Workability Of Concrete Mixture Research Articles

Structure and Properties of Variatropic Concrete Combined Modified with Nano- and Micro-silica

The lack of systematic information on the influence of the combined modification of variatropic concrete on their characteristics was revealed. The purpose of this work was to study the influence of the type of modifying additive, namely micro-silica, nano silica and their combination on the properties of concrete made using three different technologies - vibration (VC), centrifugation (CC) and vibration centrifugation (VCC). Concrete elements made using centrifugal compaction technology were subjected to additional sawing. Three types of modifiers were studied: micro-silica (MS), nano silica (NS) and their combinations. To determine the degree of effectiveness of each recipe solution, the following main characteristics were monitored: workability of concrete mixtures; density of hardened composites; compressive strength (CS) and water absorption (WA). When modifying MS, the greatest effect for VC, CC and VCC was observed with its amount of 8% instead of part of the cement. CS gains were up to 17% for VCC, and WA decreased to 25% for VCC. The NS modification showed the greatest effectiveness at a dosage of 4%. CS gains were up to 19% and WA decreased to 28% for VCC. A combined modifier of 75% MS and 25% NS showed the greatest effectiveness. CS increased up to 17% compared to effective dosages of single-component modifiers. The effectiveness of VCC, characterized by the percentage increase in CS, was up to 55% higher in comparison with VC and up to 25% higher in comparison with CC. WA of concrete decreased to 14% in comparison with effective dosages of one-component modifiers. The effectiveness of VCC, characterized by the percentage reduction in WA, was up to 30% higher compared to VC and up to 12% higher compared to CC. The greatest efficiency of all types of modifiers was observed in combination with the synthesized vibration centrifugation technology.

Study on the use of different machine learning techniques for prediction of concrete properties from their mixture proportions with their deterministic and robust optimisation

The construction industry relies so heavily on concrete that it's crucial to precisely forecast and optimize the strength and workability of concrete mixtures, while reducing costs as much as possible. For this objective, this study tries to predict and optimize the compressive strength and workability (slump) of concrete by using deterministic and robust optimization approaches, so as to determine the optimum concrete mixture proportions, while minimizing cost. Specifically, strength and slump were predicted based on concrete mixture proportions with five different machine learning techniques—support vector machine (SVM), artificial neural network (ANN), fuzzy inference system (FIS), adaptive fuzzy inference system (ANIS), and genetic expression programming (GEP), based on a dataset comprising two hundred concrete mixtures, which has various levels of key ingredients, including cement, water, fine aggregate, coarse aggregate, and size of coarse aggregate, along with their associated measures of strength and workability. These ingredients were used as input parameters, while compressive strength and slump (representing workability) served as output parameters for each mix proportion. Experimental investigations were conducted on fifteen distinct concrete mixes to validate the performance of the five networks, finding that ANFIS can yield the best results both for training and validation. This study provides valuable insights for predicting concrete properties and optimizing concrete mixture proportions, thus helping to maximize strength and workability while minimizing costs.

Influence of Polymer Fibers on the Structure and Properties of Modified Variatropic Vibrocentrifuged Concrete.

The application of polymer materials in concrete structures is widespread and effectively used. However, there is a lack of a systematic knowledge base about the structure formation and properties of variatropic vibrocentrifuged modified fiber-reinforced concrete. The purpose of this work is the investigation of the influence of polypropylene (PF) and basalt fiber (BF) and modification with microsilica (MS) on the properties of variatropic concretes obtained using the synthesized vibration centrifugation technology. Test samples were made using vibration centrifugation technology, followed by sawing. Various types of fiber reinforcement were studied, both individually and in combination. To determine the degree of effectiveness of each recipe solution, the following main characteristics were monitored: the density and workability of concrete mixtures; the density of hardened composites; compressive strength (CS); bending strength (BS); water absorption (WA). In variatropic vibrocentrifuged concrete, the greatest efficiency is achieved with dispersed BF reinforcement in an amount of 1.5%. Compared to the control composition, the increase in CS was 8.50%, the increase in BS was 79.17%, and WA decreased by 27.54%. With PF reinforcement, the greatest effect was recorded at a dosage of 1.0%. The increase in CS was 3.16%, the increase in BS was 10.42%, and WA decreased by 17.39%. The MS modification showed the best effect with 8% replacement of part of the Portland cement. The increase in CS was 17.43%, the increase in BS was 14.58%, and WA decreased by 33.30%. The most effective and economically rational formulation solution for vibrocentrifuged concrete is combined fiber reinforcement in combination with the MS modification in the following quantities: BF-1.0%; PF-0.5%; MS-8%. The increase in CS was 22.82%, the increase in BS was 85.42%, and WA decreased by 37.68%.

Influence of Graphene oxide on abrasion resistance and strength of concrete

Graphene Oxide (GO) has recently gained significant attention as a new carbon-based nanomaterial (CBN) in the civil engineering industry due to its exceptional mechanical and functional properties. It has been increasingly gaining popularity due to its superior dispersibility characteristics in aqueous solutions compared to the other graphene-based derivatives due to attached oxygen functional groups. A majority of current studies are focused on investigating the effect of GO in cement composites. However, the more useful applications of GO lie in its incorporation into concrete, as it is the most widely used construction material. Therefore, the current study determines the performance of GO-incorporated concrete in terms of strength and abrasion characteristics. Industrially produced GO was added to the concrete mixes at percentages varying from 0.02% to 0.08% by weight of cement (bwoc). A polycarboxylate-ether-based superplasticiser (PS) was used to enhance the dispersibility of GO within the mix and the workability of concrete mixtures. The Standard slump tests were performed to evaluate the workability of the mixes. Compression and indirect tensile strength tests were conducted to obtain the mechanical properties, while abrasion tests were employed to investigate the durability properties. In addition, microstructural properties were obtained using scanning electron microscope (SEM) analysis. The test results show that adding 0.08% GO bwoc in the concrete mix enhanced its compressive strength, indirect tensile strength, and abrasion resistance by 21%, 12% and 23% at 28 days compared to the control mix. At 56 days, results show 19%, 12% and 20% improvements, respectively. These findings confirmed that adding GO can enhance concrete's abrasion resistance and mechanical properties. Therefore, it demonstrates promising outcomes of utilising GO in applications such as road pavements, airport runways, industrial floorings and bridge decks where abrasion resistance and strength are key design parameters.

РАЗРАБОТКА КОМПЛЕКСНОЙ ДОБАВКИ ДЛЯ ПРОИЗВОДСТВА БУРОНАБИВНЫХ СВАЙ

The article presents the results of the effect of the additive on water resistance, frost resistance and workability, which are one of the main indicators of the physical and mechanical properties of concrete. In the presented work the authors used a complex additive containing alkali (caustic soda), post-alcohol bard and hardening regulator (gypsum) in different % ratios. It is shown that the use of a complex additive in the composition of concrete significantly increases the water resistance and frost resistance compared with the control samples. The influence of the complex additive on the workability of concrete mixture has been studied. It has been established that the complex additive allows obtaining highly workable concrete mixtures and reducing their water separation, providing high preservation of concrete mixtures. The water impermeability of concrete is also significantly improved - the water impermeability grade increases by 4 steps in comparison with the concrete without additive. The proposed method speeds up the process of determining the concrete water impermeability grade and allows you to determine the water resistance grade and the degree of permeability of concrete on the basis of the obtained dependencies. When adding a complex additive in an amount of up to 7 % of the weight of cement increases the brand on frost resistance. It is found that the concrete with the studied complex additive has high physical and mechanical properties. The optimum dosages of the considered additive were found and used in the present work.

Innovative use of agro-waste cane bagasse ash and waste glass as cement replacement for green concrete. Cost analysis and carbon dioxide emissions

The individual incorporation of cane bagasse ash (CBA) and waste glass (WG) as substitutes of cement changes the properties of concrete. The aim of this study was to investigate the effects of using CBA with WG as cement substitutes on concrete properties. Different mixtures with cane bagasse ash and waste glass were prepared. The workability of concrete mixtures was evaluated by slump test immediately after casting, density and compressive strength were tested at 28 days. Additionally, cost analysis, carbon dioxide emissions and alkali-silica reaction were evaluated. Using cane bagasse ash with waste glass to produce concrete achieved better results for physical and mechanical properties than the concrete mixture using CBA or WG individually as a partial substitute for cement. The experimental results show that the incorporation of cane bagasse ash decreased the slump related with the low water absorption of CBA. Additionally, the hardened density of concrete incorporating waste glass and cane bagasse ash was lower than traditional concrete, however a definite trend was not observed. The combined use of CBA and WG has a positive contribution in achieving the highest compressive strength. The results exhibited that the incorporation of cane bagasse improved the compressive strength. The CBA15:WG5 mixture can increase 20% compressive strength in comparison with CBA0:WG20 mixture (without CBA). Additionally, CBA15:WG5 mixture have 8% lower cost than the traditional concrete CBA0:WG0. With the partial substitution of 20% of cement by ashes from cane bagasse ash and waste glass, it is possible to reduce the emission of CO2 for each m3 of material produced. On the other hand, the introduction of cane bagasse ash reduces the alkali silica reaction effect.

Investigation study of enhance the strength by using hybrid nano-composites on conventional cement concrete

Generally, incorporation of nano-particles with conventional concrete (CC) materials expands the bulk belongings of concrete by renovating molecular structures and permits the cement-based materials converted high-strength and durable products. The concentrated tensile possessions of the concrete confines its submissions where the flexural and tensile possessions of the concrete are major. In this steel and synthetic-fibres are expressively enhanced the tensile, toughness, impact resistance and energy-absorption capacity (EAC) of the concrete. Even yet the presence of fibre enhanced the tensile strength capacity (TSC) of the concrete, it hasn’t better the compressive strength capacity (CSC) of concrete suggestively. Therefore, it is very overbearing in growth of compressive strength of the concrete where the compressive tensile belongings to the concrete are major for its application. Investigation was carried to study the impact of nano-Al2O3, nano-Fe2O3, and their hybrid combinations on the setting time, microstructure, fresh, and strength properties of conventional cement concrete. Binding material of concrete mixtures was replaced by different nanoparticles, namely nano-Fe2O3 and nano-Al2O3, with four replacement rates (up to 4 %) that makes somewhat of change in building materials and gives energy to the building. The slump cone test was performed to assess the workability of concrete mixtures. Strength characteristics were evaluated, including the compressive, split tensile, and flexural strengths, for mixtures hardened after 7, 28, and 90 days. Moreover, the slump value of the mixture was decreased with an increase in the replacement rate of nanoparticles. However, slump values were within the acceptable workability and did not affect concrete compaction. However, the strength enhancement of the hybrid nano mixtures was relatively equal to that of the mixtures with only nano-Fe2O3 or nano-Al2O3. The test results revealed that nanoparticles can enhance the strength and microstructure properties of concrete.

Optimization of Self-Compacting Concrete Containing Blast-Furnace Slag Compositions

The paper deals with composition design of self-compacting concrete containing blast furnace granulated slag and polycarboxylate type superplasticizer in a wide range of concrete strength classes. Optimal superplasticizer content, cement, and blast furnace slag consumptions are obtained from the viewpoint of minimum water demand and water-cement ratio, maximum self-compacting concrete mixture workability retention, and concrete strength. A significant effect of joint influence of superplasticizer and blast furnace slag is demonstrated. The possibility of minimizing the cement consumption at optimal superplasticizer content and slag consumption of 100–120 kg/m3 is shown. Dependences for calculating SCC strength at 1, 7, and 28 days vs. the water-cement ratio are obtained. It is found that the nature of correlation dependences for SCC splitting and compression strengths when using the blast furnace slag and the superplasticizer is linear. Optimization of SCC compositions using mathematical programming enables to obtain compositions with a lowest possible cost while providing a set of specified parameters.

Sustainability and mechanical property assessment of concrete incorporating eggshell powder and silica fume as binary and ternary cementitious materials.

Cement production emits a significant carbon dioxide (CO2) gas, dramatically influencing the environment. Furthermore, a large amount of energy is consumed during the cement manufacturing process; since Pakistan is already facing an energy crisis, this high energy consumption by the cement industry puts further stress on Pakistan's energy sector. Hence, the price of cement is rising day by day. Furthermore, waste disposals and concrete ingredients' restoration after demolition have adversative effects on the environment. Therefore, using these wastes decreases cement manufacturing, thereby reducing energy consumption, but it also aids in safeguarding the environment. The study aimed to determine the concrete properties by partially replacing cement with only eggshell powder (ESP) and combining ESP and silica fume (SF) in a ternary binder system in the mixture. However, workability, water absorption, compressive strength, split tensile strength, and flexural strength were all investigated in this study. In this experimental study, cement was replaced as 5, 8, 11, 15, and 20% of ESP, along with 5, 10, and 15% of silica by weight of cement in concrete. Approximately 21 mixes were prepared, from which 01 control mix, 05 mixes of ESP alone, and 15 mixes designed with a blend of ESP and SF with a 1:1.25:3 mix ratio and 0.5 water-cement ratios. Study parameters advocate the substitution of 11% ESP and 10% SF as the optimal option for maximum strength. Furthermore, combining ESP and SF diminishes the composite concrete mixture's workability and dry density greatly.

ВИКОРИСТАННЯ ДОСВІДУ БУДІВНИЦТВА МОНОЛІТНОГО ЦЕМЕНТОБЕТОННОГО ПОКРИТТЯ ЗЛІТНО-ПОСАДКОВОЇ СМУГИ АЕРОПОРТУ «ОДЕСА» ПРИ РОЗРОБЦІ НОВОГО ВІТЧИЗНЯНОГО СТАНДАРТУ НА ВЛАШТУВАННЯ АЕРОДРОМІВ

Abstract. Inspection of the monolithic cement-concrete pavement of the «Odessa» airport runway was carried out. Visual inspection of the runway surface, taxiways and apron for defects has been performed. The condition of the runway pavement was assessed as "excellent", destruction category I. In addition, strength tests of the rigid concrete pavement upper layer were carried out using non-destructive testing methods and core testing. The obtained strength characteristics correspond to the design requirements; the concrete has a grade of at least C32/40. Based on the processed data and own scientific developments, proposals were drawn up for a new standard (instead of SNyP 2.05.08-85 "Aérodromy") regarding the requirements for materials, concrete mixtures and concretes based on them for the runways construction in Ukraine. Modern requirements for monolithic cement-concrete airfield pavements require an extension of their service life up to 40 years. To ensure such indicators of serviceability, in addition to high strength indicators, it is imperative to ensure the rigid pavements durability using high-performance modified concretes. The proposals indicate the cement type, aggregates and chemical admixtures that can be used in the manufacture of concrete for airfield pavements. The requirements for the concrete and concrete mixture properties, the process of concrete curing are also presented. Taking into account the modern superplasticizers and the requirements for the workability of concrete mixtures for the construction of monolithic cement-concrete airfield pavements, the maximum W/C should be in the range of 0.3-0.35. To increase the flexural strength and crack resistance, it is desirable to use dispersed concrete reinforcement. To ensure the service life and satisfactory operational condition of the runway pavements, it is necessary to conduct an annual inspection for the timely identification and correction of arising defects.

Analysis of influencing factors of flow state concrete mixture performance

Based on the principle of benefiting the durability of concrete, machined sand is used to configure C40 flow concrete, and the engineering application environment and economy are considered. In this paper, the author through the flow state concrete mix ratio design, give the raw material dosage, concrete mixing, finally combined with the workability measurement method, five groups of concrete mix performance testing. According to the test results, the influence of mineral admixture and water reducing agent on the workability of concrete mixture is studied and analyzed, and the reasonable admixture dosage and water reducing rate of water reducing agent and its admixture dosage are finally given.

Theoretical analysis of water absorption kinetics of recycled aggregates immersed in water

Water absorption kinetics of recycled aggregates (RAs) is closely connected with the effective water to cement ratio (w/c), which influences the workability of concrete mixture and the performance of hardened concrete. However, experimental methods are talentless to uncover the detail of the process, especially the initial stage of the water absorption of RAs. In order to explore the mechanism of water absorption of RAs, theoretical analysis is conducted based on the experimental data. Firstly, a non-uniform cross-sectional capillary tube is introduced to investigate the mechanism of water–air displacement in RAs, which are immersed in water. Secondly, based on the Terzaghi capillary water rise model, a theoretical model is established to describe the initial stage of water absorption of RAs. Thirdly, the mechanism of water absorption of RAs during the second stage (slow water absorption stage) is analyzed theoretically. The results show that the process of water absorption of RAs can be divided into two stages: rapid water absorption stage and slow water absorption stage. The rapid water absorption rate during the first stage is caused by the high capillary pressure in small pores and large contact area of RAs with water. The slow water absorption rate during the second stage is mainly caused by two reasons: the bubbles adhered on the surfaces of RAs are not separated timely and the capillary pressure in big pores, which act as the exhaust passage during the first stage, is low.

Геополимерный бетон с использованием многотоннажных техногенных отходов

Introduction. Currently, in all countries, Portland cement is used as a binder in the production of concrete, and its global production accounts for 10 % of the total carbon dioxide emitted into the atmosphere. Therefore, Portland cement can be partially or fully replaced by new cement-free binders, made of large-tonnage technogenic waste with a cementing effect, for example, by finely ground blast furnace slag, fly ash generated by thermal power plants and ash formed during the combustion of rice hulls. Aqueous alkaline solutions (NaOH and Na2SiO3 or KOH and K2SiO3) should be used as activators of setting and hardening of such binders, and calcium sulfate dihydrate can be used to adjust the setting time. Concrete containing new cement-free binders is called geopolymer concrete. Materials and methods. In order to reduce mixing water consumption and maintain the required workability of the fine-grained concrete mixture, a polycarboxylate superplasticizer was introduced into its composition. All raw materials, except for the superplasticizer, were of the Vietnamese origin. The following research methods were used: the composition of the geopolymer concrete mixture was analyzed using the absolute volume method, the workability of the concrete mixture was determined according to ASTM C1611-18 и TCVN 3106:2007, compressive and tensile strength of the concrete, subjected to bending, were tested pursuant to GOST 10180-2012, and the average density of concrete was tested according to GOST 12730.1-78. Results. The co-authors have developed the composition of the geopolymer concrete containing the alkaline cement-free binder. As a result of the heat treatment of the 28-days-old concrete for 6 hours at 100 °C, its compressive strength reaches about 60 MPa; hence, it can be used in the hot and humid climate of Vietnam. Conclusions. This cement-free concrete, in addition to its high strength, has good water resistance and low water absorption. This concrete has economic benefits, and its production will help to protect the environment due to the lower consumption of natural resources and the applicability of large-tonnage technogenic waste.

Features of hardening and structure formation of concrete with high-dispersion mineral additives

The article deals with the effect of micro-filler additives on the properties of high-strength concrete. The effectiveness of microcements – mixtures based on highly dispersed cement and silica fume – has been substantiated. Using the methods of thermokinetic analysis and thermoporometry, the processes of heat release and the formation of microporosity during the hardening of ordinary cement and microcements without additives and with the addition of silica fume are studied. The positive effect of silica fume on the hydration and formation of the structure of cement stone is proved. It is shown that the nature of the hydration interaction in the system of “microcement - silica fume” contributes to the compaction of the structure and reduce the development of shrinkage phenomena. It was revealed that the use of microcementives allows to increase the workability of concrete mixtures and to accelerate the rate of curing of high-strength concrete. According to the results of the studies, the high efficiency of the use of components of the type “microcement – silica fume” in the technology of high-strength and durable concrete has been proved.

Experimental study on mixing proportion of reactive powder pavement concrete

Experimental study is carried out on mixing proportion of reactive powder pavement concrete. Writer studied influence of concrete admixtures such as silica fume, metakaolin and RPC special mineral filler. Studies have shown that: Silica fume can improve compressive strength of RPC. When metakaolin is used to replace some silica fume, compressive strength will decrease, but workability of concrete mixture will improve obviously. Thus, metakaolin should be add up according to specific situation. Special mineral filler can obviously improve construction performance of concrete mixture, reduce viscosity and increase slump without affecting compressive strength. Therefore, it should be add up firstly. At the same time, RPC100, which is suitable for road surface engineering, was successfully prepared, and its mixing proportion and related mechanical properties were obtained.

Development of high-strength self-compacting concrete with low fineness modulus sand

Self-compacting concrete is a highly flowing concrete that compact under self-weight without any vibration effort. The high workability of concrete mixtures is achieved by the reduction in coarse aggregate content while increasing fines aggregate volume. Usually, coarse quartz sands with fineness modulus more than 2.5 are used as fine aggregate. The use of low fineness modulus sands, characterized by high intergranular porosity and high specific surface area, as a fine aggregate, leads to an increase in the concrete mixture water demand and a decrease in its flowability. In such conditions, to obtain high-workability and high-strength concrete, increased cement consumption is required. The purpose of this study was to develop high-strength self-compacting concrete with reduced cement consumption and using low fineness modulus sand. To achieve this purpose, we optimized aggregates consumption in concrete composition, which achieves minimum aggregate mixture intergranular porosity, best concrete mixture workability without segregation, and maximum concrete strength. It has been established that silica fume and superplasticizer using allows obtaining high-strength self-compacting concrete of strength class B60 with low-quality fine sand and reduced cement consumption of 360 kg/m3. With increasing mixtures retention time before concrete placing, there was an insignificant increase in the flowability of obtained self-compacting concrete mixture and an improvement in the physical and mechanical properties of concrete. Remixing of concrete mixtures and concrete placing after 90 minutes from concrete mix preparation moment allowed to increase concrete strength to 17%, increase its density to 15 kg/m3, and reduce porosity to 25%.

Influence of Different Particle Sizes of Blast-Furnace Slag as a Fine Aggregate on Mechanical Strength and Abrasion Resistance of Concrete

This paper aims to study the effect of different particle sizes of granulated blast-furnace slag (GBFS) as a partial or full natural fine aggregate substitution in concretes with different water/cement (w/c) ratios. Natural sand fine aggregate was substituted with GBFS at ratios ranging from 25% to 100%, by weight. Two different particle sizes of GBFS (0.16 and 0.5 mm) and w/c ratios (0.5 and 0.6) were used. Workability, mechanical strength and abrasion resistance at ages ranging from 7 to 180 days were measured. The morphology of selected concrete samples were examined by scanning electron microscopy (SEM). The results showed a negative effect of GBFS fine aggregate on the workability of concrete mixtures. The incorporation of GBFS as a fine aggregate in concretes may increase or decrease mechanical strength and abrasion resistance. This depending on its particle size as well as w/c ratio.

Effect of fly ash on shrinkage of self-compacting concrete using restrained ring test

In recent years, fly ash (FA) has been increasingly used widespread like a mineral admixture for the production of concrete in general and self-compacting concrete (SCC) in particular. Fly ash is an industrial by-product and is generated during the combustion of coal for energy production from the thermal power station. Fly ash is utilized to increase the workability of concrete mixtures and increase shrinkage resistance of the self-compacting concrete. In this paper, the mixture design of the self-compacting concrete with strength grade of 60 MPa is performed with requirement that the workability satisfies the slump flow, T500 and the V-Funnel TV test range from 650 to 800 mm, from 2 to 5 s and from 6 to 12 s, respectively. Besides, fly ash is used to replace cement with content of 15%, 25%, 35% and 50% to evaluate shrinkage resistance. The obtained results showed that using fly ash contents from 25% to 35% to replace cement can ensure workability of the mixture together with high degree of shrinkage restraint. According to ASTM C1581, the evaluation of restrained shrinkage of the self-compacting concrete based on the restrained ring test, this method reduces the testing time but still ensure the reliability.
 Keywords:
 fly ash; self-compacting concrete; shrinkage resistance; restrained ring test.

Designing the Composition of Concrete with Mineral Additives and Assessment of the Possibility of Cracking in Cement-Concrete Pavement

Cement-concrete pavement not only has a long service life even at high loads but also has competitive production costs and fewer significant maintenance costs. The concrete road surfaces, thus, are rather economical. In this article, the Vietnamese Standard TCVN 9382 - 2012 was used to determine the heavyweight concrete composition for rural road construction. Assessment of the crack appearance in the concrete block body was made by the temperature field analysis, the thermal stress and cracking index. The conducted studies' result provided with the possibility of obtaining heavyweight concrete from Vietnam local raw materials regarding to the concrete mixture workability of 11-13 cm standard cone, 31-36 MPa compressive strength of heavyweight concrete at the age of 28 - day - normal hardening and 0.30 - 0.42 MPa average water resistance of samples. Using natural pozzolan to replace 20% of mass cement in the concrete mixture leads to a decrease in the concrete strength characteristics at different ages. The concrete compressive strength of composition No2 decreased mostly by 23% at the age of 3 days and least by 14% at the age of 28 days in comparison these values of composition No1. However, all of these concrete compressive strengths at the age 28 days are higher than 30 MPa. Replacing 20% of the mass Portland cement by natural pozzolan in a concrete mix will decrease price for 1 m3 concrete of 219.96 rubles. By applying the computer program MIDAS CIVIL, the maximum temperature in the concrete block center which was determined after 12 hours from the commencement of mixing of raw materials with water, equals to Tmax = 34.61 0С. At the same time, the structure temperature difference between the center (node793) and surface (nodes 120 and 898) of the concrete pavement can be neglected because of its insignificance. Besides, the cracking indexes at three hazardous locations of investigated structure are higher than 1, the cement-concrete pavement will be considered as non-appearance of cracks. However, the cracking index at center (node 793) is always less than this on the surface (nodes 120 and 898), equally to higher thermal crack occurrence at center. Therefore, it is necessary to monitor the development and expansion of thermal cracks to ensure the concrete mixture proper care during the hardening process.

INTERRELATION BETWEEN PLASTIC VISCOSITY OF CEMENT SYSTEMS AND THEIR RETHEHNOLOGICAL CHARACTERISTICS

Introduction . The theoretical basis for regulating the mobility and workability of concrete mixtures and other rheologically complex bodies is rheology. The authors give a clarification of the physical meaning of the terms plasticizer, superplasticizer, diluent of cement systems. Materials and methods . In the construction industry, suspensions and pastes are widely used to characterize the rheological properties of the cone spill, which does not always ensure the adequacy of their mobility. It has been found that the relationship between the plastic viscosity and the expansion of the cone depends on the degree of dilution of their modifying additives. Results . It is shown that the value of cone expansion, especially in the field of moderate doses of additives, adequately reflects the rheological properties of cement systems. With large and small values of plastic viscosity, the cone decay weakly reflects the rheological properties of disperse systems. Discussion and conclusions . Recommendations on the rational use of rasplav cone to characterize the technological properties of cement systems are given in the article.