2. Thesis and Dissertations
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Item Sustainable Production of Fly Ash Based Coarse Aggregates and its Performance in Concrete(National Institute of Technology Karnataka, Surathkal, 2020) Shivaprasad, K. N.; Das, Bibhuti Bhusan.An optimization study was carried out for the sustainable production of fly ash based coarse aggregates from the industrial by-products such as fly ash, considering the combined effect of geopolymerisation and pelletization. The trial mixes during the process of producing the fly ash based coarse aggregates were designed through Taguchi’s experimental design method. The combined effect of geopolymerisation and pelletization factors in the production process and engineering properties of the produced fly ash based coarse aggregates were evaluated using response indices at different curing ages. Further, the influence of each individual factor of geopolymerisation and pelletization on the engineering properties was determined through Grey relational analysis to identify the most influencing factors in the production of fly ash based coarse aggregates. The results obtained from Grey relational analysis indicate that the properties of produced fly ash aggregates are governed mostly by geopolymerisation. It is also observed that water content of 20 % by mass of fly ash found to be essential for the suitable production of fly ash based coarse aggregates. Artificially produced fly ash aggregate were used in the production of concrete with partial replacement of natural aggregates and it is found that for the production of M40 grade durable concrete, up to 30% by its volume can be replaced effectively.Item Determination of Engineering Properties of Steel-Concrete Interface of Reinforced Concrete Exposed to Marine Environment(National Institute of Technology Karnataka, Surathkal, 2020) Kumar, Sharan; Das, Bibhuti Bhusan.; Arya, Shashi Bhushan.In this investigation, engineering properties of steel-concrete interface (SCI) such as porous zone thickness and calcium hydroxide content around the reinforcing steel were studied through the measurement of ultimate bond strength and also by employing advance characterization techniques such as scanning electron microscopy (SEM) powered with energy dispersive spectroscopy (EDS) and nano-indentation. Three types of cements, i.e., ordinary Portland cement (OPC), Portland pozzolana cement (PPC), and Portland slag cement (PSC) were used in this study and their influence towards the SCI properties was determined. A reliable grayscale-based thresholding technique was used to determine the porous zone thickness at SCI. The nano mechanical properties of concrete such as hardness and modulus of elasticity around the SCI were analysed using nano-indentation technique. Also, the effect of marine environment exposure on ultimate bond strength and porous zone thickness of SCI was investigated. A detailed sample preparation technique for scanning electron microscopy (SEM) studies is proposed and ensured for a minimal damage to the SCI properties as compared to the methods adopted by the earlier researchers. It is to be noted that engineering properties of SCI were found to be quite influenced by the curing period. There found to be a reduction in mean porous zone thickness because of a prolonged curing period. Nano-indentation analysis revealed that average hardness and modulus of elasticity values around SCI were 0.8 GPa and 30 GPa, respectively. It is also observed that exposure of reinforced concrete (RC) samples to marine environment till the age of 180-days increased the bond strength. The microstructure study revealed that corrosion products penetrated the porous zone between steel and concrete and increased friction during pull out test which resulted in increased bond strength. However, RC samples exposed to marine environment for a longer period of 720-days induced severe corrosion and the ultimate bond strength between steel and concrete found to be reduced significantly. This can be attributed to the fact that corrosion products filled the porous zone completely and the expansive pressure in the concrete induced cracking that resulted in the reduction in ultimate bond strength between steel and concrete.Item Evaluation of Graphene Oxide and Reduced Graphene Oxide for the Removal of Selected Halogenated Phenols from Water(National Institute of Technology Karnataka, Surathkal, 2020) Catherine, S Hepsiba Niruba.; Manu, BasavarajuCarbon-based materials especially graphene nanocomposites (GNS) have attracted wide attention in recent years. In this study, graphene oxide (GO) and reduced graphene oxide (rGO) were prepared by Improved Hummers method having high suspension stability in water. Both GO and rGO were investigated for the adsorption of halogenated compounds from water, its stability at the GNS-water interface and its effective application in the debromination of brominated flame retardant. Emerging contaminants (ECs) are compounds of emerging concern that are of raising concern in the past 20 years. ECs such as bisphenol A (BPA), 4-nonylphenol (4-NP) and tetrabromobisphenol A (TBBPA) pose threat to both humans and the ecosystem. GNS including GO and rGO are also considered as EC due to its potential hazard. The adsorption of organic contaminants such as the phenolic ECs on GNS affects the stability at the GNS-water interface and the fate of organic contaminants, thus causing further environmental risk. Various spectroscopic tools such as SEM, TEM, XRD, Raman, FTIR, and XPS were used to characterize the nanomaterial synthesized. The obtained results confirmed that the size of GO and rGO were with a surface area of 2.02 and 227.32 m2/g. The XRD analysis shows that the values of diffraction peak 2θ were 10.01 and 26.09 confining to the synthesized GO and rGO. Later both GO and rGO were used to study the adsorption behaviour of some ECs and common phenolic compounds that include 4-chlorophenol, 2,4-dichlorophenol, 2,4,6– trichlorophenol and phenol considering its stability in water interface were studied. The adsorption capacity of GNS with phenol, TBBPA, and BPA was examined for its thermodynamic equilibrium at different temperatures. The adsorption equilibrium was reached less than 10 h and was fitted using both Langmuir and Freundlich isotherms. The kinetics and isotherms models of the sorption of aromatic compounds on GNS were investigated at ambient conditions. It was also demonstrated that GO and rGO that varied in C/O ratio is identified as an efficient approach for debromination of TBBPA. A pathway of TBBPA, tri-BBPA, di-BBPA, mono-BBPA, and BPA was thus proposed for TBBPA degradation. Debromination was observed by using metal-free carbon-based nanomaterial. The structural defects of GBMs, act as active sites responsible for catalytic performance. Furthermore, ESR analysis provided insights into the evolution of reactive oxygen species (ROS) such as superoxide radical (O⁻ ₂•) and singlet oxygen (1O2) during the debrominationprocess. Therefore, these active species were identified to be the primary radicles generated onto the surface of GBMs, which results in the formation of less brominated BPA. Finally, reuse of the adsorbents for all the pollutants were investigated, and we observed that adsorbent reusability was >93% of its activity up to 5 cycles. These novel findings unveil the crucial role of oxygen functional groups on GBMs surface for the catalytic degradation of TBBPA. These findings emphasize that when carbon-based materials are used for sorption studies of halogenated compounds more attention should be considered on estimating the adsorption capacity in addition to the degradation.Item Project Performance Assessment Using Modified Project Quarterback Rating System for Indian construction projects(National Institute of Technology Karnataka, Surathkal, 2020) Ingle, Prachi Vinod.; Mahesh, Gangadhar.The Indian construction industry is facing challenges due to performance shortfalls. Construction projects are highly complex, distinctive, fragmented and do not have well-established performance assessment models to evaluate their project success. This study has focuses on developing a mathematical formulation of construction project performance assessment to suit Indian context by modifying the original PQR model. The original PQR model combines seven performance areas. Though previous studies have identified performance areas that can be used to assess the performance of construction projects, those areas are not comprehensive in indicating overall performance. In addition, major research work is from contractor‟s perspective. Hence, there is a need to contextualize the performance areas that contribute towards the Indian construction industry. To indicate the modification the word modified Project quarterback rating (MPQR) is adopted. MPQR model‟s output is a project score based on performance areas affecting project success and outcome. The objectives set include identifying performance areas for Indian construction industry, integrating all performance areas in MPQR model and validating the MPQR model. The modified model comprises of ten performance areas and twenty-eight performance metrics related to project performance. The study used a mixed method research approach in data collection. The quantitative approach used survey questionnaires and case studies were used to obtain qualitative data from construction projects in India. Partial Least Square Structural Equation Modeling (PLS-SEM) technique was used in analyzing and establishing the relationship between the constructs. The PLS- SEM results show that all performance areas have a significant impact on project performance except productivity which was found to be insignificant. Even though the result shows productivity has no significant impact on performance it impacts construction time and cost overruns, and therefore it should not be ignored. Furthermore, the findings provide that customer relation, safety, schedule, cost, quality, finance, communication and collaboration, environment, productivity and stakeholder satisfaction are impacting project performance. It also emerged that all ten performance areas are important formeasuring project success for Indian construction industry. Case studies also supported this finding. The MPQR model is a comprehensive single score approach that can be utilized to compare performance over different projects. The identification of performance areas can help project management teams to better coordinate projects by analyzing the importance of performance areas. The findings of the study will guide project stakeholders to prioritize their efforts towards achieving excellence in performance.Item Experimental Studies on High Performance Alkali Activated Slag Concrete Mixes(National Institute of Technology Karnataka, Surathkal, 2020) Manjunath R.; Narasimhan, Mattur C.In the present study, an attempt has been made to develop high-performance alkaliactivated slag concrete (HPAASC) mixes. A total of fifteen self-compacting concrete mixes were developed based on absolute volume method, with Ground Granulated Blast Furnace Slag (GGBFS) as the principal binder with their compressive strength values targeted to be greater than 70 MPa. A Control, reference OPC-based concrete mix was also developed with similar flow ability and compressive strength values. Further the initial setting times of these mixes were also investigated as per relevant IS: 8142-1976. These concrete mixes incorporated slag sand and Electric arc furnace (EAF) slag, as fine and coarse aggregates respectively. In the background of application of Taguchi’s DOE method, the flow and strength properties of nine of these mixes were evaluated in an initial calibration phase and the performances of the remaining six mixes were analyzed in the validation phase. After ascertaining the self-compacting nature of the mixes, their mechanical strength properties such as compressive, split tensile and flexural strengths, water absorption and moduli of elasticity were evaluated. Regression equations were developed for the different strength characteristics and predictive capabilities of those regression equations were found to be good. Detailed microstructural studies were carried out on all the fifteen mixes using SEM, EDX and XRD. In the second phase of the present investigation, five (of the fifteen above) best performing candidate mixes, in terms of their better flow ability and higher mechanical strengths were subjected to various durability tests in order to assess their resistances on exposure to aggressive chemical environments. Tests were conducted in acid and sulphate-rich environments upto to an extended period of 365 days. Further these five mixes were evaluated for their chloride ion penetration by conducting steady and nonsteady state tests. The same five mixes were further evaluated for their strength characteristics on exposure to sustained elevated temperatures upto 800ºC. Microstructural studies were also carried out on the test specimens of different mixes after them being exposed to aggressive acid and sulphate-rich environments and so also to elevated temperatures using SEM and EDX.In order to enhance the toughness characteristics of these mixes, appropriate percentages of steel fiber were added and the flow ability and strength characteristics of such fiber-reinforced mixes were evaluated. Such mixes were evaluated for their enhanced toughness characteristics based on methods proposed by Barr and Hasso and ACI. The high performance self-compacting alkali-activated slag concrete mixes (HPAASC) mixes were further evaluated by testing the flexural behaviour of beams made of such mixes and reinforced with steel-rebar reinforcement, in order to check their applicability in structural concrete elements. A detailed analysis with respect to the sustainability in terms of ecological performance, of all these concrete mixes is also carried out. A new class of high strength, self-compacting, alkali-activated slag concrete mixes were successfully developed herein, incorporating slag sand and Electric arc furnace slag, both by-products from the iron and steel industry, as fine and coarse aggregates respectively. Addition of small amounts of sodium phosphate, as an additive, has led to a construction-friendly increase in the initial setting times of all the HSAASC mixes tested herein, from an initial-low of 15 minutes to a healthy 60 minutes or so. These mixes developed herein have shown higher mechanical strength properties in terms of compressive, split tensile sand flexural strengths and so also greater modulus of elasticity, and lower water absorption characteristics, possibly due to the formation of more amounts of C-A-S-H gels, as reflected from the morphologies obtained during the microstructural analysis. HSAASC mixes developed herein have also shown better durability performances when subjected to acid, sulphates and chloride environments as compared to the control OPCC reference mix. Thus the present class of alkali activated slag concrete mixes are having the required levels of enhanced flow ability, higher mechanical strengths and better durability properties, and hence can be referred to as HIGH PERFORMANCE ALKALI ACTIVATED SLAG CONCRETE MIXES. Higher residual strength characteristics were also observed in all the HPAASC mixes developed herein, when subjected to sustained elevated temperatures as compared to the control OPCC mix. Addition of steel fibers to the high performancealkali activated slag concrete mixes has been shown to marginally increase the compressive strengths. The ultimate flexural strengths of all the candidate mixes, however, were observed to increase substantially. Increase in the percentage of steel fibers has shown to increase the toughness indices of all the candidate mixes tested herein. The flexural performance of all the reinforced HPAASC beams was found to be, in general, similar to that of the reference HSS-OPCC control beam. High performance alkali activated slag concrete mixes developed herein have shown lesser embodied energy as well as lesser emissions of embodied CO2 as compared to the control OPCC-based mix.Item Sequential anaerobic-aerobic treatment of herbicides in water(National Institute of Technology Karnataka, Surathkal, 2020) Mahesh, G. B.; Manu, BasavarajuHerbicides are toxic compounds which cause deterioration of the surface and ground water resources, cause harm to all living organisms. Various treatment methods like physicochemical and biological processes and in combination of aforementioned treatment techniques have been suggested for removal of pesticides from water. Under anaerobic reducing conditions, herbicides undergo dehalogenation, dechlorination and demethylation reactions and form substituent which can be further mineralized under aerobic conditions. Therefore, this study was conducted to evaluate the sequential anaerobic-aerobic treatment of three herbicides namely (2-ethylamino)- 4-(isopropylamino)-6-(methylthio)-s-trazine) (ametryn), 3,6-dichloro-2- methoxybenzoic acid (dicamba) and 2,4-dichlorophenoxyacetic acid (2,4-d), and their mixtures in different formulations. The performance was evaluated at hydraulic retention time (HRT) of 48 h, neutral pH between 6.5 – 7.5 and at ambient reactor liquid temperature (27 – 32.2oC). A preliminary study was conducted in four set of sequential anaerobic-aerobic system influent herbicides concentrations of 25 mg/L of 2,4-d, ametryn and dicamba separately and keeping one set as control. The preliminary study was conducted to evaluate the treatment potential of the reactors; significant removal efficiency was achieved for both the herbicides. The long term study was conducted using 4 anaerobic and aerobic reactors namely R1 (anaerobic control with no herbicide), R2 (anaerobic reactor fed with ametryn), R3 (anaerobic reactor fed with dicamba), R4 (anaerobic reactor fed with 2,4-d and ametryn mixture), and R5 (anaerobic reactor fed with 2,4-d ametryn and dicamba mixtures). Effects of increased herbicides concentration when they are treated separately (ametryn and dicamba), and in mixtures (2,4-d with ametryn and 2,4-d, ametryn with dicamba) during 400 – 430 days of treatment period. Five aerobic reactors were operated simultaneously to give post treatment to the anaerobic effluent. The reactors performance was evaluated by monitoring herbicide removal efficiency of ametryn, dicamba, chemical oxygen demand (COD) and biogas production. The reactors stability parameters pH, alkalinity, volatile fatty acids (VFA) and oxidation reduction potential (ORP) were monitored on daily basis. All the anaerobic reactors wereii stabilized using 2 g/L of starch with total organic loading rate (OLR) of 0.21 – 0.215 kg-COD/m3/d during 48 days, and aerobic reactors were stabilized in 14 days using anaerobic effluent as feed having OLR of 0.02 to 0.038 kg-COD/m3/d. After achieving the quasi-state condition the influent was fed with known herbicide concentrations to the respective anaerobic reactors. The maximum removal efficiency obtained for different influent herbicide concentrations under anaerobic treatment from R2 reactor was 88 – 100% for ametryn and 85 – 92% for COD, similarly from R3 about 68 – 80% for dicamba and 77 – 85% for COD respectively. Sequential anaerobic-aerobic removal efficiency was found to be greater than the efficiency of anaerobic reactor, complete removal of ametryn with COD >95% in A2, and >88% for dicamba and COD in A3 was achieved. The mixed herbicides removal efficiency was evaluated based on COD removal efficiency only, the overall COD removal efficiency achieved for different influent concentrations of herbicides mixture was >85%, and >88% respectively from A4 and A5 respectively. Addition of anthraquinone-2,6-disulphonate (AQS) as a redox mediator enhanced the herbicides removal efficiency in the anaerobic reactors R2 and R3 by 12 – 20%, and a slight improvement in the COD removal in the R3 and R4 reactors by 5 – 10%. The GCHRMS and LC-MS analysis was conducted to identify the transformation products (TPs) formed during the treatment process. Commonly identified TPs of anaerobic treatment include long chain fatty acids, esters, and alcohols from all the reactors, which were oxidised in the aerobic reactors and TPs of herbicides were different for the specific herbicides, ametryn TPs were biodegradable under anaerobic condition itself (in R2), while some TPs of dicamba were mineralised in aerobic post treatment step. The effluent from R4 – A4 and R5 – A5 contained different TPs which were not mineralised completely, but removed to a maximum level. Therefore, sequential anaerobic-aerobic treatment is found to be effective and efficient for the removal of selected herbicides from wastewater.Item Erosion Studies on Lithomargic Clays and Slope Stability Studies of Excavated Slopes in Lateritic Formations(National Institute of Technology Karnataka, Surathkal, 2020) Thomas, Biji Chinnamma.; Shivashankar, R.This study is done in three parts. In the first part, a brief study of the geology of the area is being made, especially that of laterites and lateritic soils. The study area is coastal Karnataka in India. This coastal area receives copious amount of rainfall and a lot of developmental activities are taking place. The soil stratification in lateritic areas consists of lithomargic clays, which are products of laterization, sandwiched between the hard and porous weathered laterite crust at the top and the hard parent rock of granite or granitic gneiss underneath. These lithomargic clays which are extensively used in construction purposes behave as dispersive soils and are found to be highly erosive. In the second part of this research work, erosion characteristics of lithomargic clays are being studied in detail since very few and detailed studies on erosion of lithomargic clays are available in literature. A number of hole erosion tests are conducted on controlled lithomargic clay samples with varying percentage of fines. The influence of degree of compaction, moulding water content, head causing flow, percentage silt content and plasticity index on the erosion rate index and critical shear stress of controlled lithomargic clay samples are being studied. The results of this study indicate that the critical shear stress for soils with higher silt fraction and fine sand content varied from 45 to 125N/m2 whereas for soils with higher clay fraction and fine sand content the critical shear stress varied from 200 to 400N/m2. The erosion rate increased with a decrease in percentage compaction in all the samples and critical shear stress is found to be highest at optimum moisture content conditions. It is generally observed that soils with fines whose plasticity indices are high, are less erodible compared to soils with fines whose plasticity indices are low. Excavated slopes for railway and highway projects in such lateritic formations are posing serious erosion and slope stability problems, especially, due to the presence of these lithomargic clays and seepage pressures from stagnated water at top. In the third part of this study, slope stability analyses of excavated slopes in lateritic formations is being conducted using the software Plaxis 2D. Slope stability analyses is actually a very complex problem which should take into consideration thecombined effect of geotechnical [berm position, height and slope of excavated slope, soil properties etc.], hydrological [precipitation, ponding at top and seepage through the slope etc.] and biological [vegetation (trees at various positions and turfing on slope), wind action on trees etc.] factors in addition to erosion (both surface and internal) problems. In this research work, the influences of these various factors on slope stability are being studied separately. Some of these factors have a positive influence by increasing the factor of safety of slopes, whilst others have a negative influence. When trees are provided at the toe of the slope a percentage increase in factor of safety up to 12% and 6% is observed for drained and undrained conditions respectively. When turfing along with trees are considered, a percentage increase of factor of safety up to 15% and 12% is observed for drained and undrained conditions respectively.Item Fenton’s Oxidation of Selective Herbicides in Water using Lateritic Iron extracted by Acidithiobacillus ferrooxidans BMSNITK17(National Institute of Technology Karnataka, Surathkal, 2020) Bhaskar S.; Manu, BasavarajuNeed for the effective, economical and eco-friendly treatment to degrade the persistent organic pollutants (POP’s) is essential in day to day life. Fenton’s oxidation is one of the proven technologies which have its vast application in the treatment of wide range of organic pollutants. Iron being a catalyst plays a key role demarcating its compulsion in the process. Use of commercial iron in this regard increases treatment cost. Many researchers have been carried out to replace commercial iron with natural laterite iron. Extraction of natural laterite iron by any chemical method again limits its application as its extraction adds up to the cost. Aiming at the replacement of catalytic iron in the Fenton’s oxidation process a detailed study of bioleaching of iron from laterite soil was carried out and the investigation of catalytic role of extracted laterite iron in the Fenton’s oxidation of selective herbicides was done. Novel bacterial strain was isolated and characterized at molecular level by gene sequencing technique and the sequence was submitted to Genbank to get an accession number. Isolated bacteria confirm to be an acidophilic chemolithotrophic bacterium Acidithiobacillus ferrooxidans belongs to the gamma proteo bacterial group with an accession number MG271840. Iron mineral biologically synthesized using isolated strain Acidithiobacillus ferrooxidans BMSNITK17 was characterized and confirms to be biogenic jarosite with XRD and EDS technique. This iron mineral was evaluated for its catalytic role in Fenton’s oxidation for the degradation of ametryn and dicamba. The fresh biogenic jarosite in Fenton’s oxidation was found to degrade ametryn by 84.90 % following alkylic oxidation and hydroxylation pathway which was confirmed with mass spectroscopy studies. Whereas the same mineral shows 91.29 % of dicamba degradation with Fenton’s oxidation process promising cost effective treatment. System conditions like pH, feed mineral particle size, pulp density, temperature, rotor speed has an effect on bioleaching potential of Acidithiobcillus ferrooxidans BMSNITK17 in leaching out iron from laterite soil. Very fast iron dissolution was observed with laterite and soon the drop in the iron concentration of leached solution. The drop in total iron concentration was due to the precipitation of leached iron. Thevi leaching conditions were optimized in the current study with respect to the native bacterial strain Acidithiobacillus ferrooxidans BMSNITK17. Maximum iron concentration leached out accounts to 281.0 mg/L under system conditions like pH 3.0, temperature 30 oC, pulp density 5%, shake flask speed 180 RPM and particle size 150 µm. The bioleached laterite iron (BLFe’s) on evaluation for its catalytic role in Fenton’s oxidation for the degradation of ametryn and dicamba exhibits 94.24 % of ametryn degradation and 92.45% of dicamba degradation efficiency. Fenton’s oxidation performed well with the acidic pH 3. The process follows pseudo first order reaction. Our findings suggest the application of biogenic iron mineral jarosite and bioleached laterite iron as a catalyst in the Fenton’s Oxidation process for treating hazardous herbicides which are the part of an agricultural runoff. The study marks the low cost treatment of hazardous pollutants using naturally available minerals.Item Potential Use of Processed Lateritic Fine Aggregates in Cement Mortars and Concretes for Sustainable Development(National Institute of Technology Karnataka, Surathkal, 2020) S. N., Basavana Gowda; Rajasekaran, C.; Yaragal, Subhash C.Availability of river sand is becoming scarce, due to rapid increase in infrastructure projects in India. Acute shortage of river sand, has led to indiscriminate sand mining. Adverse effect of sand mining includes river bank erosion, river bed degradation, loss of biodiversity and deterioration of river water quality and ground water availability. To address the above issues, research efforts are on, to find substitutes for river sand to be used as fine aggregate in mortars and concretes. One among the locally available resources is laterite. Laterite is a product of tropical or sub-tropical weathering, which is an abundant soil material available in many parts of India. An attempt has been made to characterize the processing technique to obtain good quality lateritic fine aggregates (lateritic FA). Experiments were designed and conducted to study the performance of lateritic FA as replacement to river sand, in cement mortars and concretes. Processed lateritic FA in replacement levels of 0, 25, 50, 75 and 100 wt.% to river sand at all fineness levels (Zone I to Zone IV as per Indian standards) is considered. The workability and compressive strength characteristics of cement mortars and concretes are evaluated. Laterized mortars with Zone III and Zone IV fine aggregates, at all replacement levels, result in the same compressive strengths as those of control mortars. Suitable strength enhancement technique has been attempted to achieve strengths of Zone I and Zone II lateritic fine aggregates based mortars at 100 wt.% replacement, to achieve strength at least equal to or more than those of control mortars. Laterized concretes have achieved nearly the same strengths as those of control concretes, at all replacement levels and for all fineness levels (Zone I to Zone IV). Microstructure studies were also conducted to understand the arrangement of river sand and lateritic FA with cement matrix and their Interfacial Transition Zones (ITZ) using Scanning Electron Microscope (SEM). In the second phase, performance evaluation of laterized mortars blended with GGBS and fly ash at elevated temperatures was studied. The study was carried out in three stages, in the first stage effect of elevated temperatures on laterized mortar with different proportions of fly ash and GGBS were evaluated with constant retention period and varying exposure temperature. In the second stage, the best performing laterized mixes with GGBS and fly ash were examined for different retention periods of 30, 60 and 90 minutes. The effect of retention period on the physical and mechanical properties are investigated. In the third stage, the effect of different cooling regimesii on the residual properties of laterized mortar specimens when subjected to elevated temperatures are assessed. In the present study, three cooling regimes namely furnace cooling, ambient air cooling and water quenching were adopted. Microstructure analysis of specimens subjected to different exposure temperatures was done through SEM image analysis using image J software. In the third phase, usage potential of recycled concrete aggregates (RCA) along with lateritic FA in concrete was studied. Mechanical properties of RCA based laterized concretes were examined. Suitable strength enhancement methodology is adopted to overcome the decrement in strength caused by the usage of RCA in concrete. Finally, sustainability in the production of concrete is achieved by using GGBS as sole binder and lateritic FA as fine aggregates and RCA as coarse aggregates along with alkali solution as an activator. The resultant alkali activated slag concrete with lateritic FA and RCA shows almost similar results in terms of mechanical properties when compared to control concrete.Item Experimental Study on Alkali Activated Slag Concrete Mixes by Incorporating PS Ball as Fine Aggregate(National Institute of Technology Karnataka, Surathkal, 2020) Talkeri, Avinash H.; Ravi Shankar, A. U.Improved road connectivity is essential for any country to progress. Well designed and constructed concrete pavements are essential for the development of sustainable highway infrastructure. The increase in infrastructure and urban development activities desire to discover sustainable materials, replacing the natural raw materials required for concrete production. The higher demand for concrete roads and other construction projects has increased Ordinary Portland Cement (OPC) production. However, cement production is associated with environmental issues such as a higher carbon footprint, highly energy-intensive, and exploitation of natural resources. Cement production uses a significant amount of natural resources. Nearly 2tonnes of raw material required to produce 1ton of cement, which emits 850kg of carbon-di-oxide into the atmosphere. The present research community is focusing on developing alternative binders to minimize the production of OPC. Alkali Activated Binders (AABs) such as Alkali Activated Slag (AAS), Alkali Activated Slag Fly Ash (AASF), Geopolymers, etc., can be considered as potential alternatives to OPC. Precious Slag (PS) ball is an industrial by-product obtained from Ecomaister steel beads. PS ball has been identified as an alternative to fine aggregates for concrete production. In the present study, PS ball was considered fine aggregates to evaluate the performance of in Alkali Activated Slag Concrete (AASC) and Alkali Activated Slag Fly Ash Concrete (AASFC). The AASC and AASFC mixes are designed to attain a minimum strength of M40 grade and compared with conventional concrete. Sodium Silicate (SS) and Sodium Hydroxide (SH) are used as the alkaline activators. The alkaline liquid to binder ratio of 0.35 was kept constant for all the mixes. The influence of SH (i.e., 8, 10, 12, and 14M) and SS to SH ratios (i.e., 1, 1.5, 2, and 2.5) on the properties of fresh and hardened concrete were analyzed. AASC mixes are prepared with 100% GGBFS as a sole binder, while AASFC mixes are prepared by mixing GGBFS and Fly ash (FA) in different proportions, i.e., 90:10, 80:20, 70:30, and 60:40. Preliminary tests were carried out to identify the optimal NaOH concentration and dosage of alkaline activators for AASC and AASFC mixes.x The fresh and hardened properties such as workability, setting time, compressive strength, split tensile strength, modulus of elasticity, flexural strength, and abrasion resistance of different concretes were evaluated as per the standard test procedure. The durability of concrete mixes was evaluated by conducting resistance to sorptivity, hydrochloric acid, sulphuric acid, nitric acid. The water absorption and Volume of Permeable Voids (VPV) were evaluated. The flexural fatigue performance of various concrete mixes was evaluated by carrying out repeated load test on beam specimens. The fatigue life data obtained were represented and analyzed using S-N curves. Probabilistic analysis of fatigue data was carried out using Weibull distribution. Survival probability analysis to predict the fatigue lives of concrete mixes with required probability of failure was carried out. The laboratory test results indicate that the incorporation of PS ball as fine aggregates in AASC and AASFC mixes improved mechanical strength. The fatigue life improved in AASC and AASFC mixes. The fatigue data of concrete mixes can be modeled by using Weibull distribution. Improved durability performance of AASC and AAFC mixes were observed. The higher water absorption and subsequent increase inVolume of Permeable Voids (VPV) was observed at the low NaOH concentration and silicate content, due to lower hydroxyl ion concentration in the activator solution. It was observed that the activator concentration has a larger influence on the mechanical properties of AASC and AASFC mixes. High sorptivity was reported for the mixes with 8M NaOH with a gradual drop in compressive strength. The permeability property of alkali activated material was dependent on total Na2O content in the activator solution. The alkali activated mix showed good resistance towards sulphate, nitrate, and chloride attacks. The AASC and AASFC mix with PS ball as fine aggregates proved to be a good concrete for pavement.