Browsing by Author "Das, Bibhuti Bhusan"

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Influence of Raw Materials and Binding Agents on Engineering Properties of Fly Ash based Pelletized Aggregates
(National Institute of Technology Karnataka, Surathkal, 2024) Sharath, B P; Das, Bibhuti Bhusan
Mechanical and Microstructural Properties of Geopolymeric Fly Ash Based Mortar Cured in Ambient Conditions
(National Institute of Technology Karnataka, Surathkal, 2024) K M, Prasanna; Das, Bibhuti Bhusan; Mahesh, Gangadhar
This experimental study aims to improve the IST and FST, flowability, and compressive strength of FA-based geopolymer mix samples for pastes, mortars, and mortars with steel fibre additions by substituting GGBS with various alkaline to binder ratios. GGBS substitution in geopolymeric mixtures is essential for achieving quicker setting in the resultant geopolymeric samples and also to accomplish the practical viability without any heat curing. SEM-EDS and FTIR were used to perform microstructural characterization and chemical identification of structural growth in the resulting geopolymers. According to the obtained findings, GGBS addition increased geopolymeric samples compressive strength while decreasing their setting time. The IST attained for geopolymeric paste samples is 20 minutes for F50:G50 samples with an alkaline to binder ratio of 0.5. However, the FST attained is 485 minutes for F100:G0 samples with an alkaline to binder ratio of 0.8. The highest 28 days compressive strength attained for geopolymeric paste samples is 85 MPa for F50:G50 samples with an alkaline to binder ratio of 0.5. Furthermore, for geopolymeric mortars, the IST attained is 22 minutes for F50:G50 samples with an alkaline to binder ratio of 0.5, whereas the FST attained is 668 minutes for F100:G0 samples with an alkaline to binder ratio of 0.8. A highest compressive strength of 56 MPa at 28 days is attained for F50:G50 geopolymeric mortar samples with an alkaline to binder ratio of 0.6. Additionally, for geopolymeric samples with steel fibres, after a curing period of 28 days, the compressive strength obtained is 69.5 MPa. This was observed in specimens containing 1% steel fibre content, an alkaline to binder ratio of 0.6, and binder proportions of 50%:50%. SEM microphotographs of geopolymeric pastes and mortar samples revealed the presence of a dense matrix with the GGBS substitution. Furthermore, the presence of rough steel fibre surfaces and hydration reaction products on the steel surface implies a rather good link between the geopolymer matrix and steel fibre, which boosts compressive strength values, as observed in SEM images of steel fibre-containing mortar samples. The FTIR analysis of geopolymeric paste samples reveals a notable downward shift in wavenumbers of distinctive bands, corresponding to varying levels of GGBS substitution. This shift signifies a heightened degree of geopolymerization within the paste samples.
Optimized proportion for producing fly ash based coarse aggregates integrated with copper ore tailings
(Indian Patent Office, Chennai, 2024-02-09) Das, Bibhuti Bhusan; B. P. Sharath; National Institute of Technology Karnataka, Surathkal
Recent Developments in Sustainable Infrastructure
(2021) Das, Bibhuti Bhusan; Barbhuiya, Salim; Gupta, Rishi; Saha, Purnachandra
Sustainable Construction and Building Materials
(2019) Das, Bibhuti Bhusan; Neithalath, Narayanan
Thermo-Mechanical and Durability Properties of Cement Mortar Integrated With Nano-Silica Particles
(National Institute of Technology Karnataka, Surathkal, 2022) K, Snehal; Das, Bibhuti Bhusan
Evolution of infrastructure investments is important for the alleviation of poverty in emerging countries like India. Consequently, time frame execution of construction projects plays a vital role. This can be achieved through the application of superior pozzolanic material such as nano-silica in cementitious composites. However, there are certain number of problems associated with the inclusion of nano-silica such as workability issue, high heat of hydration, shrinkage and the associated cost. Hence, it is more appropriate to use supplementary cementitious materials (SCMs) in conjunction with nano-silica to produce high performance sustainable cementitious composite mixes. On the other side, the scientific and industrial communities are heavily investing on conservation of energy. Therefore, there is a need to increase the energy efficiency of the building constituents by cutting down the thermal loading. In this regard, various classes of phase change materials (PCMs) act as heat absorbing/transfer medium (latent heat storage system). However, major detriment of PCMs in cementitious composites are its physical and chemical interference with hydration products leading to loss in structural integrity. Therefore, there is a need to incorporate a highly reactive material like nano-silica along with PCM resulting in thermally efficient and sustainable construction material. In this perspective, present study was carried out to understand the influence of nano-silica on hydration properties of binary, ternary and quaternary blended cementitious composites containing micro to nano sized admixtures including fly ash (FA), ultrafine fly ash (UFFA) and colloidal nano-silica (CNS). Study also demonstrated the influence of integrating phase change materials (PCMs) on thermo-mechanical properties of nano-silica admixed cementitious composites. In the initial stage of study dosage of nano-silica (0.5% to 3.5% at 0.5% interval) was replaced with ordinary Portland cement in correspondence to obtain the optimum compressive strength of cement mortar. Further, optimised cementitious mix was designed through particle packing theory by adding suitable proportion of FA and UFFA. In the later part of the experimental investigation, nano-silica modified mix was added with the desired proportion of PCMs to identify the thermal efficiency of the cementitious composite. Hydration, mineralogical and microstructural studies of cementitious composites were carried out through advanced characterization techniques such as, thermogravimetric analysis (TGA), X-ray diffraction (XRD) and scanning electron microscopy empowered with energy dispersive X-ray spectroscopy (SEM-EDX), respectively. Thermal properties of PCM integrated cementitious composites were determined by means of differential scanning calorimetry (DSC). The experimental test results revealed that the optimum dosage of CNS in binary blended cementitious composites was found to be 3%. However, slump flow test indicated the intensified demand for water absorption and reduced workability with increase in level of CNS content. The presence of nano-silica in cementitious system amplified the hydration and pozzolanic activity, thereby promoting densified microstructure. It is to be noted that quaternary blended mix also showed promising results with respect to hydration, microstructure, mechanical and durability properties. Experimental results of PCMs integrated cementitious composites showed improved thermal efficiency as well as reduced the chemical shrinkage, but adversely affected the mechanical, hydration, and durability properties. It was found that cementitious mortar comprising of both nano-silica and PCMs have compensated the drawbacks of one another. Composite mix (having both nano-silica and PCMs) showed superior strength gain at early age, better durability resistance, low chemical shrinkage, and superior thermal performance. At this point of time, it is understood from the experimental investigation that it is possible to attain sustainable cementitious composites by blending fly ash or/and ultrafine fly ash along with highly reactive nano-silica. This experimental study also gives an understanding that PCMs and nano-silica can be combined in cementitious composites to a suitable proportion to give the best performance with respect to the compressive strength development, minimization of shrinkage, hydration, and microstructure development. In addition, a PCM admixed cementitious composite can be proportioned to store a suitable amount of heat energy.
Use of Aluminium Refinery Residue (Red Mud) as A Construction Material for Pavements
(National Institute of Technology Karnataka, Surathkal, 2022) Kudachimath, Nityanand S.; Mulangi, Raviraj H.; Das, Bibhuti Bhusan
A good road network connects remote places and also acts as a feeder system to the other modes of transportation. Manufacturing and the construction industries are in boom with the growing economy of the World. With the growing infrastructure, the demand for conventional construction materials is high, resulting in the depletion of natural resources. In recent days, pavements are subjected to excessive loads due to freight traffic, meanwhile, the depletion of conventional materials has forced people to shift towards alternate construction materials and researchers are in search of alternate materials which can provide the same strength as that of conventional materials. Therefore, waste materials from different industries are tested in laboratories by researchers to replace the natural materials in pavement constructions. Aluminium and steel are produced in very large quantities compared to other metals, these industries also produce the by-products that are either partially utilized or unutilized. Aluminium refinery residue (ARR) with its colour known as red mud, produced from bauxite by Bayer process, its high pH demands huge storage land. The steel and Iron Industries produce ground granulated blast furnace slag (GGBS) as a by-product. In road construction, a large quantity of material is required at the lower layers. In this present work, waste from both industries was used, GGBS makes complex compounds with sodium hydroxide and sodium silicate which increases the strength properties of ARR. The aluminium refinery residue was stabilized with 20, 25, 30% of GGBS, 3, 4, 5% of sodium oxide (Na2O) and silica modulus (Ms) of 0.5, 1.0,1.5 at fixed water to binder ratio 0.25. The compaction test was done on both the treated and untreated aluminium refinery residue to check the maximum dry density and optimum moisture content. The treated samples were cured (for 0,7,28 days) at room temperature. In case of stabilized ii aluminium refinery residue, the maximum strength was achieved at 25% of GGBS and alkali solution consisting of 4% Na2O and 1.0 Ms at both standard and modified Proctor densities. The stabilized aluminium refinery residue with 25% and 30% of GGBS and alkali solution consisting of 4 and 5% of Na2O having 1.0 and 1.5 Ms has passed durability test after 28 days of curing at both densities. The stabilized ARR with 25% of GGBS and alkali solution consisting of 4% of Na2O having Ms of 1.0 at both densities achieved the maximum flexural strength, fatigue life, and the densified structure. The formation of calcium-silicate hydrate and calcium aluminosilicate hydrate structures resulted in a remarkable improvement of compressive strength, flexural strength and fatigue life of the stabilized samples due to the dissolved calcium ions from GGBS, and silicate and aluminium ions from alkali solutions. The design of roads was done by replacing the conventional granular layer with the durable stabilized ARR based on Indian standard codes and the thickness of pavement with stabilised ARR was lesser than the conventional pavement layer. Stress-strain analysis was carried out using IITPAVE software and found that stresses were within the limit. The cost comparison of the pavement made with conventional material and with the proposed GGBS stabilized ARR was carried out and the cost of stabilised pavement layer was nearly same as that of the conventional pavement layer.