Papers by Keyword: Portland Cement

Abstract: The article examines the physical-chemical features of the formation of the garnish on the lining of rotary kilns for firing cement clinker, the functional necessity of the garnish and the material science difficulties for its creation when developing new types of refractories, which solves the problem of the formation of Cr(VI) compounds in Portland cement. Thus, the analyzed problem of the formation of Cr(VI) compounds in Portland cements that are dangerous for the biocenosis and humans is the result of scientific and technological progress, the pursuit of leading manufacturers for the recycling of secondary raw materials and energy resources. At the same time, the timeliness of identifying the problem and its proactive, comprehensive solution with state support give a new impetus to the scientific and technical development of not only cement, but also related enterprises and scientific organizations. In Ukraine, the problem has been solved only in relation to the development and experimental testing of a new type of refractory material to replace magnesia-chromite for lining high-temperature zones of rotary kilns for firing cement clinker.

Abstract: Several techniques based on ultrasound have been proposed for non-destructive evaluation (NDE). It has been widely applied in many fields such as medicine, mechanical, and construction, especially for the detection of cracks and flaws in structures and for the identification of material properties, which is capable of performing tasks to provide quick measurements while guaranteeing great accuracy. In this paper, we have developed the technique of ultrasonic transmission by water immersion as an alternative technique to study the propagation of ultrasonic waves in two structural materials: wood and wood protected by liquid paint (cement). Overall, the application of the transmission technique by change of the angle of incidence enables the demonstration of the experimental dispersion curves for the ultrasonic modes within the plates and allows the investigation and characterization of the function of the paint system (cement) in the wood plate.

Abstract: Geopolymer is an innovative cement substitute constructed of alkali-activated cementitious materials (AACMs). Researchers interested in improving concrete's structural resistance, toughness, and flexure tensile strength have turned their focus to geo-polymer concrete binders. To completely understand how geopolymer binders act under these circumstances, it is necessary to investigate their behavior when exposed to multiaxial stress states. The purpose of this review is to examine geopolymer cement in depth and to get a better understanding of its mechanical characteristics. In this analysis, we see that Geopolymer concrete, in particular its compressive and tensile strengths, provides higher resilience. GPC is an eco-friendly material since it reduces emissions and requires less water for curing. Incorporating hybrid polypropylene and steel fibers to ternary mixed geopolymer concrete improves its mechanical qualities.

Abstract: The possibility of increasing the basic properties of concrete products by using Portland cement with additions of sulfated clinkers as a binder is considered. It was found that when the binder is hydrated, aluminate and ferruginous ettringite are formed, which reinforce the hardening structure of the stone, increase its strength properties and resistance to the corrosive effect of sulfates.

Abstract: The main objective of the study was to obtain an effective component composition of a dry building mixture with the use of a complex additive. In this work the specific surface area of the anhydrite binder was determined. It is optimal for providing the mixtures with the required characteristics. The manufacture of experimental compositions was made, according to pre-selected recipes. From them through the performed tests, the most effective was identified. The composition of the modified anhydrite binder was established. It had to match the reference requirements for filling mixtures. The conclusion was formulated about the ability of additives to influence the technological and physical-mechanical properties of the filling mixtures.

Abstract: The durability of cement-containing building materials, like the cement stone itself, depends on their moisture resistance, frost resistance, and corrosion resistance. All these properties are determined not only by the composition of the initial clinker, but also by the structural organization at the micro-and nanoscale of hydrated Portland cement. In this work, the structural parameters of hydrated Portland cement compositions at the nanoscale level were determined by the method of small-angle neutron scattering: the size distribution of nanoparticles of calcium silicate hydrate, the average radius of nanoparticles, and fractal dimension. It is shown that the introduction of modifying nanoadditives into Portland cement affects the structural parameters of the cement stone. The following nanoadditives were used: of artificial (alpha aluminium oxide, gamma aluminum oxide) and of technogenic (carbonate and alumo-alkaline sludges) origin, as well as complex nanoadditives containing surfactants. Changes in structural parameters of Portland cement with nanoadditives in the process of hydration are traced. It is shown that the use of nanoadditives makes it possible to control the process of formation of the structure of hydrated Portland cement on the nanoscale level, to directly influence the values of structural parameters and, ultimately, to the properties of cement stone.

Abstract: Reinforced Portland cement mortars were manufactured using a mixture of type I cement, fine sand, Ichu (in variable percentages) and water, it was possible to verify the influence of the addition of Ichu fibers on the mechanical response in uniaxial compression of the mortars studied. The mechanical results found revealed a systematic reduction of the maximum mechanical resistance by increasing the volume of Ichu fibers added in the studied mortar mixtures, on the other hand, a greater degree of deformation was evidenced in mortar mixtures with a greater quantity of Ichu fibers added, reaching deformation values of up to 10%. The maximum resistance values found were 0.4 to 3.6 MPa for samples with 16 and 4 Vol.% Of Ichu added, respectively. The microstructure of the mortars studied consisted of a continuous cement binder phase with sand particles and short Ichu fibers dispersed within the binder phase. The real density and average porosity of the mortars reinforced with Ichu was 2.59 g / cm3 and 41%, respectively.

Abstract: The paper presents the study of morphological characteristics of cement particles and reveals the influence of the structure of the cement grain composition on the physical and mechanical properties of cement. The following portland cements produced by “Hrazdan Cement Corporation” LLC, which have 52,5 MPa and 42,5 MPa compressive strength limit and hydraulic additives up to 20% and over 20% have been used for the experiment: CEM II/ A-P 42,5N, CEM II/ B-P 42,5N, CEM II/A-Q 42,5N, CEM II/B-Q, CEM II/A-L 42,5N, CEM II/B-L 42,5N, CEM II/A-M 42,5N, CEM II/B-M, CEM III/A-S 42,5N and CEM III/B-S 42,5N. Grain distribution in all the samples has been studied using a CILAS laser analyzer. Microscopic analysis of all the fractions has been carried out with the help of James Swift optical microscope. The given grain compositions have undergone chemical analysis in compliance with the requirements of interstate ISO 5382-2019 and ASTM C114-18 standards. Experimental studies and analyses show that the cements with microsilica have the highest value of water-cement ratio-W/C = 0.7, the highest by volume compression are the cements with volcanic slag-4 mm, the beginning of the bonding period is the longest in case of limestone cements - t = 140 minutes, followed by microsilica cements, and in third place there are artificial slag cements, the results of which are as follows: 130; 124 minutes. The summarized data show that microsilica cements have the highest compressive strength limit among the cements having the same percentage of additives-48.87 MPa.

Abstract: Cement grouts have many purposes in various civil engineering applications such as precast construction, soil stabilization and structural rehabilitation. Using filler materials as a component in cement grouts has been increasingly implemented. The incorporation of such fillers not only does improve the fresh and hardened properties of grouts but also contributes to the decarbonization of grouts by reducing the amount of Portland cement, thereby lowering the carbon footprint of grouting materials. This study aims at assessing the influence of various filler materials on the properties of cement grouts. Three different fillers were used in this study: commercial limestone, commercial pure dolomite, dolomitic quarry dust. These fillers were assessed in terms of their effect on the spread, flowability, cohesion and compressive strength at 3, 7 and 28 days. The results show that fresh properties of the grout were dependent on the type of fillers. Dolomitic quarry dust improved the workability and flowability more than the commercial limestone and dolomite did. The compressive strengths of cement grouts did not change significantly with the incorporation of the fillers. However, cement grout samples including quarry dust exhibited slightly higher 28-d compressive strength than other samples although the same mix had lower 1-d compressive strength than other mixes. This study highlights the benefits of utilizing quarry dust in cement-based binders without compromising the performance.

Abstract: The research results on the development of fire-retardant composite cement mortar mixtures on exfoliated vermiculite and volcanic ash with the use of a multifunctional additive are presented D-5. Compositions of fire-retardant composite mortars, which make it possible to significantly improve the physical and mechanical properties of mortar mixtures and mortars, are proposed. Introduction of a multifunctional supplement D-5 in mortar mixtures makes it possible to improve the composite mortar mixtures properties and improve the solution characteristics. Replacement of finely dispersed fraction of exfoliated vermiculite d<0,63 mm volcanic ash by volume in mortar mixtures does not cause a noticeable increase in the solution density, while their strength characteristics increase. The developed composite mortar mixtures meet the requirements of GOST 28013–98 and have a low-cost price due to volcanic ash use.