Experimental and Discrete Element Model Investigation of Limestone Aggregate Blending Process in Vertical Static and/or Conveyor Mixer for Application in the Concrete Mixture

The numerical model of the granular flow within an aggregate mixture, conducted in the vertical static and/or the conveyor blender, was explored using the discrete element method (DEM) approach. The blending quality of limestone fine aggregate fractions binary mixture for application in self-compacting concrete was studied. The potential of augmenting the conveyor mixer working efficiency by joining its operation to a Komax-type vertical static mixer, to increase the blending conduct was investigated. In addition the impact of the feed height on the flow field in the cone-shaped conveyor mixer was examined using the DEM simulation. Applying the numerical approach enabled a deeper insight into the quality of blending actions, while the relative standard deviation criteria ranked the uniformity of the mixture. The primary objective of this investigation was to examine the behavior of mixture for two types of blenders and to estimate the combined blending action of these two mixers, to explore the potential to augment the homogeneity of the aggregate fractions binary mixture, i.e., mixing quality, reduce the blending time and to abbreviate the energy-consuming.

The use of glass waste cullet in the concrete production as an important factor in the circular economy

The paper focuses on the use of glass waste as a substitute for aggregates (0/4, 4/8 and 8/16 mm) in the production of concrete in order to reduce the negative impact of existing waste on the environment. For the study, 5 mixtures were designed with gradual replacement of individual natural aggregate fractions in the concrete mixture by glass cullet. Real density, total water absorption and compressive strength were monitored on cubes with an edge of 100 mm for a period of 14 days to 3 years. The achieved compressive strength of samples with glass as a filler at the level of 50 MPa gives a good precondition for the real use of such concrete in practice. In addition, when combined it with lower real density and total water absorption.

Synthesis of Niobium-Alumina Composite Aggregates and Their Application in Coarse-Grained Refractory Ceramic-Metal Castables

Niobium-alumina aggregate fractions with particle sizes up to 3150 µm were produced by crushing pre-synthesised fine-grained composites. Phase separation with niobium enrichment in the aggregate class 45–500 µm was revealed by XRD/Rietveld analysis. To reduce the amount of carbon-based impurities, no organic additives were used for the castable mixtures, which resulted in water demands of approximately 27 vol.% for the fine- and coarse-grained castables. As a consequence, open porosities of 18% and 30% were determined for the fine- and coarse-grained composites, respectively. Due to increased porosity, the modulus of rupture at room temperature decreased from 52 MPa for the fine-grained composite to 11 MPa for the coarse-grained one. However, even the compressive yield strength decreased from 49 MPa to 18 MPa at 1300 °C for the fine-grained to the coarse-grained composite, the latter showed still plasticity with a strain up to 5%. The electrical conductivity of fine-grained composite samples was in the range between 40 and 60 MMS/cm, which is fifteen magnitudes above the values of pure corundum.

Study of High Strength Concretes with Variability of Composition Designs

High Strength Concretes (HSC) are concretes defined mainly by compressive strength. The strength of concrete can guarantee other excellent results of properties, namely durability. Essential for the production of HSC is a careful approach to the design of concrete composition, especially the quality of raw materials. It is primarily necessary to increase the content of the binder combined mainly with Portland cement and another admixture. Due to its excellent properties, Silica fume is largely used as an admixture, where it is necessary to consider its effective amount. It is also suitable to combine this admixture with other types of active admixtures. The question of the type of coarse aggregate fractions used is crucial. The quality and purity of aggregates is an essential part of the quality design of these concretes, influencing practically all the resulting parameters of concrete. The article presents a set of tests on designed High strength Concretes, differing in the composition of the concrete to demonstrate the variability of the design concept and its effect on the resulting values of strength and durability.

Detection of Isopeptide Bonds in Monoclonal Antibody Aggregates

Purpose A major difficulty in monoclonal antibody (mAb) therapeutic development is product aggregation. In this study, intermolecular isopeptide bonds in mAb aggregates were characterized for the first time. We aim to propose a mechanism of covalent aggregation in a model antibody using stressed studies at raised temperatures to aid in the understanding of mAb aggregation pathways. Methods Aggregate fractions were generated using raised temperature and were purified using size-exclusion chromatography (SEC). The fractions were tryptically digested and characterized using liquid chromatography hyphenated to tandem mass-spectrometry (LC–MS/MS). Results An increased amount of clipping between aspartic acid and proline in a solvent accessible loop in the constant heavy 2 (CH2) domain of the mAb was observed under these conditions. Detailed peptide mapping revealed 14 isopeptide bonds between aspartic acid at that cleavage site and lysine residues on adjacent antibodies. Two additional isopeptide bonds were identified between the mAb HC N-terminal glutamic acid or a separate aspartic acid to lysine residues on adjacent antibodies. Conclusions Inter-protein isopeptide bonds between the side chains of acidic amino acids (aspartate and glutamate) and lysine were characterized for the first time in mAb aggregates. A chemical mechanism was presented whereby spontaneous isopeptide bond formation could be facilitated via either the aspartic acid side chain or C-terminus.