compressive strength

The use of rubber crumb from used tires in concrete as a partial replacement of natural aggregates is an ecologically oriented direction of their utilization. When rubber crumb was added to Portland cement, a decrease in strength was observed. Modification of rubber-containing Portland cement systems with a complex organic and mineral additive makes it possible to compensate for the loss of compressive strength and provide increased impact strength. Samples without rubber show high strength but are characterized by fragility and sudden destruction of the material.

Dry mix mortars are widely used in construction projects for the implementation of construction works in new construction, reconstruction, and repair. The improvement of properties of dry mix mortars for the installation of floor screeds is relevant. The purpose of such mortars is to equalize the differences in the thickness of the floor surface, to create an intermediate layer characterized by the necessary strength, durability, and even surface with the possibility of decoration with various types of flooring.

In the post-war period, Ukraine will need a large number of aggregates to repair and rebuild destroyed and damaged objects of transport infrastructure, including roads, airfields, and parking lots. To expand the raw material base of such construction, in addition to traditional high-quality aggregates from crushed granite, quartz sand and manufactured sand, it is advisable to use some types of waste and secondary products from various industries. They must meet the basic requirements for density, strength, frost resistance. These include a by-product of iron ore mining, quartzite.

The influence of the air-entraining agent (AEA) on a density, the volume of entrained air of mortar mix and compressive strength of hardened mortar was studied in this article. Results show that the addition of AEA results in the reduction of water to cement ratio to provide the targeted flow and the density that depends on the volume of entrained air. The addition of AEA causes the decrease of the density of mortar (C:S=1:2) by 8,2% and the increase of the compressive strength by 13,9% after 28 days of hardening compared to the mortar (C:S=1:2) without AEA.

The article analyzes the experience of using Portland limestone cement for the production of ready-mixed concretes. It is shown that polycarboxylate superplasticizers (PCE) play a decisive role in providing required technological and construction-technical properties of concrete. The data show that the most effective PCEs for maintaining the workability of the concrete mixture over time and obtaining the required strength class of concrete are РСЕ based on modified acrylic polymers.

This article proves the possibility of replacing aggregates in concrete mixtures with rubber, which is obtained by grinding used car tires. It was found that the replacement of crushed coarse aggregate in the amount of 10 vol.% with ground rubber from used car tires increases the bending strength by 23% The compressive strength does not change significantly.

The article considers the possibility of using wastepaper sludge ash (WSA) as a soil reinforcement material for the construction of layers of road wear. Loamy sand, sandy loam, silty clay loam, silty clay were chosen as soils for strengthening. The maximum density of the soil skeleton at optimum humidity was established by the method of Proctor. Wastepaper sludge ash and Portland cement grade 400 were used separately for soil strengthening.

The properties of fine-grained asphalt concrete and its modified by bio based epoxy rape oil (BERO) form were studied. Rapeseed oil epoxide (ROE) obtained from renewable and ecological raw materials, rapeseed oil in a composition with initiators (hardeners) was used as a modifier. It was found that the introduction of BERO in the amount of 3% of the mass. allows to increase indicators of limit of durability of asphalt concrete at compression at a temperature of 20 ° C and 50 ° C.

Particulate composite was prepared from a mixture of cement, gravel and water with additions of a polyepoxide and/or expanded polystyrene in powder. For consolidation, each mixture was poured into a mold, remaining for a short period and then removed. For complete solidification the specimens were cured with water during the final stage. The weight, compressive strength and thermal conductivity of the composite were determined.

This paper presents the investigations of the environmental advantages of low carbon composite gypsum binders for building applications. The impact of ultrafine zeolite additive on the physico-mechanical properties and hydration processes of composite gypsum binders has been investigated. The modification of gypsum pastes by polycarboxylate type superplasticizer results in the radical change in the formed microstructure of composite gypsum binders. The obtained results are essential for further design and development of new types of gypsum composites with an increased water resistance.