This paper describes a study conducted to evaluate the effect of texturing of the surface of concrete substrate on the pull-off strength (fb) of epoxy resin coating. The paper investigates a total of seventeen types of textures: after grooving, imprinting, patch grabbing and brushing. The texture of the surface of the concrete substrate was prepared during the first 15 min after pouring fresh concrete into molds. The epoxy resin coating was laid after 28 days on hardened concrete substrates. To investigate the pull-off strength of the epoxy resin coating to the concrete substrate, the pull-off method was used. The results were compared with the results obtained for a sample prepared by grinding, normative minimal pull-off strength values and the values declared by the manufacturer. During this study twelve out of fifteen tested samples achieved a pull-off strength higher than 1.50 MPa. It was found that one of the imprinting texturing methods was especially beneficial.
Nowadays, the recycled fine aggregate sourced from construction and demolition waste is not frequently used in manufacturing of epoxy resin coatings. Therefore, the main novelty of the article is to prepare green epoxy resin coatings modified with recycled fine aggregate in a replacement ratio of natural fine aggregate ranged from 20 to 100%. The microstructural properties of the aggregates and epoxy resin were analyzed using micro-computed tomography, scanning electron microscopy and nanoindentation. The macroscopic mechanical properties were examined using pull-off strength tests. The highest improvement of the mechanical properties was observed for epoxy resin coatings modified with 20% of natural fine aggregate and 80% of recycled fine aggregate. It has been found that even 100% of natural fine aggregate can be successfully replaced using the recycled fine aggregate with consequent improvement of the pull-off strength of analyzed epoxy resin coatings. In order to confirm the assumptions resulting from the conducted research, an original analytical and numerical failure model proved the superior behavior of modified coating was developed.
This paper presents an experimental study on the assessment of the cement-based materials properties made with marble powder (MP) at different replacement ratios (0%, 5%, 10%, and 15%) of cement by using the ultrasonic pulse velocity (UPV) test. The used MP has a Blaine fineness similar to that of Portland cement. The physical and the chemical characteristics of Portland cement and MP were determined. To determine the UPV values, cubic specimens (50 × 50 × 50 mm3) of cement paste and mortar were prepared and cured either in air at a temperature equal to 22 ± 2 °C and relative humidity equal to 20 ± 1%, or in water at a temperature equal to 20 ± 1 °C. The experimental tests including the UPV, the compressive strength (fcd), and the apparent density (ϒad) were conducted at 3, 7, 28, and 65 days, the relationship between each of these parameters were presented. Additionally, economic performance of cement and waste MP used in this study was performed. The results show that the use of MP as partial replacement of cement causes a decrease in the compressive strength and apparent density in both curing conditions. In addition, the results show a good relationship between the destructive test and non-destructive test adopted by UPV.
The influence of polypropylene fibres on the properties of fresh and hardened concrete Wpływ dodatku włókien polipropylenowych na właściwości mieszanki betonowej oraz betonu stwardniałego Abstract The purpose of the article is to determine the effect of the addition of polypropylene fibres on the properties of concrete mixtures and hardened concrete. To this end, both destructive and non-destructive tests were conducted. The concrete mixture tests included the testing of the consistency, air content and bulk density of the concrete mixture. Investigations of hardened concrete were based on the determination of compressive strength by destructive tests, sclerometer and ultrasonic methods and tensile strength in bending tests. All tests were performed for seven series of concrete mixtures, differing in their fibre content. The results showed that the addition of polypropylene fibres to the concrete mixture causes changes in consistency, increases air content, and does not increase the compressive and tensile strength of concrete. It was also observed that the addition of polypropylene fibres does not cause significant changes in the bulk density of the concrete mix. StreszczenieTematem artykułu jest określenie wpływu dodatku włókien polipropylenowych na właściwości mieszanki betonowej oraz betonu stwardniałego. W tym celu przeprowadzono badania świeżej mieszanki betonowej oraz betonu stwardniałego (niszczące oraz nieniszczące). W skład badań mieszanki betonowej wchodziły: badanie konsystencji mieszanki betonowej, badanie zawartości powietrza w mieszance betonowej, badanie gęstości objętościowej mieszanki betonowej. Badania betonu stwardniałego opierały się na pomiarze wytrzymałości betonu na ściskanie, wytrzymałości betonu na rozciąganie przy zginaniu, wytrzymałości betonu na ściskanie metodą sklerometryczną oraz wytrzymałości betonu na ściskanie metodą ultradźwiękową. Wszystkie badania zostały wykonane dla siedmiu serii mieszanek betonowych, różniących się od siebie zawartością włókien. Dodatek włókien polipropylenowych do mieszanki betonowej powoduje zmiany jej konsystencji oraz podwyższenie w niej zawartości powietrza. Włókna polipropylenowe nie powodują istotnych zmian gęstości objętościowej mieszanki betonowej.Słowa kluczowe: fibrobeton, włókna polipropylenowe, zbrojenie rozproszone, mieszanka betonowa, beton stwardniały
This article presents studies that were performed in order to improve the subsurface properties of horizontally-formed cementitious composites using tin(II) fluoride nanoparticles. The main aim of the study was to solve the problem of the decrease in subsurface properties caused by mortar bleeding and the segregation of the aggregate along the height of the overlay. The article also aims to highlight the patch grabbing difficulties that occur during the process of forming horizontally-formed cementitious composites. Four specimens were analyzed: one reference sample and three samples modified with the addition of 0.5, 1.0, and 1.5% of tin(II) fluoride nanoparticles in relation to the cement mass. To analyze the mechanical properties of the specimens, non-destructive (ultrasonic pulse velocity) and destructive tests (flexural tensile strength, compressive strength, abrasion resistance, pull-off strength) were performed. It was indicated that due to the addition of the tin(II) fluoride, it was possible to enhance the subsurface tensile strength and abrasion resistance of the tested cementitious composites. To confirm the obtained macroscopic results, the porosity of the subsurface was measured using SEM. It was also shown that the addition of the tin(II) fluoride nanoparticles did not reduce its flexural and compressive strength. The results show that horizontally-formed cementitious composites with the addition of 1.0% of tin(II) fluoride nanoparticles in relation to the cement mass obtained the most effective mechanical performance, especially with regard to subsurface properties.
The effect of the concentration of steel fibres on the properties of industrial floors Wpływ zawartości włókien stalowych na właściwości posadzek przemysłowych Abstract This paper presents the results of a series of experiments on samples made of steel fibre reinforced concrete. The investigated samples were made with different concentrations of steel fibres ranging from 20.0 to 32.5 kg/m3. Twenty-one cubic samples (15 x 15 x 15 cm) and fourteen cuboid samples (15 x 15 x 60 cm) were used for this investigation. The article focusses on the effect of the concentration of steel fibres on the properties of industrial floors. for this purpose, both destructive and non-destructive methods were used and compared. as a result of this study, it has been proved that compressive and flexural tensile strength are lower with increasing air content and decreasing density of concrete. moreover, it was found that there is a correlation between ultrasonic pulse velocity and rebound hammer results which together can be used to estimate the compressive strength of steel fibre reinforced concrete. Streszczenie W niniejszym artykule przedstawiono wyniki serii eksperymentów wykonanych na próbkach z betonu zbrojonego włóknami stalowymi. badane próbki zbrojone były różną zawartością włókien stalowych od 20.0 do 32.5 kg/m3. Do badań użyto 21 sześciennych (15 x 15 x 15 cm) i 14 prostopadłościennych (15 x 15 x 60 cm) próbek betonowych. W artykule skupiono się na zbadaniu wpływu zawartości włókien stalowych na właściwości posadzek przemysłowych. Do badań zastosowano i porównano metody niszczące oraz nieniszczące. W rezultacie udowodniono, że wytrzymałość na ściskanie i rozciąganie przy zginaniu zmniejsza się wraz ze wzrostem zawartości powietrza i malejącą gęstością betonu. Ponadto stwierdzono, że istnieje korelacja między wynikami ultradźwiękowymi i sklerometrycznymi, które mogą być wykorzystane do oszacowania wytrzymałości na ściskanie betonu zbrojonego włóknami stalowymi. Słowa kluczowe: włókna stalowe, posadzki przemysłowe, metody nieniszczące
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