Interfacial Zone Research Articles

Investigation of the 4D Multi-Material 316L/FeNi36 Obtained by Selective Laser Melting

Multi-material can have functional properties, which are not typical for the materials of which they are composed (for instance, shape-changing effect). This can be used in robotics, micromachines, aerospace, and other fields. In this work, the 316L/FeNi36 multi-material produced by selective laser melting was investigated. The results show that the interfacial zone of the multi-material exhibits mixing regions of the two alloys but no defects. The microstructure is constituted by large grains with epitaxial growth, which propagate in a directional manner from the 316L alloy through the interfacial zone to the FeNi36 region. The multi-material sample displays three different zones of chemical composition: the FeNi36 composition zone; the interfacial zone; and the 316L zone. The size of the interfacial zone is approximately 50 µm. The multi-material sample exhibits the presence of three distinct phases: γ-Fe; γ-Fe64Ni36; and α-Fe. The hardness of the FeNi36 zone is approximately 163 HV, followed by an interfacial zone with a hardness of approximately 200 HV and then, the 316L zone with a hardness of approximately 214 HV. Functional tests demonstrate that the shape-changing effect is directly correlated with the variation in the FeNi36 thermal expansion coefficient with temperature. For achieving the most pronounced shape-changing effect, the temperature range of 25–215 °C is more suitable.

Study on the Chloride–Sulfate Resistance of a Metakaolin-Based Geopolymer Mortar

The chloride–sulfate corrosion environment of concrete is a significant engineering problem. This paper investigates the effect of the complete/semi–immersion mode on the durability of concrete in a chloride–sulfate environment by using different granulated blast furnace slag (GBFS) dosage rates (10–50%) of a metakaolin (MK)-based geopolymer mortar. The chloride–sulfate corrosion environment is discussed by analyzing the apparent morphology, mass change, and mechanical property change in specimens at the age of 120 d of erosion combined with XRD and SEM. The high Ca content in GBFS has an important effect on the strength and erosion resistance of the metakaolin geopolymer (MGP) group mortar; an increase in the GBFS dosage makes the MGP group mortar denser, and the initial strength of the MGP group mortar is positively correlated with the dosage of GBFS. After 120 d of erosion, the GBFS dosage is negatively correlated with erosion resistance, with the high GBFS dosage groups showing more severe damage. Semi-immersion resulted in more severe deterioration at the immersion–evaporation interface zone due to the difference in the ionic concentration and the ‘wick effect’ at the immersion–evaporation interface zone. Compared with the commonly used OPC mortar, the M40 and M50 groups have improved strength and corrosion resistance and are suitable for engineering environments in highly erosive areas.

Critical Review of Physical-Mechanical Principles in Geostructure-Soil Interface Mechanics

AbstractDue to the relatively different mechanical and physical properties of soils and structures, the interface plays a critical role in the transfer of stress and strain between them. The stability and safety of geotechnical structures are thus greatly influenced by the behavior at the soil–structure interface. It is therefore important to focus on the unique characteristics that set the interface apart from other geomaterials while examining the interface behaviour. Understanding the physical mechanism and modelling principles of these interfaces becomes a crucial step for the secure design and investigation of soil-structure interaction (SSI) issues. Moreover, to deal with this soil-environment interaction problem, the classical soil mechanics formulation must be progressively generalised in order to incorporate the effects of new phenomena and new variables on SSI behaviour. Considering the variety of energy geostructures that are emerging nowadays, it is crucial to comprehend the thermo-hydro-mechanical (THM) behaviour of the interface. The objective of this study is to fill this information gap as concisely as possible. A critical review is provided along with the state-of-the-art information on the thermo-hydro-mechanical behaviour of the soil-structure interface, including testing tools and measurement methods, basic principles and deformation mechanisms, constitutive models, as well as their applications in numerical simulations. This study explains how loading influences the mechanisms at the interface and critically examines the effects of boundary conditions, soil properties, environmental factors, and structure type on the THM behaviour of interface zones between soils and structural elements. The validity and reliability of the interface shear stress-displacement models are also covered in this paper. Lastly, the trends and recent advancements are also recommended for the interface research.

The effects of hydrogen on the bonding properties of SiC/Cu interface via first-principles calculations

Ceramic/metal interfaces own great importance of technology, but the weak interface bond limits their applications. In this work, the effects of doping H element on the stability and bonding properties of SiC/Cu interface are studied by first principles calculations. In order to study the stability of interface, the potential surfaces were firstly studied for the C and Si terminated SiC/Cu interfaces. The C terminated interface is more stable than the Si terminated interface, which contributes the largest work of adhesion of 3.998 J/m2. The effects of hydrogen on the interface bonding properties were further studied. The occupation properties of hydrogen atoms were then studied, the hydrogen tends to occupy the octahedral position with negative formation energy. To reveal the bonding strength of SiC/Cu interface, the tensile simulations were carried out. The hydrogen owns obvious effects on the tensile strength depends on its occupation site. The movement and diffusion properties of hydrogen atoms in the interface zone were studied combining molecular dynamics and climbing image nudged elastic band method. Finally, the bonding mechanisms were analyzed by combining charge density, state density, differential charge and bader charge. Based on the above calculation results, it is found that for SiC(001)/Cu(111) interface, the H element generally has a negative impact on the bonding properties of SiC/Cu interface.

Self-assembled nanoflower-mediated interfacial polymerization through tunable intra- and inter-layer channels to boost total heat exchange performance

Total heat exchange membranes (THEMs) are vital for minimizing energy consumption and enhancing indoor air quality in energy recovery ventilation (ERV) systems. Manipulating the surface morphology of polyamide (PA) membranes via nanofiller-mediated interfacial polymerization is key to advancing total heat recovery performance. This study presented the fabrication of PA thin-film nanocomposite (TFN) membranes by integrating self-assembled poly(amic acid-imide) nanoflowers (P(AA-I)-NFs) with intertwined nanosheets into the organic phase. This facile approach effectively eliminated nonselective interphase voids and defects, owing to the superior polymer affinity of the organic nanoflowers. The finely tuned intra- and inter-layer channels within P(AA-I)-NFs significantly impacted monomer mass transfer, facilitated the shuttle effect, expanded the interfacial polymerization zone, and led to the formation of a rougher, thicker PA layer with enhanced surface area. The optimized P(AA-I)-NFs/PA TFN membranes exhibited outstanding performance, including CO₂ permeability of 0.51 GPU, water vapor permeability of 656.59 GPU, and an enthalpy exchange efficiency of 71.47 %, surpassing the trade-off limitations typically observed in commercial and other advanced THEMs. These findings underscored the potential of P(AA-I)-NFs-mediated TFN membranes as highly competitive candidates for next-generation ERV systems.

Mechanical and microstructural profiling of additively manufactured cobalt–nickel functional gradient structure

In this study, a functional gradient material (FGM) structure composed of a nickel alloy (IN718), and a cobalt alloy (CoCrMo) was additively manufactured using a co-axial powder-fed laser-directed energy deposition (L-DED) system. The high manufacturing flexibility of L-DED enabled the seamless deposition of IN718-CoCrMo FGM structure through interfacial bonding driven by thermal gradient and cool-down mechanisms. Microscopic analysis confirmed the absence of cracks or delamination in the CoCrMo-IN718 interfacial bonding region. The SEM-EBSD microstructural analysis and micro-hardness testing were performed on the as-printed CoCrMo-IN718 FGM primarily to correlate the hardness properties-microstructural grain phase morphology between the parent alloys and their interfacial bonding region. It was observed that the average hardness of the CoCrMo-IN718 interface zone (322.83 HV1) fell between IN718 (268.67 HV1) and CoCrMo (359.75 HV1) regions. The EBSD analysis reports indicated that along the build direction of CoCrMo-IN718 FGM, the preferential grain orientation aligned in [100] with grain structure transitioning from equiaxed → columnar → elongated columnar dendrites → equiaxed grain, predominantly comprised of face-centered cubic (FCC)-gamma (γ) phase crystal structures. Relatively, coarser grain structures were observed in the interface bonding region, attributed to the analogous crystallography space groups, and prolonged localized thermal gradients.

Improvement of fatigue life by aluminizing of additive manufactured Fe- and Ni-base alloy

Laser powder bed fusion (PBF-LB/M) is used in various industries to manufacture complex parts with high precision. High surface roughness and porosity have a negative impact on fatigue resistance. This work presents aluminum pack cementation as a method to reduce surface roughness and improve fatigue resistance of AM parts. An Fe-base alloy (Alloy 800H) and a Ni-base alloy (Alloy 699XA) are selected. Some of the specimens made from PBF-LB/M were treated by pack cementation with aluminum, while others were subjected to the vibratory finishing process. The surface roughness, microhardness distribution and the microstructure of the interface zone were measured and analyzed for the as-built, vibratory finished and aluminized specimens. Rotating bending fatigue test was performed at room temperature. Conventionally fabricated specimens of both investigated alloys were tested under the same conditions to evaluate the effects of pack cementation. The aluminized samples (PBF-LB/M) show a significant reduction in surface roughness with a decrease of 45 % for Alloy 800H and 65 % for Alloy 699XA. This leads to an improvement in fatigue life for both Alloy 800H and Alloy 699XA. In contrast, the conventionally fabricated specimens exhibited increased surface roughness after pack cementation compared to their initial condition and showed a significant reduction in fatigue resistance.

PSO-BP model for assessing frost resistance in containment concrete with varying pipe diameters

The safety of containment concrete is of utmost importance for nuclear power plants. The presence of pipe openings in the containment concrete structure introduces weakened areas, which adversely impact the mechanical properties and durability of the concrete. However, little research has been done on the durability of containment concrete with embedded steel pipe (CCESP), and no studies are found on its frost resistance under single-side freezing and thawing conditions. In this paper, using single-side salt freeze-thaw experiment to simulate the practical situation of coastal containment concrete, the effect of different steel pipe diameters (d) on the frost resistance of containment concrete was investigated. Based on the experimental results and using backpropagation neural networks optimized by a particle swarm algorithm (PSO-BP), a model was established to predict the frost resistance of CCESP for varying values of d. The research results showed that wall effects and stress concentrations created an interface zone between the steel pipes and the concrete, leading to a decline of compressive strength. Freeze-thaw cycles had only a slight impact on the relative dynamic elastic modulus (E) of CCESP, while the exfoliation mass per unit area (M) of the concrete specimens increased linearly with d. It indicates that pipe opening adversely impacts the frost resistance of the concrete, and that M can be used to evaluate the frost resistance of CCESP. This study addresses the research gap in the frost resistance of containment concrete with steel pipe openings, and the proposed PSO-BP model can accurately predict the frost resistance of containment concrete with varying pipe diameters under different freeze-thaw cycles.

Bending of a piecewise homogeneous plate with a circular interfacial materials separation zone and radial crack considering the strip contact of its edges

Bending of a piecewise homogeneous plate with a circular interfacial materials separation zone and radial crack considering the strip contact of its edges

Influence of Ni‐Coating Thickness on Interface Microstructure and Mechanical Properties of Mg/Ti Bimetal via Compound Casting

In this article, the influence of Nickel (Ni)coating thickness on the interfacial microstructure and mechanical properties of AZ91D/Ti–6Al–4 V bimetal fabricated by compound casting is investigated. In the results, it is shown that the Ni coating and its thickness have a significant effect on the interfacial phase compositions and mechanical properties of AZ91D/Ti–6Al–4 V bimetal. At a Ni‐coating thickness of 6.5–27.3 μm, it transforms into α‐Mg + Mg2Ni eutectic structures + blocky τ‐Ni2Mg3Al ternary compounds at the interface zone. When the Ni‐coating thickness increases to 36.1 μm, part of the Ni coating remains, and the interface layer forms, comprising the Ni solid solution layer, Mg2Ni layer, τ‐Ni2Mg3Al ternary compounds, and α‐Mg + τ‐Ni2Mg3Al particles from Ti–6Al–4 V to AZ91D side in sequence. The microhardness of the interface zone is lower than that of the Ti–6Al–4 V but higher than AZ91D. The bimetal shear strength reaches a maximum value of 87.6 MPa at a Ni‐coating thickness of 19.7 μm enhanced by 78.5% in comparison with that of the bimetal without Ni coating. The results are helpful to further enrich the interface control method of compound casting of Ti/Mg bimetal and determine the ideal interlayer thickness for maximizing interface strength.

Effects of low temperatures and steel fibres on the flexural properties of carbonised recycled aggregate concrete

To investigate the effects of low temperatures and carbon dioxide reinforcement on the flexural properties of steel fibre recycled concrete, this study conducted three-point bending tests on 16 sets of carbonated recycled aggregate concrete (CRAC) beams and 16 sets of recycled aggregate concrete (RAC) beams. The flexural properties of them at different low temperatures (20 ℃, 0 ℃, −30 ℃, −60 ℃) and steel fibre volume dosage (0 %, 0.5 %, 1.0 %, 1.5 %) were compared. The flexure toughness index, flexural tensile strength, and equivalent flexural strength were calculated from the macroscopic test results to assess the flexural resistance of CRAC comprehensively. Combined with scanning electron microscopy-energy spectroscopy (SEM-EDS) analysis, the microstructure and elemental content of CRAC were analysed to reveal the mechanism of carbonation and low temperatures on the macroscopic mechanical properties of CRAC. The results showed that the flexural properties of recycled aggregate concrete reinforced with CO2 were significantly improved compared to RAC. The maximum increase in flexural tensile strength and equivalent flexural strength of CRAC after low temperatures was about 61.94 % and 61.38 %, respectively. CO2 can react with the cement hydration products of the recycled aggregates to produce CaCO3 and silica gel, filling in the transition zone of the CRA-matrix interface, which can improve the microstructural densification of the CRAC at low temperatures. With further decrease in temperature, the effect of low temperatures on the flexural properties of CRAC was more significant due to the impact of ice crystal growth, with a maximum enhance in flexural tensile strength and equivalent flexural strength of 131.35 % and 165.93 %, respectively, compared to that at 20 ℃. The strength and toughness of CRAC with 1.5 % steel fibre are improved best at low temperatures.

An Insight into the Mechanical Properties of Unidirectional C/C Composites Considering the Effect of Pore Microstructures via Numerical Calculation.

Pores are common defects generated during fabrication, which restrict the application of carbon/carbon (C/C) composites. To quantitatively understand the effects of pores on mechanical strength, this paper proposes a representative volume element model of unidirectional (UD) C/C composites based on the finite element method. The Hashin criterion and exponential degraded rule are used as the failure initiation and evolution of pyrolytic carbon matrices, respectively. Interfacial zones are characterized using the cohesive constitutive. At the same time, periodic boundary conditions are employed to study transverse tensile, compressive, and shear deformations of UD C/C composites. Predicted results are compared with the experimental results, which shows that the proposed model can effectively simulate the transverse mechanical behaviors of UD C/C composites. Based on this model, the effects of microstructural parameters including porosity, pore locations, the distance between two pores, pore clustering, and pore shapes on the mechanical strength are investigated. The results show that porosity markedly reduces the strength as porosity increases. When the porosity increases from 4.59% to 12.5%, the transverse tensile, compressive, and shear strengths decrease by 35.91%, 37.52%, and 30.76%, respectively. Pore locations, the distance between two pores, and pore clustering have little effect on the shear strength of UD C/C composites. For pore shapes, irregular pores more easily lead to stress concentration and matrix failure, which greatly depresses the bearing capacity of UD C/C composites.

Fracture properties of bamboo fibrous composites: A systematic review

As a fast-growing grass, bamboo has received a great deal of attention due to the excellent mechanical performance. The unique properties of bamboo come from its natural composite structure - a kind of natural fiber reinforced composites, which is composed of bamboo fibers (reinforcement) and parenchyma tissue (matrix). Based on raw bamboo, man-made bamboo fibrous composites such as engineered bamboo and bamboo fiber reinforced polymeric composites have emerged. These materials eliminate some inherent shortcomings of bamboo, which can provide more stable material performance and achieve dimension alteration according to requirements. All of these bamboo fibrous composites have orthotropic structure, the mechanical properties of which in the longitudinal direction far exceed that in the transverse direction, and the tensile strength and compressive strength can reach 111–114.8 and 104.7–115.7 MPa respectively. Besides, the interfacial zone between fiber and matrix is weak, in which some defects are usually existed, such as micro-cracks and adhesive voids. As a result, cracks in the composites are inevitable, which are easy to extend in the longitudinal direction and result to fracture failure. Consequently, fracture studies become necessary for evaluating the crack-resistance ability of bamboo fibrous composites. This paper systematically introduces the previous research works on the fracture properties of bamboo fibrous composites. Firstly, this paper summarized the test methods for different fracture modes including Double cantilever beam (DCB), Single-edged notched beam (SENB), Compact tension (CT), etc., meanwhile the corresponding calculation theories such as Compliance calibration (CC), Modifed compliance calibration (MCC) and Modified beam theory (MBT) are also elucidated. Subsequently, the fracture behaviors and mechanisms of various bamboo fibrous composites are analyzed, in which the fracture parameters and crack-resistance capabilities are compared. In addition, considering the limitations of current research, the future research in need on the fracture properties of bamboo fibrous composites are discussed, the conclusion can be used in providing important reference for the safety evaluation of bamboo fibrous composites.

Exploring mechanical behavior at interfaces of laser powder bed fusion (LPBF) deposits on wrought Inconel 718: an indentation-based approach

PurposeThis study used an indentation-based mechanical testing framework for the mechanical characterization of laser powder bed fusion (LPBF) processed Inconel 718 on a wrought Inconel 718 substrate. The purpose of the paper is to investigate the effectiveness of the indentation-based approach for localized mechanical evaluation.Design/methodology/approachThe LPBF-processed wrought substrate was sectioned into three sections for microstructural and mechanical characterization. A 3D heat source model was used for the thermal analysis of the interface region. The developed interface region is probed using the Knoop hardness indenter in different orientations to determine the textural anisotropy and mechanical behavior of the region.FindingsLPBF process develops a melted interface zone (MIZ) at the deposition-substrate interface. The MIZ exhibited a coarse grain structure region along with a larger primary dendritic arm spacing (PDAS), signifying a slower cooling rate. FE modeling of the LPBF process reveals heat accumulation in the substrate along with intrinsic heat treatment (IHT) induced due to layer-wise processing. The obtained yield locus shows strong anisotropy in the deposition region, whereas reduced anisotropy with a nearly uniform ellipse locus for the MIZ regions. This reduced anisotropy is attributable to IHT and heat accumulation in the substrate.Originality/valueAn alternative localized mechanical characterization tool has been investigated in this work. The approach proved sensitive to thermal variations during LPBF processing in an isolated region which extends its suitability to variable geometry parts. Moreover, the approach could serve as a screening tool for parts made from dissimilar metals.

A multiscale steel–concrete interface model for structural applications

In this paper, a new multiscale macro-element formulation for the steel–concrete interface modeling is proposed. This element allows for the representation of the behavior of steel and the interface zone surrounding it. It can also model the interfacial bond stresses in between. Compared to conventional interface models of the literature, which employ separate mesh elements for the steel and the interface, utilizing a macro-element to model both components simplifies the creation of a reinforced concrete structure mesh. Moreover, the macro-element equilibrium is solved using a sub-structuring method that aims to reduce the computational cost. At the global level, it is considered as a four-node element linked to two-dimensional and three-dimensional concrete elements. At the local level, an assembly of multiple three-node bar elements with bond stresses is performed. An inner mesh discretization is therefore possible at the local level independently of the global level. The coupling between the two modeling scales is done using a static condensation technique. The formulation of the macro-element is presented in this paper. A selection of numerical examples is provided. The presented applications demonstrate the robustness of the proposed interface model and its capacity to reproduce the experimental behavior of reinforced concrete structural elements.

Microstructure and tensile properties of transient liquid phase (TLP) sintering repaired Ti–6Al–4V alloys with large area hole defect

Repairing defects in titanium alloy components is economically justified due to their high cost. In this work, Ti–6Al–4V samples with large area hole defects are repaired by transient liquid-phase sintering. The microstructure and tensile properties after repair have been investigated. The factors of different base powder morphology and the ratio of braze metal are also studied. The results show that by using spherical Ti64 alloy powder with 40 wt% TiZrCuNi braze alloy powder, an overall repair effect with high-density repair zone and good interface combination can be obtained at 960 °C for 3 h. The tensile strength of the as-repaired exceeds that of the matrix, but the elongation is lower than that of the matrix. Finally, the repair experiment conducted at various angles demonstrates this technique's strong practical feasibility.

Development of novel osteochondral scaffolds and related in vitro environment with the aid of chemical engineering principles

In tissue engineering, collaboration among experts from different fields is needed to design appropriate cell scaffolds and the required three-dimensional environment. Osteochondral tissue engineering is particularly challenging due to the need to provide scaffolds that imitate structural and compositional differences between two neighboring tissues, articular cartilage and bone, and the required complex biophysical environments for cultivating such scaffolds. This work focuses on two key objectives: first, to develop bilayered osteochondral scaffolds based on gellan gum and bioactive glass and, second, to create a biomimetic environment for scaffold characterization by designing and utilizing novel dual-medium cultivation bioreactor chambers. Basic chemical engineering principles were utilized to help achieve both aims. First, a simple heat transport model based on one-dimensional conduction was applied as a guideline for bilayer scaffold preparation, leading to the formation of a gelatinous upper part and a macroporous lower part with a thin, well-integrated interfacial zone. Second, a novel cultivation chamber was developed to be used in a dynamic compression bioreactor to provide possibilities for flow of two different media, such as chondrogenic and osteogenic. These chambers were utilized for characterization of the novel scaffolds with regard to bioactivity and stability under dynamic compression and fluid perfusion over 14 d, while flow distribution under different conditions was analyzed by a tracer method and residence time distribution analysis.

Identification of interfacial influence zone (IIZ) in clay rock-cement mortar binary based on the macro-pore distribution in space: An NMR and CT investigation

The interfacial influence zone (IIZ) is a weak link between cast-in-situ cement materials and bulk geological materials. Identifying IIZ is essential for studying binary structure’s mechanical properties. This paper aims to locate the IIZ of a clay rock-cement mortar (C-C) binary by macro-pore distribution in space using CT and NMR tests. First, the porous properties of clay rock and cement mortar were analyzed by the T2 spectrum of the NMR test. Mortar’s macro-pore volume is larger than clay rock’s. Second, the 3D pore-matrix models of these two materials were reconstructed., with larger porosity in mortar than clay rock, consistent with NMR tests. Therefore, the method of pore location using 3D reconstructed models based on CT images may be reliable. Finally, a pore-matrix model of the C-C binary was reconstructed, and the IIZ was identified by pore distribution. The IIZ shape is an approximately ellipsoidal area with thin ends and thick middle, with a max thickness of 8 mm.

Driving forces of solid-state Cu-to-Cu direct bonding suppressing the work-hardening loss by refill friction stir spot welding

In this study, the solid-state bonding of the Cu-to-Cu parallel connection with no fusion zone and keyhole formation was achieved using the refill friction stir spot welding (RFSSW) process. During the refilling process, significant plastic flow and thermo-compressive behavior promoted geometric and continuous dynamic recrystallization behaviors and highly oriented (111) microstructures, serving as key mechanisms to prevent work-hardening loss and reinforce the joint. Furthermore, the refinement of the grain size without work-hardening loss, increased by 50.8 % which was from 61 Hv in the base material to 92 Hv in the thermo-mechanically affected zone (TMAZ). Even, the hardness of the TMAZ/stir zone interface noticeably increased up to 138 Hv as the reduction in the stacking fault energy (SFE) due to the infiltration of Al element at the trace from the tool. The contribution of microstructural features to the mechanical property was quantitatively investigated by a modified Hall-Petch relationship in terms of the grain size, sub-grain size, and dislocation density. This study systematically investigated the driving forces for the implementation of Cu-to-Cu direct bonding, where work-hardening loss can be suppressed, through the RFSSW process from the perspective of dynamic recrystallization behavior and SFE due to partial alloying of Al elements.

The structural assessment for concrete structure on the onset of cracking with respect to steel corrosion

The present study concerns structural behaviour of a marine bridge in terms of cracking exposed to a seawater environment under the risk of chloride-induced corrosion with the axial loading. In the modelling process, the corrosion propagation was expressed into the rust formation on the steel surface, while the axial load was given 5–30 % to the compressive strength of concrete. The interfacial gap between steel and concrete was taken 10 µm, imposing the buffering capacity against a build-up of the rust at the steel-concrete interface. As a result, it was found that the tensile damage produced the cracking on the surface of concrete with a minimal corrosion of steel, which was further developed into the inner concrete depth with increasing corrosion formation. Also, an increase in the axial load resulted in an increase in the surface cracking at a given rust formation. At the steel-concrete interface, the cracking was much affected by the compressive deformation arising from a build-up of rust, as being limited in the vicinity in the interfacial zone, presumably due to the limited rust formation. A combination of steel corrosion and axial loading imposes the accelerated cracking of concrete structure then to rapidly deteriorate its serviceability.