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Title: Improvement of Cementitious and Marble Structural Properties by Photoautotrophic and Heterotrophic Bacteria
Authors: Sidhu, Navneet
Supervisor: Reddy, M Sudhakara
Goyal, Shweta
Keywords: Photoautotrophic Bacteria;Heterotrophic Bacteria;Concrete;Biogrout;Self-healing;Marble;biomineralization;Crack-healing
Issue Date: 14-Mar-2024
Abstract: Microbially induced calcium carbonate precipitation (MICCP) is a novel and eco-friendly technique to enhance the consolidation properties of building materials. In this study, the MICCP was carried out by heterotrophic and photoautotrophic bacteria to improve the structural properties of cementitious and stone material. The research focuses on isolating and characterizing urease-producing bacteria from marble dust and their efficiency in calcium carbonate precipitation. Seven isolates of ureolytic bacteria were isolated and identified as Bacillus cereus MD1, Bacillus paranthracis MD2, Bacillus paranthracis MD3, Bacillus paramycoides MD4, Bacillus paramycoides MD5, Bacillus paramycoides MD6 and Bacillus paramycoides MD7 using 16S rRNA sequence analysis. These bacterial isolates were screened based on their urease activity, calcium carbonate (CaCO3) precipitation, and sand consolidation properties. B. paramycoides MD6 observed the best results with urease activity of 1512 U/ml and CaCO3 precipitation of 1232 mg/100 ml. The sand column treated by B. paramycoides MD6 was more compact and showed a reduction in the flow rate. The amount of CaCO3 precipitated in the sand column's upper, middle and lower layers was 42.96 mg/g, 31.56 mg/g, and 21.13 mg/g, respectively. Different temperatures and pH conditions significantly influenced the growth cycle, urease activity, and CaCO3 precipitation. The optimum temperature for growth of B. paramycoides MD6 was 37 °C with a pH range of 7-10. The sand consolidation experiment was performed for three diverse grain sizes (150 µm, 300 µm, and 600 µm) to examine the efficacy of consolidation in the presence of various-sized voids within the sand particles. A sand column with a 150 µm grain size had the highest precipitation rate with solid consolidation. B. paramycoides MD6 was also incorporated into the concrete mix and tested for strength and permeability properties after 7 and 28 days of curing. The strength was observed to be significantly reduced in bacterial admixed specimens than in the control. The sorptivity coefficient and amount of charge passed through the concrete during the rapid chloride penetrability test (RCPT) experiment were reduced significantly. The results were confirmed using Field emission electron microscopy (FESEM). Energy Dispersive (X-ray) spectroscopy (EDX/EDS) and X-ray Diffraction (XRD). The biomaterial was developed by immobilizing B. paramycoides MD6 spores in metakaolin (MK). The immobilized bacteria in MK was used as carrier material in concrete to improve the cementitious and self-healing properties. The nutrient broth (NB) and corn steep liquor (CSL) were used as nutrient media for self-healing. The biomaterial stored at 4 °C and 25 °C were tested for bacterial viability for 180 days. At the end of storage, after 180 days, the biomaterial stored at 4 °C showed better results in viability, urease activity, and CaCO3 precipitation. The biomaterial NB-4 and CSL-4 showed significant improvement in concrete compressive and flexural strength at 7 and 28 days. The sorptivity coefficients of NB-4 and CSL-4 were 0.006 and 0.002 at 7 and 28 days, respectively, which were comparatively lower than the control. The self-healing capability of biomaterial was investigated for approximately 0.5 mm crack in 400 × 100 × 100 mm prismatic specimens. The crack was completely healed with 99.14% and 98.2% crack healing efficiency in CSL-4 and NB-4 biomaterial-incorporated specimens, respectively. During the healing of the crack, the water tightness of the repaired surface was 88.9% and 92.8% in CSL-4 and NB-4 specimens, verifying a reduction in water flow upon complete healing. During the crack healing period, the ultrasonic pulse velocity (UPV) was observed to improve and get closer to the reference specimens, proving the complete healing of the crack. At the end of testing, the precipitated mineral was assessed by FESEM-EDS and XRD. The developed metakaolin-based biomaterial can be used as self-healing supplementary cementitious material. Most of the studies have emphasized using ureolytic bacteria to improve the durability properties of building structures. The present investigation examined the role of photoautotrophic bacteria in enhancing cementitious properties and crack remediation. Five photoautotrophic cyanobacteria, Aphanocapsa montana BDU21001, Aphanothece species BDHKU 40501, Gleocapsa species BDU 40111, Synechococcus elongatus BDU14174 and Synechocystis pevalekii BDHKU 35101 were procured from National Facility of Marine Cyanobacteria (NFMC), Bharathidasan University, Tamil Nadu, India and were tested for CaCO3 precipitation. S. pevalekii showed maximum CaCO3 precipitation (695 mg/100 ml) in BG11 broth, followed by S. elongatus and Gleocapsa species. Based upon the highest calcification potential, the photoautotrophic cyanobacteria S. pevalekii was selected to study the consolidation effect of carbonate precipitation. The sand consolidation experiment used live (LT) and UV-treated (UVT) cells. The LT sand column was more compact and solid than the UVT sand column. The S. pevalekii (LT and UVT) was also incorporated in the mortar mix and tested for mechanical and permeability efficiency. The compressive strength of mortar specimens was significantly enhanced by 25.54% and 15.84% compared to control with live- and UV-treated S. pevalekii cells at 28 days of curing. Water absorption levels were reduced considerably in bacterial-treated mortar specimens compared to control at 7 and 28 days of curing. CaCO3 precipitation was higher in live-treated cells than in UV-treated S. pevalekii cells. CaCO3 precipitation by S. pevalekii cells was confirmed with SEM-EDS, XRD, and TGA analysis. These results suggest that using S. pevalekii bacteria can serve as a low-cost and environment-friendly MICCP technology to improve the durability properties of cement mortar. An eco-friendly and sustainable biogrout was developed using S. pevalekii for crack remediation in concrete. To improve the fluidity characteristics of the grout, fly ash (FA) was incorporated as a partial cement replacement in the cementitious grout. The cementitious grouts were tested for fresh properties at different dosages of FA (0%-50%) by keeping water (or bacterial culture) to binder ratios of 0.45, 0.47, and 0.50. Based on flowability results, a 0.47 culture/binder ratio was selected to examine different FA dosages for hardened properties. A 40% FA substituted cementitious biogrout was selected for repairing cracks at the lab scale. Different cracked concrete specimens were repaired and cured using ponding and spray treatment for 28 days. At the end of the experiment, a significant improvement in strength and permeability was recorded in biogrout-remediated cracked specimens. The sample was collected from the healed cracked region to confirm the CaCO3 precipitation using FESEM-EDS, XRD, and thermogravimetric analysis (TGA). The developed FA-incorporated biogrout serves as an economical and eco-friendly MICCP technology for the remediation of existing cracks in concrete structures. A comparative analysis was performed between photoautotrophic and heterotrophic bacteria to enhance concrete's mechanical and permeability properties. The specimens were cast using live S. pevalekii (SPC) and B. paramycoides (BPC) cells. The microbes incorporated concrete specimens showed significantly improved compressive strength compared to the control specimens prepared using tap water. However, a marginal difference (1.8%) was observed between the SPC and BPC specimens. The charge passed through SPC and BPC specimens during the rapid chloride permeability test was 1901 and 1440 coulombs, respectively, after 28 days of curing. The water absorption reduced after 28 days with 0.007 and 0.005 sorptivity coefficients for SPC and BPC specimens, respectively. The CaCO3 crystallization in SPC and BPC specimens was confirmed using a FESEM-EDS. The peaks of calcite and vaterite were observed in XRD. Calcification potential and consolidation properties were studied to evaluate the efficacy of S. pevalekii and B. paramycoides to precipitate CaCO3 on the marble stone. The bound CaCO3 on the surface was analyzed by weight gain on the sample. Maximum weight gain was observed in marble samples treated with 6 ×10-7 cells with 1.40 g and 1.94 g in B. paramycoides and S. pevalekii-treated samples, respectively. The marble stones were tested for acid rain attack by performing lab-scale artificial acid rain spray using four different solutions. The four solutions comprise nitric acid (HNO3), sulphuric acid (H2SO4), and a mixture of two solutions at different concentrations. The changes on the surface were assessed by weight change, roughness, microscopic visualization, and atomic force microscopic (AFM) observation. Exposure to acid rain affected the marble and resulted in weight loss due to granular disintegration. The alteration in colour was observed only in marble samples treated with H2SO4. The MICCP treatment was performed by immersing the acid-affected marble samples in bacteria and cyanobacteria culture for 28 days. The surface was improved significantly by the gain in lost carbonate at each consecutive interval by heterotrophic bacteria and photoautotrophic cyanobacteria. The outcomes demonstrated notable enhancements in roughness measurement and a negligible reduction of precipitated calcite on the surface due to sonication. This study affirms that both B. paramycoides and S. pevalekii significantly improved concrete's strength and permeability properties. The microbes also considerably enhanced the aesthetic properties of marble stone. These results suggest that heterotrophic and photoautotrophic bacteria play an important role in enhancing cementitious materials and marble stone.
Description: PH.D. thesis
Appears in Collections:Doctoral Theses@DBT

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