strength

One of the main problems of hardening monolithic cement concrete, especially in the conditions of restoration and reconstruction of various objects, is the hardening of concrete in conditions of negative temperatures. Winter concreting technologies are divided into two main methods: the thermos method, in which the temperature of the environment in which the concrete hardens, must be above zero degrees Celsius, or the use of antifreeze additives.

This study delves into the comprehensive examination of an overhead crane's construction, focusing on its frame, columns, and beams, while considering factors such as strength, stability, and stiffness. Through an in-depth review in the design domain, it is proposed a specific structural configuration for the overhead crane. This design comprises six vertical columns supporting two longitudinal beams equipped with tracks for the trolley's longitudinal movement. Additionally, cross beams featuring winches are mounted on the trolley's cross beams.

Among the several kinds of thermoplastic adhesives, structured and non-structured polyvinyl acetate (PVA) adhesives have a rather wide application and are used currently for forming adhesive joints from different wood species, especially oakwood. To ensure proper conditions of oakwood adhesive joints use, it is important to have fast and accurate methods of predicting their strength and durability. The strength changes of the oakwood adhesive joints bonded with structured and non-structured PVA adhesives have been investigated by conducting long-term experiments.

An important task is to improve cutting tools for high-precision productive machining of difficult-to-machine materials by applying the latest tool hardening methods. This is especially true for carbide-cutting tools. The paper analyzes the current state of the problem of improving the tooling of new machine tools for high-precision productive machining of hard-to-machine materials.

The article presents the results of research on modified steel fiber-reinforced concrete and shows the expediency of their use to increase the effectiveness of fortification protection structures against shock loads. It was established that according to the results of tests of compressive strength (fсm = 79.4 MPa) and tensile strength during bending (fс, lf = 7.4 MPa), steel fiber-reinforced concrete can be classified as high-strength (strength class C 50/60) and rapid-hardening (fcm2/ fcm28 = 0.57) in accordance with DSTU EN 206:2018.

Goal of the work is to develop a methodology for researching the possibility of further exploitation of drums of boiler units of thermal power plants after exhausting their park resource. Significance.

The key system of equations of the solid body model is presented, taking into account the structural heterogeneity of the material and the roughness of the real surface, which is applied to the study of interconnected fields in an unbounded heterogeneous conductive layer.  The effect of taking into account the dependences on the density of local Young's modulus and Poisson's ratio on the size effects of surface stresses in the layer and its strength limit is considered.

The development of high-performance materials, which are characterized by high compressive and flexural strength, durability and performance properties, is an urgent problem of modern construction. Engineered cementitious composites are one such material. Improving of properties of composites is achieved by partial replacement of cement with supplementary cementitious materials. The ratio of binder and filler components and superplasticizer consumption were selected.

This paper presents the findings of research study on the effect of borosilicate glass wastes on properties of cement paste and mortar. The borosilicate glass contains three times less alkali than soda-lime glass and about 12 % of boron oxide, so pozzolanic activity of borosilicate glass is three times higher compared to soda-lime glass. In order to increase the pozzolanic activity of glass precipitated synthetic silica was used. Mathematical models were used in order to test the effect of synthetic silica on pozzolanic activity of borosilicate glass.