Progressive Cracking Research Articles

Recent Innovations in Nano Container-Based Self-Healing Coatings in the Construction Industry

:Globally, the maintenance and repair of infrastructure cost billions of dollars and impact the day-to-day life of people. Corrosion of infrastructure and metals used in the manufacture of goods and supplies is a major cause of deterioration in the construction industry. Nanocontainerbased self-healing coatings attract enormous scientific attention as they offer a wide range of applications in conjunction with long-lasting inhibition performance. These coatings prevent the rate of crack progression by releasing active agents from micro/nanocontainers in a controllable manner and heal crack, thereby mitigating corrosion. The potential of such coatings to heal local damage induced by climatic causes or by mechanical damage is a significant contributing factor to their desirability. This review is a comprehensive analysis of nanocontainers used to manufacture self-healing anticorrosive coatings as well as explains their self-healing mechanism. The technique used to develop nanocontainers such as layer-by-layer assembly of layered double hydroxide has been clarified. An attempt has also been made to cover the latest developments in the manufacture of nanocontainermediated self-healing corrosion coatings used in several construction industries.

Effect of matrix and hybrid reinforcement on fibre metal laminates under low–velocity impact loading

This study aims to investigate the effect of matrix and hybrid reinforcement on Low–Velocity Impact LVI behaviour of Fibre Metal Laminates FMLs. The matrix was epoxy and Poly–Vinyl Butyral PVB, while the reinforcement was produced by sandwiching 3D–woven jute core with plain–woven skin. The plain–woven fabric was made with jute, aramid and carbon fibres. A drop weight impact test was performed for the evaluation of LVI performance. The behaviour of different FMLs was determined by comparing the pattern of curves, cross–section of damaged samples, x–ray computed tomography and crack progression phenomenon. The epoxy–based FMLs showed poor LVI response and suffered perforation due to its brittleness. The PVB–based FMLs showed higher impact resistance due to high toughness and plasticity, and had a higher impact force, lower damage, and more residual deflection. Even PVB based 100% jute reinforced FMLs performed well than hybrid reinforced FMLs made with epoxy. The tomography analysis showed that the PVB had better characteristics to be used with hybrid reinforcement due to high toughness. Among the hybrid reinforcements, the aramid/3D–jute reinforcement offered high resistance to deformation as compared to carbon/3D jute reinforcement. The FMLs made with PVB and aramid/3D–jute reinforcement showed overall superior LVI performance.

Analysing shear strength of reinforced concrete beams using a meso-scale finite-element method

An analytical exploration of the effects of shear span-to-depth ratio on the shear strength of reinforced concrete beams was carried out using a meso-scale finite-element method. Prior to the numerical analysis, a method of defining concrete as meso-scale composites of multi-phases was described. The concrete was assumed to be a composite with three phases (aggregates, cement matrix and interfacial transition zone), and the material properties of each phase were applied for the numerical analysis. The shear failure behaviour of reinforced concrete beams was examined by the numerical model that was constructed, and the effect of span-to-depth ratio on shear strength was confirmed through these analyses. An investigation of cases where span-to-depth was less than 1.0 was also carried out. Moreover, the performance of the numerical model was evaluated by comparing the numerical results with the experimental results obtained from the model code and other researchers. It was confirmed that the application of a meso-scale finite-element method was appropriate for the study on the effect of span-to-depth ratio on shear strength and the occurrence and progress of bending and shear cracks.

Effects of CO2 curing treatment on alkali-silica reaction of mortars containing glass aggregate

In this study, the influence of CO2 curing treatment on the alkali-silica reaction (ASR) of mortar bars containing 100% recycled glass was investigated. The ASR expansion results according to ASTM C1260 demonstrated that a short period (3 h) of CO2 curing could fully suppress the ASR expansion. Apart from mechanical strength enhancement, reduced pH and permeability properties, it is interesting to note that the distribution of ASR gel in the CO2 cured specimen was totally different from traditional glass-induced ASR as reported in the literature. For CO2 curing treated specimen, the ASR gel which formed at the glass-cement interface instead of initiation at microcracks within the glass aggregate is identified as an important reason for the decreased expansion. With the reduction of calcium hydroxide (CH) in the cement matrix caused by CO2 curing treatment, silica could dissolve from glass surface and induced the ASR reaction. The swelling of the surface ASR gel applied inward pressure on the glass aggregate, reducing the aggregate cracking progression. In addition, these surface gels can possibly be partly accommodated by residual space in the interfacial transition zone (ITZ).

Investigation of crack detection properties of elastomer-based nanocomposites under cyclic strain loading with graphene and carbon black interaction filler

In this study, the synergistic effect created by adding Graphene (GE) nanoplatelets and carbon black (CB) fillers to the rubber matrix was used to determine the high stretchable sensor properties. GE and CB-filled rubber nanocomposite (HcN) strain sensors have been shown to detect and trace crack initiation and crack propagation of different sizes under cyclic loading. Tests were performed with four different crack sizes (0, 2.5, 5, and 10 mm) at five different strain levels (0%, 5%, 10%, 15%, and 20%) to determine the strain sensing performance of the specimens. The electrical response of HcNs under loading was measured with the four-point probe technique and recorded with a high-performance data acquisition system. The progression of external cracks created by scalpel on HcNs was examined by measuring electrical resistance changes caused by cyclic strain loading between 0% and 20%. The electrical response of 4 phr and 8 phr filled HcNs behaved qualitatively similar to each other, while 1 phr filled HcNs showed a significantly different response in terms of quality and quantity. In 4 phr GE-filled specimens, the resistance increase was changed steadily depending on the crack length, and unstable conditions occurred at 5 and 10 mm crack lengths at 1 and 8 phr GE filler ratios. The flexible and stretchable elastomer-based conductive strain sensing sensors, developed with the synergistic interaction of well-dispersed carbon-based fillers in the matrix, can detect and record damaged conditions caused by cyclic loading in many application areas.

Modeling the delamination failure under compressive loads in CFRP laminates based on digital image correlation analysis

Laminate composite materials such as CFRPs are highly susceptible to delamination, being one of the common failure modes in composite laminates. The combination of severe delamination with uniaxial compressive loads leads to the loss of stability and structure failure. In this study, the authors present an experimental and numerical analysis of this effect in laminates. A series of tests were carried out with four different specimens including delamination-free plates and plates with incipient delamination with different damage size and location. 3D Digital Imagen Correlation technique was applied to predict the buckling initiation and propagation and to validate the numerical models implemented, showing good agreement between the numerical and experimental results. Model material failure includes Hashin criterion and cohesive zone model (CZM) to predict delamination. Finally, numerical models have been used to predict the crack initiation and progression in the rest of samples.

Flexural behavior of concrete slabs strengthened with textile reinforced geopolymer mortar

This paper presents results from experimental and numerical studies on the flexural behavior of reinforced concrete (RC) one-way slabs strengthened with textile reinforced geopolymer mortar (TRGM). Eight one-way RC slabs, comprising of five TRGM strengthened slabs, two TRPM (textile reinforced polymer-modified cement mortar) strengthened slabs and one un-strengthened slab, were tested under static loading. The varied parameters in the experiments included the number of textile layers, spacing of the lateral textiles, presence of anchorage, and type of binder. Data from the tests is utilized to validate finite element models developed to simulate the flexural response of TRGM strengthened slabs. Then a set of parametric studies were conducted, to evaluate the effect of reinforcement ratio, slab thickness and the number of strengthening layers. Results from the tests and numerical studies clearly show that use of TRGM for strengthening delays the development and progression of cracks in slabs and enhances the post-cracking stiffness, as well as flexural capacity. In addition, the flexural capacity increases with increased number of strengthening layers, and decreased spacing of lateral textiles. Compared with TRPM strengthened slabs, TRGM strengthened slabs possess higher flexural capacity and better crack control. Finally, a calculation model for predicting the flexural capacity of TRGM strengthened slabs is proposed and the model predictions of flexural capacity is in good agreement with the results from tests and numerical simulations.

Relation between Cutting Resistance and Crack Progress

When materials are cut with a knife, cutting resistance is a combination of (1) the reaction force (compressive) and (2) the frictional force between the knife edge and materials. When cutting resin material, the frictional force is dominant. Meanwhile, in the field of fracture mechanics, crack progress possibility is evaluated by the stress intensity factor which is calculated from energy release rate around crack tip. In this context, the relation between the calculated and measured cutting resistance are investigated, of which results are evaluated through the measurement of dynamic strain distribution of cutter surface by the Digital Image Correlation. The results are reported herein after.

Investigation of fracture toughness in mixed mode for hybrid laminated polymer composites using an A4PB type specimen

In this paper, the fracture toughness of hybrid composites for with and without fly ash composites is evaluated for asymmetric four-point bend test specimens. The preparations of specimens are by simple hand layup technique. Specimens are tested under a universal testing machine for peak load. And concluded that the specimens with fly ash composition yield better fracture toughness compared to without flyash. The scanning electron microscope study shows that the crack starting and progression is mainly dependent on s/d ratios.

Simulation of crack propagation in a thick-walled cylinder using XFEM

The integrity assessment to evaluate the safety margin of reactor pressure vessels (RPV) often considers only the crack initiation and excludes the crack propagation analysis. This contribution focuses on crack propagation analysis in RPV steels. The eXtended Finite Element (XFEM) method implemented in ABAQUS is applied to a thick-walled cylindrical specimen with a circumferential crack at the inner surface in order to simulate crack propagation in embrittled RPV subjected to Pressurized Thermal Shock (PTS). The thick-walled cylinder considered in this study was tested in the FALSIRE project, which results reported the crack opening displacement (COD) and the crack-arrest cycles occurring during the cooling down process. In order to simulate the cylinder with the XFEM, a reduced three-dimensional finite element (FE) model of a small sector (a slice of the cylinder) is used by applying cyclic symmetry boundary conditions. The COD evolution during the PTS transient is calculated and compared against the experimental COD. In the experiment, the COD shows several initiation-arrest-re-initiation cycles and final arrest. However, the results from the simulation show a smooth continuous increase of the COD indicating a progressive crack growth.

Numerical Simulation of Large Compression Deformation Disaster and Supporting Behavior of Deep Buried Soft Rock Tunnel with High In Situ Stress Based on CDEM

Large compressive deformation of tunnels is a phenomenon involving plastic deformation and failure of surrounding rocks and often refers to the weak surrounding rock self‐bearing capacity loss or partial loss. This research discusses the formation and evolution of large compressive deformation and effectiveness of the combined support of high in situ stress tunnel. From the new perspective of large deformation disaster caused by the structural failure of high in situ stress surrounding rock to clarify it, this paper illustrates the mechanism of progressive cracking and large deformation of high in situ stress soft rock tunnel from the aspects of the formation of self‐bearing system, deformation evolution of the surrounding rock, mechanical properties of the surrounding rock, and failure characteristics. Accordingly, the continuous and discontinuous numerical simulation methods are used. The following conclusions are drawn by comparing the simulation results of surrounding rock under combined support with no support. (1) The supporting structure constitutes the self‐supporting system with the surrounding rock and plays the roles of codeformation and load‐bearing. (2) The support structure has evident reinforcing effect on the rock mass in the relaxation zone, thereby leading to the phenomenon of weakened rock mass failure. Moreover, the shear area develops to the compaction zone. (3) The supporting structure improves the bearing capacity of rock mass in the relaxation zone. It also increases the surrounding rock stress and reduces the range of the compaction zone. Simulation results verify that the combined support measures have a good suppression effect on the large compressive deformation, thereby providing a reference for similar projects and research on the large compressive deformation of soft rock.

Nonlinear Numerical and Analytical Assessment of the Shear Strength of RC and SFRC Beams Externally Strengthened with CFRP Sheets

This study investigates numerically utilizing nonlinear finite element (ANSYS software) and analytically the shear response of the Reinforced Concrete (RC) beams. Different beams are considered in the current study, such as RC, steel fibre reinforced concrete (SFRC) without web reinforcement, and RC externally reinforced in the shear zone with carbon fibre reinforced polymer (CFRP) sheets. Nonlinear finite element model (FEM) is designed to simulate the performance of the designed beams. The results of FEM are compared to experimental measurements and standard design codes (ACI 440.2R‐17, FIB 14, CNR‐DT200, and ACI 318‐19). According to the experimental approach and nonlinear finite element, the enhancement in the load carrying capacity of SFRC beam due to CFRP strengthening decreases with a volume fraction of steel fibres of 2%. However, the effect of CFRP strengthening on the shear behaviour of RC beams was observed in increased load carrying and ultimate deflection capacities as a result of the CFRP strengthening. The results show that CFRP has a significant contribution to shear strength. At each load increment, the created model accurately reproduced the initial and progressive crack patterns. A comparison of nonlinear finite element and analytical models was conducted using the codes ACI 440.2R‐17, FIB 14, CNR‐DT200, and ACI 318‐19. Numerically, the FEM results showed a high agreement with ACI 440.2R‐17 standard code, with correlation approach to 99%. The comparison experimental load capacity of beams to FEM and ACI 440.2R‐17 shows that the FEM can be significantly used to estimate the shear strength of beams in the X‐Y directions with simulating different scenarios of CFRP and SFRC characteristics. The discrepancy between the nonlinear FEA and the theoretical predictions from the ACI 440.2R‐17 code is less than 1%, from the FIB14 code is less than 2%, from the CNR‐DT200 code is less than 15%, and from the ACI 318‐19 code is less than 30%. The ultimate load capacity evaluated based on ACI 440.2R‐17 code provision shows a good agreement with the experimental data as compared to the others’ code provision. The results of the finite element analysis and analytical models were in good agreement with the experimental results. The most significant advantage of finite element analysis over experimental approaches was that it can aid in the investigation of different output results that cannot be measured experimentally, such as shear stress in the XY direction throughout the beam strengthened in shear with different CFRP properties and steel fibre reinforced concrete (SFRC).

Fundamental Investigations of Bond Behaviour of High-Strength Micro Steel Fibres in Ultra-High Performance Concrete under Cyclic Tensile Loading.

The objective of the contribution is to understand the fatigue bond behaviour of brass-coated high-strength micro steel fibres embedded in ultra-high performance concrete (UHPC). The study contains experimental pullout tests with variating parameters like load amplitude, fibre orientation, and fibre-embedded length. The test results show that fibres are generally pulled out of the concrete under monotonic loading and rupture partly under cyclic tensile loading. The maximum tensile stress per fibre is approximately 1176 N/mm2, which is approximately one third of the fibre tensile strength (3576 N/mm2). The load-displacement curves under monotonic loading were transformed into a bond stress-slip relationship, which includes the effect of fibre orientation. The highest bond stress occurs for an orientation of 30° by approximately 10 N/mm2. Under cyclic loading, no rupture occurs for fibres with an orientation of 90° within 100,000 load changes. Established S/N-curves of 30°- and 45°-inclined fibres do not show fatigue resistance of more than 1,000,000 load cycles for each tested load amplitude. For the simulation of fibre pullout tests with three-dimensional FEM, a model was developed that describes the local debonding between micro steel fibre and the UHPC-matrix and captures the elastic and inelastic stress-deformation behaviour of the interface using plasticity theory and a damage formulation. The model for the bond zone includes transverse pressure-independent composite mechanisms, such as adhesion and micro-interlocking and transverse pressure-induced static and sliding friction. This allows one to represent the interaction of the coupled structures with the bond zone. The progressive cracking in the contact zone and associated effects on the fibre load-bearing capacity are the decisive factors concerning the failure of the bond zone. With the developed model, it is possible to make detailed statements regarding the stress-deformation state along the fibre length. The fatigue process of the fibre-matrix bond with respect to cyclic loading is presented and analysed in the paper.

Punching Shear Capacity of Prestressed Concrete Slabs Made of Lightweight Concrete Mixed with Short Fibers

The purpose of this study is to examine means of creating light and very strong prestressed concrete slabs made of lightweight aggregate concrete mixed with short fibers. The experiments reported in this paper demonstrated that the ratio of short fibers in the mix must be kept to 0.5 vol% or less, in order to obtain the same strength as that demonstrated by lightweight aggregate concrete designed to a standard strength of 50 N/mm2. In addition, the results of load testing various slabs confirmed that lightweight PC slabs mixed with 0.5 vol% of short PVA fibers had the same punching shear capacity as PC slabs made from normal weight concrete. The results led to the conclusion that the increase in the shear capacity of lightweight PC slabs mixed with short fibers was caused by the suppression of the progress of cracks in the RC direction and an accompanying tide arch formation in the PC direction.This paper is the English translation of the authors’ previous work [Kitano, Y., Ito, H. and Suzuki, S., (2020). “Study on lightweight and high strength prestressed concrete slab by using lightweight concrete mixed with short fibers.” Journal of Japan Society of Civil Engineers, Ser. E2 (Materials and Concrete Structures), 76(3), 239-254. (in Japanese)].

Fiber Bragg Grating Sensing Combined with Nano-Photocatalyst for Structural Safety of Bridges and Prevention of Environmental Pollution

The photocatalytic oxidation technology of nanomaterials has the potential of treating gaseous pollutants. Therefore, the fiber Bragg grating (FBG) macro strain sensor is applied to monitor the health of the bridge. Then, a mesoporous SiO2 adsorbent is taken as the carrier to prepare SiO2@TiO2 nanocomposites with adsorptionphotocatalytic ability, which is utilized in the adsorption test of gas phase toluene pollutants. The results show that FBG macro strain sensors can effectively detect the changes in bridge T beam cracks, curvature, bending stiffness, and deflection. The difference between the deflection value calculated by the conjugate beam method and the measured value of LVDT is small. In addition, the prepared SiO2@TiO2 nanomaterials present a core–shell space structure, and have excellent toluene adsorption and photocatalytic degradation efficiency. In short, the FBG macro strain sensor can be used to monitor the progression of bridge cracks, and the SiO2@TiO2 nanomaterials can realize the enrichment and continuous degradation of gas phase pollutants.

Improvement of the Mechanical Behavior of Composite Materials with Different Binders Based on Local Plant Fibers Alfa and Diss

Abstract Concerned about the environmental and economic impact, composite materials are increasingly used in the construction sector. Indeed, the use of plant fibers as reinforcement in construction materials have been the subject of several researches in recent years; the main motivation is the weight gain combined with high mechanical characteristics. The objective of this research concerns the study of the physicomechanical properties of composite materials with cement and clay matrices reinforced with Alfa and Diss fibers with dimensions ranging from 2 to 8 cm. This involves evaluating the performance of these materials according to the formulation, for a volume ratio (Alfa or Diss / Matrix fibers equal to 4), using dry fibers and pre-wetted fibers. The study of the mechanical properties showed a drop of the performance for both compression and bending strength compared to the reference material without adding fibers (cement or clay paste). It should be noted that the best mechanical performance is obtained for the case of composites materials with cementitious matrix with pre-wetted fibers. On the other hand, in the case of composites with clayey matrices, pre-wetting does not improve the mechanical characteristics. It is also noted that the best dimensions of fibers which improve the mechanical characteristics in bending are generally 6 cm for composites with a clay matrix and between 2 and 4 cm for cementitious composites. In all cases, the fibers in composite materials with cement or clay matrix create a bridging effect, making it possible to limit the progression of cracks during loading. This phenomenon gives to the various composite materials a ductile behavior.

Operando acoustic emission monitoring of degradation processes in lithium-ion batteries with a high-entropy oxide anode

In recent years, high-entropy oxides are receiving increasing attention for electrochemical energy-storage applications. Among them, the rocksalt (Co0.2Cu0.2Mg0.2Ni0.2Zn0.2)O (HEO) has been shown to be a promising high-capacity anode material. Because high-entropy oxides constitute a new class of electrode materials, systematic understanding of their behavior during ion insertion and extraction is yet to be established. Here, we probe the conversion-type HEO material in lithium half-cells by acoustic emission (AE) monitoring. Especially the clustering of AE signals allows for correlations of acoustic events with various processes. The initial cycle was found to be the most acoustically active because of solid-electrolyte interphase formation and chemo-mechanical degradation. In the subsequent cycles, AE was mainly detected during delithiation, a finding we attribute to the progressive crack formation and propagation. Overall, the data confirm that the AE technology as a non-destructive operando technique holds promise for gaining insight into the degradation processes occurring in battery cells during cycling.

Fatigue failure simulation of a double-lap composites-metal bolted joint structure

The fatigue damage behavior and the failure characteristics of the T300/QY8911 laminate and 7050-T7451 aluminum single-bolt bolted joints were investigated by test and progressive damage analysis (PDA) in this article. The manufactured composites-to-metal bolted joints (CMBJs) with different thickness metal plates and lap-patterns have been tested in static and fatigue load case and the failure characteristics are compared. A modified Lemaitre fatigue damage model and a phenomenological composite fatigue damage model were proposed and applied simultaneously to capture the damage evolution in the laminate and the metal parts. The competition of the fatigue damage of the laminate and the metal parts in affecting the joint stiffness and the coupling of the damage accumulation were studied by PDA, and the results indicates that: the failing sequence of the CMBJs constructive parts may change between the static load case and the fatigue load case; the fatigue damage of the metal parts has little effect on the joint stiffness of the CMBJs, nevertheless, there is certain coupling of the laminates fatigue damage and metal fatigue damage in the CMBJs, the harden or soften of the metal parts by fatigue hardening or crack progression would promote or slow down the damage accumulation in laminate.

Temperature Effect on Crack Evolution of Red Clay in Guilin

As temperature changes, red clay is prone to shrink and generate cracks, which weaken the structure and the stability of soil mass, leading to various engineering problems, such as damage and instability in engineering structures. To study the effect of environmental temperature on the crack evolution of red clay, Guilin Red Clay was taken as the research object, and the saturated mud samples were dried at 23, 40, and 60 °C respectively. During the drying process of the samples, the change of moisture content and the evolution process of surface cracks were monitored by high-definition automatic photographing and a weighing device, which were also improved. We used PCAS software to process the crack image, extract various geometric elements, observe, and analyze the change rule of the cracks during the drying process of red clay at different temperatures. The test results show that the cracking evolution of red clay at different temperatures is mainly divided into three stages: (i) the initiation of micro cracks; (ii) crack progress; and (iii) crack stability. With the increase of environmental temperature, stage (i) took less time. Meanwhile, the growth rate of the crack area increased. The number of final crack blocks of soil is significantly reduced. Moreover, the final crack rate is obviously increased. When the temperature is either 23 °C or 40 °C, the initial cracks almost happen at the same time in the samples with different diameters. While the temperature is higher than 60 °C, the cracking time will delay with the increase of the diameter. In addition, the decrease in water content leads to a decrease in the curvature radius of soil particles. Under the joint action of the surface tension and the matrix suction, the distance between red clay particles becomes shorter, so the time for red clay to start to generate cracks will be shorter, and the final crack rate will increase with the increase in temperature.

Macro-meso failure behavior of pre-flawed hollow-cylinder granite under multi-level cyclic loads: Insights from acoustic emission and post-test CT scanning

The structural deterioration and associated macro-meso fracture behaviors of granite containing crack-like and hole-like flaws subjected to multi-level cyclic loads are studied in this paper. The tested samples were prepared with a hollow hole of 15 mm and different flaw approach angles of 10°, 30°, 50° and 70°, respectively. The real-time AE monitoring combined with post-test CT scanning was employed to reveal the effects of flaw angle on the strength, deformation, AE activities and crack network pattern. Results show that the communication of the crack network and hole controls the rock volumetric deformation and the final failure modes. The output AE activities are influenced by the flaw arrangement. The progressive crack unstable propagation is much more severe for rock with low flaw angle and the recorded AE count/energy curves present multi-stage skips. The AE b value shows a first increase and then a decrease pattern. A damage evolution model was proposed by AE b value, the first fast and then steady increase and the final abrupt increase of accumulative damage can be well described. The complexity of crack network is larger for rock has high flaw angle, and the communication of crack and hole wall is severe accordingly. It is suggested that the failure of the pre-flawed hollow-cylinder granite is the interaction of crack coalescence and hole spalling.