Analysis of the mechanical resistance of cement with aggregates of petrous endocarp from macadamia nut

This research evaluates if adding crushed macadamia nutshell to a mixture of cement and sand could result in lighter and more resistant constructive materials. The mechanical resistance under compression of cement blocks made from two different experimental mixtures, in which a certain amount of sand is replaced with crushed nutshell, is compared against two control groups. Results show that blocks made from one of the proposed mixtures got an average resistance around 50% above the controls group while being 3% lighter. Additionally, the physical dependence of the strength of the blocks on the granulometry of the aggregated endocarp fragments, and their percentage to the volume of cement, was studied thanks to contour plots developed from a factorial design of the data.

Development of welded structure of 5-nozzle lance heads in converter shop of PJSC “Dneprovsky metallurgical combine”

For the upper blasting lances of 250-tons oxygen converters at PJSC «DMС» (Kamenskoe, Ukraine) the author has proposed a number of welded structures of 5-nozzle lance heads with increased resistance. A set of industrial studies of their operation made it possible to establish that the devices which provide cooling of the areas back from the nozzle zone of the tip have the highest resistance. Measures to increase the values of the average cooler speeds in welded structures of the lance heads and their rigidity also turned out to be quite effective. The transfer of copper welds holding the nozzle inserts in the copper tip from its outer surface to the inner proved to be ineffective from the point of increasing resistance of the lance head (the average resistance of the heads increased by only 7 heats – from 78 to 85 heats). This allows us to assert the need for complete elimination of copper welds in the head (both external, exposed to high-temperature and mechanical stresses, and internal) that hold nozzle inserts in the holes of the welded tip and lance head collector. Thus, in spite of all the measures taken to transfer the welds from the outer surface of the tip to its inner surface, to improve cooling of the tip and its back from the nozzle zones, which also include sections of copper welds around the nozzles, as well as to increase the rigidity of the blast welded structure heads, this led, although to positive, but still to relatively low results. The data obtained indicate that welds made of copper around the nozzle inserts, which are held by this in the tip (also in the collector) of the head, are the limiting link that does not significantly increase the resistance of welded lance heads, and it is urgently necessary to back off its use.

Barnyardgrass (Echinochloa crus-galli (L.) P. Beauv.) resistance to acetolactate synthase-inhibiting and other herbicides in rice in Turkey

Barnyardgrass (Echinochloa crus-galli (L.) P. Beauv.) is one of the most yield-limiting weeds in rice in Turkey. Barnyardgrass resistance to common herbicides has been reported worldwide; however, such information is largely lacking in the country. The objective of this study was to determine the resistance spectrum of different barnyardgrass populations to the most commonly-used herbicides in rice in Turkey. The susceptibility of 40 barnyardgrass populations was evaluated. The samples were collected from fields with intensive rice cultivation in Balıkesir and Çanakkale provinces. Seeds were picked from barnyardgrass plants suspected to be herbicide-resistant because of their survival in the rice fields after herbicides application. A total of 38 populations were resistant to penoxsulam, and the resistance index of these populations ranged from 2 to 39. A total of 24 out of the 38 barnyardgrass populations showed a GR₅₀ (herbicide dose causing a 50% reduction in plant dry matter) value higher than the recommended penoxsulam dose (20.2 g a.i./ha) in rice. Among these 24 barnyardgrass populations, 25, 29.2 and 45.8% populations exhibited high, moderate and low level of penoxsulam resistance, respectively. From the penoxsulam-resistant populations (38), the response of 14 populations (low to high resistance to penoxsulam) to six commonly-used herbicides for barnyardgrass control in rice was evaluated. The selected 14 populations showed resistance to almost all herbicides tested, with the lowest average resistance being determined against profoxydim and the highest average resistance against molinate herbicide. Resistance levels against six commonly-used herbicides in rice ranged from 2 to 34.

Efficiency of fertilizers while cultivation of the winter durum wheat variety “Agat Donskoy" in the southern part of the Rostov region

Over the years of research, the winter durum wheat variety “Agat Donskoy” sown in weedfree fallow showed a good resistance to lodging with no fertilizing (4 points), average resistance to lodging (3 points) with two nitrogen dosings: in spring in thawed frozen soil (N30) and in the period of earing (N30). The winter durum wheat variety “Agat Donskoy” sown after sunflower showed a high tolerance to lodging (5 points) for 3 years on average. Sown in weedfree fallow the largest productivity (6.09 and 6.13 t/ha) and the surplus to the control (0.54 and 0.57 t/ha) were formed by the variety when fertilizing with the basic dosing (P60K40) and with one or two nitrogen dosings (N30 in spring in thawed frozen soil and in the period of earing). At the same time, the grain had a high percentage of protein 15% and gluten 28.1% that corresponded to the 1st quality class. The winter durum wheat variety “Agat Donskoy” sown in weedfree fallow proved to be highly profitable (at the level of 163-201%). The winter durum wheat variety “Agat Donskoy” sown after sunflower produced the largest surplus of yield (1.00 and 1.25 t/ha) when fertilizing with N40P60K40 and the use of one or two nitrogen dosings (N30 in spring in thawed frozen soil and in the period of earing). The profitability of the variety sown after sunflower was 113-147%. According to the GOST the obtained characteristics allow referring the winter durum wheat variety “Agat Donskoy” to the 2-3d quality class.

ANÁLISE DAS PROPRIEDADES DO CONCRETO UTILIZANDO RESÍDUOS DA CONSTRUÇÃO CIVIL

The impacts caused by RCCs are growing exponentially each year, which is why it is necessary to create measures to mitigate and minimize such an effect. The purpose of this research was to evaluate the physicalmechanical properties of the concrete from the gradual replacement of the natural fine aggregate by the recycled aggregate. The recycled concrete was made with substitutions of 20, 40, 60, 80 and 100% of recycled aggregate, whose water / cement factor was 0.7. Test specimens were produced and after the cure time of 7, 14 and 28 days the specimens were ruptured. It was possible to analyze that with the increase of the recycled aggregate substitution, the concrete strength increased, but did not reach an average resistance of 20 Mpa. Therefore it is possible to conclude that the use of recycled aggregate in the manufacture of low resistance concrete is.

Mechanical characterization of concrete block used on infill masonry panels

Purpose The infill masonry walls in recent worldwide earthquakes have shown that it is necessary to conduct further studies to characterize the behavior of existing buildings and, in particular, of infill masonry walls under seismic activity. The lack of characterization studies of infill walls made by concrete blocks justifies the investigation reported herein, which includes experimental tests on sample sets to evaluate the mechanical properties of masonry components (units and mortar) and assemblages (wallets) made with masonry units from Faial. For the later, normal compressive, diagonal tensile/shear and out-of-plane flexural strengths were obtained according to standard procedures, the results of which are presented in the manuscript. The paper aims to discuss these issues. Design/methodology/approach One experimental campaign was conducted with the aim to mechanically characterize concrete blocks masonry samples. Several experimental tests were carried out in full-scale masonry concrete wallets according to the constructive methodology used. Findings Based on the data obtained from the mechanical characterization tests of the concrete masonry blocks, it can be seen that under simple compression, the masonry specimens’ average resistance is about 6 times superior than the average resistance to diagonal shear/tension, while the stiffness is almost doubled. In simple compression tests, it was observed that the masonry specimens cracked in areas of higher drilling of the blocks. In the tensile tests by diagonal compression, it was found that the test specimens were mainly fissured by the block/mortar joint interfaces, following the delineation of settlement and top joints. Originality/value There are no experimental results available in the literature for this type of bricks that can contribute to the development of numerical studies.

Assessing specific gravity of young Eucalyptus plantation trees using a resistance drilling technique

The resistance drilling technique has been in focus for assessing the specific gravity (SG) of young Eucalyptus trees from plantations for pulpwood production. Namely, the data of 50 34-month-old and 50 62-month-old trees from Eucalyptus grandis×Eucalyptus urophylla clonal plantations was evaluated, while the relative resistance profiles were collected with the amplitude in a scale from 0 to 100% of each tree at the breast height. For laboratory determination of SG and moisture content (MC), 3-cm-thick disks were taken at breast height. The average resistance amplitude of a full drill penetration or a half-diameter penetration showed weak correlations with SG for both 34-month-old and 62-month-old trees. However, when the two age classes were combined, the strength of the relationship was improved significantly, with a correlation coefficient ranging from 0.71 to 0.77 with respect to SG determined from strip samples and from 0.59 to 0.72 with respect to SG determined from wedge samples. The drill penetration depth had a significant effect on the relationship between average amplitude and SG. A clear trend of weakening correlation was observed with increasing drill penetration. As a result, the average resistance amplitude of a half-diameter drilling (from bark-to-pith) is more advantageous for assessing the SG of young Eucalyptus trees than a whole-diameter drilling.