With great interest, we have read the recent article “The risk of malignancy in patients with IgG4-related disease: a systematic review and meta-analysis” by Yu et al. While we have a great appreciation for the work conducted by the authors there are some methodological issues need to be considered. First, the period of articles included in the study, almost before 2013, implied that most follow-up days in these articles were earlier than the established date of a unified definition of IgG4-RD, 2011. Thus, it may lead to misclassification bias in the study. Second, IgG4-RD is a fibrous-inflammatory process that often involves multiple organs; however, malignant tumors related to IgG4-RD proposed in the study were only confined to four diseases. Therefore, we suggest adding subgroup analysis for more malignancies depending on the prevalence of IgG4-RD involved organs to ensure better clinical practice. Third, the causation between IgG4-RD and malignancy remains obscure currently. The time course for development in different malignancies varies significantly so that we cannot infer that malignancies discovered after IgG4-RD are directly relevant. With problems mentioned above, we recommend solutions to make this article more convincing. Dear Editor,With great interest, we have read the recent article “The risk of malignancy in patients with IgG4-related disease: a systematic review and meta-analysis” by Yu et al. . publishFirst, the calendar period of 10 articles included in the study, almost before 2013, implied that most follow-up days in these articles were earlier than the established date of unified definition of IgG4-RD, 2011. Before 2011, several diseases such as Mikulicz disease, Kuttner’s tumor, and Riedel thyroiditis were not categorized into comprehensive diagnostic criteria for IgG4-RD published by the Japanese IgG4 team, organized by the Ministry of Health, Labor and Welfare of Japan. Therefore, misclassification bias, which occurs when an individual is assigned to a different category than the one to which they should be assigned, may exist in the study. These cases before 2011 may be underdiagnosed due to the lack of complete reports of serum IgG or histopathological findings. Besides, the organ-specific criteria have already included IgG4-related autoimmune pancreatitis, IgG4-related Mikulicz’s disease, and kidney disease, but they are not suitable for the diagnosis of patients with involvement of other organs [Second, IgG4-RD is a fibrous-inflammatory process that often involves multiple organs, either synchronously or metachronously, including cervical lymph nodes, lung, liver, bile duct, gastrointestinal tract, central nervous system, thyroid, pancreas, kidney, prostate, arteries, lymph nodes, skin, breast, lacrimal glands and salivary gland . AlthougThird, the causation between IgG4-RD and malignancy remains obscure. IgG4-RD has ambiguous presentations with pseudotumors which can be disseminated in the affected organs, mimicking metastases. For IgG4-RD, PET/CT is utilized to detect the disease activity and determine the extent of organ involvement . It is m


Campylobacter jejuni isolates resistant to clinically important antibiotics, particularly fluoroquinolones (FQs), is a global public health concern. Currently, little is known about antibiotic tolerance and its effects on resistance development in C. jejuni. Here, we show that exposure to ciprofloxacin or tetracycline at concentrations 10 and 100 times higher than the MIC induces antibiotic tolerance in C. jejuni, whereas gentamicin or erythromycin treatment causes cell death. Interestingly, FQ resistance rapidly develops in C. jejuni after tolerance induction by ciprofloxacin and tetracycline. Furthermore, after tolerance is induced, alkyl hydroperoxide reductase (AhpC) plays a critical role in reducing FQ resistance development by alleviating oxidative stress. Together, these results demonstrate that exposure of C. jejuni to antibiotics can induce antibiotic tolerance and that FQ-resistant (FQR) C. jejuni clones rapidly emerge after tolerance induction. This study elucidates the mechanisms underlying the high prevalence of FQRC. jejuni and provides insights into the effects of antibiotic tolerance on resistance development.Antibiotic tolerance not only enables bacteria to survive acute antibiotic exposures but also provides bacteria with a window of time in which to develop antibiotic resistance. The increasing prevalence of IMPORTANCE Antibiotic tolerance compromises the efficacy of antibiotic treatment by extending bacterial survival and facilitating the development of mutations associated with antibiotic resistance. Despite growing public health concerns about antibiotic resistance in C. jejuni, antibiotic tolerance has not yet been investigated in this important zoonotic pathogen. Here, our results show that exposure of C. jejuni to ciprofloxacin or tetracycline leads to antibiotic tolerance development, which subsequently facilitates the emergence of FQRC. jejuni. Importantly, these antibiotics are commonly used in animal agriculture. Moreover, our study suggests that the use of non-FQ drugs in animal agriculture promotes FQ resistance development, which is crucial because antibiotic-resistant C. jejuni is primarily transmitted from animals to humans. Overall, these findings increase our understanding of the mechanisms of resistance development through the induction of antibiotic tolerance. Antibiotic tolerance refers to the ability of an entire population of susceptible bacteria to withstand antibiotic treatment for prolonged periods of time . This isCampylobacter spp., particularly Campylobacter jejuni, is a leading bacterial cause of gastroenteritis, accounting for 400 to 500 million cases of diarrhea worldwide per year  Campylobacter is increasing at an alarming rate and has significantly compromised the efficacy of this critically important antibiotic class  or tetracycline. Importantly, FQ resistance is rapidly developed through antibiotic tolerance induced by FQs and non-FQ antibiotics. Our results suggest that antibiotic tolerance plays an important role in the development of FQ resistance in C. jejuni.Despite public health concerns about antibiotic resistance in C. jejuni develops tolerance during antibiotic exposure. To test this hypothesis, we utilized several different antibiotics: ciprofloxacin, erythromycin, tetracycline, and gentamicin. These were chosen because C. jejuni is likely to be exposed to these antibiotics during treatment of human campylobacteriosis or in livestock production  after 24 h but not after 48 h, likely due to bacterial killing by erythromycin  and its absence  . Altogether, these results suggest that FQ resistance rapidly develops in C. jejuni during antibiotic tolerance induced by FQs and non-FQ antibiotics.FQreatment . Howevercycline) . Ciprofl control . These rfloxacin , indicatRC. jejuni in antibiotic-tolerant cells. C. jejuni harbors a single copy of genes encoding alkyl hydroperoxide reductase (AhpC), catalase (KatA), and superoxide dismutase (SodB)  . In the ΔahpC mutant, ciprofloxacin treatment markedly increased the accumulation of hydrogen peroxide  , which aype (WT) . We obseperoxide , a substperoxide . These rC. jejuni uses PerR . This indicates that the antioxidation function of AhpC is required during antibiotic tolerance in C. jejuni. These results demonstrate that AhpC plays an important role in preventing the development of FQ resistance through tolerance induction in C. jejuni.To further confirm the role of AhpC in FQ resistance development during antibiotic tolerance, we used mutants defective in the regulation of oxidative stress responses. ses PerR  and CosRses PerR  to respocription , 27. Coscription . Thus, an strain  and a ΔpR mutant . The fref the WT , confirmC. jejuni. Studies demonstrate that antibiotic tolerance or persistence induced by intermittent antibiotic exposures or drug combinations precedes the emergence of antibiotic resistance mutations in Escherichia coli and Staphylococcus aureus . Interestingly, the level of ahpC transcription was higher in cells treated with tolerance-inducing antibiotics  than in those treated with bacteria-killing antibiotics , although the bacteria-killing antibiotics produced more hydroxyl radicals than the tolerance-inducing antibiotics   , 42. FQ ni cells , suggestRCampylobacter has been ascribed mainly to the use of FQs in agriculture, because C. jejuni is typically transmitted from food-producing animals to humans  medium (Difco) under microaerobic conditions .of ΔahpC , ΔkatA  to an optical density at 600 nm (OD600) of 0.08. The bacterial suspension was incubated with shaking at 200 rpm under microaerobic conditions. After 7 h, antibiotic exposure was initiated by adding 1× MIC, 10× MIC, or 100× MIC of antibiotics . The concentrations were determined based on the MIC of the WT . The cultures were also treated with 1× MIC of antibiotics to compare the effects of a relatively lower concentration of antibiotics on tolerance. The MICs of ciprofloxacin, tetracycline, erythromycin, and gentamicin in C. jejuni NCTC 11168 were 0.063 μg/mL, 0.031 μg/mL, 1 μg/mL, and 0.5 μg/mL, respectively, as determined with a microdilution susceptibility test. Since these MICs show a wide concentration range, we could not use a fixed concentration for the four antibiotics. For instance, 1 μg/mL is equivalent to 15.9× MIC of ciprofloxacin, 32.3× MIC of tetracycline, 1× MIC of erythromycin, and 2× MIC of gentamicin in C. jejuni NCTC 11168. The growth of C. jejuni can be seriously affected by 1 μg/mL  of ciprofloxacin but not by 1 μg/mL  of erythromycin. Using the same fixed concentration for different antibiotics can generate different levels of antimicrobial activity. Thus, we decided the concentration of antibiotic treatment based on the MIC. For sampling, 1.2 mL of C. jejuni cultures were harvested and washed with fresh MH medium. After washing, C. jejuni cells were resuspended in 100 μL of MH broth and spread for enumeration onto MH agar plates and MH agar plates supplemented with 1 μg/mL ciprofloxacin. Colonies growing on MH agar plates supplemented with ciprofloxacin were randomly picked up and subjected to a broth microdilution susceptibility test to confirm resistance  and concentrated 10-fold. The assay was conducted according to the manufacturer’s instructions . Briefly, 100 μL of a sample was placed onto a 96-well plate . Hydroxyphenyl fluorescein (HPF) solution was diluted to a final concentration of 5 μM. The fluorescence at excitation/emission (ex/em) values of 530/590 nm was measured using a plate reader  with gentle shaking at 25°C. Measured fluorescence signals were normalized to protein concentrations determined using a Bradford assay.C. jejuni cells were exposed to antibiotics for 24 h as described above. The samples were washed twice, concentrated 10-fold, and placed onto a 96-well plate . The working solution  was added to each sample solution. The mixture was incubated at room temperature for 30 min, and fluorescence was detected at ex/em 530/590 nm using a plate reader . The hydrogen peroxide concentration was determined by comparing it with a standard curve prepared with known hydrogen peroxide concentrations and normalized to protein concentrations determined using a Bradford assay.The level of hydrogen peroxide formation under antibiotic treatment was measured with the Amplex Red hydrogen peroxide/peroxidase assay kit , according to the manufacturer’s protocol.


The brittleness of plain concrete represents a significant issue to the integrity of concrete structures when subjected to impact loading. Recent rapid industrialization has attracted researchers to find a solution for concrete brittleness and enhance its ductility. In light of this, the prepacked aggregate fibrous concrete (PAFC) with single and double precoated coarse aggregates using asphalt is proposed and examined. Nine different mixtures were designed using polypropylene and steel fibre of 3% dosage with single and double asphalt-coated aggregates. Specimens were prepared with natural aggregate and 100% C-graded asphalt-coated aggregate to evaluate their impact strength. The ACI Committee 544 drop-weight impact standard was followed in the testing of all specimens. Results indicated that using asphalt-coated aggregate can improve the impact energies of concrete. The impact energy at cracking and failure of the single asphalt-coated aggregate specimen was 1.55 and 2.11 times higher, while the double-coated aggregate specimens exhibited 1.73 and 2.56 times greater than the natural aggregate specimen, respectively. The contribution of fibres in enhancing the impact resistance is remarkable compared to the single- and double-coated aggregates used in PAFC. The growing use of concrete materials has led to increasing concrete constructions being able to withstand frequent or infrequent impact loads . Some tyCivil engineering technology has advanced at an alarming rate. Conventional fibrous concretes have evolved continuously with different forms; prepacked aggregate fibrous concrete (PAFC) is one of them. Placing coarse aggregate and fibre particles in an empty formwork and filling gaps with cement grout mixture is PAFC. Several investigations have been employed regarding the mechanical properties of PAFC and their impact-resistance performance. Mohammadhosseini et al.  examinedBased on the introduced literature, a material that can absorb energy and increase the impact resistance of PAFC in its hardened condition must be developed. In the present study, the concept of asphalt-coated aggregate with a single and double coating is used for producing the PAFC to evaluate their impact-resisting performance. Moreover, the combined effect of fibres (steel and polypropylene) and asphalt-coated aggregates were used to increase the impact energy absorption capacity of PAFC. The utilization of the single and double asphalt-coated aggregate in concrete is a new innovation in the technological development in the construction industry. This research area has still not been explored comprehensively and needs particular focus to implement this type of concrete in practice.Impact loading is a form of dynamic loading that is distinguished by a rapid change in velocity that occurs in a short period. In line with the momentum theory, it is possible to considerably increase the impact load, followed by large kinetic energy. Structures often collapse due to their inability to absorb massive impact energy, such as in air transportation’s renowned bird strike catastrophes. Hence, impact resistance is thus determined by a structure’s combined energy absorption and load-bearing capabilities. The material’s load-bearing capability ensures structural stability and stiffness, whereas its energy absorption capability reduces the internal damage affected by a high impact. The impact load is sustained by the concrete matrix and aggregates in traditional cement-based concrete. Inspiration can be drawn from nature’s bionic species to create PAFCs that are more resistant to impact. Biologically, the woodpecker is an outstanding demonstration of a predator endowed with ideal impact-resistance capabilities. Statistics show that a woodpecker may hammer a tree 12,000 times in one day at a maximum speed of 6–7 m/s without producing any brain damage or cerebral trauma . The wooThe coarse aggregate covered with asphalt is seen in 2 and its specific surface area was 318 kg/m2. River sand possessing a fineness modulus of 2.39 and water absorption of 1.14 was utilized as a fine aggregate in the final product. In compliance with ASTM C939 [According to IS: 1489-2015  specificSTM C939 , it had With an optimal sand/binder (s/b) ratio (1.0) and binder/water ratio (0.45), nine different concrete mixes were made and evaluated in this research. A set of flow cone experiments performed in accordance with ASTM C939  determinUsing cylindrical specimens with dimensions of 152 mm in diameter and 64 mm in height, the impact strength of the PAFC was tested. The compressive strength was assessed using the 100 mm cubical specimens. For each combination, three specimens were made, and the mean value was given and discussed. The stage-by-stage method of PAFC casting, as shown in g: gravity acceleration, h: hammer drop height, m: mass of hammer, and n: impact numbers.The drop-weight impact test was used to assess the PAFC specimens’ impact strength following the recommendations of ACI Committee 544 . This stThis study is focused on the impact resistance of fibrous concrete by combining two different concepts. First, the preplaced aggregate fibrous concrete is produced with two different fibres and the gravity method of grouting was applied. Second, the natural aggregates were precoated with asphalt in a single and double layer before being used in concrete production. The combined effect of fibres and asphalt-coated aggregate on the impact resistance has been studied extensively. This research has studied the compressive strength, number of impact blows required to initiate specimen cracking and to fail it, ductility index, failure pattern, and failure mechanism.The compressive strength results attained from the laboratory test for all specimens are presented in While asphalt-coated aggregates had a moderate effect on compressive strength, PF inclusion increased it to a higher amount, as shown in Asphalt-coated aggregate and SF’s combined action on compressive strength is remarkable. As displayed in The effect of SF and PF on the compressive strength of PAFC comprising single- and double-coated aggregate is illustrated in The impact energy of the specimens was improved when 100% asphalt-coated aggregate was used instead of natural aggregate. Moreover, increasing the asphalt coating from single to double layer resulted in a sharp rise in impact energy at cracking and failure, as shown in Generally, adding fibres into PAFC results in an inherent improvement in impact energies. The impact energies at cracking and failure for the P-PF specimens were 1139.8 and 2747.7 J, respectively. The addition of PF in PAFC comprising single- and double-coated aggregates displayed a positive effect, as shown in The impact energies corresponding to cracking and failure showed prominent enhancements, for the single and double asphalt-coated aggregate specimens as displayed in Flexural ductility refers to the capacity of flexural members such as beams and slabs to survive plastic deformation. The ductility index is derived by dividing the failure deflection by the yielding point deflection . ElasticThe ductility index value of PAFC was improved by adding PF and coated aggregate. For instance, the recorded ductility value of P-PF, P-PF-C1 and P-PF-C2 specimens was 2.4, 2.6 and 2.9. Enhanced post-cracking behaviour of the PF specimens is attributable to the bridging effect of the PF fibres, which postponed breakdown and raised variations between cracking and failure impact energies. A remarkable enhancement in the ductility index was observed in the SF-based specimens. The P-SF, P-SF-C1 and P-SF-C2 specimens exhibited ductility index values of 5.3, 5.6 and 5.8, respectively. Higher failure impact energies resulted from SF’s excellent ductility, which is linked to its higher tensile strength and superior configuration when compared to PF. It is clear from the above discussions that the influence of fibres on ductility index was considerably higher, while asphalt-coated aggregate displayed marginal positive results.As a result of the impact loading, four distinct defects were observed in PAFC. First, repetitive impact force was delivered to the cylindrical specimen, resulting in localized contact destruction . SecondlAsphalt-coated aggregates and fibres were used to produce PAFC mixtures with superior impact resistance. The following conclusions were drawn from experimental research.A reduced compressive strength was observed when natural aggregate was replaced for either a single or double layer of asphalt-coated aggregate. Compared to the natural aggregate specimens, the compressive strength of the single- and double-coated specimens without fibres was reduced by 5.08 and 11.02%, respectively. Similarly, 5.97 and 7.67% lower compressive strengths were found in the P-PF C1 and P-PF C2 specimens as compared to the P-PF specimen, while the compressive strength was reduced by 3.95 and 5.53% for P-SF-C1 and P-SF-C2 specimens, respectively, as compared to P-SF specimens.Compared to NC, the compressive strength of the PF and SF-based specimens containing 100% natural aggregate increased by 25.17 and 48.06%, respectively. Fibrous specimens with single and double coatings showed a similar trend of strength enhancement. Fibres played a significant role in this development owing to their extraordinary ability to bridge micro and macro cracks.Impact energies (EO1 and EO2) increased from a single layer of asphalt coating to a double layer. The EO1 and EO2 values of the single asphalt-coated aggregate specimens were 1.55 and 2.11 times higher than the natural aggregate specimens, respectively. The EO1 and EO2 values were 1.73 and 2.56 times greater for the double asphalt-coated specimens. An excellent post-cracking resistance was seen in the specimens when single- and double-layer asphalt-coated aggregates were employed.The impact energy was improved by adding asphalt-coated aggregate into PAFC. The EO1 and EO2 values of the P-PF-C1 specimens were 1.85 and 2.91 times greater than those of NC-C1. These values were much greater in the P-SF-C1 specimens . There was a similar increase in strength in the double-coated aggregate fibrous concrete, which were 1.76 and 2.81 times greater EO1 and EO2 values for P-PF C2 specimens than NC-C2 specimens. For the P-SF-C2 specimens, the EO1 and EO2 values were 2.45 and 7.75 times higher than the NC-C2 specimen.The post-cracking resistance of PAFC was improved significantly by adding fibres and marginally by adding asphalt-coated aggregate. The impact ductility index for the asphalt-coated aggregate improved from 1.2 to 1.8 for non-fibrous concrete, 2.4 to 2.9 for PF-based fibrous concrete and 5.3 to 5.8 for SF-based fibrous concrete. A brittle failure was observed in all non-fibrous specimens, while a ductile failure was observed in fibrous specimens irrespective of asphalt-coated aggregate usage.


Moreover, the minimal flexural strength response of 2.504 N/mm2 was obtained with a mix ratio of 0.6:0.75:0.3:4.1:0.25 for water, cement, QD, coarse aggregate and SDA, respectively. The test of the appropriateness of the developed model was statistically verified using the Student’ t-test and an analysis of variance (ANOVA), and was confirmed to be acceptable based on computational outcomes at the 95% confidence interval. Furthermore, the scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) were used to evaluate the morphological and mineralogical behavior of green prior concrete samples with various additive mixture compositions. The addition of QD and SDA, on the other hand, aided the creation of porous microstructures in the concrete matrix due to fabric changes in the concrete mixture, potentially aided by the formation of cementitious compounds such as calcium aluminate hydrate and calcium silicate hydrate.Pervious concrete provides a tailored surface course with high permeability properties which permit the easy flow of water through a larger interconnected porous structure to prevent flooding hazards. This paper reports the modeling of the flexural properties of quarry dust (QD) and sawdust ash (SDA) blended green pervious concrete for sustainable road pavement construction using Scheffe’s  optimization approach. The simplex mixture design method was adapted to formulate the mixture proportion to eliminate the set-backs encountered in empirical or trials and the error design approach, which consume more time and resources to design with experimental runs required to evaluate the response function. For the laboratory evaluation exercise, a maximum flexural strength of 3.703 N/mm A pervious concrete is achieved by carefully controlling the quantity of water and cementitious materials to generate a thick coating paste with a substantial void content and highly permeable and interconnecting voids that can drain the surface runoff very quickly, which thereby preserves the service life of road pavement ,2. PerviPervious concrete is known for being gap-graded and having enhanced porosity, whilst no fines concrete provides an innovative approach to the management, controlling and proper channeling of storm water runoff to a safe discharge point . It is uSince the US Environmental Protection Agency (EPA) expanded storm water management requirements, there has been a demand for pavements that reduce surface runoff. Traditional roadway construction frequently fails to efficiently manage storm water runoff. Pervious concrete could be a viable solution to the problem of storm water runoff . Perviou2 was obtained with a mix of 0.54:0.815:2.045:3.425:0.185 for water, cement, fine aggregate, coarse aggregate and OSP, respectively, while a minimum strength response of 17.85 N/mm2 was obtained with a mix of 0.525:0.825:2.2:4.05:0.175 for water, cement, fine aggregate, coarse aggregate and OSP, respectively. Alaneme and Mbadike , Z2 [0.45:0.9:0.13:1.95:0.1], Z3 [0.5:0.85:0.19:2.85:0.15], Z4 [0.55:0.8:0.25:3.55:0.2] and Z5 [0.6:0.75:0.3:4.1:0.25].The initial mix ratios were Z1 [1:0:0:0:0], X2 [0:1:0:0:0], X3 [0:0:1:0:0], X4 [0:0:0:1:0] and X5 [0:0:0:0:1].The equivalent pseudo-component values which are in binary form, indicating the pure blend in the mix configuration, are Xi and Zi into Equation (15) helps calculate the pseudo-components from the resulting actual mixture components.The substitution of X1 = water–cement ratio fraction; X2 = Portland cement fraction; X3 = quarry dust fraction; X4 = coarse aggregate fraction; and X5 = sawdust ash fractionXThe equation is transformed into the matrix notation for the computation of the experimental mixture proportions . as follows12131415232425343545Therefore, for AThe matrix table for the mixture proportion formulation is shown in Similarly, applying the actual and pseudo mathematical relationships presented in Equation (15), the next fifteen control points are calculated and designed for the authentication of the generated Scheffe’s regression model.For second-order control points1For C2For C3For C4For C5For C12For C13For C14For C15For C23For C24For C25For C34For C35For C45For CThe matrix table for the mixture proportion formulation is presented in This is a vital procedure in material science that describes the broad and general method of probing and measuring a material’s structure and properties .X-ray fluorescence (XRF) is a secondary characteristic emission from a substance fraught by being barraged with high-energy gamma or X-rays. The trend is broadly adapted for the assessment of chemical and elemental oxides, for the proper characterization of the test materials’ chemical constituents and for research in geochemistry and forensic science . High-enScanning electron microscopy (SEM) uses a kind of electron microscope to directly study the surfaces of solid objects or materials through the utilization of a beam of the directed electrons of relatively low energy scanned in a regular manner over the surface of the specimen. Large, hardened and bulky specimen can be taken for investigation in the SEM as no specific sample preparation technique is required. For clear imaging to be obtained, the specimen to be tested needs to be electrically conducting. To achieve this level of conductivity, a film of a metal such as gold of 50–100 Angstroms thick is evaporated on the surface of the specimen in a vacuum .In EDXRF spectrometers, a sample is directly irradiated by an X-ray tube functioning as a source, and the fluorescence emitted by the sample is detected with an energy dispersive detector. All spectrometers have three basic components: a radiation source, sample substance and detection mechanism. The varied energy of the characteristic radiation coming straight from the sample can be measured using this detector. The detector can distinguish between the radiation emitted by the sample and the radiation emitted by the various elements present in the sample. Dispersion is the term for this separation . The samh1 and h2) was recorded and utilized in Equation (16) to compute the hydraulic conductivity (k) of the pervious concrete mixtures using the mathematical expression provided in Equation (16). Where A and L are the cross-sectional area and length of the specimen, respectively, a is the cross-sectional area of the pipe shrouding the specimen [Permeability analysis on pervious concrete specimens was also performed using the falling head method, which involves sealing the specimen and placing it between two pipes. The time it takes for the water pressure head to drop to preset values The Cantabro test is a fast and intensive method of evaluating pervious concrete durability that involves impact loading a half-height 100 mm diameter cylinder in a rotational steel drum. The mass loss should be kept to a minimum. The test can be halted at predetermined intervals (after 50 or 100 cycles) to capture the intermediate mass loss and observe the damage progression as well as the ultimate mass loss value after 500 revolutions. ASTM C944 is an accelerated test technique for determining the abrasion resistance of pervious concrete. Modifying a press drill to hold a rotary cutter made of stacked washers of 25–32 in diameter revolving at a speed of 200 rounds per minute under a load of roughly 98 N or a doubling load creates the test equipment. The test is carried out on three different regions that replicate the pervious concrete pavement’s surface .This test laboratory method helps assess the rupture or bending strength of the concrete material derived just before the test sample under study yields in a flexure test. The derived test response is the maximum stress that the concrete material experiences within its yield moment. The concrete samples for this test are thoroughly mixed and compacted in a beam molds with dimensions of 100 mm × 100 mm × 400 mm. The resulting concrete beams were demolded and cured for a 28 day period of hydration before being taken for the flexural test. Three replicates for each Scheffe’s experimental runs were produced with forty-five concrete beams for an experimental test utilized for the model formulation, while the other forty-five beams (control test) were taken to evaluate the developed Scheffe’s regression model. After 28 days of curing, the three samplings for each mixture were crushed and the average flexural strength was calculated using the calculation in Equation (17). The flexural testing configuration is presented in t-test, as well as an analysis of variance (ANOVA), which is utilized to determine the mean differences between the control experiment or actual results and the model-predicted results. With respect to the flexural strength responses, statistical tests are conducted for second-order regression models developed at a 95% confidence level. By substituting the respective values of the pseudo-components (Xi) into the created model equation, the predicted values (Y-predicted) for the test control points were obtained [The adequacy test of the generated Scheffe model was carried out using a statistical method, namely Student’s obtained ,60.Null HypothesisThere is no considerable variance between the model-predicted and laboratory test results.Alternative HypothesisThe findings of the laboratory test and those anticipated by the model are significantly different.Series of laboratory tests were carried out on the mixture components to evaluate their general engineering behavior as civil construction materials. Sieve analysis and specific gravity tests were carried out on the test aggregates and admixtures to assess the gradation and particle size distribution. The sieve analysis test result which illustrates the variation in the soil grain sizes using a cumulative frequency distribution curve is shown in the semi-log graph in 2 (57.85%), Al2O3 (8.35%) and Fe2O3 (4.3%), which produces a sum of 70.52% by composition, whilst QD on the other hand possesses SiO2 (48.5%), Al2O3 (15.93%) and Fe2O3 (6.01%) to also produce a total sum of 70.44% by composition which showed a good pozzolanic property in accordance with ASTM C618, 98 specifications. The abundance of calcium oxide in the test materials—13.52%, 10.4% and 11.3% derived from QD, SDA and Portland cement binder, respectively—enhances the complete cement hydration which improves the mechanical strength and durability behavior of the green concrete produced, as presented in 3, 2.24 and 1755 kg/m3, 2.62 for SDA and QD, respectively [The assessment of the chemical properties of the test admixtures was achieved using X-ray fluorescence (XRF). The obtained result showed that SDA mostly has SiOectively ,64.1 experimental point with 14.1% water, 30.8% cement, 3.25% QD, 50.243% coarse aggregate and 1.62% SDA produced a maximum slump value of 77 mm. However, the C12 experimental point produced a minimum slump value of 42 mm with 10.61% water, 16.06% cement, 4.6% QD, 50.243% coarse aggregate and 3.645% SDA. The obtained results showed a linear decrement in the slump response of the freshly blended concrete specimen as the percentages of the admixtures present in the mix increases [Laboratory tests to assess the workability properties of the freshly mixed blended cement–SDA–QD concrete matrix were carried out. This test aimed to determine the placeability and workability behavior of the fresh concrete mixture with respect to the erratic ratios of cement–SDA and fine agg.–QD combinations as defined by Scheffe’s mixture design formulation. The obtained experimental results indicate that the value of the slump test reduces with the increase in the QD and SDA fractions in the concrete mixture, thereby resulting in more water being needed in order to make the mixture more workable. The reason may be attributed to the presence of alumino-silica content in the admixtures as well as the surface area increment . The obtained result is presented in a contour plot assessing the impact of the admixtures on the workability behavior of the concrete, as shown in ncreases ,661 produced a minimum weight loss of 1.64–21.64% from 100–500 revolutions, respectively [5 with a weight loss of 21.48–46.94% from 100 to 500 revolutions, respectively. Wu et al. [To examine the abrasion resistance behavior of the pervious concrete produced, the hardened cylindrical concrete samples for the five pure blends achieved in the design experimental points were taken for the experiment. The test concrete samples were first weighed to derive its initial weight and taken to the Cantabro test apparatus to assess the rate of mass loss after each of the 100 revolutions, with the overall results taken and plotted after a total of 500 revolutions, as presented in ectively . The weiu et al.  found ne2 at 7.32 mm/s with was obtained with SDA and QD contents of 2.833% and 3.683%, respectively, while a minimum response of 4.64 mm/s was obtained at Y5 with SDA and QD contents of 4.167% and 5.0%, respectively, as shown in the graphical bar chart in The hydraulic conductivity property is essential as it is required to enable the surface runoff to infuse through the pervious concrete surface and be directed to the safe discharge point to avert flooding and erosion issues. The hydraulic conductivity property testing provides an essential evaluation parameter to define the penetrability of pervious concrete, which would enable the proper channeling of surface runoff from the road way to avoid failure due to erosion. Water must be able to travel through a pervious concrete pavement at a rate of at least 5.4 mm/s ,69. From1 produced the greatest strength value of 3.703 MPa, while points corresponding to Y5 produced the minimum values of 2.504 MPa. 1, while the minimum flexural strength value was 3.193 MPa for sites corresponding to C45 [For the fifteen distinct combination design points, experimental results in terms of the flexural strength of concrete beam samples hydrated for twenty-eight days were obtained with a total of three replicates for each design point. The values are used to generate Scheffe’s second-order regression model for the compressive strength property of pervious concrete optimization using SDA and QD additives . As indig to C45 ,58. Due g to C45 .By the substitution of the obtained laboratory responses for the concrete’s flexural strength property in Equation (14) into Equation (12), the model equation is as shown in Equation (18) and t-test and ANOVA, the adequacy of the constructed Scheffe’s model was tested using the experiment’s control points. Using Student’s p-value of 0.554, which is greater than the alpha value of 0.05. This indicates that there was no significant difference between the actual or laboratory-derived results and the model-predicted results [The developed second-order regression model’s prediction performance was evaluated using an analysis of variance (ANOVA) by statistically assessing the laboratory- and model-predicted values at 95% confidence intervals, as shown in  results ,74.t-test to further assess the created model prediction performance; if t Stat > t critical two-tail, we reject the null hypothesis. We used the aforementioned requirement to conduct a two-tail inequality The sensitivity analysis was performed to evaluate the impact of each factor level or model input parameter on the target variable. In this case, the input variables are the components of a five-component mixture design optimization based on Scheffe’s theory. A unitary input variable is deleted for a specific trial test to perform a sensitivity analysis for the constructed quadratic regression model, and a regression model is built to generalize the remaining components with the output variable. The mean absolute error (MAE) and root mean squared error (RMSE) loss function parameters were used to statistically assess the model performance ,78. This1, Y3 and Y4) served to designate mix 1, mix 3 and mix 4, respectively. These nano-tests were performed in order to elucidate and ratify the pozzolanic action from the morphological examination of the concrete specimens as a result of the optimization exercise shown in Scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) were deployed for the assessment of the microstructural and morphological performance of the QD and SDA blended with pervious concrete specimens. Taking a critical examination of the experimental points for the binary blends with a maximum and minimum rheological and mechanical strength performance . There is no substantial discrepancy between the model-predicted and actual control results, according to the computed performance evaluation result. The obtained results for flexural strength, abrasion resistance and permeability response showed robust strength applications for road drainage purposes. Additionally, with the aid of scanning electron microscopy and electron diffraction spectroscopy, the pooled effects of SDA and QD in green pervious concrete production were qualitatively inveterate.Using Student’s Thus, the combination of QD and SDA aided the concrete matrix to form porous micro structures and enhanced its mechanical and hydraulic gradient properties. Finally, the added SDA and QD were observed to be valuable constituents in the development of the green pervious concrete material with saving costs through the recycling of solid wastes and its derivatives as well as enhanced its mechanical behavior and hydraulic gradient performance for pavement applications to successfully drain storm water.The mechanical behavior of the green pervious concrete incorporated with solid waste materials and derivatives—namely SDA and QD—was investigated using Scheffe’s mixture theory to derive the optimum mixture concentration. The following conclusions were taken from the findings and outcomes of the research work:


To achieve more accurate prediction of the potential failure location and to conduct a deeper analysis of the failure mechanism of concrete constructions, it is critical to probe the evolution process of internal meso-cracks that bear various intensities of load. While a computer Tomography (CT) test provides a non-destructive detection technique for obtaining the internal meso-damage state of concrete, traditional image processing and Digital Image Correlation (DIC) are ineffective in extracting meso-damage information from concrete CT images. On the other hand, by observing the shape change law of concrete’s internal holes under load, it is proposed to use the hole roundness and area fraction formula, developed based on the stereology principle and morphology, to characterize and predict the potential failure location. Four features particularly addressed include the CT image as a whole, image equal partitioning, crack and non-crack areas, and representative holes. The approach is to explore the variation law of critical hole shape parameters, especially the hole roundness under different loading stages, and analyze the relationship between the change in hole shapes and the final macro-crack positions. It is found that compared with the average area fraction, the average hole roundness value of cross section images is more sensitive to the change in stress. In both uniform partitioning and non-uniform partitioning, the average hole roundness value near the final macro-crack location exhibits an increase trend with the stress, while the smoothing effect caused by the hole roundness averaging always exists. Near the final macro-crack location, the roundness of each individual hole is positively associated with the stress, while away from the final macro-crack location such a relation may not be observed. This trend expounds the evolution process of meso-damage in concrete, and the finding can be used to predict the accurate locations of macro-cracks. Initial meso-damage, such as air voids and meso-cracks, are contained inside concrete structures at the beginning of the formation of concrete. Concrete structures are inevitably subjected to external loads from their own weight, earthquakes, and impact force in the service process, resulting in further accumulation of internal meso-damage, initiation of new meso-cracks, additional crack development, and even macro-damage . Such daFrom the macroscopic scale, concrete is a homogeneous material. From the mesoscopic scale, concrete is a heterogeneous material, composed of aggregate, mortar, and air voids. Meso-damage is the phenomenological expression of the deterioration of the material’s mechanical properties from the mesoscopic scale. Before the peak strength of concrete, internal cracks in concrete are referred to as meso-cracks and after the peak strength, internal cracks called macro-cracks. A meso-crack is used as the measure of meso-damage for concrete materials.Under the condition of load, the process of initiation, propagation, connection, and penetration of meso-cracks in concrete reproduces the entire realistic evolution process of meso-damage. Therefore, research on the meso-damage evolution of concrete is helpful for exploring the macroscopic mechanical characteristics and the meso-damage mechanism. The purpose of this research is to seek clues for the mix design of concrete materials in engineering, and to provide ideas and methods for studying the failure criteria of concrete under various loads.In recent years, various non-destructive testing technologies (NDT), including Scanning Electron Microscopy (SEM) ,3, acousTo quantitatively describe the evolution of concrete internal meso-damage under load, it is necessary to ensure that the size of the specimen is large enough to reflect the macroscopic properties of concrete materials, and the internal meso-damage of concrete is observable. However, the methods mentioned above have some shortcomings in the study of meso-damage of concrete. For example, SEM and fluorescence microscopies have the characteristics of large magnification, small field of view and small sample, leading to the test results not to reflect the whole picture of the internal mesoscopic scale of concrete ,11. AcouTo track the evolution process of a meso-crack, using a traditional image processing method has previously been tried, for example the gray mean method, difference CT image method, contour analysis method, isodensity segmentation analysis method, and gradient method . HoweverIn 1847, Delesse et al. first proposed the stereology in the study of ore deposit profiles . The oriStroeven et al. extracted parameters describing the geometric structure of cementitious materials based on stereological 2D and 3D particle shape evaluation methods and constructed a particle shape estimator based on these parameters . JutzeleThe meso-crack occurs usually near the peak strength of concrete when it is clearly active, but it is difficult to obtain CT images of concrete specimens because the peak strength of concrete cannot be accurately predicted. In addition, even if the CT image contains the newly generated meso-crack information, such a meso-crack is hardly going to appear intuitively due to its small size and imaging interference of aggregates and holes .This greatly increases the difficulty of extracting meso-damage information. To resolve this problem, DIC has been previously applied to the identification of meso-cracks in CT images. This method takes the sub-image composed of amount pixels as the basic unit, and it is used to identify the displacement according to the correlation coefficient between the sub-image and reference sub-image. Furthermore, the method is used to obtain the displacement field and strain field of the sub-image inside the loaded concrete, allowing meso-crack evolution process to be judged according to the strain gradient of the strain field.However, this method has too many sub-volume pixels, and the smoothing effect seriously reduces the resolution of CT images. This leads to the unsatisfactory effect of DIC in identifying microscopic cracks in CT images.Holes in concrete are easily to deform under load;Holes are clearly visible in the CT image;The deformation of holes is closely related to the evolution process of the meso-cracks, and relevant concepts can be developed based on stereology. The shape of the holes as well as the change in the hole shapes can be analyzed so that the active area of meso-cracks can be indirectly determined.Aiming to solve the above problem, we begin with three facts about holes:On the basis of the literature survey in The rest of this paper is organized as follows. Meso-damage information can be obtained through concrete CT images, and this is the basis of our study.Emeishan cement , were obtained from Emeishan City, Sichuan Province, China. Guang’an I fly ash were obtained from Guang’an City, Sichuan Province, China. The chemical composition of cement was detected according to China National Standard GB175-2007, as shown in The concrete CT test system is composed of scanning equipment and a loading system, as shown in Install the specimen, and scan the specimen for the first time before applying load, and obtain the CT image of the concrete specimen in the initial state.Set 0.5 kN/s as the load application rate and stop loading when the load reaches 30 kN. Perform the second scan.To prevent any large displacement because of a sudden fracture of the specimen caused by the load control, the load control was changed to displacement control, with loading rate 0.005 mm/s and a target displacement of 0.70 mm. Perform the third scan while keeping displacement unchanged.Set target displacement as 0.85 mm and perform the fourth scan at the target displacement.Set the target displacement as 1.00 mm. However, when the displacement reaches 0.92 mm, the specimen breaks, and the static pressure load rapidly drops to 26.43 kN, and the fifth scan is performed at this load.The specific test procedure of concrete CT test follows the following steps:Loading rate in this study is in line with the China standard , and this is consistent with the ISO standard .According to the displacement and load values of each scanning stage recorded during the test, a stress-strain curve is drawn, as shown in Under the uniaxial static pressure, the cylinder specimen generally shows an upright “v” and inverted “v” combined shape failure, which is mainly caused by the effect of the end friction effect, i.e., the structure effect of the specimen. The specific shape and formation process of the combined shape failure, such as the location of the crack point, the propagation direction of the meso-crack, and the connection mode, reflect the material properties. The combined shape failure mode is a comprehensive effect result from the stress distribution inside the specimen, the strength and deformation of aggregate, mortar, and the characteristics of the joint surface between aggregate and mortar. The meso-crack evolution process of concrete can reflect the meso-mechanical properties of concrete materials and determine the macroscopic strength and deformation characteristics.In An obvious macro-crack appeared on the CT image obtained from the fifth scan, at which point the concrete specimen has damaged. This means that from the material viewpoint, the aggregates, mortar, and holes are clearly visible. CT images provide an effective method to observe the internal structure of concrete, and the resolution can meet the observation needs. However, from the perspective of meso-damage evolution of concrete materials, the resolution of the CT images cannot meet the observation needs.Therefore, it is indispensable to seek appropriate image processing methods to mine the information of meso-crack initiation, propagation, connection, and penetration contained in CT images. In the next section, the methods for extracting the meso-crack information from the CT images of the concrete specimen will be focused on at each scanning stage before concrete failure so that the evolution law of the meso-damage before the peak strength of load will be revealed.To actualize the study of the hole shape, two aspects of the work must be carried out. One is to separate the holes and cracks in CT images, and the other is to find appropriate parameters to describe the hole and crack shapes for obtaining their shape change information of meso-damage at different stress stages.R indicates the degree of similarity between a particle and a circle. This indicator can be used to assess whether or not a hole or crack is close to a circular shape. A larger value of R means more branches of the hole or crack, thinner and longer contours of the crack, and more irregularly. The roundness of any circle is 1, which defines the critical value. The roundness of all other enclosed shapes is greater than 1.In stereology, the quantitative description of 3D structural features of materials is achieved with a 2D projection. ACA is the total area of all holes and cracks on the scanning section, m2; S is the area of the entire scanning section, m2; ACP is the perimeter of each hole or crack in the scanning section, m; n is the total number of the holes and cracks in any binary image.In Formulas (1)–(3), To obtain the appropriate segmentation method of holes and cracks in CT images, three threshold segmentation methods including the minimum cross-entropy thresholding method , fuzzy tA comparative study was preformed to choose the appropriate image segmentation method, as shown in The original cross-sectional CT image a was segTo obtain the essential quantitative information, such as number, length, width, and perimeter of holes and cracks, a program first is compiled to process each hole and each crack in a loop to obtain the position and number of closed holes and cracks, and the holes and cracks are numbered. Finally, the parameters including the length, width, perimeter, and area of each separated connected area in the image are calculated, and the roundness and area fraction of holes and cracks are computed using these parameters.According to Formulas (2) and (3), using MATLAB, the average roundness and area fraction of all holes and cracks are calculated from the binary cross-sectional images taken at different heights of the specimen and under different loading. From The area fractions of the second, third and fourth scan stages are consistent with the area fraction of the first scan stage, with some little change only, indicating that before peak strength all internal holes’ areas do not change significantly. In the fifth scanning stage, the specimen was completely damaged, and this belongs to the post-peak strength stage. The change in the average area fraction at each scanning layer showed obvious differentiation and reached the maximum value at the layer 143. This is because the area occupied by the newly grown cracks in this layer is larger.Comparing and analyzing In this section, the CT images of concrete are divided into equal sections, and the average roundness of holes and cracks at all scanning layers is calculated to study the variation law of meso-cracks in concrete before macro-cracks occur. Six cross-sectional CT images  were uniformly selected along the height direction of the concrete specimen , and forBy analyzing However, the average roundness of holes and cracks in equal divisions of the image is still difficult to reflect the local law of shape change in each individual hole or crack, which is not conducive to predicting the specific and accurate location of meso-cracks.To predict the location of macro-cracks more accurately, the concrete image is divided into either a crack zone or non-cracked zone in this section. The specific partition principle is: (1) Crack zone: this zone is near the macroscopic cracks at the 5th scanning stage (failure stage). (2) Non-cracked zone: this zone is far from the macro-cracks in all five scanning stages.Based on the above zoning principle and former same positions, 30 CT images of the five scanning stages at these six positions were analyzed. The cracked area and the non-cracked zone of the image are divided, and the division result is shown in From the analysis of In the cracked zone, before the peak strength, the average roundness of the holes at the S120 layer decreased slightly. The average increase in the roundness of holes and cracks at the S130 and S140 layers is small. The average roundness of the holes and cracks at the S150 layer has begun to increase, and the downward trend has been suppressed. The average increase in the roundness of holes and cracks at the S160 and S170 layers is significant, and this indicates that the meso-cracks around the holes develop early, eventually leading to the generation of macro-cracks. It shows that the propagation direction of the meso-crack is from the lower part of the specimen upward, which is consistent with In summary, before the failure of the concrete specimen, the average roundness of holes and cracks in the future crack area is monotonically increasing compared with respect to the area without cracks in the future. This means that the average roundness is helpful in predicting future crack areas, in contrast to the efforts using various image processing methods that still cannot help locate meso-cracks before peak strength.Since the initiation of meso-cracks is a process in which cracks occur at one or several points first and then gradually expand, the average roundness of holes and cracks divided into crack and non-cracked zone in the image still has a smoothing effect. The law is not conducive to predicting the specific and precise location of meso-cracks.Concrete CT images contain clear information of the shape and distribution of aggregates, mortar, and holes in concrete. Because the size of initial crack in concrete is small, initial crack cannot be seen in CT image usually. In this section, holes in concrete are considered only. When extracting the roundness parameters of holes, the shape parameter information is gained by taking the average of roundness parameter values of individual holes. Consequently, the effective information about the shape change in each individual hole is suppressed. In this section, the change pattern of the roundness for individual hole under each loading stage will be addressed. For such a purpose, two sections were taken in each of the upper (S70~S120), middle (S130~S170), and lower (S180~S220) layers, and the representative hole numbers were labeled as A, B, C, D, E, and F, respectively .It can be seen from For an individual hole, monotonically increasing the trend of the roundness parameter is an indication of meso-crack activity and thus such information can be used to predict the location of macro-crack. This is more targeted than that predicted by the average roundness of holes in a specific area because it is no longer affected by the averaging effect.In As the stress increases to cause the deformation of the hole, brittle fracture at the mesoscopic level occurs at the periphery of the hole near the final macroscopic crack, and the initiation of the meso-crack causes the hole shape to change and the roundness to increase. In the case that meso-cracks are difficult to observe in concrete CT images, the monotonous increase of the roundness of holes can indirectly reflect and predict the location of macro-crack. This, using roundness of individual holes to avoid the averaging effect, is more accurate in predicting locations of the final macroscopic cracks than using the average roundness for specific regions.As far as the targeting area is concerned, since all the holes and cracks in the area are included, the average roundness is more reliable and stable, but at the same time the effective information of the shape change in a single hole is suppressed. Because the initiation of a meso-crack occurs at one or several points first and then gradually expands, only the shape of the holes near the initiation point of meso-crack changes, which is reflected in the roundness parameter. Because the area of a single hole is small and it is affected by the binarization segmentation method, the true area is not easy to measure, and the roundness value is not as reliable and stable as the average roundness of regional collective holes, which is the limitation of the proposed approach. In the applications, the individual roundness values and the average roundness complement each other.It has much difficulty to obtain the series CT images including meso-crack initiation, propagation, connection, and penetration process of concrete with stress. This is because under most circumstances, meso-crack initiation occurs close to the peak strength of concrete, scan opportunity is difficult to grasp.Finally, we put a note about further studies. To validate the proposed method in this research, more tests of the same type need to be carried out.Before the peak strength of concrete, there is no obvious change rule for the average value of hole roundness and area fraction in the whole cross-section with the increase of stress, but the average value of hole roundness is more sensitive. The averaging of the hole and crack parameters seriously affects the characterization of the regularity in the shape change in individual holes with increasing stress.As the targeting area becomes smaller, it shows that the average roundness of the holes and cracks in the domain gradually change regularly with the increase of the load, and near the macro-cracks, the average roundness of holes has a monotonically increasing trend before the peak stress, suggesting that it is more valuable to analyze the variation law of roundness of individual hole.With the increase of stress, the roundness of individual hole near the location of the macro-crack has a monotonous increase trend, and the roundness of the hole far away from the macro crack has no such regularity, indicating that the roundness of individual holes before the peak strength increases monotonically. The meso-crack activity, which is difficult to be extracted from the image, has a definite correlation with the increase of the hole roundness, and the study of the roundness change in individual holes is helpful to predict the macroscopic crack positions.Since it is difficult for various image processing methods to display the new meso-cracks before the peak strength, the trend of monotonically increasing in holes’ roundness with the increase of stress is an important finding: such a trend prior to the meso-cracks can reflect the future positions of the macro-crack, and indirectly perceive the meso-crack before the peak strength. This is a breakthrough in the crack analysis in concrete CT images. In summary, it has important scientific research value and potential engineering application significance to carry out in-depth research on the change in hole shape in concrete.In this research, the CT test system is used to carry out the concrete static uniaxial compression test, and the CT images containing the meso-damage information of the concrete are obtained. Since the holes in concrete are prone to deformation after being stressed, the minimum cross entropy thresholding method is adopted to segment the holes and cracks in the cross-section CT image of the concrete. The idea is motivated from the stereology principle. The main conclusions of this paper are as follows:


Twistocaloric cooling technology is a novel solid elastocaloric refrigeration to be promising alternatives to conventional compression refrigeration. The transient thermal characteristics of the twistocaloric-effect material and its cooling capacity are critical for this technology. A test rig of the continuous torsional refrigeration system (CTRS) using nitinol wires twisted by a stepping motor was built. The experimental tests show that, the surface temperatures increased as the stepping motor twisted the nitinol wires clockwise, and decreased by untwisting them counterclockwise under the stepping motor speed of 40, 45 and 45rpm. The maximum temperature rise and drop relative to the ambient temperature for the two-twisted-nitinol-wire combinations were 7.1 and 2.6°C, higher than those of 1.4 and 0.6°C for the single nitinol wire, respectively. An optimization program based on a heat conduction model was constructed to attain the potential cooling and heating capacities (PHCCs) of the nitinol wires. Then, PHCCs were introduced into the coupled flow and convective heat transfer model to predict the actual cooling and heating capacities of the CTRS. They were discovered to increase as the number of nitinol wires, the stepping motor speed, and the air velocity. The results can be referred in developing a continuous torsional refrigeration prototype. Refrigeration and air conditioning consume a substantially large amount of energy, accounting for nearly 20% of the world’s energy consumption. The most common type of refrigeration and air conditioning is vapor compression refrigeration, which uses chlorofluorocarbons, hydrochlorofluorocarbons, and hydrofluorocarbons as refrigerants. Refrigerants such as R22 and R134a have high ozone depletion potential or global warming potential, which means that leakage of them will deplete the ozone layer and worsen the greenhouse effect. On the other hand, environmentally friendly hydrocarbon refrigerants or inorganic compounds, such as R600a and R717, are flammable and toxic Therefore, the search for novel alternative refrigeration methods has become essential.52.6Ti47.4) wire had a maximum surface temperature change of −17.0°C at an untwisting rate of 50 turns/s. They also found untwisting polyvinylidene difluoride (PVDF) fibers produced a cooling performance of −1.1 K. However, further studies on the twistocaloric heating and cooling effects are still needed, especially for providing continuous output, and so, the following tasks were carried out in the present work.Solid elastocaloric refrigeration is a new refrigeration technology that could replace conventional vapor compression refrigeration –4. It isA novel continuous refrigeration test rig was constructed using nitinol wires twisted by using a stepping motor.Experiments were conducted to determine the thermal characteristics of the continuously twisted/untwisted nitinol wires.A heat conduction-based optimization model was built to determine the potential heating and cooling capacities (PHCCs) of the wires.A coupled flow and convective heat transfer (CFCHT) model was built to determine the heating and cooling output of the continuous torsional refrigeration system (CTRS).As shown in Specifications of the CTRS are listed in ρ, c, and λ are the density, specific heat capacity, and conductivity of the wire, respectively; t is the temperature; τ is the time; Qv is the amount of heat produced or absorbed per unit volume during the torsion process; and r, φ, and z are the cylindrical coordinates.The heat conduction model of a nitinol wire was built. Nitinol wires are considered infinite cylinders because their diameter is much shorter than their length. Heat is conducted mainly along the radial direction. Therefore, the governing equation isqr is the radiant heat flux density, ε is the emissivity of the material, σ is the radiation constant of the black body, T is the surface temperature of the emitting surface, and Ta is the ambient temperature.The initial temperature was ambient temperature. The wire was involved in the heat transfer between ambient air and radiation. The surface heat transfer boundary equation can be written asqc is the convective heat flux density, h is the convection heat transfer coefficient, which is calculated using natural convection correlations, where the air velocity is coupled with the airflow model [The heat transfer boundary equation of the wire convection heat flux is expressed asow model .Qv during the torsional process in the governing equation is unknown. According to the temperature evolution of the wires in the nitinol–stepping motor unit, Qv in the governing equation is described as Qvd and Qva during loading and unloading, respectively.The Heat disposal by the loaded wire is expressed asQd0, Qa0, k1, and k2 are constants.Heat absorption by the unloaded wire is expressed asTherefore, based on the above simulation program, we built an optimization model  that tooA CFCHT model was built to predict the heating and cooling capacities of the wires in the nitinol wire–stepping motor unit and the module . Air wasThe continuity equation is expressed asThe momentum conservation equations are expressed asρa, ca, and λa are the density, specific heat capacity, and conductivity of the air, respectively; u and v are velocities along the x and y direction, respectively.The energy conservation equation is expressed ash around the wire in Eq  and heating capacity (Qth) of a continuous torsional refrigeration module are as follows:Thus, the cooling capacity  calibrated and validated by the standard thermometer, and the temperature at the midpoint  was set to 8, 12, or 16.The cooling and heating capacities of the nitinol wires shown in The continuous torsional refrigeration module allows the nitinol wires to be loaded and unloaded continuously. Similar to the heat flow inside alloy wires during heat treatment , 27, theThe specific cooling power  and the cooling/heating capacity are two criteria used to evaluate the refrigeration capacity in modern torsional refrigeration and heat pump research. SCP is a suitable index for determining the cooling power density per unit mass of SMAs . The SCPA novel modular continuous torsional refrigeration test rig using twisted nitinol wires was built and experimental and simulation studies were conducted to determine the thermal characteristics, and PHCCs of the nitinol wires during the continuously alternating torsional process. The main conclusions were as follows:The surface temperature increased as the stepping motor twisted the nitinol wires clockwise and decreased as it untwisted them counterclockwise. The thermal characteristics of the wires being twist and untwisted provided a valuable reference point for the zoning of the continuous torsional process and the development of a continuous torsional refrigeration prototype.During the continuous twisting and untwisting of the nitinol wires with a stepping motor, the number of torsional turns and the number of wires significantly influenced the temperature of the nitinol wires. Two nitinol wires being twisted can be used for refrigeration and heating in the actual design of a torsional refrigeration system.The measured temperature variation was used to optimize the PHCCs of the nitinol wires via the optimization model. Subsequently, a CFCHT model was used to predict the cooling and heating capacities. The simulation results reveal that the cooling and heating capacities of the continuous torsional refrigeration device were increased with the number of nitinol wires, the stepping motor speed, and the air velocity. Therefore, the capacity of a module can be improved by changing the number and geometric size of the wires, the number of torsional turns, and the stepping motor speed. Our approach could be valuable for research into caloric materials for torsional refrigerators with air as the medium. Our subsequent work for CTRS will include selecting materials with a higher twistocaloric effect, improving the module compactness, increasing capacity, and reducing energy consumption, thereby realizing this approach for making the next-generation domestic, commercial, and industrial refrigerators.


Durability is an essential aspect of the lifetime performance of concrete components. The adequate surface quality and thus the service life of concrete can be achieved, among other things, by appropriate curing during hydration. To measure and control the curing quality, appropriate procedures are required. Gas permeability allows conclusions to be drawn about the porosity of concrete, which has a significant impact on durability. In this contribution, the effect of different curing methods on gas permeability is presented with the help of laboratory and on-site tests, showing that inadequate curing leads to increased permeability in the near-surface area of concrete. The measurement results of concrete samples and components with the same composition but varying curing treatment are compared and evaluated. Influences such as concrete composition and environmental factors on the quality of concrete are observed, and recommendations are made for a reliable assessment of the surface quality as a result of the investigated curing measures. In the past, it was assumed that concrete structures are maintenance-free if certain basic rules of concrete technology are followed. The experience of the past decades, however, showed that only minor deviations from these rules as well as incorrectly assessed or harsh environmental conditions can lead to considerable damage . Due to Curing concrete is the lowest of low-tech operations… it is seen by many as a silly operation, a non-job…and bad curing does not show…. If I emphasize ensuring curing, it is because curing can make all the difference between having good concrete and having good concrete ruined by the lack of a small effort’.The curing of concrete is essential for the durability of a structure . VariousDifferent to bad compaction that ‘shows’, lack of curing does not show; therefore, the finding of test methods for proving sufficient curing is of great interest.Numerous methods are already cited in the literature to evaluate the curing efficiency. In addition to standardized methods such as the determination of the abrasion resistance , the comVarious non-destructive methods are already being used to assess the durability of concrete structures, such as computer tomography, radar techniques and ultrasonic testing . There iMany of the methods mentioned are associated with great effort or represent the curing effectiveness inadequately. Therefore, the objective of this contribution is to present a non-destructive, simple, and low-cost test method for curing quality control.Durability-oriented design of the structure, e.g., keep away from attacking substances and water;Correct selection of the concrete raw materials and a concrete composition suitable for the job;Proper production and processing techniques, especially curing of the concrete;Passive protection of the concrete, e.g., by impregnation, coating .According to , durabilThe concrete cover needs to be as impermeable as possible to achieve a proper resistance against chemical and physical attack of the reinforcement steel, such as chloride and carbon dioxide . TherefoKeeping the concrete in the formwork;Covering the concrete surface with foils;Wetting the concrete surface;Application of an effective curing compound ,22,23,24The following methods are suitable for proper curing of the concrete surface, and they can also be combined:Concrete mixture composition;The composition and physical properties of the cement and aggregates;Curing quality ,32,33;Degree of hydration or age;Presence of microcracks;Presence of surface treatments;Moisture content at the time of the test ,34,35.The durability of concrete depends heavily on the tightness of the concrete pore system, which, according to , can be Gas permeability is, therefore, a relevant durability indicator for the tested concrete .The procedure for collecting and evaluating gas permeability data for determining the durability of the concrete surface is described in the Swiss standard SIA 262/1: 2019 .A two-chamber vacuum cell composed of two concentric chambers ;A control system, consisting of valves, pressure sensors and a pressure regulator that keeps the pressure of both vacuum chambers balanced during the measurement (Pe = Pi) .As shown in In the inner test chamber (Ø = 50 mm) and the protective external ring surrounding this chamber, both of which are open toward the concrete surface, a vacuum is generated using a vacuum pump. Depending on the concrete and the measuring device, the vacuum is approx. 10–40 mbar. At 60 s, the inner chamber is isolated from the vacuum pump, which is the moment at which its pressure begins to build up due to the gas flowing through the concrete. The gas permeability is calculated from the change in pressure over time and other parameters. The purpose of the protective ring surrounding the test chamber  is to ensure that the gas only flows into the test chamber in one dimension, which means that it only comes from inside the component see . For lab2, corresponding to the intrinsic coefficient of permeability of the material, and it is calculated with Equation (1) according to [cV = volume of the inner test chamber (m3);A = area of the inner test chamber (m2);μ = dynamic viscosity of air (Ns/m2);ε = open porosity of the concrete (-) which, by default is taken as 0.15;aP = atmospheric pressure (N/m2);P = increase in effective pressure in the inner chamber between time t0 and ft (N/m2);Δt0 = time at which the increase in pressure is measured (s);ft = time at which the test is finished (s).In the case of in situ tests, it should be noted that according to , the tesrding to .(1)kT=. On the other extreme, being unprotected under an ambient temperature of 30 °C and a lower relative humidity of 40% should simulate more extreme conditions for “bad” curing. As can be seen in Since there is the possibility of measurement deviations due to the application of different gas permeability devices, two devices were used for the measurements in order to compare their results, including the PermeaTORR device from Materials Advanced Services  and the Before the start of the measurements, the instruments were calibrated at least two times, until the recorded maximum pressure did not exceed 5 mbar nor did it differ by more than 0.5 mbar from the previous calibration measurement, according to .A minimum of three faces per sample were measured, including the top surface that was not covered by the formwork during concreting and two lateral faces that were protected by the formwork. The measurement of two “formwork faces” was considered sufficient, since the scatter of the results between two faces is very small, and a further measurement would change the standard deviation only slightly.As recommended in , the moi−16 m2 are entered as points on a logarithmic scale also showing segments representing ± the standard deviation of the logarithms of the results. A high gas permeability corresponds to a poor surface quality and vice versa. All results of a series are summarized in a separate graph for further analysis. Series B3, B5 and BS1C Plus data are shown in According to , the resClear differences in the results of the three curing types of the samples of concrete type B3 are visualized in The Proceq permeability tester (blue symbols) was only used on samples with 7 days of curing. By comparing the results of the two gas permeability devices used, it can be seen that the kT values of the Proceq device are generally higher, which was a difference that was detected also by other researchers .In parallel to the gas permeability measurements, the moisture content (%) of the samples was recorded according to 2, while the strength of the “bad” cured samples is the lowest with only 36.5 N/mm2.An influence of the curing can also be demonstrated by determining the compressive strength after 28 days. The last column of As shown in −16 m2. Samples with no curing, such as the samples with “good” curing, are in the good surface quality range with slightly higher kT values between 0.01 and 0.1 × 10−16 m2. The results of the “badly” cured samples are in the middle to bad quality range reaching from 0.2 to 5 × 10−16 m2 depending on the curing duration and the used device. Especially, the top surfaces  in order to check the influence of the environmental conditions and the concrete composition on the measurement results.The first on-site investigations were carried out during dry and warm weather conditions on a concrete wall at a construction site of a railway passage of the Austrian Federal Railways in Obersiebenbrunn (48°14′43.6″ N 16°42′14.1″ E). The wall was executed with the Austrian type of concrete BS1C, which was composed according to Different curing areas were prepared by dividing the west-facing side of the 4 × 11 m large concrete wall into three parts, each of which was given a different curing treatment by the construction company. A distinction was made between “good” (curing A), “moderate” (curing B) and “bad” curing (curing C). The area with “bad” curing was left in the formwork for one day with no further treatment afterwards. The formwork of the “moderately” cured area was removed after four days, and the “good” area was left in formwork for seven days. Both the “good” and the “moderate” areas were encased in fleece for three days after removing the formwork and were sprinkled with water in the mornings. The outside temperature during the curing period was on average 22.5 °C, and the air humidity was 67.3%. The gas permeability tests on the concrete wall were carried out 13 days after concreting.As pictured in As performed in the laboratory, the measurements were carried out with both the PermeaTorr and the Proceq devices. The results of the two devices are shown separately in The results of the construction site tests show that the quality of the curing can be measured under natural environmental influences by means of gas permeability. It can also be seen that exposure and environmental conditions have an impact on the development of concrete quality.Another series of tests was carried out during cooler weather on the concrete walls of a sedimentation basin at an Asfinag (Austrian highway operator) construction site near Göttlesbrunn (48°03′55.3″ N 16°41′46.0″ E). The concrete walls were cast with Austrian concrete type B7 as described in Same as for construction site object 1, three areas with varying curing treatment were prepared. The curing for these tests was carried out on differently oriented areas. According to The measurements took place when the concrete was 15 days old. The average outside temperature from concreting to the day of measurement was 6.5 °C. The humidity was relatively high at 84%.Due to the prevailing damp weather, the moisture content of the structure was also measured. With 2.5%, the moisture content was below the maximum recommended value for gas permeability measurements. The low moisture content in the concrete was attributed to the strong wind conditions.−16 m2 with ± the standard deviations of the logarithms for each area. The tendency that the surface quality is impaired with increasingly poor curing is also confirmed in this series of tests. The values in the “good” curing area A show a very good to good surface condition, while the poorly treated wall area C only achieves middle quality. A good surface condition could be demonstrated through “moderate” curing. The results of “good” and “moderate” curing are very close to each other. It can be assumed that the favorable location of the area of curing B had a positive effect on hydration due to the adjacent moist soil, while curing A is more exposed and is therefore less protected from wind and consequently less protected from drying out. The stronger solar radiation on the southwest side in area A could be considered as a further aspect, which would also promote dehydration. However, due to the cloudy circumstances, solar radiation plays only a minor role in the period from concreting to the day of measurement. The variability of the kT data, for the three curings  was extremely high, which was possibly due to the young age and exposure conditions prone to the development of microcracks; this experience indicates that taking at least six readings on each test area, as defined in the Swiss standard SIA 262/1: 2019 [Three measurements were made per curing area with the Proceq permeability tester. The results in /1: 2019 , is recoThe laboratory tests show that the influence of the curing quality on concrete can be detected by determining the gas permeability. Concrete samples of the same composition have different properties due to different curing treatments. Sufficiently cured concrete has a lower gas permeability than untreated or insufficiently cured concrete. Furthermore, the compressive strength is reduced for laboratory samples with increasingly poor curing treatment. In addition to the curing quality, other factors, such as the composition of the concrete, are also decisive for the quality of the concrete surface. Therefore, the results of the examined types of concrete differ from each other when the curing treatment was carried out in the same way. While the concrete type BS1C Plus generally had higher kT values in the laboratory tests, the results for type B5 were significantly lower. Nevertheless, the trend of decreasing gas permeability with higher curing quality is reflected within all examined series.It is not possible to set a general kT value as a threshold value for adequate curing. Rather, test results already collected for different types of concrete represent guide values for further measurements.Different curing quality could also be clearly identified on the construction site. The same effect was found there as with the laboratory samples. Longer or better curing treatment had a positive effect on the concrete quality and thus lowered the gas permeability. However, the results of the construction site tests cannot be directly compared with the laboratory results, as the climatic conditions, the type of curing and the concrete composition differed.When evaluating the quality of curing on a structure, numerous other factors are responsible for the surface quality of concrete in addition to the composition of the concrete. The gas permeability of structures on site was not only influenced by the concrete composition and curing quality  but also by exposure to wind, solar radiation and precipitation. Concrete surfaces exposed to sunlight and wind showed a higher gas permeability than surfaces that were protected against these influences. Environmental influences can have both positive and negative effects on the hydration of the concrete. Their effect is reflected in the results of the gas permeability.In addition, when determining the gas permeability, the age of the concrete must be taken into account, which according to the Swiss standard  has at lSince a single gas permeability measurement only captures a small sub-area, several measurements need to be carried out for the overall assessment of a component in order to achieve reliable results. The measurements should not be carried out before the concrete is 14 days old, as young concrete still has a very high level of moisture, which may falsify the results. In addition, the humidity of the investigated component should be determined before each permeability measurement so that the recommended limit humidity of 5.5% is not exceeded. If the limit of 5.5% is exceeded, it is advisable to repeat the measurements later once the concrete has dried sufficiently.As already mentioned, no general recommendation for a limit gas permeability value for sufficiently cured concrete can be given. A possibility for evaluation of the results is the use of the permeability classes approach from  as guideIn the research work presented, different curing treatments were compared under otherwise almost identical conditions. It was found that the type and duration of curing has a strong influence on the gas permeability and, subsequently, on the durability of the structure. Thus, the quality of the curing of concrete structures can be measured indirectly by determining the gas permeability.This method is characterized by the simple and non-destructive implementation of measurements both in the laboratory and on the construction site. The evaluation of the results is quick and uncomplicated. Recommendations for the representation of the permeability values and the assessment of the surface quality are already available.Investigations in the laboratory have shown that the gas permeability measurement method is a promising and reliable method for evaluating the curing quality of concrete.The comparison of a “good” with “no” or a “poor” curing treatment is reflected in the permeability coefficient. In addition to the curing conditions, the gas permeability also depends on the composition of the concrete, which is why no general limit values can be specified for the curing quality evaluation.The higher permeability due to inadequate curing is accompanied by lower compressive strength than for optimal curing.The construction site tests show that the gas permeability measured directly on the structure also provides reliable information on the curing quality of concrete.Environmental influences play a major role in on-site measurements, since the concrete quality can be influenced both positively and negatively by factors such as wind, temperature, and humidity. For this reason, these factors must be considered when selecting the measurement points, the time of measurement and when evaluating the curing quality.For site testing, it is recommended to perform at least six individual measurements of kT per testing area, as set in the Swiss standard SIA 262/1:2019 .In summary, the following main statements could be derived from the investigations carried out:As the measured permeability coefficient not only depends on curing conditions, but also on the type of concrete and other influencing factors, a direct measurement of the curing quality is not possible. One possibility would be to set a limit value in the planning phase as a minimum requirement for achieving the desired concrete quality. This limit value could be determined on the basis of reference measurements on similar concrete components with the same compositions. To implement this approach, however, further comprehensive investigations would be necessary in order to obtain a sufficient sample size for a reliable determination of these limit values.In a follow-up research project, further investigations are currently being carried out on concrete structures with different properties and under varying climatic conditions with gas permeability measurements to evaluate the curing quality. At the same time, reference values are collected from test samples with the same formulation and optimal curing conditions for evaluating the construction site results. This promising study still requires extensive research to determine the reliability of this type of assessment.