A high-strength concrete and mortar subjected to compressive fatigue loading were comparatively investigated using experimental and computational techniques. The focus of the investigations was on the influence of the coarse aggregate in high-strength concrete. Accordingly, the fatigue behaviour was analysed experimentally using the macroscopic damage indicators strain, stiffness and acoustic emission hits. The results clearly show differences in the fatigue behaviour between the concrete and the mortar, especially at the lower stress level investigated. The basalt coarse aggregate here improves the fatigue behaviour of the concrete. Indication of a negative effect can be seen at the higher stress level. A finite element approach with a gradient-enhanced equivalent strain-based damage model combined with a fatigue model was used for the computational simulation of the fatigue behaviour. The damage model includes a differentiation between tension and compression. The fatigue model follows the assumption of the reduction in the material strength based on the accumulated gradient-enhanced equivalent strains. A random distribution of spherically shaped basalt aggregates following a given particle size distribution curve is used for the simulation of concrete. The comparison of the experimentally and computationally determined strain developments of the concrete and mortar shows very good agreement. The application of concrete with increasingly higher compressive strengths enables the realisation of more slender concrete structures. Compared to massive structures, these slender structures are exposed to fatigue-relevant loads to a higher extent because of their lower ratio of deadweight to non-static loads. Moreover, special structures, such as wind energy plants or machine foundations, are generally exposed to fatigue loading with huge numbers of load cycles. Both the development of concrete types with increasingly higher compressive strengths and the expanded construction of wind energy plants have led to a growth of research activities in the field of the fatigue resistance of concrete in the last few decades. After focusing mainly on the number of cycles to failure, the latest research is especially focused on the concrete fatigue behaviour or rather damage development ,2, whichIt is well-known that high-strength concrete has a denser binder matrix with increased compressive strength and a less pronounced and improved interfacial transition zone. Both properties lead to an improved microstructure. However, the influence of this improved microstructure and the presence of coarse aggregate on the fatigue behaviour under compressive fatigue loading has not yet been understood entirely.Mehmel and Kern  investigThe modelling of concrete, including its complex material and damage behaviour, has reached a highly advanced state for monotonically increasing external loads. In the case of fatigue loading, the cyclic increase in damage, which additionally depends on, for example, the maximum and minimum stress level and the load frequency, has to be comprised by the computational model. Material models, such as a Drucker–Prager–Cap model  or microIn addition to the phenomenological modelling of fatigue, a few damage models were developed especially for fatigue problems . These mThe general challenge in developing and validating computational models is the limited knowledge regarding the important material behaviour patterns and their interpretation on a small length scale leading to the observable macroscopic material behaviour. This particularly concerns those models that can be applied to simulate the complex processes of fatigue damage accumulation in concrete’s microstructure. A close cooperation between researchers in computational mechanics and materials science is essential in this case.A conjoint research project, which is part of the DFG Priority Programme SPP 2020 ‘Cyclic Deterioration of High-Performance Concrete in an Experimental-Virtual Lab’, investigated the compressive fatigue behaviour of high-strength concrete and mortar experimentally and numerically. In this paper, the numbers of cycles to failure and the damage indicators strain, stiffness and AE are analysed comparatively for a high-strength concrete and its corresponding mortar. Furthermore, a new modelling approach for the simulation of the concrete and mortar’s fatigue behaviour is described and the numerical results received are presented comparatively and discussed with the fatigue behaviour determined experimentally.w/c) ratio is 0.35.The experimental investigations were conducted on a high-strength concrete RH1-B, which is the reference concrete composition in the research project  and cm,cubef according to DIN EN 12390-3 [cmE according to DIN EN 12390-13 [The 28-day compressive strength  12390-3  and the 12390-13  were deth = 300 mm and a diameter of d = 150 mm. The respective mean values of three tests each are cm,bf = 326 MPa and m,bE = 99,800 MPa.The compressive strength and the modulus of elasticity of the basalt coarse aggregate were determined using drill cores with a height of h = 180 mm and diameter of d = 60 mm were used in the fatigue tests. The concrete or mortar was filled into PVC formworks in two equal layers and each layer was mechanically compacted using a vibrating table. The PVC formwork of the concrete specimens was removed 7 days after concreting and the cylinders were stored in standard climate conditions (20 °C/65% R.H.) until testing. The treatment of the mortar specimens was different from that of the concrete specimens in order to avoid increased microcracking due to shrinkage. The mortar specimens were also stored in standard climate conditions, but the PVC formwork was removed 14 days after concreting. Subsequently, these specimens were stored wrapped in plastic foil for 14 days and then without foil for at least a further 28 days in standard climate conditions (gentle drying) until testing. The test surfaces of all specimens were plane-parallel ground and polished to achieve a more uniform stress distribution.Cylindrical specimens with a height of minS = 0.05 in all tests, while the maximum stress level was either maxS = 0.85 or 0.70. The test frequency applied was tf = 1.0 Hz in all tests. The compressive fatigue reference strengths of the high-strength concrete and mortar were tested just before conducting the fatigue tests, using five specimens from the same batch having the same geometry as the specimens used in the fatigue tests. The compressive fatigue reference strengths for determining the axial test stresses based on the stress levels defined  were calculated as the mean values cm,reff = 96 MPa for the concrete RH1-B and cm,reff = 97 MPa for the mortar M-B. The age of specimens at fatigue testing was between 56 and 70 days.The fatigue tests were carried out force-controlled using a class 0.5 servo-hydraulic testing machine with a 500 kN actuator (according to ISO 7500-1 ). The fuThe axial deformations were measured continuously in all fatigue tests using three laser distance sensors positioned on the circumference of the specimen at 0°, 120° and 240° . In addiFatigue damage indicators were used to describe the differences in the fatigue behaviour of the concrete and the mortar. The fatigue damage indicators: development of strain, stiffness and AE hits are analysed in this paper. These analyses include all cycles up to the last cycle before failure. This approach was established due to the general occurrence of fatigue failure at different stresses (but mostly in the range of the peak stresses) and the high-grade instable state of the microstructure, which is reached in the last cycle (cf. ).fN/N = 0.20 and 0.80 in this paper for reasons of better comparability. The maximum and minimum peak strains for determining the strain developments were obtained by peak analyses of the sinusoidal strain curves determined by the three laser distance sensors. The three strain developments were subsequently averaged for each specimen. Concerning the mean strain development, a focus was set on the total growth of maximum and minimum strain and the gradient of strain development in phase II (cf. Equation (1)).The gradients of strain, stiffness and cumulated AE hits in phase II were determined between fixed values of related number of cycles The stiffness was determined for each specimen as the secant modulus in the decreasing branch of the hysteresis loop (cf. Equation (2)). The gradient of stiffness development in phase II  was calculated equivalent to Equation (1). In addition, the percentile reduction in stiffness from the first to the last load cycle, with the initial value of stiffness in the first cycle as reference, was analysed.Regarding the analyses of the AE hits, they were summarised from cycle to cycle and displayed as developments of cumulated AE hits. The gradient of cumulated AE hits in phase II  and the total number of AE hits in the complete fatigue process were used as parameters.The mean values of the parameters of the damage indicators, calculated based on the single tests, are given in maxS and the numbers of cycles to failure log fN  is shown in It is worth mentioning that the increase in the specimen’s temperature due to mechanical loading was a maximal 14 K and, thus, relatively low. The correlation between the maximum compressive stress level maxS = 0.85 and significantly higher numbers of cycles to failure at the lower stress level of maxS = 0.70. This indicates, on the one hand, that no influence of the basalt coarse aggregate is recognisable for the higher stress level regarding the numbers of cycles to failure. At the lower stress level, on the other hand, the presence of the coarse aggregate leads to an improved fatigue behaviour.The concrete RH1-B reached similar numbers of cycles to failure to its corresponding mortar M-B at the higher stress level max =S 0.85 and 0.70 are shown comparatively in max =S 0.85, where both materials reached similar mean numbers of cycles to failure . Investigations on other high-strength concrete compositions emphasised the important influence of the mortar’s fatigue behaviour on the strain development of concrete , which smax =S 0.85 and flatter gradients at max =S 0.70  at maxS = 0.70, but the characteristic of the development is different compared to the other developments: a stepwise development after a first initial phase is observable for the concrete. The characteristics of the stepwise development with sections of high AE activity  followed by sections of comparably low AE activity  are not visible in the macroscopic damage indicators strain and stiffness d(κ)This damage model is frequently applied for concrete. Here, α and β are parameters to adjust the shape of the damage function and  measure  was usedemployed ,(8)ε˜. FurtheThis eventually means that the threshold value for roach of , where tmaxS = 0.85 and minimum stress level of minS = 0.05. Since the number of cycles to failure for those stress levels is rather low, it is not necessary to apply computational techniques, such as cycle jump methods, here, which avoid excessive computational effort in case of large numbers of cycles. A standard Newmark method is applied as a time integration method for the following simulations. Twenty time steps are simulated for each cycle. The parameters of the simulation of the mortar and those of the simulation of the concrete are given in In the following, the results of the numerical simulations of the concrete and the mortar are compared with the experimentally determined strain developments at the maximum stress level of d < 2 mm and a homogenised mortar matrix consisting of cement paste and other components. The dimensions of the material sample considered were chosen to be small to keep the simulation times for this initial simulation reasonably low.A 3 mm × 3 mm × 0.3 mm material sample was investigated for the simulation of the mortar cf. a. The domaxS = 0.85 after 340 load cycles, or rather, fN/N = 0.99, i.e., shortly before failure occurs, in The domain was discretised using tetrahedral elements with quadratic shape functions. The boundary conditions were set such that the bottom surface could not move in vertical direction, the back surface could not move to the front and the force-controlled load was applied to a rigid diaphragm on the top surface. The basalt grains were considered to behave linearly elastically without exhibiting damage. This corresponds to our own fatigue tests conducted on the basalt stone. The material parameters of the mortar matrix and the basalt grains are given in The experimentally and computationally determined developments of maximum strain are shown in d ≥ 2 mm, which was experimentally determined for the basalt aggregate used. The grain size distribution used for discretisation is shown in d < 2 mm and other components.A cube-shaped material sample with an edge length of 23 mm was modelled for the simulation of the concrete a. The raThe same as for the mortar, the domain was discretised using tetrahedral elements with quadratic shape functions. Symmetry boundary conditions were applied in all directions. Again, the force-controlled load was applied to a rigid diaphragm on the top surface. The basalt grains were considered to behave linearly elastically again. The material parameters for the concrete simulation are given in maxS = 0.85 after 306 load cycles, or rather, fN/N = 0.99, in The computed gradient-enhanced damage distribution is shown for The experimentally and computationally determined developments of maximum strain are displayed in The results from experimental and numerical investigations on a high-strength concrete and its corresponding mortar subjected to compressive fatigue loading with two stress levels are presented in this paper. The concrete reached similar numbers of cycles to failure as the mortar at the higher stress level but higher numbers of cycles to failure at the lower stress level. Comparing the results for the concrete and mortar, the total growth of strain is smaller and the gradient in phase II is flatter for the concrete. However, the gradient of stiffness of the concrete is steeper at the higher stress level but flatter at the lower stress level, indicating a negative effect of the basalt coarse aggregate on the reduction in stiffness at the higher stress level. Furthermore, larger AE activity was determined for the concrete compared to the mortar and, thus, must be traced back to the presence of coarse aggregate. A stepwise increased AE activity in the concrete at the lower stress level indicates damage processes on a very small scale , which are not visible in the macroscopic damage indicators. The characteristics of the AE signals will be analysed in more detail in further analyses in order to obtain more knowledge about the damage processes.The experimental results presented in this paper demonstrate the existence of differences between the fatigue behaviour of concretes and mortars due to the presence of coarse aggregate. It is assumed that the highly fatigue-resistant coarse aggregate in the concrete relieves the stresses in the fatigue-sensitive mortar at lower stress levels. However, at the higher stress level, indication exists that the coarse aggregate has a negative effect on the concrete’s fatigue behaviour (higher stiffness degradation) compared to that of the mortar. This might be traced back to the inhomogeneous stress distribution induced due to the higher stresses applied and the higher resulting differences in the deformation behaviour of the coarse aggregate basalt and the mortar. Despite this, similar numbers of cycles to failure are reached. However, the influence of coarse aggregate and mortar matrix superimpose. The results in  show thaA newly developed model for the simulation of the strain development under compressive fatigue loading is presented in this paper. The comparison of the experimentally and computationally determined developments of strain reveal very good agreement. The numbers of cycles to failure and the characteristics of the strain developments are very well-depicted. Furthermore, the simulated numbers of cycles to failure result from the simulated fatigue damage development in the mesostructure, whereby the correlation of the slope of the strain development with the number of cycles to failure reached fits the experimental results very well. In contrast to damage models based on the assumption of the Paris law, the newly introduced computational model allows for the simulation of phases I, II and III of the fatigue damage process. A significant and remarkable advantage of the proposed model compared to most classical gradient-enhanced damage approaches is that it can be applied to simulations with monotonically increasing loading and fatigue simulations. The stress redistribution in the mesostructure due to damage can be visualised by applying the fatigue damage model presented. This can contribute to a better understanding of the damage processes within the concrete mesostructure.The present model does not yet contain elastoplastic or viscoplastic material behaviour, which have a significant effect on the fatigue behaviour of concrete. Nevertheless, the results obtained are promising and the material model can be extended by plasticity models suitable for concrete, which will be the subject of future collaborative work. In addition to that, efficient computational techniques avoiding excessive computational effort can be applied for the simulation of large numbers of cycles at lower stress levels in the future.


Aggregates derived from waste, due to the growing awareness of global warming, are more and more often used in the concrete production process. This way, their disposal not only reduces the pollution of the Earth but also lowers the consumption of natural aggregates, which are limited. One of the new “eco” aggregates may be a ferronickel slag waste (FNSW), which was generated in post-war metallurgical processes and stored in Szklary . In order to determine the possibility of using ferronickel slag waste aggregate (FNSWA) in the concrete production process, new concrete mixtures were designed and tested. Physical properties , mechanical properties , and thermal properties  were assessed for all new laboratory recipes. Moreover, the modulus of elasticity and Poisson’s ratio were determined. This study includes five different contents of FNSWA in the amount of 5%, 10%, 15%, 20%, and 25% of the mass of natural aggregate as its partial substitute. The final results were compared to the base sample (BS) containing 100% natural aggregate, which was granite. The war period was particularly severe for Poland. A significant number of the country’s population died, defending their homeland, some lands were taken away, and the losses in the infrastructure were difficult to accurately quantify. It is estimated that the war cost that one resident had to pay was around USD 626 . DespiteThe post-war development of the polish industry has left its mark on the environment by leaving soil and groundwater contamination, and a large amount of waste that remains to this day ,6. This Waste and by-products from other industry branches can be re-used by the construction industry as a component of concrete and mortar ,13,14,153 and substitution in range from 20% to 60% they achieved an increase in concrete mixture workability and a decrease in water absorption of hardened samples. Furthermore, concretes containing 20%, 40%, and 60% showed an increase by 1%, 34%, and 31% compressive strength compared to the base mix (37 MPa), and an increase by about 2%, 15%, and 8% split tensile strength compared to the base mix (4.3 MPa), respectively. The same trend after replacing coarse aggregate with ferronickel was reported by Sun et al. [The possibility of ferronickel slag waste utilization in concrete has been studied during recent years by Saha et al. ,25,26,27n et al.  and Qi en et al. , ferroniThis study aims to contribute to this growing area of research by exploring the potential usage of FNSWA mined in Szklary  as a replacement of natural aggregate in concrete. The problem of FNSW in Lower Silesia in Poland is very serious, so far, however, no possible method of utilization of this waste has been efficiently introduced to the Polish industry. To do so, psychical, mechanical, and thermal properties on new concretes were tested. Findings presented in this study make an important contribution to the effective utilization of ferronickel slag waste accumulated in Szklary  and contribute to the environment harmed by ferronickel slag waste stored there. As it has a different mineral composition proportion compared to the ones presented in current studies it may also show different results of concrete properties, especially its mechanical strength. Moreover, such a replacement is consistent with the principle of sustainable development and the circular economy.U = 7.2 and CC = 1.1) suggests that aggregate is well compacted [ompacted  and, as ompacted  standardw/c at 0.44, the chemical admixture was used. It was a low-alkaline liquid, free of chlorine, and based on an aqueous solution of modified polycarboxylic ethers (melamine and silanes/siloxanes), which helped reduce the accumulated water on the surface of concrete after compaction, as well [In order to increase the workability of all mixtures, but at the same time maintain the water-cement ratio  as well . The cheAs a partial substitute to natural granite aggregate, ferronickel slag waste was used . FNSW wa3. Compared to cement, its chemical composition is similar due to the fact that it contains a significant part of the compounds present in the binder. The FNSWA sieve curve is given in Six different types of mortar mixtures were produced, see After mixing dry components for 1 min, the liquid components were added to the concrete mixture, and blended together for 4 min. Next, fresh concrete was poured into molds and compacted on a vibrating table. All of the samples were manufactured in 21 °C temperature and 50% humidity inside a laboratory and stored in water according to EN 12390-2:2019-07 . After 2From each mix, the following samples were produced: Ten cubes with dimensions of 150 × 150 × 150 mm, five cuboids with dimensions of 40 × 40 × 160 mm, five rollers with a base diameter of 150 mm and a height of 300 mm, and one tile with dimensions of 30 × 30 × 6 mm. In total, 60 cubic samples, 30 cuboid samples, 30 cylinders, and six tiles were made to conduct this study.The slump cone test was carried out according to EN 12350-2:2019-07 , when thThe density of concrete samples, was determined according to EN 12390-7:2019-08  on 150 ×All of the specified above tests were carried out after 28 days of the curing process. Each of them was performed on five samples of every mix and the values presented are the average values .The air content presented in As presented in 3 (BM) and 2378 ± 3 kg/m3 (25FNSW), and, after analyzing them, an overall trend can be noted as: The higher the FNSWA amount, the higher the density of concrete, see 3 after a 10% substitution. Further modifications also showed decreased values—2310 and 2300 kg/m3 for 15% and 30% replacement of cement, respectively. This may be connected to a higher density of cement powder compared to ferronickel slag.The density of concrete samples is presented in 3). The same phenomena was reported by Qi et al. [3 with its addition equal to 20%, 40%, and 60%. They reported similar values of compressive strength (52.15 MPa) for samples containing 20% of ferronickel slag compared to 20FNSW samples (56 ± 1 MPa). Moreover, Sun et al. [The results of compressive strength for samples with different contents of FNSWA are presented in i et al.  as they i et al. . The autn et al.  used two3) was not significant. However, a further increase in FNSWA used in concrete resulted in a visible increase in the split tensile strength, what also was reported by Nuruzzaman et al. [n et al. . Their Fn et al.  tested Fn et al. , however2R coefficient equal to 0.9, means a good fit. This trend was also reported by Saha et al. [a et al. , as wella et al.  as they The modulus of elasticity was slightly influenced by the aggregate substitution done with FNSWA. Results given in On the other hand, the results of the Poisson’s ratio, presented in The obtained results of the thermal conductivity test ranged from 1.53 to 1.88 W/mK . The conThe aim of this study was to evaluate the possibility of using the ferronickel slag waste aggregate stored in dumps in Szklary  as an aggregate substitute in concrete production. To do so, tests on new laboratory concrete mixtures were carried out, from which final key conclusions can be made:The highest air content was reported for 25FNSW samples (3.6%);3) was found for concrete with 25% FNSWA and the lowest density (2187 kg/m3) for plain concrete;The density of hardened concretes were proportional to the amount of FNSWA used. The density increased with the increasing FNSWA and the highest density ;The substitution of natural aggregate done with FNSWA did not affect consistency, the pH value, and Poisson’s ratio of concrete.This research presents a solution to air, soil, and groundwater pollution caused by the remains of post-war mining activities in Szklary . The set goal of this case study, which was to determine the physical, mechanical, and thermal properties of concretes containing FSWA, was successfully achieved. All of the new concretes showed increased strength parameters, crucial in building materials, which can indicate a great application capacity in the current construction industry.


Immunoglobin G4—related disease (IgG4‐RD) is a chronic fibro‐inflammatory condition that presents as a single or multiple tumefactive lesions affecting virtually any organ system. Here we report a case of recurrent sinonasal IgG4‐RD and review the literature of this evolving entity. It was first described in 2001 by Hamano et al.While first described in the pancreas, manifestations of the disease have been described throughout the body, including the lacrimal glands, submandibular glands (Kuttner tumor), orbit, lymph nodes, thyroid, biliary tract, liver, kidney, retroperitoneum, lungs and even aorta. Mulholland et al.2A comprehensive literature review using PubMed and Web of Science was performed through February 2021 following Preferred Reporting Items for Systematic Reviews and Meta‐Analyses (PRISMA) guidelines. Articles related to IgG4‐related disease with sinonasal involvement were identified using the search terms “IgG4‐related disease,” “sinonasal IgG4,” and “sinus IgG4.” Upon removing duplicates, titles and abstracts were screened for relevant articles. English, full‐text case reports and series were included. Non‐English, abstract‐only text, and review articles were excluded. Studies that did not meet histopathological diagnostic criteria for IgG4‐related disease as described by Deshpande et al.3Annals of Allergy, Asthma, and Immunology in 2013, which this manuscript will briefly recount. It is the goal of this paper to present his disease course following Rituximab infusion, as well as the long‐term follow‐up between 2013 and 2021. This patient's disease initially manifested with multiple systemic features, including pulmonary emboli, xerostomia, and intermittent double vision; however, the early stage of disease is not the focus of this paper and is, therefore not extensively discussed.This is the case of a 72‐year‐old male patient whose disease course began with the development of a spontaneous cerebrospinal fluid (CSF) leak in 1999. His early clinical course, from the onset of symptoms up until 2012, was described by Hu et. al.In 1999, at the age of 50 years, the patient presented with CSF rhinorrhea and was incidentally noted to have left ethmoid sinusitis on computed tomography (CT). He underwent a craniotomy for repair, and the surgeon noted that that the dura had a 2 mm defect in the area of the left cribriform plate. The area of infection in the left ethmoid was not addressed. His repair was completed without complication and he remained asymptomatic for over a decade.He presented to another otolaryngologist in 2012 following a 12‐month history of recurrent acute sinusitis. Imaging at that time, including CT and magnetic resonance imaging (MRI) revealed opacification of the left‐sided paranasal sinuses, hyperostotic bone, and a contrast‐enhancing lesion of the left ethmoid cavity that was concerning for malignancy. Endoscopic sinus surgery was performed shortly thereafter, revealing diffuse mucosal inflammation without evidence of a discrete mass lesion. Multiple biopsy specimens were sent intraoperatively. The final pathology revealed a lymphoplasmacytic infiltrate with areas of fibrosis in a storiform pattern, as well as plasma cells that stained positive for IgG4. His IgG4/IgG ratio was >80% in the ethmoid specimen, >40% in tissue from the maxillary sinus, and serum IgG4 was within normal limits . He was initially diagnosed with inflammatory pseudotumor; however, the report was appended several weeks later, and the diagnosis of IgG4‐RD was subsequently made.Shortly after diagnosis, he was referred to an IgG4‐RD specialist in Boston, MA and underwent two consecutive Rituximab infusions. One month after the infusions, his IgG4 level was reduced to 55 mg/dl. The patient noted symptomatic relief, specifically a reduction in sinus pressure and pain, and in‐office nasal endoscopy confirmed a marked improvement in the degree mucosal inflammation. He remained asymptomatic for over a year but his symptoms returned, once again manifesting with left‐sided sinus pressure, pain, and purulent rhinorrhea.Conservative treatment with Budesonide irrigation and culture‐directed antibiotics failed to adequately manage his symptoms. A post‐treatment CT scan revealed opacification of residual left‐sided ethmoid air cells, hyperostotic bone and mucosal thickening within the left maxillary sinus. He underwent revision endoscopic sinus surgery, including left maxillary antrostomy, total ethmoidectomy, and frontal sinus exploration, which was complicated by a CSF leak from the left lateral lamella of the cribiform plate. This was repaired with a free mucosal graft from the left middle turbinate. His surgical pathology showed an IgG4/IgG ratio that was >70%.Over the following year, his chronic rhinosinusitis (CRS) symptoms were successfully managed with nasal saline irrigations and intermittent use of oral steroids and culture‐directed antibiotics for disease exacerbations. The frequency of infections and the number of antibiotics prescribed increased over the following year, with worsening polypoid edema in the left maxillary sinus on follow‐up endoscopy. A third Rituximab infusion was performed in 2016, and at that time his IgG4 level was 45 mg/dl. Unlike his prior infusions, his symptoms did not improve as dramatically, and he had four additional sinus infections requiring antibiotics over the ensuing 12 months. A left maxillary mega‐antrostomy was performed in October 2016, and again the pathologic evaluation of the tissue supported the diagnosis of IgG4‐RD. Following surgery, he was again started on Budesonide irrigations which he continued daily for over a year, after which he transitioned to irrigations with buffered saline alone. Over the following years, he has remained mostly asymptomatic and only required intermittent culture‐directed antibiotics for sinusitis exacerbations. At his most recent clinic appointment in December of 2020, his SinoNasal Outcome Test‐22 (SNOT‐22) score was 3, and he had not experienced a sinus infection for over a year.4IgG4‐RD is a rare fibro‐inflammatory condition characterized by tumefactive lesions that can arise in multiple different sites. First described in 2001 by Hamano et al.,4.1While it is common for IgG4‐RD to involve multiple different organ systems at presentation, it seems that sinonasal IgG4‐RD is often limited to local disease or only head and neck involvement. Of the 31 cases in this review, 14 (45%) had extra‐sinonasal involvement, most of which involved the salivary glands or orbit. Only 2 of these cases involved organs outside of the head and neck, and the present case is the third. The most common sinonasal structures involved were the maxillary sinus (61%), followed by the ethmoid sinus (29%), nasal cavity/septum (26%), sphenoid sinus (19%), and two cases involving the frontal sinus (6%). The sinonasal locations of involvement and other organs involved are shown in Table 4.2IgG4‐RD has been shown to be most prevalent in the older male population, with a reported male‐to‐female ratio of 1.6–4:1.4.3Common presenting symptoms of sinonasal IgG4‐RD from this article's review include nasal obstruction/congestion (48%), facial swelling (26%), headache (19%), and epistaxis or blood‐tinged rhinorrhea (16%). While only five other cases (16%) presented a multiple‐year history of chronic rhinosinusitis like this patient, IgG4‐RD might be an important diagnostic consideration in patients with intractable CRS, especially when imaging is suggestive of the disease. Additionally, a few other cases described recurrent facial pain, congestion, and nasal discharge that were consistent with CRS in whom this diagnosis was not made. These presenting symptoms are, therefore, important to consider when making the diagnosis of sinonasal IgG4‐RD. Presenting symptoms are listed in Table For the patient in the present case, sinonasal endoscopy was performed at each of the clinic appointments during the nine years he was managed at this institution. The modified Lund‐Kennedy (mLK) endoscopic scoring system is a standardized method of quantifying the visual appearance of the sinuses on nasal endoscopy.4.4The majority of cases demonstrated thickening, attenuation, or enhancement of the soft tissue in the sinuses with or without a discreet mass. However, Ueno et al.4.5Definitive international pathology consensus guidelines for diagnosis were formally described in 2012 by Deshpande et al.N = 28). All of the cases that reported a value of IgG4+ plasma cells/HPF >10 (19 cases), with most values >30 (79%). Several others reported “diffuse” or “many” IgG4+ plasma cells instead of numeric values. All of the cases that reported IgG4+ cells/total IgG‐containing cells ratio demonstrated a ratio >40% (16 cases). Laboratory and histologic summary from the present review is detailed in Table Elevated serum levels of IgG4 are usually reported in 70%–80% of all patients with IgG4‐RD,4.6There are many approaches to treatment of IgG4‐RD which usually involve some combination of surgical resection of affected tissues, systemic glucocorticoids, steroid‐sparing immunosuppressive drugs and biological agents. Prednisone monotherapy at a dose of 0.6 mg/kg/day and tapered over the period of 3–6 months is currently considered the first‐line therapy.In a recent study, the recurrence rate for IgG4‐RD was reported to be 46% after initial treatment with steroids.5While a greater sample size is required to draw definitive conclusions, the findings presented here, which include the most comprehensive review of literature to date, suggest that the general otolaryngologist or rhinologist should have a high index of suspicion for this disease process when considering patients who present with new‐onset symptoms of chronic sinusitis, particularly middle‐aged adults without a longstanding history of sinonasal complaints or patients with refractory disease despite appropriate surgical intervention. When sinonasal IgG4‐RD is considered, the authors of this article recommend diagnostic workup that includes CT sinuses without contrast, serum IgG4, and biopsy of the involved sinus tissue, if feasible. Although the utility of positron emission tomography‐computed tomography (PET‐CT) in the diagnosis of IgG4‐RD has been supported, sinonasal IgG4‐RD is often limited to the head and neck, and therefore, it should not be used for the initial diagnostic workup. PET‐CT can be considered once the diagnosis has been confirmed in order to identify other organ system involvement or to monitor treatment response.Additionally, these findings suggest that steroid monotherapy is usually sufficient to prevent recurrence in sinonasal IgG4‐RD. Although surgery may be indicated to improve symptoms, caution may be warranted, since it does not seem to reduce the likelihood of recurrence. The findings of this case and literature review also confirm that rituximab is an important consideration with recurrent disease after steroid monotherapy. A summary of diagnostic workup recommendations by the authors of this report can be found in Table This research received no specific grant from any funding agency in the public, commercial or not‐for‐profit sectors. There are no competing interests with regard to this project.Caleb P. Wilson, Ben Brownlee, Kibwei A. McKinney, and Edward El Rassi each contributed meaningfully to data collection, manuscript writing, and final review.Patient consent was obtained for inclusion in this case report. No identifying details have been disclosed.


Concrete infrastructure requires continuous monitoring to ensure any new damage or repair failures are detected promptly. A cost-effective combination of monitoring and maintenance would be highly beneficial in the rehabilitation of existing infrastructure. Alkali-activated materials have been used as concrete repairs and as sensing elements for temperature, moisture, and chlorides. However, damage detection using self-sensing repairs has yet to be demonstrated, and commercial interrogation solutions are expensive. Here, we present the design of a low-cost tomographic impedance interrogator, denoted the “ConcrEITS”, capable of crack detection and location in concrete using conductive repair patches. Results show that for pure material blocks ConcrEITS is capable of measuring 4-probe impedance with a root mean square error of ±5.4% when compared to a commercially available device. For tomographic measurements, ConcrEITS is able to detect and locate cracks in patches adhered to small concrete beam samples undergoing 4-point bending. In all six samples tested, crack locations were clearly identified by the contour images gained from tomographic reconstruction. Overall, this system shows promise as a cost-effective combined solution for monitoring and maintenance of concrete infrastructure. We believe further up-scaled testing should follow this research before implementing the technology in a field trial. Concrete degradation is an ever-growing global challenge as more structures reach the end of their design life . Asset mresistance tomography (ERT) has been demonstrated for crack detection in concrete via an electrically conductive paint  [The major challenge facing concrete monitoring applications is that existing EITS interrogators tend to be expensive ($15k USD), plug-in bench systems which are optimised for chemical analyses and medical imaging. There is a clear need for low-power, low-cost and portable EITS interrogators optimised for wireless concrete structural health monitoring if this technology is to gain wider industry application. Low-power, portable devices for corrosion and electrochemical testing of concrete has been demonstrated and examples have been summarised by Segura et al. , includiutlined) . No examRecent work by the present authors has outlined the use of alkali-activated material (AAM) as a self-sensing non-structural concrete repair. We have demonstrated that changes in concrete and AAM repair material moisture , temperaIn this paper, we present ‘ConcrEITS’: a new low-cost EITS interrogator which can provided continuous and distributed measurements of concrete specimens via electrically conductive coatings, such as AAM repairs. The system is capable of both single 4-probe impedance and 16-probe tomographic impedance measurements of AAM patches at various AC driving frequencies. Here, we benchmark ConcrEITS against a commercial 4-probe impedance analyser before validating its ability to detect and locate temperature changes and concrete cracking in small lab-scale specimens. ConcrEITS is in the proof-of-concept stage, and results are demonstrated at small scale. Future work will look to demonstrate ConcrEITS at full scale.Alkali-activated materials (AAMs) are a class of curable cementitious materials produced by mixing an alkaline activator solution (such as sodium hydroxide and sodium silicate) with a precursor rich in silicon and aluminium (such as metakaolin). For more information on the fabrication of AAMs, their deployment and curing methods, and their use as repairs, see in ,18. InitAfter curing, AAMs act as electrolytic conductors due to the presence of mobile sodium ions in their matrix . Their ichloride . AlternaThe large number of variables involved in AAM mixing can cause contradicting conclusions from similar studies. Simple factors such as mixing technique and duration or even location of sourced alumnisilicate can change the mechanical properties of the final product ,20. It iSolid:liquid ratioNaAdditivesIn this work, the focus is on acquiring a pourable and strong surface coating that can adhere well to a concrete specimen until cracking, with sufficient conductivity for sensing. The three main factors in a mix design are as follows:Requires a higher liquid content which increases conductivity .Has more consistent particle sizes than fly-ash .Is a natural resource compared to fly-ash  and BFS (by-product of iron/steel smelting).More suitable as a repair than BFS .Metakaolin was chosen over other alumnisilicates ) for four reasons:However, Zhang et al.  suggest  optimal ). A Na2Suctivity ,26. For uctivity , with 50uctivity . Finallyuctivity .Every ingredient, their mass contribution and an example mass for the mix design used in this work is given in Small 30 mm × 30 mm × 25 mm prism samples of this mix design were crushed in a compression machine. These experiments will provide a general indication of the compressive strength of the material. BS EN 12190:1999 requires 40 mm cubes to be tested, but this could not be done with the equipment available. Should this material be used in a real world application, a more extensive mechanical analysis should be performed. From a total of 13 prisms, an average compressive strength of 26 MPa was gained, with a standard deviation of 6 MPa. This meets BS EN 1504:1999 for non-structural repair of concrete (≥15 MPa).Prior to the AAM being applied, the concrete surface was wire brushed to improve adhesion. The AAM repairs were then applied manually within a temporary mould attached to the concrete surface. Stainless steel electrodes (plates or bolts) were inserted to allow for later electrical coupling to the impedance analyser/ConcrEITS instrument. Samples were then cured at room temperature in sealed containers for 28 days. This produced concrete prism and cube samples b,c with Low-cost electrical impedance measuring devices for concrete have gained some interest in recent years: Corva et al.  developeThe electrical impedance of a specimen can be monitored via 2-, 3-, or 4-probe AC excitation . For an extensive overview of these methods, along with examples of when they should be deployed, see . In thisIn its ideal case, the VDP method consists of small “point” electrodes placed exactly in the corners of a thin, cloverleaf shaped cell. However, these ideal conditions are rarely even approximately met in real applications: electrodes have a finite area, cannot be placed exactly in the corners, and AAM patches need to have a suitable shape and thickness to be able to function as a repair. Weiss  states tEquation  can be uFor AAMs, the electrical impedance consists of a resistive . In EIS, impedance measurements are carried out over a range of excitation frequencies, To carry out these tasks, and keep costs low, an ATXMEGA128A4U  micro-coThe measured voltage, The minimum conversion times of ≈7 Data logging is done via a serial interface UART-to-USB device, or using a UART-to-bluetooth module when wireless communication is required. The device is compatible with battery operation, as it is low power, drawing (≈95 mW), and uses a 3.4 V DC supply.The total combined cost of components and manufacturing of a single ConcrEITS PCB is $50 USD at low fabrication volumes.ConcrEITS was benchmarked against a commercial interrogator (which costs $16k USD). Benchmarking was conducted on pure AAM block samples, as shown in Results are shown in For a closer comparison, With the successful demonstration of ConcrEITS for 4-probe EIS, the next stage was to look to the requirements for distributed impedance mapping via electrical impedance tomography (EIT).x is the applying pair of electrodes, and y is the measuring pair. EITS is an extension of EIT, in which the frequencies are also altered during the measurement.EIT can be considered as the implementation of the impedance measurement outlined in Historically, when discussing EIT, the electrical conductivity distribution, The objective of difference imaging in EIT is to produce a reconstructed colour contour image to analyse the change in conductivity (or impedance) distributions over time, relative to some baseline measurement. In contrast to absolute imaging, difference imaging is not sensitive to errors, such as electrode misplacements, misshapen bodies, and inhomogeneous materials. All of which are common in practical civil engineering applications. These benefits compensate somewhat for the reduced level of accuracy and spatial resolution compared to absolute imaging.An in depth discussion of impedance mapping is provided in . BrieflyV is a vector of observed electrode potentials, V, and n is some measurement noise.The forward problem is the prediction of the boundary voltages of a body based on its modelled conductivity distribution. It can be stated in simplified terms asa in the body, At a deeper level, the equation which is being solved is the nonlinear Laplace equation:To gain unique solutions to Equation , boundarThe forward problem is then to solve the CEM with Equation  over theThe maturity of EIT in the medical field means that there are already available methods to solve the forward problem using open-source software. One example is the Electrical Impedance Tomography and Diffuse Optical Tomography Reconstruction Software (or EIDORS), which is used in this work.The purpose of the inverse problem is to utilise the forward model to estimate the conductivity change, J is the Jacobian matrix of mapped conductivities to voltages from the forward model. From this, the objective is now to find In the difference imaging method, a linearisation model is used to approximate the difference using Equation  as(7)δVThe inverse problem is ill-posed, because it has non-unique solutions. In other words, multiple conductivity distributions could lead to identical boundary voltages. The regularisation term s smooth . TikhonoThe only additional hardware requirement to realise tomographic imaging is to perform impedance measurements over multiple pins via multiplexing. Due to the small size of the samples in this work, 16 pins were assumed to provide enough spatial resolution without overcomplicating the circuit. For larger AAM repairs samples, more electrodes may be required. From In the results presented in this paper, the firmware was updated to serially measure every combination of electrodes as previously illustrated in The output of EIDORS consists of a reconstructed contour image of the conductivity change between two states separated by time. For convenience, contour images are normalised and set to the same magnitude limits, allowing direct comparison between samples. Results are described in reference to change in conductivity, Initial testing of ConcrEITS for EIT involved detection and location of temperature changes over a 100 mm × 100 mm patch. This test was chosen as it is non-destructive and could be repeated indefinitely. Our previous work  has showResults from a representative test are shown in The tomographic reconstruction shows that the resulting thermal variations are detectable from the electrical measurements. However, it is clear that discretely located temperature changes are dispersed, due to the low thermal conductivity of the AAM and the high thermal inertia of the concrete substrate. This may be why the system is unable to distinguish between two heated dishes during test T3.Although interesting, these results show that despite being reversible, temperature mapping has its limitations as a testing and validation procedure for this system. In future, if temperature becomes the intended measurand, a thermocouple will be embedded within the AAM during testing to better understand heat dispersion in the AAM.To test damage detection and location using ConcrEITS, small-scale concrete beam bending experiments were carried out, as shown in For example, sample SB1 cracked between electrodes 11 and 12 which then propagated upwards to between electrodes 4 and 5. This is correctly measured from the tomographic reconstruction image. In cases where multiple cracks occur, such as SB5 which cracks between electrodes 10 and 11, 14 and 15, then 3 and 4: these are all observed in the tomographic reconstruction, with black contours appearing in these locations representing a decrease in conductivity. However, it is clear that accurate quantification of crack shapes and widths cannot be ascertained from these reconstructions.We believe there are two main reasons for this. First, difference imaging is inherently less accurate than absolute imaging , therefoNevertheless, ConcrEITS has demonstrated that is able to generally detect and locate cracks, and provide some measure of severity. Furthermore, the system provided no spurious results; there were no false positives or negatives. That is, no cracks were undetected and there were no large decreases in conductivity at locations without cracks. Overall, these results show that the low-cost, low-power ConcrEITS shows promise as a crack detection system for AAM repairs and potentially other self-sensing coatings which encode measurands as a conductivity change.Results in this paper represent a validation of ConcrEITS as a low-cost distributed crack detection system using AAM self-sensing repairs. This section will first analyse the results before discussing various parts of the research and how they could be improved for the future.Initial testing attempted to measure distributed temperature changes in a 100 mm × 100 mm patch. This sought a simple, fast, and repeatable experiment to validate the interrogator measurements. However, it is clear from the thermal variation images  beams with manually deployed AAM patches over a single surface were tested. Results show that distributed crack measurements over time are possible with ConcrEITS, although locations are general and exact crack widths, shapes and lengths are indistinguishable. Nevertheless, these results show promise for the use of ConcrEITS and AAM on large area concrete as a distributed crack detection system.From Research in this paper demonstrates the capability of ConcrEITS to detect and locate cracks in small scale samples. Identifying the location of a crack in such a small area has little to no use in an industrial context. The final objective of ConcrEITS is to perform distributed crack detection over a large area covered with an AAM. Future work will look to upscale the research in this paper to larger areas, working towards a site deployment. This will also require benchmarking against the commercial interrogator for larger samples.In In terms of resolution, the MCU uses 12-bit ADC and 12-bit DAC, which for a In this paper, we have presented ConcrEITS: a low-cost ($60 USD) interrogator for tomographic and spectroscopic impedance mapping of concretes coated with conductive coatings. The system was demonstrated for an alkali-activated material-based repair. ConcrEITS was able to measure impedance to ±


The mechanical properties of the static and dynamic compression of concrete eroded by a 15% sodium sulfate solution were explored with a 70-mm-diameter true triaxial static-dynamic comprehensive loading test system, and an analysis of the weakening mechanisms for the degree of macroscopic damage and microscopic surface changes of eroded concrete were conducted in combination with damage testing based on relevant acoustic characteristics and SEM scanning. The experience obtained in this paper is used to analyze and solve the problem that the bearing capacity of concrete buildings is weakened due to the decrease in durability under the special conditions of sulfate erosion. The results showed that, in a short time, the properties of concrete corroded by sulfate solution were improved to a certain extent due to continuous hydration. When the corrosion time was prolonged, the internal concrete structure was destroyed after it was eroded by sulfate, and its dynamic and static strength, deformability, and energy absorption were reduced to differing degrees, thus greatly inhibiting the overall mechanical performance of concrete; the dynamic compressive strength changed with strain that exhibited a significant strain rate effect; and, under the influence of sulfate erosion and hydration, the longitudinal wave velocity increased first and then decreased. The longitudinal wave velocity was slower than that of concrete under normal environment and distilled water immersion condition. SEM and acoustic wave analysis indicated that the internal concrete structure was destroyed after it was eroded by sulfate, and its dynamic and static strength, deformability, and energy absorption were reduced to differing degrees, thus greatly inhibiting the overall mechanical performance of concrete. Concrete is universally used in both industrial and civil construction as a building material due to its low cost, convenience, excellent compressive performance, and easy access to components. Under normal service conditions, concrete possesses good dynamic properties; its dynamic compressive strength ,2, deforThe erosion of concrete by sulfate is mainly reflected in its destruction of the calcium silicate hydrate gel, which leads to the disruption of the original internal structural balance of concrete. Sulfate erosion usually occurs in the form of swelling and cracks in concrete , when afBy now, great progresses have been made while researching the erosion effect of sulfate on concrete. In their study, Guo et al. ,15 focusSarkar et al. ,19,20,21Many scholars have carried out a lot of research and analyzed sulfate erosion of concrete from many angles, including the establishment of models for different types of modified concrete and other types of cementing materials. In fact, however, most of the concrete subjected to sulfate attack is plain concrete, which has been extensively studied under the condition of erosion, but many remain static. Under actual working conditions, some concrete buildings not only bear static loads, but also dynamic mechanical properties of eroded concrete should be considered due to the influence of earthquake, war and other factors. In terms of experimental microscopic and macroscopic observation methods, it is impossible to comprehensively study the mechanism of sulfate erosion of concrete by fine observation of concrete damage points or comprehensive study of concrete damage as a whole. Therefore, dynamic and static mechanical properties are analyzed at the same time, and SEM and ultrasonic detection technology are used at the same time, so as to comprehensively meet the problems of applying different loads and analyzing different layers of sulfate corroded concrete. Sulfate corrosion of concrete for civil construction and national defense construction to provide the theoretical support and scientific basis, and to solve concrete buildings in coastal areas and saline soil areas, led to a short use period because of its special service environment, durability, and cause economic loss. By reducing the erosion of salt for concrete and improving the service time of concrete, it avoids the interference to the normal work of sulfate corroded concrete, reduces the waste of concrete caused by repeated construction of damaged parts due to erosion, and makes a small contribution to the sustainable development and reduction in carbon dioxide emissions to promote green and low-carbon construction mode.In this study, ordinary concrete cube specimens were prepared and corroded by sulfate for 0 d, 30 d, 60 d, 90 d, and 120 d, respectively; a 70-mm-diameter true triaxial static-dynamic comprehensive loading test system was utilized for mechanical testing under static and dynamic compression to obtain the dynamic stress–strain relationship for each test piece at different strain rates; and a comprehensive analysis on the damage points was conducted macroscopically by analyzing the static compressive strength, dynamic compressive strength, and strain rate effect, as well as exploring the dynamic and static mechanical properties and acoustic damage law. In addition, the corresponding damage points were scanned by SEM, so that the dynamic and static mechanical properties of concrete under sulfate attack and relevant mechanisms of action from both macroscopic and microscopic aspects may be obtained.2/kg, density: 3.15 g/cm3, fineness: (80 μm sieving residue) 7.6%; fine aggregate: sand from the Ba River, Xi’an, China, fineness modulus: 2.6, apparent density: 2.44 g/cm3, bulk density: 1.77 g/cm3; coarse aggregate: crushed limestone, 15% of particle size 5–10 mm and 85% of particle size 10–20 mm, volume weight: 2700 kg/m3. Cement content is 495 kg/m3, coarse aggregate content is 1008 kg/m3, fine aggregate content is kg/m3, and water consumption is 180 kg/m3. A “sand enclosed cement” method was adopted for the concrete test pieces in this test. After the concrete was mixed, its surface was covered with a film to cure it and prevent water evaporation. A cube specimen with a side length of 70 mm was prepared at room temperature (80 ± 5% in case humidity and 20 ± 3 degrees in case of temperature). After 24 h of curing, the molds were removed, and the test pieces were transferred to the standard curing room for 28 d of curing. Then, the test pieces were taken out for the water to grind the sides with a stone grinding machine, so that the surfaces of the test pieces were flat and smooth. For the Na2SO4 adopted in this test, at room temperature (20 ± 3 °C), the solubility in 100 g water is about 19.5 g and the mass fraction is about 16.3%. Therefore, the erosion solution used in this test was a Na2SO4 solution with a mass fraction of 15%, and the solution was replaced every seven days, so that the mass fraction of the solution was maintained at 15% during erosion , Rε (t), and Tε (t), the incidence, reflection, and transmission strains in the bar, respectively. During testing, a dispersion effect may occur while propagating a stress pulse, and, furthermore, the test cannot guarantee that the test pieces have enough time to achieve a homogeneous state of stress. In this study, the loading waveform was changed by incident wave shaping technology, and the rectangular wave generated during the experiment was transformed to create a semi-sine wave that was easy to observe and utilize, thus reducing the test waveform disorder caused by the dispersion effect, and improving the overshot and high frequency oscillation in the bar impact process. During this test, a brass pulse shaper was used to shape the incident wave. This pulse shaper had a thickness of 1 mm and a diameter of 27 mm.To explore the damage law on concrete eroded by sodium sulfate, ultrasonic pulse technology was utilized for a relevant analysis on the concrete. After the sulfate attack, the concrete underwent a series of complex physical and chemical changes, with erosion products in it and on its surface, as well developing damage defects, such as pores and micro-cracks, and the overall performance of concrete was degraded due to erosion. When the ultrasonic waves passed through the concrete, longitudinal waves traveled much more quickly than shear and surface waves. Non-metallic ultrasonic analyzer is mainly composed of two parts. One part is ultrasonic transmitter, which is mainly composed of a DC boost system, a high-voltage pulse transmission system, and a transmission transducer. The other part is the ultrasonic receiving device, which is mainly composed of data acquisition system, signal amplification system, and receiving transducer. The transducer for an ultrasonic analyzer can emit various waves. Because the longitudinal wave travels most quickly, the receiving transducer receives it first, known as the head wave, of which the propagation velocity will be affected by the internal structure, pore distribution, and crack development of concrete. Therefore, the ultrasonic test of concrete corroded by sulfate mainly explores the propagation law of longitudinal wave in concrete. In this test, a KON-NM-4A nonmetallic ultrasonic analyzer manufactured by Beijing Kangkerai Engineering Testing Technology Co., Ltd., Beijing, China. was adopted for detecting acoustic damage in concrete. Before the test, in order to prevent the residual moisture on the surface of the concrete specimen from adversely affecting the test, the concrete specimen was put in a static position until there was no moisture on its surface. The treated specimen between the ultrasonic transmitting device and receiving device was fixed, the face of the concrete was fixed, preparation was completed, and ultrasonic was launched. There was then a wait for the ultrasonic wave velocity stability after the test results were recorded, and, after the record, the location of the ultrasound transmitting device and receiving device was swapped. The above steps were repeated and the ultrasonic wave velocity measurement was recorded.The SEM test was conducted using Nova NanoSEM230 field emission scanning electron microscope produced by FEI Company . According to the research content and the requirements of the test instrument, the concrete sample used for observation was the concrete cement mortar part inside the square specimen damaged after static compression test. The test sample in alcohol concentration for 48 hours soaked in 70% alcohol solution was observed, and soaking by alcohol solution was performed to remove surface impurities affect the follow-up observations to improve the electrical conductivity of the sample surface, and to facilitate follow-up observations, using Leica in Germany production SCD500 type high vacuum coating apparatus coating on concrete specimens.From 0 d to 120 d, the uniaxial static compression test results of concrete specimens corroded by sulfate are as follows. From 0 d to 120 d, the compressive strength of the W group is 56.84 MPa, 62.04 MPa, 63.16 MPa, 64.98 MPa, and 65.16 MPa, respectively. The compressive strength of the S group was 56.48 Mpa, 63.14 Mpa, 62.36 Mpa, 60.65 Mpa, and 55.85 Mpa, respectively. For dynamic test results, see The test pieces were damaged to different degrees under dynamic compression. The stress–strain curve may reflect a complete process from loading to failure macroscopically. Based on the “three-wave method”, the stress–strain curves for plain concrete test pieces at different strain rates and different erosion times were obtained, as shown in The dynamic compressive strength of the test pieces depended on the stress value corresponding to the peak point of the stress–strain curve, reflecting the characteristics of concrete in strength under an impact load.The dynamic strength growth factor  For the two test piece groups eroded for 90 d and 120 d, and with the increase in strain rate, the growth rate of dynamic compressive strength decreased gradually, indicating that, at the same strain rate, for the test piece groups with longer submersion times in the Na2SO4 solution, the dynamic compressive strength loss increased with the strain rate. (4) The dynamic strength growth factor also had an obvious enhancement effect on the strain rate, and the effect of the dynamic strength growth factors in the test groups with longer submersion times were weaker than in the test groups with shorter submersion times.IT) represents the energy change in concrete under dynamic load, i.e., energy absorption capacity. Physically, it is the area under the stress–strain curve, which may be expressed as:f represents the dynamic stress–strain curve of the test piece and u,ε is the dynamic limit strain of the curve. Dynamic compressive deformation is an important reference index for analyzing mechanical characteristics of concrete under impact loads after sulfate attacks, with the peak strain (pε) and limit strain (uε) acting as the important mechanical parameters for the impact compressive deformation performance of concrete. Under different strain rates, impact toughness, peak strain, and limit strain have roughly the same upward trend, as shown in In this study, the impact toughness  and (5), respectively, with the static compressive strength as a criterion for damage degree.2 = 0.9679 (the W group), R2 = 0.9471 (the S group). Thus, the correlation was high, and the fitting results were optimal.The fitting results are shown in (6), and the relevant relation diagram is shown in The compressive strength and erosion resistance coefficient were used to analyze the degradation law of concrete test pieces. Therefore, according to classical mechanics, The following can be obtained according to the Formula (8):Substituting it into the Formula (8), the test piece damage variable defined by the wave velocity can be obtained as:Concrete specimens are affected by the erosion of sodium sulfate solution, which mainly includes the erosion of sulfate and the continuous hydration of concrete. In order to separately analyze the influence of sulfate erosion on concrete, where 2SO4 occurred between the skeleton and the pore bulk, and there were many consolidation products in the pores and increasing consolidation products amplify the defects. The static mechanical properties and dynamic mechanical properties decreased to different degrees as the wave velocity decreased based on acoustic measurements.The acoustic velocity of the W group soaked in distilled water is the initial speed of the material, while that of the S subjected to sodium sulfate erosion is the speed after the material was damaged. The static mechanical properties and dynamic mechanical properties decreased to different degrees as the wave velocity decreased based on acoustic measurements. Through the tests, the static and dynamic mechanical properties measured in this study were basically consistent with the performance of concrete under the condition of erosion . ThroughThroughout the sodium sulfate erosion process, the changes in static compressive strength and dynamic compressive strength of the concrete test pieces were primarily influenced by the following factors. (1) During the process of sulfate erosion, the test pieces were submerged in the solution. During the curing process, the concrete continued to hydrate with time, and the hydration continued during the submersion process. (2) In the process of sulfate solution immersion, concrete continues to hydrate, and sulfate also begins to enter into concrete. The reason why sulfate enters into concrete is that there is no liquid in the internal pores of concrete. Solution immersion makes liquid with sulfate enter into the sample due to the influence of water pressure. In addition, because the concrete surface has more pore structure, it also promotes the sulfate solution to enter the concrete interior. (3) During the hydration process for concrete, a calcium silicate hydrate gel was formed to fill in the defects and pores in the concrete pouring process. This makes the concrete stronger, and, as sulfate attacks concrete, while the consolidation products strength was lower than that of normal calcium silicate hydrate gel, it also led to an internal force effect, for which the overall damage degree of material was increased.In order to obtain the erosion situation of concrete buildings in service under special environment, the conclusion of ultrasonic test on concrete eroded by sulfate solution in this paper can be used to obtain the current damage state of concrete. In the actual working conditions, the concrete building may have eroded parts of ultrasonic detection, test data, and damage fitting curve comparison; thus, using the comparison of the results of the building performance and safety performance has a better evaluation and analysis. The damaged parts could bear the main dynamic load or static load of the position of reinforcement treatment to ensure that the concrete service during the work and safety, and, at the same time, to avoid a large range of reinforcement and mix anti-erosion treatment in the premise of ensuring safety to reduce the amount of concrete to achieve the purpose of low carbon environmental protection.In this study, the split Hopkinson pressure bar (SHPB) experiment was conducted with a true triaxial static-dynamic comprehensive loading test system.(1)The dynamic and static mechanical properties of concrete are weakened to a certain extent after sulfate erosion. The dynamic strain rate effect is significant, the dynamic compressive strength is decreased, and the impact toughness and deformation capacity are also weakened.(2)There are two main factors affecting the dynamic and static mechanical properties of concrete after being corroded by sulfate solution, including continuous hydration of concrete in solution and sulfate erosion. These two effects have two completely opposite influence trends on the dynamic and static mechanical properties of concrete. Hydration strengthens the properties of concrete, while sulfate erosion weakens the properties.(3)The law of changes in longitudinal wave velocity is similar to that of strength. Due to the changes in strength and internal pore structure of the test pieces after sulfate erosion. The longitudinal wave velocity is slower than that of concrete under normal environment and distilled water immersion condition. In addition, the compressive strength and the compressional wave velocity develop. In the same direction, in response to external influences, both the compressive strength and the compressional wave velocity of concrete have a decreasing trend after sulfate erosion.(4)For the concrete eroded by sulfate, the internal structure changed, within which a large number of low-strength consolidation products may be formed. In addition, the increase in the volume of reaction products and the crystals with strength weaker than that of normal gels may compromise the concrete strength.Static and dynamic mechanical testing of concrete was conducted 0 d, 30 d, 60 d, 90 d, and 120 d after undergoing erosion by a sodium sulfate solution with a mass fraction 15%. Acoustic waves were used for macroscopical detection and SEM for microscopical analysis. The main conclusions are:


The aim of this study was to analyze the antibiotics prescription habits, both prophylactically and therapeutically, of Spanish general dental practitioners in the management of endodontic infections in primary care. Two hundred Spanish general dental practitioners were asked to respond to a survey on indications for antibiotics prescription in the treatment of endodontic infections, being 190 general dentists (95%) included in the study. Data were analyzed using descriptive statistics and the chi-square test. The average duration of antibiotics therapy was 6.5 ± 1.0 days. In patients without medical allergies, most of them (97%) selected amoxicillin as the antibiotic of the first choice, alone (51.1%) or associated with clavulanic acid (45.8%); in patients with penicillin allergies, the drug of choice was clindamycin 300 mg (70%). For cases of symptomatic irreversible pulpitis, 44% of the respondents prescribed antibiotics, in the scenario of prophylactic antibiotic prescription, up to 27% of the general dentists prescribe according to non-current guidelines (1 g 1 h before or 1 g 1 h before and 1 g 1 h after) in non-indicated cases . It is necessary to improve the antibiotic prescription habits of Spanish general dentists in endodontics. One of the most serious threats to Spanish and global public health is the emergence of infections caused by bacterial strains resistant to treatment with antibiotics. A key factor in the emergence of bacterial resistance to antibiotics is the misuse of antimicrobial agents by healthcare workers. Approximately 10% of antibiotics dispensed in primary care are prescribed by dentists . CurrentEndodontic infections are very prevalent, being characterized by a polymicrobial microbiota, involving a combination of facultative Gram-positive, Gram-negative, and strictly anaerobic bacteria ,8. They Incorrect dosage and excessive duration of treatment are among the factors that have been associated with the development of bacterial resistance to antibiotics due to improper prescribing . The preSeveral studies have analyzed through surveys the antibiotic prescription habits of Spanish endodontists  and oralIn this cross-sectional descriptive survey, 200 Spanish general dental practitioners were asked to respond to a survey on indications for systemic antibiotics in the treatment of endodontic infections, as well as on antibiotic prophylaxis in endodontics. The only requirements for participation were to be a practicing dentist in primary care. The dentists who responded and completed the survey satisfactorily were 190 (95%), all of whom were included in the study. The dentists who participated in the survey did so anonymously, voluntarily, and without compensation.The questionnaire  was basep < 0.05.For the collection of the data, the Excel program version 15.40  was used, describing them by means of frequency tables. The numerical variables are expressed as mean ± standard deviation. The data were analyzed using descriptive statistics and the chi-square test. ANOVA and the Tukey test for independent samples were used to assess differences between groups. Significant differences were considered when n = 124) represented 65.3% and the men 34.7% (n = 66). The average age of the respondents was 30.5 (SD = 7.8), with the age group ≤ 30 being the most predominant (65.8%). Referring to the average experience as a dentist was 74.0 ± 88.7 months, with low experience being more prevalent (65.8%). The number of weekly root canals was 4.3 (SD = 4.7).The demographics of the 190 participants are described in p > 0.05) (The majority of respondents (96.8%) selected amoxicillin as the first-choice antibiotic in patients without medical allergies, either alone (51.1%) or in combination with clavulanic acid (45.8%) . Dentist > 0.05) . GroupinRegarding the antibiotic preferences of dentists in patients with penicillin allergies, clindamycin 300 mg was the first drug of choice (70%) .p = 0.15).The average duration of antibiotic therapy was 6.5 ± 1.1 days. Most respondents (71%) prescribed antibiotics for 7 days. No highly experienced general dentist eliminates antibiotic therapy when systemic symptoms cease. Only 7% of dentists, particularly all of them with less experience, prescribe antibiotics until systemic symptoms disappear . Differep > 0.05).p > 0.05). Dental practitioners prescribe antibiotic prophylaxis mainly for patients at risk of infectious endocarditis (97.4%). Misprescription of antibiotic prophylaxis in patients being treated with oral bisphosphonates was higher in the group with less experience. No significant differences were found (p > 0.05).The results obtained on clinical procedures, guidelines, and patients with indications for antibiotic prophylaxis are described in This is the first study that reflects the current state of knowledge and prescribing habits of Spanish general dentists on the indications of systemic antibiotics in the treatment of pulp-periapical infections and antibiotic prophylaxis in the area of endodontics. The analysis of the data shows that a great majority of people select correctly the type of antibiotic for the treatment of these infections, as well as for the prophylaxis, but there is a high rate of generalists who prescribe antibiotics inaccurately.n = 190) was similar to previous studies [The sample of the present study n = 90 was si studies ,5, with Recently, the European Society of Endodontics (ESE) and the Spanish Endodontic Association (AEDE)  have devp > 0.05). This could be explained by the lack of updating based on scientific evidence by more experienced dentists who continue to apply obsolete clinical guidelines.The results of the present study coincide with the rest of Spanish surveys ,3,5,6 anIn patients with allergies to β-lactams, the results of this study coincide with the rest of the Spanish surveys ,3,5,6 anp = 0.15).The average duration of antibiotic therapy was 6.5 ± 1.1 days, and most of the respondents (71%) prescribed antibiotics for 7 days, coinciding with the rest of the Spanish surveys ,5,6. No p > 0.05). Therefore, high experienced dentists prescribe more erratically than those with less experience.With regard to endodontic clinical situations requiring antibiotics as coadjutants in endodontic treatment, even though they are only indicated in the last situation proposed in the survey , the present study shows high percentages of prescription in clinical situations that do not require it. The high percentage of prescriptions in the last clinical situation 91.1%) coincides with previous studies .1% coinc,5,6. Howp > 0.05).Clinical recommendations on the use of prophylactic antibiotics in compromised patients have been changing , which mlocus minoris resistentiae, it is very important to assess each case individually. The erroneous prescription of antibiotic prophylaxis in patients being treated with oral bisphosphonates was high (16.3%), being higher in the group with less experience (p > 0.05). Therefore, despite the fact that ignorance of the antibiotic prophylaxis regimen is high in both groups, it is more prevalent with less clinical experience.Antibiotic prophylaxis should be considered in immunosuppressed patients with a blood neutrophil count < 500/µL and, in patients with The results of the present study show that it is necessary and essential to developing new strategies to improve the knowledge and prescribing habits of general dentists in Spain in the treatment of pulp-periapical conditions and the indication of prophylaxis in endodontic clinical settings. To this end, the teaching of educational programs on antibiotic prescription and patient management must be improved in official studies in dentistry and in continuing education programs offered by the various professional associations of dentists, as well as by the various scientific societies in the sector.Most general dentists working in primary care are selecting the appropriate antibiotic and indicating it when it really is needed in the treatment of endodontic infections. However, there are still dentists who prescribe antibiotics inappropriately and do not follow the position of the European Society of Endodontics (ESE) and the Spanish Endodontic Association (AEDE). The use of antibiotics for minor infections, or in some cases in patients without infections, as well as unnecessarily prescribed antibiotic prophylaxis, could be a major contributing factor to the global problem of antimicrobial resistance. It is necessary to propose measures to improve the correct prescription of systemic antibiotherapy in the treatment of endodontic infections.


The use of conductive concrete is an effective way to address snow and ice accretion on roads in cold regions because of its energy saving and high efficiency without interruption of traffic. Composite conductive concrete was prepared using graphene, carbon fiber, and steel fiber, and the optimum dosage of graphene was explored with resistivity as the criterion. Subsequently, under the conditions of an initial temperature of −15 °C and a wind speed of 20 km/h, the extremely severe snow event environment in cold regions was simulated. The effects of electrode spacing and electric voltage on snow melting performance of conductive concrete slab were explored. Results showed that graphene can significantly improve the conductivity of conductive concrete; the optimal content of graphene was 0.4% of cement mass in terms of resistivity. The snow-melting power of conductive concrete slab decreased with increase in electrode spacing and increased with increase in on-voltage. For an optimal input voltage of 156 V and an optimal electrode spacing of 10 cm, the time required to melt a 24 h snow thickness (21 cm), accumulated during a simulated severe snow event, was only 2 h, which provides an empirical basis for the application of graphene composite conductive concrete to pavement snow melting in cold regions. Severe ice and snow events are climate events that affect traffic safety and the service reliability of concrete road engineering. In recent years, the frequency of severe ice and snow events has increased year-on-year, which has not only seriously disrupted normal urban activities, but has also caused great loss of property and life. Statistical evidence suggests that approximately 10–15% of road traffic accidents are caused by severe ice and snow events [Traditional conductive concrete pavements usually use graphite, carbon fiber, and steel fiber, as conductive fillers, but they have certain limitations. Adding graphite into concrete can significantly improve the conductivity of cementitious materials, but due to the large amount of graphite required, the mechanical properties of the materials decrease significantly, such that they cannot meet the basic strength requirements of road engineering ,3. Carbo−6 Ω·cm, which can enable conductive concrete to achieve good electrical conductivity at low concentration. It has potential application in conductive concrete [With the development of powder technology and nanotechnology, conductive materials are also being developed at the nanometer scale. Graphene is a new nanomaterial with excellent mechanical and electrical conductivity. Its resistivity is only 10concrete ,15,16,17concrete  added 0.concrete  found thconcrete  suggeste3 and with electrode spacing of 1 m. At the Des Moines International Airport in the US, 38mm thick snow melted within 3.5 h of exposure to 210V alternating current outdoors. Arabzadeh et al. [3 with electrode spacing of 125 mm. They applied 40 V AC  and melted 190 mm thick snow over 2 h. Tang et al. [3 carbon fiber conductive concrete plates and applied a 25 mm thick insulation layer at the bottom of the plates, which melted 31 mm thick snow in the field over 1 h. The above snow-melting tests have confirmed the snow-melting performance of conductive concrete slab, but there has not been further investigation into the factors influencing the conductive performance of conductive concrete. There is, moreover, a lack of targeted research on heating efficiency in the practical application of conductive concrete.In order to further explore the application of graphene in the design of cement-based materials, it is necessary to assess the feasibility of the application of graphene composite conductive concrete to road snow melting in severe cold regions, and to consider solutions to the existing problems of conductive concrete in conductivity, snow melting efficiency, and snow melting energy consumption. At present, conductive concrete slabs are prepared for submission to deicing and snow melting tests ,23,24,25h et al.  added 1%g et al.  preparedAccording to existing research, the layout parameters of conductive concrete slab electrodes have a great influence on the thermal efficiency of the material ,29,30, b2, when the temperature is −10 °C, the heating power should exceed 350 W/m2, and when the temperature is −5 °C, the heating power should exceed 250 W/m2. Therefore, it is necessary to optimize the voltage required for snow melting according to the specific snow event conditions, to improve the efficiency and economy of snow melting.Most studies on the snow melting and deicing behavior of conductive concrete have not considered the grade of the severe snow event, or the differences in the energy consumption of snow melting under different snow intensities. Currently, investigations are mainly focused on snow melting efficiency and required energy consumption by adjusting the input power, specifically, the input voltage . Zhang eIn this study, three-phase, composite conductive concrete was prepared with multilayer graphene, carbon fiber, and steel fiber as conductive materials, and its conductive mechanisms were studied. The optimal content of graphene in conductive concrete was determined by its resistivity. In addition, the effect of the electrode spacing arrangement and the electric voltage on snow melting efficiency of conductive concrete slab was explored, in order to meet the snow melting performance requirements of graphene composite conductive concrete under severe snow conditions.3 apparent density, was used as fine aggregate. Gravel of 5–16mm calibre, with 0.2% mud content, and 2587 kg/m3 apparent density, was used as coarse aggregate. Graphene used in this experiment was produced by Changzhou Sixth Element Materials Science and Technology Co., Ltd., Changzhou, China. Graphene, carbon fiber, and steel fiber were selected as conductive fillers; their performance parameters are shown in P·O 42.5 Portland cement was used as cement. Natural river sand, with 3.0 fineness modulus, 0.1% mud content, and 2620 kg/mIn this paper, 0.4 wt.% carbon fiber and 1% vol. steel fiber were mixed into concrete according to the volume exclusion law of multiphase conductive materials. In the composite, 0.2, 0.4, 0.6, 0.8 and 1 wt.% of graphene were selected. Tributyl phosphate, with 0.03% dosage of cement, was used as a defoamer. Superplasticizer, with 2% dosage of cement, was used as a water reducer. Sodium dodecyl benzene sulfonate was used as the dispersant of graphene; the dosage was twice that of graphene. Sodium nitrite was selected as the conductive strengthening agent, and the dosage was 2% of cement. The proportion of graphene composite conductive concrete is shown in Firstly, the graphene dispersion was prepared. An electronic balance was used to weigh graphene and sodium dodecyl benzene sulfonate. Then the mixed powder was placed into a 500 mL beaker and water was added. The beaker was placed on a magnetic stirrer and stirred for 5 min at 250 r/min. When the mixture was uniformly dispersed, without obvious foam, the mixture was poured into several 50 mL flat-bottom centrifuge tubes, and the centrifuge tubes were placed in an ultrasonic dispersion instrument at 500 °C and 40 kHz for 30 min. Finally, the centrifuge tube was removed and cooled to room temperature to prepare the graphene dispersion.For the preparation of the graphene composite conductive concrete test block and plate, cement, sand, stone, and steel fiber were first added to the cement mortar mixer and slowly stirred for 60–120 s. When the basic distribution of steel fiber was uniform, 3/4 of graphene dispersion was slowly added and stirred for 60 s. Carbon fiber and sodium nitrite were then added, and finally 1/4 of the graphene dispersion was added with polycarboxylate superplasticizer and tributyl phosphate with slow stirring for 120 s. When the mixture was evenly mixed and no obvious bubbles were generated, the mixture was poured into the mold to prepare the graphene composite conductive concrete test block and plate, the electrode plate was inserted, and the vibration table was used for compaction molding. After natural curing for 24 h, the block was demolded and put into a standard curing room for 28 days at 20 °C and 95% humidity.3, the electrode size was 29 × 29 × 4 cm3, the electrode spacings were 10 cm, 18 cm, and 28 cm, and the on-voltages were 128, 156, and 220 V, respectively. The electrode layout is shown in The size of the graphene composite conductive concrete slab was 30 × 30 × 5 cm3 were removed after standard curing for 28 d in the curing room. Applying the standard test method for the physical and mechanical properties of concrete (GB/T 50081 2019) [The specimens of dimensions 100 × 100 × 100 mm81 2019) , the com2; The electrical conductivity of the graphene composite conductive concrete after 28 days of curing was characterized by assessment of resistivity. The resistivity of the graphene composite conductive concrete was measured by the two-electrode method, and the adjustable voltage regulated AC power supply (YM-1800 A) was used for testing. With the power off, the positive and negative poles of the concrete test block were connected to the positive and negative poles of the power supply by wire. The AC power was connected, and the output frequency of the AC power supply was adjusted to 50 HZ, with a voltage of 108 V. The voltage and current of the power instrument screen were read, and the resistivity was calculated according to the volt-ampere law and Equation (1).After the specimens had been cured for 28 days, the interfacial transition zone of the graphene composite conductive concrete specimens, with graphene content of 0, 0.2, 0.4, 0.6, 0.8, and 1.0 wt.%, were sampled. After the samples were treated, they were examined by Zeiss SUPRA55 scanning electron microscope in low vacuum mode, and SEM scanning was performed under 20 kV accelerated voltage.After the curing of the graphene multiphase conductive concrete slab was completed, it was removed. The AC voltage stabilizer was connected to the positive and negative electrodes of the board with a wire in the power-off state. A polyurethane foam plate with a thickness of 2 cm was laid around and at the bottom of the concrete plate as an insulation layer and placed in a refrigerator (BC/BD-307HNE) to effect an indoor snow melting test. The snow was evenly spread on the surface of the conductive concrete plate to the thickness of 21 cm . TheThe AC voltage regulator (YM-1800 A) was used to input 108 V, 156 V, and 220 V AC currents. The snow thickness was measured and recorded every 15 min until complete melting was achieved. The current and voltage data of the AC voltage regulator were read and the resistance of the graphene composite conductive concrete plate was calculated according to ohmic law. An infrared thermometer (HT650C) was used to test and record the temperature of each measuring point distributed evenly on the surface of the concrete slab. Finally, the average value of the temperature measuring points was taken as the temperature of the concrete slab, and the time-average temperature diagram was drawn. The schematic diagram of the snow melting test is shown in The results of the compressive tests are presented in 2/V·s at room temperature; adding an appropriate amount of graphene in concrete can reduce the potential energy of electronic transition in the concrete matrix. When inputting AC test resistance, the probability of electronic transition can be greatly improved, and then the conductivity of concrete can be improved.The resistivity results of conductive concrete at 28 days with different graphene contents are shown in However, with an increase of graphene content above 0.4 wt.%, the resistivity gradually stopped decreasing and showed an upward trend. With a large amount of graphene, it is easy for it to agglomerate and affect the formation of the conductive network. Furthermore, due to the large specific surface area, a large amount of water will be absorbed during the preparation of conductive concrete, which affects the conductivity. In order to meet the design resistivity for snowmelt and de-icing of the graphene composite conductive concrete, and to reduce the cost within the design range of resistivity, the optimal content of graphene was determined to be 0.4 wt.%.With the incorporation of graphene, the conductive network in the composite conductive concrete is shown in SEM images of the interface transition zone of the composite conductive concrete samples with different graphene content are shown in When the graphene content increased to 0.4 wt.%, As shown in When the content of graphene was further increased to 0.8 wt.% and 1 wt.%, it can be seen from P, electric heating power, W; ∆t, snowmelt time, s; m, quality of graphene conductive concrete, kg; PC, specific heat capacity of graphene conductive concrete, J/kg·K; ∆T, temperature change of concrete slab, K; im, quality of snow, kg; PiC, specific heat capacity of snow, J/kg·K; ∆Ti, average temperature change in snow during snow melting, K; LQ, melting heat of snow, J; SQ, heat loss during snow melting, J.The snow melting process of the graphene composite conductive concrete is a process of converting electrical energy into thermal energy. When using the thermal effect of conductive concrete to melt snow, according to the law of conservation of energy, it is known that the heat generated by the conduction of graphene conductive concrete should be equal to the sum of the heat absorbed by the heating of concrete slab, the heat lost in concrete slab and air, and the heat absorbed by the heating and melting of snow. The relationship is expressed as:The energy utilization ratio of graphene composite conductive concrete is the ratio of heat absorbed by snow heating and melting to input electric energy:After applying voltage at both ends of the graphene composite conductive concrete plate, the current flows in the low resistance area of the plate, and a large amount of Joule heat will be produced over time. The generated heat first increases the temperature inside the plate. According to the heat conduction effect, when there is a temperature gradient inside or between objects, there will be energy transferred from the high temperature region to the low temperature region. Therefore, part of the heat will remain in the interior of the plate and continue to heat, and the other part will transfer to the surface of the plate with low temperature, which will increase the surface temperature. When the temperature on the surface of graphene composite conductive concrete slab rises above 0 °C and exceeds the melting point of ice and snow, the heat absorbed by snow covering the surface of the slab begins to melt, to achieve the purpose of electrified snow melting.The snowmelt effect of graphene composite conductive concrete slabs with different electrode spacing at 220 V and a snow thickness of 21 cm is shown in After the second stage was electrified for 35 min, the snow on the graphene composite conductive concrete slab began to melt under different electrode spacings. After a period of continuous power supply in the third stage, the snow melting rate increased. With the continuous conduction time, it can be seen from In the fourth stage, the snow melting rate gradually decreased until the snow melting was completed. This is because with the decrease of snow thickness, the effect of wind speed on heat loss near the snow layer was more significant, which reduced the retention of heat in the snow and affected the energy saving of the snow layer. Therefore, in the fourth stage, the heat transferred to the snow layer was reduced, and the heat storage of the snow layer itself was also reduced, so the snow melting rate was weakened compared with that in the third stage.The resistance and current of the graphene composite conductive concrete slab at different electrode spacings are shown in The snow-melting power of the conductive concrete slab with different electrode spacing is shown in The snow melting effect of the graphene multiphase conductive concrete slab under different energizing voltages when the electrode was spaced at 10 cm is shown in The resistance and current of the graphene composite conductive concrete plate under different voltages are shown in The input power of the graphene composite conductive concrete slabs at different voltages is shown in When the content of graphene was 0.4% of the cement mass, the mechanical properties and electrical conductivity of the conductive concrete were significantly improved. The compressive strength first increased and then decreased with the increase of graphene content and reached a maximum strength of 45.3 MPa when the content was 0.4%. The resistivity decreased with increase in graphene content. When the content reached 0.4%, the resistivity gradually stopped decreasing and showed an upward trend; the minimum resistivity was 12.66 Ω·m.2 and energy consumption density of 7.8 kW·h/m2.With increase in electrode spacing, the snow-melting efficiency and energy consumption of the graphene composite conductive concrete slab reduced. When the electrode spacing was 10 cm, snow of 21 cm thickness could be rapidly melted within 1.2 h, with a required average power density of 6.5 kW/mThe snow melting power of the graphene conductive concrete increased with increase in the electrified voltage, but the overall snow melting energy consumption first decreased and then increased with increase in the voltage. From an economic point of view, when the voltage was 156 V, the overall snow melting energy consumption was optimal.2 and the energy consumption density was 6.6 kW·h/m2.With 21 cm snow thickness formed in 24 h, simulating the conditions of a heavy snowstorm, the graphene composite conductive concrete slab prepared in this experiment could quickly melt the snow in 2 h with electrode spacing of 10 cm and an input voltage of 156 V, without affecting road traffic. The average power density was 3.3 kW/mThree phase composite conductive concrete was prepared with multilayer graphene, carbon fiber, and steel fiber as conductive materials. The optimum content of graphene in conductive concrete was sought with resistivity as the criterion. The effects of electrode spacing and energizing voltage on snow melting efficiency were studied. The following conclusions can be drawn from the results of this study: