http://localhost:8080/xmlui/handle/123456789/104 2026-04-26T08:51:37Z http://localhost:8080/xmlui/handle/123456789/3510 Title: INVESTIGATIONS ON FLEXURAL RESPONSE OF FRC BEAMS REINFORCED WITH BASALT FIBER REINFORCED POLYMER REBARS Authors: SAGAR, BHANAVATH Abstract: Investigations on the flexural response of fiber reinforced concrete (FRC) beams reinforced with basalt fiber reinforced polymer (BFRP) rebars are presented. The development of durability related issues in traditional steel reinforced concrete (RC) structures due to embedded steel reinforcement corrosion is the biggest problem that is causing the shortening of service life of the steel RC structures. Reinforcing the concrete structures using non-metallic and non corrosive fiber reinforced polymer (FRP) rebars will ensure that the structure remains corrosion-free. BFRP rebar is a newly developed FRP rebar that is emerging as a green construction material, and it has become one of the best alternatives to existing FRP rebars. All FRP rebars have a lower Young’s modulus and higher tensile strength than steel reinforcing bars. As a result, FRP reinforced plain concrete beams become less ductile, experience more deflections, and produce more cracks at higher flexural strengths. The flexural behaviour of steel or FRP RC beams not only depends on the area and type of reinforcement provided but also on the properties of the concrete used. The application of BFRP rebars in FRC can increase its performance as a longitudinal reinforcement, as the drawbacks associated with plain concrete (PC) beams reinforced with BFRP rebars can be decreased by increasing the strength and tensile properties of concrete with the addition of fibers. In this study, an attempt was made to develop an eco-friendly reinforcing system (BFRP rebars + basalt fibers and/or polyvinyl alcohol (PVA) fibers) to investigate the flexural response of BFRP reinforced basalt fiber reinforced concrete (BFRC) and PVA fiber reinforced concrete (PVAFRC) beams. Therefore, the present study was aimed to investigate the flexural response of PC, BFRC and PVAFRC beams reinforced with BFRP rebars. This investigation was carried out using two concrete grades: normal strength concrete (NSC) of M30 grade and high strength concrete (HSC) of M70 grade. The use of pozzolanic materials in concrete manufacturing provides economical, technological, and environmental benefits. In this study, alccofine-1203 and fly ash were used as supplementary cementitious materials (SCMs) to partially replace cement in the development of HSC. 4%, 6%, 8%, 10%, 12% and 14% alccofine-1203 with 20% fly ash combination were used to partially replace cement to find the optimum percentage of alccofine-1203 to be used in the development of HSC. For this, a total of seven binder proportions were prepared and evaluated for mechanical properties, microstructural characteristics and compressive stress strain behavior. From the obtained results, it was found that the use of alccofine-1203 in combination with fly ash was beneficial in the development of HSC. Among all, the i replacement of cement with 10% alccofine-1203 with a 20% fly ash combination attributed superior microstructural characteristics for binder mixes and showed highest mechanical properties and compressive stress-strain behaviour for the concrete. In this study, to improve the flexural performance of BFRP RC beams, BFRC was developed using basalt fibers and PVAFRC was developed using PVA fibers. To determine the optimum percentage of basalt fibers and PVA fibers to use for manufacturing BFRC and PVAFRC, additions of 0.1%, 0.2%, 0.3%, 0.4%, and 0.5% (of the volume of concrete) basalt fibers and PVA fibers were made to the developed NSC and HSC. Consequently, a total of 20 mixes (10 BFRC mixes and 10 PVAFRC mixes) were developed and evaluated for fresh and hardened properties. The workability, compressive strength, flexural strength, split tensile strength, load deflection behaviour, and uniaxial compressive stress-strain behaviour of BFRCs and PVAFRCs were studied experimentally. Young’s modulus, and energy absorption capacity, peak-stress, and strain at peak-stress of BFRCs and PVAFRCs have also been studied analytically. Scanning electron microscopy analysis was performed to examine microstructural characteristics of BFRCs and PVAFRCs. The results indicated that the addition of basalt or PVA fibers reduced the workability of concrete mixes. The maximum compressive strength, flexural strength, split tensile strength and better load-deflection and stress-strain behaviour were obtained with the addition of 0.3% of basalt fibers in two strengths of BFRCs and 0.3% PVA fibers in two strengths of PVAFRCs. The modified constitutive analytical model and relationships between properties of compressive stress-strain curves of BFRCs and PVAFCs such as peak-stress, strain at peak stress and material parameter (𝛽𝑛) with modified reinforcing index values of fibbers were proposed for analytical modelling of stress-strain curves of BFRCs and PVAFRCs of two strengths, and a good agreement with experimental results was observed. Additionally, in the literature, the proposed constitutive analytical model and relationships between the material parameter and reinforcing index for analytical modelling of FRC’s stress strain curves failed to accurately predict the experimental stress-strain curves of BFRCs and PVAFRCs. To test the flexural response of BFRP RC (PC, BFRC, and PVAFRC) beams, 16 single reinforced concrete beams with a pure bending region were cast and tested experimentally. Twelve beams were longitudinally reinforced with BFRP rebars in the tension region and four beams were fully reinforced with steel reinforcing bars. Two grades of concrete- NSC and HSC; two types of FRC- BFRC and PVAFRC; and two types of RC sections- under-reinforced and over-reinforced were parameters considered in the investigation. All the beams were tested for ii load-deflection behaviour, moment-curvature relationships, ductility, cracking pattern and failure mode evaluation. The optimum percentage of basalt fibbers and PVA fibers (0.3%) was taken to prepare BFRC and PVAFRC. The obtained results showed that the load-deflection and moment-curvature response of BFRP-reinforced PC, BFRC, and PVAFRC beams exhibited two phases which bounded the cracking point, whereas steel-reinforced PC beams exhibited three phases which bound the cracking and yielding points. Although BFRP rebar is a brittle material with no clear yielding point, BFRP RC beams exhibited more deformation and curvature prior to failure during testing. The amount of deflection, curvature, stiffness and ductility that were exhibited by BFRP-reinforced PC beams were partially countered by reinforcing PC with basalt fibers and PVA fibers. However, due to the higher bond strength and better strain softening behaviour, PVA fibers improved flexural behaviour of BFRP RC beam better than the basalt fibers. ABAQUS based non-linear finite element numerical modelling was conducted to validate the experimental results of BFRP-reinforced PC, BFRC, and PVAFRC beams. The investigation parameters considered in experimental evaluation were the same as those considered in numerical modelling. All the numerically modelled beams were evaluated for load-deflection behaviour, moment-curvature response, ductility and damage pattern. The results showed that the numerical modelled beams behaved similar to the experimentally tested beams. The percentage of error between experimental and numerical results was found within 10%. This shows good agreement between them. The numerically modelled beams accurately illustrated concrete damage in compression and tension, as well as a cracking pattern in tension, in a manner similar to that of the experimental cracking and the damage patterns of concrete in compression and tension. iii Description: NITW 2023-01-01T00:00:00Z http://localhost:8080/xmlui/handle/123456789/3480 Title: AN EXPERIMENTAL INVESTIGATION ON THE ENGINEERING BEHAVIOUR OF CHEMICALLY STABILISED EXPANSIVE SOILS Authors: Ramanjaneya Raju, E. Abstract: Expansive soils are popularly known in India as black cotton soils. They have an inherent nature to experience changes in volume depending upon changes in water content. Hence, they heave or increase in their volume when they absorb water in rainy seasons and shrink or decrease in their volume when they lose water on evaporation in summer seasons. This propensity of expansive soils to respond to changes in water content makes them highly problematic. Owing to this alternate swelling and shrinkage, lightly loaded infrastructure like residential buildings, canal linings and pavements constructed upon them are damaged. Structural members such as flooring, walls and columns develop severe cracking. Diagonal tension cracks are observed above doors and windows and below window-sills in the case of lightly loaded buildings. To control these volume expansions and volume reductions of these soils, innovative foundation techniques have been invented. The broad classification of these techniques is as follows: i) mechanical modification (Sand cushion and CNS layer), ii) physical modification, iii) chemical modification and iv) foundations counteracting tension. In mechanical modification, the top few layers of the expansive clay layer are removed and replaced by layers of non-expansive material such as sand and gravel. Sand cushion is a classic example of mechanical modification. Cohesive non-swelling (CNS) layer technique is another example of mechanical modification. In physical modification, the top layers of the soil stratum are excavated, pulverised and mixed with non-expansive materials like sands and gravels and compacted back in layers. As the soil layers are replaced by non-swelling materials, swelling is reduced. Foundations counteracting tension are special foundation techniques. The examples are under reamed piles, large-bottomed piers or belled piers, straight-shafted piers or drilled piers, and granular pile-anchors (GPAs). The swelling pressure of the soil causes the uplift force on these foundations. And skin friction causes the force resisting this uplift. Granular pile-anchors (GPAs) are a recent innovation over conventional granular piles. In a GPA, an anchor is created for the foundation using a mild steel anchor rod and a mild steel anchor plate placed at the bottom of the granular pile. When the expansive clay bed swells by imbibing water, swelling pressure uplifts the foundation. But, the anchorage in the GPA develops resistance to this uplift which is mobilised over the cylindrical GPA-clay interface. The resistance mobilised acts in the downward direction; and this resistance can be attributed to the weight of the GPA and the GPA-clay interface shear parameters, namely, c’ and φ’. In chemical modification, various chemicals and industrial byproducts such as lime, silica fume (SF), fly ash (FA), cement, rice husk ash (RHA), pond ash (PA), calcium chloride (CaCl2) and GGBS are added to expansive clay for controlling their volume changes, reducing their plasticity and improving their engineering behaviour. Chemical stabilisation of expansive clays basically works through flocculation and cementation which are the two important reactions of which one is an immediate reaction and the other is a time-bound reaction. Flocculation reduces plasticity and swelling. And cementation causes cementitious products which harden the blends. This thesis is a focused research on chemical stabilisation of a remoulded expansive clay. Lime, cement, fly ash and GGBS were used as the additives to the clay. Free swell index (FSI), liquid limit (LL), plastic limit (PL) and plasticity index (PI) were the index properties determined at varied amounts of the above additives. Compaction characteristics, hydraulic conductivity, unconfined compressive strength corresponding to varied curing periods and soaked CBR were the engineering properties studied. Further, to study the load-settlement characteristics, plate load tests were performed on clay beds stabilised with varied amounts of the above additives. Moreover, in another series of tests, the plain clay bed and the clay beds stabilised with 6% lime, 20% cement, 20% fly ash and 20% GGBS were subjected to five swell-shrink cycles. In each of the swell-shrink cycles, swelling was observed for 10 days and shrinkage was observed for 50 days. Thus, each clay bed was continuously monitored for 300 days for swelling and shrinkage. Furthermore, shrinkage/desiccation cracks developed in the untreated and the treated clay specimens were quantified by image analysis to determine the crack area, the crack density factor and the crack intensity factor. Description: NITW 2024-01-01T00:00:00Z http://localhost:8080/xmlui/handle/123456789/3479 Title: ASSESSMENT OF RAIL TRANSPORT NOISE PERCEIVED BY TRACKSIDE DWELLERS Authors: SUDHIR KUMAR, BODDU Abstract: Unplanned urbanization has led to the settlement of migrants from rural areas close to railway lines, exposing them to the continuous noise levels from the moving trains. These high, intense noise levels annoy and adversely affect the health of individuals living near railway lines. Every ambient noise study employs the source-path-receiver structure to explore the overall behavior of sound. Therefore, noise control techniques are necessary to modify the noise source mechanism, transmission path characteristics, and receiver perception. Among these techniques, eliminating railway noise at the source is the most effective method for mitigating noise. This study evaluated different train types, including various speeds and lengths, to determine their correlation with noise levels. Results showed that train speed had the strongest correlation with noise levels, the driving factor for maximum noise levels. When the train speed increases by 10 km/h, noise levels rise by 2.8 to 3 dBA. In the case of freight trains, the train length is a key parameter in the emission of railway noise when compared to passenger trains. The study also identified the type of trains with the highest noise levels, and a detailed examination of the mechanism responsible for this phenomenon was carried out. Multiple linear regression models for maximum and equivalent noise levels were developed for passenger and freight trains. In addition to source parameters, the current study evaluates a noise pollution hotspot: a railway-level crossing, where several activities related to transportation noise were involved. Train honking, train movement, road vehicles, and pedestrians contribute to the noise level at a railway-level crossing. Train horns are generally blown as trains approach railway level crossings and are mandatorily used to alert road users. However, the train horns are considered a nuisance to the nearby residents. A comprehensive noise monitoring survey was conducted at an access-controlled level crossing. Further, an Artificial Neural Network (ANN) based railway noise prediction model was developed to forecast maximum (Lmax) and equivalent (Leq) noise levels. Results revealed that train horns produced impulsive sound signals that fall under high-frequency one-third octave bands, causing severe irritation to trackside inhabitants. Noise levels are affected by changes in distance, intervening barriers, and atmospheric conditions along the transmission path between the source and the receiver. This study explored the variance of railway noise in an urban setting over various measuring distances, including 25, 50, 100, and 200 m, with variables such as air temperature, humidity, and wind conditions. Results showed that the effect of the wind was more significant for larger distances between the source and the receiver. For every 1 m/s increase in wind speed within a distance of 50 m, the average sound attenuation induced by the upwind phenomena was 0.2 dBA. The impact of air temperature changes on received xx sound level from a moving source was insignificant within the range of temperatures considered in the study. The effect of humidity was observed to be less at shorter distances but at larger distances, increasingly attenuates noise levels. Along the transmission path, the presence of a wall between the source and receiver can act as a noise barrier resulting in a reduction in intensity of noise. In urban areas, railway boundary walls are constructed to prevent encroachments of railway lands and to avoid pedestrians trespassing the railway tracks. This study aims to evaluate the effectiveness of such a boundary wall in reducing noise and proposes an improved alternative through Computational Fluid Dynamics (CFD) simulations. Various noise barriers with different geometry, shape, and surface materials were simulated and verified through field study measurements. Noise attenuation was evaluated by measuring railway noise spectra at different positions, including 0.5 m in front and behind the barrier and at the facade of the residential area. Results showed that as barrier height increased, insertion loss also increased, with a maximum attenuation of 17 dBA achieved with a rectangular barrier of height 6 m. The most effective noise barrier for reducing railway noise was a T-shaped barrier with a height of 6 m and a projection length of 2 m, with an insertion loss of 22 dBA. This study recommends constructing the barrier with soft materials on its surface to reflect and absorb sound waves effectively. In the last phase of this study, the impact of railway noise on the residents living along the railway line at several distances was assessed by measuring the noise inside houses. Additionally, a human perception survey was conducted to investigate the relationship between noise levels and annoyance during daily activities such as working, resting, conversing, eating, talking on the phone, and reading. Structural Equation Models (SEM) were employed to analyze the complex relationships between annoyance, disturbance, and health effects. The outcomes of this study reveal that both passenger and freight trains exceeded the permissible noise limits, with an excess of 36.8% and 15% during daytime and 75.15% and 41.8% during nighttime, respectively. The primary factors contributing to annoyance were identified as the source type and location of noise exposure. The annoyance levels associated with the time of noise exposure negatively impacted disturbances to daily activities and subsequent health effects. This phenomenon suggests a psychological adaptation known as habituation, where residents along railway lines gradually become accustomed to the noise over time. Furthermore, the cumulative impact of disturbances to daily activities can indirectly influence long-term health. Proximity to the railway line amplifies the relationship between annoyance and health effects. Description: NITW 2024-01-01T00:00:00Z http://localhost:8080/xmlui/handle/123456789/3478 Title: BEHAVIOUR OF PESTICIDES IN AGRICULTURAL SOILS: ASSESSMENT AND BIOCHAR-BASED CONTROL APPROACH Authors: MAJEE, PRASANTA Abstract: The World Health Organization defines pesticides as chemical substances used to prevent, destroy, or mitigate pests, including vectors of disease and unwanted species harmful to food production and other commodities. While pesticides are crucial in modern agriculture for protecting crops and enhancing food production, their overuse can harm human health, the environment, and non-target species. Pesticide use raises environmental risks, especially regarding groundwater and surface water contamination. This necessitates a thorough understanding of pesticide behaviour in agricultural lands to address human health and environmental sustainability. Sorption characteristics of organic chemicals vary with location, influenced by factors like clay content, organic matter, and microbial presence. Understanding these characteristics is vital for developing effective remediation measures and pesticide management strategies. In the specific context of Telangana state, where pesticide usage has increased dramatically in recent years, there is a heightened risk of groundwater contamination with persistent organic pollutants. Imidacloprid and Atrazine are the two majorly used pesticides in this region. Therefore, this research aims to investigate the sorption, desorption, and leachability of widely used pesticides in the black cotton soils and red soil of the Telangana region. The objective is to provide a comprehensive assessment of the potential risks associated with groundwater pollution from these pesticides, offering valuable insights for tailored environmental management. Additionally, the study seeks to explore the efficacy of biochar derived from locally available cotton stalks in enhancing pesticide sorption. This aspect of the research is essential for developing targeted remedial measures against pesticide pollution and implementing effective pesticide management practices specifically tailored to the unique characteristics of the Telangana region. By shedding light on the sorption, desorption, and leaching behaviour of Imidacloprid and Atrazine, this research aims to empower policymakers with the knowledge necessary to formulate targeted strategies for environmental conservation and sustainable agricultural practices, thereby ensuring a harmonious balance between agricultural productivity and environmental preservation. vii The first phase of the study assesses the sorption desorption behaviour of insecticide Imidacloprid and herbicide Atrazine in four different agricultural soils (BC-1, BC-2, BC-3, RS) of Telangana region. The study reported that both the pesticides were weakly sorbed on the investigated soils. The sorption kinetics for both the pesticides were observed to occur in two stages- the quick initial adsorption stage, where 90% of the pesticide’s adsorption capacity reached within first few hours due to the rapid filling of empty spaces in soil particles, and the slow equilibrium stage. Pseudo second order kinetic model demonstrated the best fit to the experimental data. Analysis of isotherm models indicated that the Freundlich isotherm model provided the best fit compared to Langmuir or Temkin isotherm models. Among the soil samples, BC-2 soil exhibited the highest Freundlich coefficient value (Kf), followed by BC-3, BC-1, and red soil. A strong positive correlation (r>0.9) was observed between clay content and the Kf value, indicating that clay content significantly influences Imidacloprid adsorption to the soil. Interestingly, despite having a higher organic carbon content (0.57%), red soil showed a lower affinity for Imidacloprid compared to other soils, possibly due to the relatively low quantity of organic carbon present. Both temperature and pH exert significant influences on the sorption behaviour of Imidacloprid in the examined soils. As temperature rises, the sorption of Imidacloprid decreases, possibly due to increased solubility at higher temperatures. Additionally, lower pH levels demonstrate favourable conditions for sorption, as they facilitate the protonation of the solution, thereby increasing the cationic charge of the pesticide molecules. The second phase of the study focused on the degradation of Imidacloprid and Atrazine in soil to assess their persistence. The study reported that the half-life of Imidacloprid ranged from 67 to 83 days in the investigated soils, whereas the half-life of Atrazine ranged from 44 to 57 days. Imidacloprid showed greater persistence in the investigated soils compared to Atrazine. The Groundwater Ubiquity Score (GUS) index is employed to evaluate the leachability of pesticides in the soils under investigation. This screening method utilizes the KOC value and half-life (T1/2, days) of pesticides to assess the probability of groundwater contamination. The GUS values for Imidacloprid ranged from 2.25 to 2.62 in black cotton soils, while in red soil, it was reported as 3.72. For Atrazine, GUS values ranged from 2.01 to 2.41 in black cotton soils, and in red soil, it was 3.16. GUS values falling between 1.8 and 2.8 in all black cotton soils suggest that both pesticides fall into the potentially mobile category. However, in red soil, where the values exceeded 2.8 for both pesticides, they are considered highly mobile. The results of the soil column leaching study corroborated these findings, as both Imidacloprid and Atrazine were viii detected in the leachate sample and migrated to the deeper sections of the column. The presence of pesticides in the deeper layer of the soil matrix could make the pesticides more persistent due to the absence of microorganisms, ultimately leading to groundwater contamination. The final phase of the study investigated the efficacy of cotton stalk biochar as soil amendments to improve pesticide sorption capacity in soils and reduce the mobility. The results indicate that the introduction of 0.5% and 1% cotton biochar (CBC) into the soil significantly enhanced the Kf values of Imidacloprid and Atrazine sorption across all the examined soils. The improved sorption capacity is a direct outcome of the augmented surface area and additional sorption sites resulting from the addition of CBC to the soil. Pesticide degradation study in biochar amended soils revealed that the addition of biochar to the soil had a slight effect on the half-life of Imidacloprid and Atrazine, with all cases showing a modest increase. With the incorporation of biochar, GUS values notably declined, falling below the threshold of 1.8 suggests a significant reduction in the mobility of both Imidacloprid and Atrazine within the investigated soils. The soil column leaching study revealed that biochar amended soil can retain pesticides in the top layers of the soil matrix for both Imidacloprid and Atrazine. Overall, it can be concluded from the findings of the present study that the sorption capacity of both Imidacloprid and Atrazine was notably low in all three black cotton soils and red soil. Clay content, temperature and pH was identified as the primary factor influencing pesticide sorption, while soil organic matter showed a negative correlation with the sorption coefficient due to its limited availability in the soil. Imidacloprid's prolonged half-life compared to Atrazine indicates its greater persistence in all investigated soils. The calculated GUS value categorized both Atrazine and Imidacloprid as falling within the highly mobile to mobile category, highlighting the region’s vulnerability to groundwater contamination from pesticides. The study underscored the high susceptibility of groundwater in this specific area of the Telangana region to contamination, emphasizing the urgent need for proactive measures to prevent potential catastrophes. The incorporation of cotton stalk biochar into the soils emerged as a promising strategy to mitigate the leaching potential of both pesticides, offering a potential solution to reduce environmental risks associated with pesticide use. Description: NITW 2024-01-01T00:00:00Z