Authors: B.Lavanya, Assistant Professor M.Harish Kumar
Abstract: This study stabilized two potentially hazardous industrial waste materials—Fly Ash (FA) and Lime Sludge (LS)—using Commercial Lime (CL) and Gypsum (G), respectively. The FA and LS come in large quantities from thermal power plants and water treatment plants, and they pose environmental hazards. The goal was to make the sludge and FA suitable for use in Civil Engineering construction applications. Tests for Unconfined Compressive Strength (UCS), California Bearing Ratio (CBR), and Split Tensile Strength Test (STS) were conducted on 39 different combinations of FA, LS, CL, and G. Using these metrics, we were able to determine that two composites stabilized with 12%CL and 1%G performed admirably: (optimum mix 2, 50%FA+50%LS) and (optimum mix 1,95%FA+5%LS). After 28 days of curing, the UCS for optimal mix 1 was 6.6 MPa, while for optimum mix 2 it was 5.8 MPa, and for STS it was 1.3 MPa, and for both mixes it was 1.1 MPa. After 28 days of curing, the optimal mix 1 had a soaked CBR value of 75% and an unsoaked value of 89%. When optimal mix 2 was cured for 28 days, the CBR values were 91% for the unsoaked condition and 82% for the soaked condition. When tested for durability according to both British and American standards, both composites passed with flying colors. For instance, following twelve cycles of wetting and drying, mix 2 samples lost 1.05% of their initial weight while mix 1 samples only lost 1.12% of their initial weight, both of which were well within the criteria that were recommended. Also, after 28 days of curing, the composites had almost little heavy metal content leaching out. Additionally, scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to study the development of cementitious compounds during curing. Having said that, the stabilized composites exhibited brittleness. The ductility and strength were examined after adding fibers to these composites in an effort to reduce their brittleness. The results of the trials with the various fiber percentages showed that adding 0.3% of fiber to both composites increased the mix's strength and ductility. The strength index and deformability index were used to measure the improvement in ductility and strength, respectively. There is an 80% increase in failure strain and a 40% increase in strength when fibers are added. The findings indicated that using Composites have achieved the necessary strength, durability, and ductility to be used as base course layer materials in flexible pavements. Furthermore, it is recommended that the total pavement thickness be decided upon based on dependability, taking into account the uncertainty in the input data such as the design traffic load (measured in Million Standard Axle, MSA) and soil carrying capacity (measured in CBR value). In order to determine the total thickness of the flexible pavement that can guarantee a specific degree of dependability in the pavement's performance, design charts were produced, taking into account the uncertainty in the input data. In addition, the reliability-based technique—which combines the Mechanistic- Empirical approach with Monte Carlo Simulation (MCS) and the First Order Reliability Method—was used to study the uncertainties in distress analysis of flexible pavement, specifically with regard to fatigue and rutting failure. In order to determine the pavement's performance, the reliability index (β) was calculated and strain at crucial sites for fatigue and rutting failure was calculated using PLAXIS 2D coding software on a three-layered flexible pavement model. The specified strength, durability, and ductility requirements are met by the produced composites, namely Optimal Mix 1 [(95%FA+5%LS), 12% CL, 1% G and 0.3% F] and Optimal Mix 2 [(50%FA+50%LS), 12% CL, 1% G and 0.3% F]. The compressive strain value at the crucial point was found to be ɛc = 13.42 x 10-5 and the tensile strain value at the same region was found to be ɛt = 18.11 x 10-5 for a 450 mm thick foundation of optimal mix 2. For 10 MSA of design traffic load, the pavement performed admirably (βR and βF >5) according to the probabilistic based methodology. However, when subjected to larger traffic loads, the pavement exhibited above-average performance in terms of fatigue and rutting.
