This article presents the results of tests conducted to identify the failure process and evaluate the deformation of axially compressed concrete specimens modified with polypropylene fibers (PP). The test specimens were previously stored at ambient temperature and subjected to fire temperatures of 300 °C, 450 °C, and 600 °C. Acoustic emission (AE) signals were recorded during loading, along with force and strain measurements. The recorded AE signals were analyzed using the k-means clustering method. The compilation of the test results made it possible to determine the classes of signals characteristic of different stages of the material failure process and to indicate the differences in the failure mechanisms of specimens stored under ambient conditions and subjected to fire temperatures. Digital image correlation (DIC) measurements were conducted during the strength tests. A numerical model of the material (FEM) was also prepared, and a comparison of the obtained results was carried out. As is well known, it is possible to add polypropylene fibers to the concrete mix to ensure ductility, improve mechanical properties, and extend durability. This creates polypropylene-fiber-reinforced concrete (PPFRC). Thus, from a simple material, concrete becomes a complex solution that can be adapted to specific applications ,2.The requirements that concrete must meet relate not only to mechanical properties such as high compressive, tensile, and flexural strength but also to architectural qualities and safety. As more and more emphasis is now being placed on sustainability, reducing carbon dioxide production and extending the life of concrete structures is becoming one of the priority measures. Accordingly, efforts are being made to reduce the number and size of scratches and pores; reduce water permeability and chemical penetration; and increase strength, protect against corrosion, and reduce the negative effects of fire, freezing, thawing, impact, and abrasion. PPFRC is a material that can meet these requirements ,4,5.Polypropylene fibers (PPFs) are define by ASTM  as straiThe positive effect of the addition of fibers to concrete is also noticeable in tests of resistance to abrasion, impact, spalling, and freeze–thaw cycles. In addition, instead of the brittle type of failure, fiber concrete after scratching is able to carry loads with increasing crack width. On the other hand, lower porosity, permeability, and water absorption allow the extension of the life of the fiber concrete element ,4,5,7.Thanks to their scratch resistance, concretes with polypropylene fibers are used for the construction of, among other things ,Sidewalks and pedestrian paths;Thin-walled façade elements;“Small architecture” elements;Repair layers of reinforced concrete elements (by the shotcrete method).Monolithic water tanks;Settling tanks in sewage treatment plants;Sewage tunnels.The chemical (corrosion) resistance of polypropylene fibers determines their use as an additive  also in the following concrete structures ,7:MonoliPolypropylene fibers are also a component of precast concrete tunnel lining elements as they counteract the explosive behavior of concrete and spalling at fire temperatures ,5,7,8,9.In construction practice, an important issue is the behavior of concrete during a fire. The dimensioning of load-bearing elements made of concrete and reinforced concrete with regard to the risk of fire is carried out, as a rule, on the basis of values tabulated in standards, taking into account the effects of fire on materials and elements. Concrete is considered a non-combustible and fire-resistant material. However, it is known that even under typical conditions of ordinary fires, serious damage can occur in it, the effects of which depend on the duration of the fire and the type of construction ,9,10,11.The decrease in the strength of concrete at temperatures around 200 °C is small; between 200 and 500 °C, the decrease in strength is much faster, and at 500 °C the basic compressive and tensile strength can decrease by several tens of percent. Above 500 °C, the strength of the concrete drops almost to zero ,12,13,143] in the temperature range of 100, 300, 500, and 700 °C. The samples were tested for compressive strength. It was found that the residual strength decreased almost linearly up to 700 °C. The influence of polypropylene fibers and silica fume on the mechanical properties of lightweight concrete exposed to high temperatures was investigated experimentally and statistically by Tanyildizi [v/v) PP fibers were added. At a temperature of 800 °C, the relative compressive strength was the same for concretes with and without PP fibers. Behnood and Ghandehari [The mechanical properties of fiber-reinforced concrete exposed to high temperatures have been the subject of many analyses. Sideris et al.  tested cnyildizi . Mixturenyildizi  reportedandehari  and Hoffandehari  reportedandehari  found thandehari  investigThe research results show that the mechanism of polypropylene fibers, due to the fact that they melt at a temperature of 170 °C and create a porous structure, reduces the build-up of pore pressure inside the heated concrete structure ,23,24,25NDT methods, especially acoustic emission (AE), are very widely used in condition monitoring of many engineering structures. Acoustic emission as a phenomenon can be defined as transient elastic waves resulting from local internal microdisplacements in the materials of the structures under test. The AE method has become a common NDT method used mainly for testing stationary equipment—tanks, pressure vessels, reactors, pipelines, bridges, etc. In these applications, the AE method is fully accepted and standardized. AE provides a wealth of information about the response of materials to applied stresses. It is useful for detecting and identifying increasing material defects. Thanks to its sensitivity, it can detect such processes as the formation and growth of microcracks, dislocation group displacement, cracking, sliding, or debonding of deposits ,30.The advantage of the AE method is the ability to examine the entire structure/element, locate any damage, and assess its threat to the structural integrity. AE application brings significant economic benefits ,32,33,34In this article, through the use of multiparameter analysis of AE signals, the identification of destructive processes in PP-fiber-modified concrete during compression testing was carried out. Differences were indicated regarding the loading of specimens stored at room temperature and those subjected to fire temperatures. It was established that high temperatures led to a decrease in the mechanical parameters of the material, as well as a change in the mode of operation under load. It was confirmed that the acoustic emission method, due to the differences at low load values, can be a useful tool for evaluating the technical condition of PP-fiber-modified concrete after exposure to fire temperatures. So far, similar research directions have not been encountered.In the present study, in addition to AE methods, numerical calculations using the finite element method and image analysis of the deforming specimen using a video extensometer (DIC methods) were used to evaluate the condition of PP-fiber-modified concrete elements after exposure to high temperatures. The use of the above-mentioned diversified test methods will allow a comprehensive approach to the evaluation of the behavior of the analyzed material ,38,39,403. The length of the fibers was 12 mm, and the diameter was 29 μm. Information on the exact composition of the material was not obtained, as the formula is protected by patent law.Concrete cubes of 150 × 150 × 150 mm were tested. The pieces had a concrete structure with the addition of dispersed PP fibers. The test material was obtained from an entity offering to sell modified concrete for industrial use. It was concrete on Portland cement with 10% fiber content. The overall density was 2417 kg/mFour series of three samples each were tested. Samples from the first group, A, were stored at ambient room temperature (±20 °C). Samples from the second test series, B, were subjected to firing in a laboratory furnace. The processing temperature was 300 °C. The annealing time from the time the set temperature was reached was 3 h. Samples from the third test series, C, were subjected to firing in a laboratory oven at 450 °C. The annealing time from the time the set temperature was reached was 3 h. Samples from the fourth test series, D, were subjected to firing in a laboratory furnace at 600 °C. The annealing time from the time the set temperature was reached was 3 h.The firing time of the specimens in the furnace was set to bring the temperature to a uniform value throughout the volume of the conditioned parts. Samples cooled under air conditions at ambient room temperature were tested.The cubic specimens were subjected to axial compression using a Zwick Roell testing machine. A schematic diagram and view of the test stand are shown in Acoustic emission signal acquisition was carried out during the study. For this purpose, an AEWin acoustic emission processor  and two Vallen sensors of the VS75-SIC-40dB type were used.During the tests, image recording was conducted on the front of the specimen for later analysis using DIC–GOM Suite software v2022, rev. 157716.The acoustic emission (AE) method belongs to the group of passive methods, that is, the AE apparatus does not emit signals and does not affect the physical state of the object/element under test but only records physical effects spontaneously arising in the monitored object. The sources of the acoustic emission signal are the formation and propagation of microcracks, corrosion processes, the cracking of strings in prestressed structures, the escape of gas through leaks in the pressure structure, or damage to the insulation of high-voltage power equipment, that is, processes in which elastic waves are formed and propagate in the object. The AE apparatus records the signal generated in the tested object during its normal operation or during tests. The elastic waves generated in the AE source propagate from the source in all directions in the volume of the monitored object. The elastic waves reach the AE sensor and are then transmitted to the AE analyzer in the form of electrical voltage changes. The mathematical model of the propagation of these waves and the accompanying changes in their form is quite complex and uses the properties of the Green’s function ,41,42.The measurement apparatus consists of AE sensors that convert AE signals into an alternating electrical voltage, AE analyzers that amplify this voltage and eliminate signals that do not originate from the monitored source (acoustic background), and an AE signal recorder ,42,43.For the classification of AE signals, NOESIS v12 software is very often used, which is mainly based on the pattern recognition method, in two versions: an arbitrary class division (unsupervised), USPR, and a self-learning one, in which the class division is performed using pattern signals (supervised), SPR ,41,42,43In the first case, arbitrary pattern analysis is mainly used when creating a database of pattern signals if the number of classes is unknown. The second method is used, in cases where pattern signals characterizing a given destructive process are available. The benchmark signals are signals previously collected in a database, generated during independent experiments ,42.For statistical methods used for object recognition, an important consideration is the optimal choice of acoustic emission parameters to be recorded. Many acoustic emission parameters have a strong correlation with each other, so that they can carry the same information about the AE source. The degree of correlation between AE parameters is determined by so-called dendrograms ,33.An important issue that may affect the accuracy of the calculations, which should also be taken into account, is the number of iterations needed to obtain satisfactory results. It has been accepted that a sufficient number of iterations is 10,000. Decreasing this number results in a significant decrease in the fit of the signals in each class, while increasing it slows down the analysis process, and the obtained results improve the fit only slightly ,32,33,34The NOESIS program uses different clustering methods, and the manual does not provide guidance on which one to choose. In the discussed analyses, the Fuzzy K-means algorithm was used ,30.The k-means method is a method belonging to the group of cluster analysis algorithms, i.e., an analysis involving the search for and separation of groups of similar objects (clusters). It represents a group of non-hierarchical algorithms. The main difference between non-hierarchical and hierarchical algorithms is the need to specify the number of clusters in advance ,32,33,34Using the k-means method, k different, possibly distinct clusters are created. The algorithm involves moving objects from cluster to cluster until intra-cluster and inter-cluster variability is optimized. The similarity within a cluster should be as high as possible, while the separate clusters should differ from each other as much as possible ,41.Determining the number of clusters.The methodology of the algorithm can be described as follows ,41,42,43One method of determining the number of clusters is to contractually select it and possibly change this number later to obtain better results. The choice of the number of clusters may also be based on the results of other analyses.2.Determination of initial cluster means.The cluster means, the so-called centroids, can be selected in several ways: random selection of k observations, selection of the first k observations, or selection in such a way as to maximize the cluster distances. One of the most common methods is to run the algorithm several times and select the best model when the initial cluster means were selected randomly.3.Calculation of the distance of objects from the cluster centers.The choice of metric is a very important step in the algorithm. It influences which observations will be considered similar and which will be considered too different from each other. The most commonly used distance is the Euclidean distance . The square of this distance or the Chebyshev distance is also used.4.Assignment of objects to clusters.For a given observation, compare the distances to all clusters and assign it to the cluster to which it has the closest center.5.Determination of new cluster centers.Most often, a new cluster center is a point whose coordinates are the arithmetic mean of the coordinates of the points belonging to a given cluster.6.Repeat steps 3, 4, and 5 until a stop condition is met.The most commonly used stop condition is the number of iterations set at the beginning or the absence of object transfers between clusters.The results of the experimental tests served as the basis for the numerical calculations. Numerical models were developed for specimens identical to those used in the experimental tests. These were 150 × 150 × 150 mm cubes made of PP-fiber-modified concrete. The lower surface of the specimen was assumed to be fixed in the boundary conditions, while the displacement of the upper wall was applied (as shown in u and v) are calculated, and out-of-plane displacements (w) are determined using triangulation. By using interpolation methods, sub-pixel accuracy is achieved. The output data are a set of displacement maps, which can then be used to calculate strain maps in the  plane [The Digital Image Correlation Method (DIC) enables the measurement of in-plane and out-of-plane displacements and the calculation of object deformations resulting from the load of external forces and environmental forces . The measurement involves taking a series of photos before and after loading the tested object. The surface of the tested object must have a certain random texture (spot structure). Typically, when measuring engineering objects, such a texture should be applied to the object before starting the measurements, which is not acceptable in most cases of works of art; it may be, for example, the natural texture of a painting, in the form of intense color differentiation and/or a clear brush stroke. One of the images in the series is selected as the reference image for all subsequent analyses. The reference image is divided into small rectangular regions, called subsets. The DIC algorithm tracks the position of each subset from the reference image in all other images of the measurement series. Finding subsets is performed by calculating the cross-correlation coefficient. For each subset, in-plane displacement vectors (y) plane ,55,56,57In the laboratory testing program, compression tests were carried out on 150 × 150 mm cubes made of concrete with PP fiber reinforcement. The tests were carried out on a Zwick testing machine equipped with automated control and data recording systems. The specimens were loaded to failure. As the annealing temperature of the test specimens increased, there was a decrease in the nominal stress level but an increase in the strain at failure. In particular, a decrease in the maximum nominal stress level was clearly visible from an annealing temperature of 450 °C . When observing the state of the specimens after the compression test for the specimen in the initial state (A) and for the annealing temperature of 300 °C , there were fractures on the observed specimen front, but there was no clear shattering of the specimens a,b. SignDuration (μs);Rise time (μs);Decay angle (rad);RMS (V);Counts;Counts to peak;Amplitude (mV);Energy (EC);Average frequency (kHz);Reverberation frequency (kHz);Initiation frequency (kHz);Absolut energy (aJ);Signal strength (pVs);Average signal level (dB).Fourteen AE signal parameters were used to create a reference signal database of destructive processes in PP-fiber-modified concrete specimens:2 coefficient, which in each case was not less than 0.9. The evolution of the crack sequence was divided into seven stages based on microcrack and macrocrack levels. The measure of the matching of signals to individual classes was the RK-means algorithm: Linear elastic deformation—class 1 (red square);Microcrack initiation—class 2 (blue rhombus);Growth of microcracks—class 4 (black lower triangle);Coalescence of microcracks—class 5 (yellow upper triangle);Formation of macrocracks—class 3 (green dot);Macrocracks–crack coalescence—class 6 (gray plus);Failure—class 7 (x in pistachio color).The processes were assigned to groups of acoustic emission signals isolated using the Analyzing the graph of the energy distribution of acoustic emission signals of individual classes over time for an exemplary sample from series A , it can Analyzing the graph of the energy distribution of acoustic emission signals of individual classes over time for an exemplary sample from series B , it can Analyzing the graph of the energy distribution of acoustic emission signals of individual classes over time for an exemplary sample from series C , it can Analyzing the graph of the energy distribution of acoustic emission signals of individual classes over time for an exemplary sample from series D , it can As a result of the performed numerical calculations, the values of stresses and strains were determined in simulation-loaded specimens identical to those used in the laboratory tests. The numerical model assumed a displacement of the upper wall of the specimen, the value of which corresponded to the displacement recorded when the maximum force was reached in compression tests. The numerically determined maximum Mises effective stress values and the component of the stress tensor in the compression direction, as well as strains, both effective and in the direction of the compressive force, are shown in The numerically determined levels of effective stress and stress in the direction of the compressive force decreased with increasing temperature at which the PP-fiber-modified concrete cubes were fired. For the specimen without firing, the maximum stress level oscillated around 50 MPa. When the heat was applied to the sample at 300 °C, the stress level was reduced to a value of approximately 30 MPa. A significant decrease in stress was recorded from the firing temperature of the samples of 450 °C. At that point, the stresses were at a level of 6–7 MPa. This is almost an eightfold reduction in stresses with respect to the specimen without heat treatment. As the firing temperature of the PP-fiber-modified concrete increased, the level of numerically determined deformations increased. A notable exception in the analyzed specimens is the case of the concrete cube firing at 300 °C, where, as could be seen from the force–displacement diagram of the crosshead, the maximum force occurred at a higher level of deformation than occurred at the firing temperatures of the analyzed concrete: 450 °C and 600 °C. The contribution of the modifying polypropylene fiber in the firing tests showed a decrease in stress levels with increasing temperature, while an increase in strain values was shown. This was due, among other things, to the contribution of the modifying additive and its role in melting into the concrete at high firing temperatures. This was the result of an increase in the plasticity characteristics of the concrete with the modifying fibers. These results may be of great importance for the planned operation, especially fire operation, of concrete with the analyzed share of PP modifying fibers. Maps of the Mises effective stress distributions for the four analyzed specimens are shown in The laboratory tests were accompanied by image recording of the deformed specimens in order to determine the distribution of effective deformations in the material using GOM software v2022, rev. 157716  of material destruction occurred: linear elastic deformation, microcrack initiation, microcrack growth, microcrack coalescence, macrocrack formation, macrocrack coalescence, and failure.The destructive processes were analogous for samples stored at ambient temperature and those exposed to fire temperatures.The development of destructive processes in the material was associated with the emission of signals with increasingly higher energy levels.The destruction of samples stored at ambient temperatures and those exposed to fire temperatures involved the emission of signals with similar energy.In the case of samples stored at ambient temperature conditions and subjected to fire temperatures of 300 °C (series A and B), the processes occurred sequentially until the components failed. The course of individual classes of acoustic emission signals was close to linear.In the case of samples subjected to fire temperatures of 300 °C (series B), a break in the development and coalescence of microcracks was noted. This fact was associated with the possibility of local strengthening of the material due to the increase in the degree of compactness of the material structure by the melted plastic (PP fibers).In the case of samples subjected to fire temperatures of 450 °C and 600 °C (series C and D), a significantly smaller number of events and a change in their distribution over time were found.In the case of samples subjected to fire temperatures of 450 °C and 600 °C (series C and D), it was found that all destructive processes occurred in steps at certain time intervals. This fact was associated with the increase in the degree of porosity of the material as a result of high temperatures.Through the use of numerical calculations using the finite element method, it was possible to determine the values of stresses and strains in the analyzed specimens from concrete with PP fiber reinforcements.The validity of the numerical results obtained in terms of deformation values was verified by comparing the numerical results and those obtained by analyzing the deforming image of the specimen (DIC).Fire temperatures of 300 °C, 450 °C, and 600 °C reduced the mechanical strength of concrete modified with PP fibers.As the temperature at which the specimen was fired increased, there was a significant decrease in the numerically determined levels of effective stress and the component of the stress tensor in the direction of the loading force. On the other hand, the level of maximum strain increased.Good agreement was obtained between the deformations obtained by numerical calculations and those determined by DIC analysis.Compression of concrete samples modified with PP fibers was associated with the emission of acoustic signals characteristic of various destructive processes occurring in the material.Fire temperatures influenced the change in the number and distribution of acoustic emission signals of individual classes generated during compression of concrete samples modified with PP fibers.Differences in the number and distribution of acoustic emission signals of individual classes occurred at low levels of load and deformation.The analysis of acoustic emission signals according to the energy parameter over time allowed for conclusions about the degree of advancement of the destructive processes taking place in the material structure.The acoustic emission method can be fully useful for monitoring the condition of fiber-modified concrete elements or structures under load. This applies to both materials operated at ambient temperatures and those exposed to fire temperatures.Based on the conducted research and analyses, the following conclusions were drawn:


Corrosion affecting reinforced concrete (RC) structures generates safety and economical problems. This paper is focused on the simulation of corrosion-induced fractures in concrete, whereby non-uniform corrosion growth is taken into account. In particular, the volumetric expansion of rust accumulated around reinforcement bars causes cracking of the surrounding concrete. This phenomenon is simulated using the finite element (FE) method. In the analyses, concrete is described as a fracturing material by using a damage–plasticity model, steel is assumed to be elastic–plastic and rust is modeled as an interface between concrete and steel. The behavior of corrosion products is simulated as interface opening. Two-dimensional FE models of RC cross-sections with 2, 4 or 6 reinforcing bars are considered. Crack formation and propagation is examined. Moreover, interactions between cracks and patterns of possible failure are predicted. The most developed and complex crack pattern occurs around the side reinforcing bar. Conclusions concerning the comparison of results for uniform and non-uniform corrosion distribution as well as the prediction of concrete spalling are formulated. Chloride corrosion of reinforcement is a process that highly devastates reinforced concrete (RC) elements. The reinforced concrete structures infected by corrosion often do not meet the requirements of serviceability limit states (SLS) and sometimes also of the ultimate limit states (ULS), which in the end generates huge expenses. Volumetric expansion of rust accumulated around reinforcement bars causes cracking of the surrounding concrete. In modeling, chloride corrosion is usually represented by pressure uniformly distributed around a bar and acting on a thick-walled concrete cylinder or cubic sample . HoweverIn the presented examples, finite element (FE) models of concrete cross-sections reinforced with 2, 4 and 6 rebars are considered. The numerical simulation of an RC element takes into account the non-uniform distribution of rust. All analyses treat concrete as non-linear, fracturing material and rust as an interface between concrete and steel. Small deformations are assumed. The expanding behavior of corrosion products is simulated as an opening of the interface between steel and concrete. The validation of the model is performed with respect to experiments presented by Andrade et al. in .We start the presentation of the modeling concepts with an overview of the chloride corrosion process in RC. The pH of concrete decreases in time (due to carbonation or change in moisture content). Additionally, free chlorides present in the pore solution are responsible for breaking the passive layer on the reinforcement surface. In real-life structures, corrosion is a result of a combination of many factors. When the pH of the pore solution drops below approximately 12 and the chloride concentration is above a threshold value, the passive layer is decomposed  and a coAlthough much research has been performed on the matter of corrosion, it is still difficult to determine reliably the rust properties. Its mechanical parameters, as well as the phenomena occurring at the contact surface between steel and concrete, need to be idealized. In the literature, one can find simulations with different representations of rust, using, for instance, connector elements , damage Another idea is to represent the rust expansion using the thermal analogy, i.e., an equivalent increase in temperature. Such an approach enables the simulation of both uniform and non-uniform corrosion. For instance, in ,21,22,233.The mass and density of rust can be introduced by the following relations:As mentioned before, the most common model used for the calculation of the mass of steel consumed in the process is Faraday’s law ,3,4,5,25In the paper, the mass of rust is introduced into the model as so-called corrosion level The location of points with passive layer decomposition is random and depends on the porosity of the concrete, properties of pore solution and mechanical influences . The desMany analyses contribute to experimental procedures simulating electro-chemical reactions and rust generation. The laboratory tests are performed in terms of accelerated corrosion, which itself introduces some imperfections when compared to real-life situations ,14,15,33In the case of uniformly distributed corrosion, Equation  can be eIn the case of non-uniformly distributed corrosion, it is much more convenient to use Equation , as it oThe propagation of the cracks caused by corrosion has been analyzed, for instance, in ,40,41,42This paper presents the methodology of numerical simulations of concrete cracking due to reinforcement corrosion. The computations are performed in Abaqus/CAE 2022 software. The initial simulations strongly refer to experimental data presented in  in orderIn the paper, the expanding corrosion products are represented by interface elements placed between respective solid materials. The corrosion interface is shown in The volumetric expansion of rust is introduced into the simulation as an opening interface. It represents a discontinuity in the FE model, as presented in In the calculations, the initial thickness Equation . The traquation  and compression (c), and the effective stress. Since the responses related to tensile and compressive damage are different in concrete, the model implemented in Abaqus characterizes the damage states independently in tension and compression:The evolution of the degradation variable The model is equipped with viscoplastic regularization according to a generalization of the Devaut–Lions approach, see e.g., , in whicμ, cf. . This prSteel is modeled with the classical elastic–plastic model . ElasticAll simulations are performed using the finite element method (FEM). Two-dimensional models of concrete cross-section with steel reinforcement are built in Abaqus/CAE 2022 software within its standard version. In general, the calculation models are composed of three parts, concrete, rust and steel, in different configurations, as presented in The Abaqus calculations are performed for meshes with the approximate size of an element 0.5 mm. The mesh is composed of 4-node plane strain elements for the concrete and steel parts. The rust interface is modeled with 4-node cohesive elements. Since the component materials are represented as inelastic, the Newton–Raphson algorithm is used in the nonlinear computations with an implicit time integration scheme.Another problem to be solved is to create a credible way of applying rust expansion. All three parts are tied together so that all degrees of freedom are transferred from one part to another. The corrosion-induced internal pressure is applied to the surrounding concrete by using substitute thermal expansion of rust. Thus, an artificial temperature increase interpreted as corrosion level is applied to the rust interface. The whole behavior is then governed by expansion parameter To establish the proper value of ented in . Those eented in  have beeThe analyzed specimens Sp1 and Sp2 have a square shape and dimensions 150 × 150 mm. The displacement boundary conditions are applied at the bottom edge so as not to affect the computation results. The reinforcement radius is 8 mm, but the assumed initial rust layer thickness is 0.02 mm, so that the effective radius is 7.98 mm. The concrete covers are 20 mm and 30 mm for the top and side edges, respectively, in case Sp1, while in case Sp2, the cover is 20 mm and the reinforcement is placed in the middle of the specimen width. The configurations and meshes used in the computations of cases Sp1 and Sp2 are presented in For the purpose of simulation, the loss of radius is expressed as the corrosion level according to Equation . This mecker see a. In theIn The simulation has been performed using the concrete model considering only plasticity or the plasticity–damage description. In the second variant, the values of damage parameters are assumed within a range In Since the damaged part does not affect the cracking pattern and the assumed corrosion generates monotonically increasing loading, the rest of the simulation assumes only the plasticity part of the constitutive model, i.e., the damage mode is not activated.Finally, it turns out that The material data employed for specimens Sp1 and Sp2 are also used in the simulation of realistic rectangular concrete cross-sections with different reinforcement positions according to S varied in computations. The particular values of S can be found in In Again, the tensile equivalent plastic strain (PEEQT) distributions indicate the zones where cracking of concrete occurs. In The same configurations (CS1–CS6) and FE meshes are used again, but the corrosion is non-uniformly distributed around the reinforcement, as well as non-linearly applied in time. The non-uniform distribution of rust expansion is realized by the non-uniform distribution of temperature. The corrosion levels are applied in subsequent steps of the analysis at specific points on reinforcement circumference and presented in The cracking patterns obtained for the cases CS1, CS3, CS4 and CS5 with non-uniform corrosion are presented in The cracking patterns for cases CS3–CS5, presented in In In this paper, the issue of concrete cracking due to reinforcement corrosion has been analyzed. The simulations have been performed in Abaqus, and concrete has been modeled using the damage–plasticity material description , with steel as the elastic–plastic material and rust as a cohesive interface. The expanding character of rust has been simulated using substitute thermal expansion of the interface with a traction–separation law. The plastic strains in concrete represent the cracks induced by the expanding interface. The concrete damage–plasticity model needs to be regularized with a viscosity parameter; otherwise, the calculations diverge prematurely.The presented simulations refer to experimental data presented in . The numIn addition to concrete mechanical parameters, the cracking pattern depends also on the spacing of the reinforcement bars. As the spacing decreases, the horizontal crack between rebars is more likely to occur. This can cause spalling off of the whole concrete cover, and then the bond between steel and concrete is impaired. The horizontal crack is observed both for uniform and non-uniform corrosion; however, in non-uniform corrosion simulations, the horizontal crack is less developed. In this case, the cracks are concentrated mainly around the side rebar, causing the corner of the cross-section to spall off.It is worth noticing that for configurations CS4 and CS5, when the bar spacing is 75 or 91 mm, hardly any cracking has been observed around the middle rebar. Thus, for a sample reinforced with many bars, the cracking pattern is not a simple combination of cracks predicted in single rebar specimens, because the processes occurring in the vicinity of the two bars influence each other. It is also mentioned that, in spite of stress redistribution taking place in the cracking history, the influence of the damage component of the CDP model is negligible in the presented simulations.It is emphasized in this context that the proposed modeling methodology enables numerical experiments to support the optimization of the reinforcement bar placement in the beam cross-section. The future work plans contain an extension of the cross-section models to a three-dimensional representation of a reinforced concrete beam. Moreover, the influence of corrosion on the steel–concrete bond-slip relation needs to be investigated.


Potable water and freeze–thaw concrete were adopted as the control group. Changes in the appearance morphology, mass loss, relative dynamic elastic modulus, and compressive strength of the concrete were tested, and the microstructure of the concrete was analyzed by scanning electron microscopy (SEM). The results showed that an admixture of both MK and PPF in the potable water and freeze–thaw cycle test can improve the mechanical properties and frost resistance of concrete. The admixture of PPF can effectively improve the mechanical properties and frost resistance of concrete. However, the admixture of MK failed to improve the mechanical properties and frost resistance of concrete during multi-salt soaking and freeze–thaw. The frost resistance of concrete under multi-salt soaking and freeze–thaw was optimally improved with 10% MK and 0.6 kg/m3 PPF. Its microstructure shows that PPF can effectively inhibit crack propagation and reduce the deterioration of concrete under multi-salt soaking and freeze–thaw. The wide distribution of alpine saline areas in China is faced with two major problems, which are salt intrusion and freeze–thaw. In total, 216 specimens were prepared with 6 kinds of concrete mix proportions in this paper. The effects of the single and compound incorporation of metakaolin (MK) and polypropylene fiber (PPF) of different amounts on the mechanical properties and microstructure properties of concrete were investigated under the dual action of multi-salt (NaCl, MgCl Saline soil is widely distributed in the northwest and northeast of China. The damage caused by chloride, sulfate, magnesium salt, and carbonate to concrete is becoming more and more serious. In addition, freeze–thaw cycles in high/cold environments aggravate the corrosion damage of concrete. In order to solve the problem of the corrosion damage of concrete in alpine saline soil areas, adding mineral admixtures and fiber materials to improve the durability of concrete is the most commonly used low-cost technical measure ,2.Mineral admixtures represented by silica fume have been widely used in concrete ,4,5, but3~1.5 kg/m3, and with the increase in PPF content, the strength damage gradually decreased. Li et al. [To overcome the expansion of internal cracks in concrete, domestic and foreign scholars have incorporated fibers into concrete for modification. The addition of fibers is an effective way to improve the early crack resistance of concrete ,15,16. Ii et al.  believe i et al.  exploredi et al.  conductei et al.  added an3, 0.9 kg/m3, and 1.5 kg/m3) on the compressive strength, mass loss rate, relative dynamic elastic modulus of concrete and its influence on the internal microstructure of concrete were designed under multi-salt soaking with freeze–thaw and potable water with freeze–thaw. The failure mechanism and microstructure mechanism of concrete under multi-salt soaking with freeze–thaw conditions were analyzed, which provides a reference for the engineering design of high-cold saline–alkali corrosion areas.In summary, current research on the freeze–thaw test for fibers and MK incorporated into concrete is mostly focused on the freeze–thaw test under potable water and is less involved in the freeze–thaw test under multi-salt soaking. Concrete under salt erosion and freeze–thaw will face the erosion of corrosive ions and freeze–thaw damage at the same time. The effect has a more complex failure mechanism, which accelerates the process of the deterioration and attenuation of concrete performance. Therefore, based on the engineering practice of the Delingha–Xiangride expressway in Qinghai Province (in China), composite multi-salt soaking was configured according to the concentration of the solution in the field. Considering the incorporation of MK and PPF into concrete, the effects of MK content  and PPF content  were used to the prepare multi-salt solution based on the ion concentration in the construction site of De Xiang Expressway in Qinghai Province , the coAnd then the concrete specimens were moved into a rapid freeze–thaw testing machine  for the V is the longitudinal wave velocity of the ultrasonic wave propagating in the concrete, m/s; T is the ultrasonic propagation time and the unit is s; L is the longitudinal length of concrete, m; E is the dynamic elastic modulus of concrete in GPa; μ is Poisson’s ratio, and μ is generally 0.15 when the material is concrete; ρ is the density of concrete in kg/m3; dE represents the relative dynamic elastic modulus of concrete in%; nE represents the dynamic elastic modulus of the specimen after the freeze–thaw cycles, GPa; and E0 represents the dynamic elastic modulus of the specimen without freeze–thaw, GPa.In the formula, The potable water and freeze–thaw test: The control group of multi-salt soaking with the freeze–thaw test and the soaking solution is potable water. The other test methods are the same as the multi-salt soaking with the freeze–thaw test method.(1)Effect of PPF content3 PPF, 0.6 kg/m3 PPF, 0.9 kg/m3 PPF, and 1.5 kg/m3 PPF) under the condition of multi-salt soaking and potable water. The pictures of the appearance after 0, 25, 50, 75, and 100 freeze–thaw cycles are shown in 3 PPF had better spalling resistance in the salt freezing test.The concrete specimens were mixed with 10% MK Effect of MK content3 PPF  under the condition of multi-salt soaking and potable water. The pictures of the appearance after the freeze–thaw cycles are shown in The concrete specimens were mixed with 0.9 kg/m2, but it reduces the alkalinity inside the concrete while generating hydrated calcium silicate gel. This is very detrimental to the concrete’s resistance to sulfate attack. Therefore, MK cannot improve the frost resistance of concrete in multi-salt solutions.In the water freeze–thaw test, the surface of the specimen after the freeze–thaw cycles was smooth and flat . After 5(1)Effect of PPF contentConcrete quality decreases after freeze–thaw cycles due to spalling damage. Quality loss rate can effectively reflect the appearance of concrete damage. The relationship between mass loss and the PPF dosage of concrete under different freeze–thaw cycles and different freeze–thaw conditions and PPF dosages are shown in 3 had the lowest mass loss rate. And the mass loss rate was much lower than the control group without PPF in all stages of the freeze–thaw cycles. When the number of cycles reached 100, the concrete mass loss rate of the control group was more than five times the mass loss rate of the concrete mixed with 0.6 kg/m3 PPF. This may be due to the better fluidity and more adequate hydration reaction of concrete mixed with 0.6 kg/m3 PPF. And this produces more calcium hydroxide, which can effectively resist the salt solution. When analyzing 3 maintained the lowest mass loss rate at all stages of freeze–thaw cycles under the potable water and freeze–thaw conditions.The mass loss rate of the concrete increased with the number of freeze–thaw cycles for each group under different conditions. And the mass loss rate of the concrete under multi-salt soaking under freeze–thaw conditions was significantly higher than that of potable and water freeze–thaw under the same number of freeze–thaw cycles. The image of the mass loss rate under multi-salt soaking with freeze–thaw conditions is shown in (2)Effect of MK contentThe relationship between the mass loss rate and the MK dosing of concrete under different freeze–thaw conditions and different numbers of freeze–thaw cycles is shown in (1)Effect of PPF contentThe relationship between the relative dynamic elastic modulus of concrete and the number of freeze–thaw cycles under different freeze–thaw conditions and PPF dosages is shown in 3 is the smallest (38.8%), which was lower than that of the control group (54.02%). The maximum loss of the relative dynamic modulus of elasticity (100%) was observed for concrete with PPF dosing of 1.5 kg/m3. Therefore, adding a certain amount of PPF to concrete under multi-salt soaking with freeze–thaw conditions can reduce the loss of relative dynamic elastic modulus. However, too much PPF will increase its freeze–thaw loss, and there is an optimal dosing amount (0.6 kg/m3) under multi-salt soaking with freeze–thaw conditions.The relative dynamic elastic modulus loss under multi-salt soaking with freeze–thaw conditions decreases and then increases with the increase in PPF dosing. After 100 multi-salt soaking with freeze–thaw cycles , the rel3 is the smallest (38.87%), which is lower than that of the control group (58.1%). The relative dynamic elastic modulus loss of concrete with PPF content of 1.5 kg/m3 is the largest (100%). Therefore, adding a certain amount of PPF to the concrete under the condition of potable and water freeze–thaw can reduce the loss of relative dynamic elastic modulus, but excessive dosage will increase its loss, and there is an optimal dosage (0.9 kg/m3) under the condition of potable water and freeze–thaw.The relative dynamic elastic modulus loss of concrete decreases and then increases with the increase in PPF admixture in potable water and freeze–thaw conditions. Under the condition of potable and water freeze–thaw, with the increase of PPF content, the relative dynamic elastic modulus loss decreases first and then increases. After 100 freeze–thaw cycles , the relComparing the two tests, the phenomenon of freeze–thaw damage under partial clear water solution appears more serious. This may be due to the fact that the addition of a small amount of salt solution will react with calcium hydroxide in concrete. The generated aqueous solution reacts with the unhydrated cement particles in the cement. Therefore, the content of calcium hydroxide in the concrete is reduced, making the interface transition zone harder and increasing the strength of the concrete.(2)Effect of MK content2+, SO42−, and Cl−, which will cause erosion inside the concrete. Also, the concrete was mixed with 0.9 kg/m3 PPF, while the adhesion of the fiber to the cement paste was poor. This may provide a channel for the penetration of solutions and aggressive ions, making it easier to enter the concrete [− penetration. However, the corresponding mitigation effect of chloride salt on sulfate corrosion is also reduced. The chemical corrosion reactions of Mg2+ and SO42− on concrete promote each other, pushing its microcrack development and accelerating the freeze–thaw damage effect. The relative dynamic elastic modulus loss increases with the increase of MK doping under multi-salt soaking and freeze–thaw conditions. After 100 freeze–thaw cycles , the conconcrete . And the2+ and SO42− on concrete promote each other, pushing its microcrack development and accelerating the freeze–thaw damage effect.Under the condition of potable and water freeze–thaw, with the increase in MK content, the relative dynamic elastic modulus loss decreased first and then increased. After 100 freeze–thaw cycles , the relIn summary, the addition of MK does not reduce the loss of relative dynamic modulus of elasticity of concrete under multi-salt soaking with freeze–thaw conditions. And the loss of relative dynamic elastic modulus increases with the increase in MK doping. The appropriate amount of MK can reduce the loss of relative dynamic modulus of elasticity of concrete under freeze–thaw conditions of potable water. However, too much MK will increase its loss, and there is optimal dosing (10%) under potable and water freeze–thaw conditions.(1)Effect of PPF contentDuring the freeze–thaw cycle, concrete is subjected to freeze swelling, ice crystal pressure from NaCl and chemical corrosion. These factors can further develop their internal pre-existing cracks. With the increase in the number of freeze–thaw cycles, the cracks inside the specimen gradually increase and penetrate each other, ultimately reducing the load-bearing capacity of concrete .The relationship between the compressive strength loss rate and the number of freeze–thaw cycles of concrete under different freeze–thaw conditions and PPF dosages is shown in 3 and the maximum compressive strength loss (72.5%) was observed for the control group. Therefore, the addition of PPF to concrete under salt freezing conditions can reduce the loss of compressive strength. Optimal dosing (1.5 kg/m3) exists under salt-freezing conditions.Compressive strength loss decreases, then increases and then decreases with the increase in PPF dosing under multi-salt soaking and freeze–thaw conditions. After 100 freeze–thaw cycles , the min3 showed not only no loss but also an increase. The reason for this may be the addition of the right amount of PPF being due to the small density of fibers, and a number of reasons such as the formation of a dense “fiber network” inside the concrete. It reduces the pore connectivity in the concrete and makes the interior of the concrete denser, which alleviates the uneven distribution of internal stress in the concrete and finally effectively alleviates the loss of compressive strength of the concrete. The maximum compressive strength loss of concrete with PPF dosing was 1.5 kg/m3 (65.07%). Therefore, the addition of PPF to concrete under clear water and freeze–thaw conditions can reduce the loss of compressive strength, and the optimum admixture level (0.9 kg/m3) exists under clear water and freeze–thaw conditions.The compressive strength loss increases, then decreases and then increases again with the increase in PPF dosing under potable and water freeze–thaw conditions. After 100 freeze–thaw cycles , the com(2)Effect of MK contentThe relationship between the compressive strength loss rate and the number of freeze–thaw cycles of concrete under different freeze–thaw conditions and the PPF dosage is shown in − penetration can be effectively improved with the increase in MK [2+ and SO42− on concrete promote each other, driving the development of its microcracks and accelerating the freeze–thaw damage effect.We observed increasing compressive strength loss with increasing MK dosing under multi-salt soaking with freeze–thaw conditions. After 100 freeze–thaw cycles , the smase in MK . However2 produced by cement hydration and increase the content of cementitious materials in the hydration products and promote the formation of hydration products containing aluminum phases, thus filling the internal pores of concrete, which is conducive to the improvement of the concrete’s properties. The compressive strength loss decreases and then increases as the amount of MK increases under potable and water freeze–thaw conditions. After 100 freeze–thaw cycles , the comThe maximum compressive strength loss (65.07%) was observed for the concrete with 15% MK dosing. The compressive strength of concrete mixed with MK at 10% increased at all stages of the cycle. The compressive strength increased and then decreased as the number of freeze–thaw cycles increased. Therefore, the addition of MK to concrete under potable and water freeze–thaw conditions reduces the loss of compressive strength, and an optimum admixture level (10%) exists.To further investigate the internal microstructure of the concrete under the compounding of PPF and MK under salt freezing, typical specimens of each group of concrete were selected for electron microscopy scanning. The microstructure diagrams are shown in (1)The influence of freeze–thaw cycles and PPF content under multi-salt soaking with freeze–thaw conditions.When PPF was not incorporated, the concrete was well hydrated and structurally dense before freezing and thawing a. With tWhen PPF was incorporated, compared to the concrete without PPF b,d for t(2)The influence of freeze–thaw cycles and MK content under multi-salt soaking with freeze–thaw conditions.When not mixed with MK, a large number of hydration products are in the concrete before freezing and thawing the dense structure a. With t− ions. Therefore, the hydration reaction of concrete is weakened after MK replaces the cement, and the content of Ca(OH)2 generated by hydration is reduced. The decrease in free OH- in the pores of concrete leads to a decrease in the PH value, which destroys the stable environment for the existence of hydration products. Some of the hydration products’ structural damage occurred during decomposition [When MK was added, compared with the concrete without MK b,d, undeposition , concret3 PPF after 100 freeze–thaw cycles increased by 12.47% under potable water and freeze–thaw conditions, and its loss of compressive strength was 59.65% under salt freezing conditions.Compared to potable water freezing and thawing, salt freezing is more corrosive to concrete materials. The compressive strength of concrete with 0.9 kg/mThe changes in appearance, quality, relative dynamic modulus of elasticity and compressive strength under multi-salt soaking with freeze–thaw conditions are a good reflection of the damage to the concrete. A combination of the four can be used as a criterion to determine concrete damage.PPF can effectively enhance the erosion resistance of concrete under multi-salt soaking with freeze–thaw conditions. MK can only improve the erosion resistance of concrete under potable water conditions. The relative dynamic modulus of elasticity of concrete with 10% MK was 54.46% at 100 cycles of freezing and thawing in potable water, which was much higher than that of the control group (22.32%) without MK.Concrete with a small amount of PPF added under salt freezing conditions had fewer cracks after a comparative analysis of the SEM images. Fibers can effectively assist the concrete to resist stress, inhibit the expansion of cracks, and improve the concrete’s resistance to freezing and thawing. The addition of MK destroys the alkaline environment inside the concrete and reduces the generation of hydration products resulting in the weakened ability of concrete to resist multi-salt soaking with freeze–thaw tests.Improvement to the erosion resistance of concrete by multiple admixtures including PPF and MK can be considered in future salt freezing studies.The effects of MK and PPF dosing on the physical and mechanical properties and microstructure of concrete under multi-salt soaking with freeze–thaw and potable water freezing and thawing conditions were investigated. The following conclusions were obtained:


Genovese) production. We assessed edible biomass, nutrient bioaccumulation, and LUE. Nine light treatments included: one non-supplemented natural light (NL) control, two end-of-day (EOD) HPS treatments applied for 6 h and 12 h, five EOD 20B/80R LED treatments applied for 3 h, 6 h, 9 h, 12 h, 18 h, and one continuous LED treatment (24 h). Each SL treatment provided 100 µmol·m-2·s-1. The DLI of the NL control averaged 9.9 mol·m-2·d-1 during the growth period (ranging from 4 to 20 mol·m-2·d-1). SL treatments and growing seasons significantly impacted biomass and nutrient bioaccumulation; some SL treatments had lower yields than the non-supplemented NL control. January growing season produced the lowest fresh mass (FM) and dry mass (DM) values compared to November, which had the highest. Mineral analyses revealed that both growing seasons and lighting types impacted macro and micronutrient accumulation. Additionally, the efficiency of each treatment in converting electrical energy into biomass varied greatly. EOD supplements using LED and HPS lighting systems both have merits for efficiently optimizing yield and nutrient accumulation in basil; however, biomass and nutrient tissue concentrations highly depend on seasonal variation in ambient sunlight in conjunction with a supplement’s spectral quality, DLI, and application schedule.Three primary factors that impact plant growth and development are light quantity, quality, and duration. Commercial growers can manipulate these parameters using light-emitting diodes (LEDs) to optimize biomass yield and plant quality. There is significant potential to synergize supplemental lighting (SL) parameters with seasonal variation of ambient sunlight to optimize crop light use efficiency (LUE), which could increase biomass while reducing SL electricity costs. To determine the best lighting characteristics and durations for different crops, particularly for enhancing the yield and nutritional quality of high-value specialty crops produced in greenhouses during the winter, a thorough efficacy comparison of progressive incremental daily light integrals (DLIs) using LED and high-pressure sodium (HPS) sources is required. The purpose of this study was to compare the effects of differential application timing and DLIs of supplemental blue (B)/red (R) narrowband wavelengths from LED lighting systems and HPS lamps on greenhouse hydroponic basil  Other s , as well as other specialty crops  and red/far-red photoreceptors (phytochromes) are known to have a significant role in the synchronization of circadian oscillations to light/dark cycles . PhotosyTo date, there are no published studies that compare narrowband B/R and HPS SL application timing and duration across growing seasons in terms of yield, nutrient uptake, and electrical efficiency. Because horticultural lighting is energy-intensive, it is pertinent to develop lighting strategies to maximize the conversion of SL electrical consumption to biomass. There is significant potential to synergize SL parameters with seasonal variation of ambient sunlight to optimize crop LUE, which could optimize biomass and nutritional quality while reducing SL electricity costs. Due to its high demand and flavor preference, ‘Genovese’ basil makes an excellent model crop to use for light experiments and could predict the impacts of light spectral quality/intensity on other high-value specialty crops (both at the primary and secondary metabolic level), specifically those in the Lamiaceae family .We hypothesize that manipulating supplemental lighting quality, application timing, and duration under standard commercial growing conditions has the potential to significantly influence yield, micronutrient bioaccumulation, and LUE of sweet basil across growing seasons. The primary objective of this project was to determine the seasonal impact of application timing and duration of low-intensity EOD SL using specific narrow-band blue (B) and red (R) wavelengths (447 ± 20 nm B and 627 ± 20 nm R) from solid-state LED lighting systems and broadband HPS lamps on edible biomass yield, nutrient bioaccumulation, LUE, and other pertinent energy efficiency metrics of hydroponically grown greenhouse basil. It will be advantageous to establish specific-specific optimal SL protocols  that optimize LUE via manipulating crop physiology and circadian rhythms; this provides an opportunity to improve the electrical efficiency of commercial greenhouse SL, while increasing yields and nutrition quality.22.1This present study was conducted at The University of Tennessee Institute of Agriculture (UTIA), which is located in Knoxville, TN, USA . All experiments were conducted under Venlo glass research greenhouses using ebb-and-flow hydroponics. Growing dates for four experimental runs occurred from September 2016 to June 2017. These four experimental runs are labeled as growing seasons.2.2Emphasis was placed on investigating biomass yield, nutrient bioaccumulation, and LUE in response to differing EOD SL application timing, duration, and spectral quality. This was accomplished using narrowband blue/red  LED light and broadband HPS light applied at equal photosynthetic photon flux densities (PPFD) for different incremental lengths of time across different growing seasons. The 20B/80R LED lighting ratio was specifically chosen for this experiment because of its prevalence in recent literature; it was also deemed optimal for a variety of growth and development parameters from a previous experiment in our group .A total of nine lighting treatments were added immediately after seedling transplantation: one non-supplemented NL control (ambient sunlight only), two HPS treatments applied at 6 h and 12 h per day , and six 20B/80R LED treatments applied at 3 h, 6 h, 9 h, 12 h, 18 h and 24 h per day . SL regimes for all treatments were initiated each day 1 h before sunset . Sunset time averages and average daylengths can be found in -2·s-1 for its respective duration . LED treatments were 1 m above the hydroponic system, and HPS lamps were 1.5 m above hydroponic systems throughout experiment (post-transplantation). As crops grew, SL intensities were adjusted using dimmers to the target intensity 4-5 times per week (after dark) using a PS-200 Apogee Spectroradiometer . Leaf temperature variance across treatments was ± 0.4°C from average at canopy surface. The Orbital Technologies LED systems consisted of 10 equally spaced meter-long alternating blue/red bars with adjustable spectral and intensity control, designed to uniformly illuminate 1.2 m x 1.2 m . Dimmable HPS lamps were placed in targeted reflectors to reduce SL treatment bleed-over and allow for precise intensity control and uniformity across the 1.2 m x 1.2 m treatment areas. Spectra of lighting treatments and background solar energy have been provided in Each SL treatment uniformly provided 100 ± 2.5 µmol·m-2·s-1 SL bleed-over at the treatment edges). 1.2 m x 1.2 m sections of basil were grown, with 1.2 m separation between treatments . Tissue samples for all analyses were only harvested from within the middle 0.6 m x 0.6 m of each treatment to ensure further reduction of SL contamination between treatments (0.3 m around the edge of each treatment was considered the buffer zone and was not used for sampling). Within the harvest zones of adjacent treatments, SL bleed-over was <0.1 µmol·m-2·s-1 . Under these circumstances, SL treatment bleed-over was deemed non-significant; therefore, physical barriers  were not utilized because of potential deleterious experimental effects . SL treatments were randomized each season to eliminate the potential for DLI and air temperature variability within the greenhouse bay.Each SL treatment was physically separated to ensure no bleed-over effects between SL treatments  were analyzed in each treatment . Each experimental cycle was repeated across four growing seasons . Replicates (6) were nested within treatments (9), which were nested within growing seasons (4).2.3Because of its distinctive flavor profile, high market demand, and popularity among chefs, ‘Genovese’ sweet basil was chosen. ‘Genovese’ basil seeds  were germinated in peat moss-based cubes  under ambient sunlight maintained at 28.3°C and 95% RH. Seeds and sponges were suspended in plastic float trays above 1 L tap water in within humidity domes and trays .After 2 weeks in the humidity domes, seedlings were transplanted into plastic pots (8 cm × 8 cm × 9 cm) using 1 part peat moss  to 3 parts perlite  potting mix.-2·d-1 across all four growing seasons (daily average ranging from 4 to 20 mol·m-2·d-1). Each hydroponic system (treatment) received similar amounts of cumulative ambient sunlight (DLI of ± 0.5 mol·m-2·d-1 across treatments) throughout the four growing seasons, in addition to the prescribed SL regime. Relative humidity during the growth period averaged 55%.Day temperatures averaged 28.1 ± 1.5°C, and night temperatures averaged 21.3 ± 0.4°C. DLI of the natural light control  averaged 9.9 mol·mSpecific growing parameters for each of the seasons may be found in All basil plants were grown in ebb-and-flow hydroponic systems and sub-irrigated for 5 min each day with full-strength general mix nutrient solution; the fertility regime was kept constant across the duration of all seasons. Total growth time lasted approximately 45 d across all 4 experimental runs (seasons). The nutrient solution was kept consistent at 5.9 ± 0.1 pH and 2.0 ± 0.1 dS/m, changed at least weekly. Nutrient solution consistent of a modified Hoagland solution using fertilizer grade mineral salts. Each bench (three treatments) had its own closed nutrient reservoir.Nutrient solution samples were analyzed throughout each experiment to ensure consistent nutrient composition across reservoirs and seasons. Water samples were taken twice weekly in 15 mL sterile test tubes. A 9.9 mL of acid matrix solution  was placed into 15 mL sterile test tubes. A disposable 1 mL plastic pipette was used to add 0.1 mL of the homogenized nutrient solution sample to the 9.9 mL acid matrix solution. This mixture was then thoroughly shaken to ensure that the nutrient solution sample was uniformly distributed within the matrix. An Agilent 7500 Series Inductively Coupled Plasma Mass Spectrometer (ICP-MS) was used to determine the concentrations of each nutrient solution sample . Average2.4Plants were harvested at physiological vegetative maturity  for each growing season. 2.5To determine changes in elemental nutrient tissue concentrations in basil plants across SL treatments and growing seasons, samples were analyzed for macro and micronutrient concentrations according to a method from 2.6Energy efficiency and cost efficacy calculations of EOD SL were evaluated for hydroponically grown greenhouse basil. Efficiency values are calculated on both a per-plant FM basis  and a full system FM basis . LUE was calculated on a per-plant DM basis. All calculations (except LUE) are based on statistical averages across all four growing seasons intended to determine generalized efficiency parameters representative of a year-round growing operation under standard greenhouse conditions; LUE is evaluated by treatment and growing season individually.The calculations in this study only consider the cost of energy consumed by lighting fixtures; calculations do not include other greenhouse sources of energy consumption, service charges from electricity providers, lighting fixture purchase, or maintenance, which are all important factors when deciding SL types and regimes.-1) was calculated based on the time in hours (h) each treatment was provided and the electrical requirement of the energy fixture in Watts (W).First, daily SL electrical energy input (kWh·dT) was calculated by multiplying the daily electrical input (kWh·d-1) per treatment by the number of days (d) per growing cycle.Next, the total SL electrical energy input per harvest cycle (kWhT) was then determined based on the current electrical rate in Knoxville, TN. Electrical energy was provided to our growing facility by Knoxville Utility Board (KUB) at the current rate of $0.10 kWh (USD per kWh).The total SL energy cost per growing cycle (USDSL) and the total perceived DLI  were calculated using SL treatment instantaneous photosynthetic photon flux density (PPFD) of 100 µmol·m-2·s-1, treatment duration sTD, and known average DLI received inside the greenhouse.The DLI provided by each SL treatment per day (DLIandT) was also calculated for each treatment, which was the total amount of time within a 24 h period that a treatment received light . One hour is subtracted from hSL because treatments were initiated one hour prior to sunset. Maximum hT is equal to 24 h .The average perceived daylength (hɡ·DLI-1) was calculated based on the yield and total DLI average received by each treatment.Biomass efficiency (BE) is a measure of the conversion of light energy by a crop into biomass. Per plant biomass efficiency (ɡPPY) was calculated, which is useful for comparing the impact (positive or negative) of SL treatments with the non-supplemented control. It is the yield difference (ɡ) of the non-supplemented NL control (ɡNL) and each SL treatment (ɡSL).Average per plant yield increase over NL control (ɡTSY) was also calculated, which is the fresh mass difference (ɡ) of the total FM of the non-supplemented NL control (ɡTNL) and total FM of each SL treatment (ɡTSL). This value provides a reference point to determine the efficiency of each SL treatment’s ability to convert electrical energy to FM increases over the NL control with respect to the entire 1.2 m x 1.2 m hydroponic system.Average total system yield increase over NL control (T) required per g increase of total system FM  increase over the NL control (ɡTSY).The SL energy input per total system yield increase (Positive ɡTSY) per dollar in SL electrical energy (USDT).To quantify in dollars, the total system yield increase per SL energy cost  indicate higher yield losses per USD of electricity spent. Large positive values are ideal, which indicates high-cost efficacy in terms of energy conversion to FM increase over NL control.Finally, light use efficiencies  were calculated for each lighting treatment . Design and Analysis macro  was utilized in addition to Tukey’s (protected) adjustment, regression analysis, and univariate/normalization procedures. Treatments and seasons were separated by least significant difference (LSD) at α=0.05.3-1 DM and micronutrients in µg·g-1 DM), and energy efficiency calculations.Fresh mass (FM) and dry mass (DM), as well as the nutrient concentrations of edible tissue, were evaluated in this experiment. Data presented include plant weights (g), mineral concentrations , spectral quality variations, and natural DLI provided across growing seasons will be discussed 5, 6.P ≤ 0.0001; F=62.23) and season  but did not show significant season*treatment interactions . When comparing yield across LED treatments, a clear sigmoidal pattern is observed. HPS lighting treatments generally performed better than LED treatments. The 6 h and 12 h HPS treatments had higher FM than most of the LED treatments, showing a 27% increase over the NL control  and season  but not by season*treatment interactions . HPS lighting treatments 6 h and 12 h again produced the two highest DMs across all growing seasons, averaging 6.8 g and 5.9 g DM per plant, respectively  and season  but did not show season*treatment interactions . There were elevated levels of P in the 12 h LED treatment and decreased levels in the 6 h LED treatment; however, most of the treatments did not statistically separate, except for the two previously mentioned  and season*treatment interactions  but not by lighting treatment . Plants grown in January had significantly higher K concentrations, while none of the other seasons were statistically different , season , or season*treatment interactions  , season , and season*treatment interactions . The highest treatment tissue concentrations of S were 24 h LED and 6 h HPS, while the lowest treatment was 6 h LED , season , and season*treatment interactions . Mg concentrations in the 18 h LED treatment and the 6 h HPS treatment were found to be higher in comparison to the 6 h LED treatment; however, there was variation across treatments, and many did not statistically separate , season , and season*treatment interactions . The 9h LED treatment had the highest B concentrations across all growing seasons, while the lowest was observed under the 6 h LED treatment , season , and season*treatment interactions . The lowest Cu concentrations were found in the NL control and 24 h LED , season , and season*treatment interactions . 12 h LED had higher concentrations than 6 h LED, but the other treatments did not statistically separate , season , and season*treatment interactions . 9 h LED had statistically greater tissue concentrations of Fe as compared to the 12 h HPS and NL control, while the other treatments did not separate , season , and season*treatment interactions . The 6 h LED treatment had the highest concentrations, while the lowest was found in 6 h HPS. The NL control fell between the Na tissue concentrations range for this experiment  and season , but no significant season*treatment interactions  were observed. The 9 h LED treatment and NL control were the only two Zn tissue concentrations that statistically separated  compares all treatment FMs to the NL control FM, which allows the ability to incorporate positive/negative values for later calculations. LED 18 h, 24 h, and HPS 6 h and 12 h had increased yields over the NL control, while other treatments had reduced yields. Average plant yield increase over NL control ranged from 13.60 g (HPS 6 h) to -18.50 g (LED 9 h) (The average plant yield increase over NL control (gLED 9 h) Table 7.TSY) is related to the average plant yield (gPPY) and represents the total FM (positive or negative) yield as compared to the NL control. This value is necessary for total-system energy efficiency calculations. The LED 18 h, 24 h, and HPS 6 h and 12 h treatments had increased over the NL control, while other LED treatments had reduced yields. Average total system yield increase over NL control ranged from 660.0 g (HPS 6 h) to -910.0 g (LED 9 h)  Table 7.T·ɡTSY-1) represents the amount of SL electrical energy required per gram of total system FM increase over the NL control (-1 (HPS 12 h) to -0.28 kWh·g-1 (LED 12 h). Half of the treatments (LED 3-12 h) were negative, indicating a decrease in the total system yield below the NL control (despite paying for SL electricity), while the other half (LED 18-24 and HPS 6-12) increased total system yield and various rates .SL energy input per total system yield increase kWhT·ɡTSY-1 repres-1) was calculated (-1 (LED 18 h) to -182.70 g·USD-1 (LED 6 h). In other words, the LED 18 h treatment was the most cost-effective in terms of increasing total system yield, while the LED 6 h treatment was the least cost-effective treatment and actually led to significant losses in total system yield.To quantify SL electricity usage in dollars, the total system yield increase per SL energy cost  and season . LUE was statistically highest for the HPS 6 h, HPS 12 h, and NL control. The many of lowest values were found under the LED treatments between 6 h and 24 h  across all growing seasons evaluated. It was significantly higher than the NL control and many of the LED treatments (Lactuca sativa). Other experiments have shown that increased DLI is correlated with increased FM and DM  in a controlled environment production system , the 6 h LED treatment had 53% less yield than the 6 h HPS treatment. The 12 h LED treatment had 69% less yield than the 12 h HPS treatment. Increasing SL duration from 6 h to 12 h significantly increased the yield for the LED treatments, but it did not significantly change the yield between the HPS treatments. Additionally, the 6 and 12 LED treatments did not improve yields over the NL control (Cryptochromes (CRYs) are blue light pigment-proteins (photoreceptors) that regulate light-mediated plant growth and development . CRYs arArabidopsis, a suite of five photoreceptor classes provides the ability to perceive minor variations in spectral quality ranging from ~280 nm to 780 nm , blue light induces stomatal opening, while red light is ineffective; as PPFD increases, stomatal opening is consistently higher for blue light than red light under concurrent PPFD, making the process more sensitive to blue wavelengths  and increases in net biomass accumulation. Based on the data and literature currently availability, we believe a combination of these factors resulted in unexpected FM/DM, as well as the nutrient bioaccumulation interactions between treatment and season.The combination of circadian rhythm, temperature, and light-induced stomatal were likely significant factors for unexpected trends in biomass production and nutrient accumulation. Additional experiments are needed to verify this speculation. While temperature variation is known to induce stomatal opening, one important factor that regulates stoma position is blue and red wavelengths . At low elengths . In addielengths . Transpi4.4Electrical energy, specifically used for SL, is one of the top three most expensive business costs of common commercial greenhouse operations . MaximizOne strategy to improve the efficiency of SL includes applying different spectral qualities of light EOD to extend daylength and increase DLI which, in theory, should improve yields/nutritional quality. SL energy input per yield increase and total yield increase per SL energy cost values represents the efficiency of additional SL light to yield increases in terms of electrical energy used and price. It was interesting to see that many of the provided treatments were not an efficient use of electricity. In some of the LED treatments, the values were negative, meaning that the energy provided unexpectedly decreased crop yield; in other words, money could have been saved and basil crop yields increased by just using natural sunlight and not applying some SL treatments. This demonstrates that SL applicating timing and spectral quality is a critical factor when considering electrical efficiency. Not all SL treatments are guaranteed to improve yields, and some could even be detrimental to both yields and business operating expense.Light use efficiency (LUE) is a metric that reflects the total amount of carbon assimilation that occurs during a plant’s life cycle relative to the amount of light intercepted by a plant, typically measured in terms of the ratio of mass to mols of absorbed photosynthetically active radiation (PAR). This metric is essential for understanding the efficiency of light energy conversion into biomass production in plants. The blue (400-500 nm) and red (600-700 nm) regions of the spectrum are particularly important for photosynthesis, as they correspond to the absorption peaks of chlorophyll pigments. However, the green-yellow region (500-600 nm) is less efficiently utilized due to the lower absorbance of chlorophyll in this range, leading to a lower LUE in this spectral region.This experiment found many of the EOD LED treatments were not an efficient use of electrical energy when compared to the control. Many of the lower-DLI treatments caused significant reductions in yield and LUE, while also consuming electrical energy. We expected that increasing DLI would improving the yield regardless of the lighting type or application timing, but the results show that both application timing and spectral quality of SL are equally as important as DLI and energy efficiency of SL system. Spectral quality of light can also influence LUE by affecting various aspects of plant physiology, such as the rate of photosynthesis, photomorphogenesis, and circadian rhythms. By understanding the relationship between LUE and spectral quality, researchers can optimize lighting systems for plant growth, improve crop yield, and develop more efficient horticultural practices.As discussed previously, HPS lights emit a broad spectrum of light with a strong emphasis on red and yellow wavelengths, which are beneficial for plant growth during the flowering stage. However, HPS lights have a lower spectral output in the blue wavelength range, which is crucial for vegetative growth. LED lights can be designed to emit specific wavelengths of light tailored to various stages of plant growth. They can also provide a balanced spectrum of blue, red, and far-red light, which can be adjusted according to specific crop needs. The differences in spectral output between HPS and LED lights can affect the photosynthetic efficiency of plants. LED lights can potentially provide a more targeted spectral output that closely aligns with the absorption peaks of chlorophyll a and b, leading to more efficient photosynthesis. This targeted spectral output can also reduce the amount of wasted energy from light that is not absorbed by the plant, increasing overall energy efficiency.-1). Due to their targeted spectral output and lower heat production, LED lights generally have a higher PPE than HPS lights. LEDs are inherently more efficient than HPS lamps at converting electrical energy into light energy. LEDs have significant potential for decreasing energy costs for SL while improving yields and nutritional quality, but this study indicates lighting regime is just as important as considering the energy consumption and PPE of any given lighting system. It should be noted that the electrical efficiency of SL systems is highly dependent on a number of other factors that were not discussed or evaluated in this experiment. Some of these factors include growing facility location and setup, lighting fixture type, crop species and variety, optimization of standard controlled environment agriculture parameters , plant spacing, adequate ventilation, and fertility regime.Energy efficiency in horticultural lighting systems is typically measured in terms of photosynthetic photon efficacy (PPE), which is the ratio of the photosynthetically active radiation (PAR) output to the electrical input power  differentially influenced biomass, nutrient bioaccumulation, and LUE. These unexpected findings did not align with our original expectations and prompted us to speculate on alternative explanations for the observed outcome. These results establish a proof-of-concept for low-intensity EOD SL, and open up exciting opportunities for future research; specific physiological mechanisms discussed in this manuscript should be replicated and verified in future experiments using further analytical and molecular techniques.An important factor in primary metabolism and circadian rhythm is plant temperature. While energy costs of heating and cooling were not evaluated in this study, greenhouse temperature maintenance and optimization are vital for successful, efficient, and sustainable crop production. It is well known that LEDs produce significantly less radiant heat energy than HPS lighting systems . Most ofHPS lighting sources contribute more radiant heat energy to the canopy’s surface temperature than LEDs, which may prove useful during cold months by increasing photosynthetic rates as compared to plants without that additional heat. Increased leaf temperatures from infrared (IR) wavelengths will directly increase leaf temperatures as well as metabolic activity and transpiration. While it is more energy-efficiency to raise plant temperatures using typical greenhouse heating systems to raise ambient temperature, in some cases, higher canopy temperatures may prove advantageous for yield optimization. IR wavelengths from HPS sources may conversely prove harmful for plants with low leaf temperature requirements, especially during summer months with high light intensities and ambient temperatures, resulting in heat stress and photodamage. Additional considerations for greenhouse cooling systems and continual adjustments to ambient air temperature may be required to keep canopy temperatures consistent across the day and night periods, requiring additional ventilation strategies or specific on/off schedules.Excess radiant heat, in the form of infrared (IR) wavelengths, produced from HPS sources during warm growing seasons may explain why changes to FMs and DMs were not as pronounced during these seasons, as heat stress is known to reduce biomass and induce thermomorphogenic responses. It is possible that excess IR wavelengths hindered optimal photosynthetic rates, in addition to variance in day/night temperatures between experimental treatments that may have influenced FM/DM. By extending/increasing night temperatures, HPS treatments may have increased metabolic rates, but not allowed for a cooler rest period overnight, leading to a stagnation in yield between the 6 h and 12 h HPS  to verify treatment environments were similar. HPS lights were hung at a higher distance to reduce the likelihood of increased leaf temperatures. 24 h continuous leaf temperature measurements would have allowed for precise record of any discrepancies among treatments and should be investigated further . While we did not investigate air temperature or leaf temperatures under the different SL regimes, it would be valuable to evaluate the influence of temperature microenvironments from SL sources within greenhouse spaces across different seasons.P=0.1235; F=9.62). That being said, there are clear visual patterns that suggest season*treatment interactions . Mixed Model ANOVA and GLIMMIX statistical procedures (treatments nested within seasons) indicated season significantly influenced FM, but did not show significant season*treatment interactions  to elucidate DLI/lighting period duration effects across growing seasons would be another potential strategy and help isolate the variable of SL intensity; however, it would be difficult under standard greenhouse conditions because the PPDF, DLI, and photoperiod of ambient sunlight are constantly changing, and this type of experiment would ideally be performed in growth chambers. It is extremely difficult to precisely control of DLI from ambient sunlight in greenhouses . That being said, it is very simple to supplement ambient sunlight with SL and is more applicable to commercial growers. Because the ambient sunlight cannot be controlled precisely, we decided to take the approach of not trying to control the sun; rather, control the SL applications and see how they interact with the ambient solar spectrum as it changes over the year. We believe both approaches have merits and should be used together in order to elucidate effects from each of the pertinent lighting parameters.Irrespective of electrical cost, the FM and DM results of this study suggest narrowband B/R is much better applied during the daytime or full 24 h, while the HPS is better applied at night for 6 h; LED treatment yields began to improve above the control after daylight hours, while the 6 h HPS treatment did not see yield improvements despite adding an additional 6 h of EOD SL. It is likely that the natural solar spectrum was optimized during daylight hours by providing specific narrowband B/R wavelengths, which are primary drivers of photosynthesis and promote several physiological responses. Narrowband wavelengths at night may have boosted yields if other wavebands within the visible spectrum were included . Further, 18 h and 24 h LED SL may have overridden endogenous circadian rhythm, or the continuous application (no dark period) failed to disrupt the balance of light-dependent and independent reactions significantly. Because photosystems were kept active 24 h per day, light-dependent reactions were able to occur nonstop . On the other hand, maintaining a natural day length  with higher intensities of SL may be useful for synchronous light/dark reactions, and increased biomass accumulation, given that sufficient DLI and spectral quality requirements are met. These results suggest that light schedule and exposure length of SL are equally important as DLI for biomass accumulation. While the intention of this experiment was to investigate the use of SL under commercial greenhouse conditions, multi-year tandem experiments with sole-source lighting in growth chambers would prove useful to further elucidate other spectral quality effects and eliminate confounding factors . Future studies should also consider the development of lighting protocols that are optimized for across different high-value specialty crops that incorporate plants with/without photoperiod requirements during commercial production as well as crops with species-specific tolerance to 24 h lighting periods .In this study, changes to the spectrum, DLI, and application timing of SL lighting differentially regulated the absorption of mineral nutrients. Recent experiments have evaluated the effects of narrowband wavelengths on nutrient uptake with mixed effects, highly dependent on lighting type and species . The priPotential advantages for production can be achieved by manipulating PD or EOD light in a controlled environment; the most notable, however, has been achieved through manipulations of photoperiod and/or DLI . Multipl5The results of this experiment clearly indicate that SL spectral quality, DLI, and application timing greatly influence fresh/dry yields, nutrient uptake, and SL energy efficiency in greenhouse hydroponic basil cultivation. Across all seasons, HPS lights provided optimal results for both fresh/dry edible biomass yield (25-29% over control), while 9 h to 18 h LED treatments significantly increased the uptake of many macro- and micronutrients when compared to HPS and natural light controls.-1. Lighting type  and application timing were significant factors in terms of biomass accumulation, nutrient uptake, and electrical efficiency. In general, PD-blue and EOD-red wavelengths were beneficial for yield increases. SL treatments had different effects across growing seasons, due to changes in the spectral quality, DLI, and daylength of ambient sunlight.For all parameters considered in this study, the optimal supplemental DLI ranged from 4.2-6.3 mol·dIn our efficacy comparison, LEDs and HPS have proven merits, but both systems have limitations in regard to nutrient cycling and sustainability under controlled environments. Biomass efficiency across treatments varied two-fold. When considering SL energy costs, LED 18 h was the most cost-effective treatment for increasing mass. Additional efficacy comparisons between HPS and LED lighting systems should be conducted on a variety of physiological metrics to determine economically favorable practices. Plant quality and other secondary metabolic interactions were not evaluated in this experiment and should be considered for future experiments; while increased yields are important, secondary metabolites and quality attributes are also important for consumer acceptance and preference. Using metabolomic and transcriptomic methodologies, future studies should investigate these types of lighting regimes to determine responsible physiological and biochemical mechanisms and how those can be leveraged to increase yields and nutritional quality of specialty crops grown in controlled environment agriculture systems.The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.Conceptualization – HH, DK, CS. Methodology – HH, CS. Software – HH, CS. Validation – HH, CS. Formal analysis – HH, CS. Investigation – HH, CS. Resources – CS. Data curation – HH. Writing  – HH. Writing (review and editing) – HH, DK, CS. Visualization – HH. Supervision and project administration – CS. Funding acquisition – CS. All authors contributed to the article and approved the submitted version.


Immunoglobulin G4-related disease (IgG4-RD) is a unique immunological disease that can impact multiple organs including a formation of a hepatic inflammatory pseudotumor (IPT). We present a case of a 67-year-old male with a history of chronic viral hepatitis C infection who had an accidental finding on magnetic resonance imaging (MRI) of a liver arterially enhancing lesion. With an extensive work-up, immunohistochemical stains for immunoglobulin G of the liver lesion was performed and showed markedly increased IgG4-positive plasma cells (> 50/HPF), which was consistent with hepatic inflammatory pseudotumor related to IgG4-RD. The patient was treated with prednisone with a complete resolution of the hepatic lesion. The diagnosis of hepatic IPT and IgG4-RD requires a high degree of clinical suspicion and coordination with a multi-disciplinary team, including pathologists. Early tissue acquisition and staining for IgG4 was essential for the early diagnosis and treatment in this case. We also provide a comprehensive summary of published reports of IgG4-RD presenting with IPT. Immunoglobulin G4-related disease (IgG4-RD) is an immune mediated condition that can affect multiple organs and lead to organ failure . The preA 67-year-old male with a history of chronic viral hepatitis C (with a sustained virologic response following treatment with velpatasvir-sofobuvir and ribavirin seven years prior) without advanced hepatic fibrosis presented with a bile duct injury following laparoscopic cholecystectomy for symptomatic acute cholecystitis. His post operative course was complicated by multiple instances in which percutaneous drains placed at the time of surgery were dislodged and during one drain replacement, the tube was passed through the hepatic venous system and pleural space with subsequent bilo-thorax development. Magnetic resonance imaging (MRI) for drain assessment found an enlarging arterially enhancing lesion involving hepatic segment 3, measuring 2 cm, with associated washout and pseudo capsule, concerning for hepatocellular carcinoma (HCC) Figure . His labA core needle biopsy of the liver lesion was performed and showed an inflammatory process composed of abundant lymphoplasmacytic inflammation with focal storiform-type fibrosis. Immunohistochemical stains for Immunoglobulin G (IgG) performed showed markedly increased IgG4 positive plasma cells (> 50/HPF), which was consistent with IgG4-RD. Alpha-fetoprotein collected two months prior was 4 ng/mL (<8.3 ng/mL). Immunological staining of the patient’s gallbladder from his prior cholecystectomy did not demonstrate an elevated IgG4 to IgG plasma cell ratio suggesting IgG4-RD in the gallbladder.The patient was started on a prednisone taper plan as follows: 40 mg for 14 days, then 20 mg for 14 days, and then 10 mg for 14 days. Following the first two-week course of steroid treatment, his laboratory studies were as follows: alkaline phosphatase 125 U/L (40-126 U/L), AST 38 U/L (10-50 U/L), ALT 57 U/L (10-50 U/L), total bilirubin 0.5 mg/dL (<1.2mg/dL), direct bilirubin 0.28 mg/dL (0.0-0.30 mg/dL), INR 1.41 (0.85-1.15), and serum creatinine 2.56 mg/dL (0.67-1.17 mg/dL). After the patient had completed the steroid treatment plan, follow-up imaging was done. The visualized mass-like structure was not visualized on magnetic resonance cholangiopancreatography (MRCP)  are often unable to differentiate concerns for malignancy from IgG4-RD. In the presenting case, there was a high suspicion of HCC because the lesion was exophytic, had enhancement on imaging, and the patient had a history of hepatitis C, although the patient had no evidence of advanced fibrosis. The diagnosis of IgG4-RD can be made clinically using the Japanese Comprehensive Clinical Diagnostic (CCD) criteria for IgG4-RD and histopathology .The patient did not obtain a serum IgG4 level until after steroid treatment and at that time, serum IgG4 levels were found to be within normal limits. A biopsy is essential to make the definitive diagnosis of IgG4-RD. The pathognomonic histology for IgG4-RD includes a dense lymphoplasmacytic infiltrate with a storiform pattern, evidence of obliterative phlebitis, and moderate eosinophilic infiltrate that is positive for IgG4 plasma cells; a diagnosis requires two out of three findings ,6,7. TheA literature search via PubMed using key terms -IgG4, -hepatic, and -pseudotumor found 38 case reports. After excluding cases without access to full text n= 18) and patients of <18 years old (n= 1), 19 case reports remained (Table 8 and patWe incidentally discovered a patient with IgG4-RD with the presentation of hepatic IPT. The diagnosis of hepatic IPT and IgG4-RD requires a high degree of clinical suspicion and coordination with a multi-disciplinary team, including pathologists. The Japanese CCD criteria can be used to determine the probability of the diagnosis. In cases such as this one, serum IgG4 levels may not be drawn prior to treatment. However, it is reassuring to see normal serum IgG4 levels following steroid treatment. Early tissue acquisition and staining for IgG4 was essential for the early diagnosis and treatment in this case. Comparing this patient’s case with previously published case reports of hepatic IPT, the patient’s chronic hepatitis C was found to be unique. The exact mechanism connecting hepatitis C and IgG4-RD is still unknown requiring further study with levels of IgG4 immunoglobulin influencing each disease's progression. Our patient completed steroid treatment and follow-up imaging did not visualize the previously demonstrated mass.