Chemogenetic activation of these neurons increased RA and burying behaviors toward a novel object without affecting anxiety and corticosterone levels. Ablation of these neurons caused the abnormal behaviors of gnawing and direct contacts with novel objects, especially in a home-cage. These results suggest that PeFA Ucn3 neurons modulate defensive responses to a potential threat stimulus.Defensive behaviors are evolved responses to threat stimuli, and a potential threat elicits risk assessment (RA) behavior. However, neural mechanisms underlying RA behavior are hardly understood. Urocortin-3 (Ucn3) is a member of corticotropin-releasing factor peptide family and here, we report that Ucn3 neurons in the hypothalamic perifornical area (PeFA) are involved in RA of a novel object, a potential threat stimulus, in mice. Histological and   •The activity of PeFA Ucn3 neurons is associated with novel object investigation•DREADD activation of PeFA Ucn3 neurons increases RA and burying of novel objects•Ablation of PeFA Ucn3 neurons causes direct contact with a novel object•PeFA Ucn3 neurons modulate defensive responses to novel objects Biological Sciences; Neuroscience; Behavioral Neuroscience Defensive behaviors are a set of evolved responses to threat stimuli to avoid or reduce potential harm . VariousUrocortin-3 is a member of the corticotropin-releasing factor (CRF) peptide family, which has been identified in humans and rodents . Ucn3 biAccumulating evidence has suggested that PeFA Ucn3 and its receptor, CRFR2, play an important role in energy homeostasis  and streUcn3-Cre mice. Finally, we examined the behavioral effects of activation and ablation of PeFA Ucn3 neurons including anxiety-like behavior; the former made use of a pharmacogenetic method (designer receptors exclusively activated by designer drugs [DREADD]) and the latter used targeted cell ablation with diphtheria toxin subunit A (DTA) in Ucn3-Cre mice.In the present study, we aimed to identify a stimulus activating PeFA Ucn3 neurons and elucidate the behavioral effects of activation/ablation of these neurons, including anxiety-like behaviors. To this end, we first investigated the reactivity of PeFA Ucn3 neurons to various forms of stimulus by c-Fos immunolabeling, a marker for activated neurons. Second, we performed fiber photometric analysis to identify behaviors associated with the activity of these neurons by Cre-dependent expression of GCaMP7s in PeFA Ucn3 neurons using + neurons located −0.7 mm posterior to bregma co-expressed Enk (+/Enk+ nerve fibers were observed in the LS but not in the PVN or VMH (+/Enk+ fibers formed perisomatic baskets around LS neurons (Ucn3-Cre mice (Ucn3-DTA) or their wild-type littermates as a control  or neutral (eugenol) odor , interma+ cells B. The pe+ cells, a novel object stimulus was given in a cage without bedding material (empty cage) to block the behavioral expression of burying. A novel object stimulus in the cage induced c-Fos expression in Ucn3+ cells; the percentage of c-Fos+/Ucn3+ cells to Ucn3+ cells in the novel object group was significantly higher than that of the empty-cage  adeno-associated virus (AAV) encoding GCaMP7s, a calcium indicator, was injected into the PeFA of Ucn3-Cre mice at −0.82 mm to the bregma , a novel object (block 2), and the same familiar object again (block 3) for 5 min in each block C. In theA representative trace of the calcium signals during the block 2 experiment is shown in We next investigated whether sniffing or the distance between the nose and a novel object affects the activity of PeFA Ucn3 neurons. We classified SAP-related behaviors into two forms with reference to a previous study with slight modification ; SAP-sniUcn3-Cre mice (+ cells were mainly observed between the fornix and PVN from −0.58 to −0.94 mm to the bregma (+ cells were immunoreactive for Ucn3 (+ cells (n = 5), whereas saline injection induced c-Fos in 2.62 ± 1.2% of mCherry+ cells  into the PeFA at −0.82 mm to the bregma in Cre mice A. In thee bregma B. The mafor Ucn3 C. IntrapThe open field test followed by the novel object test was performed to evaluate anxiety-like behaviors, in accordance with previous studies . AlthougWhen a control vector, AAV: hSyn-FLEX-mCherry, was injected into the PeFA with the same coordinate A, CNO adThe marble-burying test is widely used to examine burying activity in mice and is also applied to evaluate anxiolytic and anticompulsive drug actions . CNO tre+ cells and their Ucn3 expression were confirmed after behavioral testing. Results are shown in + cells were distributed from −0.58 to −0.94 mm to the bregma .We next investigated the effects of ablation of PeFA Ucn3 neurons on anxiety-like behaviors, responses to a novel object, and burying behavior. As described in Cre mice A. Almostrol mice C, novel rol mice D, and marol mice E; there We next investigated the behavioral responses to a novel object in a home-cage using Ucn3-DTA mice. When a novel object (plastic tube) was put in the home-cage, the number of SAP toward the object and activity in the cage were comparable between control and Ucn3-DTA groups, whereas Ucn3-DTA mice gnawed and persistently sniffed the object F. When aTo examine whether mice actually touch novel objects, we used a shock prod that releases an electric current only when a moist object, such as the nose or mouth, touches the prod. The probability that mice receive an electric shock in Ucn3-DTA group reached 100% within 15 min, whereas the probability of control mice reached a maximum of 50% within the same time window I. These Because Ucn3 and CRFR2 have been shown to modulate metabolism , we measThe purpose of the present study was to identify stimuli that activate PeFA Ucn3 neurons and elucidate the behavioral effects of activation and ablation of these neurons, including anxiety-like behaviors. Here, we first demonstrated that the activity of PeFA Ucn3 neurons was increased by a novel object stimulus and associated with SAP behavior during novel object investigation. Second, activation of PeFA Ucn3 neurons had no effects on anxiety-like behaviors at least in non-stressed animals as measured by open field, light-dark box, elevated plus-maze tests, whereas it increased SAP and sniffing toward a novel object and burying behavior. Third, ablation of PeFA Ucn3 neurons had no effects on the behavioral expression of SAP and burying, whereas it induced much close and direct contacts with a novel object including gnawing and persistent sniffing, particularly in the home-cage. These abnormalities led to an increased risk of mice receiving an electric shock when the object was an electrified prod. Finally, neither activation nor ablation of these neurons affected plasma corticosterone level. These results indicate that PeFA Ucn3 neurons modulate RA toward novel objects and likely contribute to keep an appropriate distance from the object to avoid the risk brought by potential threats particularly in the habituated environment of a home-cage.It is generally believed that CRF/CRFR1 signaling promotes stress responses and anxiety-like behavior, whereas Ucns/CRFR2 mediates stress recovery and the restoration of homeostasis; however, recent studies reveal that this view is overly simplistic and CRFRs signaling are brain-region- and cell-type-specific . ImportaAlthough the reason for these inconsistent findings on the functions of LS Ucn3/CRFR2 signaling in the context of anxiety is not entirely clear, there are at least three possibilities. First, as demonstrated by Ethologically, both RA and burying behaviors in rodents are categorized as defensive behavior . A simplThere is an interesting hypothesis that suggests defensive behaviors can be divided into two categories, active and passive . It is iAnother important point is that the ablation of these neurons had no effects on the behavioral expression of RA and burying, which suggests that a critical center for regulation of these behaviors exist somewhere else in the brain. We believe that the most probable region is the septum including the LS, because a large number of studies have reported that a septal lesion decreases defensive burying  and the Based on the above hypothesis, when the novel object test is performed in a novel environment, even though PeFA Ucn3 neurons are ablated by DTA, novel-environment- and novel-object-responding neurons stimulate RA/Burying regulatory neurons C, left. The results of c-Fos expression experiments indicate that stressful events, aggression, predator odor, and pain, are not likely to be a direct factor to activate PeFA Ucn3 neurons, and a novel object stimulus, a form of potential threats, can activate these neurons. Although many studies demonstrate that central Ucn3 and CRFR2 are involved in stress-related responses , this stConsidering the fiber photometry result that the peak of calcium signal was observed when the mice withdrew from a novel object, increased physical contacts and the failure of keeping an appropriate distance from a novel object in Ucn3-neurons-ablated mice may be caused by impairments in withdrawing from the object. Through such fine behavioral modulations, PeFA Ucn3 neurons probably contribute to avoiding the risk brought by potential threats during RA and play an important role in animal survival.There is a report demonstrating that PeFA Ucn3 neurons, particularly a rostral population , not caudal, were activated by infant-direct aggression . Based oFirst, although this study found that novel objects activate PeFA Ucn3 neurons, the stimuli used for our experiments was very limited. Thus, the present results cannot deny the possibility that PeFA Ucn3 neurons could be activated by other kinds of stimuli other than a novel object. Particularly, although predator odor is known to elicit RA behavior , it is uhayashi@naramed-u.ac.jp).Further information and requests for resources and reagents should be directed to and will be fulfilled by the Lead Contact, Noriko Horii-Hayashi (The study did not generate new unique agents.This study did not generate/analyze datasets and code.All methods can be found in the accompanying


Black shale, which usually contains pyrite, is easily oxidized and generates acid discharge. This acidic environment is not favorable for concrete in engineering applications and is likely to affect the durability of engineering structures. This study investigated the effect of acid discharge from the weathering of black shale on the strength of concrete under partially immersed conditions. Black shale concrete immersion tests were conducted at different immersion depths to evaluate the oxidation conduction of black shale. Water chemistry and oxidation products were monitored during and after the immersion tests. The quality and strength of the black shale and concrete specimens were obtained before and after the immersion by testing the ultrasonic wave velocity and uniaxial compressive strength. The results indicated that a lower immersion depth of black shale reveals a higher degree of oxidation, and the capillary zone in black shale is critical for black shale oxidation in terms of mass transfer. The ultrasonic velocity of the concrete showed different change patterns in the immersed and non-immersed zones. Precipitation and additional hydration enhanced the quality and entirety of the concrete (increased ultrasonic velocity) at the non-immersed or partially-immersed zones, while the dissolution of concrete was dominant in the immersed zone (decreased ultrasonic velocity) and induced a reduction of concrete quality. The compressive strength of the concrete was enhanced after immersion. The concrete strength slightly increased by 5–15%. This phenomenon is attributed to the filling of the voids by the precipitations of minerals, such as goethite and anhydrite. The area has a humid tropical climate, and the black shale is abundant in carbon and pyrite, with a scarcity of fossils. Rock samples were taken from a depth of 1 m from the outcrop surface, following the procedure described in Liao et al. . The rocTo evaluate the effect of the acidic discharge produced by black shale on the concrete, laboratory black shale-concrete immersion tests were set up to mimic in situ conditions. In this study, the cylindrical black shale specimens were partially immersed in deionized (DI) water at different immersion heights (30 mm and 50 mm or 30% and 50% immersed), which was designed to simulate the water-rock interactions under partially saturated conditions . The bla3 of coarse aggregate (5–25 mm continuous-grade crushed stone), 750 kg/m3 of fine aggregate , 7.5 kg/m3 of polycarboxylate superplasticizer, and 410 kg/m3 of cement with water (water/cement ratio = 0.45) before it was cured for 28 days in a room with 100% humidity. The initial mineralogy analysis of the fresh concrete specimen showed that the concrete cubes mainly consisted of quartz, albite (Na(AlSi3O8)), slaked lime (Ca(OH)2), and Magnesium silicate hydroxide (Mg3Si4O10(OH)2).At the same time, a concrete cube (150 mm × 150 mm × 150 mm) was placed in the acrylic tank to evaluate the effect of acid discharge from the black shale on the physical and chemical properties of the concrete. During the immersion tests, half of the concrete cube (75 mm) was immersed in the DI water. The concrete cube was created by mixing 1060 kg/mThe testing program of laboratory immersion tests is shown in −) and sulphate (SO42−), were analyzed by ion chromatography .Water samples from the acrylic tank were taken after the 40-day testing period. The water samples were purified after centrifuging at 4000 rpm for 20 min, and the supernatant was then filtered through 0.45 μm filters and transferred to a 15-mL polypropylene centrifuge tube for chemical analysis. The bulk chemical parameters, including pH and EC, were analyzed using a benchtop pH and conductivity meter . Major elements, including aluminum (Al), iron (Fe), magnesium (Mg), calcium (Ca), sodium (Na), silicon (Si), and potassium (K), were analyzed by inductively coupled plasma optical emission spectrometry . The major anions, including chloride  of each test specimen  after the laboratory immersion tests was evaluated by an electro-hydraulic servo rock test system . The UCS test is considered to be time-efficient, low-cost, and easy to operate. The length to diameter ratio (L/D) of the cylindrical black shale was set to be 2 , and the L/D of the cubic concrete was set to be 1 , which is consistent with the requirement in ASTM C39/C39M-12. During the tests, the loading displacement was set to be 0.1 mm/min until the specimen failed and the maximum normal stress could reach up to 100 MPa. Stress and strain results were recorded through an electronic system that has 1% accuracy.The temporal behavior of the solution pH in the laboratory immersion test is shown in However, a different temporal behavior was observed for tests with both black shale and concrete specimens. The initial pH values of No.2 and No.3  were both 4.1. These pH values increased within 6 days and then fluctuated in the weak acid range (5.0–6.5). The deeper immersion of black shale induced slightly lower water pH during the early stage of weathering. The initial pH values of No.4 and No.5  were 3.9 and 4.1, respectively. However, a similar change of pH was observed within the first 6 days as that of No.2 and No.3, where the pH values increased within 6 days and then fluctuated between 6.5 and 7.5. This change of pH could be due to the balance between the acid-producing (pyrite oxidation) and alkali-producing (concrete dissolution) reactions. In general, the pH values of groups No.2 and No.3 were lower than those of groups No.4 and No.5, indicating that a lower immersion depth generates a lower overall solution pH.42− (1022.9 mg/L), which are the major oxidation products of pyrite (3+)  a. The oxite (3+) b. On the2 and KOH), which can be easily neutralized and dissolved by acid attack. The lower immersion depth  produced a higher abundance of oxidation products, such as Fe and SO42−, than tests with a higher immersion depth . This phenomenon is consistent with the pH of the water, where the pH is higher with a deeper immersion depth. The reason for this is likely due to the higher exposed surface to the atmosphere at a lower immersion depth where oxygen is more easily obtained. The higher pH of No.4 and 5 also induced a higher potential for mineral precipitation. The water chemical parameters  were oversaturated in the water after the laboratory weathering tests ), while FeOOH is the precipitation by the excessive ferric ions in water (Equation (2)).Increased release of Ca and K was evident when acid discharge from the black shale attacked the concrete. The concentration of Ca increased from 2.8 mg/L (No.1) to 20.0–436.6 mg/L (No.2–5) and the concentration of K increased from 97.6 mg/L (No.1) to 127.7–314.6 mg/L (No.2–5). These elements come from the dissolution of the major constituents of the concrete eters in  were inpng tests . 3CaO·Al42− also brought the potential for precipitation of anhydrite (CaSO4) and gypsum Equations (3) and (4), where the saturation index was close to 0 (−0.1 to −1.7 for CaSO4 and −0.3 to −2.0 for CaSO4·2H2O). The presence of these minerals may induce swelling and cracking if precipitation occurs in the pore structure of the concrete due to the volume change of these minerals [This precipitation of FeOOH was driven by the change in water pH, where the concrete was alkali and brought in hydroxide to the immersion water. Additionally, the presence of the oxidation product SOminerals ,19.42−, in the immersion solution was relatively higher in the tests with lower immersion depth. Therefore, the saturated zone may not be very critical for pyrite oxidation compared with the capillary zone. Benavente et al. [In general, the effect of immersion depth on the weathering of black shale was evident. A lower immersion depth represented a lesser contact surface with water. However, in this study, a lower immersion depth of black shale led to a higher degree of pyrite oxidation. The concentration of weathering products, such as Fe and SOe et al.  found th4), and anhydrite (CaSO4) appeared in the mineral phase after the immersion, indicating the precipitation of these minerals in the void spaces of the concrete. The precipitation occurred in both the immersed and non-immersed zones, showing that the capillary zone may have a strong effect on the mass transfer under partially immersed conditions.Ultrasonic velocity increases with the density and continuity of the sample. Therefore, in this study, higher ultrasonic velocity revealed a better quality and continuity (less voids) of the concrete. The ultrasonic velocity of each concrete specimen before and after the immersion tests is shown in However, no obvious change in ultrasonic velocity in the bottom layer was evident in general. The bottom layer presented a slightly lower ultrasonic velocity under acid water (3.6 µm/mm of C2 to C5) compared to that of concrete without acid water (3.7 µm/mm of C1). This phenomenon indicates that immersion in acid water would have a slightly negative impact on the quality of the concrete. This layer was immersed in the water, and the concrete underwent strong mineral dissolution. Although the precipitation of anhydrite, iron sulfate hydroxide, and goethite were evident in this layer a, the diThe compressive strength of the concrete and black shale samples was examined before and after the immersion tests. Black shale specimens from R2, R3, and R4 could not be obtained due to the inordinate fractures and cracks. Therefore, only the relatively integrated black shale specimens (R5 and R6) and concrete specimens were tested in this study. The strains to reach the maximum compressive strength (fc’) were similar before (0.7%) and after (0.6%) the immersion, and the elastic ranges of the black shale were also identical for all immersion conditions a. The elThe concrete had a slight reduction in compressive strength  after immersion in DI water for 40 days but had significantly increased compressive strength in acid water (1.7–15.4%) . Similar2 and KOH); (2) form precipitations of minerals and filling the voids. The latter mechanism presents a positive impact on the compression strength of the concrete in short-term tests, based on the findings of the current study. However, long-term tests are necessary to evaluate the long-term change of the compressive strength of the concrete.The stress-strain curves of concrete presented a similar pattern before and after the immersion tests, and the strains (0.15–0.16%) to reach the maximum compressive strength were identical b. The imThis study evaluated the effect of the acid discharge from the weathering of black shale on the strength of concrete. Immersion tests were conducted at different immersion depths of the black shale to evaluate the oxidation conduction under partially saturated conditions. Concrete specimens were placed in the same water tank and directly contacted the acid discharge from the black shale. The oxidation products in the water and precipitation were quantified and calculated through water chemistry and mineral composition analysis during and after the immersion tests. The ultrasonic wave velocity and uniaxial compressive strength were obtained before and after the immersion by testing to evaluate the quality and strength of the black shale and concrete specimens.42−, and Fe, in the immersion solution. This observation was likely due to the oxidation and mass transfer in the capillary zone in black shale. Additionally, the oxidation and dissolution of minerals reduced the compressive strength of black shale.Under the partially saturated condition, the oxidation of sulphide minerals in the black shale, i.e., pyrite in this study, depended on the immersion depth. Lower immersion depth of the black shale led to a higher degree of oxidation with lower pH, higher EC, and more abundant weathering products, such as SOThe acid discharge from the black shale showed a negative impact on the quality and entirety of the concrete in the immersed zone, but presented a positive impact on the non-immersed zone. The ultrasonic velocity of the concrete decreased in the immersed zone, which was due to the dissolution-induced reduction of concrete quality and entirety. However, the ultrasonic velocity of the concrete increased in the non-immersed zone. This phenomenon attributes to the mineral precipitation and hydration that occurred in the non-immersed or partially-immersed zones.In the testing period of the current study, the compressive strength of the concrete enhanced after contacting the acid discharge from the black shale. This phenomenon is attributed to the filling of the voids by the precipitations, such as goethite and anhydrite. However, a long-term test is needed in the future to evaluate the long-term impact of acid discharge on the compressive strength of the concrete.Based on the results of this study, the following conclusions can be drawn from this research:


Reinforced concrete structures are prone to cracking. The development of cementitious matrices with the capacity for self-healing soon after these cracks appear represents savings with inspections and repairs of the structures. Self-healing can be stimulated with the use of crystalline admixtures. Such materials easily react with water and increase the density of C-S-H , forming insoluble deposits blocking existing pores and cracks. In this research, self-healing in concrete cracks was evaluated using three different crystalline admixtures, submitted to two and six wetting–drying cycles. The efficiency of self-healing was evaluated by optical microscopy and using the chloride diffusion test, which allowed calculating the predicted useful life of the concretes. The results highlight two important findings: (i) in optical microscopy, crystalline admixtures were not efficient in promoting self-healing on the surface of cracks in any of the studied concretes; (ii) the passage of chlorides by diffusion was lower for concretes with crystalline admixtures compared to the reference, showing better internal healing of these materials and, consequently, greater prediction of the concrete’s useful life. Concrete is a material widely used around the world in various construction techniques. Its purpose is to resist the efforts of compressive forces and protect the reinforcement from aggressive environmental agents, such as chlorides. Although it has been used for many years and has undergone several improvements, this cementitious material is susceptible to different sources of degradation, which can considerably compromise the durability of structures . Among tWhen exposed to the environment, reinforced concrete structures require periodic inspections to observe and monitor the presence of cracks and their geometries. Depending on the conditions and the location in which the structure is located, carrying out inspections may be difficult or impractical, in addition to the fact that such inspections and possible repairs require a high investment ,4,5. To 3 occurs with the crack [In this sense, the self-healing of cementitious materials has been the focus of several studies ,7,8. Thihe crack .Autogenous self-healing in concretes can be stimulated using commercial products, such as crystalline admixtures, inserted in the cementitious matrix during its production ,11. CrysThe chemical composition of crystalline admixtures is formed by Portland cement, filler, pozzolans, sand, slag, siliceous powder, and “active chemicals” ,13,14. DxRx) reacts with C3S and water, producing modified C-S-H and a precipitated pore blocker (MxCaRx) in existing microcracks and capillaries [The reaction of crystalline admixtures with cementitious compounds occurs according to Equation (1). The crystalline promoter  and six cycles (84 days) of wetting and drying to intensify the self-healing ability. The crack thickness measurements were performed at 3 days and at the end of each wetting and drying cycle, using an optical microscope. After the wetting and drying cycles, the cracked samples were subjected to the natural chloride diffusion test, with no potential difference applied, to simulate a real condition of exposure to the concretes. Through the chloride diffusion test, it was possible to forecast the service life of cracked concretes. The work made it possible to conclude the self-healing ability of cracks in concrete with crystalline admixtures and to compare the effects of these materials with the reference concrete.The cement used in this research was Portland cement composed with filler (CP II-F 40) , according to NBR 11578 , equivalThe aggregates were characterized according to sieve analysis by NBR NM 248 , while N3. The fine aggregate used was quartz sand, whose particles have a fineness modulus of 1.89. The mass specific gravity of the sand is 2.54 g/cm3. Basalt  was used as coarse aggregate, with a mass specific gravity of 3.01 g/cmThe superplasticizer additive  was used to maintain the established slump of 220 ± 20 mm, according to NBR NM 67 . This liThree different powder crystalline admixtures available on the market, called X, Y, and Z, were used. The water used in this study for molding the specimens came from the public supply of the city of Porto Alegre, Rio Grande do Sul, Brazil.To achieve the objectives proposed in this research, the experimental program presented in The proportions of each material used are described in Cylindrical specimens with dimensions of 100 mm in diameter by 200 mm in height were molded for the test of resistance to axial compression and water absorption by capillarity, and samples of 95 mm in diameter by 190 mm in height were used for the test optical microscopy and chloride diffusion. The specimens were cut for the chloride diffusion test and optical microscopy, with the5 cm thick upper and lower slices being discarded. For the chloride diffusion test, only central slices of 3 cm thickness each were used.For the creation of cracks, the specimens (3 cm thick) were positioned on the press, according to NBR 7222 , which eAfter creating the cracks, wetting and drying cycles were performed for 28 days (two cycles) and 84 days (six cycles) in the chloride diffusion test samples; one cycle corresponds to 2 days of wetting and 14 days of drying. The water used for the immersion cycles came from the public supply network, renewed at each new cycle. A simple compressive test, recommended by the NBR 5739 , was useA capillarity water absorption test was performed according to NBR 9779  at 28 anEach specimen’s crack width was measured using an optical microscope   on the crack surface. The crack thickness measurement was performed at 3 days, for the selection of cracks with thicknesses less than 0.4 mm, and at the end of the wetting–drying cycles. For each concrete, six cracked specimens were chosen, three for each age of the chloride diffusion test (28 and 84 days). For the images to always be generated in the same place at different ages, 10 zones of 0.6 mm were demarcated in the sample’s central region (95 mm in diameter), discounting the 35 mm of the edges. From each sample for each age, 10 images were always generated in the same place.Through the images generated, the healing efficiency of the crack could be assessed. The cure rate was calculated using Equation (2).The chloride diffusion test was used to verify the internal self-healing of cracks, carried out according to UNE 83987 . To simuThe samples were collected in a cell with deionized water to check the chloride passage through the concretes over time. To perform the readings and determine the chloride content, the Hanna Instruments HI 98191 equipment  and the selective ion electrode HI 4007, from the same manufacturer, were used.Ccl is the chloride concentration at depth x and time t (mg/L), Co is the initial concentration of chlorides within the structural component, Cs is the chloride concentration on the surface of the concrete structural component, taken as constant (mg/L), erf is the Gauss error function, x is the depth considered (cm), D is the chloride diffusion coefficient (cm2/s), and t is the length of time considered (s).For the calculation of the diffusion coefficient of chlorides and prediction of useful life, Equation (3), from Fick’s second law, was used.The results of the compressive strength test of the specimens are shown in By analyzing Pazderka and Hájková  did not For the age of 91 days, it can be noted that the concretes containing the crystalline admixtures showed less resistance in the compressive test when compared to the reference. Likewise, Helene et al.  demonstrTo study the significance of controllable variables, a variance analysis (ANOVA) was carried out with factors using the software Statistica 13 . The results are shown in It can be seen that the influence of the controllable variables used was considered statistically significant. Thus, the use of crystalline admixtures and the increase in age of the concrete made a difference regarding the results of compressive strength.The results obtained in the capillarity water absorption test are shown in The capillarity water absorption mechanism is not only influenced by the characteristics of the liquid, such as density, surface tension, and viscosity, but also depends on the characteristics of the concrete, such as tortuosity, radius, and communication between the capillary pores; the absorption of water is more intense with a smaller diameter of the capillary pores and their connections .Thus, the greater water absorption by capillarity observed in the reference for both ages may be related to the cement used in the present study. CPII-F cement has filler in its composition, a material that is considered to have similar inertness and fineness to cement, acting in the densification of the concrete matrix, causing a reduction in the size of the capillary pores, which in turn increases absorption.Regarding the effect provided by crystalline admixtures, it is possible to observe a reduction in the absorption of water by capillarity in concretes with these materials. At 28 days compared to the reference, concretes with additives X, Y, and Z showed a reduction of 7%, 41%, and 13%, respectively.At 91 days, a more considerable effect was observed using these materials, where the reduction in absorption was 24%, 43%, and 31%, respectively, for the crystalline admixtures X, Y, and Z. It is also possible to notice that there was no reduction in absorption from 28 to 91 days in the reference concrete, indicating that the reduction in absorption perceived in other concretes was mainly due to the effect of the crystalline admixtures used.In the study by Joa et al. , 3% crysTo study the significance of controllable variables, a variance analysis (ANOVA) was carried out with the software Statistica 13. The results for the capillarity water absorption are shown in At 3 days, the crack thickness was measured on its surface, and images of the samples were collected using an optical microscope. Subsequently, after the wet–dry cycles, new images of the samples were collected to assess the crack self-healing rate. The test was performed on the same specimens used for the chloride diffusion test. The evolution of the self-healing of all evaluated samples is shown in Analyzing the results presented in One reason for this increase in the rates of self-healing of cracks was the methodology for quantifying the thicknesses per pixel, using the ImageJ software. As explained in Over time and with the application of the wetting/drying cycles, these remnants were removed, and an increase in the rate of self-healing was observed, leading to an increase in the crack region. In this way, to be perceived, the self-healing of a crack would need to be superior to the loose fines generated when cutting the specimens. However, this would not be perceived using optical microscopy if the samples were not cut and were molded directly into the dimensions required for testing .With crystalline admixtures, more significant self-healing was expected in most samples, including for greater crack thicknesses. However, a factor considered influential in this low formation of healing products was the lack of moisture, since the concretes were exposed to predominantly dry conditions, where each cycle was formed by only 2 days of wetting and 14 days of drying ,12,43. OGiven the above, it can be seen that, superficially, the self-healing of cracks was not observed. This result is related to the cracking methodology applied, which was not efficient in this work, as well as to the short wetting period that the concretes with crystalline admixtures were exposed to in the wetting/drying cycles.As already mentioned, superficially, it was impossible to observe any point of self-healing of the cracks in all evaluated concretes. However, through optical microscopy, this behavior could not be confirmed for their internal region. The results showing the internal behavior of self-healing of cracks are presented below.The chloride diffusion test was used to check the internal self-healing of cracks. This test started after two and six cycles of wetting and drying, with three cracked samples of each concrete, i.e., the same samples being used in optical microscopy. It can be observed that, among the crystalline admixtures, X and Z presented the lowest chloride passage over time. The crystalline admixture Y had the worst result during the test, with a more significant passage of chlorides over time, showing itself to be inferior even to the performance of the reference concrete. This result presented by the crystalline admixture Y may be related to its greater granulometry, thereby delaying the hydration reactions of this material before the start of the diffusion test . Concretes with crystalline admixtures X and Z showed a reduction of 35.55% and 58.53%, respectively, in relation to the reference, while the crystalline admixture Y showed an increase in this passage over time by 52.44%. In this sense, Borg et al.  evaluateAnalyzing However, as can be seen, all crystalline admixtures provided a reduction in the passage of chlorides. That is, they acted in reducing the internal thickness of the crack. In this sense, Huang  found thJacobsen, Marchand, and Boisvert  verifiedAs previously mentioned, the wetting and drying cycles were not fully effective in causing the cracks to close, mainly due to the short wetting period that the specimens were exposed to. However, after these cycles, the direct contact of concretes containing crystalline admixtures with the water during the diffusion test may have positively influenced the reduction of the passage of chloride ions from the continuous hydration reaction of the crystalline admixtures with the water of the test. This is in line with the results observed by Borg et al. , who verThe crack internal morphology is another factor that may have contributed to the greater or lesser passage of chlorides. The cracked specimens used in this work were selected by image analysis; thus, only the crack’s external surface and not its internal configuration was known. According to Roig-Flores et al. , a crackFrom the chloride diffusion test and Equation (3) describing Fick’s second law, it was possible to calculate the chloride diffusion coefficient for each studied concrete, a parameter that characterizes the concrete’s resistance to the passage of chlorides. Thus, through Analyzing Azarsa, Gupta, and Biparva  investigAnalysis of variance (ANOVA) was performed with the software Statistica 13. The results of the diffusion coefficients are shown in The predicted useful life of concrete structures corresponds to the period that chlorides take to pass through the concrete covering layer until they reach to and dissipate in the reinforcement, which can start corrosion. Therefore, the prediction of useful life is totally influenced by the diffusion coefficient. A higher diffusion coefficient suggests a lower resistance of the concrete to the passage of chlorides and, consequently, a lower calculated useful life.Thus, through the diffusion coefficients found for the concretes, the useful life was forecast using Equation (3), with the results shown in Considering the 4 cm coverage recommended by the NBR 6118 , the refIt can be noted that the reference concrete had a useful life forecast of 17.6 years. A better result was noted for concrete with crystalline admixture X (37 years), while concretes with crystalline admixtures Y and Z showed similar performance (approximately 28 years), with a gain of 57% in the time before reaching the reinforcement.Thus, it can be observed that the use of crystalline admixtures provided a reduction in the passage of chlorides through the concretes during the diffusion test and, consequently, to an extension of the time until these aggressive agents would reach the reinforcement, thereby causing the corrosion to start. It is worth mentioning that the results presented refer to cracked concretes, which allow a more accelerated movement of chlorides through the interior of the cementitious matrix and, as a result, less time for depassivation of the reinforcement.From the optical microscopy test, it was observed that the wetting and drying cycles were not efficient in activating the hydration reactions of crystalline admixtures on the sample surface. Thus, they did not provide complete crack sealing due to the short wetting period that the concretes were exposed to.The analysis and quantification of images by optical microscopy was not able to efficiently detect the self-healing of concretes, mainly due to the presence of loose fragments of mortar present on the crack surface due to the cutting procedure of concrete samples.From the chloride diffusion test, it was possible to internally observe the performance of crystalline admixtures and the wetting/drying cycles in the closing of cracks and the reduction of the passage of chlorides in comparison to the reference concrete.The chloride diffusion test proved to be feasible for detecting self-healing in cracked samples. At the different ages of the test (after two and six wetting/drying cycles), it was possible to observe that the crystalline admixtures delayed the passage of chlorides over time with respect to the reference concrete.The concretes with crystalline admixtures showed an increase in the useful life forecast compared to the reference concrete at the two evaluated ages, with the exception of the concrete with crystalline admixture Y when the diffusion test started at 28 days.Regarding the performance of crystalline admixtures, concretes with crystalline admixtures X and Z showed a reduction in chloride passage with respect to the reference concrete, considering the two ages of the chloride diffusion test. Concrete with crystalline admixture Y only showed this reduction after six cycles of wetting and drying.From the results, it was possible to observe that the internal self-healing behavior of a crack can differ from the behavior observed in the outer region. Thus, a precipitous conclusion of self-healing cannot be reached on the basis of the crack’s surface, as the internal behavior can be quite different.This study explored the effects of using crystalline admixtures on the self-healing of cracks in concrete. We reached the following conclusions from the results:


Many older bridges feature capacity deficiencies. This is mainly due to changes in code provisions which came along with stricter design rules and increasing traffic, leading to higher loads on the structure. To address capacity deficiencies of bridges, refined structural analyses with more detailed design approaches can be applied. If bridge assessment does not provide sufficient capacity, strengthening can be a pertinent solution to extend the bridge’s service lifetime. For numerous cases, applying an extra layer of textile-reinforced concrete (TRC) can be a convenient method to achieve the required resistance. Here, carbon fibre-reinforced polymer reinforcement together with a high-performance mortar was used within the scope of developing a strengthening layer for bridge deck slabs, called SMART-DECK. Due to the high tensile strength of the carbon and its resistance to corrosion, a thin layer with high strength and low additional dead load can be realised. While the strengthening effect of TRC for slabs under flexural loading has already been investigated several times, the presented test programme also covered increase in shear capacity, which is the other crucial failure mode to be considered in design. A total of 14 large-scale tests on TRC-strengthened slab segments were tested under static and cyclic loading. The experimental study revealed high increases in capacity for both bending and shear failure. Thus, the ecological footprint of concrete structures might be improved.The age distribution of the existing bridges in combination with several normative changes and significant economic and demographic changes in many industrial countries lead to many structures showing damages. Or else, there are computational deficits due to increased traffic or stricter verification ,4,5,6,7.The findings presented in the following were part of a project aiming at developing a thin TRC layer which is intended to be added on bridge deck slabs between the RC structure and the road surface. It is called SMART-DECK and offers a three-fold functionality comprising monitoring, corrosion protection and strengthening of the transverse system of concrete T-beam or hollow core bridges. Strengthening is subject to the present paper. In terms of the gain in capacity due to the additional TRC layer, not only regular flexural and but also shear tests were conducted. The results of the experimental investigations are presented later. Prior to the presentation of the conducted investigations, the concept of the strengthening layer is described in The aim of the study is outlined in detail in Sonderforschungsbereich, SFB) 528 at TU Dresden, Germany, on strengthening of existing structures [Construction with reinforced concrete is rather economical and characterised by its versatile shaping. The two main elements—concrete and steel reinforcement—are combined to exploit their full potential when interacting with each other. One main disadvantage is the predisposition of the steel reinforcement for corrosion. If the concrete surface is damaged or chlorides enter the structure, the reinforcement can be damaged despite sufficient concrete cover. For this reason, research is concerned with the development of corrosion-resistant reinforcement elements. In the last two decades, research on corrosion-resistant textile reinforcements has been intensified. Early applications from Japan on non-metallic carbon mesh reinforcement  inspiredructures ,28,29,30ructures ,33,34,35The reinforcement in TRC is comprised of continuous fibres, which are called filaments . These aAlkali-resistant (AR) glass fibres and carbon fibres are preferably used for TRC. Both materials have good mechanical properties, but carbon fibres are more durable than AR glass fibres . Carbon Bond of non-impregnated textiles is achieved by adhesion and friction rather than mechanical interlock, which is the typical mechanism for conventional deformed steel rebar. Due to the circular shape of the filaments and their small diameter, small voids exist in the roving. Because of their small size, cementitious binder cannot penetrate the roving and only encloses the edge filaments. The core filaments can only be activated for load transfer by friction on the edge filaments. Due to the smooth surface of the fibres, this bonding mechanism is ineffective and results in a telescopic failure with a stress gradient over the cross-section. An impregnation with low-viscosity organic or mineral binders fills the voids and allows for simultaneous activation of the core and sleeve material ,38. The The system SMART-DECK presented here was developed in a research project in cooperation with a total of seven project partners from research and building practice as well as administration and material production. It is added to the top of the bridge between the concrete slab and the road surface  and enabAnother research question was the manufacturability of SMART-DECK. A common method for TRC production is shotcreting ,58,59. SSMART-DECK is a supplementary TRC layer, which is applied on top of the existing concrete and subsequently covered by the road surface . It is tThe bond between strengthening layer and existing concrete in this system is not achieved by mechanical connectors but relies on concrete-to-mortar adhesion. This greatly reduces application time and cost but requires proper surface preparation prior to casting as well as a close quality control on site. The basic material carbon of the TRC layer offers the electrical conductivity required for monitoring and pCCP on the one hand. On the other hand, in combination with epoxy resin impregnation, it has good bonding properties to the surrounding concrete and is very efficient due to its high axial tensile strength . The corrosion resistance of the material allows the execution of thin layers with small concrete covers. Especially in combination with a massive existing supporting structure, which provides high stiffness, these advantageous properties of TRC can be used optimally and high increases in load-bearing capacity can be achieved with a minimum use of material.As stated before, the flexural strength of regular RC components with small longitudinal reinforcement ratios can be significantly increased by TRC strengthening in the flexural tension zone ,61,62,63Prior to the start of the project, tests were conducted to estimate whether promising degrees of strengthening for the main failure modes in transverse direction of the bridge can be achieved in the ultimate limit state . It was 2 was built which also met the demands resulting from the other two intended functionalities. It featured a height of h = 28 cm and a change of slope was produced to represent realistic conditions for fabrication with respect to an existing bridge slab. The additional TRC layer was applied to 80% of the area, whereby the implementation of the cross-sectional supplement itself and the manufacturing of the measuring device for the monitoring system were tested. Subsequently, the monitoring system (see above) and the achievable increases in capacity were investigated. The latter was done by extracting saw-cuts from the strengthened and non-strengthened areas of the demonstrator slab, which were then tested in a total of eight load tests at IMB until failure. Bending and shear were investigated in the same way as in the series of tests presented here: 24–56% shear strengthening and 90–174% flexural strengthening were achieved [The strengthening effect of SMART-DECK itself was already experimentally examined during realisation of the project demonstrator. For this purpose, a slab of approximately 100 machieved .W × H × L = 40 × 40 × 160 (mm) in accordance with Reference [Material and small-scale tests were carried out to characterise the materials intended for SMART-DECK and their interaction with each other. The goal was to select a suitable combination of mortar and textiles for strengthening  was either 21 or 38 mm. Depending on the knitting method, different bond properties can occur which not only differ among the various grids but also depend on the direction [X: test type Y: applied mortar Z: applied textile With the findings from the small-body tests, in which various parameter combinations were investigated, the materials for the final SMART-DECK system were pre-selected. This optimised combination was then used as a strengthening layer in the large-scale tests. Small-body tests are particularly suitable for this purpose, as multiple repetitions with the same combination of properties and a large number of different specimens can be tested in a comparatively short time. The tests were labelled X-YZ based on the type of experiment and the materials used as follows:For some tests, another abbreviation was added to the end in order to mark a more specific property. Due to the production process, the weft direction of the textiles is limited to the width of the textile machines. For this reason, the weft direction is positioned in longitudinal direction and the warp direction in transverse direction of the bridge (main load transfer direction of the roadway slab) since separated segments of textile are required in longitudinal direction by means of electrically insulated areas . While tFor test preparation, the fibre strands were extracted from the grid approximately at the centre between two strands (10–15 mm from the stand axis). The textiles have comparatively large yarn cross-sections. At the same time, carbon filaments have high strengths, so high failure loads had to be assumed, which required high lateral compression in the clamps at the ends of the yarns. To prevent them from rupturing in the clamps, the ends were glued into aluminium foil with the aid of epoxy resin mortar. These straps were fixed between the jaws of the clamps after curing.Only results from tests were considered where the yarn actually ruptured within the free length. Loading was applied displacement-controlled at 1 mm/min. Meanwhile, the applied tensile force and the strain were recorded. The results differ with regard to the test length (free length between the clamps). Since the probability of imperfections increases with increasing length of investigation, its influence should be checked. For T-1-38, no negative influence due to increasing test length is evident. Only in weft direction, slightly smaller stresses do occur at the largest test length compared to the medium test length. Instead, the tests on the weft yarns of T-2-21 show increasing ultimate stresses with longer test length. Only in warp direction of T-2-21, a decreasing trend is visible, whereby the tests with medium lengths showed comparatively low tensile strengths. Overall, the ultimate stresses of T-1-38 are somewhat lower than those of T-2-21 and the fibre strands in the weft direction have higher tensile strengths than those in the warp direction, which is due to the negative influence of the knitting thread and is commonly known ,68.As mentioned before, the composite system was tested in small-body tests under bending and uniaxial tension , step IIThe textiles were placed in concrete over a total length of 1000 mm. For the flexural test, the TRC strips were supported over a span of 900 mm, with support overhangs of 50 mm at both ends. The test set-up was a 4-point bending test with centre distances of 300 mm in relation to the position of the supports and load application points. Large deflections occurred (100 to 130 mm in the middle of the span at ultimate load), which correspond to five to six times the depth of the test specimen. Failure always occurred via a propagating crack by spalling of the concrete compression zone without rupture of the textile. As the reinforcement did not fail and due to second-order effects , the results of the bending tests were not taken into account in the evaluations and only uniaxial tensile tests were used in the further investigations of the composite load-bearing behaviour.l/d (here: l/d = 90). In this case, the tensile test setup does provide convenient results.Further development of the uniaxial tensile test setup  minimiseSeries 1: manufacturing method → half the specimens were regularly cast  or one layer as in the description above (indication 20).Series 3: water-to-cement ratio of the mortar.A total of five test series was investigated with their main parameters depending on the progress and open questions regarding the efforts of the project partners to develop advanced materials that meet all, and sometimes contradictory demands resulting from the different targeted functions of SMART-DECK . While all tensile tests aimed at receiving essential insights on mortar to reinforcement combination, each series also aimed at defining another parameter, like, for instance, the following:Those and the other tensile tests that are not shown in detail here, were conducted to characterise the properties in the warp direction, which is decisive for the strengthening effect in the present case. The specimen length was 1000 mm, and the anchor length at each end was 250 mm. Due to the specified layered structure of SMART-DECK with a concrete cover of 10 mm, the concrete cover of the tensile strips was also limited and not optimised regarding maximisation bond or maximum tensile stress development. Therefore, it was expected that a full exploitation of the material’s potential might not succeed, which was confirmed by the tests. After completion of the crack formation transverse to the load direction, longitudinal cracks often formed in the textile plane. Failure of the fibre strands occurred abruptly and was accompanied by concrete spalling. In some cases, there was no or only partial spalling. In these cases, however, the matrix clods were no longer bonded to the textile. The fibre strands in tensile direction either ruptured or remained partially intact. Since the specimens that were concreted by means of pouring and compacting a featureIn the first two mortars tested, the fibre strands generally failed smoothly. In the more advanced mortars, they were mostly frayed. An improvement in the bond properties was achieved by further development of the textiles (T-4-38). The highest failure stresses, and at the same time the smallest dispersion, were obtained in tests with sanded textiles of T-4-38 in combination with M-4-04 g. Howevel = 1.0% can be referred to [For investigation of the strengthening effect of SMART-DECK, a total of 17 results from component tests are available, as the overview in erred to . The aima = 0.7/1.0/1.3 m between load and support was modified and to additionally vary the exploitation of the flexural reinforcement, the longitudinal reinforcement ratio was set to either ρl,s = 1.0/0.5/0.2% in terms of the steel in the existing slab. For the high and medium longitudinal reinforcement ratio, threaded steel bars with a strength class of St900/1000 (Ø15) were used, and for the small longitudinal reinforcement ratio, a ribbed steel of B500 quality (Ø10) was used. The reinforcement layout of the reinforced concrete slab segments is shown in To control the bending moment, the load distance b = 50 cm, while the load plate’s widths were 40 mm to involve the entire cross-section in load transfer. No significant impact was expected by the additional TRC layer on stress redistribution in the slab originating from the concentrated load. In the near past, the influence of the slab width was extensively investigated for reinforced concrete slabs [No shear reinforcement was provided in the shear spans, as its installation in slabs is costly and therefore unusual in trunk road bridge slabs for practical reasons. A longitudinal reinforcement of Ø10/20 in transverse direction to the load transfer direction of the test bodies  was provided in accordance with the normative minimum value for bridge slabs. The height of the RC base specimens was 28 cm, and the concrete cover was 20 mm all around. All slab segments were designed with a width of te slabs ,73,74,75dg = 16 mm. The specimens were compacted by means of an internal vibrator. Material samples (cylinder Ø = 150 mm/h = 300 mm and cubes with an edge length of 150 mm) were produced, which were stored next to the slab segments and tested at the time of the component test in order to be able to draw conclusions about the developed concrete strengths of the slab specimens (Rt = 1.0 mm was determined (three measurements per slab segment). SMART-DECK was manufactured by the project partner Eurovia under construction site conditions.The reinforced concrete base bodies were concreted indoors with a ready-mixed concrete featuring a target strength corresponding to a C30/37 and a maximum aggregate size pecimens . Prior tSpecimens S4, S5, S6, S7 and S8 were produced together and strengthened some weeks later at once. They had the same material combination in the TRC layer. The specimen which was used for tests S2-1 and S2-2 was manufactured at an earlier stage with the material combination then available.ia (load axis to axis of the support close to the load), was varied according to the specifications in Two separate tests were carried out on each specimen . The loaAll tests were statically loaded with stepwise increments until failure, except S8-1 and S8-2, which were loaded cyclically. The first four load stages were introduced load-controlled. From about half of the expected failure load, the load was applied deformation-controlled.In some tests, there were production-related imperfections in the interface between old and new concrete. Therefore, the TRC layer was partially detached from the existing concrete during the tests. However, these delaminations only occurred in the concrete interface and always originated from pre-existing imperfections. In case of intact interfaces, the load did not cause the joint to open, which could already be observed in previous tests .Based on the crack patterns, the tests can essentially be divided into three groups, differentiated by primary cracking that introduced failure, or could be observed at the time when ultimate load was reached . FlexuraWith a few exceptions, activation of the carbon concrete supplement could be achieved in the tests presented here, as shown in the previous section. However, the findings from manufacturing the strengthening layer for the specimens of this experimental programme provided crucial indications for the further development of the mortar and the production methods. In subsequent applications , unimpaiia, and the longitudinal reinforcement ratio, ρl,s, referring to the steel reinforcement. Depending on the load distance and the flexural reinforcement, the ranges of abscissa and ordinate were adjusted, which should be kept in mind while comparing the results. The strengthened specimens (solid curves) show less deflection than the plain RC specimens (dashed curves) at the same load level. The deflections, w, were measured continuously by means of displacement transducers beneath the specimens in the load axis.In addition to crack formation, SMART-DECK influences the load-deflection behaviour of the slab segments . Just as in the static tests, the load was applied stepwise. Subsequently, about 80,000 load cycles with an amplitude of 10 kN were applied at a frequency of f = 5.243 Hz. The upper load was 120 kN (maximum peak load) and the lower load 100 kN (minimum peak load). This load range corresponds to about 12.5% of the ultimate load of the RC reference specimen. Hardly any stress changes in the reinforcement were measured and there was no significant change in the crack pattern. Therefore, the amplitude was doubled while maintaining the upper load at 120 kN and approximately 0.5 × 106 load cycles with a doubled load oscillation width were applied (lower load: 80 kN). In the meantime, the interface between the existing slab and the strengthening layer opened up, starting from the aforementioned imperfection that already existed before the start of the test. Nevertheless, no increase in the strain of the reinforcement and the concrete compression zone could be observed, which is why an increase in the average load was targeted.To investigate the influence of predominantly cyclic loads due to the impact of traffic, two tests were carried out under load collectives . The specimen was prised open after the test to reveal the steel reinforcement in the support section of the cantilever. Slight confinement was visible which was much less distinct as in specimen S6  is intended to provide a monitoring system, preventive cathodic corrosion protection if necessary and the possibility to enhance the deck slab’s flexural and shear capacity in transverse direction of T-beam or hollow-core concrete bridges.An experimental campaign was introduced comprising small- and large-scale tests. The small tests were conducted using TRC samples to investigate the interaction between suitable high-performance mortars and potential textile reinforcement materials aiming at material refinement and selection of proper materials and characterising its properties. The large-scale tests were conducted on slab specimens strengthened using SMART-DECK. They were partly statically or cyclically loaded until failure.their longitudinal reinforcement ratio  andthe bending moment-to-shear force ratio.The outline of the specimens was varied by means ofAn activation of the carbon concrete strengthening for existing slabs which feature shear failure allows strengthening degrees of 30–50%.In case of high bending loads on the existing slab, SMART-DECK can lead to an increase of the flexural capacity of 2.3 to 2.9 times the capacity of the non-strengthened RC member.In some cases, a shift from flexural to shear failure was observed by means of SMART-DECK. This corresponds to the maximum flexural strengthening of the referred RC component.Therefore, load cases’ bending and shear could be addressed in twelve static and cyclic tests on strengthened specimens. A comparison to test results gained from non-strengthened reference specimens showed that SMART-DECK can enable high increases in capacity:The results demonstrate the high potential of carbon concrete strengthening for ULS load cases in bridge deck slab design. Additionally, the fine crack pattern at the tensile side of the slab also resulted in significant advantages regarding serviceability.For verification purposes, further investigations should be carried out, with the focus on fatigue loading with alternating loads and higher amplitudes typical for bridges. Further test results provide the basis for generalised design approaches which not only quantify the flexural but also the shear and fatigue strength.


In the present study, the influence of thermally induced damage of reinforced concrete (RC) frames on their static and dynamic response is experimentally and numerically investigated. In the experimental test, the RC frame is first pre-damaged through fire exposure and then loaded from the side with the impact of a steel pendulum. To verify the recently developed coupled thermo-mechanical model for concrete, transient 3D FE simulation is carried out. The rate and temperature-dependent microplane model is used as a constitutive law for concrete. It is first shown that the simulation is able to realistically replicate the experimental test. Subsequently, the numerical parametric study is performed where the dynamic and static response of RC frame is simulated for both hot and cold states. It is shown that the pre-damage of RC frame through fire exposure significantly reduces the resistance and changes the response. Finally, it is demonstrated that for the impact load the rate sensitive constitutive law of concrete significantly contributes to the response of RC frame. Reinforced concrete structures exposed to extreme loading conditions such as fire, impact, blast, earthquake, industrial accidents or their combination is in recent years becoming a more relevant topic of research. Such loading scenarios are characterized with high loading rates, often related with fire outbreak, exposing structures to extremely complex conditions, which can lead to strong and fast degradation of mechanical and physical material properties and failure of structures. Therefore, to make structures more resistant on extreme loading conditions, it is important to investigate the behavior of materials and structures exposed to such extreme loads. In the literature, a large number of studies are available for concrete loaded under high loading rates at ambient temperature and even more on thermally exposed concrete structures. However, there is a relatively low number of studies for the structures that are exposed to combined loading, e.g., impact after fire ,3,4,5,6.The behavior of concrete that was exposed to high temperature changes significantly. Its mechanical properties, e.g., strength and modulus of elasticity, decrease. At thermal loading there are temperature gradients, which lead to thermally induced stresses. The boundary conditions can prevent deformation due to thermal strains, which cause thermally induced stresses and damage. The load induced thermal strains  and relaxation can also strongly influence the structural behavior ,9,10,11.The influence of loading rate on the behavior of quasi-brittle materials and structures has been intensively studied and better understood in recent years ,29,30,31When the concrete is before mechanical loading pre-damaged through thermal loading , there is a significant decrease of mechanical properties, at structural level there is additional damage of concrete due to thermally induced stresses. Recently, it has been demonstrated that through high temperature pre-damaged concrete is less sensitive on the influence of high strain rates . TherefoThe organization of the manuscript is as follows. In the following section, the numerical model, geometry, material properties and loading scenarios are presented. To verify the numerical model, the results of experimental test on one thermally pre-damaged RC frame are compared with the results of the numerical simulation. Subsequently, the results of parametric study are presented and discussed. Finally, the role of rate dependent constitutive law and structural inertia in dynamic (impact) and static analysis of RC frame is investigated and concluding remarks are given.in (see ijε (kinematic constraint). On the microplane, considered normal are  and two shear stress-strain components . To realistically model concrete, the normal microplane stress and strain components are decomposed into volumetric and deviatoric parts . Unlike most microplane formulations for concrete, which are based on the kinematic constraint approach, to prevent unrealistic model response for dominant tension , kinematic constraint is relaxed [S denotes the surface of the unit radius sphere and ijδ is Kronecker delta.The rate and temperature dependent microplane model is used to model concrete ,35. Mostni see . Micropl relaxed , i.e., bc0 and c2 are material rate constants, which have to be calibrated by fitting test data, crs is assumed spacing of micro-cracks, and The microplane model accounts for the two abovementioned strain rate dependent effects: (i) the rate dependency due to the formation (propagation) of micro-cracks that is the effect of inertia at the level of the micro-crack tip, and (ii) the rate dependency coming from the viscous properties of concrete between micro-cracks. For each microplane component, the rate effect is defined according to the rate process theory :(2)σM(εMormed in .The rate sensitivity of concrete (Equation (2)) is assumed to be independent of the thermally induced damage. However, the inertia effects, which have significant influence on dynamic response of concrete, are automatically accounted for through dynamic FE analysis. As mentioned above, after concrete is damaged due to fire exposure the inertia effects become less pronounced .T is the temperature, T that comes from thermal finite element analysis. However, such approach in quasi-brittle materials such as concrete, which exhibit fracture and damage phenomena, can cause strong localization of thermally induced damage and consequently mesh dependent results. As will be discussed on the numerical example below, this is especially true in dynamic analyses, where the thermally induced damage in the impact zone together with mechanical damage can lead to nonobjective and too strong degradation of structural resistance.In the here employed thermo-mechanical model for concrete, the total strain tensor consists of three components: mechanical strain, free thermal strain, and load induced thermal strain:ependent ,16,17. UT inside representative volume RV:α = nonlocal weighting function, x = coordinate of the averaging point, and s = coordinate of the contributing point. The adopted nonlocal weighting function is the modified Gauss distribution function . Note that if the size of the finite elements are significantly larger that the characteristic length or if the temperature field is homogeneous, the nonlocal and local temperatures are the same. Furthermore, free thermal strains and load induced thermal strains are also calculated based on nonlocal temperature, i.e., in Equation (3) T is replaced with To make the analysis more objective in this respect, an approach in which the thermally dependent mechanical properties of concrete are calculated based on the nonlocal (average) temperature is proposed here. Similarly to the nonlocal strain approach ,37, the function :(5)α(r)=Thermo-mechanical model for steel is formulated in the framework of classical rate theory of plasticity. It is based on the von-Mises yield criteria, isotropic hardening and associated flow rule. Its mechanical properties, i.e., Young’s modulus, yield stress and strength, as well as thermal properties  depend on temperature ,16,17 acSteel is almost rate insensitive, however, if it is loaded under high loading rates; after threshold strain rate the resistance (apparent strength) starts to increase progressively. The reason is that the non-linear response of steel (strain hardening) that generates strong inertia induced resistance . This efThe finite element analysis consists of two parts: (i) transient thermo-mechanical and (ii) dynamic analysis. The spatial discretization is performed using standard 3D solid finite elements. Thermal transient analysis is performed using direct integration scheme of implicit type ,15,16,40The experimental tests to investigate the effect of combined thermo-dynamic load on RC frames were carried out at Bhabha Atomic Research Center (BARC) in Mumbai, India . In the ykf = 415 MPa. The RC frame structure was fixed on the four contact-point pendulum facility. In the absence of anchorage bars, a supporting structure was made to anchor the frame . The FE discretization of the complete RC structure is shown in As mentioned before, the frame was first exposed to fire, cooled down to ambient temperature, and subsequently laterally loaded with a side impact of pendulum. The fire load was applied following the fire scenario according to the ISO 834 curve  for the All of the surfaces except the top slab surface and the four footings, which were thermally insulated, were exposed to fire. The frame was pushed into the oven on a steel trolley . For meaIn the second loading stage, the thermally damaged frame was laterally loaded with a pendulum under an initial impact angle of 23°. The structure was additionally equipped with strain gauges and accelerometers to measure the strain and acceleration histories at different locations on the frame. The horizontal displacement was measured with high-speed camera, with a frame rate of 1000 fps, which kept track of the stickers placed along the frame and the steel pendulum. The horizontal displacements were measured on the pendulum and at different locations on the frame see a. The dil = 25 mm. It should be noted that the main differences between local and nonlocal temperature exist close to the exposed surfaces, i.e., in these zones, nonlocal temperatures are slightly lower than the local, due to the relatively large temperature gradients. Local temperature causes unrealistically high thermally induced damage of the concrete surface (impact zone) and, as will be shown below, leads to unrealistic failure of concrete slab in front of the pendulum impact frame surface.In the following, the typical results obtained from the thermo-mechanical and dynamic simulations are shown and compared with the experimental results. wc = 6 mm. Bearing in mind the complexity of the problem, the agreement between experimental and numerical crack patterns is reasonably good.Experimentally measured and numerically obtained time displacement histories at different locations are shown in To investigate the influence of thermally induced damage of RC frame under static and dynamic loading on its response and resistance, a parametric numerical study was carried out. The simulations were performed for static and dynamic loading, with and without thermal pre-damage. In the case of dynamic loading, the side impact of pendulum was performed for three different displacement rates. Moreover, the importance of the rate sensitive analysis in static and dynamic analysis was investigated. The geometry, boundary conditions and loading were the same as in the above presented experimental and numerical investigations.t = 30 and 60 min is not notably different, i.e., 600 °C vs. 730 °C, respectively.Static analysis was performed by controlling horizontal displacement at the pendulum mid-line. Considered are the following cases: (i) initially undamaged frame, (ii) thermally damaged frame, hot and cold state after 30 min of fire exposure and (iii) hot and cold state after 60 min of fire duration. The reactions on the frame foundation are shown in terms of reaction-displacement (RD) responses see . The disThe typical failure modes are shown in In the dynamic analysis, the loading time history was the same as in the experimental test and simulation from Comparing the RD curves, it can be seen that principally the same is valid as for the static analysis, i.e., with increase of temperature induced damage, the peak resistance and initial stiffness decreases, especially for the hot state. The degradation of peak reaction for cold state is lower than in the case of static analysis. When compared to dynamic resistance of undamaged frame with that of thermally pre-damaged  the degradation is only 16%. Moreover, the reduction of initial stiffness is smaller than in the case of static loading and ductility of the response is not strongly influenced by the thermal damage. However, for the hot state not only concrete but also reinforcement is damaged and consequently, relatively high reduction of dynamic resistance (48%) and initial stiffness is observed for a duration of 60 min of fire. The reason for relatively large differences in the responses of cold and hot state is that in hot state concrete and reinforcement are damaged, however, in cold state the mechanical properties of steel are almost fully recovered.RDIF) is also shown. As can be seen, the dynamic resistance of the frame for different states and given loading conditions is not very different, as it varies between 1.72 and 2.51.The comparison between RD curves for static and dynamic loading shows that dynamic resistance is higher and the response stiffer. There are two principal reasons for this: (i) rate sensitive constitutive law for concrete and (ii) inertia effects of different kinds . In The typical failure modes are shown in As discussed above, the dynamic response exhibits higher resistance and stiffness. This is a consequence of the contribution of the rate dependent constitutive law of concrete and inertia effects. To investigate the contribution of these two effects on the dynamic response of the initially undamaged RC frame, additional parametric study is carried out. Static and dynamic analysis with and without rate sensitivity for three different displacement-loading histories of the pendulum see : low , the rate sensitivity has a significant contribution to the resistance (reaction) and failure mode, i.e., the resistance is approximately double compared to the case without rate sensitivity b. The maFor the medium impact velocity (725 mm/s), the impact force can be transferred over the slab in both cases, i.e., with and without rate sensitive constitutive law. Therefore, the effect of rate sensitivity is less important. However, compared to the structural inertia, its contribution is still relatively high. For instance, by comparing RD curves for the loading rate of 725 mm/s c with thComparing the failure modes obtained from quasi-static and dynamic analysis, it can be seen that in static analysis the critical sections are the top and bottom of the columns . HoweverIn the present study, static and dynamic 3D FE simulations of initially undamaged and damaged RC frames are carried out. Based on the results the following can be concluded: (i) The comparison between experimental test and numerical simulation shows that the thermo-mechanical transient analysis based on the temperature dependent microplane model is able to realistically replicate the experimental dynamic test of thermally pre-damaged RC frame; (ii) It is shown that instead of local temperature obtained from the standard heat analysis, temperature dependent degradation of concrete mechanical properties should be calculated using nonlocal (average) temperature. This is especially true for dynamic (impact) analysis; (iii) It is demonstrated that fire exposure of RC frames and related thermally induced damage significantly influence their behavior and resistance; (iv) For quasi-static loading, the reduction of structural resistance is the highest for the hot state because the steel reinforcement after cooling almost fully recovers. In the contrary to the peak resistance, the initial stiffness is controlled by concrete properties and it decreases with increasing of fire exposure. Consequently, the initial stiffness is lower for cold state. Ductility of the response is increasing with the increase of fire duration; (v) Compared to quasi-static analysis, in dynamic analysis the reduction of resistance and initial stiffness is principally similar, however, it is significantly higher for the hot state. The overall response is more brittle due to the contribution of inertia; (vi) It is shown that rate sensitive constitutive law for concrete significantly contributes to dynamic structural resistance and failure mode. As expected, with an increase of loading rate, strain rate becomes more important and its influence can be even stronger than the contribution of inertia effects. However, it should be pointed out that its contribution to the overall structural response does not depend only on the loading rate but also on a number of other parameters  and should be investigated for each case separately.


Met/Met, Met/Val, and Val/Val COMT genotypes differed in their response to bupropion in terms of depression scores.Pharmacodynamics and pharmacogenetics are being explored in pharmacological treatment response for major depressive disorder (MDD). Interactions between genotype and treatment response may be dose dependent. In this study, we examined whether MDD patients with M = 3.8 visits, SD = 1.5) and were prescribed bupropion or another antidepressant drug. All participants were adherent to pharmacotherapy treatment recommendations for >2 months following genetic testing.This study utilized a convenience sample of 241 adult outpatients (≥18 years) who met DSM‐5 criteria for MDD and had visits at a Midwest psychopharmacology clinic between February 2016 and January 2017. Exclusion criteria included various comorbid medical, neurological, and psychiatric conditions and current use of benzodiazepines or narcotics. Participants completed genetic testing and the 9 question patient‐rated Patient Health Questionnaire (PHQ‐9) at each clinic visit (SD = 17.9). For Val carriers, high bupropion doses resulted in significantly lower PHQ‐9 scores than no bupropion (t(868) = 5.04, p < .001) or low dose bupropion (t(868) = 3.29, p = .001). Val carriers differed significantly from Met/Met patients in response to high dose bupropion (t(868) = −2.03, p = .04), but not to low dose bupropion.Participants were mostly Caucasian (85.9%) outpatients  who were 44.5 years old, on average  with major depression disorder (MDD) with Met/Met, Met/Val, and Val/Val COMT genotypes differed in their response to bupropion treatment in terms of PHQ‐9 scores. High‐dose bupropion is beneficial for MDD patients with Met/Val or Val/Val COMT genotypes, but not for patients with Met/Met genotype. Pharmacotherapy is a mainstay of modern MDD treatment, but many patients do not respond to initial treatment or discontinue treatment because of adverse drug effects  genes and pharmacodynamic (PD) genes. Included PK genes are most often of the CYP450 family, which encode for ubiquitous proteins responsible for the metabolism of most drugs. Two of these PK genes (cytochrome P450 2D6 (CYP2D6) and cytochrome P450 2C19 (CYP2C19)), along with genes involved in hypersensitivity reactions  and human leukocyte antigen, A type, allele 31:01 (HLA‐A*31:01)), are currently the four genes that have amassed a level of empirical support to include them in FDA labeling Miller, .COMT, which encodes for catechol‐o‐methyl transferase, an enzyme responsible for the breakdown of dopamine in the frontal lobes. A common variant is a valine to methionine substitution  resulting in decreased capacity of the enzyme to degrade dopamine. Individuals with the Val/Val genotype display elevated enzyme activity and increased dopamine degradation; conversely, patients who are Met/Met homozygous have reduced enzyme activity and dopamine degradation  at this locus may vary in their response and/or tolerability to dopaminergic drugs.Pharmacodynamic genes encode for proteins such as transporters, receptors, growth factors, and other targets. Although potentially actionable, they have less research support compared with the aforementioned PK genes. A PD gene incorporated into one such available pharmacogenetic assay is Bupropion is a widely used antidepressant with a pro‐dopaminergic mechanism of action. Occupancy of dopamine transporter receptors (DAT) by bupropion and its metabolites averaged 26% under conditions of steady‐state oral dosing (150 mg every 12 hr of the sustained‐release (SR) formulation) as determined by positron emission tomography , date of genetic testing, primary and secondary diagnoses, dates of clinic visits that occurred 6 months prior to and 6 months after genetic testing, class and dose of antidepressant medications at time of each clinic visit, and the Patient Health Questionnaire (PHQ‐9) scores at each clinic visit. The items in the PHQ‐9 correspond to the nine symptoms listed in the DSM 5 for an MDD diagnosis. Additionally, participants met the following inclusion criteria: treated with pharmacotherapy; adherent to treatment recommendations based on genetic testing results for >2 months; and 18 years or older at the time of testing. Exclusion criteria included various comorbid medical conditions, current use of benzodiazepines or narcotics; comorbid neurological conditions and various other psychiatric comorbidities. Bupropion doses  were categorized as no bupropion, <200 mg (low dose), or ≥200 mg (high dose). COMT gene variants were classified as Met/Val, Val/Val, or Met/Met.Participants were MDD patients at a Midwestern psychopharmacology clinic who had available genetic testing results  conducted between 1 February 2016 and 31 January 2017. As this was a naturalistic study in an outpatient treatment setting, patient treatment plans ranged from initial diagnosis to medication management for those who had failed at least two antidepressants in different classes with an adequate dose and duration. A retrospective chart review utilizing electronic health record data extraction collected the following variables: demographics , COMT genetic variants, and bupropion dosing. Four cases had erroneous data for their PHQ‐9 scores and were removed. Chi‐square tests of independence were used to determine whether COMT gene variant was related to treatment with bupropion or bupropion dose at time of genetic testing or for new bupropion prescriptions subsequent to genetic testing.Descriptive statistics were calculated to characterize the sample for demographics, Pregenetic represented clinic visits before genetic testing was conducted; Placebo represented time period during which genetic testing had occurred, but before results were available and incorporated into the patient medical treatment (set at 4 weeks after genetic testing). For these observations, the simple effect of informing the patients that a genetic test is being conducted can be estimated; this effect was operationalized as changes to PHQ‐9 scores for this time frame. In the statistical analysis, we are thus able to detect a psychological effect simply due to the genetic testing process before the changes to medical treatment, in light of the genetic test results, are implemented.Multilevel models (or linear mixed‐effect models) were estimated. This approach allows integration of the repeated observations for each case, while also incorporating the impact of genetic, demographic, and bupropion predictors  from genetic testing date to 6 months after genetic testing. Other sample characteristics, including demographic variables and COMT genotype variant, are displayed in Table This study demonstrated high dose bupropion was beneficial for patients with COMT genotypes was typical of a largely Caucasian population. At any time during their treatment from baseline to up to 6 months after genetic testing, medication distributions were noted as 39.0% SSRI, 41.1% SNRI, 32.4% vortioxetine, and 49.4% bupropion.The distribution of n = 53) were currently taking bupropion. See Table COMT gene variant. Over the course of the observation period, 16.7% (n = 10) Met/Met, 22.5% (n = 29) Met/Val, and 26.9% (n = 14) Val/Val cases started a new prescription for bupropion.At the time of genetic testing, 24.1%  = 5.04, p < .001) and between low dose bupropion and high dose bupropion (t(868) = 3.29, p = .001). Finally, although these two categories of COMT genetic variants did not differ significantly in PHQ‐9 scores at low dose bupropion, Met/Val or Val/Val gene variants did differ significantly in response to high dose bupropion (t(868) = −2.03, p = .04) compared to Met/Met gene variant.High dose bupropion was beneficial for patients with 4Genetic polymorphisms play a role in the response to medications, an emerging science known as pharmacogenetics. In recent years, commercial pharmacogenetic assays have gained traction in medicine, and data suggest that these assays may be useful in selecting appropriate pharmacotherapy and reducing healthcare costs and utilization  have been associated with greater benefit in COMT Val/Val individuals, whereas drugs acting via dopamine antagonism  have been associated with greater benefit in Met/Met carriers  metabolizes catecholamines; thus, the association of COMT genotypes in treating MDD has been examined in terms of treatment response for some drugs. For example, two published studies on the role of the COMT val158met polymorphism in antidepressant treatment response investigating samples of 102 and 346 patients, respectively, report a tentative negative effect of the COMT 158Met/Met genotype on mirtazapine and citalopram response in MDD  response or remission , and primary evaluation of side effects  was beneficial for MDD patients with Val carrier COMT genotypes, but not for patients with a Met/Met genotype. This is an important and novel finding, as it contradicts previous studies showing no associations between COMT variant and remission or medication response for MDD patients  should be prescribed bupropion at doses ≥200 mg. Met/Met carriers (24.9% of patients in this study) should avoid, or cautiously use bupropion for MDD. The use of genetic testing, although not deterministic, may influence the probability of successful bupropion antidepressant response, especially when considered as a factor combined with depressive phenotyping and past individual and family of antidepressant treatment responses.Our data suggest that a high dose of bupropion (≥200 mg daily) is beneficial for MDD patients with Prospective work on the effectiveness of pharmacotherapy for MDD should include an analysis of pharmacodynamics and pharmacogenetic genotypes. This work provides the foundational elements to design a large randomized clinical trial to link the utility of pharmacogenomic testing guided drug selection to clinical outcomes.Dr. Fawver reports personal fees from Takeda Pharmaceutical Company, Lundbeck, Inc., personal fees from Janssen Pharmaceuticals, Inc., personal fees from Alkermes, outside the submitted work. Dr. Mirro reports grants from Medtronic plc, during the conduct of the study; grants from Agency for Healthcare Research and Quality (AHRQ), grants from Biotronik, Inc, grants from Janssen Scientific Affairs, personal fees from McKesson Corporation, personal fees from iRhythm Technologies, Inc., personal fees from Zoll Medical Corporation, other from Medical Informatics Engineering, outside the submitted work; and Dr. Michael J. Mirro's relationships with academia include serving as trustee of Indiana University and on the Indiana University Health Board.Jay Fawver and Mindy Flanagan helped to conceptualize, design, and conduct this study. Jay Fawver, Michelle Drouin, Mindy Flanagan, Thomas Smith, and Michael Mirro collected, analyzed, and/or interpreted the data and wrote the manuscript. Jay Fawver and Michael Mirro were in charge of overall direction and planning of the project. Additionally, all authors drafted or revised this manuscript critically for important intellectual content, approved the version to be published, and agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.