Neural Model of Projecting Compressive Strength of Cement Concrete Intended for Airfield Pavements

This work present to the mathematical model in the form of ANN, intended for projecting concrete compressive strength. Input data was classified according to the type of component material and its content in concrete mix (cement contents, coarse aggregate, fine aggregate, water and admixtures). In order to determine mathematical model, a multilayer, one-way perceptron network was used, recursion network with sigmoidal neurons. The model assumes that neurons are gathered in some layers (one input layer, hidden layers and one output layer). The conducted cross-section of the influence of variables parameters values (learning constant - α and momentum values - η) on the accuracy of representation of compressive strength was analyses. Assessment criterion was assumed taking into consideration the lowest mistake level and 100% compliance. According to the obtained analysis results ANN was assumed the best representing network for constant value of momentum 0,3, learning constant of 0,05 and 6 neurons in a hidden layer. Very good coincidence of component models with experiment results was achieved. At testing stage, the coincidence was achieved at the level of 99.74%, in case of the assumed network structure. During model verification by means of experimental results, the average coincidence was 99.83%

Influence of the media used in the operation of aircraft on the durability of airport cement surfaces

Abstract: The intensification of air operations in recent years has resulted in an increase in stresses and deformations in concrete pavements. In terms of mass, dynamic and temperature interactions, these are measurable phenomena that can be determined and predicted using appropriate methods and algorithms. Another type of impact that does not occur in an avalanche-like manner on pavements is their random destruction caused by the presence and operation of exploitation media. The article presents the impact of selected measures on the change of concrete parameters and its durability in the pavement structure. The effects of this impact are significant and clearly destructive for concrete pavements. In addition to the measurable decrease in the mechanical parameters of concrete, there is an interference of media with the concrete structure, which in the presence of extreme temperatures (positive and negative) is a challenge for concrete technologists, contractors and users of airport pavements. The nature of the impact of exploitation media is varied and in most cases there is a combined effect of them on pavements. It has been shown that the operational coatings currently applied to pavements are only partially effective for these media, and learning about the nature and manner of impact makes it possible to effectively limit these unfavorable, objectively occurring phenomena. Keywords: Concrete airport pavement; Operating medi

Airport Cement Concrete with Ceramic Dust of Increased Thermal Resistance

The impact of aircraft on airport pavements is varied and closely related to their operational durability. The article presents the impact of the annealing process related to the forced impact of airplanes on airport pavements. The composition of cement concrete with ceramic dust, which is characterized by increased thermal resistance, has been proposed. Two research cycles were programmed, differentiated by the annealing scheme and the way in which the temperature influences the annealing time. Samples stored at a temperature of 20 ± 2 °C were subjected to testing. The tests were carried out for two diagrams: A and B. The first—diagram A—included the continuous impact of the flue gas stream on the samples for a period of 350 min with a test step every 25 min. For the second—diagram B—the samples were alternately heated (1 min) and cooled (15 min). The influence of the proposed pavement mix on changes in the internal structure of cement concrete and the increase in its resistance to high temperatures was determined. In the microstructure of the CC-1 concrete matrix, it was found that there were plate-granular portlandite crystals up to 10 µm in size and ettringite crystals with a length of 8 µm. In the CC-2 concrete, the ettringite crystals were less numerous and had a length of up to 5 µm, there were also continuous contact zones between the aggregate grains and the cement matrix (diagrams A). The alternating annealing/cooling (diagram B) resulted in the ettringite crystals in the CC-1 matrix being up to 10 µm long, and in the CC-2 concrete up to 7 µm long. The contact zone between the aggregate grain and the matrix in CC-2 concrete was continuous, and the microcracks in CC-1 concrete were up to 8 nm. Regardless of the heating diagram, in the surface zone, there were larger microcracks in the CC-1 concrete than in the CC-2 concrete. For diagram A they were 14 µm and 4 µm and for diagram B they were 35 µm and 5 µm, respectively. It was found that concrete with ceramic dust is characterized by a lower and more stable temperature increase. In scheme A, the average temperature increase on the heated surface ranged from 46 °C to 79.5 °C for CC-1 concrete, and from 33.3 °C to 61.3 °C for CC-2 concrete. However, in scheme B, the temperature after 350 heating cycles for CC-1 concrete increased to 129.8 °C, and for CC-2 concrete to 116.6 °C. After the cooling period, the temperature of CC-1 and CC-2 concrete was comparable and amounted to 76.4 C and 76.3 °C, respectively. CC-2 concrete heats to lower values, and favorable changes in internal structure translate into higher strength and durability (after 350 heating cycles according to scheme A, the strength of CC-1 concrete was 67.1 MPa and of CC-2 concrete 83.9 MPa, while in scheme B, respectively, 55.4 MPa for CC-1 and 75 MPa for CC-2)

Application of ceramic dust as a modifier reducing the extent of rheological deformations in airfield pavement concrete

The article presents material solution based on the application of ceramic dust as concrete mix component intended for airfield pavements. Material composition is intended for the application on the selected areas of pavement exposed to the influence of imposed thermal loads intensifying the stress strain state of concrete slabs. Due to the nature of loading of these parts it is necessary to reduce the extent of registered rheological deformations. Concrete containing dust additive is distinguished by more favourable porosity properties, more consistent cement matrix without visible discontinuities and with the formed different hydration products. Diversification of internal micro structure of cement concrete using the suggested dust has significant influence on the improvement of mechanical, physical and performance parameters. Also, assessment of the applied dust influence on the extent of the registered rheological deformations was presented. The analyses included concretes curing in standard conditions and concretes subject to thermal cycles representing the destructive influence of imposed loading. The obtained laboratory test results prove clearly the validity of the suggested solution. Reducing the extent of deformations is derivative of favourable changes observed in internal structure of concrete composite. Better formed contact areas provide the increased concrete parameters and consequently influence extending concrete durability

Low-shrink airfield cement concrete with respect to thermal resistance

The paper presents theoretical background to the occurrence and propagation of imposed thermal load deep inside the structure of airfield pavement. The standard composition of low-shrink cement concrete intended for airfield pavements was presented. The influence of recurring temperature changes on the extent of shrinkage deformations was assessed. The obtained lab test results, combined with observations and analysis of changes of the hardened concrete microstructure, allowed the authors to draw conclusions. It was proven that the suggested concrete mix composition makes it possible to obtain the concrete type of better developed internal microstructure. More micro air voids and reduced distance between the voids were proven, which provides increased frost resistance of concrete. The change of size, structure and quantity of the hydration products in the cement matrix and better developed contact sections resulted in the improvement of the mechanical parameters of hardened concrete. Low-shrink concrete in all analysed cases proved to have increased resistance to the variable environmental conditions. Increased concrete resistance is identified through reduced registered shrinkage deformations and growth of mechanical parameters of concrete. Low-shrink concrete used for airfield structure guarantees extended time of reliable pavement operation

Application of similarity method of distance courses describing the elements content in cement concrete after 50 forced thermal cycles

The article presents material solution based on the application of ceramic dust as concrete mix component intended for airfield pavements. The applied dust influences the changes in internal structure of concrete composite. Diversification of internal microstructure of cement concrete using the suggested dust has significant influence on the improvement of compressive strength. The laboratory analyses included concretes curing in standard conditions and concretes subject to thermal cycles representing the destructive influence of imposed loading. Comparative SEM observations of concretes subject to 50 thermal cycles proved significant influence of dust on internal structure of composite. In the study 6 samples were selected, which, each time, were intended for the laboratory tests. The applied similarity analysis of distance courses in case of this concrete. Similarity indexes between input and target sequence were defined. Diagrams presenting the similarity of the analysed concretes were prepared (after 28 days of curing and after 50 thermal cycles). It was proved that the suggested method can be used to assess the elements content and define the similarity of concrete intended for airfield pavements in the selected of areas (cement matrix, contact area between fine aggregate and cement matrix, contact area between coarse aggregate and cement matrix and contact area between air voids and cement matrix)

Application of similarity method of distance courses describing the elements content in typical cement concrete after thermal cycles

The work concerns the use of similarity analysis of distance course. Composition of concrete mixes was designed. The cement concrete composition includes cement, coarse aggregate, fine aggregate, water and admixtures. The laboratory analyses included concretes curing in standard conditions and concretes subject to thermal cycles representing the destructive influence of imposed loading. Laboratory tests assumed the fifty thermal test cycles. A single test cycle included process of alternate heating and cooling. Recurrent influence of temperature stimulated the impact of aircraft on airfield pavements. The assumed heating and cooling time corresponded to the time during which the aircraft effected the most frequently used airfield pavement within the area of Poland. Comparative SEM observations of concretes subject to thermal cycles were conducted. An increase in the width of microcracs has been observed. In case of crystallization, there is diversification within the area of cement matrix, contact area between cement matrix and aggregate grains and in case of porosity characteristics of both concretes. Similarity indexes between input and target sequence were defined. Diagrams presenting the similarity of the analysed concretes were prepared (after 28 days of curing and after thermal cycles). It was proved that the suggested method could be used to define the similarity of concrete intended for airfield pavements

Wybrane aspekty oceny stanu technicznego betonowych nawierzchni lotniskowych w ujęciu trwałości eksploatacyjnej

The paper presents the essence of airport pavements’ durability in terms of its condition’s evaluation. It features a discussion of selected research methods for the most important pavement parameters. It was proposed to expand the existing pavement condition evaluation process with selected verification methods. The use of geo-radar measurements in connection with the specification of the pavement concrete’s durability and concrete pavement’s internal structure analysis seems to be a necessary element supplementing the currently used evaluation procedure.W artykule przedstawiono istotę trwałości nawierzchni lotniskowych w kontekście oceny stanu nawierzchni. W ramach rozważań omówiono wybrane metody badawcze dla najważniejszych parametrów nawierzchniowych. Zaproponowano rozszerzenie istniejącego procesu oceny stanu nawierzchni o wybrane metody weryfikacyjne. Wykorzystanie pomiarów georadarowych w powiązaniu z określeniem wytrzymałości betonu w nawierzchni i analizą struktury wewnętrznej kompozytu betonowego wydaje się nieodzownym elementem uzupełniającym stosowaną obecnie procedurę oceny

Thermal Stress in Concrete Slab of the Airfield Pavement

Stress occurring in concrete pavement slab changes on daily and annual basis. Daily changes of air temperature in between environments depend on the following: latitude where the structure is located and season. Change of air temperature causes the variable thermal stress of a slab and consequently change of its linear dimensions (slab extension or shortening. “Thermal balance of pavement” prepared for individual structure solutions, should be the basis for construction design and geometric solutions concerning air field structure. This publication refers only to natural changes of temperature conditions of the environment. Other phenomena occurring on concrete airfield pavement under the influence of imposed thermal loads will be the subject of another publication in this regard

Intra-Rater Reliability of Shear Wave Elastography for the Quantification of Respiratory Muscles in Adolescent Athletes

The aim of this study was to assess the intra-rater reliability and agreement of diaphragm and intercostal muscle elasticity and thickness during tidal breathing. The diaphragm and intercostal muscle parameters were measured using shear wave elastography in adolescent athletes. To calculate intra-rater reliability, intraclass correlation coefficient (ICC) and Bland–Altman statistics were used. The reliability/agreement for one-day both muscle measurements (regardless of probe orientation) were at least moderate. During the seven-day interval between measurements, the reliability of a single measurement depended on the measured parameter, transducer orientation, respiratory phase, and muscle. Excellent reliability was found for diaphragm shear modulus at the peak of tidal expiration in transverse probe position (ICC3.1 = 0.91–0.96; ICC3.2 = 0.95), and from poor to excellent reliability for the intercostal muscle thickness at the peak of tidal inspiration with the longitudinal probe position (ICC3.1 = 0.26–0.95; ICC3.2 = 0.15). The overall reliability/agreement of the analysed data was higher for the diaphragm measurements (than the intercostal muscles) regardless of the respiratory phase and probe position. It is difficult to identify a more appropriate probe position to examine these muscles. The shear modulus/thickness of the diaphragm and intercostal muscles demonstrated good reliability/agreement so this appears to be a promising technique for their examination in athletes