Papers by Keyword: Binder

Abstract: Green sand mixtures which are used for moulding purposes in foundry industries should possess sufficient green compression strength, flowability, toughness and air-permeability. Usually, the aforementioned properties for a particular casting differ due to variation in composition of the moulding sand mixtures, sand grain shape and size, bonding capacity of the binder, type and quantity of additives used, etc. The present work focuses on the effect of various additives namely, camphor powder, coconut shell ash, mixture of camphor powder and coconut shell ash at diverse proportions on permeability and green compression strength of the sand moulds. The quantity of the aforementioned additives for experimentation was varied from 0.5 to 3.5 wt. %. It was found that the mould’s permeability increased on addition of 1 wt. % additives for all cases. Similarly, the optimum quantity of additives that needs to be added to the sand mixtures for enhancing green compression strength was found to be 2 wt. %. Among all the additives used for improving the mould’s permeability, substitution of camphor exhibited best results. The green compression strength was found to be highest for the coconut shell ash containing sand mould. The moulding sand containing a combination of camphor powder and coconut shell ash between 1 to 2 wt. % exhibited fine mould permeability along with sufficient green strength.

Abstract: Geopolymer are being considered for a variety of application including formation of ceramics. The addition of Ultra High Molecular Weight Polyethylene as binder in geopolymer based ceramic is purposely to enhance the strength and toughness of the ceramic materials. This paper aims to study the relation of density and flexural strength of geopolymer based ceramic with addition of Ultra High Molecular Weight Polyethylene as binder. Geopolymer were synthesized by fixing the NaOH molarity, Na₂SiO₃/NaOH and solid to liquid ratio at 12 M, 0.24 and 1.0 respectively. Geopolymer in a powder form with addition of various content of UHMWPE (2 wt.%, 4 wt.%, 6 wt.%, 8 wt.% ) were pressed into pellets followed by sintering at 1200 °C. The highest flexural strength of geopolymer based ceramics was achieved at sintering temperature of 1200 °C which is 92.1 MPa with a lowest density of 1.88 g/cm³.

Abstract: Climatic and traffic effects are the causes of aging of the surface layer of asphalt, which leads to the necessary renovation of the latter. The use of waste from the tread layer provides a viable and beneficial solution for the environment and the economy. However, this solution must meet the requirement of sustainable development, which necessitates that a road has a very long lifespan. In this study we investigated the performance of recycled asphalt in terms of fatigue (as an element of life-cycle control). All the formulas were tested by the fatigue test in order to define the influence of the proportions of the asphalt aggregates, penetrability of the new binder used, and the manufacturing temperature. The results obtained showed the relationship between the contribution binder (reproduced between the new binder and the old binder) and the fatigue resistance under the influence of the parameters that we have mentioned above. At the end an optimization study has been carried out in order to determine exactly the doses required to formulate recycled asphalt resisted to fatigue The optimization seeks to maximize the asphalt aggregates and minimize the temperature of manufacture with a class of the binder compatible.

Abstract: Currently, dry mixes (CDM) play an important role in the development of the world market of building materials. The industry of construction and finishing materials in Russia is quite young: the first time the dry building mixes appeared on the Russian market in the late 1980s, the consumption structure of CDM in the domestic market the main share (70%) are in the adhesive and plasters. The use of other compositions, in particular mixtures for self – leveling floors, does not have significant volumes and often the reason for this is the lack of design solutions and the low level of qualification of specialists at different levels from workers to designers who do not own CDM technologies.

Abstract: This study deals with the restoration of columns of the VEF Culture Palace. A complete restoration of the building was performed in 2016–2017 [1]. The methodology of physico-chemical investigation of the stone materials of two facade columns includes visual observation, granulometric analyses, classic wet chemical analyses, XRD and determination of soluble salts’ content. The data obtained indicate, that for rendering of columns dolomitic and calcitic lime mortars were used. An efflorescence of sulphates on the bricks’ surface is observed.

Abstract: A proper recycling and secondary reuse of end-of-life car tires (ELTs) remain an important issue for many regions. Devulcanised crumb rubber as a product of ELT recycling could be used for very different applications, including site remediation by spilled oil products. In current paper a development of new bio-based composite material containing devulcanised crumb rubber and cenospheres is suggested. Designed bio-based composite can be used as a oil spill adsorbent, material for civil engineering, and as a raw material for further modification by introduction of ferromagnetic components. Homogenised peat with peat content 14.0 ± 1.5 wt%, particle size 0.01 – 0.5 mm used as a natural bio-based binder. Devulcanised crumb rubber particle size 1.0 – 4.0 mm was used as a porous substrate. Designed compositions contained 5, 10, 15, 20 wt% (before drying) of devulcanised crumb rubber. Cenospheres have duplex function for designed composite: lightweight additive that makes final product floatable, and at the same time minimises shrinkage of dried product. It was found that devulcanised crumb rubber reduces density of final composite and adding open porosity. Developed bio-based composites could be manufactured in granules by drum granulation technique for further environmental applications. Formability and apparent density of bio-based composite are studied.

Abstract: The rheology of A96% alumina slips and the physical and mechanical properties of slip cast samples were studied. The slips had a constant solids loading of 40 wt% alumina and a polyvinyl alcohol (PVA) content of 0-3 wt%, as a binder. The rheological behavior and viscosity of the slips were examined to determine the flowability of the slips necessary for the casting process. The slips were prepared by ball milling and the bend bar samples were cast in plaster molds. The green densities and the flexural strength of the bars were measured, and the fracture surfaces were examined by scanning electron microscopy. It was found that the slip viscosity increased with an increase of PVA content. The green flexural strength also increased to a maximum value of 0.52 MPa with increasing PVA up to 2 wt%. The further addition of PVA decreased the flexural strength. The green density did not significantly change with the PVA content, however the samples produced using 3 wt% PVA showed the lowest percentage of theoretical density of 41%. The fracture surface of the 3 wt% PVA sample showed numerous large pores compared with the other samples. Therefore, in this study it was concluded that there is in optimal amount of PVA to produce the highest green density and flexural strength of cast samples. Excess PVA reduced the flowability of the slip and resulted in excess porosity, which decreased the green density and deteriorated the flexural strength.

Abstract: The goal of this work concerns the synthesis of a binder for restoration purposes that is physically and chemically compatible with dolomitic Roman cement, a historical binder used for the construction of significant architectural heritage objects in the 19^th and 20^th centuries. Dolomitic marlstone, the traditional raw material of dolomitic Roman cement, is not being obtained anymore and it is also hard to achieve a constant chemical composition. To address these issues, the experimental synthesis of a low temperature hydraulic binder using locally sourced raw materials, namely dolomite flour and clay, was performed. The developed synthesis technology provides economic and ecological advantages compared to other similar materials, such as lime with pozzolan additive, lime and cement mixtures and magnesium oxychloride cements. The raw material, dolomite flour, is a by–product in the manufacturing process; furthermore, the low firing temperature (800 °C) reduces the power consumption required to obtain the binder.The aim of the work is determination of porosity-related physical characteristics of dolomitic binder that is synthesized by using manufacturing by-product – dolomite flour – as basic raw material to evaluate it’s suitability for restoration purposes.

Abstract: As a result of the research, the technology of accelerated forming on the sol-silicate binder in precision casting has been developed. It is based on granular materials cladding by the gel-processing catalysts of the sol-silicate binder and on the use of the clad granular materials as the stucco of ceramic coating layers. That allows to achieve a reduction of ceramic molds product cycle of more than 2...2.5 times and strength improvement of 1.4...1.5 times at the temperature of baking. The developed technology allows to improve the quality of ceramic molds and significantly shorten the forming cycle. Production tests of the gel-processing clad stucco in the investment casting showed a significant reduction of the reject precision castings, acceleration of ceramic molds production and a reduction of the working hours on removing "wedged" ceramic from less-accessible cast section cavities of the pump parts from complex alloyed steels.

Abstract: The article considers a method of recycling citrogypsum – the сіtric acid production waste. A modified gypsum binder was obtained by means of dehydration of citrogypsum suspension and adding a modifier - polyacrylamide (PAA) - to it in conditions of autoclave treatment. The application of PAA as a modifying admixture causes the necessity to reduce the water-gypsum ratio (W/G) of the mix in order to prevent lamination at the molding product forming; at the same time, to provide the necessary flowability of the mix the introduction of plasticizing admixtures is needed, or the application of the harsher moulding mixtures or pressing technologies. For cylindrical samples, obtained by the compaction method at W/G=0.25 and the specific compacting pressure 20МPа, the optimal content of polyacrylamide as a modifying admixture amounts to 2% of the initial citrogypsum weight. This allows increasing the compression strength of the ready samples by more than 5 times. The samples, produced on the basis of modified gypsum binders, are characterized with high water resistance – the softening coefficient amounted to over 0.8.