Faculty Publications
Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736
Publications by NITK Faculty
Browse
6 results
Search Results
Item Review of Various Microbial Immobilization Methods Towards Self-healing Application(Springer Science and Business Media Deutschland GmbH, 2023) Baby, B.; Palanisamy, T.; Sundaramoorthi, S.Crack development and propagation in concrete structures, associated with internal and external stresses possess a severe threat to the performance and durability. Repair works of such concrete structures impart an immense financial toll. Self-healing mortar and concrete are developed with a view to provide a solution to address the aforementioned problem. The viability and performance of calcite precipitating microbes inside the concrete, in the long term, is always a concern when it comes to self-healing application. Among different methods to introduce such bacteria inside, immobilisation is considered to yield better results having the advantage of lesser impact from the adverse environment. This paper reviews the available immobilisation and encapsulation methods for microbial transport into the mortar or concrete, which makes use of porous media, hydrogels, polymeric coatings, etc., and its effectiveness in making a resilient building material. The current practices and the challenges associated with encapsulation methods to make a viable bio-mortar is critically reviewed and presented. The interaction of microbial colonies with the transporting medium and crack healing efficiency is compared based on different encapsulation methods. An experimental study was conducted to determine the impact of nutrients on the compressive strength of cement mortar was also conducted to identify the impact on strength parameters. The nutrients like calcium lactate, calcium nitrate, urea, calcium formate, and yeast extract in different dosages were analysed to achieve the optimum dosage value. It was observed nutrients other than urea and yeast extract, improved the compressive strength of bio-mortar at respective optimum dosages. © 2023, The Author(s), under exclusive license to Springer Nature Switzerland AG.Item Experimental Study on Durability and Mechanical Properties of Lightweight Mortar with Encapsulated Spore Forming Bacteria(Springer Science and Business Media Deutschland GmbH, 2023) Akshay, J.P.; Baby, B.; Palanisamy, T.Concrete is a material that is used worldwide for centuries as a construction material. Increased consumption of concrete leads to vulnerability of structure physically, chemically and biologically. Exposure to extreme conditions and detrimental effects of corrosion of reinforcements leads to cracking of concrete. Compressive strength, Flexural strength, and permeability can be affected by these cracks consequently leading to shortening the useful life of the concrete. Repairing and maintenance of these infrastructures need higher cement consumption and expenses. The benefits of microbial concrete can reduce the consumption of cement for structural replacements and maintenance works. Self-healing concrete by microbially induced calcite precipitating bacteria is an economical and sustainable solution, as it autonomously repairs small cracks. In this paper, we discuss the mechanism and performance of bio-concrete along with the idea of microbially induced calcite precipitation (MICP). The Bacillus species is proven to be an effective microbial agent for self-healing concrete. Hence the sample preparation is done using encapsulated spore-forming Bacillus Subtilis bacteria species as a biological healing agent. Three concentrations of 105, 107, and 109 cells per millilitre are adopted for sample preparation. The mix proportion of cement mortar is 1:3, using expanded perlite as a replacement for the fine aggregate in the percentages 10% was done. The mechanical and durable properties of bio-mortar are evaluated to ascertain the possibility of the same as a resilient building material. © 2023, The Author(s), under exclusive license to Springer Nature Switzerland AG.Item Seismic Analysis of a PSC I Girder Bridge Using Nonlinear Static Method(Springer Science and Business Media Deutschland GmbH, 2023) Vamsi, A.; Baby, B.; Palanisamy, T.This paper presents a seismic analysis of three spanned Prestressed Concrete (PSC) I girder bridge, which is known for having a high load-bearing capacity and high flexural resistance. Bridge modeling is done in MIDAS Civil software. MIDAS Civil is a recently developed finite element-based software, exclusively for bridge modeling and well known for its user-friendly interface. A case study was carried on a 36.7 m of three spanned prestressed I girder bridge which consists of 4 numbers of Pre-Cast Post Tensioned-I Girder of 35.7 m long, under seismic Zone-II and is rested on hard soil strata. Loading on the superstructure is assigned as per IRC:6-2017. The entire work is divided into two phases; in the first phase, a three-dimension model of the bridge has been subjected to the linear dynamic method (response spectrum method) to obtain the displacement demand of the bridge. In the second phase, the nonlinear static method (push-over analysis) has been performed as per ACT 40 and FEMA 440. The displacement capacity results from the push-over analysis are used for carrying out seismic performance evaluation of a bridge. After analysis, the seismic response of a bridge is found out in terms of base shear and displacements. © 2023, The Author(s), under exclusive license to Springer Nature Switzerland AG.Item Optimisation of Cement Mortar Performance Through Bagasse Ash as a Sustainable Supplementary Material(Springer Science and Business Media Deutschland GmbH, 2024) Majeed, P.M.M.; Baby, B.; Palanisamy, T.Bagasse ash, a residue from the processing of sugarcane, has the potential as an environmentally friendly addition material for waste valorisation in the building sector. This study used different amounts of bagasse ash to partially substitute cement to examine the mechanical and durability aspects of cement mortar. The experimental matrix involved substituting the cement with bagasse ash at dosages of 5, 10, 15, and 20%. Using compressive strength, flexural strength, ultrasonic pulse velocity (UPV), and rapid chloride penetration tests (RCPT), both the durability and mechanical characteristics of the various mixes were studied. The results revealed that a bagasse ash dosage of 15% emerged as the optimum level, demonstrating superior mechanical and durability performance. For measuring compressive strength and UPV, mortar cube specimens measuring 70.6 mm × 70.6 mm × 70.6 mm were cast; prism specimens measuring 40 mm × 40 mm × 160 mm were formed for the assessment of flexural strength; and cylindrical specimens measuring 100 mm in diameter and 200 mm in height were cast for RCPT. The significant improvement in the compressive and flexural strengths demonstrated the beneficial impact of bagasse ash on the mortar's structural integrity. Furthermore, UPV measurements revealed enhanced internal cohesion and homogeneity in the mortar matrix. Moreover, the findings of the RCPT demonstrated a noteworthy decrease in the penetration of chloride ions, highlighting the capacity of bagasse ash to alleviate the risk of corrosion on reinforcement. This study emphasises the importance of using bagasse ash as a sustainable alternative for waste valorisation in cementitious systems. An optimised dosage of 15% enhanced the mechanical and durability properties and contributed to the eco-friendly disposal of agricultural waste. These findings support the adoption of bagasse ash as a viable supplementary material to promote environmental sustainability and improve the performance of construction materials. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2024.Item Experimental evaluation of the synergistic effect of calcium precursor dosage and bacterial strain interactions on the biogenic healing potential of self-healing cement mortar(Taylor and Francis Ltd., 2024) Baby, B.; Palanisamy, T.; Gupta, A.; Gopal, M.This study investigates the microbially induced calcium carbonate precipitation (MICP) in repair mortar, focusing on the impact of calcium precursor dosage and bacterial strain selection. C6H10CaO6·xH2O and (CH3COO)2Ca·xH2O were used as calcium precursors at dosages of 0.1, 0.25, and 0.4 M with Bacillus subtilis VEB4, Priestia megaterium TSB16, and Halobacillus halophilus MCC2188 microbes. Quantitative assessment of precipitate and optimization of precursor dosages were conducted before making mortar cube specimens of size 70.6 × 70.6 × 70.6 mm with bacterial spores and nutrients immobilized in Modified Expanded Perlite. Cracked cube specimens underwent automated wet-dry cycles of 12 h daily for 60 days to induce healing. Comparative analysis of biomortar specimens showed P. megaterium as the most effective in compressive strength recovery (up to 89.33%) and crack healing with a maximum healed crack width of 0.64 mm, followed by B. subtilis with significant CSR improvements. H. halophilus, less efficient in non-saline conditions, healed cracks up to 0.48 mm. Calcium lactate was considered the better calcium source choice for B. subtilis and P. megaterium strains, whereas calcium acetate improved MICP by H. halophilus. Microstructural analysis of healed precipitates collected from cracked cubes identified distinct morphology of MICP and the presence of polymorphs viz, calcite, aragonite, and vaterite. Tailored selection and dosage of calcium precursors for each strain significantly enhanced MICP and improved the quality of healing products in cracks, advancing the understanding of self-healing construction biomaterials. © 2024 Informa UK Limited, trading as Taylor & Francis Group.Item An experimental investigation on mitigating cracks and augmenting the endurance of concrete structures in marine environment by bio-mortar immobilised with halophilic bacteria(Elsevier Ltd, 2024) Baby, B.; Palanisamy, T.In coastal areas, built structures encounter hostile conditions and forces that can cause them to deteriorate over time owing to saltwater exposure, tidal forces, reinforcement corrosion, and freeze–thaw cycles. Early age cracks in such structures accelerate the rate of deterioration, and the current research focuses on alleviating such threats. This paper evaluates the performance of a self-healing mortar made by encapsulating expanded perlite with the bacterium Halobacillus Halophilus MCC2188. Mortar cube specimens of size 70.6 mm × 70.6 mm× 70.6 mm were prepared with cement: fine aggregate in 1:3 ratios. A 10% volume of the fine aggregate fraction was substituted with the expanded perlite immobilised with bacterial spores and nutrients. The expanded perlite aggregates were coated with sodium silicate and cement solution to protect the spores from the nonconducive environment. The specimens were subjected to fully and partially submerged marine water curing. The mechanical properties and self-healing potential were evaluated, and the precipitated polymorphs in completely healed cracks were identified and examined by characterisation techniques such as XRD, FEGSEM, FTIR, and TGA-DTG. The marine bacterium under investigation can tolerate the high salt concentrations commonly found in seawater and saline marshy soil and produce calcite through the metabolism of organic compounds, making it a suitable microorganism for self-healing applications. Crack widths of up to 0.84 mm and 92.79% average strength recovery were achieved in 56 days post-cracking, and the pace of healing was quicker in partially submerged curing conditions. The results showed improved self-healing, strength regain and mechanical strength and proved to be an efficient tool for enhancing the endurance of biomortar in severe marine exposure conditions. © 2024 Elsevier Ltd