Repair Of Concrete Structures Research Articles

Air-coupled ultrasonic mapping of stimulated autogenous self-healing and repair effectiveness within concrete mixtures

Due to the high risk of cracking, the adequate repair of concrete structures has become equally important to the design of cementitious mixtures. As these repairs should provide a certain level of safety to the user, the assessment of the regained performance needs to be confirmed. Air-coupled ultrasound combines a non-destructive character together with a fast and easy application. Within the present study, two main objectives are pursued. One is the use of air-coupled receivers as a step towards a fully non-contact methodology. Additionally, the effectiveness of air-coupled ultrasonic mapping is applied to both self-healing mixtures and manually repaired specimens. Additionally, two different ultrasonic frequencies are adopted. The results show that air-coupled ultrasonic mapping enables to monitor the processes of cracking, self-healing and repair within the entire cross-section through a point-by-point measurement. Moreover, the use of different frequencies demonstrates the increased sensitivity of the higher frequencies to follow-up these mechanisms. Lastly, from the material point of view, the mixture with 1% SAP revealed the highest self-healing capacity, whereas the manual repair through polyurethane was superior to all self-healing blends.

Enhancing bonding behavior between basalt fiber-reinforced polymer sheets and concrete using resin pre-coating method and multi-wall carbon nanotubes

There is a crucial problem of premature debonding failure in fiber-reinforced polymer (FRP) sheet external bonding reinforcement for concrete structures. Using anhydrous ethanol as solvent instead of acetone, the effect of resin pre-coating (RPC) technique with neat resin-ethanol solution and multi-wall carbon nanotubes (MWCNTs)-resin-ethanol solution on the bonding behavior of the FRP-concrete joints was investigated by single-shear tests. Experimental results indicated that RPC technique significantly enhanced the bonding properties, especially when the pre-coating was MWCNTs-resin-ethanol solution. In the case of using neat epoxy resin as adhesive, compared with the control specimens without RPC treatment, the ultimate bearing capacity, ultimate global slip, maximum bond stress and interface fracture energy of the basalt fiber-reinforced polymer (BFRP)-concrete joints using RPC treatment with MWCNTs-resin-ethanol solution increased by 32.6 %, 48.4 %, 68.3 % and 88.8 %, respectively. MWCNTs could be seen in scanning electron microscopy (SEM) images of the fracture surface, which indicated that they could penetrate into the concrete and the crack bridging and pull-out of MWCNTs could enhance the interfacial adhesion of the FRP-concrete joints. Compared with the RPC treatment using the restricted acetone, the RPC treatment with MWCNTs-resin-ethanol solution can more significantly enhance the bond properties of the interface between concrete and FRP sheet, and it is suitable for large-scale practical engineering applications on site. This study demonstrated the great promise of the RPC technique with MWCNTs-resin-ethanol solution toward practical engineering application in reinforcement and repair of concrete structures.

Explorative Study into Alkali-Activated Repair Mortars Using Blast Furnace Slag and Glass Waste

The repair of concrete structures is increasing in prevalence. Conventional repair mortars are expensive materials rich in Portland cement (PC) and other organic and inorganic components that question their economic efficiency and carbon footprint. Alkali-activated materials (AAMs) are an eco-friendly alternative to PC that possess properties desirable for repair mortars. The article presents the mix design, mechanical, bond, and shrinkage properties of alkali-activated binary mortars intended for structural concrete repair. Mix optimisation based on mechanical properties of repair mortar and utilisation of glass waste (GW) is presented together with total and restrained shrinkage, pull-off bond tests, and life cycle assessment (LCA) for selected configurations. Results demonstrate good compressive and flexural strength, exceeding 45 N/mm2 and 7 N/mm2, an excellent pull-off bond strength (1.8–2.3 N/mm2) of the alkali-activated mortar to the concrete substrate, in spite of extensive shrinkage, with an order of magnitude of a couple of thousands of microstrains, which is also reported. Shrinkage appears to increase with the increase of the applied GW in the mixture. LCA revealed that alkali-activated mortars have up to 54% lower CO2 eq. emissions compared to PC-based repair mortar.

Paper waste grown as a biocalcified foam: perspectives from a bacterial and design viewpoint

Abstract Biocalcification is a naturally occurring mineralisation phenomenon resulting from the urease produced by microorganisms inhabiting soil environments. This process, often referred to as microbially induced calcite precipitation (MICP), is primarily exploited in an engineering context for soil stabilisation and the repair of concrete structures. MICP represents an emerging area of research in architecture and design. In this paper, we discuss the appropriation of MICP on Papier Plume, a foam made of paper waste used in the context of ImpressioVivo: a design-led research project exploring the conception and fabrication of 3D-printed and bacterially induced bio-sourced materials for a circular design framework. In the light of a previous study based on two strategies of calcification: (1) direct inoculation (2) spraying, we – a team of two designers and a microbiologist – discuss the relevance of an immersion strategy applied to the dry paper foam substrate. By doing so, we reflect on the relevance of MICP as a material design process underpinned by sustainable and circularity concerns, from a design perspective, but also into an attempt to embrace the perspective of the bacteria supporting these experiments; namely Sporosarcina pasteurii.

Experimental Investigation Properties of Reinforced Cement Concrete with Partial Replacement of Cement by Metakaolin Clay and Structural Health Monitoring Using Sensor

Abstract: Cement concrete is the most extensively used construction material. Maintenance and repair of concrete structures is a growing problem involving significant expenditure. As a result carried out worldwide, it has been made possible to process the material to satisfy more stringent performance requirements, especially long–term durability. HPC is the latest development in concrete. It has become very popular and is being used in many prestigious projects such as Nuclear power projects, flyovers multi-storeyed buildings. When using HPC, the addition of supplementary materials in cement has dramatically increased along with the development of concrete industry, due to the consideration of cost saving, energy saving, environmental concerns both in terms of damage caused by the extraction of raw materials and carbon dioxide emission during cement manufacture have brought pressures to reduce cement consumption. Metakaolin looks to be a promising supplementary cementations material for high performance concrete. Properties of concrete with metakaolin is mostly preferred additives in high performance concrete. A possible lower cost, due to large availability in our country itself may be advantages to metakaolin usage in HPC. The substitution proportion of metakaolin is to be used was 5%, 10%, 15%, 20% by the weight of cement. To make this cubes and cylinders to determine the strength and durability of concrete of it. A multitude of structural health monitoring options are currently being investigated to address the reliability of concrete infrastructures at different stages of their service life. This review presents the recent achievements in the field of sensors developed for monitoring the health of concrete infrastructures. The focus of this review is on sensors developed for monitoring parameters including temperature, humidity, pH, corrosion rate, and stress/strain and the sensors particularly fabricated based on fiber optic, Bragg grating, piezoelectric, electrochemical, wireless and self-sensing technologies. Several examples of developed concrete monitoring sensors (from laboratory concepts to commercialized products) together with their various benefits and drawbacks as well as open research problems will be discussed in this project.

Fiber reinforced sulphoaluminate cementitious composites: Mechanical properties and comprehensive evaluation method

The rapid repair of concrete structures is an important research subject, which has attracted the attention of engineers at home and abroad. Here, an early-strength and strain, fast-setting and fast-hardening cementitious composite named as fiber reinforced sulphoaluminate cementitious composites (FRSACC)was developed. The mechanical properties of FRSACC were investigated through a series of experiments, including compressive strength, flexural strength, uniaxial tensile performance, four-point bending performance, three-point bending fracture, and microstructure analysis. The results indicated that these properties were influenced by the curing age, water to binder (W/B) ratio, sand to binder (S/B) ratio, and fly ash (FA) dosage. To be specific, the W/B ratio plays a vital role in achieving desirable mechanical properties at early curing stage, followed by the FA dosage and the S/B ratio. In addition, a facile six-dimensional representation was proposed to assess the overall performance of FRSACC. This comprehensive evaluation method can also be used for other cementitious composites to evaluate and select the better mixture ratio based on mechanical properties, bending toughness and fracture toughness.

Repair concrete structures with high-early-strength engineered cementitious composites (HES-ECC): Material design and interfacial behavior

Aimed at realizing the effective strengthening and durable repair of concrete structures, particularly in emergencies like traffic interruption triggered by broken roads and damaged bridges, nine groups of specimens were designed and tested in this paper to develop the high-early-strength Engineered Cementitious Composites (HES-ECC) featured as both high early-strength and superior long-term-deformability. The high-early-strength effect of sulphoaluminate cement, silica fume, and Portland cement on HES-ECC was compared, as well as their influence on the deformation ability of HES-ECC. Moreover, the interfacial behaviors between HES-ECC and existing concrete structure were clarified, considering the effects of interfacial agents, interfacial treatment methods, and interfacial roughness. The results indicate that HES-ECC with 6% silica fume mixed could obtain both the high early-strength and superior long-term-deformability. The flexural strength at 3 h could reach 66.67% of that at 28d. The compressive strength could reach up to 28.7 MPa at 3 h, and the ultimate tensile strain could remain 4.21% at 28d. Cement paste interfacial agent could enhance the chemical adhesive bonding between HES-ECC and existing concrete while polymer modified interfacial agent was incompatible. The increased roughness of chiseled interface was beneficial to both the bearing capacity and the deformation ability. Interfacial shear performance of the grooved interface was scarcely deteriorated even if the roughness decreased by 54.18% compared with the chiseled interface. The recommended interfacial treatment is chiseled interface combined with grooved interface, as well as a thickness of 1–2 mm cement paste interfacial agent. This study provides valuable and credible experimental data for promoting the application of HES-ECC in repairing existing concrete structures in practice.

Experimental Study on Influence of Bacteria in Concrete

Abstract: Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens over time. The elasticity of concrete is relatively constant at low stress levels but starts decreasing at higher stress levels as matrix cracking develop. Therefore, it is important to control the crack width and to heal the cracks as soon as possible. Since the costs involved for maintenance and repair of concrete structures are usually high, apart from conventional methods of repairing cracks with sealants or treating the concrete with adhesive chemicals to prevent the cracks from widening, a microbial crack healing approach has shown promising results and this research focuses on the development of self-healing concrete. Self-healing of cracks in concrete would contribute to a longer service life of concrete structure and would make the material not only more durable but also more sustainable

Underwater Repair of Concrete Elements with TRC Grouting System.

The repair of underwater concrete structures is usually difficult work, requiring specialized materials and installation systems. This paper presents a carbon-textile-reinforced concrete (TRC) grouting system for underwater repair of concrete structures. One multi-purpose grout and two types of underwater grouts were considered in this study, and the bond performance between the substrate and grout was evaluated by a bi-surface shear test with cubic specimens. The bond strength of the repair material is greatly affected by the casting and curing conditions. When the multi-purpose grout is used, the average bond strength of the specimens cast and cured in dry conditions is only 22% of the specimens cast and cured in underwater conditions. On the other hand, the maximum difference in bond strength is, at most, 15.8% when non-dispersive, anti-washout grouts are used. Two types of installation methods were proposed and four full-scale RC slab specimens were repaired with the TRC grouting method, two for each installation method. Regardless of the installation method, the load levels that causes concrete cracking, steel yield, and the failure of specimens repaired with the TRC grouting system are at least 37.5%, 16.6%, and 21.7% greater than those of the unrepaired specimen, respectively. The test results further indicate that the influence of the grouting materials on the ultimate load-carrying capacity of the specimens repaired with the TRC grouting system is insignificant, and the maximum difference is, at most, 4%.

Sulfate Freeze-Thaw Resistance of Magnesium Potassium Phosphate Cement Mortar according to Hydration Age.

Concrete structures can be degraded by exposure to environmental stressors such as freeze–thaw cycling and salt corrosion. Magnesium potassium phosphate cement (MKPC) mortar is useful for the rapid repair of such structures but must acquire environmental resistance rapidly. In this study, the freeze–thaw resistance of MKPC mortar specimens of different hydration ages was tested in water and a 5% Na2SO4 solution. The strength, volume deformation, and water absorption rates were compared with those of full-age MKPC mortar specimens (28 d). The phase composition and microscopic morphology of the MKPC mortar specimens before and after corrosion were observed, and the corrosion-resistance mechanism was analyzed. After 225 freeze–thaw cycles in water and sulfate solution, the strength residual rates of the early-age specimen (1 d) were higher than those of the full-age specimen (28 d). The degree of strength attenuation in the 1 d specimen was lower in the sulfate environment than in the water environment. After 225 freeze–thaw cycles, the volume expansion rates of 1 d specimens in water or sulfate were 0.487% and 0.518%, respectively, while those of 28 d specimens were 0.963% and 1.308%. The comparison shows that the 1 d specimen had significantly better deformation resistance under freeze–thaw than the 28 d specimen. After 225 freeze–thaw cycles, the water absorption rates of 1 d specimens were 1.95% and 1.64% in water and sulfate solution, respectively, while those of 28 d specimens were 2.20% and 1.83%. This indicates that freeze–thaw cycling has a greater effect on the pore structure of fully aged mortar than on early-age mortar (1 d). Therefore, MKPC mortar is suitable for the rapid repair of concrete structures in harsh environments. The results form a theoretical basis for winter emergency repair projects. They also further the understanding of the application of MKPC-based materials in extreme environments.

The Effect of Magnesium Chloride on the Macroscopic and MI-Croscopic Properties of Phosphate Cement-Based Materials

Phosphate cement-based materials are fast-hardening cement materials, which have been applied to the rapid repair of concrete structures. However, the excessive setting rate could lead to initial cracks in the cement-based matrix. Therefore, a proper retarder is required to reduce the setting rate, thus improving the strength of structures. In this study, a magnesium chloride retarder was selected, and its influence on the setting time, slump flow, and the mechanical strengths (flexural strength, compressive strength, and bond strength) of phosphate cement paste curing for 3 h~28 d was investigated. Scanning electron microscopy, X-ray diffraction, and thermal analysis were used to analyze the mechanism of the properties of phosphate cement paste. Results showed that the setting time increased exponentially with the mass ratio of magnesium chloride by the total mass of magnesium oxide. Meanwhile, the slump flow increased linearly with the increasing dosage of magnesium chloride, and the drying shrinkage rate exhibited a quadratic function with the curing age. The addition of magnesium chloride decreased the mechanical strengths of phosphate cement paste at earlier curing age (lower than 3 d) and effectively improved the mechanical strengths at a later curing age (equal to or higher than 3 d). Moreover, magnesium chloride could also decrease the drying shrinkage rate. It can be obtained from the microcosmic researching results that magnesium chloride can inhibit the hydration of phosphate cement and reduce cracks induced by drying shrinkage at later curing age (higher than 3 d).

Состояние и перспективы развития мелиорации в Амурской области

The reclamation complex of the region, after a long period of uncertainty, is among the priorities of agricultural development. The article deals with the problems of land reclamation, which acts as a means of ensuring the sustainable development of the agro-industrial complex of the region, since land reclamation plays a crucial role in increasing the fertility of developed lands and crop yields. However, reclamation systems need constant maintenance. It is noted that forest reclamation is insufficiently developed in the region. The purpose of the study is to analyze the current state of land reclamation in the Amur region. The study was conducted in 2018 – 2021 in the Amur region. It has been established that the majority of reclamation systems are in unsatisfactory condition due to a long service life, lack of repair and maintenance, as well as great wear and tear. As a result of the conducted research, the necessity of restoration and reconstruction of the reclamation systems of the region was established. The ways of development of land reclamation on the basis of restoration, repair, reconstruction and construction of new land reclamation systems are outlined. An example of the reconstruction of the reclamation Gilchinsk drainage system and the results of this reconstruction are given, which are expressed in the fact that agricultural work began to be carried out in optimal agrotechnical terms, regardless of weather conditions, and farmers receive stable high yields of agricultural crops. It was noted that it became necessary to pay attention to the design and construction of land reclamation. The modern approach to the survey of reclamation systems, the main directions of repair of concrete structures of reclamation structures are considered. The subject methods of economics, ecology, principles: diversity of forms are used. To conduct this study, information data from websites and other open sources were used.

Numerical Simulation-Based Damage Identification in Concrete

High costs for the repair of concrete structures can be prevented if damage at an early stage of degradation is detected and precautionary maintenance measures are applied. To this end, we use numerical wave propagation simulations to identify simulated damage in concrete using convolutional neural networks. Damage in concrete subjected to compression is modeled at the mesoscale using the discrete element method. Ultrasonic wave propagation simulation on the damaged concrete specimens is performed using the rotated staggered finite-difference grid method. The simulated ultrasonic signals are used to train a CNN-based classifier capable of classifying three different damage stages (microcrack initiation, microcrack growth and microcrack coalescence leading to macrocracks) with an overall accuracy of 77%. The performance of the classifier is improved by refining the dataset via an analysis of the averaged envelope of the signal. The classifier using the refined dataset has an overall accuracy of 90%.

Flexural behavior of high ductility MPC-based composites under low-temperature curing

A high ductility magnesium phosphate cement-based composites (HDMC) was developed using polyvinyl alcohol (PVA) fibers and fly ash. In cold areas or winter, there is a need for the urgent strengthening and repair of concrete structures by using the HDMC, so the performance of the HDMC in low temperature environment needs to be explored to expand its application. In this study, the flexural behavior of HDMC under low-temperature curing was evaluated through the flexural test. The effects of fly ash (FA) content, sand/binder mass ratio (S/B), water/solid mass ratio (W/S), PVA fiber volume fraction (Vf), curing age, and curing temperature on the flexural behavior of the HDMC were examined. The results showed that as the FA content increased, the strength of the HDMC was gradually reduced, and the toughness and ductility exhibited the best at 30%. As the S/B increased, the strength, toughness, and ductility of the HDMC first increased up to the S/B of 0.2 and then decreased. With the increase of W/S, the toughness and especially the ductility of the HDMC were significantly improved, whereas the strength was reduced slightly. Also, the increase of Vf could improve the strength, toughness, and ductility of the HDMC. Generally, the HDMC mixture with 30% FA, 0.2 S/B, 0.14 W/S, and 2.0% Vf was the best. Besides, as the curing age increased, the toughness and ductility first increased and then decreased; and the strength and toughness could be higher when cured at 0 °C than −5 °C.

Dynamic Performance Evaluation of Concrete Building Using Low-Yield Point Steel Shear Panels

Steel shear walls are a novel component in the field of construction. It has been of special interest to structural engineers for the reinforcement of steel buildings for the recent decades. Its unique features have attracted more attention, and its features are economical, easy to implement, light weight compared to similar systems, high ductility, fast installation, high energy absorption, and a significant reduction in residual stress in the structure. All the reasons made researchers think about studying its use in the repair of concrete buildings. Because this system has a low weight, it does not add extra load to the structure, and even with its connections, it strengthens the beams and columns around it. The design of this system in concrete buildings does not seem to be economical except in the case of restoration. In this paper, preliminary explanations of the steel shear wall are presented for more familiarity, and in the following sections, the study of reinforcement and repair of concrete structures will be studied and its difference with the low-yield point will be considered. Finally, the test results will be reviewed. The results of this study show that LYP steel shear panels cause a lot of energy loss and absorption, which is very useful in the safety of buildings exposed to severe earthquakes.

Shear interfacial fracture of strain-hardening fiber-reinforced cementitious composites and concrete: A novel approach

For strengthening and repair of concrete structures, shear interfacial behavior between concrete substrate and strengthening materials (e.g., strain-hardening fiber-reinforced cementitious composites) is critical for the structural performance of concrete members. In this study, a novel approach for shear interfacial fracture of cement-based materials was proposed to achieve pure shear failure. The stress intensity factor of the bi-material double-edge notched specimen was analytically obtained for the first time. A numerical investigation was carried out to confirm the suitability of the proposed approach. Then, shear interfacial fracture tests between strain-hardening cementitious composites and ordinary concrete were conducted to demonstrate its feasibility and to determine the shear interfacial fracture toughness. Additionally, digital image correlation (DIC) technique was used to analyze the shear behavior of the bi-material interface. The proposed approach can be applied to evaluate shear interfacial behaviors of cement-based materials.

Effects of nano-modified polymer cement-based materials on the bending behavior of repaired concrete beams

Abstract As the use time of concrete structures increases, defects such as concrete cracks, corrosion and exposure of steel bars gradually appear, resulting in additional repair of concrete structures to increase their durability and life. In this article, the effects of nano-modified polymer cement-based materials as repair material on the bending behavior of repaired concrete beams were studied. Based on the moment, deflection, strain, surface quality and cracking development monitor of repaired concrete beams, the bending behavior of repaired beams with polymer, nano-modified polymer and fibers was compared and the failure mechanism of the beams was analyzed. The results showed that the nano-modified polymer cement-based materials are helpful in improving the performance of repaired beams, manifested by the increase in the ultimate bending moment and the significant improvement in the quality of the interface between repair and matrix concrete. Compared with polymer cement-based materials, nano-modified polymer cement-based materials result in a 27% increase in ultimate bending moment of the repaired beam and a 58% increase in cracking moment, while reducing the total number of cracks by 23% and the average width of cracks by 17% in the repaired beam. This article demonstrated the availability of nanomaterials for improving the loading behavior of structural components with polymer-modified cement-based materials.

Mechanical Properties of Grout Materials for Concrete Structure Repairs

This research studies about the characteristics of grout material used for repairs to concrete structures. The purpose of this test is to produce materials with optimum composition for use as alternative materials for grouting or retrofitting. Fresh properties testing is carried out in the form of checking the flowability value as a benchmark to determine the proportion of the mixture, in addition to the hardened properties tested in the form of water content, absorption value, specific gravity, unit weight, and initial rate of suction. The results of the fresh properties show that overall the material can be worked or applied. While the hardened properties test results show that RCFA shows quite good results compared to other types of grout material, this is indicated by the results of absorption, moisture content and initial rate of suction which is worth 0. Besides that the type of grouting RCFA also produces the highest compressive strength value that exceeds 100 MPa at 28 days. Type of grouting SSCG produces a compressive strength that is small enough that is below 10 MPa so it is recommended not to use this type of grouting to be applied to the repair of concrete structures.

Fragmentation Pattern and Removal Mechanism of Concrete Subjected to Abrasive Water Jet Impact

Abrasive water jet (AWJ) breaking technology is suitable for the maintenance and repair of concrete structures, generating minimal dust, low tool wear, and no vibrations or selective destruction. The failure features and mechanisms of concrete subjected to AWJ impact are fundamental issues of AWJ breaking technology, which are also related to the safety and quality of engineering construction. Based on computed tomography (CT), scanning electron microscopy (SEM), and image processing technology, this paper studied the fragmentation pattern and removal mechanism of concrete under AWJ impact. The general failure characteristics and crack propagation law of concrete subjected to AWJ impact were described through AWJ impact concrete tests. The spatial distribution of damage in concrete subjected to AWJ impact can be divided into the intensive action zone, the transition zone, and the weak action zone. The removal mechanism of AWJ was discussed by comparing the impact performance of a pure water jet (PWJ) system. The results indicate that abrasive particles can cause cliff-shaped fracture and lip-shaped distortion in the aggregate part and flat fracture surface in the matrix part. There is no obvious crack in the interfacial transition zone (ITZ) due to the weakening of the water wedge effect.

Corrosion resistance of Structural Steel using Waste Plastic Oil

The failure of reinforced concrete structures is due to various surface damage or structural damage. The common problem identified for the repair of concrete structures is mainly because of Corrosion. In order to prevent the steel from corrosion effect, the various methodologies are being adopted. Core-shell theory was used to protect the steel material from the effect of corrosion by the application of cobalt oxide with zinc oxide on silica and alumina layer. According to this theory, the formation of effective protective layer is made to behave an anticorrosive coating. The combined effect of core and shell compounds enhances the efficacy of properties as a film of coating material for the steel used in the construction industry. The present study is an attempt on coating the steel reinforcement used in the construction industry using plastic oil extracted from the waste plastic which possesses the property of adhesion and resistance against corrosion.