollution, it’s a sustainable waste. Plastic can be recycled or reused i.e. reprocessing these plastic wastes makes the useful products. Such wastes of plastics be used as additives for stabilized soil.
The compaction tests were done to assess the amount of compaction and the water content required. The water content at which the maximum dry density is attained is obtained from the relationships provided by the tests. The California Bearing Ratio test is conducted for the soil by adding plastic strips with varying percentage of 0.2 i.e.0.2%, 0.4%, 0.6% etc. and determines the strength of soil until the strength reaches the highest level and stop at the interval when strength decreasing from the highest. Plot the graph and calculate the bearing value for 2.5mm penetration and 5mm penetration and value of 2.5mm penetration and 5mm penetration is recorded. Then finally plot a graph of Percentage of Plastic content and CBR value and obtained the maximum CBR value corresponds to percentage of plastic content.
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