Microsilica Addition Research Articles

Properties of CaO-MgO-SiO2 insulating refractories prepared from phosphorus tailings

CaO-MgO-SiO2 insulating refractories were prepared using phosphorus tailings through in-situ pore-forming technology in this work, aiming to achieve the efficient utilization of solid waste phosphorus tailings. microsilica was used to react with free CaO generated by the decomposition of dolomite from phosphorus tailings during the calcination in order to prevent the hydration of CaO in the materials. The influence of microsilica addition and heating temperature on the properties of insulating refractories prepared from phosphorus tailings was investigated. The results showed that CaO-MgO-SiO2 insulating refractories with 8.8 wt% microsilica addition exhibited excellent comprehensive performance after heating at 1300 °C for 3 h. The insulation refractories prepared from phosphorus tailings were anti-hydration, had lower thermal conductivity, and could be used as insulation refractories for high-temperature kilns.

Influence of Mineral Additives on Strength Properties of Standard Mortar.

In the article, the authors presented the results of research on the assessment of the effect of selected mineral additives on the strength properties of the standard mortar. The modification of the composition of the standard mortar made on the basis of CEM I 42.5R cement and quartz sand consisted of using seven selected mineral additives in the form of compacted microsilica, Mikrosill microsilica, limestone flour, glass flour, glass granulate, basalt flour, and fly ash in the amounts of 10 and 20% in relation to cement as its substitute. Reducing the share of cement in the standard mortar by 10% has a beneficial effect on improving the compressive strength by over 40% with the addition of microsilica, and in the case of bending strength, even by 10%.

QUALITY IMPROVEMENT EFFECTIVENESS OF ROAD SLABS PRODUCED USING MICROSILICA AND FIBER

Here we present the results of testing the concrete physical and mechanical properties for road slabs reinforced with bulk fiber, including polypropylene macro- and microfibers. We have analyzed the effect of the use of macrofibers and microfibers in the concrete composition. There was established the impact of low-modulus synthetic fibers on the characteristics of strength, density, water resistance and frost resistance of concrete for road pavement. It was established that polypropylene macrofibers impact on the physical and technical characteristics of concrete, increase compressive and bending strength, and polypropylene microfibers improve the structure of the cement component of concrete, optimize the pore space, increase the frost resistance and water resistance of concrete. It has been experimentally proved that owing to the combined use of various sized fiber fibers, it is possible to produce concrete that has good characteristics in strength, density and frost resistance. It was established that with the combined concrete fiber reinforcement with microsilica addition, we get the possibility of increasing bending strength up to 35%, frost resistance up to F375 and water resistance up to W14. The research results make it possible to recommend multi-dimensional polypropylene fibers for volumetric reinforcement and microsilica to create additional crystallization centers and reduce the pore space in the concrete body at road slabs manufacture.

EXTRA FINE-GRAINED CONCRETE FROM WASTE OF MINING CONCENTRATION PLANT FOR CONSTRUCTION PRODUCTS

The theoretical substantiation of the production of especially fine-grained concrete (EFC) from the waste of the Poltava Mining Concentration Plant as a fine-grained aggregate has been performed. Its structure is substantiated taking into account the contacts between the angular aggregate grains, the possibility of increasing strength by introducing mineral fillers and microfillers with particles 5 times smaller than the aggregate grains and cement particles, respectively, is proved. The determination of the composition of EFC from the waste of the Poltava MCP was substantiated by determining and ensuring the optimal value of the coefficient of displacement of aggregate grains by cement paste m opt = 1.89 with the inclusion of dusty fractions of the aggregate. The optimal composition of EFC Aggregate : Cement : Water = (3–3.15):1:0.5 with mandatory use of superplasticizer additive to ensure W/C = 0.5 was determined and experimentally confirmed. The dependences of compressive and tensile strength of EFC on: type and content of superplasticizer additives were experimentally investigated; ratio of aggregate content to cement content; microsilica content; pressing pressure. It was established that the maximum strength of EFC is achieved in the case of the use of superplasticizers: polycarboxylate 1.5 % or sulfonaphthalinformaldehyde 1 % by weight of cement. It was also established that with the same A:C = 3:1 and W/C = 0.5, the strength of EFC on the waste of Poltava MCP exceeds the strength of fine-grained concrete on natural, especially fine-grained sand: in compression - by 2 times, in tension - by 1.9 times and reaches 35 MPa at the age of 28 days. The addition of microsilica in the amount of up to 15 % of the mass of cement allows to further increase the compressive strength by 44 %, and the tensile strength by 20 %. It is proposed to form EFC products by layer-by-layer pressing with a layer thickness of 5 mm. It was experimentally established that the maximum strength is achieved at a pressing pressure of 12 MPa.

Synergetic effect of binary, ternary and quaternary binders on microstructural, mechanical and durability aspects of EAF aggregate HPC system

The present study focuses on the combined effects of binder composites on the microstructural, mechanical, and durability characteristics of high-performance concrete that include manufactured sand (M-sand) and Electrical Arc Furnace slag (EAF) aggregate. Also, the influence of multi binders like Ordinary Portland Cement (OPC), Ground Granulated Blast Furnace Slag (GGBS), mS (micro-silica) and nano-silica (nS) have been investigated. The ternary binder system is used to develop HPC mixtures with the effect of the mS in three levels 5%, 10%, and 15% and a quaternary binder system with 1% nS into the optimized ternary system containing 10% mS. Micro-characterization has revealed that the addition of micro-silica (mS) and nano-silica (nS) refined the compact morphology of the multi binder system. Natural aggregate is replaced at the level of 0%, 50%, and 100% with the EAF aggregate. Slump flow value decreased with an increase in micro and nano particles. Mechanical properties of HPC mixes with EAF, as well as a ternary binder without ns and quaternary binder with ns have shown better strength properties due to the combined effect of mS and nS as well as the stronger physical features of EAF slag aggregate. The qualitative tests have shown that the addition of a quaternary binder system has a significant positive effect on the permeable characteristics of HPC mixes. Deterioration due to MgSO4 solution and HCl acid is reduced due to the addition of ternary and quaternary binder composite. The drying shrinkage of HPC mixes was higher with the inclusion of micro and nanoparticles, but the same decreased with the addition of EAF aggregate. The present finding has revealed that the maximum utilization of EAF aggregate and M-Sand enhanced the durability of concrete.

Effect of microsilica addition on properties of geopolymer composites

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Changes in the Rheological and Adhesive Properties of Epoxy Resin Used in the Technology of Reinforcement of Structural Elements with CFRP Tapes

Nowadays, FRP composites are widely applied in the construction industry. Their inherent characteristics are used to strengthen structural elements made of various materials and to increase their durability. The following paper contains the results obtained in a conducted research program aimed at determining the ability to improve the durability of epoxy resin modified with the sonication process, microsilica and carbon nanotubes. The adhesive modified was used to adhere a CFRP tape to a concrete surface. Changes in the viscosity, physicochemical parameters and adhesion of the resin were studied. Selected parameters of the concrete substrate prepared using the sandblasting method, determined with the contact profilometry, were also taken into account. During the tests, attention was paid to the thorough execution and preparation of the samples. As a result of the research, it was demonstrated that the adhesion of the modified epoxy adhesive to concrete could be increased by approximately 28% in the case of the addition of carbon nanotubes and by up to 66% in the case of the addition of microsilica. The modifications used, in addition to increasing the adhesion of the resin to the concrete substrate, were also aimed at reducing the weakening of the adhesive joints caused by oxidation of the resin over time. The results obtained will serve as a basis for evaluating the possibility of their use in the practical reinforcement of structural reinforced-concrete elements.

THE INFLUENCE OF MINERAL ADDITIVES ON THE PROPERTIES OF ULTRA-HIGH STRENGTH CONCRETE

The article presents the results of a study of the influence of highly active mineral additives on the physical and mechanical properties of ultra-high strength concrete. Currently, according to the classical concept of making ultra-high strength concrete, a significant amount of ultradispersed microsilica is introduced, which determines the increased cost of its preparation. In order to obtain cost-effective ultra-high-strength concrete, the composition of mixtures was evaluated according to the criteria of strength and economy by replacing microsilica with technologically optimized highly dispersed zeolite (SSA=1200 m2/kg), which belongs to the class of superzeolite. It is shown that for modified concrete with the addition of microsilica, the compressive strength after 2 days is 88.8 MPa, after 28 days ‒ 161.0 MPa. When microsilica is partially replaced by superzeolite, sufficiently high mechanical parameters are achieved: after 2 days the compressive strength is 75.8 MPa, after 28 days the strength increases by 2.1 times and is 163.2 MPa, in this case a flexural strength of 12.1 MPa is achieved. The microsilica has a positive effect due to increased reactivity, especially at an early age. Similarly, the fine fraction of superzeolite is characterized by the acceleration of the pozzolanic reaction, while the coarser fraction contributes to increasing the degree of hydration of the Portland cement due to the desorption of water molecules from micropores and provides internal care for concrete. The cementitious matrix is compacted by filling the intergranular space due to the formation of nanodispersed C-S-H phases. Thermal analysis showed that the amount of calcium hydroxide in the superzeolite cementitious system is 2.75% or 66 kg/m3, which meets the requirements for ultra-high strength concrete. The synergistic combination of microsilica and superzeolite with high surface activity and polycarboxylate superplasticizer provides high packing density and the necessary strength characteristics of ultra-high strength concretes, as well as contributes to their cost-efficiency, which opens the prerequisites for a large-scale engineering application of such concrete in construction.

Study of the behavior of reinforced concrete structures made from high-strength concrete during fire

Introduction. High-strength concrete has high mechanical strength and a number of other advantages, but is prone to explosive destruction during rapid high-temperature heating (in case of fire), which leads to a decrease in the cross-sections of reinforced concrete structures and premature occurrence of the fire resistance limit by loss of bearing capacity (R). The results of studies on the fire resistance of structures made of high-strength concrete are not available in the construction regulatory framework. The calculation method for assessing the fire resistance of structures made of high-strength concrete with fire testing has not been worked out too.Aim. Experimental study of fire resistance of reinforced concrete slab structures made of high-strength concrete of B60 and B100 classes, taking into account the influence of the process of explosive destruction of highstrength concrete in case of fire.Materials and methods. Concrete samples and full-scale slabs made of high-strength concrete with the addition of microsilica of B60 and B100 classes were subject to research. Full-scale solid-section slabs made of highstrength concrete of B60–B100 classes with steel reinforcement of A500C class were subject to fire tests. Based on the results of fire tests, the limits of fire resistance of full-scale slabs of high-strength concrete and the specifics of explosive destruction of high-strength concrete in a fire were determined.Results. The article presents the results of experimental studies and fire tests of the fire resistance of slab structures made of high-strength concrete.Conclusions. The effectiveness of research is determined by the development of a computational method for assessing fire resistance for structures made of highstrength concrete during design. Based on the results of the work, the need for further studies of the fire resistance of different types of structures made of high-strength concrete, with variations of high-strength concrete classes and types, depending on their material and quantitative composition, was revealed.

Using of microsilica for improvement of physical and mechanical properties of epoxide-based composite material

Utilization of industrial waste and secondary raw materials, in particular, in the production of metallic silicon and silicon-containing alloys, which include silica vapors (microsilica), is the main task of implementing environmental policy and solves the problem of their storage and negative impact on the environment, in order to reuse them in polymer composites. The use of microsilica as a filler in composite materials based on epoxy resins contributes to a positive effect on the basic properties of the resin, and also makes it possible to use the composite material as coatings and parts in the repair of machinery and equipment. The aim of the work was to establish the positive effect of microsilica as a filler in composite materials based on ED-20 epoxy resin on improving the physical and mechanical properties of composite materials. Within the framework of this work, studies were conducted to test composite materials based on ED-20 epoxy resin, differing in different filler content of 2, 5, 10, 15 wt. % on impact strength, tensile strength and modulus of elasticity, adhesion and impact strength of the coating. The analysis of the obtained results showed a positive effect of microsilica as a filler in composite materials based on ED-20 epoxy resin on the physical and mechanical properties of the composite material. The optimal filler content was determined, which is 2 % of the mass of the ED-20 epoxy resin, while an increase in adhesion, toughness of the composite material by 45 %, tensile strength and modulus of elasticity by 21 % and 5 %, respectively, and the strength of the coating on impact by 32 %, compared with the addition of microsilica in ED-20, which shows the prospects of using microsilica as a filler in composite materials

The Influence of Recipe-Technological Factors on the Resistance to Chloride Attack of Variotropic and Conventional Concrete

A current problem in the construction industry is the lack of complex, scientifically based technological materials and design solutions for universal types of building materials, products, and structures, especially in terms of structures operating under conditions of aggressive chloride exposure. The aim of the study was to compare and evaluate the differences in the durability of conventional and variotropic concretes made using three different technologies, vibrating, centrifuging, and vibro-centrifuging, modified with the addition of microsilica, under conditions of cyclic chloride attack. Laboratory experiments and analyses using scanning electron microscopy were conducted. Vibro-centrifuged concrete showed the highest resistance to cyclic aggressive chloride exposure, which was expressed by a lower percentage drop in compressive strength compared to vibrated (87%) and centrifuged concrete (24%). The use of a microsilica as a modifying additive in the amount of 2–6%, instead of as a part of the binder, had a positive effect on the resistance of concrete to cyclic chloride attack. The most effective intervention was the introduction of additives in the amount of 4%. There was a reduction in the loss of strength of vibrated, centrifuged, and vibro-centrifuged concrete after 90 “dry-wet” cycles, as a result of the use of a modifying additive, in an amount between 45% and 55%, depending on the type of technology being used for producing a composite. The combined effect of the use of vibro-centrifuged concrete and microsilica led to a 188% decrease in strength loss resulting from cyclic chloride exposure.

Flexural performance of steel-concrete-steel sandwich beams with lightweight fiber-reinforced concrete and corrugated-strip connectors: Experimental tests and numerical modeling

The present paper experimentally investigates the flexural behavior of steel-concrete-steel (SCS) composite beams with lightweight polypropylene fiber-reinforced concrete core and corrugated-strip shear connectors. For this purpose, the four-point bending tests have been performed on 11 specimens. This aims to investigate the influence of lightweight concrete core on the performance of the beams, and therefore all the parameters in the tested beams are kept constant except the type of concrete core. Based on the results of the performed quasi-static loading tests, the observed failure modes and force-displacement curves are reported and analyzed to achieve a deeper understanding of the influence of lightweight fiber-reinforced concrete on the flexural behavior of SCS beams. It was found that the utilization of polypropylene fiber has an improving influence on the performance of SCS beams, and especially enhances their toughness and ultimate deflection. A positive linear relationship between the fiber content (up to 2 %) with the specimen’s toughness was detected. It was also found that the addition of micro-silica to the lightweight fiber-reinforced concrete core results in considerable improvement in the flexural load capacity of the tested SCS beams. In addition, numerical finite element models including detailed material and geometric modeling of SCS beams are developed using the general software package ABAQUS. The accuracy of the developed models is validated using the attained experimental results. The numerical models can be used to simulate the load-deflection behavior and ultimate strength of SCS sandwich beams.

A multi-criteria evaluation and optimization of sustainable fiber-reinforced concrete developed with nylon waste fibers and micro-silica

Nylon waste fibers similar to new nylon fibers possess high tensile strength and toughness; hence, they can be used as an eco-friendly discrete reinforcement in high-strength concrete. This study aimed to analyze the mechanical and permeability characteristics and life cycle impact of high-strength concrete with varying amounts of nylon waste fiber and micro-silica. The results proved that nylon waste fiber was highly beneficial to the tensile and flexural strength of concrete. The incorporation of a 1% volume of nylon waste fiber caused net improvements of 50% in the flexural strength of concrete. At the combined addition of 0.5% volume fraction of nylon fiber and 7.5% micro-silica, splitting tensile and flexural strength of high-strength concrete experienced net improvements of 49% and 55%, respectively. Nylon fiber-reinforced concrete exhibited a ductile response and high flexural toughness and residual strength compared to plain concrete. A low volume fraction of waste fibers was beneficial to the permeability resistance of high-strength concrete against water absorption and chloride permeability, while a high volume (1% by volume fraction) of fiber was harmful to the permeability-resistance of concrete. For the best mechanical performance of high-strength concrete, 0.5% nylon waste fiber can be used with 7.5% micro-silica. The use of micro-silica minimized the negative effect of the high volume of fibers on the permeability resistance of high-strength concrete. The addition of nylon waste fibers (at 0.25% and 0.5% volume) and micro-silica also reduced carbon emissions per unit strength of concrete.

Experimental studies of the strength of fine-grained concrete with implementations of organomineral additives

Experimental studies of the strength of fine-grained concrete with implementations of organo mineral additives were carried out. The organo mineral additive in the amount of 5-15% by weight of cement has a significant effect on the strength characteristics. Zeolite-containing rock with a specific surface area of 4000 cm2/g was used in the studied compositions. The amount of water added to the mixture also increases with an increase in the amount of organo mineral additive in the concrete mixture. The introduction of an organo mineral additive as a mineral additive instead of a part of the cement promotes the pozzolanic process, in which amorphous silica (SiO2) is bound to the lime formed during cement hydration as a result of the transition to down-basic hydro silicates. The addition of zeolite-containing rocks in an amount of 5-15% by weight of cement has a significant effect on the strength characteristics. The greatest increase in compressive and flexural strength is achieved by replacing 10% cement with TPP ash (heat from a power plant). It was established that a 10% dosage of TPP ash is optimal and is used for a further selection of the composition of fine-grained concrete. The resulting mixture has increased workability and plasticity. The most optimal dosage of additives is 1-1.5%. As the second mineral additive, we used an additive of technogenic origin - microsilica, i.e. ash from burning rice husks. After studying the literature, it was concluded that the addition of microsilica in an amount of 10-12% by weight of cement most contributes to increasing the strength of concrete. The research work is aimed at improving the properties of cellular concrete, developing their composition and production technology by introducing minerals and modifying additives. The results of the research work provide an increase in manufacturability, strength, water and frost resistance, and operational reliability of the obtained materials. The joint implementation of ash and a chemical mixture into fine-grained concrete allows concluding that the strength indicators increase, and the water-cement ratio and porosity decrease.

Research on the effect of microsilica on the properties of the cement-sand mixture

The article presents a study of changes in the mineralogical composition of cement when adding microsilica of different concentrations using diffractometer DRON-3 with СuCa-radiation, β-filter. X-ray phase analysis on a semi-quantitative basis was carried out on powder sample diffractograms using the method of equal weights and artificial mixtures. The work examines the effects of microsilica on the mineralogical composition of cement at the microstructural level. The aim of the study was to improve the physico-chemical properties of the cement. Solutions with different percentages of microsilica additives (0 %, 10 %, 20 %, 30 %) were made for the analysis. The conducted research makes it possible to determine the effect of microsilica in different concentrations on the properties of the cement composition. The introduction of additive into products is introduced to increase mechanical properties, reduce porosity, increase water resistance and durability of products, possibly due to binding of calcium hydroxide in the structure of hardening cement stone by dispersions of microsilica. In general it can be concluded from the results of studies that the additive contributes to increasing the strength of the mixture, accelerating hardening. Consequently, the additive is one of the most effective additives to increase the strength.

Effect of Micro-Silica on Fresh and Hardened Properties of Self-Compacting Concrete Reinforced with Glass and Polyvinyl Alcohol Fibres

Self-compacting concrete (SCC) being an innovative and environmentally friendly concrete is impressively accepted in various regions of the world. SCC is a high-performance concrete that can consolidate under its own weight without the aid of mechanical vibration, filling spaces of almost any size and shape without segregation or bleeding. In this study, experimental investigations were carried out to improve the properties of self-compacting concrete by replacing cement with various percentages of Micro silica in SCC having fixed percentages of fly ash, glass, and polyvinyl alcohol fibre. Micro silica content varied from 2% to 10% by weight. Various tests like L-Box, V- funnel, Slump flow, and uniaxial compression tests were carried out on SCC, and the results have been compared with the control mix. It is observed that the hardened properties of the SCC improved with the addition of micro silica. However, the filling ability, passing ability, and resistance to segregation of fresh concrete mix with increasing micro silica content were found to reduce.

Testing of cement stone modified with an additive based on industrial waste

Nowadays under the conditions of intensively developing construction production, hardening time and strength of Portland cement are becoming more and more relevant research issues of this type of binder. The basic requirements to the cement stated in the normative industry documents are considered. The strength limits of Portland cement of normal and fast-hardening are given. Raw materials for the production of fast-hardening and high-strength cement must be homogeneous and provide a high degree of fineness of the binder to increase its surface area. The production of cement with the addition of microsilica will make it possible to obtain concretes with the given characteristics without additional costs. To describe the methodology of testing cement recommendations of the main regulatory documents operating in Kazakhstan are used. Necessary means and equipment used in the testing laboratory and satisfying the existing standards are listed in a sequential manner. The procedure of preparing standard samples of cement dough is described step by step. The prepared specimens were kept in water at the required temperature regime. Determination of bending and compressive strength was carried out on accredited equipment. Processing of test results of cement samples with and without additives is given. Setting times of cement samples of two compositions were carried out according to the requirements. The dependence of the activity of the cement setting process on its temperature has been determined.

Compaction Curves and Strength of Clayey Soil Modified with Micro and Nano Silica.

Some Clayey soils are generally categorized as weak soils, and structures lying on such soils have been exposed to severe damage. Therefore, the central thesis of this paper is the impact of a waste material known as a silica fume as nano and micro material on soil’s behaviour. To evaluate the effects of those additives on Atterberg limits, compaction characteristics and unconfined compressive strength, clayey soil samples have been transformed using micro and nano silica fume (by-product materials). In the current investigation, silica fume is used at four different percentages: 0, 2, 4, and 7%. The results show that the plasticity index of soil decreases with the addition of micro silica and increases with the addition of nano-silica. Increasing nano silica percentage improves the dry density of the compacted soil and reduces the optimum moisture content. An opposite behavior is observed with adding micro silica to compacted soil. Finally, 4% of silica fume is found to be the optimum dosage to improve the unconfined compressive strength of the treated soil with both additives. As a result, treating the weak clay soil with micro and/or nano-silica fume has the potential to be impactful.

Synergistic Effect of Nano-Silica and Micro-Silica Fillers on the Rheological and Thermal Properties of Epoxy Resins

This article aims to improve nanofiller dispersion in epoxy resins by using an electrostatic disperser (ED), as well as reduce costs by using a combination of microfillers and nanofillers. The ED method aids in homogenized mixing of nanofillers in epoxy resin, due to its jet elongation and shearing effect on a polymer mix. In this article, two concentrations (7.5 wt% and 5 wt%) of nanosilica are used with resin, and the rheological properties of hybrid composites are tested before and after the addition of 50 wt% microsilica. It is observed that the electrostatic dispersion method aids in the network formation of nanosilica, unlike the high shear (HS) method, wherein clusters of nanosilica are formed. Hence, the ED method aids in reducing the viscosity values with the addition of microsilica, which is helpful in the product molding process. A plausible mechanism of filler dispersion is explained for ED and HS methods. The morphological analysis showed that the composites are brittle due to the high silica content, and that the silica fillers are dispersed well within the epoxy matrix. The flexural strength lies in the same range for both composites prepared using ED and HS methods. Thermal conductivity depends both on nanosilica and epoxy matrix dispersion, while heat deflection temperature, thermal diffusivity and specific heat depend on the dispersion method.

Effects of phase-change material on performance of cement mortar at varying temperatures

Recent thermal effect reports have shown a widespread increase in temperature associated with global warming. The need to preserve building interiors at a steady, comfortable temperature has become a major task for engineers. This has resulted in the development of phase-change materials (PCMs), which can be positioned in the interior of building components to absorb heat from the surroundings. The main aim of this study was to examine the physical, mechanical and thermal properties of cement mortar incorporating encapsulated PCMs at different temperature phases. The materials required for the PCMs and encapsulation were selected based on economy, availability and temperature tolerance. The results were compared with a control specimen and improved behaviour in thermal resistance was noted. The compressive strength was reduced with an increased percentage of PCM; the reduction in strength could be compensated with the addition of micro-silica. Temperature phases did not have much influence on the strength and durability properties. Based on thermal resistance and strength properties, 5% PCM incorporation showed the best performance. An analytical model was developed using Comsol Multiphysics software to assess the thermal comfort in a building made of PCM-incorporated mortar block walls in comparison with conventional brick walls.