Shear friction capacity of self-consolidating concrete

An experimental research was developed to evaluate shear transfer in self-consolidating. Three concrete mixes were prepared, one conventional and two self-consolidating, differing on the proportion of the coarse and fine aggregate used. Nine push-off specimens, containing steel reinforcement passing through the shear plane, were tested, to evaluate the ultimate shear stress and shear plane displacements. Shear strength of self-consolidating concrete specimens were higher than conventionally vibrated concrete. The experimental results were compared to the shear strength estimated by literature and code based equations, yielding conservative results of these equations for both types of concrete, especially the models that disregard the compressive strength of concretes.

Effects of Microbial Transglutaminase on Technological, Rheological, and Microstructural Indicators of Minced Meat with the Addition of Plant Raw Materials

The aim of the study was to analyse the effects of transglutaminase on the physicochemical, technological, rheological, and microstructural indicators of minced meat with the addition of plant raw materials. The formulations of minced meat from beef trimming, hemp protein, and flax flour were optimized in terms of biological value and optimal content of essential amino acids. The addition of plant components in amounts greater than 18% caused an increase in the content of protein, fat, and ash in the minced samples. The rheological properties of minced meat samples without enzyme treatment changed depending on the proportion of plant raw materials. When the content of the flax flour was increased, the minimum ultimate shear stress and viscosity were observed, while the maximum values for these indicators were achieved in samples containing about 15% hemp protein, as well as in samples without plant additives. When adding transglutaminase to the formulation, increases in the ultimate shear stress and viscosity were proven for all combined minced samples. The combined minces, containing flax flour, had a more plastic structure and the lowest modulus of elasticity, while minces including 14% hemp protein or more than 87% meat components were identical to the control samples in terms of deformation and elasticity. In enzyme-treated minces, the plasticity of the samples reduced while density and elasticity increased. Transglutaminase treatment contributed to the formation of optimal technological properties of combined minces. Microstructural analysis showed the intermolecular bonds between protein particles in combined minced samples with the addition of enzymes. The research results have demonstrated the effectiveness of using transglutaminase in the composition of combined minced meat for the formation of a homogeneous and dense system with the necessary technological and rheological properties.

The Influence of Nanotechnogenic Raw Materials on the Drying Properties and Physical and Mechanical Properties of Ceramic Bricks

When obtaining ceramic bricks only from low-melting clay with the number of plasticity less than 12 without the use of thinners, there is a sharp drop in the limiting shear stress in the temperature range of 20-80oC, which contributes to the appearance of cracks and deformation curvatures of products. The use of nanotechnogenic raw materials as a thinner does not contribute to a sharp drop in the ultimate shear stress of the semi-finished brick in the temperature range of 20-80oC, eliminates the appearance of cracks and increases the physical and mechanical performance of the finished product. Studies have shown that in order to improve the drying properties of the ceramic mass, the system «nanotechnogenic raw materials-fusible clay-water» is more homogeneous in relation to the system «clay-water». The analysis of the ultimate shear stress in hot forming conditions showed that the function of dependence of plastic strength on molding humidity PM =f (W,t) than the function of dependence of plastic strength on temperature PM =f(t) acquires special importance in this case.

The study of the maximum shear stress of the composition of pyrophyllite - clay component – water at elevated temperatures

A sharp decrease in the ultimate shear stress in the range of 20‒80 °C is observed when obtaining samples from the clay component without descendents. This contributes to the appearance of cracks and defects in the samples. The use of pyrophyllite in ceramic masses in obtaining samples ensures a gradual decrease in the ultimate shear stress Pm in the range of 20‒80 °C. It is shown that to improve the drying properties of the samples, the composition of pyrophyllite ‒ clay ‒ water is more homogeneous than the composition of clay ‒ water. Analysis of the Pm of the samples under the conditions of hot forming showed that it is not so much the dependence Pm = f(t) that takes on special importance, but the dependence Pm = f(W, t), where t ― the temperature; W ― the humidity. Ill. 1. Ref. 8. Tab. 2.

Research of the plastic strength of alumina mass for molding corundum ceramics by extrusion depending on them humidity

One of the characteristics that makes it possible to evaluate the plasticity and formability of ceramic masses is the plastic strength of structure — the ultimate shear stress that the plastic mass can withstand under static stress. The dependence researches of the plastic strength of alumina masses from alumina MARTOXID and CT 3000 brands on a flour binder on their humidity and keeping time were carried out. The determination of the plastic strength of the masses was carried out on a KP-3 conical plastometer, for which purpose a cone with an apex angle of 30о was used (mass of the cone together with rod is 0.8056 kg). The optimum humidity of alumina masses for the molding of corundum ceramics by extrusion from alumina MARTOXID brand is 19 % and from alumina CT 3000 brand is 20 % were established. In depending on technological needs and capabilities were set that, the keeping time of alumina masses with the optimum humidity can be 1—7 days. The samples of corundum ceramics received by extrusion from the alumina mass of alumina MARTOXID and CT 3000 brands with optimum humidity after firing at 1580 оC are characterized by low open porosity and correspond to high refractories corundum high-density products requirements (open porosity no more 0.8 %).