Variation in Compressive Strength of Concrete aross Thickness of Placed Layer

This article focuses on the development of nanoalumina-based cement mortars for overlay applications in concrete floors. It focuses on the effect of applying aluminum oxide (Al2O3) nanopowder to the cement mortar used to make the overlay, on the adhesion of this overlay to concrete substrate and on its functional properties. It was claimed that the addition of 0.5% of Al2O3 nanopowder has a positive effect on the adhesion of the cement mortar used to make the overlay to the substrate made of concrete. The prior studies performed using scanning electron microscopy (SEM) confirmed that the reason for the improvement in adhesion is the fact that cement mortar used to make the overlay with the addition of 0.5% of Al2O3 nanopowder is less porous than the reference mortar within the interphase. The article concurs that the most favorable results, in terms of lower abrasion resistance and higher subsurface tensile strength of the cement mortar used to make the overlay, are mainly brought about by adding 0.5% of Al2O3 nanopowder.

Section: Methodsmentioning

confidence: 99%

The Development of Nanoalumina-Based Cement Mortars for Overlay Applications in Concrete Floors

Szymanowski

Sadowski

2019

“…The CV ranged from 1.4-7.1% for composites containing less fly ash and 1.9-9.7% for concretes richer in fly ash. Such values could be considered satisfactory if they were assessed in the context of ordinary concrete with a similar strength, whereas given other composite material and specimens sizes, there are no particular guidelines for such an assessment [25,26].…”

Section: Flymentioning

confidence: 99%

Long-Term Compressive Strength of Polymer Concrete-like Composites with Various Fillers

Sokołowska

2020

The durability of building composites with polymer matrix, such as polymer concretes, is considered high or excellent. However, very few studies are available that show the properties of such composites tested long after the specimens' preparation, especially composites with fillers other than traditional rock aggregates. The paper presents the long-term compressive strength of polymer concrete containing common and alternative fine fillers, including quartz powder (ground sand) and by-products of the combustion of Polish fossil fuels (coal and lignite), tested nine or 9.5 years after preparation. The results were compiled with the data for respective specimens tested after 14 days, as well as 1.5 and 7 years. Data analysis confirmed the excellent durability of concrete-like composites with various fillers in terms of compressive strength. Density measurements of selected composites showed that the increase in strength was accompanied by an increase in volumetric density. This showed that the opinion that the development of the strength of composites with polymer matrices taking place within a few to several days was not always justified. In the case of a group of tested concrete-like composites with vinyl-ester matrices saturated with fly ashes of various origins, there was a further significant increase in strength over time.wastes or by-products are applied to the aforementioned composites as the substitutes of the regular components. Such composites have been recently eagerly designed and produced, following the assumptions of the sustainable development concept, i.e., a concept strongly promoted for the past few years. Composites containing such wastes and/or by-products (e.g., fly ash, perlite powder, recycled glass, aggregate leftover mineral dust, etc.) are subjected to various tests [5][6][7][9][10][11][12][13], but usually only at the early stage of their service-life. The level of mechanical properties of such composites after a long period of use remains unclear.The aim of the paper is to discuss the "long-term compressive strength" of polymer concretes with traditional quartz fillers (including coarse and fine aggregates, the same as those used in ordinary Portland cement concrete and very fine quartz powders) and sustainable secondary materials, namely the by-products of the combustion of two kinds of fossil fuels, i.e., coal (or so-called "hard coal") and lignite (or "brown coal"), mined in deposits located in Poland. The combustion processes are intended to produce electricity or heat. Due to differences in the construction of furnaces and associated combustion installations, the remaining fly ashes differ in terms of morphology and granulation, so they differently affect the consistency of PC mix [13] which, among others, influences the microstructure and, therefore, the properties of hardened composites containing such fly ashes.The tested composites are cement-free (the binder consists solely of vinyl-ester resin). There is also no water in the composition of these composites. Water disturbs or...

“…In paper [32] the author asked a question: is the variation in the compressive strength of concrete across the thickness of horizontally cast elements negligibly small, or rather, does it need to be taken into account at the design stage? In order to determine if the compressive strength of concrete varies across the thickness of horizontally cast elements, ultrasonic tests and destructive tests were carried out on core samples taken from a 350 mm thick slab made of class C25/30 concrete.…”

Section: Description Of the Articles Presented In The Issuementioning

confidence: 99%

“…The correlation between the velocity of the longitudinal ultrasonic wave and the compressive strength of the concrete in the slab was determined It was found that the destructively determined compressive strength varied only slightly (by 3%) across the thickness of the placed layer of concrete, whereas the averaged ultrasonically determined strength of the concrete in the same samples does not vary across the thickness of the analyzed slab. Therefore, it was concluded that the slight increase in concrete compressive strength with depth below the top surface is a natural thing and need not be taken into account in the assessment of the strength of concrete in the structure [32].…”

Section: Description Of the Articles Presented In The Issuementioning

confidence: 99%

Non-Destructive Testing of Materials in Civil Engineering

Schabowicz

2019

This issue was proposed and organized as a means to present recent developments in the field of non-destructive testing of materials in civil engineering. For this reason, the articles highlighted in this editorial relate to different aspects of non-destructive testing of different materials in civil engineering, from building materials to building structures. The current trend in the development of non-destructive testing of materials in civil engineering is mainly concerned with the detection of flaws and defects in concrete elements and structures, and acoustic methods predominate in this field. As in medicine, the trend is towards designing test equipment that allows one to obtain a picture of the inside of the tested element and materials. Interesting results with significance for building practices were obtained.