2. Thesis and Dissertations
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Item Exploration of Calcium Rich Marine Benthos Bio-Waste to Develop Bio-Genic Hydroxyapatite for Bone Regeneration and UV Protection(National Institute of Technology Karnataka, Surathkal, 2021) Hadagalli, Komalakrushna.; Mandal, Saumen.In this study, a scalable biogenic synthesis of phase-pure hydroxyapatite (Ca10(PO4)6(OH)2, HA) (Ca/P = 1.66) scaffold from the marine-resource-derived HA together with different pore formers were conventionally sintered to produce physiologically relevant scaffolds with porous architecture. A combination of moderate compressive strength (12−15 MPa) with elastic modulus up to 1.6 GPa was achieved with ∼98% interconnected porosity using wheat flour as the pore former. More importantly, the faster nucleation and growth of the biomineralized apatite layer with full coverage within 3 days of incubation in a simulated body fluid, together with a combination of mechanical properties, establish the potential of marine-resource-derived biomimetic HA scaffold as a new generation of cancellous bone analogue. MTT assay and cell morphological analysis established the good cytocompatibility of naturally derived HA porous scaffolds, as evident from the good cellular adhesion, proliferation, and phenotypical features of osteoblast cells. The effect of Fe3+ ionic substitution in HA was studied using structural modification, such as lattice parameter, crystallite size, and particle size resulting into a drastic improvement in UV absorption through a tailored optical band structure. Ca2+ of HA being larger (0.99 Å) compared to Fe3+ (0.64 Å) contributes to the shrinkage of the lattice. Hence, hexagonal lattice parameters, a and c of HA are reduced successively as the concentration of Fe3+ increases, is observed via XRD. UV absorption of Fe-HA in the entire UVA and UVB range with an increase in Fe content because of the remarkable decrease in band gap with undoped and doped HA. Also, present work explores the use of marine resourced prawn exoskeleton/shell as a new class of naturally occurring composite containing UV absorbing proteins. Mycosporine-like amino acids with a central aromatic ring in the exoskeleton/shell of naturally occurring prawns (Fenneropenaeus Indicus) offer excellent UV protection. The presence of tryptophan, phenylalanine, and tyrosine, forming the basic building blocks of mycosporines, is confirmed by structural, compositional, and microscopic studies on prawn shells. The UV spectroscopic signatures at 290 and 320 nm provides strong evidence for the highest UV absorption. UV absorption attributes to the presence of mycosporine-like amino acids.Item Development of Thermal Efficient Non Fired Bricks using Iron Ore Tailings and Perlite(National Institute of Technology Karnataka, Surathkal, 2021) Rao, P Shubhananda.; Chandar, K Ram.Brick is the most basic artifact and plays a very important role in the construction of buildings. The construction industry is in need of easily available, economically feasible and green materials, as there is a scarcity of naturally available river sand. A lot of research is going on to improve mechanical properties of bricks and also to make more environmentally friendly and economical. A systematic study is taken up by manufacturing bricks using iron ore tailings and additives like perlite. The physical and chemical properties of the materials used in the bricks were determined as per Indian Standard (IS) codes. Use of iron ore tailings (IOT) found to be very beneficial in this research, and the addition of perlite as an admixture to improve its thermal properties is given scope for the development of non-fired thermal efficient bricks. These are non-burnt bricks manufactured in a nontraditional method, which creates a cleaner and greener environment. Bricks were made using different proportions, by replacing sand with Iron Ore Tailings from 30 to 60 percent at 10 percent interval, cement from 10 to 20 percent at 5 percent interval, and Perlite at 2 and 5 percent, of 230mmX112.5mmX75mm dimensions. The study on ecofriendly bricks aims to assess the suitability of IOT in construction in terms of strength, durability, percentage of water absorption and thermal conductivity. Based on laboratory experiments, the optimum percentage of mix to make bricks consisting of iron ore tailings, sand, cement, and perlite was found to be 50%, 25%, 20%, and 5% respectively. The optimum mix gave a compressive strength 3.89MPa, water absorption 14.82% and thermal conductivity 0.920 W/mk which are well within IS codes. Based on the positive laboratory results, further a pilot-scale study is taken up with IOTperlite bricks. In order to assess the effectiveness of IOT-perlite bricks, the pilot-scale study also planned with locally available conventional bricks (fired bricks). Two model rooms, one with IOT – perlite bricks and the other with conventional bricks are constructed to assess the effectiveness of thermal conductivity. It is assessed by measuring the temperature on all sides of the walls at different timings of the day. The results revealed that heat transferred from the outside surface to the inside surface of the bricks in the walls of the model room constructed with IOT-Perlite bricks was less compared with the room constructed with ordinary bricks. Lower thermal conductivity of IOT-Perlite bricks will tend to have less room temperature ii compared to the ordinary brick room. The reduction in the temperature of the IOT-Perlite brick room will consume less electricity and it was estimated in terms of energy savings will be around 8 percentage. The study proved that eco-friendly bricks by using IOT will have lower thermal conductivity, better strength and lightweight in structure. Regression models are developed to predict strength and durability properties like density, compressive strength and thermal conductivity. The regression fit between actual and predicted values in all cases showed a very good correlation.Item Performance Evaluation of Geopolymer Mortar Mixes Using Recycled Fine Aggregate(National Institute of Technology Karnataka, Surathkal, 2019) Saha, Suman; Rajasekaran, C.Manufacturing of Ordinary Portland cement (OPC) requires huge quantity of natural resources, energy and it releases large amount of carbon-dioxide to the environment. Numerous research efforts have been made continuously to establish geopolymer as the most suitable alternative binder material in view of economical and environment consideration. With the rapid growth in construction activities, high amount of construction and demolition waste (C&DW) is generated and large volumes of natural resources are also being consumed by the construction industry. As a result, both the quantities of C&DW to be disposed off and the scarcity of natural resources are increasing day by day. To promote sustainability in construction industry, the use of recycled concrete aggregates, resourced from C&DW is very important and provides a useful solution for the production of concrete. Here an attempt is made to use C&DW as recycled fine aggregate (RFA) for the production of fly ash based geopolymer mortar mixes. Effects of the concentration of sodium hydroxide solution, the ratio of sodium silicate solution to sodium hydroxide solution, the ratio of alkaline liquid to binder, different curing regimes and RFA content on the properties of mortar mixes produced have been explained based on the observations at laboratory. Experimental results indicate that 20% RFA can be used effectively to obtain better performances of the mixes. Using the observed results in the laboratories, prediction models for water absorption capacity, compressive strength and drying shrinkage of the produced geopolymer mortar mixes were developed using artificial neural networks.