Faculty Publications

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Author: search.filters.author.Anoop, P.P.Subject: search.filters.subject.calcium carbonate

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    Long-lasting Bacillus safensis CG1 and Bacillus cereus DKBovi-5 based coconut shell biochar spore composites as self-healing additives for bio-mortar production
    (Elsevier B.V., 2024) Anoop, P.P.; Palanisamy, T.; Gupta, A.; Gopal, M.
    The major challenge in the production of bio-mortar lies in the effective storage of immobilised bacterial carriers. This study explores the effective storage and use of coconut shell biochar as a carrier for bacterial spores. Bacillus safensis CG1 and Bacillus cereus DKBovi-5 were immobilised in biochar and stored at 4 °C and 25 °C for 120 days. The storage at 4 °C showed enhanced viability, and Field Emission Gun Scanning Electron Microscopy studies revealed the firm adherence of bacterial spores within the biochar pores, attributed to the secretion of extracellular polymeric substances. Biochar-based spore composites stored at 4 °C were subsequently added as self-healing additives in mortar. Mechanical, self-healing, and microstructural evaluations demonstrated that the biochar with Bacillus cereus DKBovi-5 exhibited superior results. Cracks up to 0.888 mm were healed within 56 days, indicating enhanced healing efficiency, as supported by higher ultrasonic pulse velocity and a lower resistivity ratio. Brunauer-Emmett-Teller 20-point adsorption-desorption analysis showed that biochar with Bacillus cereus DKBovi-5 mix possessed the smallest pore width of 3.086 nm. Additionally, Field Emission Gun Scanning Electron Microscopy- Energy Dispersive X-ray Spectroscopy, X-ray Diffraction, and Fourier Transform Infrared Spectroscopy analyses confirmed the formation of biogenic calcium carbonate in the healed regions. Overall, the biochar composite with Bacillus cereus DKBovi-5 showed significantly improved performance compared to Bacillus safensis CG1 and is recommended as a long-lasting self-healing additive for large-scale construction applications. © 2024 Elsevier B.V.
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    Non-reactive biochar and Bacillus pumilus RSB17-based healing powder: A sustainable solution for enhanced bacterial viability in self-healing mortar
    (Elsevier B.V., 2025) Anoop, P.P.; Palanisamy, T.
    Existing mortar uses self-healing powders that are based on mineral admixtures, whose reactive nature negatively impacts bacterial viability and diminishes their effectiveness over time. This study aims to develop non-reactive, sustainable biochar-based healing powders with extended bacterial viability to serve as self-healing admixture in bio-mortar. Biochar from coconut husk, coconut shell, and coconut leaf petiole was evaluated for compatibility with Bacillus pumilus RSB17, emphasizing bacterial growth and calcium carbonate precipitation. Coconut shell biochar demonstrated superior performance and was used to formulate a microbial biochar healing powder. Another healing powder was prepared by lyophilizing the bacterial spore solution without protectants. The shelf life was evaluated for 180 days at 4 °C and 25 °C, demonstrating that microbial biochar healing powder at 4 °C maintained bacterial viability above the 4.5 log CFU/g threshold necessary for effective calcium carbonate precipitation, while lyophilized spore powder stored at 25 °C dropped below the threshold at 90 days. Microbial biochar healing powder stored at 4 °C for 180 days was integrated into the mortar, which healed crack width up to 0.80 mm at 56 days under submerged rainwater maintained at 27 °C ± 2 °C and 85 % ± 5 % relative humidity. Electrical resistivity decreased from 28.16 ?·m to 21.35 ?·m, the permeability coefficient dropped from 153.90 mm/s to 0 mm/s, and compressive strength regained 90.53 %, which collectively indicated enhanced self-healing. Microstructural analysis confirmed the stable cuboid calcite crystals with a crystallite size of 86.62 nm. Thus, Microbial biochar healing powder produced from coconut shell biochar and Bacillus pumilus RSB17 and stored at 4 °C is an effective self-healing admixture for bio-mortar applications with a minimum storage period of 180 days. © 2025 Elsevier B.V.
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    Coconut shell biochar–Bacillus cereus DKBovi-5 based biocomposite as a sustainable additive for cement mortar: Effect of pyrolysis temperature on characterization, strength, hydration, and healing
    (Elsevier B.V., 2025) Anoop, P.P.; Palanisamy, T.
    Although biochar–bacteria composites have been explored for self-healing in cementitious materials, the influence of pyrolysis temperature on microbial compatibility and healing performance has been insufficiently investigated. This study addresses this gap by examining how pyrolysis temperature affects the physicochemical properties of coconut shell biochar and its effectiveness as a microbial carrier in mortar. Biochar produced at 300 °C, 400 °C, and 500 °C was characterized, and Bacillus cereus DKBovi-5 was immobilized onto it to form biocomposites. The biocomposites were incorporated into mortar to evaluate mechanical, microstructural, and crack healing performances. Characterization of biochar showed enhanced crystallinity at 500 °C as indicated by XRD, development of primary and secondary pores confirmed by FESEM, and increased micronutrient concentrations due to thermal enrichment observed through ICP-MS. Compressive strength restoration increased from 80.21 % to 91.23 % between 300 °C and 500 °C temperatures. TGA analysis, interpreted using Bhatty's method, indicated an increase in the degree of hydration from 61.65 % to 65.33 %. Rietveld refinement of XRD data revealed a rise in calcite content from 24 % to 51 %. FESEM imaging confirmed the deposition of hydration products within the biochar pores. Healing evaluation showed closure of cracks up to 0.762 mm and 0.920 mm in mortars with 300 °C and 500 °C biocomposites, respectively, corresponding to healed areas of 92.49 % and 100 %. The healed products in all biocomposites were confirmed as calcite through FESEM-EDS and XRD analyses. Optimized pyrolysis at 500 °C yielded a biocomposite with superior microbial healing performance, establishing its suitability as a self-healing admixture in bio-mortar applications. © 2025 Elsevier B.V.