Crack Repair Research Articles

The Evaluation of the Effectiveness of Biomineralization Technology in Improving the Strength of Damaged Fiber-Reinforced LWAC.

Concrete cracks and local damage can affect the bond performance between concrete and steel bars, thereby reducing the durability of reinforced concrete structures. Compared with general concrete crack repair methods, biomineralization repair not only has effective bonding capabilities but is also particularly environmentally friendly. Therefore, this study aimed to apply biomineralization technology to repair damaged fiber-reinforced lightweight aggregate concrete (LWAC). Two groups of LWAC specimens were prepared. The experimental group used lightweight aggregates (LWAs) containing bacterial spores and nutrient sources, while the control group used LWAs without bacterial spores and nutrient sources. These specimens were first subjected to compression tests and pull-out tests, respectively, and thus were damaged. After the damaged specimen healed itself in different ways for 28 days, secondary compression and pull-out tests were conducted. The self-healing method of the control group involved placing the specimens in an incubator. The experimental group was divided into experimental group I and experimental group II according to the self-healing method. The self-healing method of experimental group I was the same as that of the control group. The self-healing method of experimental group II involved soaking the specimen in a mixed solution of urea and calcium acetate for two days, and then taking it out and placing it in an incubator for two days, with a cycle of four days. The test results show that in terms of the relative bond strength ratio, the experimental group II increased by 17.9% compared with the control group. Moreover, the precipitate formed at the cracks in the sample was confirmed to be calcium carbonate with the EDS and XRD analysis results, which improved the compressive strength and bond strength after self-healing. This indicates that the biomineralization self-healing method used in experimental group II is more effective.

Repair of Cracks in Concrete with the Microbial-Induced Calcite Precipitation (MICP) Method

Abstract In this study, the microbiologically-induced calcium carbonate precipitation (MICP) method was employed to examine its potential for repairing cracks in concrete. In addition, specific gravity and porosity values were measured to examine the effect of calcite formations on concrete surfaces and microstructures. Bacteria-supplemented concrete repaired cracks up to 0.4 mm wide by filling them with CaCO3. Furthermore, this study not only examined the healing of the width but also the length of cracks. However, as the width of the treated cracks decreased, their length increased. This indicated that the MICP treatment is more effective in a limited crack range. Specific gravity values increased, and porosity values decreased in concrete supplemented with calcifying bacteria. SEM analyses showed that calcite is a bacterial product that forms a very tight bond with a cement gel and that calcite fills visible cracks and voids and creates more of a void-free and undamaged concrete structure.

Investigation of Crack Repairing Technique to Delay Fracture Initiation of Steel Members Subjected to Low Cycle Fatigue

Stress concentrations have become a common phenomenon in steel elements when arresting a fracture by implementing the crack stop hole (CSH) technique. Embedding the CSH with Carbon Fibre-Reinforced Polymer (CFRP) enhances the fatigue life by delaying fractures while achieving stiffness recovery due to the superior mechanical characteristics of the CFRP material. Hence, the low cyclic fatigue (LCF) behaviour of 90 strengthened and non-strengthened CSH specimens was examined in this context. These specimens were subjected to a range of 0 to 10,000 fatigue load cycles at a frequency of 5 Hz. At the end of fatigue exposure, the average tensile strength was measured in each case. The application of a CFRP patch on the CSH effectively recovered the strength losses while enhancing the strength in the range of 32% to 45% with respect to the non-strengthened specimens. The developed numerical model based on the cyclic J-integral technique agrees with the test results. This study introduced geometry-related design guidelines for this novel CSH hybrid technique.

Effect of Propolis on Fungal Infection for Denture Wearers and Dry Socket

Propolis is consist of various amounts of resins and beeswaxes that produced by the honeybees from different natural plants, as leaf buds and flowers. It is a sticky and dark-brown color material that produced by honey bees from natural plants that the bees mixed it with wax and applied it in building, construction and adaptation of the nests specially in repair cracks and defects in the bees hive. They have been used in medical folk or medical traditional since times of ancient. It is now known to be natural medical treatment with, antifungal, antibacterial, antioxiditive, antitumor and mmunomodulatory properties. These medical properties of propolis are motivating isolation researches, identification of the possible relationship of these with its biological activity, and chemical compounds. It was used in dentistry for healing of surgical wound (or post-surgical mouth pain), tooth hypersensitivity, pulp capping and root canal treatment. Propolis has a promising goal in future medically. This research shows the application of propolis, clinically, as a natural dental medicine. Furthermore; systemic and clinical applications of these drugs may have some adverse effects like liver toxicity, drug interactions etc. Using propolis as antifungal by local application shown that it reduces the incidence of dry socket and denture stomatitis that associated with the Candida. In present study, the propolis has been used in the following manner. It is applied to the tissue surfaces of dentures, two times daily for two weeks. Propolis putty can also applied to dry socket cases after complete debridement and irrigation of it. The results showed after use propolis that the signs and symptoms including pain, redness and inflammation areas related stomatitis were gradually disappear, after 2 to 14 days the denture stomatitis is healing by using a propolis paste. Propolis putty has an effect on the fungal infection of dry socket that gradually reduced pain and inflammation until complete healing. Aim of the study, after the treatment of patients with denture stomatitis, they were subjected to examination and evaluation of the mucosa and socket, Candidal quantitative cultures and confirmation the diagnosis by three methods: Germ tube, Gram Stain, and ChromAgar media.

Simulation and Experimental Investigation of Multi-Step Shot Peening for Surface Crack Repair in Aluminum Alloys

This study explores the impact of shot peening residual compressive stress on repairing surface cracks in the 7075-T651 aluminum alloy. Two models were developed for crack repair via shot peening and fatigue test finite element modeling. A multi-step numerical simulation introduced shot peening-induced residual stress into the fatigue test model, and subsequent simulations analyzed the crack repair mechanism. The research results indicate that increasing pressure and projectile size improve repair effectiveness, but higher pressure causes material damage, and larger projectiles decrease fatigue life. Crack repair effectiveness decreased with higher loading levels, more significantly at higher loads. Experimental and simulation results matched well, validating the simulation model for shot peen repair processes and offering optimization possibilities.

Properties of High-Performance Materials for the Crack Repair of Segment Structures

In order to improve the crack repair effect of high-performance segment structure crack repair materials, in this paper, we used the orthogonal test research method of four factors and three levels to analyze changes in the microstructure of crack repair materials under different material compatibility levels, followed by analysis through the performance testing of repair materials. The flow performance, setting time, compressive and flexural strength, and bonding and tensile strength were studied. The results show that (1) excessively thick epoxy polymer film affects the bond strength, an appropriate increase in the polymer–cement ratio can promote the hydration of cement, and an appropriate increase in gel material can enhance the repair function of repair material; (2) the setting time clearly increases with increases in the polymer–cement and water–cement ratios and the decrease range clearly increases with an increase in the water–cement ratio; (3) the adhesive flexural strength of epoxy polymer repair material increased the most in 28 days; and (4) the bonding tensile strength of the repair material increases first and then decreases with increases in epoxy polymer content. An appropriate increase in the polymer–cement ratio can promote cement hydration.

Some Approaches to the Repair of Cracks in the Concrete of Hydraulic Structures

Some Approaches to the Repair of Cracks in the Concrete of Hydraulic Structures

Study on the effects of different polymicrobial environments on b. Pasteurii survivability, urease activity, and crack healing

Microbially induced calcite precipitation technology for healing microcracks is currently a prominent topic in the field of construction materials. The objective of this study was to assess the efficacy of crack repair in diverse polymicrobial environments and propose a novel auxiliary mechanism for enhancing survival performance, crack healing ability, and recovery rate of mechanical properties in such environments. The results suggest that the presence of a polymicrobial environment negatively affects Bacillus Pasteurii. The novel auxiliary mechanism could increase the urease activity up to 1.875 times and the number of fully healed cracks reached 18/20, which is 1.35 times higher than the previous method. In addition, the effect of different salt solutions (NaCl, KCl, Na3PO4 and Na2SO4) on the survival properties of Bacillus Pasteurii was investigated. The optimal NaCl concentration for survival ranges from 0.3 to 0.9 mass%, excessive levels of K+ (0.3 mass%) can be harmful or even lethal to the cells. Additionally, an excess of PO43− and SO42− inhibits the multiplication of Bacillus Pasteurii and reduces urease activity.

Toughening, reinforcement and repair mechanisms of TiSi2 in Al2O3/TiN/TiSi2 ceramics

The short sintering time of discharge plasma sintering (SPS) can effectively improve the research efficiency. Through the self-repair phenomenon, ceramic materials can repair surface cracks and improve their reliability. In this study, self-repairing ceramic materials—Al2O3/TiN and Al2O3/TiN/TiSi2—are prepared through SPS and surface crack-repair experiments are performed under different heat-treatment conditions to determine the optimum sintering parameters and analyse the surface crack repair effects. The effects of TiSi2 on the toughening, strengthening, and repair mechanisms of Al2O3/TiN ceramics are analysed. The results show that the bending strength and fracture toughness increase by 25.20 and 4.42 %, respectively, with the addition of TiSi2. The increase in the bending strength is due to the decrease in the sintering temperature and grain refinement. The fracture toughness increases because the addition of TiSi2 increases the crack deflection and bridging. TiSi2 forms an oxide layer on the ceramic surface, which prevents the contact between oxygen and cracks, thereby reducing the porosity of the repaired surface of the Al2O3/TiN ceramic material.

Experimental study on the influence of cracks on tunnel vibration under subway train load

The impact of train vibration on the tunnel lining is a popular research topic. Under long-term train operation, the tunnel lining may incur damage, mainly longitudinal cracks, which will further increase the vibration caused by running trains, impacting the lining and the surrounding soil and eventually endangering the safety of train operation. To understand the influence of cracks on tunnel vibration under train load, we performed a model test of a shield tunnel with and without typical cracks based on a line of Hangzhou metro prototype to characterize its dynamic responses under train vibration loads. To simulate the tunnel lining material, the tunnel segment was lined up with polymer cast nylon with low creep rate and high strength. An inverted shaker simulated the train vibration load, and an accelerometer was used to measure the dynamic response of the tunnel structure and the surrounding soil. The results show that the dynamic response of the cracked section is significantly larger than that of the intact section, and due to the propagation characteristics of vibration, the expansion effect inside the tunnel is significantly greater than that of the surrounding soil. When the frequency spectrum results of the tunnel structure and the surrounding soil are compared, it is found that the vibration level of the surrounding soil due to cracks is mainly concentrated at around 100 Hz, while that of the tunnel structure at around 315 Hz, indicating that the cracks have a targeted effect on the expansion of the dynamic response. Meanwhile, the excessive vibration of intact segments is –2 or –1 dB, and the existing vibration reduction measures can meet the damping requirements. However, the excessive vibration caused by typical cracks can go up to 12 dB. Therefore, corresponding vibration reduction measures should be taken according to specifications. Finally, this paper proposes some vibration reduction suggestions and crack repair measures.

Preparation and performance of sugarcane bagasse ash pavement repair mortars

Pavement rehabilitation is typically required to ensure the service life of the road and the safety of road traffic. Due to various environmental and loading factors, pavements can present degradation or failures along their length, such as cracks, fissures, deformations, and disintegration of the wearing course. One way to reapair these defects is by using sealant materials. The objective of this research is to design mortars with sugarcane bagasse ash as a substitute for sand for the repair of cracks in pavements. Compression, tensile, shrinkage, fluidity and adherence tests were carried out on mortar samples that varied their dosage with 0 %, 50 % and 75 % ash content as a substitute for sand. These tests allowed for the evaluation of the physical and mechanical properties of the samples, determining compressive strength values of 16.65 MPa, adhesion of 0.52 MPa, among others. The control mix 5 with a 50 % replacement of ash by sand (M5–50 %), obtained the best results under the criteria of each of the tests performed. This article also evaluates the environmental impact of construction materials using the established procedures, finding that considering sugarcane bagasse ash as waste, using recycled polypropylene fibers, and incorporating zeolite for carbon capture can reduce the carbon footprint of concrete by up to 50 % compared to baseline mixes.

Preparation of the geopolymer grouting material by coal-based solid wastes for the aquiclude key strata and its application

The application of grouting to repair cracks in the key strata of the aquiclude is an effective measure to safeguard the overlying aquifer during underground coal mining. However, conventional grouting materials are expensive and can induce serious environmental pollution. In this study, a cost-effective geopolymer grouting repair material was prepared by using coal gangue, fly ash, bentonite, and other additives. The response surface methodology was employed to design the compressive strength and seepage strength tests on the cemented body, and the microstructure of the cemented body was also explored. The results show that when the ratio of coal gangue to fly ash to bentonite is 23:22:5 and the NaOH content is 4 %, the optimal performance of the grouting material is achieved, with a compressive strength of 10.11 MPa and a seepage strength of 2.38 MPa at the curing age of 28 d. The compressive strength and seepage strength of the grouting material are significantly improved by the network structure formed by the cross-linking of ettringite generated from the hydration of the material and the gel of sodium silicate hydrate.

Investigation on the working performance of a non-dispersible grouting material for the crack repairment of underwater structures

Underwater structure repair is highly susceptible to various factors, including the pressure of the underwater environment and dynamic water flow. Traditional materials used for repairs are prone to dilution and dispersion, resulting in a subpar repair outcome. To address the limitations of traditional grouting materials, specifically their poor retention rate and vulnerability to erosion caused by dynamic water, an underwater non-dispersible crack repair grouting material was developed. It is composed of liquid epoxy resin, curing agent, and aggregate (ECA). Comprehensive and systematic testing was conducted to evaluate the performance of ECA grout. The results show that optimized ECA grouting material has advantages such as a high retention rate under dynamic water erosion, strong adhesion, high fluidity, high early strength, and suitable setting time. The ECA grout demonstrates excellent underwater working performance. In addition, the microstructure was analyzed using X-ray diffractometry (XRD), Fourier-transform infrared spectroscopy (FTIR), and environmental scanning electron microscopy (ESEM). The results show that the addition of aggregates to the epoxy resin does not cause any chemical reaction. Furthermore, the aggregates are bonded together by epoxy resin. Due to the formation of cross-linked microstructures, the microstructure becomes more compact. The addition of aggregates during the curing process has good compatibility and stability, which enhance the performance of the ECA grout. The material has been successfully applied in a restoration project of underwater cultural relics protection facilities, effectively addressing and repairing the existing defects. Its potential value as a reference for similar projects is substantial.

Effects of emulsified asphalt on the rheological behaviors of magnesium phosphate cement

The traditional method for repairing asphalt pavement relies on hot-mix asphalt. Owing to its high energy consumption, this method proves inadequate in meeting the growing demands of low-carbon and environmental protection. Further, the utilization of cold-patching material is limited due to its slow strength development and poor long-term durability. Therefore, in this study, an organic–inorganic composite system that is based on the addition of emulsified asphalt and magnesium phosphate cement (MPC-EA) for filling asphalt pavement cracks was developed. Since the rheological properties of the slurry play a crucial role in determining its suitability for injection into the area to be reinforced and the effectiveness of crack repair, the effect of EA content on rheological properties was investigated. Specifically, the rheological properties of the slurry were analyzed at 260 s, and the rise in hydration temperature during this period was monitored to better understand the hydration process. The addition of EA drastically influenced the shear thickening of the original MPC system, and the rheological parameters changed with an increase in the EA content (10%–40%). The rheological loss mechanism of the composite system was elucidated by studying the hydration temperature and rheological parameters of the MPC-EA composite system. Further, an early rheological model of the composite system was established to understand the interaction mechanism of the MPC-EA composite system, and a constitutive equation of MPC-EA that considers the influence of EA content was devised. This study provides valuable information that can facilitate the field application of novel repair materials for pavement crack repair.

A Novel Mathematical Model for Repairing Rough Cracks Using the Microbially Induced Carbonate Precipitation (MICP)

Concrete cracks have an adverse effect on the strength properties and durability of concrete structures. Therefore, repairing concrete cracks to recover the concrete’s strength parameters is an important task in the civil engineering field. For repairing concrete cracks, the MICP technique has been widely analyzed in recent times; however, no research has been conducted to deeply investigate the repair effects of MICP on concrete cracks with a rough surface using a theoretical model. In the current research, MICP with a novel mathematical model was conducted considering the precipitation of calcium carbonate (CaCO3), ureolysis, suspended biomass, geochemistry, transport of solutes, and biofilm growth. Furthermore, crack repair experiments were performed to assess the performance of the new mathematical model. The results revealed that the calculated concentrations of suspended biomass in cracks gradually decreased during the test. The comparison between the experimental results and calculated results verified the precision of the migration behavior of the suspended biomass. At the inlet, the solute concentrations and volume fractions of biofilm were higher, causing an increase in the productive rates of calcium carbonate. The consumed concentrations of solutes were higher for cracks with a smoother surface, eventually leading to smaller values of sonic time; the upper parts of the cracks also had smaller values of sonic time, showing good repair effects. The proposed mathematical model provides a better solution to control the repair time and microbial metabolism process, allowing for adjustive bioremediation and biomineralization of concrete, which could provide a firm basis for the remediation of materials in the civil engineering field.

Studying the Mechanics of NMC Cathode Particles for Direct Battery Recycling

As the global usage of lithium-ion batteries skyrockets, there is increasing interest in recycling spent batteries. While the economic and environmental impacts of reclaiming high-value elements such as cobalt, nickel, and lithium are obvious, directly-recycling cathode materials takes this one step further by both recovering these elements as well as preserving particle structure, which takes significant processing cost and materials to manufacture. Previous literature has found a correlation between mechanical strength and cyclability of cathode materials, indicating that restoring the structural integrity of active particles is crucial to direct recycling efforts [1, 2]. Cathode materials experience significant fracture and cracking during the lifetime of a battery, caused by both the calendering process during formation and the volume expansion of the particles upon lithium insertion during cycling [1]. Many recycling processes rely on high-temperature annealing to repair cracks in end-of-life cathode particles. As fracture due to calendering exists in pristine electrodes, it is possible that the annealing step does not need to heal all cracks in end-of-life material to match pristine electrode performance. To lower recycling costs, it is vital that the requirements for the annealing step are well understood.To address this, we characterize the mechanical strength of nickel manganese cobalt (NMC) cathode particles at pristine, end-of-life, and recycled-annealed states. We leverage multiple experimental techniques, including bulk compressive testing, nanoindentation, and nano-CT measurements, to characterize the particles’ bulk modulus, Weibull distribution, and fracture toughness, among others, and correlate these mechanical properties to cycling performance. From this, we provide insight into an optimal annealing step that minimizes cost without sacrificing recycled material mechanical and electrochemical quality.

Lane Crack Detection Based on Saliency

Lane cracks are one of the biggest threats to pavement conditions. The automatic detection of lane cracks can not only assist the evaluation of road quality and quantity but can also be used to develop the best crack repair plan, so as to keep the road level and ensure driving safety. Although cracks can be extracted from pavement images because the gray intensity of crack pixels is lower than the background gray intensity, it is still a challenge to extract continuous and complete cracks from the three-lane images with complex texture, high noise, and uneven illumination. Different from threshold segmentation and edge detection, this study designed a crack detection algorithm with dual positioning. An image-enhancement method based on crack saliency is proposed for the first time. Based on Bayesian probability, the saliency of each pixel judged as a crack is calculated. Then, the Fréchet distance improvement triangle relationship is introduced to determine whether the key point extracted is the fracture endpoint and whether the fast-moving method should be terminated. In addition, a complete remote-sensing process was developed to calculate the length and width of cracks by inverting the squint images collected by mobile phones. A large number of images with different types, noise, illumination, and interference conditions were tested. The average crack extraction accuracy of 89.3%, recall rate of 87.1%, and F1 value of 88.2% showed that the method could detect cracks in pavement well.

Exploring a high-urease activity Bacillus cereus for self-healing concrete via induced CaCO3 precipitation.

The structural integrity and esthetic appeal of concrete can be compromised by concrete cracks. Promise has been shown by microbe-induced calcium carbonate precipitation (MICP) as a solution for concrete cracking, with a focus on urease-producing microorganisms in research. Bacillus cereus was isolated from soil and employed for this purpose in this study due to its high urease activity. The strain exhibited strong tolerance for alkaline media and high salt levels, which grew at a pH of 13 and 4% salt concentration. The repair of concrete cracks with this strain was evaluated by assessing the effects of four different thickeners at varying concentrations. The most effective results were achieved with 10g/L of sodium carboxymethyl cellulose (CMC-Na). The data showed that over 90% repair of cracks was achieved by this system with an initial water penetration time of 30s. The study also assessed the quantity and sizes of crystals generated during the bacterial mineralization process over time to improve our understanding of the process. KEY POINTS: • MICP using Bacillus cereus shows potential for repairing concrete cracks. • Strain tolerates alkaline media and high salt levels, growing at pH 13 and 4% salt concentration. • Sodium carboxymethyl cellulose (CMC-Na) at 10g/L achieved over 90% repair of cracks.

The influence of repair technique on the distribution of biogenic CaCO3 in a mimic vertical crack

Microbially induced carbonate precipitation (MICP) is a promising solution for the remediation of concrete cracks. It has great advantages of environmental compatibility and exceptional penetration of cracks owing to its low-viscosity solution. Despite of these, practical application of MICP has been hindered by challenges including limited efficiency of in situ microbial deposition of CaCO3, extended repair cycles, and suboptimal strength recovery. Addressing these issues, this study undertook a comprehensive exploration of key repair process parameters for repairing cracks within the simulated crack space through inducing CaCO3 precipitation by a urease producing bacteria, specifically, the flow rate of the repair agents (7.958, 15.91, and 39.79 μL/min), the pre-sealing length of the crack (one-third of the crack length, half of the crack length, and full sealing), and the injection port position (upper, middle, and bottom of the crack). Their impacts on the distribution of bio-CaCO3 and overall repair effectiveness were examined in detail. Optimal repair performance was achieved at a flow rate of 15.91 μL/min, with full crack sealing, and the injection port situated at the bottom. This configuration resulted in a remarkable coverage rate of crack side wall, crack surface repair rate, and crack volume filling rates of 94.38%, 79.48%, and 100% respectively, and the first two were calculated using Image J software. The crack repair depth was significantly improved. Relative contribution rates to repair effectiveness was found to be ranked as follows: injection port position > flow rate > pre-sealing length. This study provides critical insights into the optimization of MICP repair process parameters, presenting a significant advancement in the understanding and development of effective techniques for concrete crack repair.

Experimental Research into the Repair of High Temperature Damage to Cement Mortar Samples Using Microbial Mineralization Technology

Experiments such as microbial activation culture, subculture selection, and fire damage repair of cement mortar specimens were conducted to investigate the repairing effect of Sporosarcina pasteurii as a repair agent for fire-damaged cracks in cement mortar specimens. In addition, multi-scale parameters such as compressive strength and chloride ion migration coefficient of cement mortar specimens before and after restoration were compared. The effect of microbial mineralization technology on the repair of fire-damaged cracks in cement mortar specimens was investigated, and the microstructure and mineral composition of the products were analyzed. The results showed that the strong alkaline environment in the cracks of the cement mortar specimens after a high temperature of 500 °C inhibited the activity of bacteria and weakened the mineralization effect; the compressive strength of the repaired cement mortar specimens was 22.8% higher than that of the unrepaired fire-damaged specimens; the compressive strength of the repaired cement mortar reached 78.2% of the strength of the original cement mortar specimen without high temperature; after restoration, the chloride ion penetration resistance of the cement mortar specimens decreased by about 16.9% compared with that before restoration.