The presented research project anticipated the determination of strength for samples in various cross-sections at the height of elements and destructive strength in the strength testing machine. It was confirmed that for standard and big borehole samples, it is not possible to test the strength of concrete in the top layer of the floor by destructive methods. This can be done using the ultrasonic method. After the analysis, certain types of distributions of strength across concrete floor thickness were chosen from the completed research program. The gradient and anti-gradient of strength were proposed as the new parameters for the evaluation of floor concrete quality.The accepted methods for testing concrete are not favorable for determining its heterogeneity. The interpretation of the compressive strength result as a product of destructive force and cross-section area is burdened with significant understatements. It is assumed erroneously that this is the lowest value of strength at the height of the tested sample. The top layer of concrete floors often crumble, and the strength tested using sclerometric methods does not confirm the concrete class determined using control samples. That is why it is important to test the distribution of compressive strength in a cross-section of concrete industrial floors with special attention to surface top layers. In this study, we present strength tests of borehole material taken from industrial floors using the ultrasonic method with exponential spot heads with a contact surface area of 0.8 mm Composite materials belong to an exceptional group because it is difficult to control grain distribution in the material being formed. The most characteristic example of such a composite is concrete, the most broadly used among them in the construction industry. Tests of this material concern both spatial structure  and its basic parameter, that is, compressive strength. Modifications of this composite aim at the improvement of its homogeneity ,2,3,4.The industrial floor belongs to those building structures in which concrete should be of the highest quality in the top layer because it is exposed to considerable abrasion, local pressure, impacts, etc. Often, the top layer of the concrete floor quickly crumbles  and streStrength tests on borehole material of small diameter and height, cut out from various depths, indicate often considerable weakening of concrete in the top layer compared to strength determined on samples cut out from a deeper layer. This problem was noticed in the European standard , highligIn calculation theories, concrete is usually treated as a homogeneous entity, specified often as quasihomogeneous, at least in the macroscopic sense. The question of the actual heterogeneity of concrete remains open for several reasons. The most important reason is that the accepted test methods do not favor recognition of its heterogeneity. According to the binding standard , they arThe heterogeneity of strength for elements with a large height dimension, such as pillars and vertical partitions formed in the built-in position, was the subject matter of a publication. Research showed a weakening of concrete in their horizontal cross-sections along with an increase in the measurement height. Tests conducted during the period from 1962 until 1978 in Japan  on concrinternal, which is characteristic for stocky cross-sections formed in the vertical position,superficial, which is observed in the case of laying floors and elements of small thickness in the horizontal position.Khatib and Mangat showed that the cement pastes formed horizontally can have the pore volume twice as large near the top layer than near the bottom layer. Pores near the top layer are also considerably larger (from 46% to 98% of pores above 0.1 µm) than pores near the bottom layer (from 38% to 80% respectively) . The weaTopics regarding strength distribution at the height of stocky cross-sections formed in a vertical position are researched, described, and characterized in the technical and scientific literature. Superficial bleeding, the homogeneity characteristics of near-surface structures, and strength distribution for concrete floors in thin layers are not topics broadly described in the scientific literature. Information about mathematical criteria used to describe strength variability in industrial floors is also missing. Cases of superficial damage to the floors which are the subject of this study are frequent, therefore the authors undertook such research.The research project assumed that the analysis would be carried out on samples from borehole materials taken from various regions of the country to avoid any potential material-related errors connected with, for example, the aggregate source. The floors were constructed of concrete class C25/30 and C30/37. Borehole materials with diameters 80 and 100 mm were provided, 6 pieces from each tested floor. They came from floors that were not superficially hardened, from floors with surface hardened using mineral agents and also with resin flooring .The hardened layer in certain areas of the halls became loosened which is regarded as an emergency condition .The presented damage indicates substrate hardening of low strength (weak concrete).UPV), elastic modulus (E), and Poisson’s ratio (ν) were researched and described [LC) is proportional to the square root of the dynamic modulus of elasticity (dE), and inversely proportional to the square root of its density (ρ) in Equation (1):dν is the dynamic Poisson’s ratio. The dependency in Equation (1) applies to homogeneous and isotropic materials. Concrete is a heterogeneous material. High attenuation in concrete limits the UPV method to low frequencies (up to 120 kHz). Under this condition, ultrasounds do not interact with most concrete inhomogeneities [cf) and UPV [The compressive strength of concrete samples in their various cross-sections was determined with the use of the non-destructive method calibrated with the destructive tests of the samples. This type of examination is being widely used for the range of building materials, such as concrete, wood, steel, ceramics, and for the diagnostics of building structures ,23,24,25escribed ,28. Passeneities  and it ceneities . Scienti and UPV ,34,35,36 and UPV ,37,38. K and UPV . In the  and UPV ,40.At the beginning of the tests, the borehole materials were first cleaned and dried to air-dry moisture according to the standard . TestingIn subsequent batches, the top zone of the floor at the thickness of 3–4 cm was examined in more detail. The planes in which measurements were conducted were compacted, at first every 5 mm, and in certain series every 2 mm .Such densely located planes for measurement of the ultrasonic impulse were possible because the diameter of the ends of the spot heads used was only 1 mm .ϕ = h . To the pulse velocity determined in the middle of each sample height, compressive strength determined on the strength machine as a relation of destructive force P (N) to the surface area of cross-section A (mm2) of Equation (2) was assigned:Boreholes were cut thus obtaining samples with cf (MPa) and mean ultrasonic wave velocities LC (km/s) from two testing directions  was approximated for the measurements of the first concrete type shown in The approximation of the scaling curve in Equation (3) was performed based on the results of destructive tests conducted on cylindrical samples with dimensions 10 cm × 10 cm. The results of destructive tests, measured pulse velocities, and strength values calculated using Equation (3) are presented in Scaling curves for the remaining tested boreholes of the floors were approximated in the same way. Scaling curves established hypothetically were used to convert the rate of ultrasound wave in the given cross-section at the borehole height into concrete compression strength in this cross-section.The tested borehole materials provided an answer to the question of the distribution of concrete strength across the thickness of industrial floors in the tested facilities. Ignoring minor fluctuations of strength at different levels resulting from random positioning of aggregate or small defects in the concrete structure, or errors in measurement of the distance (the head ends got inside surface pores), all results can be grouped according to the summary below.t (µs), wave velocities LC (km/s), and compressive strengths cf (MPa) in planes parallel to the surface of the boreholes are presented in Passing times Distribution of compressive strength in the tested concrete at the sample height is presented in Fluctuations across the average strength values . The borehole materials were taken from an industrial floor 21 cm thick. Results are presented in The distribution of compressive strength for the tested concrete at the height of the sample is presented in The concrete was relatively homogeneous across the floor thickness. The weakened top layer was 30–50 mm thick. Compressive strength in this layer of concrete drops from the value of 34–40 MPa down to the value of 24 MPa in the near-surface cross-section.The bottom layer of the sample was significantly strengthened. Measurements made at a height of 2 mm from the bottom of the sample showed an increase in strength to 46 MPa from 35–40 MPa in close layers above.The borehole materials were taken from an industrial floor 15 cm thick. Calculation of compressive strength from ultrasound wave velocities was done with the use of Equation (4).Results are presented in The concrete across the floor thickness changed its strength along with the change in the measurement plane. The top layer with a high thickness (up to 50 mm) became weakened very quickly in the direction of the floor top. The distribution of compressive strength for the tested concrete at the height of the sample is presented in To improve the hardness of the top layer of the floor, powders made of hardening materials based on a cement binding agent and strong filler were used. If the strength of the hardened concrete had characteristics in the vertical cross-section similar to the one described in The result of measurements regarding ultrasonic wave velocity and compressive strength in the sample’s cross-section is presented in Distribution of strength in cross-section of the sample taken from the floor with the hardening layer made as expected  is preseThe superficially weakened floor, with the compressive strength of 25–30 MPa, strengthened in the near-surface zone up to the designed value of 30 MPa. Repair efficiency depends on the weakest cross-section under the strengthened layer and its ability to transfer shear stress arising because of the shrinkage of the strengthened layer. In the lower zone of the sample (2 mm from the bottom of the floor) the concrete was strengthened to a value of over 40 MPa. The concrete strengthening zone was about 20 mm thick.the case of strengthening the top layer with too small a quantity of mineral powder,the case of strengthening the floor with too weak a top layer of concrete,the case of excessive strengthening of the top layer of the floor.As far as concrete floors strengthened (and hardened) using the mineral powder under emergency conditions are concerned, three types of strength distribution were analyzed:Distribution of strength in cross-section of a sample taken from the floor in which too small a quantity of hardening powder was used is presented in 2.In this case, the compressive strength drops from a value close to 30 MPa at a depth of 5 cm from the top of the floor to 16 MPa in the zone close to the surface of destruction. The destruction occurred in the weakest layer of concrete, where strength reaches a value of not more than 16.3 MPa. In the reinforced surface plane, the strength increases to 19 MPa at a depth of 3 mm from the top of the floor. The mineral strengthening of the floor, in this case, should reach a depth of 25–30 mm, at which the concrete strength was at a minimum level of 20–25 N/mmLC and strength cf described using Equation (6) was used for calculations of the distribution of strength in the sample’s cross-section.The strengthening will be ineffective also in the case in which concrete below the zone affected by the mineral powder is too weak and the entire strengthened layer is loosened. Measurements of ultrasonic wave velocity in cross-section of a sample taken from such a floor are presented in The distribution of strength in cross-section of the tested sample is presented in In this situation, the strengthening was ineffective because directly under the mineralized layer, with a strength of 20 MPa, the concrete was very weak, its strength decreases down to the value of approximately 5 MPa near the surface of destruction, and then increases up to the designed value of 30 MPa.The floor reaches the highest strength value at the last measuring point, 1 cm deep from the bottom edge. The reinforcement was even at a thickness of 4 cm from the bottom, where the measured strength was 28 MPa and reaches 40 MPa in the plane at the bottom of the sample. The effect of concrete strengthening in the lower planes of industrial floors  usually A similar effect of damage to the hardened floor occurs if excessive powder is used. Measurements regarding ultrasonic wave velocity for a borehole material from such a floor are presented in The distribution of strength in the cross-section of the tested sample is presented in In this case, the strength of the top layer exceeded the designed value. The measured strength of the borehole material in the middle of the sample’s height has a value of approximately 30 MPa. Considering the possible weakening in the upper zone, the concrete was excessively strengthened with mineral powder. After strengthening, in the near-surface zone, the strength value increased up to 40 MPa, and below the strengthened zone it drops down to the value of 13.5 MPa. In the destruction zone, in which it was impossible to make a measurement, the value of strength was lower than 13.5 MPa—a value measured from its nearest surface (2 cm from the top of the floor). Considerable shrinkage in the place of contact between the layer with increased strength and the weakened layer lead to loosening .The various situations involving floor concrete weakening in the top layer shown above, as well as successful and unsuccessful strengthening using hardening powder, explain the causes of the defects and the effects of the ‘repairs’. The examination of concrete strength distribution across the thickness of the floor was possible thanks to the applied ultrasound method with spot heads.The interpretation of the results obtained from tests of concrete strength distributions across the thickness of the floor presented above is satisfactory, however, no reference documents or admissible values regarding strength variability in a cross-section of concrete slab elements are available concerning this. The subsequent section presents a proposal of additional criteria for assessing concrete in floors and an attempt to indicate mathematical criteria ensuring the basis for evaluation of strength changes across the thickness of the tested concrete layer based on the strength values and the rate of change of strength values obtained from measurements of ultrasonic wave velocities.The gradient of the scalar strength field indicates the direction of the quickest growth of strengths in individual points. The modulus (that is ‘length’) of each vector in such a field is equal to the rate of strength field growth in the given direction. The vector opposite to the gradient is sometimes called an anti-gradient. The strength gradient is a vector value and its unit in the SI system is pascal per meter (Pa/m). Due to the range of the measured strength gradient values for industrial floors, the unit MPa/cm is used for the description of them.c,2f is concrete strength in plane 2 (closer to the top surface of the slab); c,1f is concrete strength in plane 1 (closer to the bottom surface of the slab); Z2—distance of the second measurement plane from the bottom of the slab; Z1—distance of the first measurement plane from the bottom of the slab.In the considered case of the strength field test, you can refer to a vertical strength gradient that corresponds to a strength change in line with the distance from the bottom of the slab (with the height of the measurement plane). The strength gradient between two measurement planes 1 and 2 can be expressed using Equation (8):cf is 0.7 MPa/cm apart from local fluctuations, and in layers located closer to the top surface it changes quickly . In the zone of powder-based hardening, the strength begins to increase (∇cf = +0.5 MPa/cm). Changes in the strength of concrete in the areas of fluctuation around the average value  upwards, to the zone of strengthening  in the case of hardened floors or to the floor surface when there is no strengthening zone;∇c min,10 mmf—on a thickness of 10 mm up from the place of onset of a rapid decrease in strength in the near-surface area (20–50 mm from the top of the floor);∇c,maxf—gradient of strength increase in the hardening zone, relevant to the floors treated with a surface hardening agent.∇At a depth of 0 to 10 cm counting from the bottom of the slab, ∇A summary showing described strength gradient parameters together with measured extreme and mean values of compressive strength of tested samples is presented in if their minimum compressive strength measured in cross-section is considerably lower than the designed value;if their compressive strength in the surface zone is lower than its service load;if the strength gradient for the top, hardened layer exceeds the value of shear strength of concrete. Shrinkage in the place of contact between the level of concrete with increased and weakened strength leads to loosening.Apart from the minimum, mean, and maximum values of compressive strength in cross-section of industrial floors, the strength variability dynamics can be, in this case, described using the value of strength gradient and anti-gradient, which is especially important for the distribution of strength for near-surface concrete layers. The floor should be made using concrete of a specified class and with strength variability gradient at as low a level as possible, guaranteeing that its performance features are maintained during use. The quality of concrete in an industrial floor can be in this case specified using not one but two parameters. The presented examples of strength distribution in the floors indicate that crumpling and cracking in industrial floors used in a standard way usually occur in the following cases:Presented measurements of concrete floors require further research, also with the use of different measurement tools. A discussion of a wide pool of strength distribution results is needed, based on which it may be possible to determine the limit values of the measured concrete strength gradients that can be used to standardize the quality assessment of industrial concrete floors. In the future, it is also planned to carry out measurements of ultrasonic wave velocity and strength distribution in the different concrete constructions formed horizontally to compare them with the results presented in this article. The obtained values of reduced compressive strength in the upper zone of concrete elements are also important in the case of bent reinforced concrete slabs, in which it is advisable that the top zone is not weakened.Despite meeting the requirements for industrial floors tested by the standard method, local fluctuations in compressive strength values in surface cross-sections are a frequent reason for their failure conditions.In industrial floors made of concrete without surface hardening, the weakest layer is the top layer 10–50 mm thick. The strength of such thin layers can be tested using the ultrasound method with spot head on borehole materials taken from the structure.c ≥ 20 MPa).Determination of the distribution and dynamics of concrete compressive strength changes throughout the entire cross-section allows, for example, for the establishing of the thickness of the layer which must be removed during repair of the floor. The reconstructed layer must be laid on concrete having the necessary strength (typically fConcrete floors analyzed in the article can be divided into three types based on the curve showing the distribution of strength across their thickness. In this case, the one-parameter evaluation of concrete in the floor, based on the standard destructive compressive strength tests, is not sufficient. The addition of a parameter, which is a strength gradient, was proposed. Floor concretes can be controlled based on the tests of concrete compressive strength class and its gradients across the floor thickness.


Textile reinforced concrete (TRC) is an emerging construction material with interesting potential concerning sustainability, providing corrosion-free and lightweight solutions. Ordinarily, fiber bundles, impregnated with resin, are used. In this research the performance of reinforcement with unresin fibers is investigated. Control of cracking is considered the key performance factor and is assessed through tensile testing. However, economic and environmental aspects are addressed as well. Then, four different mixes/matrices were considered, without the addition of special/expensive admixtures. TRC ties were subject to direct tension tests, with load and deformation monitoring to assess the influence of mechanical reinforcement ratio on the cracking, failure and toughness of these composites, as well as of the matrix properties on the maximum load. It was observed that at a macro-level TRC behaves like conventional reinforced concrete, concerning crack control. Based on the maximum loads attained at the different composites, it was found that this particular TRC is economically viable. It is suggested that matrix workability may influence the maximum load. Reinforced concrete structures have a major role in the construction of buildings and infrastructures. Ordinary concrete is a very versatile material, adaptable to complex geometries, economic and manufacturable on site. However, it has a brittle behavior and limited tensile strength. To overcome these drawbacks, it is often reinforced with steel, which is ductile and has good tensile strength. In conventional reinforced concrete, steel bars are embedded in concrete in strategic positions, to optimize its reinforcing effect. This solution makes the production process more complex, as it is necessary to properly place the reinforcement and brings a significant problem: steel corrosion, which impairs the durability of conventional reinforced concrete elements. To mitigate these problems, several alternatives have been tried.To diminish the complexity of the production process, long/continuous reinforcing bars may be replaced by short/discontinuous fibers, added to the concrete at the mixing stage, together with the other concrete constituents. This solution is called fiber reinforced concrete. Although it eases the production of concrete and provides some tensile strength, the reinforcement efficiency is limited, as fibers are randomly dispersed in the concrete, while the acting stress fields generally have preferential directions. Thus, to have an equal resisting bending moment in a conventional reinforced concrete beam and in a fiber reinforced concrete beam, a higher reinforcing ratio is required in the latter. Furthermore, the mixing and placing of fiber reinforced concrete with fiber volumes required to achieve current resistant bending moments is impractical. Only special production techniques, like SIFCON , allow sTo avoid corrosion problems, stainless steel or epoxy-coated steel bars or fiber reinforced polymer (FRP) rods have been used instead of carbon steel rebars ,3. The tTextile reinforced concrete (TRC) is a composite material that consists of conveniently aligned continuous high strength fibers and fine-grained concrete (matrix). Even though the most common designation is TRC, the usual maximum aggregate grading ranges between 1 and 2 mm ,8. Then,st century, two research centers were established in Germany, with the purpose of carrying out research and development on TRC [Research on the reinforcement of cement-based matrices with long/continuous fibers started on the 1960s  mention t on TRC .Within the major features of TRC are the absence of corrosion problems and the ability to adapt to complex shapes, due to reinforcement flexibility . The facTRC has been applied in the production of façades, roofing and wall panels ,15,16, pn filaments is n times the response of a filament. If the bundle is impregnated with resin, its strength varies from 35 to 60% of the strength of a single filament [Commonly, reinforcement in TRC is provided by prepreg fibers. This means that the fibers are pre-impregnated with a resin. With this, a group effect is generated within a bundle of filaments and higher strengths are attained. The strength of an unresin bundle ranges between 10 and 25% of a single filament strength . This hafilament , dependifilament . Besidesfilament ,30,31.However, unresin carbon fibers have some advantages over impregnated fibers, such as being less costly, lighter, less susceptible to high temperatures and easier to adapt to complex geometries. Moreover, the use of resins raises eco- and human toxicity concerns. Studies have proven that Bisphenol A, used in the production of resins, even in low doses, causes alteration in brain chemistry and the immune system, among others, in several animal species .At the beginning of the 2000s, there was some investigation of concrete reinforcement with unresin continuous carbon fibers ,33,34,35One key for sustainability is the optimization of civil engineering materials. This optimization must be fostered through application and design.Concerning application, different materials can be considered for one construction. The advantages and disadvantages of each solution will be weighed, to ensure the most appropriate choice. Lightly-loaded or non-load-bearing elements, where element thickness is ruled by minimum reinforcement cover requirements (if reinforcement is provided by steel bars), is where the replacement of conventional reinforced concrete by TRC brings more benefits. Further, these elements are generally precast. One of limitations of TRC is that its production on site is not recommended . TherefoIn the context of fiber reinforced concrete design, a common parameter is the critical fiber volume. This parameter, the amount of fiber per unit volume required to resist the cracking load, is also considered for TRC. According to Hartig et al. , if the Still fostering sustainability, the current design will also seek materials inherently nontoxic to biological systems and for the reduction of waste.Therefore, the aim of this investigation is to resume the research on TRC with unresin fibers, instead of prepreg fibers, which are hazardous to health and more difficult to recycle. Contrary to what has been found in the literature, the main focus is set on the minimum reinforcement ratio for control of cracking, as it is the ruling design criterion for the excellence cluster of TRC applications. Still aiming at the optimization of benefit vs. cost, and also in opposition to what has been found in the literature, the addition of special admixtures to the matrix and even microfibers, which have been proven to enhance TRC performance ,39,40,41Developing suitable TRC with unresin fibers is expected to bring economic, environmental and health benefits. This suitability will be evaluated through the tensile behavior of the tested composites. An original system to transfer the load from the testing machine to the specimens is essayed.Although it is claimed that TRC may be more economical than conventional reinforced concrete, a literature review did not reveal any explicit cost analysis. Therefore, the experimental assessment of the tensile behavior is followed by an analysis of economic and environmental costs.Hereunder, the most relevant characteristics of the materials used in this research are presented. Information is also provided about specimen manufacturing and testing.3. Fine and coarse natural siliceous sands with a specific gravity of 2.63 g/cm3 were used. Cementitious matrices composed of cement, sand, water and superplasticizer were designed. The cement type was CEM I, ordinary portland cement, of the strength class 42.5R, conforming to EN 197-1 [The criterion to define the different mixes was to obtain an increasing matrix strength (from A60 to A35). In this way, decreasing mechanical reinforcement ratios were achieved, keeping the tensile specimen dimensions constant and the amount of reinforcement as well see . The pro3, elasticity modulus of 240 GPa and tensile strength and elongation at break of 4 GPa and 1.7%, respectively.To reinforce the matrix, carbon fibers  were used. These fibers were produced from oxidation and carbonization of polyacrylonitrile (PVA) fibers, supplied in a bundle with linear mass of 3300 tex, containing 50k filaments with a 7 μm diameter. According to the producer information, these fibers have a specific gravity of 1.81 g/cmf). Following Colombo et al. [l) and fiber specific gravity (γf) throughThe received fiber was subject to direct tension tests, carried out on bundle sections. To prevent shear rupture of the fiber, steel wool bits were placed between the bundle and grips . A displo et al. , that ar2 for Af is found, and a corresponding tensile stress of 1.06 GPa is computed. Therefore, the bundle efficiency is 0.25.From this, a value of 1.83 mm3 were cast in steel molds, compacted by means of a vibrating table. After demolding (at 24 h) these specimens were kept in water at 20 °C. Further, four 15 × 35 × 500 mm3 ties were cast for uniaxial tensile testing. The dimensions of the ties are within the range found in the literature [For each mix, three prisms of 40 × 40 × 160 mmterature ,49,50,51terature . Based oterature , at bothThree of the four ties were reinforced with unresin carbon fiber, at a fiber content of 0.35% (vol./vol.), provided by a single bundle, from top to top, thus overlapping with the rods. The required anchorage length of the fiber bundle was assessed through preliminary pull-out tests. The manufacturing process was the hand-lay-up or laminating ,41,45, iDue to the slenderness of the ties, to avoid accidental microcracking at formwork removal, these specimens were demolded only 48 hours after casting. Then, the ties were kept in water at 20 °C.In the following, the procedures to characterize matrix workability and strength and to assess tensile behavior of TRC are described.The workability of the fresh mixes was measured according to ASTM C1437-13 . The sprThe compressive, flexural and tensile strength of the cementitious mixes was evaluated.3 per mix at an age of 28 days, following EN 196-1 [Flexural strength was assessed through testing of three prisms of 40 × 40 × 160 mmEN 196-1 . The speThe tensile strength was evaluated though a direct tension test on unreinforced ties, whose details are described next .Direct tensile testing is arduous and therefore not very common ,56,57. ATests were conducted using a screw-driven universal test frame Instron 5900-R , equipped with a 10 kN load cell capacity (class 0.5). The tension load was applied under displacement control at a rate of 0.5 mm/min, common within this type of testing ,40,50. TAll direct tension tests were carried out when the specimens were 28 days old.In this section, the results obtained in the different experiments are reported. Those related with the matrix properties are briefly discussed here, while tensile behavior is the object of a detailed discussion in 4.1.The strength results are summarized in A good agreement is found with existing relationships in reference documents ,61. Fromcr), the crack spacing (Srm), the ultimate load (Fu) and the corresponding deformation (εu). These values are presented in According to De Santis et al. , the mosThe energy absorption capacity and ductility are also important in several TRC applications. Therefore, strain energy and ductility are evaluated. Strain energy (U) is computed as the integral of the load-elongation product until 70% of the ultimate load at the softening branch. Ductility is quantified through the ratio between the average strain at the ultimate load and the strain at cracking. The results of these two parameters are presented in The cracking load of the different TRC varied generally according to the matrix strength. As expected, this parameter was controlled by the lowest ultimate strain of the composite constituents, which was the matrices’ ultimate strain. However, the lowest cracking load was observed in A50. This is attributed to a presumable defect in the tie, as the response after cracking was hardening and the second crack appeared at a load already superior to that of A60 cracking load.Concerning the ultimate load, the highest value was for A35, while A40 and A60 composites had quite similar ultimate loads. The ultimate load of A50 was a bit lower but still comparable with those of A40 and A60. The difference between these two groups lies in the controlling factor of the ultimate load. For A35 it was matrix strength, whereas for the others it was reinforcement load-bearing capacity. In A40, A50 and A60, after cracking, the fibers were able to withstand the imposed strain without a significant loss of load-bearing capacity, transferring stress to the matrix that caused further cracking. In contrast, in A35, the cracking load was too high to be sustained by the fiber bundle alone at the cracked section, causing the composite to fail without further cracking. Furthermore, in A35 a single crack was formed, while in the others there were multiple cracks.Observing the ultimate loads of A40, A50 and A60 composites, it is estimated that the fiber bundle can sustain a load of around 3 kN when embedded in cementitious matrices. The ultimate load of A50 being lower than those of A40 and A60 is attributed to a poorer fiber-matrix bond. It is judged that the inferior bonding is caused by a lower fluidity of the matrix that has less penetrated the fiber bundle. The mix A50 was the one with the lowest water-cement ratio of those without superplasticizer. Nevertheless, a similar value is found for the fiber bundle in A35. At cracking of A35, the load transferred to the bundle (3.4 kN) was higher than its load-bearing capacity, which led to the immediate failure, without further cracking.In A40, A50 and A60, cracks were formed successively until crack saturation was attained. Afterwards, there was strain hardening and the deformation became concentrated in one of the already existing cracks, as can be observed in Similar crack spacing was observed in A60 and A40, while A50 showed a smaller number of cracks, thus a wider spacing. This is attributed to the already discussed weaker fiber-matrix bond, which requires longer lengths to transfer the load carried by the fiber at cracks to the matrix. Crack spacings in TRC like those obtained in this research have already been reported ,49,63.Regarding average strain at peak load, similar values are present in A60 and A40, while for A50 the value is a bit smaller (in agreement with the ultimate load variation). Obviously, the strain at peak load for A35 is a lot smaller because it corresponds to matrix strain at maximum tensile stress. Therefore, there is a significant difference between the tensile behavior of A35 and the other tested solutions, regarding ductility. This is evidenced by the large differences in strain energy and in the ratio considered to quantify ductility between A35 and the other TRC composites.All TRC composites failed by fiber pull-out. After the peak-load there was a stiffness drop that triggered automatic stop of the test. Although the crack localization caused local strains that were higher than the fiber ultimate strain, the ties were still not in separated pieces. This happens because when the reinforcement is provided by fiber bundles, the state of strain is not the same at all filaments. There is a strain lag  and furtComparing the tensile behavior of TRC with that of conventional reinforced concrete, there are similarities and differences. In both, there is a mechanic reinforcement ratio threshold that enables control of cracking. The amount of reinforcement should be capable of withstanding the energy that is released when the matrix cracks. In this research, the mechanical reinforcement ratio of A35 is under that threshold, while that for A40, A50 and A60 is above.The smaller reinforcement diameter of TRC, accompanied by a group effect (narrower reinforcement spacing), does not allow the application of the existing analytical models for the simulation of crack behavior of conventional reinforced concrete to TRC. Furthermore, the group effect also causes heterogeneity concerning the fiber involvement by the matrix. This is a complex issue, as the fresh state matrix properties also play an important role in the ease with which it can surround fibers. Moreover, the number of filaments in a bundle also influences the ease by which the matrix penetrates the bundle . NeverthThe economic analysis will not be linked to any particular currency, as it will be based on relative costs. Let us consider steel as the reference material concerning cost. Following Meredith et al. , the ratct = 3 MPa and that the yield stress of steel is 500 MPa. Based on the present experimental work, it will be fair to assume an ultimate load Fu = 3 kN for a bundle of unresin carbon fibers totaling 1.83 mm2 of fiber cross-section embedded in the cementitious matrix. Based on the results from Donnini et al. [For the mechanical properties, it is assumed that concrete has a tensile strength fi et al. , a ratioThe structural element is assumed to be lightly-loaded and its thickness is ruled by durability constraints, for conventional reinforced concrete, and ruled by bond requirements in TRC. Then, as in , thicknec,CRC, requires a steel area As = (3/500) × Ac,CRF. As for this solution, Ac,CRC = 0.06 m2, then As = 35 × 10−5 m2.To ensure control of cracking, the reinforcement must be capable of bearing the force that is transferred when a crack opens in the matrix. Therefore, for the conventional reinforced concrete, a concrete cross-section, Ac,TRC, requires a number of unresin carbon fiber bundles NUCF = /Fu = /3. As for this solution Ac,TRC = 0.018 m2, then NUCF = 18, which corresponds to an area of 32.94 mm2. Considering the previously estimated efficiency of impregnated carbon fiber, still for the TRC solution the required reinforcement area with impregnated fibers is calculated through AICF = AUCF/1.7, which returns AICF = 19.38 mm2. The quantities and solution costs of the materials are presented in Following the same principle for TRC, a concrete cross-section, AThe results in 2 emissions, the ratios presented in 3 to kg, using the previous densities. Within this frame, a 45% content (wt./wt.) of resin in the impregnated carbon fibers is assumed. Finally, total CO2 emissions for each solution are computed and presented in Regarding CO2 emissions by 70% when compared with conventional reinforced concrete. However, the solution with the lowest CO2 emissions is TRC with impregnated fibers, which has 10% less emissions than TRC with unresin fibers. Nevertheless, the use of resin encompasses additional environmental issues, as stated in 1.3, whose quantification falls outside of the scope of the present research. TRC with unresin fibers reduces COA brief retrospective of concrete reinforcement was provided. Textile reinforced concrete was identified as a solution that meets sustainability criteria. Precast lightly-loaded or non-load-bearing elements, whose thickness, in the case when they are made of conventional reinforced concrete, is ruled by durability concerns, have been identified as a cluster of excellence for the application of textile reinforced concrete. The potential hazardousness of the resin used in the impregnation of the fibers commonly applied in textile reinforced concrete was recalled.The performance of TRC with unresin carbon fibers, concerning control of cracking was assessed through tensile testing. It was found that control of cracking is possible, using unresin carbon fibers, if the load bearing capacity of embedded reinforcement is not less than the cracking load. The tensile behavior of the tested composites was similar to other TRC found in the literature.A novel system to transfer the load from the testing machine to the specimens was introduced and has proven effective.The economic and environmental analysis demonstrated a similar performance of TRC with prepreg and with unresin fibers, and both clearly outperformed conventional reinforced concrete. However, TRC with unresin fibers is considered preferable, due to the benefits concerning health, ease of recycling and resistance to deterioration under high temperatures.The subpar performance of A50 must have been due to less fiber involvement by the matrix. This will be further investigated through a dedicated experimental program encompassing matrices with different workability and cross-section observation using microscopy. Anyway, unlike in conventional reinforced concrete, it is recommended that the mechanical performance of each TRC solution (fiber-matrix combination) should be experimentally evaluated. Such assessment must provide the reinforcement bearing capacity when embedded in the matrix, a fundamental parameter for control of cracking, as addressed in the present research, but also for other design criteria, e.g., the bending ultimate limit state.


Despite surgical resection and adjuvant therapies, stage III melanomas still have a substantial risk of relapse. Neoadjuvant therapy is an emerging strategy that might offer superior efficacy compared to adjuvant therapy. Moreover, neoadjuvant therapy has some virtual advantages: it might allow for less demolitive surgery, permit the in vivo evaluation of drug efficacy, help tailor adjuvant treatments, and play a crucial role in innovative translational research. Herein, we review the available literature to explore the scientific background behind the neoadjuvant approach. We also discuss published clinical trials with a focus on predictive biomarkers and ongoing studies. Finally, we outline a possible framework for future neoadjuvant clinical trial development based on the International Neoadjuvant Melanoma Consortium guidelines. Anti-BRAF/MEK agents and immune checkpoint inhibitors (ICIs), which have proven their efficacy in metastatic melanoma patients, have been tested as an adjuvant therapy for resected stage III high-risk melanoma to reduce the risk of recurrence and improve distant metastases-free survival (DMFS) and overall survival (OS) ,3,4,5,6.Despite surgical resection, high-risk stage II  patients can have even worse survival than some stage III patients . InterfeAn emerging issue is evaluating effective treatments for melanoma through neoadjuvant therapy. This approach offers some additional benefits compared to adjuvant treatments alone ,11,12,13First, the tumor shrinkage after induction therapy can translate into less demolitive surgery with inferior morbidity and an increased chance to be radical ,11,12,13p = 0.001)  [Second, neoadjuvant therapy offers an in vivo test for the efficacy of the drugs, thus allowing a tailored adjuvant approach. For example, an ongoing clinical trial PRADO is evaluating the possibility to de-escalate or escalate systemic adjuvant therapies and the relevance of complete dissection in patients who achieved a complete pathologic response (pCR) ,15. Notactively) .Third, an analysis of modifications to the tumor and its microenvironment after neoadjuvant therapy might provide useful insights for translational research. In particular, it will be important to identify the mechanisms of resistance and predictive biomarkers, such as the gene expression signature, tumor-infiltrating T-cells, and tumor mutational burden, to better select the patients who could most benefit from different types of therapies.Fourth, it has been hypothesized that, for melanoma, the neoadjuvant approach could confer a possible advantage in survival compared to adjuvant strategies ,22 with All these advantages should be weighted against the risk of cancer progression during neoadjuvant treatment. However, this risk seems to be low (see below). We reviewed all the available studies on neoadjuvant treatments for stage III melanoma, with a specific focus on the predictive factors of response .Before the introduction of ICIs and anti-BRAF/MEK agents, chemotherapy was the standard of care for melanoma patients.Studies conducted on advanced melanoma patients reported a 10–20% response with Dacarbazine and up to 40% with a combination of cytotoxic drugs without a substantial survival benefit ,24.To improve the outcome of metastatic melanoma patients, trials with biochemotherapy, including Interleukin-2 (IL-2) and/or IFN-alfa, in association with chemotherapy have been conducted. A meta-analysis by Ives reported a response rate (RR) of up to 50% with biochemotherapy without a survival improvement .Considering the RR, biochemotherapy was also tested in a neoadjuvant setting. Buzaid described a 48% RR with neoadjuvant biochemotherapy, including 10% complete responses (CR) , similarForty-eight patients with stage III melanoma were treated with Cisplatin, Dacarbazine, and Vinblastine, in association with IL-2 and IFN-alfa . The resLewis reported the results of another phase II study, enrolling 92 patients with stage III melanoma, with either clinical lymph node or sentinel lymph node positivity, and treated with biochemotherapy . The RFSA retrospective study considering 153 patients treated in a single institution with biochemotherapy in a neoadjuvant setting reported toxicity in 46% of the patients. These adverse events were associated with a worse survival, suggesting that the inability to tolerate neoadjuvant biochemotherapy could be a negative prognostic factor .In a study by Koyanagi, circulating tumor cells (CTCs), during neoadjuvant biochemotherapy, were associated with a worse prognosis. Therefore, CTC monitoring could help predict patient outcomes .Temozolomide was also tested in melanoma patient candidates for surgical resection. The RR was 16%, similar to that in a metastatic setting . MoschosThe trials with IL-2/IFN and chemotherapy as neoadjuvant agents did not demonstrate a survival advantage, but they represent the basis for a promising neoadjuvant strategy in the treatment of stage III melanoma patients.+ T-cell clones. This specific immune system activation is essentially mediated by the recognition of neoantigens expressed selectively by cancer cells [Preclinically, it has been shown that neoadjuvant immunotherapy confers a better prognosis compared to the adjuvant approach . This efer cells . From ther cells ,34. Considering the positive results of anti-PDL-1 and anti-CTLA4 combination therapy in advanced-stage melanoma  and adjuNeoadjuvant ipilimumab was tested by Tarhini et al.  in localMoreover, the cytokine and chemokine profiles were evaluated, and the IL-7 blood levels showed a significant correlation with grade 3 colitis, supporting the connection between immune-related toxicity and ipilimumab’s mechanism of action . In addi+ and FoxP3+ Treg were observed in the relapsed patients. Similarly, lower Treg in the tumor was related to clinical benefits. Within the tumor, Ipilimumab induced several modifications, such as increased infiltration by activated T-cells , the induction of memory cells (CD45RO+), and decreased MDSC, all leading to an improved 1-y RFS [The updated long-term results  reported 1-y RFS . These fHuang et al.  tested nAccording to previous data ,34,42,43+ CD8 T-cells was observed, particularly in cells expressing PD-1, CTLA-4, and markers of T-cell exhaustion, such as CD39 [+ cells during pre-treatment, day 7, and week 3 presented a similar differentiation phenotype, corroborating the role of the PD-1 blockade in revitalizing a pre-existent subset of T-cells [Besides pCR, the radiographic response (available in six patients), decreased viable tumor (<50%), and increased tumor-infiltrating lymphocytes (TILs) were all associated with improved DFS . In part as CD39 . Intrigu T-cells .+, CD4+, and FoxP3+ regulatory cells was detected after pembrolizumab; in the tumors, an expansion of CD8+ T-cells and T-lymphocytes expressing exhaustion markers (bet and eomesodermin) was observed, featuring a strong association with clinical benefits, consistent with the preclinical models [In the peripheral blood, an increased proliferation of CD8l models .Notably, an exhausted phenotype is commonly associated with T cell effector-function deterioration and the expression of immunosuppressor receptors . TherefoIn a phase Ib OpACIN trial, 20 patients with clinical stage III melanoma were randomly chosen to receive Ipilimumab 3 mg/kg (IPI3) and Nivolumab 1 mg/kg (NIVO1), as four courses of adjuvant therapy or divided into two neoadjuvant treatments followed by two post-operative courses . NotablyThe randomized phase II trial of Amaria et al. compared four doses of neoadjuvant Nivolumab 3 mg/kg (NIVO3), versus up to three doses of combined IPI3+NIVO1 in clinical stage III and oligometastatic stage IV melanoma . The com+ T-cell tumor infiltrate, PD-L1, and lymphoid markers  were higher in the baseline and early-treatment tumor samples of the responders. A greater expansion of peripheral blood tumor-resident T-cell clones was observed in the combination arm, although this did not reflect differences in response [The small numbers of patients enrolled combined with premature interruptions make it difficult to obtain conclusive clinical efficacy data from these two studies ,34. Howeresponse ,34,48. Given the toxicity of the combination therapy and the poor responses with the risk of progression and inoperability among the patients treated with ICI monotherapy, the OpACIN-neo trial was designed to preserve a high response rate while minimizing the toxicity of combination therapy . In thatp < 0.001) [In the pooled analysis of these two studies, pCR was observed in 38% of patients and was associated with a better RFS: a 12-month RFS in 100% vs. 72% in patients with or without pCR, respectively (< 0.001) . Taken t< 0.001) . However< 0.001) . In ancillary translational studies of the OpaCIN-neo trial, contrary to the results of Amaria et al. , PD-L1 eAs suggested in the OpACIN-neo trial, pathologic response is an important marker for RFS, even if its long-term benefits remain to be proven . In a smThe use of targeted therapy as a (neo)adjuvant treatment has been reported since 2013 in many retrospective studies and case series ,15,57. HAmaria et al.  reportedThe NeoCombi is a single-arm, open-label, single-center phase II study that was performed at the Melanoma Institute Australia. This study, patients with IIIB-C melanoma received Dabrafenib and Trametinib for a total of 52 weeks (12 weeks before complete resection and for 40 weeks after surgery). The study enrolled 35 patients, and the median follow-up was 27 months . Nearly From a translational perspective, the biomarker analyses available from the NeoCombi and CombiNeo trials showed lower phosphorylation of ERK at baseline in patients who achieved pCR and, intriguingly, a higher expression of TIM3 and LAG3 in the TILs of patients who did not achieve a pCR ,58. Thesp < 0.001). Notably, the RFS rates at 24 months for those with pCR after immunotherapy treatment were 100% (72% for those without pCR RFS rates). Instead, for those with pCR after targeted treatment, RFS was 78% (compared with 8% for those without pCR) [The results of the immunotherapy and BRAF/MEK inhibitor trials in neoadjuvant settings suggest some relevant questions regarding their different levels of efficacy. In particular, the pooled analysis of Menzies et al. suggests an increased activity of immunotherapy in comparison to BRAF/MEK inhibitors. The 12-month RFS was improved in patients who received immunotherapy compared to targeted therapy treatment  .Another pivotal issue concerns the predictive biomarkers for immunotherapy and BRAF/MEK inhibitors to better select the right treatments for patients. For targeted therapy, remarkable results were observed in a recently published biomarker analysis of an adjuvant COMBI-AD trial, in which patients were randomized to Dabrafenib and Trametinib vs. placebo . High INIntralesional treatments represent a promising strategy for melanoma neoadjuvant therapy. This treatment modality could determine a profound tumor response, and potential advantages include the possibility to elicit both a local- and a systemic-immune response while reducing systemic adverse events. The first demonstration of melanoma cell eradication in a neoadjuvant setting employed polylactic acid microspheres (PLAMs) loaded with IL-12 or TNF-a in a B16 melanoma mice model . This prIn a clinical setting, data on intralesional neoadjuvant treatments are derived from trials on early metastatic disease (unresectable stage IIIB/C-IVM1a). The combined intralesional administration of Interleukin 2 (IL2) and tumor necrosis factor-alpha (TNFα), both fused with monoclonal antibody L19, which binds fibronectin (immunocytokine L19-IL2/L19TNF), and achieved a disease control rate of 80%. This antitumoral response allowed the surgical resection of residual tumor mass in 7/20 patients . In the To map the current trends in trial design for melanoma neoadjuvant treatments, we searched and manually annotated the ongoing studies available on clinicaltrial.gov  phase 2 studies. Indeed, the median number of patients planned to be enrolled was medium-to-low . More than half of the trials used the RR (57%) as a primary endpoint, while nearly one third used RFS (30%). A response rate endpoint facilitates rapid data generation, and the surrogacy of melanoma with RFS seems to be probable . TherefoInterestingly, 70% of neoadjuvant trials also scheduled adjuvant treatment. This is particularly important when RFS is considered. Moreover, the intensity of adjuvant treatment could be modulated by the response to neoadjuvant therapy. However, this adjuvant escalation vs. de-escalation based on pCR is being evaluated by only a minority of studies . In general, the overall time of the therapy (neoadjuvant + adjuvant) among trials was 1 year, while the median neoadjuvant length was 6.5 weeks (an interquartile range of 6–8 weeks).An ongoing randomized phase 2 trial that could be practice changing (NCT03698019) will test 9 weeks of pembrolizumab followed by surgery versus surgery alone. Patients of each arm will undergo adjuvant pembrolizumab to complete 1 year of therapy. The primary endpoint is relapse-free survival, and the target accrual is 500 patients. This study could show whether neoadjuvant immunotherapy can decrease melanoma relapse compared to a classic adjuvant approach.Another interesting trial is the OpACIN-neo/PRADO study. This is an open-label three-arm phase 2 trial (OpACIN-neo) that tests the different toxicity levels of three Nivolumab and Ipilimumab combinations. The results have already been published (see above). The expansion cohort (PRADO) will enroll 110 stage III melanoma patients who will be treated with the winning treatment of the OpACIN-neo study. Moreover, the adjuvant treatment will be tailored to the neoadjuvant treatment via the achievements of pCR.To harmonize the study design of neoadjuvant trials on melanoma, in 2016, the International Neoadjuvant Melanoma Consortium was established, and has produced some suggestions for clinical trial development . A focusStage III is an appropriate setting to conduct a neoadjuvant trial, because it necessitates risk-reduction therapy and allows us to study not only the tumor, but also the lymph nodes after a lymphadenectomy. In that context, stage II or IIIA should have a different and dedicated study design. Instead, oligometastatic stage IV could be included in stage III trials, but in a different cohort, because of its different risk of relapse.The optimal duration of neoadjuvant therapy remains unknown. However, it is critical to balance efficacy with the risk of progression or the delay of surgery because of toxicity. From this perspective, a duration of 6–8 weeks is suggested. Such a homogenous duration could also permit a cross-trial comparison. However, as new evidence regarding neoadjuvant therapy emerges, a longer duration could be considered.Besides the neoadjuvant regimen, it is also vital to schedule the adjuvant phase. In light of the data generated from registration phase III adjuvant trials, a total of 1 year of therapy should be considered adequate. However, as new data become available, a tailored adjuvant approach based on the achievement of pCR could be adopted.Regarding outcomes, several considerations can be made. Compared to stage IV, which is often characterized by immunoevasion , earlierBasal staging imaging should be provided for each candidate in neoadjuvant trials. While 18F-FDG PET/CT offers high sensitivity, a CT scan is preferred, because of its better visualization of the liver, brain, and lungs.From a translational point of view, a careful and pre-planned collection of biological samples should be done. Cancer cells and their microenvironment, blood , and the microbiome should be collected at specific time points .Another possible innovative strategy to reduce systemic toxicity and further improve the tumoral delivery of drugs could be intratumoral immunotherapy, as stated in a recent ESMO-meeting .Finally, it should be stated that current international guidelines do not support neoadjuvant therapies for resectable disease outside the frame of clinical trials.It has been hypothesized that neoadjuvant treatments could be more effective compared to adjuvant ones. This idea relies on the preclinical and clinical findings that neoadjuvant immunotherapy sharply increases the number of TILs , which aAnother unresolved issue is the proper duration of neoadjuvant therapy. While clear data regarding the optimal duration of targeted therapy are still lacking, the use of only two cycles of Ipilimumab + Nivolumab seems to be effective in a neoadjuvant setting . These fFinally, an important unresolved question is how to tailor adjuvant treatments after neoadjuvant therapy. Since pCR seems to predict an excellent prognosis, active surveillance could be sufficient for complete responders. On the contrary, patients that do not obtain a pathological response to neoadjuvant treatment could benefit from an escalated adjuvant approach. These ideas are being tested in the ongoing PRADO trial discussed previously .The pharmacological treatment of melanoma is a rapidly evolving field. Adjuvant immunotherapy and BRAF/MEK inhibitors have revolutionized the prognosis of this highly lethal disease, and the neoadjuvant approach promises a second revolution. Pre-surgical therapy could exploit a competent immune system to increase the efficacy of currently available drugs, while providing important biologic and translational data. Moreover, the achievement of pCR could help guide a more tailored adjuvant approach. While neoadjuvant therapy for stage III melanoma is an exciting topic for the future, some challenges still need to be addressed, such as the high toxicity of such therapies and determining the most effective schemes and schedules. Ongoing clinical trials will provide all these awaited data.


The article shows investigations on the behavior of preplaced aggregate concrete with regular and irregular coarse aggregates. The thermal properties, compressive strength, and internal structure were analyzed based on computed tomography images. The regular and irregular shapes of aggregates were obtained according to patented technology, which is possible to produce in both laboratory and industrial conditions. Based on the conducted calculations, heat storage capacity was assessed. The influence of grain shape on the material strength, porosity, and hydration gaps was determined. Debonded porosity, as a result of aggregate impurities, was shown using computer tomography analysis. It was shown that the arrangement and shape of the grains has a significant impact on the performance properties of hardened preplaced concrete. Different types of concrete are widely used in all types of civil engineering constructions. Approximately 70% of its volume is aggregate, and therefore, the quality of the aggregate significantly affects the properties of the concrete mix, such as consistency, workability, and water demand, as well as the properties of the hardened concrete e.g., strength, waterproofing, water absorption, and frost resistance . The maiThe preplaced aggregate concrete (PAC) is a characteristic and untypical type of concrete, which is different than concrete performed in the traditional manner. The main differences relate to the raw material’s characteristics, preparation process, and raw materials content . PAC couIn the design process of concrete, relatively little attention is paid to the geometry of aggregate. Most research works focus on cement binder modifications while looking for new additives and admixtures to improve the quality of concrete. In the work cited above, Rocco et al. studied the impact of shaped  grains of artificial aggregate made of sintered mullite on concrete properties, i.e., tensile strength, susceptibility to cracking, modulus of elasticity, etc. Artificial aggregate production enables grain sphericity to be easily obtained. Until now, it has been problematic to obtain natural crushed aggregates of a regular shape. The technology developed by AGH University of Science Technology makes it easy to obtain cubic or flat-shaped aggregates. Admixtures and additives are usually difficult to use, and any change in the chemical composition of the clinker requires corrections and refinement of the recipe. There are not many studies on aggregate itself, and the research is limited to the impact of rock chemistry on the quality of the aggregate–binder combination . ResearcThe aggregate used in the study is dolomite from the Imielin deposit . Due to their basic chemical nature, dolomite aggregates are a good mineral filler in simple concretes . The proProperties of dolomite aggregate. Dolomite aggregate can be used as an alternative to gravel aggregates in the production of simple concrete, as well as for floor, contractor, or hydrotechnical concretes. This is due to similar functional properties such as resistance to grinding and abrasion, resistance to crushing, frost resistance, water absorption, and the rheological properties of the concrete mix ,30. For 2O3–2.75%, SiO2–20.26%, Al2O3–4.89%, others–8.16%)  and a setting time regulator (up to 5%). No additives and chemical admixtures were included, as the research focused on the properties of aggregate, specifically coarse fractions of 12–14 mm with various shapes. Moreover, the mixes were not prepared using a continuous graining curve. The reason for this was to capture the effect of the coarse grain shape on the material properties as much as possible, which is the main purpose of the research presented in this article. In this way, basic samples were obtained, and potential factors that could affect the test results were eliminated. Therefore, the aggregate shape remained the only variable. As a result, the water-to-cement ratio was equal to 0.62. Thanks to this, the appropriate workability of the cement matrix that was added to the aggregate was ensured.The tests were carried out on 21 different concrete samples, with dimensions of 100 mm cubic sides, made of regular and irregular dolomite aggregates in the 12–14 mm class. In order to determine the compressive strength of concrete, 18 samples were tested, while the remaining ones were subjected to thermal tests. Preplaced aggregate concrete is prepared by placing coarse aggregate into formworks and then injecting the grout mortar into the void between the coarse aggregate . The comTwice as many cubes were made of the concrete mix with irregular aggregates, which were cut parallel and perpendicular to the pouring direction for the purpose of the thermal and structural tests. The cubes of regular aggregates were cut perpendicular to the pouring direction  In the cWhen preparing the test mixes, differences in flow were noted, i.e., in concrete consistency. In the case of the shaped aggregates, the measured flow is greater and equal to 175 mm, and the consistency is smaller, which confirms the lower demand for water and cement mix. The flow was 150 mm for the irregular aggregates. Similar results were obtained in studies on the formation of fibro concretes from regular and irregular aggregates .After 28 days of the concrete aging, the samples were subjected to strength and thermal tests using a thermal imaging camera. The difference in the cooling temperature of the concrete with regard to the type and arrangement of aggregates was determined, as well as the calculation of the thermal parameters . Then, the concrete samples were subjected to internal structure tests using a GE tomograph in order to determine air pores and hydration cracks. Thermal tests were carried out using the NEC ThermoGear G100 thermal imaging camera , which enables the registration and visualization of temperature distribution on the surfaces of objects . The camera works by converting infrared radiation emitted or reflected by these objects into an electrical signal and then into an image viewed on the screen—the so-called thermogram. Thermovision allows the detection of many properties of plastics in a way that no other technology can. The camera was placed at a distance of 40 cm from the tested sample. The samples were placed in a laboratory dryer that was heated to 160 °C for 2 h. After this time, the temperature was measured to determine the cooling time. At the beginning of the measurement, the temperature between consecutive measurements was measured every 30 s, then every minute, and later at longer intervals.ave was used, i.e., the average temperature collected from the entire surface of the sample. Thermal properties of concrete materials are attracting increasing attention, not only because of their effects on building energy efficiency but also on structural performance and serviceability. More and more often, modern concrete materials containing various types of aggregates  and fibers are used. These materials are used in transport structures such as pavements and bridges platforms as well as large foundations (bulk concrete) where thermal behavior is important and sensitive to the behavior of the structure.On the thermal imaging camera, a program can be set for reading temperature values on the surface of samples in various places. To calculate the heat capacity, the value Strength tests were performed using the destructive method by means of the Toni Technik strength press  , which iImaging tests were performed using a model Vtomex m300 General Electric (GE) tomograph   with theThe computed tomography method can be used to assess the microstructure of the binder and the number and shape of air pores in concrete. Plane images obtained on different depths of samples allow assessing the spatial distribution of the examined objects. The assessment of the distribution, size, and shape of pores has a decisive influence, among others to infer the durability of concrete. Pores formed accidentally as a result of the inappropriate selection of components or improper technology of mixing and laying concrete mix are harmful due to the strength and tightness of concrete and its frost resistance.ave contained in m—mass [kg]ΔT—temperature difference before and after heat conversion [K]c—specific heat of the tested concrete in a dry state [J/kg∙K]  ratio and degree of hydration are among the most important factors of concrete strength. The w/c value is constant for all the samples and equal to 0.62. However, the shape and size properties of the aggregate particles that are used as fillers are also of major importance. The shape of aggregate particles mainly affects the demand for water and the amount of cement required for the workability of a given concrete mix .Particles with an elongated shape require more water in the process of concrete production, and therefore the use of this type of aggregate decreases the workability of a concrete mix. On the other hand, smooth texture and rounded aggregate particles require less water to create concrete with an improved performance. The binding with cement can also be weakened due to water accumulation under relatively large surfaces of flat aggregate particles. For the same w/c ratio value, concrete with regular and broken aggregate particles has a higher compressive strength than concrete with irregular aggregates. The basic requirement for hardened concrete is its compressive strength. This property is closely related to the microstructure of the hardened cement, the strength of the aggregate, and the aggregate–cement contact area. The compressive strength of the concrete determines the grade and quality of the concrete. Concrete strength tests were carried out in accordance with the PN-EN 12390-3  standardA slightly higher average strength (44.6 MPa) was obtained when the direction of the force was parallel to the arrangement of particles (sample 1). For the perpendicular direction of breaking force (sample 2), the achieved value was 43.4 MPa. The results for samples with regular particles were also characterized with a lower standard deviation of strength (σ = 0.32) when compared to the results for samples with irregular particles—where the values for both types of samples were greater than 1. In addition, the perpendicular arrangement of irregular particles to the direction of the acting breaking force was also characterized by a higher standard deviation (σ = 1.12) than in the case of the sample with irregular particles arranged parallel to the direction of the force (σ = 1.03).Based on these tests, it can be observed that the particle arrangement in the material, as well as their shape, has a significant impact on the mechanical strength of preplaced concrete. When knowing the direction of compression or the breaking force on the sample, the value of the concrete strength for a specific concrete element can be increased by using a suitable method of filling the mold. Based on the above test results, it can be concluded that elongated particles in the concrete mix should be avoided because they have a negative effect on concrete strength. In addition, flat and elongated particles of aggregate are difficult to compact, and thus, the workability of the concrete decreases and the water demand increases. Increasing the water content reduces the strength and durability of the concrete.Three factors influence concrete porosity: the porosity of the aggregate, the porosity of the cement mix, and the porosity of the contact area; the aggregate consists of approximately 70% of the concrete’s volume. The porosity of coarse aggregate is low in relation to the porosity of the cement mix and usually does not exceed a few percent. Moreover, the amount and structure of the cement mix’s pores directly translates into concrete strength and other useful properties such as frost resistance, water absorption, or corrosion resistance . Thanks It is assumed that small spherical pores not connected together of a size not larger than about 300 µm do not significantly affect the durability and properties of concrete. Continuous gap pores and large (over 300 µm) spherical pores cause the deterioration of strength parameters. An increase in the content of air voids by 1% causes a decrease in compressive strength by approximately 5% . Figure Slit-like pores are formed as a result of the evaporation of demand water in the concrete mix in processes of clinker phase hydration. During the formation of concrete, significant amounts of heat are emitted, which results in thermal stresses and an increase in the vapor pressure of excess demand water. The risk of thermal gaps forming is highest in the initial hydration stage, when a fresh concrete has a lower strength. In Regular aggregates have a positive effect on concrete quality in terms of its durability, as well as in terms of its improved thermal properties and lower number of large pores. The utilization of regular aggregates improves the quality of construction materials.During the preparation of the concrete mixes for the tests, variations in flow, and thus in concrete consistency, were observed. The flow was higher (175 mm) for the sample with regular particles when compared to the sample with irregular ones (150 mm). The consistency of the mix was thinner, which confirms the lower water and cement demands of the mix.max, which could be cumulated and emitted by the material, was 206.8 MJ/m3 for regular particles and 199.1 MJ/m3 and 191.8 MJ/m3 respectively for irregular particles. These values are typical characteristics for ordinary concretes.Thermic tests carried out with the use of a thermal camera showed that the concrete sample with irregular particles of aggregate was cooling faster than the sample with regular particles. Moreover, the final temperature of cooling depends on the particle arrangement in the sample. Irregular particles arranged transversely keep the temperature longer, creating a barrier for the heat flow , while the parallel arrangement of aggregate particles in a sample act as a heat transporter . Maximum energy bOn the basis of the strength test results, it could be observed that the manner of aggregate particle arrangement in the material, as well as their shape, significantly influences the mechanical strength of concrete. By knowing the direction of the compressive force acting on a sample, it is possible to increase the value of concrete strength with an appropriate method of laying the concrete mix, which depends on its intended use.Concretes with 100% regular particles (six samples with 100% regular grains) obtained about a 10% higher strength, equal to 49.2 MPa, when compared to the remaining samples with irregular particles. The standard deviation results were lower for the concretes with regular grains when compared to the samples with irregular particles.Tests of the internal structure of the concretes using a tomograph showed that the concrete with irregular particles is characterized by a significant detachment porosity and size of hydration gaps, as well as a much higher content of large spherical pores (with a size of over a few millimeters), which are located at the aggregate–cement matrix phase boundaries. This fact has a direct impact on the strength of the samples and the increased demand for mixing water when using this type of aggregate.The aim of this investigation was to show the impact of the coarse particle size fraction aggregate (12–14 mm) on the selected parameters of the concrete mix and hardened concrete. Subsequent research will focus on testing regular and irregular aggregates in concretes with a constant and optimal particle size composition. The cost of producing regular grains and irregular aggregates, regardless of the regularity of the grains, is the same. While maintaining the same parameters of concrete, it is possible to reduce the amount of cement in the concrete mix by using aggregate of an appropriate shape. Detailed cost analyses will be presented in a separate article.Based on the results of this study, the following conclusions can be drawn:


A series of destructive and tumefactive lesions of the oral cavity are increasingly recognized as part of the IgG4-related disease (IgG4-RD) spectrum. We herein examined the clinical, serological, radiological, and histological features of a series of patients referred to our clinic because of oral cavity lesions ultimately attributed to IgG4-RD. In particular, we studied 6 consecutive patients out of 200 patients referred to the immunology outpatient unit who presented with erosive and/or tumefactive lesions of the oral cavity. All patients underwent serum IgG4 measurement, nasal endoscopy, radiological studies, and histological evaluation of tissue specimens. The histological studies included immunostaining studies to assess the number of IgG4+ plasma cells/High-Power Field (HPF) for calculation of the IgG4+/IgG+ plasma cell ratio. Six patients (3% of the entire cohort) were diagnosed with IgG4-RD of the oral cavity based on histological evaluation. A major complaint at presentation was oral discomfort due to bulging mass. A mild to no increase in serum IgG4 was observed. Different patterns of organ involvement were associated with oral lesions. Five patients were treated with immunosuppressive therapy and two patients promptly responded to B-cell depletion with rituximab. Watchful waiting was decided in one patient with no major clinical symptoms. Involvement of the oral cavity is an infrequent manifestation of IgG4-RD but should be taken into consideration as a possible differential diagnosis of tumefactive or erosive lesions once neoplastic conditions are excluded. A histological examination of biopsy samples from the oral cavity represents the mainstay for diagnosis of IgG4-RD. IgG4-related disease (IgG4-RD) is a systemic immune-mediated condition potentially affecting any organ, characterized by tissue inflammation and fibrotic outcome ,2. It caIn particular, four clinical phenotypes of IgG4-RD have been defined based on organ involvement: (i) pancreaticobiliary disease; (ii) retroperitoneal fibrosis with or without aortitis; (iii) head- and neck-limited disease; (iv) Mikulicz’s syndrome with systemic involvement ,6,7,8. WIn the present work, we report on six patients with atypical localizations of IgG4-RD in their oral cavities and describe the main clinical, pathological, serological, and radiological findings of a unique presentation that might complicate the differential diagnostic process.Six consecutive patients out of 200 patients, referred to the immunology outpatient unit with a diagnosis of IgG4-RD involving the oral cavity evaluated at San Raffaele Scientific Institute between January 2015 and February 2020, were included in this retrospective study. All the patients fulfilled the available IgG4-RD diagnostic and classification criteria . DemograThe present study has been approved by the San Raffaele Hospital ethics committee (approved on 15/7/2020) in adherence with the Declaration of Helsinki.M.L., G.M. and L.D. performed clinical evaluations and gathered laboratory data of the patients, while A.R. and A.V. performed the nasal endoscopy and tissue biopsy.Case 1: A 35-year-old female was admitted in April 2015 for a rapidly progressive frontal headache and complete visual loss in the right eye. Imaging studies of the head and neck revealed diffuse pachymeningitis with bone erosions, thickening of the nasal septum, hard palate tumefaction, and bilateral optic neuritis a. Her me2 weekly intravenous infusions leading to a prompt resolution of the parotid swelling and palate mass at 4-month follow-up.Case 2: A 20-year-old female was referred in June 2012 for a 4-month history of cervical lymphadenopathy and bilateral parotid glands swelling. Oroscopy also unveiled an asymptomatic involvement of the pterygopalatine fossa and oropharyngeal structures, with clear bulging of the hard palate . An exciCase 3: A 45-year-old male was referred in November 2019 for a 9-month history of mild dyspnea (on exertion), cough, nasal obstruction and bulging of his left nasolabial fold. An 18-fluorodeoxyglucose (18-FDG) positron emission computed tomography (PET-CT) scan showed bilateral ground-glass opacities, an intranasal mass with downstream extension to the superior alveolar processes, and disease activity in cervical and hilar lymph nodes. A biopsy of the nasolabial tissue showed an inflammatory pseudotumor with storiform fibrosis, more than 80 IgG4-positive plasma cells/HPF, and a IgG4/IgG-positive plasma cell ratio of 30–40%, a result that was highly suggestive of IgG4-RD. Serum IgG4 was 420 mg/dl . Mimicker neoplastic, inflammatory, and infectious disorders were ruled out through an extensive serological and pathological evaluation. Corticosteroid therapy was started at a daily prednisone dose of 0.6 mg/kg followed by gradual tapering over six months. Four months after initiation of the steroid therapy, a resolution of the cough and dyspnea were observed, but the bulging of the nasolabial fold was clinically stable. Because of the poor response of IgG4-RD to steroids in the oral cavity, surgical debulking is currently under consideration.Case 4: A 37-year-old female was referred in December 2017 for gradual onset of a dry cough, sore throat, and bilateral cervical lymphadenopathy. At oroscopy, a peritonsillar abscess was observed together with a hard mass on the left side of the soft palate close to the uvula a. The abCase 5: A 57-year-old male was referred for melena in September 2018. Radiological examination disclosed fibrotic tissue in the retroperitoneum surrounding the abdominal aorta and encasing the small bowel a. A wholCase 6: A 29-year-old male was referred in April 2013 for bilateral swelling of parotid and submandibular glands with discomfort when chewing. A PET-CT scan showed symmetric 18-FDG uptake at the salivary glands and identified an asymptomatic involvement of the rhinopharynx and tongue base . At orosThe mean age of the patients ws 37.7 years (SD 12.8 years). The main features of the six patients in the sample are presented in Prior to 2003, different illnesses such as Mikulicz’s syndrome, autoimmune pancreatitis, hypertrophic pachymeningitis, and Riedel’s thyroiditis were all considered separate entities, and only 17 years ago they were recognized as part of the unified spectrum of IgG4-related disorders ,16,17,18In our large single-center cohort, localizations of IgG4-RD in the oral cavity were observed in 6 of 200 patients (3%), a frequency similar to pleural, sinonasal, and pharyngeal involvement . The harIgG4-RD of the oral cavity, especially if isolated and not associated with other suggestive organ manifestations, can be challenging to recognize for several reasons. First, according to our experience, findings from physical examinations are largely non-specific, with patients presenting a swelling of mucosal and submucosal tissues with local hyperemia. However, although we could not identify any characteristic clinical feature, the absence of ulcers, tissue necrosis, fever, mucopurulent drainage, and local pain were helpful in orienting the diagnosis towards an inflammatory rather than infectious or neoplastic condition ,36,37,38In light of the abovementioned considerations, our experience suggests that diagnosis of IgG4-RD in the oral cavity should rely on a combination of clinical, serological, radiological, and histopathological findings because none of these approaches alone has sufficient accuracy as in other IgG4-RD manifestations . Of noteOral lesions due to IgG4-RD responded well to glucocorticoid therapy in most cases with prompt shrinkage of the fibro-inflammatory mass ,47. B-ceThe oral cavity is a rare but probably underestimated localization of IgG4-RD, which lacks a single reliable instrument for its diagnosis. Nevertheless, even when it presents with a single non-specific localization as in the oral cavity, IgG4-RD is a systemic disease, and as such it must be investigated. Therefore, the most adequate strategy to manage an oral lesion suspected for IgG4-RD manifestation should include clinical, serological, radiological, and histopathological studies assessed by different specialists, and only the combination of these findings may lead to a reliable diagnosis. The experience in oral lesions is too limited to find a targeted therapy, which is then based on the suggested treatments for other sites, basically steroids and B cell-depleting agents. Possible future developments would be the discovery of new drugs and the definition of more specific therapeutic algorithms, if not for any sites involved, at least for the four phenotypes identified.