Effect of Physical Treatment on the Properties of Composites Based on Natural Fibres

Due to the low density and high porosity of the hemp hurds, the combination of hemp and binder creates a building material with good thermal and acoustic insulation properties. Today hemp hurds can be used in high-quality products such as hemp concrete, fibre board and composites.In this paper, the attention is given to the study of the properties of lightweight composites based on modified hemp hurds as filler and MgO-cement as binder. The cohesion of the filler and of the binder is an important factor in the development of mechanical properties. The impact of ultrasonic treatment of hemp hurds and its cooking in water for 1h on the physical and mechanical properties (compressive strength, density, water absorbability, thermal conductivity) of the composites hardened in indoor condition was studied. The observation is also focused on the influence of the hemp hurds length. The durability of produced composites was studied under different conditions

13-cis-retinoic acid re-differentiation therapy and recombinant human thyrotropin-aided radioiodine treatment of non-Functional metastatic thyroid cancer: a single-center, 53-patient phase 2 study

In 30–50% of patients with metastatic non-medullary thyroid cancer the metastases are not radioiodine-avid and so there is no effective treatment. Retinoids have demonstrated inhibition of thyroid tumor growth and induction of radioiodine uptake. The aim of our study was to assess benefits of the retinoic acid (RA) treatment to re-differentiate non-functional NMTC metastases

Effect of Surface Modifications of Recycled Concrete Aggregate on Concrete Properties

The experiment aims to test the specific way of producing concrete with recycled concrete aggregate (RCA). To reduce its negative impact on the concrete properties, two different ways of treatment of the RCA with geopolymer slurry were applied—coating during the mixing using the specific mixing approach and coating prior to the mixing of concrete. As control samples, a mixture prepared by natural aggregate only and a mixture with RCA that was prepared by standard mixing with no coating process were tested as well. The results of density, total water absorption, and compressive strength in periods of 28, 90, 180, and 365 days of curing are presented and evaluated. Both methods of coating of the RCA with geopolymer slurry allow for the preparation of concrete with properties comparable to those of normal concrete (prepared by standard mixing with natural aggregate); thus, it seems to be a promising way to enhance the rate of RCA application. The positive effect of coating is clearly visible after a longer period of curing (180 days). When comparing the methods of RCA coating, coating directly during the mixing yields somewhat better results; it is also positive from the technological point of view, since the process is simpler in practice

Sustainable Use of Reservoir Sediment through Partial Application in Building Material

Sediment, often considered a by-product of various activities within river basin management to be disposed of, or a pollutant to be controlled, is increasingly being acknowledged as a resource in need of management. The paper deals with the possibility of reusing sediment from two Slovak reservoirs (Klusov and Ruzin) as an alternative raw material in concrete production. Concrete specimens were prepared by a combination of original reservoir sediment, reservoir sediment mechanically activated by dry milling, reservoir sediment mechanically activated by dry milling together with biomass incinerator fly-ash as a binder. To improve the strength properties of specimens, sodium hydroxide (NaOH) was used as a sediment activator. Mixtures containing 40% of binder replacement by the above-mentioned combinations of original and treated sediments were tested for flexural and compressive strengths after 28, 90 and 365 days of curing. The results showed that the mixtures prepared from sediments milled without and with addition of fly ash as cement replacement satisfied the strength requirements for the compressive strength class C16/20 according to the European standard except the composites prepared with NaOH as the sediment activator. Addition of NaOH into composites in the concentration of 5 M as an activator of sediment indicated the negative impact on compressive and flexural strengths and thus NaOH was not an effective pozzolanic activator for sediments. This study reveals that the sediment may be considered as 40% cement substitution in building materials

Natural aggregate totally replacement by mechanically treated concrete waste

This paper presents the results obtained from the research focused on the utilization of crushed concrete waste aggregates as a partial or full replacement of 4/8 and 8/16 mm natural aggregates fraction in concrete strength class C 16/20. Main concrete characteristics such as workability, density and compressive strength were studied. Compressive strength testing intervals for samples with recycled concrete aggregates were 2, 7, 14 and 28 days. The amount of water in the mixtures was indicative. For mixture resulting consistency required slump grade S3 was followed. Average density of all samples is in the range of 2250 kg/m3 to 2350 kg/m3. The highest compressive strength after 28 days of curing, 34.68 MPa, reached sample, which contained 100% of recycled material in 4/8 mm fraction and 60% of recycled aggregates in 8/16 mm fraction. This achieved value was only slightly different from the compressive strength 34.41 MPa of the reference sample

Assessment of ecological stability of the built environment in relation to sustainable construction

When placing buildings in a landscape environment, the urban and architectural design of the building must be in harmony with the surrounding environment. The environmental criterion in assessing the sustainability of buildings and the subsequent environmental certification of buildings is the construction site selection in terms of its ecological importance. The way to determine the ecological value of a territory is through the determination of the landscape’s ecological stability, which can be considered as a basis for assessing all conditions and assumptions of land use. Maintaining ecological stability on Earth is a prerequisite for sustainable development and is of long-term strategic importance for the development of society

Effect of Silica Fume as a Component of Alternative Binder on the Selected Technically Important Characteristics of Bio-Aggregate-Based Composites

This experimental study was focused on the application of an alternative binder based on MgO, and the variation of its components by the combination of two MgO products obtained by the calcinations of natural magnesite, siliceous materials (river sand and silica fume), and alkaline admixture in the mixture for a preparation of composite based on biomass waste such as hemp hurds as organic filler. This paper presents the results of the effect of an MgO binder composition on the compressive strength of the bio-aggregate-based composites. Other physical properties, such as the bulk density, thermal conductivity coefficient, and water absorption, were also investigated. The measured strength parameters of the bio-composite samples that were hardened for 28 days demonstrate that the binder consisting of optimal calcined MgO and silica fume as a total replacement for sand ensures a good binding of the matrix with hemp hurd compared to other varied compositions of alternative binder. No significant differences in bulk density and thermal conductivity values were found for these composites. However, the bio-composite specimen with an MgO⁻SiO2 matrix had the highest compressive strength and achieved the lowest value of water absorption. An increase in hardening time of up to 90 days led to a significant improvement of strength as well as reduction in permeability

Color pigments in concrete and their properties

Nowadays, color concrete pigments are used to revive space in the construction of new buildings, reconstruction existing buildings and squares. Color pigments represent a partial weight replacement of the binder. Color pigmented concrete also has properties like traditional concrete namely high strength, good durability and weather resistance for its variable use. In this paper, characterization and classification of color pigments, using and their influence on the properties of concrete is given. The experimental part of concrete composites studying (with color pigments) includes testing of physical and mechanical properties in comparison to reference sample (without color pigments)

Concrete samples prepared with different types of wastes

This paper is focused on utilization of coal fly ash, steelmaking slag and glass bottle fragment in concrete production. Each of these wastes was mixed into concrete, and compressive strength was tested.The first part of this paper is focused on Portland cement replacement by mechanochemical activated coal fly ash and the second part is aimed to natural aggregate replacement by steelmaking slag and glass bottle fragment in concrete mixture. The results showed that coal fly ash has a positive influence on compressive strength development, and steelmaking slag and glass waste can be successfully used as a natural aggregate replacement

Properties monitoring of fibrous composites based on hemp hurds with different mean particle size

In this paper, the effect of mean particle length of hemp hurds on compressive strength and other parameters of fibrous-composites is studied. Hemp hurds of various origin (Hungarohemp LTd, Nagylak, Hungary; Hempflax, Netherlands) with a wide particle size distribution were used in the experiments. Six samples of hemp hurds with various mean particle length (from 7.3 mm to 39.9 mm) were used for the preparation of fibrous composites based on MgO-cement as a binder. Bulk density, compressive strength, thermal conductivity and water absorbability of fibrous composites after 28 days of hardening were tested. The impact of men particle length of hemp hurds slices on values of bulk density, compressive strength and water absorbability of hardened composites was confirmed