The polymer deformability under load and heating is the determining factor in calculating reinforced polymer structures used under heating. Deformability-load/temperature relations make it possible ...to calculate temperature stresses and deformations in bearing cross-sections of polymer structures such as chimneys, smokestacks, etc. The present study suggests a method of calculating deformability of polymers subjected to the temperature loads. The method is based on the structure model of pack or layer bonded polymer domains where the elasticity of rigid bonds decreases with heating according to entropy principles. The method has been successfully tested on various polymers and compounds with due account for the effect of mineral additives on the deformation modulus increase.
The influence of four naturally occurring mineral additives (zeolite, diatomite, trass and bentonite) on the hydration and properties of cement pastes and mortars was investigated. The materials ...change the phase composition, heat of hydration (determined by calorimetry) and mechanical properties of composites. After 28 days, the amount of Ca(OH)2 was reduced by up to 23% and up to 35% more C-S-H was formed, as proved by TG measurements. Differences were observed in the kinetics of heat release, especially for 25% of the addition. In the calorimetric curves, an additional exothermic effect is observed, related to the alteration in the hydration of C3A in cement. From the point of view of beneficial influence on mechanical properties of mortars, the additives could be ranked as follows: bentonite < diatomite, zeolite < trass after 2 days and bentonite < diatomite < trass < zeolite after 28 days of curing. The highest compressive strength (58.5 MPa) was observed for the sample with a 10% addition of zeolite. Zeolite, trass, bentonite and diatomite are all pozzolanic materials; however, their activity varies to an extent due to the differences in their specific surface area and the content of the amorphous phase, responsible for the pozzolanic reaction.
Portland cement-based artificial stone is one of the most important construction materials, but the high risk of efflorescence limits its application. Metakaolin, nano-SiO2 and basalt powder were ...used as mineral additives in Portland cement stone to inhibit efflorescence in this work. The efflorescence of cement stone was investigated from perspectives of hydration products and pore structure. Both morphology and phase assemblage of efflorescence substance was studied through optical microscope, laser confocal Raman spectroscopy and SEM at various scales. Results show that the addition of nano-SiO2 and metakaolin can effectively inhibit the efflorescence of cement stone, due to the consumption of Ca(OH)2 during cement hydration and the decline in total porosity. By contrast, nano-SiO2 with higher reactivity and specific surface area exhibits the best efflorescence resistance, accompanied with the least amount of macro-pores and total porosity, the lowest capillary absorption coefficient and portlandite content.
Cement production efficiency improving Orazov, Parahat; Nurberdiev, Redzhepnur; Khodzhamuradov, Kurt
E3S Web of Conferences,
01/2023, Volume:
376
Journal Article, Conference Proceeding
Peer reviewed
Open access
The paper considers the issues of increasing the efficiency and environmental safety of cement production by using clinker dust in slurry preparation and replacing a certain part of clinker with ...mineral additives having pozzolanic activity. On the basis of research work carried out at the production site of the Baherden cement plant (Turkmenistan), the suitability of a Venturi scrubber to capture the dust generated in wet clinker kilns of cement plants has been established. The technological scheme for the use of the sludge generated in the scrubber in the preparation of clinker was developed. Based on the results of analyses of the main indicators of cement prepared with the addition of sludge the possibility of using the collected dust in the production of cement has been established. The optimal solution for three interrelated problems, such as increasing the efficiency of cement production, reducing the amount of harmful gases emitted into the atmosphere, and rational use of natural resources, is to reduce the specific consumption of clinker by compensating a certain part of it with mineral additives with pozzolanic activity.
This paper investigates the mechanical properties of sandcrete mixes with metakaolin (MK) as a mineral additive. Three different types of binders were prepared: one used as reference, based on 100% ...w/w ordinary Portland cement (PC), and two modified, where MK replaced PC in percentages 10% or 20% by weight of the reference cement content. Experimental tests have been carried out in order to obtain the full stress-strain diagram for the material under uniaxial compressive loading. The results of the tests have been post-processed numerically in order to obtain various mechanical characteristics of the sandcrete material, such as compressive strength, modulus of elasticity and strain at maximum strength. It has been found that, in general, specimens with metakaolin in the binder exhibit enhanced compressive strength compared to the reference samples without metakaolin. The improvement in compressive strength was more pronounced in samples with higher concentration of binder (50% w/w) and low or medium water per binder (W/B) ratio. Samples with higher compressive strength were characterised by higher values for the measured ultrasonic pulse velocity. The strain values, recorded at maximum strength, are considerably higher than the strain value of 2‰ for concrete under uniaxial compressive load.
the article discusses the effect of the complex of active mineral additives consisting of silica and fly ash, and a fine aggregate, including finely ground natural-white quartz sand for partial ...replacement of river sand, on the mechanical properties of high-strength concrete containing steel fiber.
high-strength concrete containing Dramix
3D 65/35 steel fiber in the amount of 100 kg per 1 m
of concrete mixture was suggested where 22% to 100% of river sand was replaced by finely ground white natural sand of the particle size of 5 to 1800 μm and containing the complex of active mineral additives for partial replacement of cement as part of a multicomponent binder, consisting of low-calcium fly ash of thermal power plants and silica and containing, respectively, 20, 30, 40% fly ash and from 5 to 15% silica by weight of the binder.
research results have shown that 100% replacement of river sand with finely ground natural white sand, in concrete containing 20% of the mass as part of a multicomponent binder, fly ash and from 5 to 15% by weight of silica, contributes to the increase of its strength properties: the values of concrete compressive strength after 28 days were in the range from 118.5 to 128 MPa, tensile strength during bending and splitting, respectively, from 18.8 to 25.4 MPa and from 10.2 to 11.9 MPa, which is higher than the strength of concrete samples containing river sand.
the achieved results have demonstrated the efficiency of using finely ground natural white sand as an alternative to river sand for producing high-strength concrete, thus helping to save the river sand resources in Vietnam. The use of fly ash and micro silicon, which are power and metallurgy wastes, as part of a multicomponent binder in order to partially replace cement reduces the carbon footprint in the production of binders and will also have a beneficial effect on environmental protection against industrial waste pollution.
There is an increasing tendency to use recycled aggregate to produce concrete due to diminishing sources of natural aggregate. The properties of recycled aggregate concrete (RAC) are inferior to that ...of normal aggregate concrete. Several strategies including the use of supplementary cementitious materials (SCMs) are adopted to improve the properties of RAC. The two-stage mixing approach (TSMA) is also used as an improvement strategy. The present study was aimed to examine the individual and combined effects of using SCMs and TSMA on the fresh and hardened properties of RAC. Three SCMs, namely, fly ash, ground granulated blast furnace slag, and silica fume were used with and without TSMA. The experimental data indicated the beneficial effect of SCMs and TSMA on workability, strength, shrinkage, and durability of RAC. Further, the cost per unit strength of the RAC with SCMs and TSMA was less than that of RAC without any treatment. The use of developed RAC will lead to technical, economic, and environmental benefits.
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