Possibilities and challenges of constant shear rate test for evaluation of structural build-up rate of cementitious materials

Ivanova, Irina; Mechtcherine, Viktor

doi:10.1016/j.cemconres.2020.105974

Cited by 64 publications

(19 citation statements)

References 39 publications

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“…For 3DCP material as well as for other cementitious materials, the most commonly used rheology measurement protocols are the stress-growth test [54,[81][82][83] and performing the hysteresis loop test [81,[84][85][86]. For the stress-growth test, the material will be sheared with a very low constant shear rate (typically 0.01 to 0.001 s −1 ) and the shear stress variation will be recorded.…”

Section: Rotational Rheometersmentioning

confidence: 99%

Rheometry for Concrete 3D Printing: A Review and an Experimental Comparison

2022

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The rapid advancement of 3D concrete printing (3DCP) and the development of relevant cementitious material compositions can be seen in the last few decades. The commonly used 3DCP method is to build the structure layer by layer after extruding the material through a nozzle. Initially, the pumping and extrusion of the material should be done with considerable fluidity and workability. The extruded layers should retain their shape immediately after extruding and depositing. While constructing the structure in a layerwise manner, the bottom layers should have enough early age strength to support the layers at the top. Therefore, at different processes in 3DCP, the rheological requirement is contradictory. As the rheology of the material is the deterministic factor which decides the fluidity or workability of the mix, proper rheological characterization should be completed accurately. In some instances, due to the higher stiffness, and higher time and rate-dependent material behavior (thixotropic behavior) compared to the conventional concrete, standard rheology measurement techniques have many limitations when used for 3DCP material. Therefore, non-conventional and novel techniques can be implemented with suitable material models to characterize the rheology of 3DCP material. In this study, a comprehensive review was conducted on conventional and non-conventional methods used for characterizing the rheological parameters for 3DCP material. The previously conducted studies were highlighted with the targeted 3DCP processes in the study (if applicable), and rheological parameters achieved from the test (i.e., yield stress, viscosity, and thixotropy). In addition, some experimental studies were conducted to compare several selected testing methods. The rheological parameters achieved from different test methods were compared to identify the similarities, dissimilarities, pros, and cons between the test methods. Furthermore, the extrudability and buildability studies were conducted for the mixes to demonstrate the usage of the mixes in 3DCP applications and to correlate the achieved rheological parameters with these processes.

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Section: Rotational Rheometersmentioning

confidence: 99%

Rheometry for Concrete 3D Printing: A Review and an Experimental Comparison

2022

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“…And there are numerous activities on developing adequate test methods and protocols; see e.g. [79,80].…”

Section: Yield Stressmentioning

confidence: 99%

Extrusion-based additive manufacturing with cement-based materials – Production steps, processes, and their underlying physics: A review

Mechtcherine

Bos

Perrot

et al. 2020

Cement and Concrete Research

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350

127

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This article offers a comprehensive overview of the underlying physics relevant to an understanding of materials processing during the various production steps in extrusion-based 3D Concrete Printing (3DCP). Understanding the physics governing the processes is an important step toward the purposeful design and optimization of 3DCP systems as well as their efficient and robust process control. For some processes, analytical formulas based on the relevant physics have already enabled reasonable predictions with respect to material flow behavior and buildability, especially in the case of relatively simple geometries. The existing research in the field was systematically compiled by the authors in the framework of the activities of the RILEM Technical Committee 276 "Digital fabrication with cementbased materials". However, further research is needed to develop reliable tools for the quantitative analysis of the entire process chain. To achieve this, experimental efforts for the characterization of material properties need to go hand in hand with comprehensive numerical simulation.

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“…The static rheological properties were measured using the constant shear rate test and the single-batch approach, which were thoroughly described by the authors in [31] and [36]. In summary, the constant shear rate test includes determination of the peak values of torque at the lowest possible constant shear rate, or, more accurately, rotational velocity, at specific concrete ages.…”

Section: Determination Of Workability and Static Rheological Propertiesmentioning

confidence: 99%

“…However, a zero static yield stress measurement was performed at t age of 10 min, which provided proper rotor positioning in the sample before the main tests [31]. To prevent excessive disturbance of the sample, each measurement was broken off as soon as the peak value of torque was reached; the corresponding technique is described in [36]. The temperature of the freshly prepared concrete was 20 ± 2 • C and was maintained at 20 ± 0.5 • C during the entire testing period by means of a temperature control module.…”

Section: Determination Of Workability and Static Rheological Propertiesmentioning

confidence: 99%

Effects of Volume Fraction and Surface Area of Aggregates on the Static Yield Stress and Structural Build-Up of Fresh Concrete

Ivanova

Mechtcherine

2020

Materials

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With increasing interest in the use of additive manufacturing techniques in the construction industry, static rheological properties of fresh concrete have necessarily come into focus. In particular, the knowledge and control of static yield stress (SYS) and its development over time are crucial for mastering formwork-free construction, e.g., by means of layered extrusion. Furthermore, solid understanding of the influences of various concrete constituents on the initial SYS of the mixture and the structural build-up rate is required for purposeful material design. This contribution is concentrated on the effect of aggregates on these rheological parameters. The volume fraction of aggregates was varied in the range of 35% to 55% by volume under condition of constant total surface area of the particles. The total surface area per unit volume of cement paste was equal to 5.00, 7.25 and 10.00 m²/L, conditioned on the constant volume fraction of aggregates. Both variations were enabled by changing the particle size distributions of the aggregates while holding the cement paste composition constant for all concrete mixtures. To characterise the SYS and the structural build-up, constant shear rate tests with a vane-geometry rotational rheometer were performed. It was found that in the ranges under investigation the variation in volume fraction had a more pronounced effect on the static rheological properties of concrete than did the variation in surface area. An accurate mathematical description of the relationship between the initial SYS of concrete and the relative volume fraction of aggregate based on the Chateau–Ovarlez–Trung model was proposed. Challenges in deriving a similar relationship for the structural build-up rate of concrete were highlighted.

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Possibilities and challenges of constant shear rate test for evaluation of structural build-up rate of cementitious materials

Cited by 64 publications

References 39 publications

Rheometry for Concrete 3D Printing: A Review and an Experimental Comparison

Rheometry for Concrete 3D Printing: A Review and an Experimental Comparison

Extrusion-based additive manufacturing with cement-based materials – Production steps, processes, and their underlying physics: A review

Effects of Volume Fraction and Surface Area of Aggregates on the Static Yield Stress and Structural Build-Up of Fresh Concrete

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