English English

Keywords: concrete

Investigation of plasticizing additives based on polycarboxylate esters on the properties of concretes formed by 3D printing

https://doi.org/10.58224/2618-7183-2022-5-5-42-58
 42-58 p.
Abstract
The article studies the features of the use of plasticizing additives based on polycarboxylate ether in the technology of additive construction production (3D printing). Layer-by-layer extrusion was carried out on an AMT S-6044 3D printer. The normal density and setting time of the cement paste, the average density, plastic strength and dimensional stability of the concrete mixture, the compressive strength and flexural strength of concrete were studied. It is shown that plasticizing additives based on polycarboxylate esters in the considered concentrations are effective modifiers of rheotechnological and physical and mechanical properties of cement concrete mixtures used in 3D printing technology. The greatest increase in compressive and flexural strength with the introduction of the studied polycarboxylate plasticizers is observed at PC CEM I 42.5N: the introduction of 0.5% "MasterGlenium 430" leads to an increase in compressive and flexural strength by 49.3% and 31.6%; with the introduction of "MasterGlenium 115" – by 21.6% and 35%; with the introduction of "MasterGlenium 591" – by 49.8% and 41.7%, respectively. Of interest for further research is the development of complex organo-mineral additives of multifunctional action based on polycarboxylate plasticizers for concretes molded by additive manufacturing (3D printing).
PDF

OBTAINING A THERMAL INSULATION LAYER FROM MONOLITHIC NON-AUTOCLAVED STRUCTURAL AND THERMAL INSULATION FIBRE FOAM CONCRETE

https://doi.org/10.34031/2618-7183-2021-4-3-5-22
,
 5-22 p.
Abstract
The possibility of obtaining structural and thermal insulation foam concrete of non-autoclave hardening with improved construction and technical characteristics for the device of a thermal insulation layer in the con-struction of road pavement due to three-dimensional dispersed reinforcement with polypropylene fiber is theoretically justified and experimentally confirmed. Based on the results of studies of the influence of technological factors on the properties of foam concrete, the optimal content (up to 0.25% of the cement mass) and the length (12 mm) of reinforcing polypropylene fibers have been established, which allows obtaining high strength indicators of dispersed-reinforced cement stone for bending (an increase of 12-20%) and compression (an increase of 6-12%) compared with non-reinforced cement stone of non-autoclaved foam concrete. The analysis of the process of structure formation of dispersed reinforced foam concrete from the standpoint of a systematic approach based on multifactorial polynomial models of the influence of the ratio of filler and binder, as well as the number of dispersed reinforcing fibers, which is determined by the optimal conditions for the distribution of solid and gas phases, as well as the reinforcement of adjacent interstitial partitions of foam concrete, linking them into one asociate, which ensures the joint work of the material under various external influences. A method was developed to increase the durability of the road surface and eliminate the influence of the frost heaving effect on the quality of the road surface by introducing the necessary amount of effective thermal insulation layer into the road surface design. The analysis of the regularity of the heat transfer process in the soil mass of the roadbed and multilayer road pavement is carried out. Based on the analysis, the values of the necessary resistance to heat transfer of road pavement for the natural and climatic regions of the country are determined and a method for calculating the value of the thermal insulation (frost-proof) layer of road pavement is proposed. A method was developed for calculating the value of the thermal insulation layer using monolithic fibre foam concrete and a nomogram to determine the required value of the thermal insulation layer made of monolithic non-autoclaved structural and thermal insulation fibre foam concrete of classes D600-D1000.
PDF

USE OF IRAQ CONCRETE SCRAP AS FILLER AND AGGREGATE OF HEAVYWEIGHT AND LIGHTWEIGHT CONCRETE

https://doi.org/10.34031/2618-7183-2020-3-3-28-39
, , , ,
 28-39 p.
Abstract
The relevance of the paper is due to the search for alternative sources of raw materials for the construction industry, associated with the disposal of man-made waste. The novelty of the article is to identify the sci-entific laws of the influence of demolition waste on buildings and structures on the formation of the microstructure of lightweight and heavyweight concrete. Concrete waste was prepared as both fillers of cement materials and fine aggregates, based on which concrete with high mechanical properties was created. The mix design was carried out from the point of view of geomimetics, in particular, taking into account the law of affinity of structures. The strength characteristics of concrete mixtures were investigated in accordance with EN 12390-3. In addition, the microstructural, morphological and thermal properties of the raw materials and concrete were determined during 28-day curing. For the first time, the dense microstructure of the composite was ensured, both with Portland cement products and with hydration, and, in part, with hydration products of previously unreacted clinker, whose minerals are present in concrete waste and are activated when they are crushed. The use of demolition waste of buildings and structures as a filler of cementing material when replacing Portland cement up to 20% allows to obtain better compressive strength of both heavyweight and lightweight concrete.
PDF