Study of the kinetics structure formation of cement dispersed systems. Part I

Introduction. To create concrete with a set of physical and mechanical characteristics, a rational selection of the components of the concrete mix is required, including the use of finely dispersed fillers, including those based on recyclable materials, and a highly effective chemical additive of a certain nature and reactive action, which has a complex effect on concrete system. Methods and materials. The effectiveness of the components in used additive was assessed by changing the indicators of compressive strength, tensile strength in bending, the assessment of which was carried out according to GOST 10180-2012 "Concrete. Methods for determining the strength of control samples. For carrying out scientific and experimental studies, the following materials were used: Portland cement CEM I 42.5N; natural sand; fine microsilica; complex chemical additive with increased plasticizing and reactive effects. Results. The combination of polycarboxylate polymers and nanodispersions of silicon hydroxide enhances the effectiveness of each component, which is reflected in a significant increase in the coefficient of crack resistance of concrete at high compressive strength. It has been established that when using a complex nanopolymer chemical additive, the increase in tensile strength in bending is 67% and it exceeds the increase in compressive strength by more than 30%. Discussion. An increase in hydration activity in the presence of a nanopolymer additive has a positive effect on the compaction of the emerging concrete structure. Confirmation of the formation of a dense and strong structure during the hardening of nanomodified concrete is an increase in the water resistance of concrete by 2.5 times and its frost resistance by more than 2.5 times. Conclusion. The advantage of nanomodified concrete is its increased chemical resistance to carbon dioxide and magnesia corrosion and, in accordance with the index of chemical resistance coefficient, CCSт> 0.8, and GOST R 58895-2020, the developed nanomodified concrete belongs to chemically highly resistant concretes. It is advisable to recommend nanopolymer concrete with high physical and mechanical properties for the manufacture of structures for overhead power transmission lines (OPL).

Section: Discussionmentioning

confidence: 99%

High-performance nano-modified concrete of increased strength and durability

Kasatkin¹,

Soloviova²,

Stepanova³

et al. 2022

“…The modifying additive based on zinc hydrosilicates additionally contains a small amount of Zn 4 SO 4 (OH) 6 •хH 2 O. For the nanomodification of the binder nanosized zinc hydrosilicates produced according to the technology presented in [8] were used. Modifier have sedimentation stability [9].…”

Section: Methodsmentioning

confidence: 99%

“…Early, the refinements of the methodology for determining the parameters of the kinetics structure formation of cement composites, including modified compositions, are proposed in the article [8]. The essence of the refinement is to consider the kinetics of structure formation as a time series, the development of which can be described by the dependence proposed by Hurst.…”

Section: Introductionmentioning

confidence: 99%

Study of the kinetics structure formation of cement dispersed systems. Part II

Korolev¹,

Grishina²,

Inozemtcev³

et al. 2022

Self Cite

Introduction. The study of the kinetics structure formation is rarely the subject of a careful study. Although it is important for materials used to create elements of building structures, energy elements, thermoelements and materials for other purposes. The article proposes refinements of the methodology for determining the parameters of the kinetics structure formation of cement composites, including modified compositions. Methods and materials. The structure formation of cement systems with plasticizers, microsized mineral additives (hydrosilicates of barium, copper, iron and zinc) and nanosized particles of zinc hydrosilicates has been studied. Results and discussion. It is proposed to single out two stages of initial structure formation: the stage of setting the cement paste and the stage of hardening. It was found that the strength of the material at the stage of hardening should be influenced by an additional factor, depending on the type of the introduced substance. A strong negative relationship between the parameters α and n of the equation) at the hardening stage was confirmed. The trends identified at the setting stage also demonstrated, namely: an increase in the rate of structure formation leading to the formation of a less dense structure. Conclusions. An analysis of the change in the value of the internal dimension of the system during the transition from the stage of setting to the stage of hardening made it possible to identify two trajectories of the system development. The first trajectory appears only by combining the elements of the structure (trajectory No. 1). Preservation of the characteristic dimensions of structural elements, but an increase in the proportion of elements with small dimensions (when the conditions that prevent the combination of elements of the structure are realized) describes the second trajectory (trajectory No. 2). The implementation of trajectory No. 2 is typical for compositions which the structure formation of cement stone is carried out in the presence of Melment F15G plasticizer or microsized particles of copper or zinc. For other studied compositions, structure formation is proceeding with the enlargement of structural elements.

“…The use of such additives, both mineral and chemical (synthetic) nature, is one of the tools that provides the ability to control the processes of structure formation at the recipe level. At the same time, a significant role is given to the formation of the structure of hardened cement paste at the micro level [11], because it predetermines the potential for the development of complex modifying additives that implement versatile mechanisms for controlling structure formation [12,13]. Mainly imported additives are used in the domestic construction industry.…”

Section: Introductionmentioning

confidence: 99%

“…The creation of an effective complex concrete mix modifier based on glyoxal is possible by combining glyoxal and organic compounds suitable for it according to the "retarder-accelerator" principle [18,19]. The available scientific groundwork shows the possibility of forming a denser and more durable structure of hardened cement paste in the composition of concrete due to the combined control of structure formation, which consists in the simultaneous control of both the number of crystallization centers and their growth [11,13,14]. This is realized by a combination in the composition of the modifying additive of components that perform the function of an accelerator and retarder of the hardening of the binder, respectively [19].…”

Section: Introductionmentioning

confidence: 99%

Structural and heat insulating cement based concrete with complex glyoxal based additive

Steshenko¹,

Simakova²,

Inozemtcev³

et al. 2022

Introduction. The article presents the results of studies of the effect of complex additive based on glyoxal on the properties of cement-based foam concrete mix and foam concrete of natural hardening. The relevance of the study is determined by the necessity to provide the required process parameters of mixture for transportation and laying the formwork, as well as providing strength and thermal and physical characteristics of wall structures for the development of the northern regions of Russia, including the Arctic zone. It has been proposed to decrease the shrinkage deformations of the concrete mix and increase compressive strength of hardened foam concrete by affecting the cement matrix with complex modifier based on glyoxal. Materials and methods. The effect of modifying additives on the properties of the foam concrete mixture and foam concrete was studied at a W/S mixture ratio of 0.45. Research has been carried out using test methods set out in national standards. The results of the study of the effect of complex modifying additives (CMA) based on an aqueous solution of glyoxal and organic acids on the rheological and strength properties of foam concrete are presented, the regularities of the processes and the mechanism of structure formation of the modified foam concrete are determined. Results. The use of modifying additives leads to increase result in increasing the aggregative stability and reducing the plastic shrinkage of the foam concrete mix by 22-70%. In foam concrete with the complex additive LA 0.5% + Gl 0.55% the compressive strength rises from 1.96 to 2.43 MPa at the age of 28 days while maintaining the average density of D600. The thermal conductivity coefficient of foam concrete modified with various additives decreased by 5-30% compared to references. Conclusions. The obtained results of the study create in the construction industry the basis for the import substitution of modifying additives on the domestic mineral resource base and the production of effective structural and heatinsulating concretes for the development of the northern regions of Russia.