Modelling of rheological behaviour of macaíba pulp at different temperatures

ABSTRACT Fruit pulps undergo temperature variations during processing, leading to viscosity changes. This study aimed to analyse the rheological behaviour of macaíba pulp at different temperatures (10 to 50 ºC, with 5 ºC increments) and speeds (2.5 to 200 rpm, totalling 17 speeds). Experimental measurements were performed in a Brookfield viscometer, fitting the Ostwald-de-Waele, Mizrahi-Berk, Herschel-Bulkley, and Casson models to the experimental data of shear stress as a function of shear rate. Among the models used, the Mizrahi-Berk model (R² > 0.9656 and average percentage deviation - P ≤ 4.1%) was found to best fit the rheogram data. Macaíba pulp exhibited a non-newtonian behaviour and was characterised as pseudoplastic. It showed fluid behaviour indexes below unity under the studied conditions, with decreases in apparent viscosity as temperature and shear rate increased. Such behaviour could be described by the Arrhenius equation. The Mizrahi-Berk and Falguera-Ibarz models (R² > 0.99 and P ≤ 10%) best fitted the data and were used to represent the viscosity behaviour of macaíba pulp. The activation energy values of macaíba pulp ranged between 17.53 and 25.37 kJ mol-1, showing a rheological behaviour like other fruit pulps.

Effect of Mix Proportions on Fresh and Rheological Properties of Cementitious Mixture Containing Natural Fibre: Modelling Using Factorial Design

This paper aims to discuss the influence of mix composition of cement mortar on fresh and rheological properties of cement mortar. Two different natural fibres, basalt (BA) and sisal (SL) are selected based on fresh and rheological behaviour for its usability in a cementitious mixture. The workability and rheological behaviour are evaluated by flow table test, cone penetrometer and slump test of the mixture. A full factorial design method was used to investigate the effects of four mix components: dosage of cement content (B), percentage of fly-ash (FA) by mass of cement, dosage of basalt fibre (BA) and dosage of superplasticizer (SP) along with a water/binder ratio of 0.41. A mathematical model which predicts the main effect and interactions of these components for each of the measured properties are derived using the factorial design. The proposed mixtures consist of two levels of binder content as 550 kg/m3 and 650 kg/m3, FA as 5% and 20% by mass of cement, BA as 1 kg/m3 to 3 kg/m3 and SP as 2 kg/m3 to 4 kg/m3. By reducing the number of test batches needed, the mathematical models produced with this method can expedite optimizing the mixture proportions of cement mortar to achieve desired fresh and rheological properties.

Linseed Oil and Xanthan Gum: Promising Stabilisers for Earthen Building Materials

In the current context, the development of new bio-based and local building materials is becoming mandatory. Among them, earthen materials have a strong potential to be used as sustainable structural materials but their variability and their water sensitivity impact their mechanical properties that are difficult to guaranty. Recent developments have emphasised the ability of some bio-based additions to help to ensure these properties: linseed oil and xanthan gum are part of them. In this paper three different Breton earths, representative of a certain local variability, are studied. The impact of the selected bio-based additions on earths’ rheological behaviour is followed in order to adapt it to different forming processes. Then, the mechanical properties of different earth-addition combinations at the dry state, exposed to hygric variations and immersion are investigated for different forming processes. The findings highlight the fact that xanthan gum and linseed oil have a relevant ability to stabilise earthen blocks, that can be processed using different promising forming methods.

Rheological Behaviour of Cementitious Materials Incorporating Solid–Solid Phase Change Materials

Nowadays, thermal regulation of the indoor environment is mandatory to reduce greenhouse gas emissions. The incorporation of Phase Change Materials (PCMs) and especially solid–solid PCMs (s/s PCMs) into building materials can be a major step forward in reducing energy consumption. Such materials are used for their high latent heat to save and release heat during phase change. To integrate these products in the fabrication of cementitious materials, it is essential to predict their influence on the rheological behaviour of construction materials. In this work, rheological measurements were carried out on composite suspensions made of cement or mortar plus s/s PCMs. Results showed that the fitting of the Herschel–Bulkley model with a constant value of flow exponent was reliable. The s/s PCMs influenced the consistency and the yield strength values, with the yield strength value being only slightly affected. The adaptation of an existing viscosity model is proposed to predict the consistency value of suspensions. Finally, an innovative approach to predict the flow behaviour is proposed and we highlight the research needs to mainstream the use of s/s PCMs in construction materials.

A Rheological Study of Fibre Reinforced Composites and The Factors That Affect Rheological Behaviour During Impregnation Process: A Review

Rheological behaviour is an important factor affecting the flow behaviour of a fluid and many aspects related to this, mainly in the manufacturing process of fiber reinforced composites, either for Newtonian fluids or non-Newtonian fluids. During impregnation process, the viscosity changes with temperatures and their strain rate, has influenced the resin flow behaviour during curing process. In this paper, a review on the rheological studies of fiber reinforced composites for both, synthetic and natural based fibers, respectively, are presented. In addition to that, this review paper highlighting a few research studies conducted in literature on the main factors that affecting the rheological quality and performance of the composites. The aims of this review, mainly to capture the trend ranging from the recent five years back and summarize the various studies via experimental, theoretical or modelling works. Furthermore, also aiming to provide an ideal baseline information in the selection of the methods regarding rheological study to ensure better quality of pre-preg product and fibre reinforced composites can be produced in the author’s future work.

Rheology of mobile sediment beds in laminar shear flow: effects of creep and polydispersity

Classical scaling relationships for rheological quantities such as the $\mu (J)$ -rheology have become increasingly popular for closures of two-phase flow modelling. However, these frameworks have been derived for monodisperse particles. We aim to extend these considerations to sediment transport modelling by using a more realistic sediment composition. We investigate the rheological behaviour of sheared sediment beds composed of polydisperse spherical particles in a laminar Couette-type shear flow. The sediment beds consist of particles with a diameter size ratio of up to 10, which corresponds to grains ranging from fine to coarse sand. The data was generated using fully coupled, grain resolved direct numerical simulations using a combined lattice Boltzmann–discrete element method. These highly resolved data yield detailed depth-resolved profiles of the relevant physical quantities that determine the rheology, i.e. the local shear rate of the fluid, particle volume fraction, total shear and granular pressure. A comparison against experimental data shows excellent agreement for the monodisperse case. We improve upon the parameterization of the $\mu (J)$ -rheology by expressing its empirically derived parameters as a function of the maximum particle volume fraction. Furthermore, we extend these considerations by exploring the creeping regime for viscous numbers much lower than used by previous studies to calibrate these correlations. Considering the low viscous numbers of our data, we found that the friction coefficient governing the quasi-static state in the creeping regime tends to a finite value for vanishing shear, which decreases the critical friction coefficient by a factor of three for all cases investigated.