Self-healing Concrete: Bacillus Subtilis Natto Immobilized in Lightweight Aggregate

'HYHORSPHQWRI6HOI+HDOLQJ6\VWHPLQ&RQFUHWHXVLQJ %DFLOOXV6XEWLOLV1DWWR,PPRELOL]HG LQ/LJKW:HLJKW$JJUHJDWH (ேᕤ㍍㔞㦵ᮦࢆ㍺㏦፹య࡜ࡋࡓ⣡㇋⳦࡟ࡼࡿࢥࣥࢡ࣮ࣜࢺࡢ ⮬ᕫಟ᚟ࢩࢫࢸ࣒ࡢ㛤Ⓨ) 'HFHPEHU 1JX\HQ1JRF7UL+X\QK Table of content Page Acknowledgment -----------------------------------------------------------------------------------------iv Dedication -------------------------------------------------------------------------------------------------- v Abstract ----------------------------------------------------------------------------------------------------vi List of Figures ------------------------------------------------------------------------------------------- viii List of Tables --------------------------------------------------------------------------------------------- xv Chapter 1. Why we need self-healing in concrete materials? ----------------------------------------------- 1 1. Advances and challenges for current self-healing approaches --------------------------------- 1 1. What bacteria can do and how to shorten the way from the laboratory to real self-healing applications? ------------------------------------------------------------------------------------------------ 4 Reference --------------------------------------------------------------------------------------------------- 7 Chapter 2.

Literature review of self-healing ------------------------------------------------------ 11 2. Different approaches of self-healing concrete -------------------------------------------------- 12 2. Quantification methods of self-healing ability -------------------------------------------------- 21 2. Current problems and challenges ----------------------------------------------------------------- 28 Reference -------------------------------------------------------------------------------------------------- 30 Chapter 3.

Features of the study --------------------------------------------------------------------- 35 3. Mechanism of healing products formation and promotion of the hydration process ------ 35 3. Bacterial protection in lightweight aggregate --------------------------------------------------- 36 3. Using lactose as nutrient-low for bacteria and the effect of immobilizing sugar in lightweight aggregate on prevention adverse on concrete ------------------------------------------ 42 3.

Self-healing evaluation and quantification ------------------------------------------------------ 45 Reference -------------------------------------------------------------------------------------------------- 49 Chapter 4. Materials and experiments design ---------------------------------------------------- 53 4. Analysis of the urea hydrolysis and bio-mineralization ------------------------------------- 53 4. Bacterial activites and its bio-mineralization in concrete ----------------------------------- 54 i 4.

Breakage rate and the behavior of lightweight aggregate for releasing bacterial self- healing agents --------------------------------------------------------------------------------------------- 55 4. Effect of immobilizing sugar in lightweight aggregate on prevention adverse on concrete --------------------------------------------------------------------------------------------------------------- 57 4. Compressive strength improvement using bacterial repairing solution ------------------- 58 4. Compressive strength improvement using lightweight aggregate immobilized bacteria --------------------------------------------------------------------------------------------------------------- 59 4.

Compressive strength restoration ----------------------------------------------------------------- 60 4. Continuous curing for one-cycle strength restoration --------------------------------------- 60 4. Multi-cycle strength restoration and the repetitive self-healing ---------------------------- 61 4. Ultrasonic pulse velocity --------------------------------------------------------------------------- 62 4.

Bacterial survival rate and the protecting effectiveness of lightweight aggregate --------- 63 4. Water permeability and visual evaluation of crack healing ----------------------------------- 64 4. Capillary water absorption through the crack ------------------------------------------------- 64 4. Water flow through the crack ------------------------------------------------------------------- 65 4.

Visual evaluation of crack healing ------------------------------------------------------------- 66 Reference -------------------------------------------------------------------------------------------------- 68 Chapter 5. Results and discussion ------------------------------------------------------------------- 69 5. Analysis of the urea hydrolysis and bio-mineralization ------------------------------------- 69 5. Bacterial activites and its bio-mineralization in concrete ----------------------------------- 70 5.

Breakage rate and the behavior of lightweight aggregate for releasing bacterial self- healing agents --------------------------------------------------------------------------------------------- 72 5. Compressive strength improvement using bacterial repairing solution ------------------- 73 5. Compressive strength improvement using lightweight aggregate immobilized bacteria --------------------------------------------------------------------------------------------------------------- 74 5. Compressive strength restoration ----------------------------------------------------------------- 75 5.

Continuous curing for one-cycle strength restoration --------------------------------------- 75 5. Multi-cycle strength restoration and the repetitive self-healing ---------------------------- 75 5. Ultrasonic pulse velocity --------------------------------------------------------------------------- 82 5. Pulse velocity over curing time ----------------------------------------------------------------- 82 5.

Pulse velocity over multi cracking-healing cycle -------------------------------------------- 83 5. Microstructure analysis ----------------------------------------------------------------------------- 86 ii 5. Performance of bacteria immobilized in lightweight aggregate for calcium carbonate precipitation ----------------------------------------------------------------------------------------------- 86 5. Stimulating ability on the formation and development of hydrated cement minerals of bacterial calcium carbonate ----------------------------------------------------------------------------- 91 5.

Bacterial survival rate and the protecting effectiveness of lightweight aggregate --------- 94 5. Water permeability and visual evaluation of crack healing ----------------------------------- 95 5. Capillary water absorption through the crack ------------------------------------------------- 95 5. Water flow through the crack ------------------------------------------------------------------- 97 5.

Visual evaluation of crack healing ----------------------------------------------------------- 102 Reference ------------------------------------------------------------------------------------------------ 106 Chapter 6. Possibility of Bacillus subtilis natto on bio-mineralization ------------------------------ 109 6. Mechanical behavior of self-healing concrete under multi-cracking cycles --------- 110 6. Water permeability and water leakage prevention in bacteria-based self-healing concrete -------------------------------------------------------------------------------------------------- 110 Appendix 1.

Real-scale application ---------------------------------------------------------------- 111 Appendix 2. Experimental data -------------------------------------------------------------------- 114 iii Acknowledgment I would like to to express my gratitude to the Japanese Government through the MEXT Scholarship and Building Material Science IMAMOTO LAB, Biology Science SHIMIZU LAB - Tokyo University of Science for financial support, materials, and technical equipment. By all my heart, no word can be enough to show my gratitude to my supervisor - Professor Imamoto Kei-ichi, research associate Kiyohara Chizuru, and all of the LAB members for all of their support me. I would like to express my gratitude to Shang Li and Tanaka Hiroto, my best friends, for all of their help.

All of the achievements I can get in this work is a gift for my father, my mother, my wife, and my little daughter. Thank you and love you all. Even if cracked concrete can bravely heal itself, nothing can prevent us from healing every pain ourselves º v Abstract Concrete is probably the most important and commonly used construction materials. Despite many technical improvements, concrete still faces quality degradation problems caused by cracks.

Recent studies show that the early cracking in micro-size can occur as soon as the cement matrix becomes hardened. In many ways, these cracks can become macro-size and open cracks resulting in significant issues for the durability of concrete structures as water leakage and corrosion. Many approaches have been studied more extensively, meeting the criteria, and realizing that management should be better than preventing concrete cracks. The technique of self-healing using bacteria has recently received attention for its potential applications.

With the ability to be easily cultured and form CaCO3, the potential to use Bacillus subtilis natto in the full-scale application is very promising. However, the effectiveness and the repeatability of this method over a long period was not clarified. The information on both the survival and the number of bacteria after healing is limited. This study aims to improve the self-healing capacity and evaluate the repeatability of concrete when using Bacillus subtilis natto with nutrient-low source as lactose and clarify the mechanism of the bio-mineralization to find a suitable way to protect and maintain the self-healing ability in a long time.

The high survival rate of bacteria immobilized in expanded clay lightweight aggregate gave essential information for maintaining self-healing ability for a long time. The experiments were designed to study the bacterial biomineralization, the possibility of lightweight aggregate as protecting and carrying vehicle to control the release of healing agents, and demonstrate self-healing through mechanical behavior and water permeability multi-cracking cycles. The urea hydrolysis and the bacterial biomineralization with urea and lactose as the primary carbon source were assessed. We studied the effect of cracking age on the self-healing capacity, associated with the compressive strength improvement.

The self- healing effect was expected to occur over curing time with the age of cracks from 7, 14, 28, 60, and 90 days. The compressive strength restoration of concrete specimens can translate into the self-healing efficiency, and then gives information about the relation between self-healing capacity and necessary curing time. Optical microscope and SEM/EDS/XRD microstructure analysis indicated the existence of bacterial CaCO3 forming in concrete after three cracking- healing cycles. Besides, these precipitated CaCO3 could become nucleations for promoting the crystallization of other cement minerals, creating a strong-bonding as multi-layer healing products to restore the damaged structure.

During a long duration, bacterial concentration in concrete was also determined by the colony counting method. Experimental results demonstrated that Bacillus subtilis natto could produce urease enzyme to break down urea in the harsh condition of lack of organic carbon source to form CaCO3 through the biomineralization process from three to seven days. Combining bacteria and nutrient-low in lightweight aggregate was an effective technique to control the release of healing fluid without adverse effects on setting and hardening properties. Consequently, the higher compressive strength and strength restoration of concrete specimens with bacteria could be obtained after a 3-cycle of cracking and once again confirmed the high self-healing ability of concrete when using bacteria in lightweight aggregate.

By microscopic image-analysis, cracks around 0.5 mm could be healed entirely from 7-day to 14-day curing. For the water vi permeability, both in the capillary absorption and water flow test, concrete specimens with bacteria show significantly better results than the reference. Also, Bacillus subtilis natto can survive to maintain its ability to form healing products for at least 10 months after three cycles of cracking-healing with considerable high bacterial concentration, which suggested that they can maintain their survival for years. In summary, the self-healing system in concrete using Bacillus subtilis natto immobilized in lightweight aggregate is a technique with reasonable manufacturing costs without environmentally unfriendly chemicals in producing the repairing materials.

Also, experimental results on mechanical behavior, water permeability, and crack closing process of concrete specimens can add to the understanding of the bio-mineralization of Bacillus subtilis natto in self-healing concrete and show this can be a promising solution with repeatable self-healing possibility for long-time using, leading to sustainable development. vii List of Figures Page Figure 1.1 Schematic description of repair mechanism through biomineralization using porous controlled release material immobilized Bacillus subtilis natto.2 Illustration of two approaches of crack repairing using bacteria in concrete and the healing products after long time. Outside treatment by spraying or injection (left) and inside treatment by adding bacteria into concrete mix through LWA (right) (a). The self-healing mechanism by activating Bacillus subtilis natto immobilized in LWA combines with natural carbonation and chemical reactions (b).3 Range of crack width for sufficient healing capacity through different self-healing approaches (De Rooij et al., 2013; Souradeep and Kua, 2016; Fernandez et al.4 The illustrated scenario develops a self-healing system using Bacillus subtilis natto immobilized in lightweight aggregate for concrete structures.5 The general strategy of research and experiment designs.1 Venn diagram of self-healing terminology according to JCI TC-075B.2 1XPEHURISXEOLFDWLRQVLQWKHZRUOG DQGLQ-DSDQSHU\HDULQWKHWRSLFRI³VHOI- KHDOLQJ FRQFUHWH´ 6RXUFH ³*RRJOH 6KRODU´ DQG ³-DSDQ 6FLHQFH DQG 7HFKQRORJ\ $JHQF\´ database.3 Expanded clay immobilized bacteria used as lightweight aggregate and SEM images in reference (Chen et al., 2020) (a), (Han et al., 2019a) (b), (Huynh et al.

Diatomite immobilized bacteria in two different type: paste (J. Wang et al., 2012) (d) and pellet (Huynh et al.4 Crack area detection by image processing: crack region definition, image binarization output, and final output (a) (Cuenca et al. Cracking measurements map within the gauge length (b) (NguyӉn et al. Surface binarization images of specimens with different crack width after different repair time (c) (Luo et al., 2015), (d) (Huynh et al.5 Ultrasonic schematic diagram (a).

The propagation time of the ultrasonic waves on the upper and lower surfaces to confirm that the repair agent filled the cracks (b) (TANAKA et al. Crack depth calculation by measuring the ultrasonic waves propagating time (c) (Alghamri et al., 2016; Mao et al. Ultrasonic wave-based technology to monitor the healing of cracks. Experimental results using Reflection analysis (d) and numerical simulation results using wave propagation (e) (Kaur et al.

Ultrasonic frequency analysis of concrete samples (f) (Yuan et al. Evaluate the change in concrete structure by the change of pulse velocity through the different directions of concrete specimens over time and the relationship with compressive strength (g) (Huynh et al.1 Self-healing mechanism by the activation of Bacillus subtilis natto immobilized in LWA (a). Mechanism of bacterial bioflms formation (b).2 Illustration of promoting bacterial CaCO3 on C-S-H crystallization to create multi- layers (a) and the formation of the crack healing materials with CaCO3 as the main component and C-S-H layers (b).3 The mechanism of the bioactivation process in LWA in the case of using lactose as the priority nutrient source (a), and urea as the only energy (b). Effects to each other of lactose and urea in two different ways of CaCO3 precipitation under bacterial metabolisms (c).

Illustration of the bacterial activities through multi cracking-healing cycles (d). Picture 1: the 1st crack appears, bacteria move and form healing materials while a part is washed away. Picture 2: the 2nd crack appears. Picture 3: the 2nd crack is healed, and the 3rd crack appears.

Picture 4: the bacteria begin to produce spores. Picture 5: spores occupy the other porous positions. Picture 6: when suitable conditions come, spores germinate and restart a new healing cycle.4 Crack healing on the surface of concrete specimen after the first (a), the second (2), and the third cracking-healing cycle (c).