Measurement of Bonding Strength between Glass ...

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Geo-Congress 2014 Technical Papers, GSP 234 © ASCE 2014

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Measurement of Bonding Strength between Glass Beads Treated by Microbial-Induced Calcite Precipitation (MICP) Hai Lin1, Muhannad T. Suleiman2, Jeffery Helm3, Derick G. Brown4 1

Graduate Student, Department of Civil and Environmental Engineering, Lehigh University, Bethlehem, PA 18015, USA; email: [email protected]; 2 P. C. Rossin Assistant Professor, Department of Civil and Environmental Engineering, Lehigh University, Bethlehem, PA 18015, USA; email: [email protected]; 3 Associate Professor, Department of Mechanical Engineering, Lafayette College, Easton, PA 18042, USA; email: [email protected]; 4 Associate Professor, Department of Civil and Environmental Engineering, Lehigh University, Bethlehem, PA 18015, USA; email: [email protected]; ABSTRACT: Microbial induced calcite precipitation (MICP) is a new soil improvement technique that shows an enhancement of the shear strength and shear wave velocity. However, the mechanical property of the calcite bond at particle-scale level, which controls macroscopic responses of soil, remains unexplored. This paper focuses on the measurement of calcite tensile and shear strength between two glass beads (simulating two sand particles) treated by MICP. The glass beads were mounted on separate movable stages attached by a displacement actuator. Then, MICP treatment was introduced to induce calcite precipitation on the glass beads. After the treatment, the stage was slowly moved sideward or upward to generate tensile or shear force on calcite bond between the two glass beads. The measured ultimate tensile and shear forces were 0.02 N and 1.94 N, respectively. The maximum tensile and shear strength in the calcite bond were 41.1 kPa and 616.5 kPa. INTRODUCTION Bio-geotechnical engineering, a new branch of geotechnical engineering, provides environmental-friendly treatment processes, utilizes low viscosity fluids which can penetrate into deep stratum, requires low cost and minimum extra energy, and sequestrates carbon underground to mitigate greenhouse gases (DeJong et al., 2006; Ivanov and Chu, 2008; Phillips et al., 2013). In this research area, Microbial Induced Calcite Precipitation (MICP) using urea hydrolysis bacteria Sporosarcina pasteurii

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(ATCC 11859) is the most widely researched. MICP does not involve the direct production of calcium carbonate (CaCO3) by microbes, but rather create an environment that is conducive to CaCO3 precipitation (Mortensen et al., 2011-a; Stocks-Fischer et al., 1999; Whiffin et al., 2007). Initial Scanning Electron Microscope (SEM) results of MICP treated sand sample conducted by our research team show that CaCO3 nucleated around bacteria surface to bridge and create the bond between soil particles (Figure 1). Therefore, the strength and stiffness of soil matrix were enhanced. It is worth noting that the precipitated calcium carbonate have various morphology (Armstrong and Ajo-Franklin, 2011).

Figure 1. Scanning electron microscopy images for precipitated calcium carbonate (CaCO3) that (a) bonds sand particles and (b) wraps Sporosarcina pasteurrii (ATCC 11859) inside. Researchers have been focusing on characterization of macro-sale soil mechanical properties using bender elements and triaxial testing (DeJong et al., 2006; Weil et al., 2012；Lin et al., 2014). However, particle-level stress assessment (stresses generated in CaCO3 bond), which controls macro-scale soil responses, remains unexplored. The objective of the research presented in this paper is to investigate the particle-level tensile and shear stresses generated in the CaCO3 bond between two glass beads treated by MICP. To achieve this objective, a test setup including precision bearing stage, motorized linear actuator, and fiber optic sensor was designed. In this paper, the setup of the test is described and preliminary results are presented. EQUIPMENT Device for Tensile Stress Measurements The setup used in our experiment is shown in Figure 2 where the two glass beads (3 mm in diameter) were attached on two precision bearing stages with stiff rebar and optical fiber (Corning SMF-28) (Figure 2a). In the preliminary tests, the stage attached to the optical fiber was manually controlled to move sideward to generate tensile force between the two glass beads. The deflection of the optical fiber was




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recorded by the high definition microscope (2.0 Mega Pixels, 500 Magnification), which allowed for calculating tensile force generated in the CaCO3 bond based on the cantilever beam theory using the equation shown in Figure 2a. Although this setup using the soft-flexible device has successfully been used to calculate for the capillary force ( 3.5 × 10 N average for 1:1 particle size ratio) by Lu et al. (2008) between two glass beads (Figure 2b, c, and d) (Dong, 2013), calculating tensile force generated in the brittle CaCO3 bond encounters a rotation moment between the two beads (i.e., not applying direct tension) and caused a nonhomogeneous tensile stress distributed in the CaCO3 bond (Figure 2c and f). The system was then redesigned to eliminate the rotation between the two glass beads. Figure 3a shows that the optical fiber was attached to the stiff rebar by epoxy and two 3 mm diameter glass beads. Then, another glass bead was attached to the middle point of the fiber, which was subjected to horizontal tension only due to the symmetry of the optical fiber beam. The forth glass bead was attached to the stiff rebar. Furthermore, a displacement actuator (Newport 850G motorized linear actuator, maximum speed: 500 μm/s) was used to accurately control the bearing stage movement.

Figure 2. Preliminary tensile test setup and responses of glass beads under the capillary force and CaCO3 bond. Notes: the figures show the (a) tensile test setup, glass beads bonded by water bridge (b) before, (c) during, and (d) after the tensile test, glass beads bonded by CaCO3 (e) before, (f) during, and (g) after the tensile test. Device for Shear Stress Measurements During the shear test, the stage was moved upward using the displacement actuator to generate shear force in the CaCO3 bond by displacement actuator. Two glass beads were attached to the rebar and optical fiber fused with the bare Fiber




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Bragg Grating (FBG) sensor (Figure 3b). FBG was made by ultraviolet light into the core of an optical fiber. The Bragg resonance (λ ) of a FBG, which is the center wavelength of light backreflected from the grating, depends on the effective index of refraction of the core (n ) and the periodicity of the grating (Λ) using the relationship of λ = 2n Λ. Parameters such as n and Λ are affected by changes in strain ( ). In this test, the FBG was used to calculate the force using the measured strain as shown in Equation 1, which is the shear force generated in the CaCO3 bond based on the force equilibrium (Figure 3 b). The equation used to calculate the shear force in the bond was presented below. = × = × × (1) Where F is the force generated in the FBG, which equals to the force generated in is the stress generated in the FBG, the CaCO3 bond based on the force equilibrium, is the cross section area of the FBG, E is the Young’s modulus of FBG, which is 70 GPa according to (Cheng et al., 2005), is the strain measured by the FBG sensor. Stiff rebar

Fixed stage

Moving direction FBG sensing system

Movable stage

Displacement actuator

Deflected optical fiber

Fixed stage

Displacement actuator Moving direction

Movable stage measured in Fiber Brag Grating (FBG)

Two 3 mm glass beads Stiff rebar Bond force: F: force EI: optical fiber stiffness L: fiber length Δ: fiber deformation

Optical fiber

Bond shear force:

(b)

(a)

Figure 3. New particle-scale devices for (a) tensile and (b) shear tests. BACTERIA PREPARATION AND MATERIALS The stock culture of Sporosarcina pasteurii (ATCC 11859) was dropped into the growth media (10g Yeast Extract, 5g Ammonium Sulfate in 500 mL 0.13M Tris Buffer (pH=9.0) sterilized by filter) to let them grow in an incubator shaker at 170 rpm, 33oC for approximately 40 hours until OD600=0.8~1. Then, the bacteria were harvested and centrifuged twice at 4000 g for 30 minutes to target bacteria density 1 × 10 cells/mL. The bacteria were stored in 4oC refrigerator until used. The cementation media for MICP contains 20 g urea, 2.12 g NaHCO3, 20 g NH4CL, 3 g Nutrient Broth, and 1mM CaCl2 in 1 L deionized water (pH=6) sterilized by filter. To model the sand particles, two soda-lime glass beads (diameter 3mm from Walter Stern Glass Beads and 2mm from Thermo Scientific Glass Beads) were used in the experiment. The glass beads were cleaned to remove any dissolvable chemicals on the surface that may interfere with CaCO3 content measurement by soaking within



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1M HNO3 for 24 hours, rinsed thoroughly with deionized water, and then driedat 105oC for 24 hours before being used. TEST PROCEDURE


Biological Treatment Initially, two beads were placed touching each other, which were checked by digital microscope. Then, the beads were embedded into a small chamber (15 mL) prior to biological treatment (Figure 4). All influent solutions were injected from the bottom at flow rate of 1.5 ml/min. The effluent solutions which went out of the chamber from the top were collected by the beaker at the bottom (not shown in Figure 4). Displacement actuator FBG sensing system

Stiff rebar

Fixed stage

Movable stage

Fixed stage Displacement actuator

Movable stage

FBG Stiff rebar

Optical fiber Optical fiber

Treatment solution

Treatment solution

(b)

(a)

Figure 4. Particle-scale devices with small chambers for biological treatment before (a) tensile (b) and shear tests. In the tensile test, 30 mL deionized water was first pumped. Then, 30 mL bacteria solution was inoculated into the small chamber and waited for 6 hours. Then, 5 flushes (every 3 hours) of cementation media (30 mL of each flush) were injected to induce calcite precipitation. After finishing all the flushes, additional 30 mL deionized water was inoculated for cleaning. Finally, the small chamber was removed and the beads were air dried before conducting the tensile tests. However, 5 cycles of treatment were conducted in the shear test. The procedure of each cycle is that the bacteria solution (25 mL) was injected into the small chamber and stayed inside for 6 hours. Then, two flushes of cementation media (30 mL of each flush) were inoculated into the small chamber. After finishing two flushes, cementation media without CaCl2 was used for cleaning. This cycle was then repeated for additional four times. Thus, total amount of CaCl2 and urea in the shear test was much larger than the amount used in the tensile test, which would cause more CaCO3 precipitation on glass beads in the shear test.



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Tensile and Shear Tests The tensile and shear tests were conducted after the beads dried. The linear actuator speed was 0.1 mm/s. The sampling rate of FBG sensor was 10 MSa/s (Mega samples per second). The tensile forces were determined from the deformation of the optical fiber shown in the images of the digital microscope. The shear forces were calculated from the strain measurements using the FBG sensor (Equation 1). EXPERIMENTAL RESULTS The results of two preliminary tests are presented in this section. Figure 5 (a, b, and c) show the behavior of 3 mm diameter glass beads treated by MICP under tension. Compared to the flexible behavior of glass beads bonded by the water bridge (Figure 2 b, c, and d), CaCO3 bond responded as a brittle material, which was also observed during the shear test (Figure 5 d, and e). The images of the tensile test were processed in the Image-Pro Plus 6.0 software from Media Cybernetics, Inc. First, the picture scale from the reference ruler and fiber length were measured using the measuring tool in the software. Also, one reference line was created to represent the initial position of the stiff rebar (Figure 6 a). Then, the movement of the stiff rebar was measured (the amount of movement equals to the distance between the initial reference line and current stiff bar position, which equals to the deformation of the optical fiber) at each time step (Figure 6 b). The maximum deformation of the optical fiber was used to calculate the ultimate tensile force using the equation shown in Figure 3 a. The calculated ultimate tensile force was 0.02 N for 3 mm diameter glass beads. Since the bond breaks within the calcium carbonate, the thickness of the calcium carbonate was measured using the Image-Pro software, and assuming a cylindrical bridge between the two beads, the cross section of the breaking position was calculated (i.e., the diameter of cross section equals the measured thickness of calcium carbonate), then, the tensile stress can be calculated using tensile force and the cross section area of the CaCO3,. The tensile stress was 41.1 kPa. After the test, the CaCO3 content (mass of precipitated CaCO3 on whole surface area of one bead over mass of one glass bead) was determined to be 9.5% by using acid wash technique performed with 5 M Hydrochloric acid (Mortensen et al., 2011 b). In the shear test, the wavelength shifts of the reflected light transmitting in the FBG sensor were recorded, which were used to calculate strain values generated in the FBG sensor using the calibration between wavelength shift and strain shown in Figure 7 a and b. The bonding shear force was calculated from the strain measurement using Equation 1. The result showed that the ultimate shear force was 1.94 N for 2 mm diameter glass beads bonded by CaCO3. By using the same calculating procedure of the CaCO3 bond’s tensile stress, the shear stress can be calculated as 616.5 kPa. The CaCO3 content was determined as 24% using acid wash technique. The shear strength is 15 times higher than the tensile stress, however, the two tests have different



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CaCO3 contents between the glass beads.

Figure 5. Digital microscope images shown (a) before, (b) during, (c) after the tensile test, (e) before, and (f) after the shear test.

Figure 6. Digital microscope image processing for the tensile test. Note: (a) the 5 mm scale and fiber length were measured. Also, one reference line was created to represent the initial position of the stiff rebar. (b) Then, the maximum movement of the stiff rebar at bond failure was measured by measuring the moving distance relative to the initial rebar position. Then, the maximum deformation of the optical fiber was used to calculate the tensile force using the equation shown in Figure 3 a.



.0020

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Wavelength shift

Time (s)

.10

0 2

.05

.0012 .0008 .0004

0.00


y=0.0011x R2=0.982

.0016

.15

Strain (ε)

Intensity (dB)

.20

-.05 1510

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fitted line Experimental data

0.0000 1520

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1540

Wavelength (nm)

1550

1560

0.0

.2

.4

.6

.8

1.0

1.2

1.4

1.6

Wavelength shift (nm)

(a)

(b)

Figure 7. Data processing of FBG sensor for the shear test. Notes: (a) the wavelength shift of the light in the FBG sensor was measured first from 0 second to 2 seconds which manifested the largest shift. Then, (b) the amount of strain generated in FBG sensor was calculated by using the calibration relationship between wavelength shift and strain. Finally, the bonding shear force was calculated from the strain measurement using Equation 1. DISCUSSION Compared to axisymmetric condition of the water bridge between glass beads, the precipitated calcite had a non-uniform distribution around two glass beads (Figure 5 and 6). Also, most CaCO3 precipitated at the top of two glass beads, which posed a difficulty for modeling bond shape and strength. Furthermore, the literatures on the shear and tensile strength of calcite were limited (compressive strength of calcite, 892±112 MPa, Ribeiro, 2012). Martinez et al. (2009) concluded that fracturing of the cemented sand matrix by MICP was controlled by CaCO3 phase only. This test result presented here also confirms that the fracture happens in the bond not at the interface between CaCO3 and bead surfaces, which can be shown in Figure 5. CONCLUSION This paper describes the preliminary particle-scale test results of glass beads with different sizes treated by MICP. The test devices for tension and shear use precision bearing stage, motorized linear actuator, and fiber optic sensor. After the tests, it was observed that the failure occurred in the CaCO3 bond. The ultimate tensile and shear forces are 0.02 N and 1.94 N, respectively, and the maximum tensile and shear strength are 41.1 kPa and 616.5 kPa. The further research is currently being conducted on more tests to confirm the preliminary test results and to investigate the relation between the amount of CaCO3 precipitation and tensile and shear strength.



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ACKNOLEDGEMENT


The authors would like to acknowledge the support of the Geotechnical Engineering Program of the CMMI Division at National Science Foundation (Grant No. 1233566) and the Faculty Innovation Grant (FIG) from Lehigh University. The authors also would like to acknowledge the help of master students Hang Dong and Dalong Wang from Lehigh University. REFERENCES Armstrong, R., and Ajo-Franklin, J. (2011). “Investigating biomineralization using synchrotron based X-ray computed microtomography.” Geophysical Research Letters, 38, L08406. Cheng, C., Lo, Y., Pun, B. S., Chang, Y. M., and Li, W. Y. (2005). “An Investigation of Bonding-Layer Characteristics of Substrate-Bonded Fiber Bragg Grating.” Journal of Lightwave Technology, 23(11): 3907-3915. DeJong, J. T., Fritzges, M. B., and Nusslein, K. (2006). “Microbially Induced Cementation to Control Sand Response to Undrained Shear.” Journal of Geotechnical and Geoenvironmental Engineering, 132(11): 1381-1392. Dong, Y. (2013). “Engineered Soil with Thermally Controlled Wettability.” Ph. D. dissertation, Lehigh University, Bethlehem, PA. Ivanov, V., and Chu J. (2008). “Applications of Microorganisms to Geotechnical Engineering for Bioclogging and Biocementation of Soil in Situ.” Reviews in Environmental Science and Bio/Technolog, 7(2): 139-153. Lin, H., Suleiman, M. T. and Brow, D. G. (2014). “Mechanical behaviors of sand treated by biocalcification.” In preparation. Lu, N., Lechman, J., and Miller, K. T. (2008). “Experimental Verification of Capillary Force and Water Retention between Uneven-Sized Spheres.” Journal of Engineering Mechanics, 134(5): 385-395. Martinez, B. C., and Dejong, J. T. (2009). “Bio-Mediated Soil Improvement: Load Transfer Mechanisms at the Micro- and Macro- Scales.” US-China Workshop on Ground Improvement Technologies, ASCE GSP 188, 242-251. Mortensen, B. M., Haber, M. J., DeJong, J. T., Caslake, L. F., and Nelson, D. C. (2011a). “Effects of Environmental Factors on Microbial Induced Calcium Carbonate Precipitation.” Journal of Applied Microbiology, 111(2): 338-349. Mortensen, B. M., Haber, M. J., DeJong, J. T., Caslake, L. F., and Nelson, D. C. (2011b). “Effects of Environmental Factors on Microbial Induced Calcium Carbonate Precipitation.” Journal of Applied Microbiology, 111(2): 338-349. Phillips, A. J., Lauchnor, E., Eldring, J., Esposito, R., Mitchell, A. C., Gerlach, R., Cunningham, A. B., and Spangler, L. H. (2013). “Potential CO2 Leakage Reduction through Biofilm-Induced Calcium Carbonate Precipitation.” Environmental Science Technology, 47(1): 142-149. Ribeiro, L. (2012) “Mechanics of Calcite-Polymer Microcomposites Using Nanoindentation and Micro-Compression.” Doctor of Philosophy Dissertation,




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The University of Manchester, School of Materials, Manchester, United Kingdom. Stocks-Fischer, S., Galinat, J. K., and Bang, S. S. (1999). “Microbiological Precipitation of CaCO3.” Soil Biology and Biochemistry, 31(11): 1563-1571. Weil, M. H., DeJong, J. T., Martinez, B. C., and Mortensen, B. M. (2012). “Seismic and Resistivity Measurements for Real-Time Monitoring of Microbially Induced Calcite Precipitation in Sand.” Geotechnical Testing Journal, 35(2): 1-11. Whiffin, V. S., Van Paassen, L. A., and Harkes, M. P. (2007). “Microbial Carbonate Precipitation as a Soil Improvement Technique.” Geomicrobiology Journal, 24(5): 417-423.
