Crack Repair Research Articles

Preparation of multi-layer compound microcapsules and their application in self-healing of concrete cracks

Concrete is widely used in building construction, civil engineering, roads, bridges, etc., but concrete cracking remains a major issue in the engineering industry. To develop an effective and feasible concrete repair technology, this study combined microbial and microencapsulation technologies to prepare a multi-layer compound microcapsule using the piercing method. The formulation and drying method of microcapsules were optimized by taking their embedding rate and mechanical properties as evaluation criteria. The calcium transcrystallization process of microcapsules and the crystal form of products were characterized and compared with the calcium transcrystallization process in free cells. Finally, the effects of microcapsule incorporation on mechanical properties, impermeability, and self-healing performance of concrete specimens were then tested. The results showed that the air-dried multi-layer compound microcapsules, formulated with 1.0% wet cells of Bacillus cereus, 1.5% calcium chloride, 3.0% sodium alginate, 5.0% nutrients, 6.0% glycerol, 0.6% chitosan, and 2.0% urea, achieved an embedding rate of 95.3%, a rupture force of 60.0 N and a hardness of 150.8 N. These microcapsules can transform from a solid state to a flowing colloidal state when the microorganisms inside undergo a calcium formation reaction. Both the microcapsules and free cells produced stable calcite crystal forms of calcium carbonate through the calcium conversion reaction, with the microcapsules producing more uniform-sized particles, which are more conducive to accumulation in cracks, thereby enhancing the stability of repair. When microcapsules were incorporated into the concrete specimen at a content of 0.45%, the flexural strength of the specimen increased by 17.3%, and the compressive strength increased by 12.3%. In the water impermeability test, specimens with microcapsules demonstrated better impermeability compensation for the cement concrete than those with free cells. The self-healing effect of cracks proved that multi-layer compound microcapsules could completely repair cracks up to 0.7 mm wide, and a repair rate of 95% for 0.8 mm wide cracks. In this study, a multi-layer compound microcapsule was developed to protect microorganisms in concrete and provide nutrients required for their growth, which provided a new idea for microbial induced calcium carbonate precipitation in concrete crack repair.

Research on the application of nano modified epoxy resin adhesive in the repair of cracks in building concrete

Research on the application of nano modified epoxy resin adhesive in the repair of cracks in building concrete

Research on the application of nano modified epoxy resin adhesive in the repair of cracks in building concrete

Research on the application of nano modified epoxy resin adhesive in the repair of cracks in building concrete

The effect of Bacillus bacteria and nano clay on the properties of roller pavement concrete and self-healing of its cracks due to calcium carbonate deposition

ABSTRACT One of the best methods to enhance the strength and durability of concrete and repair the cracks is to use a self-healing mechanism, based on bacterial-induced calcite precipitation. In this study the effect of this mechanism was investigated on untreated roller concrete pavement containing nanoclay. The bacteria used in this study was Bacillus sphaericus. The specimens were characterized using permeability, compressive strength, tensile strength, and ultrasonic tests. At first, one face of the specimens was subjected to bacterial self-healing to permeability test and all faces to compressive and tensile strength test. Also, using a copper sheet, a standard crack was created on one side of the specimens, and then the repair rate of these cracks due to bacterial self-repair was investigated by ultrasonic testing. The results showed that permeability, compressive and tensile strengths improved by 2.2%, 7.1% and 14.4%, respectively in the treated specimens without nanoclay. Meanwhile, in concrete specimens containing nanoclay, the improvement rate increased. Also, the results of the ultrasonic test showed that repair occurs by this coating and its rate is 12% in nanoclay-treated specimens and 7% in treated specimens without nanoclay, which shows the positive effect of nanoclay in improving the bacterial repair of standard cracks.

Crack Sealing in Concrete with Biogrout: Sustainable Approach to Enhancing Mechanical Strength and Water Resistance.

Concrete, as the most widely used construction material globally, is prone to cracking under the influence of external factors such as mechanical loads, temperature fluctuations, chemical corrosion, and freeze-thaw cycles. Traditional concrete crack repair methods, such as epoxy resins and polymer mortars, often suffer from a limited permeability, poor compatibility with substrates, and insufficient long-term durability. Microbial biogrouting technology, leveraging microbial-induced calcium carbonate precipitation (MICP), has emerged as a promising alternative for crack sealing. This study aimed to explore the potential of Bacillus pasteurii for repairing concrete cracks to enhance compressive strength and permeability performance post-repair. Experiments were conducted to evaluate the bacterial growth cycle and urease activity under varying concentrations of Ca2+. The results indicated that the optimal time for crack repair occurred 24-36 h after bacterial cultivation. Additionally, the study revealed an inhibitory effect of high calcium ion concentrations on urease activity, with the optimal concentration identified as 1 mol/L. Compressive strength and water absorption tests were performed on repaired concrete specimens. The compressive strength of specimens with cracks of varying dimensions improved by 4.01-11.4% post-repair, with the highest improvement observed for specimens with 1 mm wide and 10 mm deep cracks, reaching an increase of 11.4%. In the water absorption tests conducted over 24 h, the average mass water absorption rate decreased by 31.36% for specimens with 0.5 mm cracks, 29.06% for 1 mm cracks, 27.9% for 2 mm cracks, and 28.2% for 3 mm cracks. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses confirmed the formation of dense calcium carbonate precipitates, with the SEM-EDS results identifying calcite and vaterite as the predominant self-healing products. This study underscores the potential of MICP-based microbial biogrouting as a sustainable and effective solution for enhancing the mechanical and durability properties of repaired concrete.

Biological concrete, a viable alternative in modern civil construction: Review

Concrete and/or mortar are the most commonly used construction materials and have a high tendency to form cracks. These cracks lead to a significant reduction in the useful life of the concrete structure and high preventive maintenance costs. Although it is not possible to prevent cracks from forming, there are several types of techniques to heal cracks. It has been shown that some of the current concrete treatment methods, such as the application of chemicals and polymers (epoxy), are a source of health and environmental risks and, more importantly, are only effective in the short term. Therefore, alternative, environmentally friendly and long-lasting methods are being developed with high potential for use and at lower prices than conventional concrete. A microbial self-healing approach is distinguished by its potential for lasting, rapid and active crack repair, while also being capable of maintaining the quality of the environment. Furthermore, the self-healing approach mainly by anaerobic and aerobic bacteria prevails over other treatment techniques due to the efficient binding capacity and compatibility with concrete compositions in the formation of media capable of protecting the concrete structure by forming Calcium as a product of special metabolism. This study provides an overview of microbial approaches to produce calcium carbonate (CaCO3) and application of bioconcretes in civil construction. They discuss everything from conventional concrete, concrete pathologies to forms of remediation in the development of high quality and resistant bioconcrete based on a systematic review. Finally, this review focuses on the use of bioconcrete as a viable and sustainable alternative for modern civil construction that combines the use of alternative materials for self-healing and environmental maintenance.

Dynamic Redeposition Over Bidirectional Amorphous NiFe-Oxides toward Surface Self-Healing for the Alkaline Oxygen Evolution Reaction.

The NiFe-oxy/hydroxides (NiFeOxHy) have emerged as promising candidates for alkaline oxygen evolution reaction (OER) but suffer from irreversible metal dissolution to pose a great challenge to long-term stability. Here, a self-supported electrode of NiFeOxHy/FeNiOx/SS-A (substrate-etched stainless steel, SS-A; interlayer-amorphous Fe3Ni1Ox oxide; catalytic layer-amorphous Ni3Fe1OxHy) is fabricated and presents rare self-healing property of surface cracks, as well excellent activity and stability. It is found that crack repair is driven by the redeposition of dissolved Fe and Ni ions from the amorphous interlayer involved in the OER process because no similar behavior is observed in Fe-free and crystalline interlayer-supported NiFeOxHy. Moreover, the repair performance is dependent on current density and electrolysis time, with 71% of surface cracks being repaired after 72h operated on an industrial level of 500mA cm-2. It needs to be emphasized that the irreversible dissolution of Fe and Ni from the catalytic layer of NiFeOxHy still occurs but is effectively suppressed. It is demonstrated that the construction of an amorphous FeNiOx oxide interlayer in self-supported electrodes plays an important role in improving the stability and is expected to open up an opportunity for the design and develop highly efficient and durable alkaline OER catalytic electrodes.

The Role of Microorganisms in Bio-cement Production: An Extended Review

Bio-cement is an innovative material with the potential for replacement of conventional cement through microorganisms-influenced process. The major method uses bacterial, fungal, or algal activity to produce Microbial-Induced Calcium carbonate Precipitation (MICP). This review aims to understand the microbial aspect of bio-cement production explaining the process through MICP that is enhanced by ureolytic bacteria with a focus on <i>Sporosarcina pasteurii</i> through the provide urease. Bio-cement has many environmental advantages such as lower CO<sub>2</sub> emission in comparison with common cement and opportunities to utilization of waste products. In construction, it is used in self-healing concrete, crack repair, and soil stabilization among others to demonstrate its flexibility in the construction industry due to its available solutions to many structural and geotechnical problems. The review also includes directions for basic, applied, and translational research, targeted genetic modifications for enhanced microbial performance, bio-cement, and more effective microbial strains, and the convergence of bio-cement with 3D printing. Even though bio-cement is an environmentally friendly approach used for soil stabilization, the negative impacts that surround the environment, for further research in making the bio-cement more bio-deteriorate and energy efficient.

Microbial self-healing cement-based materials co-reinforced by Mg2+: using recycled aggregates as carriers

Microbial self-healing cementitious materials have attracted widespread attention due to their targeted repair of cracks, but their practical application is limited by cost. In this study, self-healing mortar was prepared using recycled concrete fine aggregate as a cementitious material to investigate the effect of magnesium ions on crack repair, to explore the compatibility of self-healing components and cement, and to assess the cost and environmental impact of this self-healing mortar. The results showed that the mineralization efficiency was the highest at 31.1% with a Ca/Mg molar ratio of 3, and the 28 d crack repair rate reached 97.8%; yeast and peptones in the self-repairing system slowed down the rate of cement hydration, whereas magnesium chloride and calcium lactate facilitated the hydration reaction. The use of recycled concrete fine aggregate (RCA) reduces the cost of the self-repairing material and the CO2 emission, and improves the application of microbial self-healing cementitious materials potential.

Preparation and Experimental Study of Corrosion-induced Shape-memory Fibers for Crack Repair

Repairing concrete cracks is crucial for enhancing the safety and durability of concrete structures. However, current repair technologies face limitations in corrosive environments such as marine settings. This study presents a novel corrosion-induced shape-memory fiber (CSF) based on the concept of corrosion-induced intelligent fiber (CIF). The CSF1 was made by coating elongated spandex-covered yarn with polyvinyl alcohol, and the CSF2 was prepared by winding stretched nylon fiber with iron wire. Experimental results demonstrate that CSF1 specimens can rapidly heal a 10mm wide crack within two seconds when exposed to water, while CSF2 specimens exhibit obvious shape recovery when exposed to seawater. Moreover, under midspan loads, pre-cracked CSF2-acrylic plate specimens achieve effective crack closure in seawater. These findings confirm the successful transfer of prestress from CSFs to the matrix, thereby validating the feasibility of CIF-based crack repair theory. This research provides experimental evidence for designing and optimizing self-repairing composite materials tailored for various corrosive environments and engineering applications.

Experimental study on crack repair materials for masonry ancient building based on skeleton effect

In order to obtain “repair the old as the old” ancient building crack repair materials and cracks on both sides of the wall does not produce internal stress and secondary damage, this study uses acrylamide as the core gelling material, brick powder as the force transmitting skeleton of the hydrogel material modification, the preparation of the brick powder hydrogel. The dry density, modulus of elasticity, compressive strength, toughness and dissolution properties of hydrogels with different grey brick powder admixtures were tested. Scanning electron microscopy (SEM) was used to reveal the binding mechanism in the microstructure of acrylamide hydrogel modified with brick powder. The results show that the grey brick powder particles can be embedded in the three-dimensional network structure of the hydrogel in a more complete way, which effectively improves the mechanical properties and swelling properties of the hydrogel itself; With the increase in the proportion of brick powder, the dry density, compressive strength, toughness of the brick powder hydrogel were significantly increased, and the equilibrium swelling was significantly reduced, when the proportion of 70 % of compressive strength increased by 2998.06 %, toughness increased by 2250.03 %, and the equilibrium swelling was reduced by 716.12 %. Brick powder hydrogel performance and color meet the requirements of crack repair in masonry ancient building.

Finite Element Numerical Simulation and Repair Process of Laser Cladding Repair of Surface Cracks on Mechanical Parts.

This study focuses on the planetary gear reducer and employs ANSYS 13.0 software to perform thermo-mechanical coupled simulations for the laser cladding repair process, aiming to address gear failure caused by cracks. The optimal theoretical repair parameters were determined based on temperature and stress field analyses, and performance testing of the cladding layer was conducted to validate the feasibility of the selected parameters. The results suggest that a laser power of 140 W and a scanning speed of 8 mm/s represent the optimal theoretical parameters for the laser cladding repair of the gear workpiece. Tensile strength tests revealed that the cladding layer's maximum tensile strength reached 1312.80 MPa, which was 1.22 times higher than that of the substrate material. Additionally, the wear resistance tests indicated that the wear loss of the cladding layer under the optimized parameters reduced from 9.3 mg for the base material to 0.5 mg, demonstrating excellent wear resistance. Thus, the mechanical properties of the cladding layer were significantly enhanced compared to the base material under these theoretical process parameters.

Regulating Cross-Linking Structure and Dispersion of Core-Shell-Rubber Particles in Polyurethane Composite to Achieve Excellent Mechanical Properties for Structural Adhesive Application.

Structural adhesives are bonding materials that can quickly join structures with components and repair cracks. However, thermosetting polyurethane structural adhesives suffer from disadvantages such as insufficient toughness, poor aging resistance, and long curing time, which greatly limit their practical application. Herein, a polyurethane (PU) composite with excellent mechanical properties was prepared successfully via regulating the cross-linking structure and the dispersion of core-shell-rubber (CSR) particles. Various polyols were selected to improve the cross-linking density of the PU and to enhance the intermolecular forces, which can achieve the high strength and stability of the polyurethane composites. Solvent displacement was used to improve the dispersion of CSR in PU. The cured composite has ultra-high toughness and impact resistance due to the well-dispersed CSR particles. The impact strength was increased from 52.0 to 90.4 kJ/m2, and the elongation at break was increased from 6.1% to 14.9%. Due to the addition of catalyst T120, this composite can be cured quickly at room temperature, reaching high strength after 30 min. In addition, these composites can resist extreme environments, such as high and low temperature changes, UV aging, high humidity and heat environment, and salt spray aging, which has potential and value for practical application. The prepared PU structural adhesive can meet the requirements of structural bonding transit and improve the production efficiency. This work proposed a novel strategy to prepare polyurethane composites with excellent mechanical properties for structural adhesive application.

Study on the Repair of Irregular and Deep Cracks Induced by Thermal Shock Using Al-Cu-O Reactions in Al2O3 Ceramics

The irregular and deep cracks induced by thermal shock in Al2O3 ceramics were repaired by applying Cu powder layer on their surface and heating at 1200 °C under an atmosphere of air. The Al-Cu-O liquid phase formed at 1200 °C by the reaction of molten Cu, oxygen, and Al2O3 phases penetrate deep into the narrow cracks, and the precipitation phases of Cu2O and CuAlO2 densely fill the crack interior. Our observation and analysis of the filled cracks and the surrounding areas of the repaired cracks, as well as the microstructural analysis results obtained through SEM-EDS and TEM observation, suggested the aforementioned crack repair mechanism. The bending strength of the coated surface after repairing the cracks is 301.8 MPa (ΔT = 300 °C), which is twice as strong as the specimen after thermal shock and 10% higher than the original strength of the base material.

Application and environmental sustainability assessment of microbial induced calcite precipitation in asphalt concrete crack repair

ABSTRACT Cracks are a major factor affecting the durability of asphalt concrete. Microbial-induced calcite precipitation (MICP) represents an eco-friendly method for repairing these cracks compared to conventional methods. This study investigates the repair of artificial prefabricated asphalt concrete cracks using MICP, assessing uniaxial compressive strength, permanent deformation, moisture buffering, and water sensitivity for different crack depth conditions. Microscopic analysis using SEM/EDS and X-ray micro-computed tomography was conducted. The results show that MICP reduces void fraction by 75% and increases uniaxial compressive strength and ultrasonic velocity by approximately 20%, while improving creep stiffness modulus, moisture buffering value, and resilient modulus ratio by 5%-10%. The effectiveness decreases with increasing crack depth. Calcite particles cluster within 20 mm from the crack top, enhancing mechanical properties. MICP is feasible for repairing shallow cracks. An analysis of the energy consumption and carbon emissions of the MICP technology using a life cycle assessment demonstrates that the industrial preparation processes of calcium sources and urea produce substantial carbon emissions and energy consumption, accounting for 68.31% and 94.64% of the total process, respectively, revealing that it is crucial to explore alternative materials in the future to reduce the environmental impact.

Induction Heating Optimization for Efficient Self-Healing in Asphalt Concrete.

In this study, the practical application of self-healing asphalt mixtures incorporating steel wool fibers and induction heating was investigated, expanding upon previous research that primarily assessed the self-healing properties rather than optimizing the heating process. Specifically, the aim was to enhance the induction heating methodology for a semi-dense asphalt concrete mixture (AC 16 Surf 35/50 S). In this research, the induction heating parameters were refined to improve the self-healing capabilities, focusing on the following three key aspects: (i) energy consumption, (ii) heating rate, and (iii) heating homogeneity. The findings reveal that the current intensity, the percentage of ferromagnetic additives, and coil shape are critical for achieving optimal heating conditions. Higher current intensity and additive percentage correlate with improved heating speed and reduced energy consumption. Additionally, variations in coil shape significantly influence the heating uniformity. Although asphalt mixtures with steel slag coarse aggregates exhibit slightly higher specific heat, this aggregate type is preferable for sustainability, as it allows for the recycling of industrial waste. The optimized mixtures can rapidly reach high temperatures, facilitating effective crack repair. This innovation offers a durable, environmentally friendly, and cost-effective solution for road maintenance, thereby enhancing the longevity and performance of asphalt pavements.

Microbial-Induced Calcium Carbonate Precipitation and Basalt Fiber Cloth Reinforcement Used for Sustainable Repair of Tunnel Lining Cracks

The increasing problem of urban traffic congestion has led to the extensive use of underground tunnels. However, tunnel lining cracks pose a major threat to the integrity and safety of the structure. Although the traditional repair method is effective, it often requires higher construction technology and higher cost, and may cause damage to the concrete structure. In this study, microbial-induced calcium carbonate precipitation (MICP) was combined with basalt fiber cloth to repair and reinforce tunnel lining cracks. Bacillus pasteurii was used to optimize the microbial mineralization process, and the effectiveness of the method on cracks with different widths was evaluated using a water seepage test. In addition, the mechanical properties of the reinforced tunnel lining were tested. The microbial mineralization process effectively repaired cracks with widths of 1 mm, 2 mm, and 3 mm. The use of unidirectional basalt fiber cloth increased the bearing capacity of the strengthened member by 12.5%. The combined reinforcement method also enhances the deflection performance and alleviates the influence of water seepage on the bonding performance. This innovative and sustainable approach not only provides an effective solution for the repair of tunnel lining cracks, but also contributes to the broader field of eco-friendly building materials. This study highlights the potential of using this combination approach to improve the durability and performance of underground infrastructure.

Investigating the repair of cracks through bacterial self-healing for sustainable concrete in aggressive sulfate attack environments

Concrete completely submerged in sulfate solutions has been used as the primary study subject for the durability of concrete subjected to sulfates. On the other hand, empirical data from the field indicates that concrete exposed to sulfates may exhibit physical attack-induced surface scaling above. This study aims to study the two different types of local bacteria, (BS) and (BM), with content of 0%, 0.25%, 1%, 2.50%, and 5.00% by cement weight used in this work under curing in sulfate to examine the efficiency of bacterial self-healing of cracks for sustainable concrete in aggressive sulfate attack environments. The results show that in both curing in freshwater, FW, and sulfate, SUL, the optimum bacteria ratio was 2.5% BM, and the compressive strength improved by 43.34% for FW and 47.65% for sulfate. On the other hand, the results proved that the crack-filling and crack-repairing methods may be considered quicker than conventional methods. Moreover, a detailed conclusion about the preparation and processing of bacteria to provide the most significant content of locally accessible bacteria in Egypt, mainly when using chemical and mineral additives.

Crack Development and Electrical Degradation in Chromium Thin Films Under Tensile Stress on PET Substrates

The mechanical and electrical deterioration of chromium (Cr) thin films sputtered onto polyethylene terephthalate (PET) substrates under tensile strain was studied. Understanding mechanical and electrical stability due to imposed strain is particularly important for device reliability, as the demand for flexible electronic devices increases. Cr thin films, widely spread across the field of electronic and sensor applications, face crack propagation with electrical degradation with tensile stress that can seriously compromise the performance. Accordingly, this study offers new findings on how Cr film thickness might influence crack formation and electrical resistance differently and also the general guidelines for flexible electronic component design with respect to long-term durability. Electrical resistances were measured while mechanically stretching 100- and 200 nm thin sheets. The study focused on crack development and propagation mechanisms in both film thicknesses and their effects on percentage change in electrical resistance (PCER). Scanning electronic microscopy (SEM) was used to characterize surface morphology and observe cracks as the strain rose. Early crack formation in 100 nm Cr films led to rapid PCER increases due to quick crack propagation and fast electrical degradation. Thicker 200 nm films, however, showed a more gradual PCER rise with fewer but deeper cracks, indicating a regulated strain response. Unlike the sharp PCER spike in 100 nm films, 200 nm samples were more variable, with three out of four showing a slight PCER decrease at the end, hinting at partial crack repair or conductive realignment before full failure. These results underscore the role of layer thickness in managing crack propagation and electrical stability, relevant for flexible electronics and strain sensors. This paper is aligned with the ninth goal of the United Nations Sustainable Development Goals, specifically Target 9.5: Enhance Research and Upgrade Industrial Technologies.

Introducing the mineral powder to strengthen polyurethane grouting materials for crack repair of asphalt pavements

Cracking in asphalt pavement may lead to structural distress while existing crack repair materials have significant shortcomings in terms of cost and construction efficiency. This study incorporates mineral powder into the polyurethane grouting materials to provide a more economical and durable solution for repairing cracks in asphalt pavement. The results of bonding and tensile tests show that excessive mineral powder may deteriorate the mechanical properties of polyurethane grouting materials, which is caused by the agglomeration of mineral powder observed by the microscale characterization. Characterization tests indicate that ultraviolet exposure results in the evolution of the chemical components and thermal stability of polyurethane grouting materials, subsequently causing the degeneration in the mechanical properties. The addition of mineral powders was found to increase the tensile strength of polyurethane grouting materials after Ultraviolet aging by 12 %, while the elongation at break measured in tensile tests remained essentially unchanged. The results of the splitting test, bending test, and immersion Marshall test prove the enhanced low-temperature property and moisture resistance of mineral powder-modified polyurethane grouting materials as compared to the styrene-butadiene-styrene emulsified asphalt. The economic analysis shows that this study presents a practical approach to cost-effective asphalt pavement crack repair, offering insights for enhancing the durability of asphalt pavements.