Rheological Properties Of Concrete Research Articles

The rheological behavior characterization and prediction of cement concrete containing magnetite (Fe3O4) and/or carbon fiber

The effect of magnetite and carbon fiber (CF) on the rheological properties of concrete was investigated to reflect and affect its engineering performance development. The rheological parameters of concrete were measured. Next, a prediction model was established to predict the change tendency in the rheological properties of concrete. Then, the correlation between rheological and mechanical properties was investigated to explore the mechanism of rheological behavior on its engineering performance. The results showed that magnetite and CF had a significant effect on the rheological behavior of concrete. When the magnetite and CF contents were 50 % and 0.5 wt%, the yield stress and plastic viscosity of concrete increased by 210.77 % and 35.88 %, respectively, compared to the control group. The physical properties of the materials, their interaction with the cement matrix and their effect on the volume fraction of the concrete system are the main factors affecting the rheological properties of concrete. Meanwhile, the prediction model established by using the nonlinear surface fitting function could effectively predict the influence of materials on the rheological behavior of concrete. The R2 between the predicted and measured values of yield stress could be up to 0.99. However, under the condition of large magnetite and CF content, the aggregation effect of the materials had a certain influence on the plastic viscosity of the concrete, resulting in a certain deviation between the predicted and measured values, but the R2 could still be up to 0.89. It indicated that the prediction model had favorable reliability and accuracy. A strong correlation existed between the rheological parameters and mechanical strength of concrete. The effect of magnetite and CF on rheological properties of concrete promoted the internal microstructure characteristics optimization of concrete to affect its mechanical properties.

Opportunities and barriers of pozzolanic cements

AbstractNatural pozzolans have been used as building materials since ancient times. They are used as a supplementary cementitious material in combination with portland clinker to produce cements, characterized by high mechanical strengths and good durability performance. In the past the production of pozzolanic cement was mostly restricted to countries with natural pozzolan availability (Italy, Turkey, Greece, Philippine for example) and considered or even rejected in other countries that had the possibility of using other types of SCMs such as slag or fly‐ash. The market acceptance of natural pozzolanic cement also shows regional dependency. Colour and water demand strongly affect the perception and rheological properties of concrete containing natural pozzolan resulting in poor acceptancy in regions not used to working with this type of cement. Although, this SCM has been studied for very long time, today it makes sense to look closely at new pozzolanic binders. Innovative types of pozzolanic cement with very low clinker content are approaching the traditional cement market, due to the need for clinker factor reduction, and to the availability of separate grinding technology. New applications are being investigated with the aim of exploiting the behaviour of certain pozzolanic material to act as CO2 adsorbers for the removal of the exhaust gas during the production process. This paper will provide an overview of the most recent research work dealing with natural pozzolanic cement and the possible future opportunities and barriers offered by this very traditional and long‐used building material.

Nonlinear Deformation Model for Analysis of Temperature Effects on Reinforced Concrete Beam Elements

The results of the study are aimed at developing a nonlinear strain model for reinforced concrete beam elements in the general case of force actions and temperature effects for different durations. As a rule, temperature effects on structures involve temperature drops, causing heterogeneity of mechanical and rheological properties of concrete and reinforcement. The article has approximating expressions needed to take into account the effects of temperature and heating time on the values of temperature-induced strain and mechanical and rheological properties of heavy concretes with C30–C60 strength classes. The properties of concrete and rebars are heterogeneous from top to bottom and across the width of the cross section. A physically nonlinear problem is solved using the method of elastic solutions combined with the method of stepwise increases in temperature and force loading. The cooling of a heated reinforced concrete element to normal temperature is considered a short-term effect. Strength criteria of portions of a concrete cross section, crack closure conditions, and the ability of cracked sections to take loads in compression amid a change in the sign of stresses are determined. The stress–strain state (SSS) analysis of reinforced concrete beams, made according to the proposed method, is compared with the experimental studies using (i) values of thermal bending moments in statically indeterminate structures, (ii) cracking forces, and (iii) values of deformations (elongations and curvatures) of the elements in the longitudinal axis. Good agreement between the calculated and experimental values of controllable criteria confirms the reliability of physical relationships (i) developed for heterogeneous reinforced concrete beam elements and (ii) applied to the complex cases of temperature and force effects.

Study on the Synthesis and Rheological Properties of Polycarboxylate Superplasticizer with Different Main Link Density

Rheological properties of concrete are considered to be the most ideal method to characterize the working performance of concrete. Rheological models are used to quantitatively characterize the working performance of concrete based on the yield stress and viscosity of fresh cement paste. In this paper, Rheology QC was used to study the influence of different main link densities (acid-ether ratios) on the rheological properties of fresh paste. The Bingham model was used to fit the rheological curve of the slurry, and the influence of different main link densities on the yield stress, plastic viscosity, and thixotropic ring area of the slurry was analyzed. And the structural characterization and concrete performance characterization were carried out. The results show that the plastic viscosity and yield stress decrease with the increase of the main link density, and the thixotropic area also increases first and then decreases. When the acid-ether ratio is 3.5, the dispersion, rheology, and thixotropy properties of the sample are better.

On the Stability of Eccentrically Compressed Reinforced Concrete Elements with a Small Eccentricity, Taking into Account the Rheological Properties of Concrete

In the practice of modern construction, flexible centrally and eccentrically compressed reinforced concrete elements are becoming more common. In this regard, the relevance of studying their work and the mechanism of bearing capacity exhaustion increases. There are two directions in determining the bearing capacity of these elements: calculation for stability and calculation for strength. The loss of stability in a number of cases, obviously, can cause the destruction of not only centrally, but also eccentrically compressed rods with small eccentricities, since under certain conditions they can practically turn out to be close in their work. The stability of these eccentrically compressed rods is calculated by multiple integration. Such a calculation is especially laborious for reinforced concrete elements. This article is devoted to the study of the stability of centrally and eccentrically compressed reinforced concrete rods with small eccentricities, taking into account the creep of concrete. An eccentrically compressed rod with a small eccentricity of length l is replaced by a centrally compressed rod of length l0 so that the bending arrow includes the eccentricity. The numerical values of the rheological coefficients are determined from the boundary values of the reduced stiffness, which varies along the length of the rod. Complicated integration is replaced by the solution of the differential equation of the bent axis of the rod in the form of a sinusoid half-wave.

Performance Modeling of Spherical Capsules during Mixing of Self-Consolidating Concrete

Autonomous healing is a very promising technique in self-healing concrete systems. For capsules to achieve their anticipated performance, they should be able to survive the harsh mixing conditions of concrete, yet rupture upon concrete cracking. At present, there are no standard test methods, either experimental or analytical, for determining the capsule survival rate during concrete mixing. This study investigates the correlation between the capsules' shell properties, concrete rheological properties, the capsules' external forces, and capsule survival rate during concrete mixing. Finite element and statistical modeling techniques were employed to evaluate the capsule performance and predict the survival rate of capsules during concrete mixing, with 68% confidence. The results revealed that the capsules' survivability during concrete mixing is highly influenced by the capsule's radius-to-thickness ratio, the rheological properties of the fresh concrete, the average-paste-thickness (APT) of the concrete mix, the aggregate content and angularity, and the speed of the mixer. In brief, capsules with a radius-to-thickness ratio between 30 and 45 are likely to survive concrete mixing and yet still rupture upon concrete cracking.

Bond behavior between steel bars and 3D printed concrete: Effect of concrete rheological property, steel bar diameter and paste coating

• The effects of the rheological property on the steel–concrete bond behavior of printed and cast samples were investigated. • The porosity at the steel–concrete interface is related to the bond strength. • The bond strength values of 3D printed samples with ribbed bars of different diameters were compared. • The rheological properties of fresh concrete for 3D printing are very significant to control the quality of reinforced 3D printed concrete. Due to the unique layer by layer deposition process of extrusion-based 3D printed concrete (3DPC), the bonding of steel bars with 3DPC differs from that with traditional cast concrete. To understand the steel-printed concrete bond behavior, this paper mainly explored the effect of preparation technologies, concrete rheological properties, steel bar diameter and paste coating on steel bars on the bond behavior between ribbed steel bars and concrete. According to pull-out test and X-ray computed tomography test, the results showed that bond strengths between 3DPC and steel bars were obviously lower than those between steel bars and cast concrete. The rheological properties of fresh concrete show significant impact on the bond behavior of reinforced 3D printed samples. Lower yield stress and plastic viscosity can narrow the bond strength gap between printed samples and cast samples. The utilization of surface coated steel bar with fresh cement paste can effectively enhance the steel-3DPC bond strength. The variations in steel–concrete bond strengths can be explained via pore structure at steel–concrete interface. The results suggest that it is of great importance to control the quality of reinforced 3D printed concrete by optimizing the rheological properties of fresh concrete for 3D printing.

Comparative study of evolutionary artificial intelligence approaches to predict the rheological properties of fresh concrete

Rheology has been an essential tool to control the fresh state properties of concrete in case of self-compacting concrete, 3d printing of concrete, and ultra-high-performance concrete. Through proper control of rheology, it is possible to achieve desire green strength concrete and free from honeycombing, bleeding, and segregation for self-compacting concrete. The rheological properties of concrete were investigated in the study with the application of machine learning methods. The decision tree (DT) and bagging regressor (BR) were employed to predict the plastic viscosity (PV) and yield stress (YS) of the concrete with various mixes. Total 140 data points (mixes) for concrete were used to the run the selected models to obtain the forecasted result for both PV and YS. Six input variables were used for running the models for two outcomes (PV and YS). Results revealed that the BR was more effective in term of predicting both properties PV and YS of concrete by indicating the coefficient of determination values 0.90 and 0.95, respectively. However, the said results for PV (0.90) and YS (0.93) from DT model was also satisfactory. The lesser values of the errors, root mean square error, mean square error, mean absolute error and the indication of high performance of the BR towards the prediction. The sensitivity analysis reflected the importance of each parameter with water and gravels having more than 50 % impact on PV output values, while for YS, both medium and small size gravels were found having impact more than 65 %. The statistical checks and method of k-fold cross over validation also confirms the accuracy of models.

Rheological properties of concrete with manufactured sand: A multi-level prediction

Conventional rheological predictions of concrete were mostly developed based on spherical aggregate assumptions whereas the particle shape of irregular aggregate significantly influences the rheological properties of concrete. In this study, rheological properties of concrete with manufactured sand (MS) are predicted concerning the particle shape of aggregate based on a multi-level biphase assumption. The relative plastic viscosity and relative yield stress at each level are demonstrated to present power-law relationships with the relative thickness of the corresponding suspending media. The proposed models are proved with high accuracy and robustness for predicting the rheological properties of mixtures with MS and coarse aggregate that have various particle shapes and particle size distributions. Based on the proposed predictions, the influences of particle shapes of MS and coarse aggregate on the rheological properties of mixtures can be represented by their effects on the relative paste film thickness (R_PFT) and relative mortar film thickness (R_MFT), respectively. The proposed multi-level prediction lays the foundation of mix proportioning of concrete with irregular aggregate according to the specified rheological requirements.

Effect of spiral blade geometry on 3D-printed concrete rheological properties and extrudability using discrete element modeling

Sizes and shapes of spiral blades have a great influence on 3D printable concrete construction. This study is presented to answer two research questions: How does spiral blade geometry affect rheological properties of 3D printing mixtures? What are effects of the rheological properties of 3D printing mixture on final extrudability? The discrete element model formed by particles bonded with liquid bridges is used to analyze the influence of 3D printer blade size, shape, and rotation speed on the extrudability of cement-based materials. It is demonstrated that effects of spiral blade geometry on rheological properties and resulting extrudability of 3D printing mixtures are considerable. The research results could be good references about geometry of spiral blades for 3D concrete printing industry. However, the microscopic time-varying constitutive model of particle bonding has not been generated in this paper. It might be one of the future research directions.

ВЛИЯНИЕ ПОЛЗУЧЕСТИ НА НАПРЯЖЕННО-ДЕФОРМИРОВАННОЕ СОСТОЯНИЕ ЖЕЛЕЗОБЕТОННЫХ МНОГОЭТАЖНЫХ ЗДАНИЙ

With long-term action of the load in concrete and reinforced concrete, an increase in inelastic deformations occurs, which is associated with the creep of concrete. The viscous properties of any concrete are determined by its measure of creep and creep coefficient. Modern software systems make it possible to calculate structures taking into account the rheological properties of concrete. To analyze the stress-strain state of a multi-storey building, taking into account the long-term deformation of concrete, a 45-storey model of a frame building was calculated. The creep characteristics of concrete were set according to Eurocode 2. The results of the calculation showed that the creep of concrete during its long-term deformation leads to a redistribution of forces in the building elements, an increase in floor slab deflections and an increase in the buckling of eccentrically compressed elements. A comparative analysis of the creep coefficients of high-strength concretes according to Eurocode 2 and SP 63.13330.2018 was carried out, which showed the need for an experimental study of the values specified in SP 63.13330.2018 due to a single coefficient for concretes of class B60-B100.

Effect of Waste Glass on Slurry Rheological Properties of Cement and Concrete

In order to realize the recycling of waste glass, the influence of waste glass on the rheological properties of cement paste and concrete was studied. The rheological parameters were obtained by linear fitting with Bingham model. The results showed that for cement slurry system, with the replacement amount of waste glass increasing from 0 wt% to 20 wt%, the plastic viscosity of slurry increased gradually, while the yield stress decreased. Fixing the replacement amount of fixed waste glass at 5 wt%, the plastic viscosity and yield stress of cement slurry decrease with the increasing dosage of polycarboxylate superplasticizer. The cement slurry conforms to the characteristics of pseudoplastic fluid. For initial concrete slurry system, with the increase of waste glass replacement amount from 0 wt% to 20 wt%, the plastic viscosity of slurry increased, while the yield stress gradually decreased. And then the rheological properties of concrete slurry were closed to Newtonian fluid. After 1 hour, the plastic viscosity of concrete increased first, then decreased, and finally increased again. The yield stress decreased gradually. And the rheological properties of slurry were also close to Newtonian fluid.

Evaluation on the rheological and mechanical properties of concrete incorporating eggshell with tire powder

The construction industry is the largest consumer of raw materials which are under the risk of exhaustion and depletion in the near future, which has prompted the usage of waste materials for the conservation of resource and as a solution for waste management. Two wastes that are widely produced but often inefficiently disposed are eggshell and waste tire. Hence, this paper aims to evaluate the rheological and mechanical properties of concrete incorporating eggshell and waste tire rubber using Response Surface Methodology (RSM). Concrete with eggshell as cement replacement and waste tire rubber as sand replacement was prepared with an interval of 5% up to 15% replacement of both materials. Rheological properties of concrete were accessed using slump cone test while mechanical properties were studied through compressive strength and flexural strength test. Result showed that eggshell replacement has a minor effect on concrete slump while tire rubber reduces workability considerably. Result also showed that concrete mechanical strength was optimum at 5% and 10% eggshell replacement, while tire rubber reduced mechanical strength with percentage of replacement. Non-destructive tests indicated that concrete has excellent quality but excessive tire replacement beyond 10% compromised structural integrity of concrete. Overall, RSM models were able to model the properties of concrete with high accuracy and minimal deviation.

Assessment of the Rheological and Mechanical Properties of Geopolymer Concrete Comprising Fly Ash and Fluid Catalytic Cracking Residue as Aluminosilicate Precursor

The use of fluid catalytic cracking (FCC) by-products as aluminosilicate precursors in geopolymer binders has attracted significant interest from researchers in recent years owing to their high alumina and silica contents. Introduced in this study is the use of geopolymer concrete comprising FCC residue combined with fly ash as the requisite source of aluminosilicate. Fly ash was replaced with various FCC residue contents ranging from 0–100% by mass of binder. Results from standard testing methods showed that geopolymer concrete rheological properties such as yield stress and plastic viscosity as well as mechanical properties including compressive strength, flexural strength, and elastic modulus were affected significantly by the FCC residue content. With alkali liquid to geopolymer solid ratios (AL:GS) of 0.4 and 0.5, a reduction in compressive and flexural strength was observed in the case of geopolymer concrete with increasing FCC residue content. On the contrary, geopolymer concrete with increasing FCC residue content exhibited improved strength with an AL:GS ratio of 0.65. Relationships enabling estimation of geopolymer elastic modulus based on compressive strength were investigated. Scanning electron microscope (SEM) images and X-ray diffraction (XRD) patterns revealed that the final product from the geopolymerization process consisting of FCC residue was similar to fly ash-based geopolymer concrete. These observations highlight the potential of FCC residue as an aluminosilicate source for geopolymer products.

Розрахунок монолітної плити з урахуванням реологічних властивостей залізобетону

Виконано розрахунок монолітної плити перекриття з використанням методу «інженерна нелінійність». Зроблено аналіз впливу понижених жорсткісних характеристик на результати напружено-деформованого стану та підбір армування.

Effect of Alkali Reactions on the Rheology of One-Part 3D Printable Geopolymer Concrete

Yield strength development of 3D printable concrete by the early age activation reactions plays a vital role in the printability of geopolymer concrete. This study presents a rheo-chemical approach to investigate the early age strength development due to alkali reactions for the formulation of suitable 3D printable one-part geopolymer concrete. The influence of design parameters, including activator content, thixotropic additive (Magnesium Alumino Silicate -MAS), and retarder (sucrose) dosage, on the rheological properties of concrete were assessed. The shear stresses of geopolymer concrete were measured with the aid of a rotational rheometer for various shearing protocols that represent the major stages of printing operation (pumping, extrusion and building). The measured rheological properties were related to reaction kinetics of geopolymer mixes using FT-IR spectroscopy and calorimetry. The results revealed that, with MAS, activator and sucrose content of 0.75 wt%, 10 wt% and 1.5 wt% of the binder respectively, the formulated one-part geopolymer showcased enhanced printing properties. This is further demonstrated by printing laboratory-scale specimens and evaluating the hardened properties.

Strength characteristics of concrete using coconut shell as a coarse aggregate – A sustainable approach

Many researchers have carried out works on use of various agricultural and industrial by-products to enrich the performance and strength characteristics of concrete. The study here reports and captures the use of coconut shell (CS) as partial replacement to coarse aggregate (CA). CS is a naturally available abundant agricultural waste material, which can be used as an alternate to CA. For this research, authors considered M20 grade concrete to investigate the rheological and strength characteristics of concrete incorporating CS as an alternate material for CA in varying percentages like 0%, 5%, 10%, 15%, 20%, 25%, and 30%. The study aims to find the optimum dosage of coconut shell that can be replaced partially in concrete to enhance the strength characteristics and to make concrete lightweight by overcoming the disposal challenges of agricultural waste. Total of seven mixes are considered for this investigation to attempt CS a substitute for CA. The rheological properties like slump & compaction factor tests are conducted for fresh properties. Similarly, strength characteristics of concrete like compressive, split tensile and flexural strength tests are performed to measure the structural performance of CS as a CA. Test outcomes of this investigation exhibits that, CS can be replaced up to 20% by weight of CA, without compromising the strength characteristics and rheological properties of concrete. Use of CS as a CA in concrete production not only contributes to performance and strength of concrete but also solves the solid waste disposal problem and helps in conserving natural resources.

How quarry waste limestone filler affects the rheological behavior of cement-based materials

AbstractThe main objective of this work is to highlight experimentally the effect of quarry waste limestone fillers (LF) on the rheological properties of concrete. All mixtures were made with water-to-cement ratio (W/C) of 0.50. The method adopted based on the rheological behavior of concrete incorporating LF as a partial substitute for sand in multi-scale systems (concrete, mortar, grout and LF suspension). The replacement ratio of sand by LF ranged from 0% to 20% (by weight of sand) in concrete and mortar. Whereas, the addition of LF varied from 0% to 60% (by weight of cement) in cement grout. The rheological behavior of concrete and mortar was modeled by the Bingham model with sufficient precision. However, the cement grout shows a nonlinear behavior, which was modeled by the Herschel-Bulkley model. Results indicate that the use of LF has a significant effect on the superplasticizer (Sp) demand of concrete and mortar, for a given slump on one hand. On the other hand, an increase in yield stress, apparent viscosity and flow time of cement grout was obtained when LF is incorporated, which results in a loss of fluidity of the suspensions of LF.

Influence of a new dispersant additive amount on the structural and rheological properties of chamotte concrete and samples from it

The use of dispersing additives in the composition of concrete mixtures helps to reduce water demand, increase flow, increase strength after hardening in air. The effect of a new dispersant additive amount on a polycarbonate base in comparison with the currently used phosphate-containing additive on the structural and rheological properties of chamotte concrete from a mixture of the “SSHBD” grade and samples from it has been investigated. The optimal amount of new dispersant additive on the polycarbonate base has been established and it has been shown that, in its effect on the structural and rheological properties of concrete from a mixture of the “SSHBD” grade and the properties of samples from it, it is similar to the phosphate-containing additive used at present. The change nature of the concrete flowability is practically the same. "Vitality" (i.e. the time period during which the concrete mass is suitable for performing high-quality lining by vibrocasting) of the compared concretes is ~ 4 hours; cold crushing strength of concrete samples with additives after hardening in air for 7 days and heat treatment at a temperature of 110 °C, as well as cold crushing strength of samples after firing at a temperature of 1350 °C are practically the same. The use of new polycarbonate-based dispersant can be recommended for the preparation of chamotte concrete as an alternative phosphate-containing additive.

Effect of alkali reactions on the rheology of one-part 3D printable geopolymer concrete

Yield strength development of 3D printable concrete by the early age activation reactions plays a vital role in the printability of geopolymer concrete. This study presents a rheo-chemical approach to investigate the early age strength development due to alkali reactions for the formulation of suitable 3D printable one-part geopolymer concrete. The influence of design parameters, including activator content, thixotropic additive (Magnesium Alumino Silicate -MAS), and retarder (sucrose) dosage, on the rheological properties of concrete were assessed. The shear stresses of geopolymer concrete were measured with the aid of a rotational rheometer for various shearing protocols that represent the major stages of printing operation (pumping, extrusion and building). The measured rheological properties were related to reaction kinetics of geopolymer mixes using FT-IR spectroscopy and calorimetry. The results revealed that, with MAS, activator and sucrose content of 0.75 wt%, 10 wt% and 1.5 wt% of the binder respectively, the formulated one-part geopolymer showcased enhanced printing properties. This is further demonstrated by printing laboratory-scale specimens and evaluating the hardened properties.