strength

The article describes the development of rapid-hardening, high-strength fiber-reinforced concrete with increased impact resistance for protective structures. Fiber-reinforced concretes with the addition of Portland cement CEM II/A-LL 42.5 R (C = 390 kg/m3) with polymer structural fiber PMS 1/60 with the addition of PCE were studied. The addition of PMS 1/60 fiber to concrete increases impact strength by 2.8-3.7 times and achieves a strength class of C 40/50. Fiber-reinforced concretes with the addition of Portland cement CEM II/A-S 52.5 R were studied.

The article examines the problem of strengthening reinforced concrete floor slabs with insufficient load-bearing capacity during reconstruction or increased loads. A method is proposed involving partial integration of additional monolithic reinforced concrete beams through pre-formed openings in the slab. Various approaches are analyzed to ensure composite action between the slab and beams. The study aims to theoretically and experimentally determine slab deflection and develop optimal implementation methods.

The paper substantiates the selection of a polymer and filler based on aromatic polyamide to create a material of friction pairs that operate in heavy-duty friction and sealing units of up-to-date vehicles and machinery. The effect of load and sliding speed on the tribological behavior of the initial aromatic polyamide and filled 15%-aramid fiber was studied. As a result of tribological studies, the terminal operating conditions of products made of initial aromatic polyamide and a composite based thereon, filled with aramid fiber, have been determined.

A study on the influence of polycarboxylate-type superplasticizers on the physical and technical properties of fine-grained concrete was conducted. The proposed concept involves creating high-quality, high-strength concretes based on modified cementing systems characterized by improved construction and technical properties.

The production of shredding shafts for industrial shredders presents significant challenges due to the high mechanical loads and exposure to abrasive materials these components must endure. Traditional designs involve the complex and labour-intensive process of welding sprockets to the main shaft, which increases manufacturing, labour, and maintenance costs. This study explores a novel approach to manufacturing shredding shafts by implementing cast sprockets, significantly reducing the complexity and expense associated with traditional designs.

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.