Viscosity Modifying Agent Research Articles

An Experimental Study on the Rheological Properties of Self-Consolidating Mortars, Affected by Superplasticizer, Waste Marble Powder, and a Viscosity-Modifying Agent

An Experimental Study on the Rheological Properties of Self-Consolidating Mortars, Affected by Superplasticizer, Waste Marble Powder, and a Viscosity-Modifying Agent

Influence of chemical admixtures on buildability and deformation of concrete for additive manufacturing

In this study, the buildability of three-dimensionally (3D) printed (3DP) concrete that uses coarse aggregate was evaluated in the fresh state according to the contents of three chemical admixtures (high-range water-reducing agent (HRWRA), viscosity-modifying agent (VMA), and setting-time modifying agent), and the correlation between fluidity changes and buildability was analyzed. Polycarboxylate HRWRA and VMA contents were varied to control the flowability and static yield stress, which affect the workability. In addition, the SMA content was varied, and slump tests and table flow tests were performed at 30-minute intervals up to 6.5 h after mixing to measure flowability. Simultaneously, static yield stress was measured to analyze rheological changes, and penetration resistance and green strength tests were performed to analyze the main factors influencing buildability over time. The highest buildability was observed when the VMA content was 1.5 %. The static yield stress of fresh concrete could be ≤3000 Pa to guarantee adequate 3DP concrete transport performance while that at 1 h after mixing could be ≥2000 Pa to secure buildability. When the penetration resistance of fresh concrete is ≥80 kPa, the deflection of concrete may be <10 %. Through this, buildability can be approximately judged based on penetration resistance.

An investigation of rheological properties and sustainability of various 3D printing concrete mixtures with alternative binders and rheological modifiers

This study assessed the performance of eco-friendly 3D printable mixtures prepared with various wastes such as fly ash (FA), granulated blast furnace slag, and marble dust. Additionally, the study investigated the impact of a viscosity-modifying agent (VMA) and silica fume (SF) on the mixtures’ rheological and mechanical characteristics. The influence of different wastes and VMAs on the fresh and hardened properties of printable mixes was investigated. Besides, the extrudability and buildability properties of the mixtures were evaluated with a manual extrusion device. The sustainability assessment was conducted using embodied CO2 and embodied energy index, integrating both the mixtures’ environmental implications and engineering characteristics. Experimental outcomes indicated that the inclusion of SF led to enhancements in the fresh properties of the 3D printable mixes. The VMA mixes exhibited significantly higher static yield strength than mixes incorporating SF. Considering printability and sustainability, the FA-SF mixture was identified as the optimal one.

Enhancing the performance of 3D-printed fiber-Reinforced mortar: synergistic effects of clays and bacterial cells as viscosity modifying agents

The absence of standardized 3D concrete printing mixtures drives ongoing material exploration. This study investigates mineral and bio-based viscosity modifying agents (VMAs) application in fiber-reinforced cementitious mortar. Nano-montmorillonite, sepiolite, and bacterial cells function as supplementary materials, partially substituting cement with fly ash for sustainability assessment and compatibility evaluation in our study. Mechanical tests encompass compressive, flexural strength, and interlayer bonding in 3D-printed samples. Based on the results, incorporating 0.150% Polyamide (PA) fiber positively affected interlayer bonding strength and deceleration of the flow loss rate. Additionally, adding clays decreased workability and compressive strength but improved interlayer bonding and flexural properties. On the other hand, substituting 20% of cement with FA improved the flowability of the mixture and showed great compatibility with other materials during printing. Applying a cement paste layer was evaluated as a practical method for bond enhancement at the interface. Bacteria incorporation improved flexural strength but weakened interlayer bonding. However, the combination of bacteria and clays resulted in a superior improvement in mechanical properties. This study demonstrates clays and bacteria’s potential in enhancing rheological and mechanical features in cementitious fiber-reinforced mortar. Notably, this study introduces bacteria cells and sepiolite as rheology modifiers in 3D concrete printing for the first time. Additionally, it presents a novel dog-bone-shaped structure test for assessing interlayer bond performance.

Feasibility study on using red mud as a viscosity-modifying agent for self-compacting concrete

Red mud (RM) is a hazardous waste material generated during the alkaline leaching of bauxite in the Bayer process. The feasibility of using RM as a viscosity-modifying agent (VMA) for self-compacting concrete (SCC) was proposed in this study. In addition, RM paste, cement paste, RM-blended paste, SCC that containing RM as VMA were prepared, and those fresh properties were investigated with emphasis. The results show that compared to cement paste, the RM paste exhibited excellent water retention. In the RM-blended cement paste with equivalent fluidity, an increase in RM dosage led to a notable decrease in bleeding rate, accompanied by an increase in yield stress and plastic viscosity. Similarly, in the SCC (containing RM as VMA) with equivalent slump-flow, the segregation rate decreased significantly (17.12 % of segregation for SCC that without RM, and 6.88 % of segregation for SCC that with 12 wt% RM), while yield stress and plastic viscosity increased with higher RM dosages, demonstrating a linear relationship. These findings highlight the feasibility of achieving SCC with high slump-flow and non-segregation by using RM as VMA, and the fresh properties of prepared SCC can be effectively controlled. Meanwhile, the findings of this study offer a novel approach to utilize RM and provide valuable guidance for the application of RM used as VMA.

Comparative analysis of 3D printing of Portland cement mortars with hydroxypropyl methylcellulose and microfibrillated cellulose as viscosity modifying agents

The most used viscosity-modifying agents (VMAs) in 3D concrete printing (3DCP) are typically in powder form, which may pose challenges in dispersion and handling due to their low concentration and dust generation. This study explores the viability of using microfibrillated cellulose (MFC) in suspension and paste forms as a VMA in 3D-printable Portland cement mortars. The performance of these developed mortars was compared to a cement mortar containing hydroxypropyl methylcellulose (HPMC) in powder form. The mortars containing MFC in suspension and paste forms showed slightly higher workability, mechanical strength, and denser microstructure than those with HPMC. The MFC samples showed a higher viscosity and yield stress than the ones containing HPMC. A large-scale concrete 3D printer was used for the printability test. The HPMC mortars showed slightly superior extrudability and printability; however, the shape stability was inferior to that of the MFC mortars. The compressive strength of the 3D-printed samples was 40% lower compressive strength than the mold-cast samples; however, the flexural strength was comparable. Overall, the MFC in paste form outperformed the other VMAs studied here, providing better shape stability, while maintaining acceptable printability.

Formulation, Development and In-vitro Characterization of Modified Release Tablets of Curcumin

Objective: The current study set out to design and test a cost-effective system for developing modified-release tablets of curcumin in an effort to increase the duration of drug release. Because curcumin has a shorter elimination half-life, reducing the frequency of doses can increase its bioavailability. Methods: For improved drug retardation in the stomach environment, modified-release tablets were made utilizing the wet granulation method with various grades of high-potassium chloride (HPC) as the extended-release matrix-forming agent and katira gum as the viscosity-modifying agent. Combining the use of HPC and katira gum slows the drug’s release in the stomach. The sustained-release tablets had the highest rate of medication release for up to 24 hours with almost no stomach absorption. The medication and excipients did not interact, according to the fourier-transform infrared spectroscopy (FTIR) spectra. There was no evidence of drug-excipient incompatibility, according to differential scanning calorimetry (DSC) tests. Optimal formulation batch F2 modified release tablets showed no outward signs of deterioration after three months of storage, according to stability analysis. Further evidence that F2 was steady is the lack of variation in drug content and percentage of drug release. Conclusion: This study accomplished its stated goal of creating a modified-release tablet formulation that is both cost-effective and does not make use of coating technology.

Improving the air bubble stability of air-entrained mortar in low air pressure environments via adopted rheology and surface tension methods

Air bubble stability in cementitious materials in low air pressure (AP) environments is influenced by the Ostwald ripening process, which causes coarsening behavior of air bubbles. This research reports the enhancement of air bubble stability in low AP via the adoption of rheology and surface tension methods. Besides, the evolution of air bubbles during the cement early hydration process is proposed. It was found that incorporating viscosity-modifying agents (VMAs) and shrinkage-reducing admixtures (SRAs) resulted in improving air bubble stability by 37.7 % and 23.4 %, upon undergoing AP change from 100 to 60 kPa. Calculation of air bubbles via ripening equations under low AP revealed that VMA induced a notable decrease in the effective diffusion flux within fresh cement mortar, leading to a reduction of 9.8 % in air bubble ripening within 120 min. Conversely, SRAs were primarily aimed at reducing the initial dimensions of air bubbles.

An Experimental Analysis on Self Compacting Concrete with Different Grades

Abstract: Self-compacting concrete (SCC), moreover called self-consolidating concrete. It is able to stream beneath its possess weight to totally fill the formwork and accomplish total compaction, indeed within the case of over-burden fortification. Solidified concrete is thick, homogeneous and has at slightest the same specialized properties and toughness as conventional vibrated concrete. scc can be made utilizing the same fixings as customary concrete. In any case, a more tightly resistance is required to guarantee tight control of processability characteristics. The dosing of self-compacting blend is much more logical than that of standard concrete blends. SCC blend requires tall powder substance, less coarse total, exceedingly viable superplasticizer and VMA (viscosity modifying agent) to provide concrete blends soundness and fluidity. Workability of SCC could be a adjust of ease, deformability, fill capacity and isolation resistance.

Analyzing the potency of Viscosity Modifying Agents on the Characteristics and Static Segregation of Fresh and Hardened Fluid Concrete

Self-compacting concrete (SCC) represents a recent advancement in the field of concrete technology due to its ease of handling and placement. In order to regulate the internal integrity of the concrete, a supplementary mixture component is employed. The term used to refer to this particular component is a viscosity-modifying agent (VMA). Different quantities of VMA were incorporated into the concrete mixture in order to evaluate its performance in both the fresh and hardened states. This study focused on the impact of VMA (Viscosity Modifying Agent) on various characteristics of concrete mixes. Specifically, the features under examination included flowing time, slump flow, flow time into a 500-mm diameter, and resistance to vertical segregation. In contrast, a measurement was conducted on the compressive strength of the cured concrete. The utilization of the column of segregation test allows for the identification and assessment of static segregation in SCC mixtures. This test offers a direct quantitative determination of the stability of segregation in fresh concrete. The purpose of this experiment is to determine the precise quantity of coarse aggregate with a diameter above 8 mm present within a specimen of 300 mm in height. This can be achieved by conducting sedimentation tests at a specific time interval of 30 minutes after the pouring of concrete. The research results indicate that the addition of VMA had a substantial impact on the rheological characteristics of the concrete mixture. It effectively stabilized the mixture, minimized static segregation, and improved the compressive strength when compared to the reference mixture without VMA. Furthermore, a comprehensive illustration of the segregation phenomenon is provided by the column of static segregation tests.&#x0D;

Durability Study of Self Compacting Concrete Containing Fly Ash, Lime Stone and Sugarcane Bagasse

Abstract: Self-compacting concrete (SCC) is a unique kind of concrete that can flow and fill form work or moulds under its weight without the aid of vibration or mechanical compaction. SCC is accomplished using a specifically formulated mix that contains high-range water-reducing admixtures (super-plasticizers) and viscosity-modifying agents. Excellent workability, great flowability, and the capacity to pass through densely packed reinforcement without segregation are just a few of SCC's special qualities. SCC has many advantages, including increased construction efficiency, lower labor costs, improved durability, and better surface polish. The present study focuses on the durability properties of concrete mixes, which were designed using control, binary, and ternary cementitious systems. In the environment, wastes such as Fly Ash (FA), limestone (LS), and agroindustrial waste such as sugarcane bagasse ash (SCBA) are used as partial replacements for cement.

The influence of viscosity-modifying agent and calcium carbonate on 3D printing mortar characteristics

3D printing or additive manufacturing is an example of technology development in the construction sector. In 3D printing mortar, many things need to be considered regarding the characteristics of the mortar, such as workability, initial setting time, compressive strength, extrudability, and buildability. In previous studies, there were problems in the printing process, such as a lousy extrusion process and cracks in the 3D printing mortar sample. This study used calcium carbonate and a viscosity-modifying agent (VMA) to modify the mixture to achieve the desired characteristics. The extrudability and buildability were tested by observing the extrusion process and measuring the thickness and width of each layer printed. Based on the research, adding calcium carbonate and VMA can reduce workability and accelerate the initial setting time of the mixture. The use of VMA can reduce the compressive strength of the mixture. Using calcium carbonate and VMA can also increase the buildability of the mixture. From the compressive strength test, there was a decrease of 39.26% in the 3D printing mortar sample compared to the mortar cube sample. In addition, it was found that the 3D printing mortar is anisotropic, so the compressive force’s direction affects the compressive strength produced.

Printing quality control of cement-based materials under flow and rest conditions

Time-dependent rheological properties of cement-based materials have a significant impact on 3D printing processes, where multiple rheological requirements should be met. A proper high rate of structural build-up is recommended to ensure the buildability and stability of printed elements. However, the loss of workability may occur rapidly, resulting in a significant reduction in print quality. Workability and buildability requirements usually interfere due to the time-dependent rheological behavior of cement-based materials under flow and rest conditions. This research aims to highlight the effects of time-dependent behavior on the printability of cement-based materials. The coupling mechanisms of microstructure development at rest and under shearing conditions are discussed. A new thixotropy index is proposed to quantify the printability window of cement-based materials based on their structuration rates. An experimental study was conducted on printable mortars incorporating a viscosity-modifying agent (VMA) to assess printing quality as a function of the degree of thixotropy. Different types of stability failures were captured and discussed.

Matrix Tailoring for Polyvinyl Alcohol (PVA) Fiber-Reinforced Ductile Cementitious Composites

The main concern for the limited practical applications of strain-hardening cementitious composite, especially in China, is the high cost of imported materials, mainly polyvinyl alcohol fibers. This study uses local ingredients to develop strain-hardening cementitious composite reinforced with non-oil-coated Chinese polyvinyl alcohol fiber. The cementitious matrix consisting of cement, fly ash, viscosity-modifying agent, and silica fume was prepared, and the matrix tailoring was performed to achieve improved mechanical performance. The prepared composites were evaluated by rheology, three-point bending, and tensile characterizations. It is found that with the given local ingredients and matrix modification, the toughness index value of 100 ( I40) according to the American Society for Testing and Materials can be achieved. Besides, the tensile results showed the improvement of 45% and 60% for first-cracking strength and peak tensile strength values, respectively. The effects of matrix modification are also analyzed statistically using the analysis of variance for the mechanical properties of the cementitious composite. The post hoc statistical analysis using the Tukey–Kramer honestly significant difference illustrated the optimum cementitious mix from the experimental data. The presented results of cost-effective strain-hardening cementitious composite are expected to promote the practical applications of strain-hardening cementitious composite in China.

Influence of surfactant on foam generation and stabilization in cement slurry

Modern civil engineering and industrial buildings use foamed cement because of its low heat conductivity and light weight.Despite their high performance, foamed cement products manufactured solely from cement might be prohibitively expensive for commercial entities. Thus, chemically foaming cement is important. This paper compiles and reviewsthe foamed cement preparation, mostly used physical and chemical foaming processes. Physical foaming creates foamed cement by mixing foam into a slurry. Physical foaming methods are inefficient and energy-intensive. Chemical foaming involves adding a foaming ingredient to cement slurry. Foaming agents like surfactants react to create bubbles that expand the slurry. Surfactants in the liquid solution promote a bubble by spontaneously cicatrizing holes caused by external perturbations. These chemicals stabilize foams and bubbles for minutes to hours. Oil and gas well cementing uses Self-generated nitrogen foam cement (SNFC) with a high-efficiency foam stabilizer. Three surfactants produced cement pastes with and without MWCNT. A viscosity-modifying agent (VMA) in an aqueous cement paste dispersion can change its rheology. Sodium dodecyl sulfate (SDS) and CaCl2 increase nanosilica (NS) fluidity for pumping cement-based grout. FSCGM is used for coal mine infill grouting. Foamed sulfoaluminate cement-based grouting material (FSCGM) makes firefighting CO2 foam. Cement-hollow glass microballoon syntactic foams have greater compressive strength than neat cement at equal densities. Polydentatephosphonate-modified polymers and ester-type polycarboxylate superplasticizers create many cement mortar bubbles (PCE-1). Calcium ions stabilize polymer bubbles. Aqueous epoxy resin is added to cement slurries to reduce plastic viscosity and boost heat conductivity to make high-porosity cement foams (HPCF). Foamed cement bubble stability is highest at particle wetting angle π/2. SDS in silica suspension adjusts this angle. Ti-extraction blast furnace slag (TEBFS) foam with 20–40% sulfoaluminate cement (SAC) makes foamed cement.

Optimization of Workability and Compressive Strength of Self-Compacting Mortar Using Screening Design

In this study, the significance of several factors in the performance of self-compacting mortar was statistically investigated. A screening design was used as a suitable design to identify the most important factors that can affect workability and compressive strength. The purpose of the study was to obtain the optimal conditions which can lead to optimal workability (slump flow, funnel time) and maximal compressive strength (2 and 28 days). Four experimental factors each at two levels, the type of supplementary cementitious material (SCM) as silica fume (SF) and metakaolin (MK); the amount of (SCM) at 5% and 15%; superplasticizer (SP) at 0.3% and 1.2% and viscosity modifying agent (VMA) at 0.05% and 0.2% were selected as potential candidates affecting the experimental outputs. The analysis of the data to obtain optimal values of the outputs was carried out by using MINITAB®. To establish the factor levels selected in this study in order to achieve optimal workability and maximal compressive strength, response optimization was applied. The predicted conditions for optimal workability were found to be 8.84% SF, 1.2% SP and 0.15% VMA. The solution proposed to maximize the compressive strength was 0.3% SP, 0.05% VMA and 9% or 9.75% SF for 2 and 28 days, respectively. By setting the factors at the specified levels, experimental values of the slump flow at 278 mm; funnel time at 8.3 s; 2- and 28-day compressive strength at 22.8 and 66.1 MPa were achieved. This resulted in the predicted and experimental values at the optimum conditions being in strong agreement.

The Effects of Air-Entraining Agent on Fresh and Hardened Properties of 3D Concrete

Three-dimensional concrete printing (3DCP) is becoming more common in the construction industry nowadays; however, the aspect of durability of printed concrete is not well-studied yet. Frost resistance is a very important factor for durability of concrete structures located in northern regions. Since air-entraining agents (AEAs) are widely used in conventional concrete, this paper focuses on exploring the potential of using AEAs in 3D concrete as well—the main objective is to determine how it affects fresh and hardened properties, including frost resistance of 3D concrete. Three different mixes were printed and cast—the dry mix consisted of ordinary Portland cement (OPC), limestone filler (LF), sand, as well as viscosity modifying agent (VMA) and superplasticizer (SP). Two mixes contained different amounts of AEA, the third one was used as reference. First, fresh state properties were tested—air content, density, and mini cone flow test. Second, 28-day compressive and flexural strength tests were carried out; bulk and particle densities were also determined. Next, both cast and printed concrete samples were subject to freeze–thaw cycles according to provisions of CEN/TS 12390-9, mass loss due to surface scaling was determined for each sample. As a result, printed concrete samples containing AEA in the amount of 0.06% of binder mass showed the highest frost resistance—addition of AEA decreased both flexural and compressive strength of this printed concrete mix by 30–40%. To conclude, the obtained results give an insight of how addition of AEA to printed concrete mix affects its properties both in long and short term. Further research of certain aspects, for instance, the air void system and pore distribution is needed to gain a deeper understanding on how to increase durability of 3D concrete.

Utilization of Fly Ash as a Viscosity-Modifying Agent to Produce Cost-Effective, Self-Compacting Concrete: A Sustainable Solution

Sufficient deformability can be achieved in concrete while maintaining segregation resistance either by using a chemical viscosity-modifying admixture (VMA) or increasing the fine content in the concrete. Using VMA, the initial cost of self-compacting concrete (SCC) increases, making it unsuitable for general construction. As a result, alternative methods for lowering the cost of SCC must be investigated. In this study, we assess the effectiveness of fly ash (FA) as a viscosity-modifying agent in the production of cost-effective and durable SCC. We also forge new pathways for sustainable development. The percentage of FA, superplasticizer dose, and water/binder ratio were varied, whereas the amounts of cement and water, as well as fine/coarse aggregate content were kept constant. Fresh properties, such as flow, filling and passing abilities, viscosity, and segregation resistance, were measured. Compressive/flexural strength, density, water absorption, and rate of water absorption of hardened SCC were also determined. The test results showed that fly ash can be used as an alternative to a VMA to produce cost-effective, self-compacting concrete. The slump flow of the various fresh-state concrete mixes ranged from 200 to 770 mm, with an L-box ratio of 0 to 1 and a flow time of 2.18 to 88 s. At 28 and 56 days, the compressive strengths of the concrete mixes with fly ash were found to be comparable to those of the control concrete mixes with VMA. The cost of ingredients for a specific SCC mix is 26.8% lower than the price of control concrete, according to a cost comparison assessment.

Environmentally friendly viscosity-modifying agent for self-compacting mortar: Cladophora sp. cellulose nanofibres

Admixtures such as viscosity modifying agents and mineral admixtures could be used to regulate the rheological behaviour of the self-compacting concrete mixture. Herein, cellulose nanofibres obtained from Cladophora sp., a bio-waste that pollutes water bodies and threatens the ecosystem, were used to provide appropriate plastic viscosity in self-compacting mortars instead of a traditional viscosity modifying agent known as Welan gum (WG). Within the scope of the study, mini-slump, mini-V funnel, viscosity tests, compressive-flexural strength tests and FE-SEM analyses were performed on the mortar and cement paste specimens prepared. According to the rheological results, increases of up to 93% in plastic viscosity and increases of up to 10 times in yield stress were observed in the CCF-used specimens. On the other hand, increases in yield stress up to seven times and in plastic viscosity up to 37% were determined in the specimens with WG added. Moreover, as a result of mechanical tests, increases of up to 15% in compressive strength and up to 7% increases in flexural strength were observed in the WG-added specimens. While the decreases of up to 4% in compressive strength were observed, increases of up to 12% in flexural strength were detected in the CCF-added specimens.

The effect of different viscosity modifying additives on the mechanical and flow properties of self-compacting mortars

Some requirements are needed in the rheology design of special concretes such as self-compacting concrete, underwater concrete, shotcrete. For example, in the design of the desired concrete flow, some viscosity modifying agents (VMA) are used with various plasticizer additives. However, studies are needed to determine which of these additives used to design flow parameters is more appropriate. Herein, the mechanical and rheological effects of two commercially used VMAs on self-compacting mortars were investigated. For this purpose, compressive-flexural strength tests and mini-slump, mini-V funnel tests were conducted to determine the effects of welan gum (WG), and xanthan gum (XG) included in the mixtures at various ratios (0.01-0.1%) by weight of cement. The study supported by FE-SEM analysis concluded that WS had a positive effect on mechanical behavior, while XG had a negative effect, but XG was more effective on flow properties than WG.