Hollow Beads Research Articles

Hysteretic Behavior and Restoring Force Model of Reinforced Glazed Hollow Bead Insulation Concrete (GIC) Columns

Based on the research of mix ratio and mechanical properties of glazed hollow bead thermal insulation concrete (GIC), the quasi-static tests of six GIC frame columns and one normal concrete (NC) frame column are carried out. The stress of frame columns under earthquake is simulated by applying a constant vertical load and cyclic horizontal load, and the hysteresis behavior, skeleton curve, ductility coefficient, stiffness degradation, and energy dissipation capacity of frame columns are studied. Contrast variables include axial compression ratio, stirrup reinforcement ratio and concrete material. The results show that the seismic performance of GIC frame columns is similar to that of ordinary concrete frame columns and frame columns. The stiffness degradation rate and ductility of GIC column are higher than that of NC column with the same parameter; higher axial compression ratio can increase the initial stiffness of GIC and reduce ductility; higher reinforcement ratio can increase ductility, but can limit plastic hinge development and reduce energy dissipation capacity of GIC column. The results can provide theoretical basis for elastic-plastic analysis of GIC column under earthquake action.

Adsorption of cadmium by a high-capacity adsorbent composed of silicate-titanate nanotubes embedded in hydrogel chitosan beads

ABSTRACT In this study, we developed a nanoparticle-based mesoporous composite that consisted of silicate-titanate nanotubes (STNTs) supported in hydrogel chitosan beads (STNTs-Ch beads) and was studied for Cd2+ adsorption. By using Fourier-transform infrared spectroscopy, transmission and scanning electron microscopy coupled to an energy-dispersive X-ray spectrometer, we could determine that the hollow STNTs were highly dispersed in the walls of the hollow beads. The dispersion was attributed to the effect of pH when the composite was prepared and we observed a non-interaction between STNTs and chitosan. The adsorption studies of Cd2+ showed that the kinetic rate (k 2) increased 3-fold and that the diffusion rate (K d) increased 2-fold after the embedment. Moreover, the maximum capacity of adsorption of STNTs-Ch beads was 2.3 times higher than that of STNTs alone. The treatment of a synthetic Cd2+ solution and a real leachate in continuous mode showed two phases in which it was observed higher removed fractions of transition metal ions (Cd2+, Co2+, Ni2+, Zn2+ and Cu2+) and the post-transition metal ion Pb2+, in comparison to the removed fractions of alkali and alkali-earth metal ions (Ca2+, K+, Mg2+). The composite was successfully reused four times when adsorbing Cd2+, saving three times the needed amounts of TiO2, SiO2 and chitosan for the production of the material. This composite was produced in a simple way and shows the potential for wastewater treatment.

Bond Behavior of Reinforcing Steel Bars in Thermal Insulation Concrete Exposed to Freeze-Thaw Cycles

An experimental study on the bond behavior of reinforcing steel bars in thermal insulation concrete (TIC) mixed with glazed hollow beads (GHBs) and exposed to freeze-thaw (F-T) cycles was carried out. In order to investigate the effects of GHBs on freezing and thawing, the experimental results were compared with those of normal concrete (NC). The comparison shows that, after 300 F-T cycles, both bond behavior and mechanical properties of the TIC specimens are better than those of the NC specimens. Furthermore, in order to investigate the mechanism of frost effect on TIC, the CT scanning method was used to investigate the evolution of the inner structure of a TIC specimen exposed to F-T cycles. The CT images show that the deterioration of bond performance and mechanical properties of the TIC specimen appears to be caused by the increase of micropores in the TIC.

PH-Sensitive Chitosan-Sodium Phytate Core-Shell Hollow Beads and Nanocapsules for the Encapsulation of Active Ingredients.

The oral administration of nutraceuticals and vitamins is the most compliant route because of its minimal invasiveness, painlessness, ease of use, and cost effectiveness. To overcome the possible destruction and low availability induced by the harsh gastrointestinal environment, we use sodium phytate as a cross-linker to fabricate pH-sensitive core-shell chitosan hollow beads and nanocapsules through the ionic linking method for the controllable release of active ingredients. Texture profile analysis, transmission electron microscopy, dynamic light scattering, and scanning electron microscopy were used to characterize the morphologies and behaviors of the beads and nanocapsules. The size of the beads could be adjusted from 0.1 to 10 mm, and the diameter of the nanocapsules was 50-100 nm. The addition of pectin in sodium phytate remarkably increased the hardness of the chitosan beads. Nile blue A was used as a model active ingredient for loading into the chitosan beads with the maximum encapsulation efficiency (EE) and loading capacity of 96.07 ± 2.45% and 9.61 ± 0.29%, respectively. Polyphenols including catechin, epicatechin, epigallocatechin-3-gallate, and proanthocyanidin were successfully loaded into the chitosan nanocapsules with an EE of above 90%. The cumulative release of Nile blue A from the beads at pH 1.2 (after 2 h) and pH 6.8 (after 6 h) was less than 20% and more than 80%, respectively. Similarly, the cumulative release of polyphenols in the nanocapsules at pH 1.2 (after 2 h) and pH 6.8 (after 6 h) was less than 30% and more than 70%, respectively. In sum, chitosan-sodium phytate with and without pectin could form pH-responsive macro- and nanoscale carriers suitable for the encapsulation and controlled release of active ingredients.

Influence of different fibers on properties of thermal insulation composites based on geopolymer blended with glazed hollow bead

In this work, fly ash and slag were used as aluminosilicate raw materials to prepare geopolymer paste, and different fibers and glazed hollow beads (GHB) were incorporated into the paste to produce various series of fiber reinforced geopolymer composites. The preparation process of geopolymer composites was explored and the optimum preparation conditions was obtained. Compressive strength, flexural strength, water absorption, porosity, thermal conductivity, linear shrinkage rate, microstructure and morphology have been characterized and assessed. Polypropylene fiber, alkali resistant glass fiber and lignin fibers were added to improve the cracking resistance and to enhance the strength. The results show that the optimal strength of fiber reinforced GHB blended geopolymer is obtained with 15% GHB addition, 0.75% fiber addition and liquid-solid ratio of 1.1. The improving effect of fibers on enhancing and anti-shrinkage follows the following sequence: PP fiber, alkali resistant glass fiber and lignin fiber. It is also observed that the fiber not only prevents the separation of the GHB and geopolymer matrix, but also inhibits the generation and expansion of the cracks, and finally improves the strength regardless of hybrid fibers or single fiber.

Effect of salty freeze-thaw cycles on durability of thermal insulation concrete with recycled aggregates

An experimental study on the durability of thermal insulation concrete with recycled aggregates (RATIC) subjected to the combined action of chloride salt erosion with 3.5% NaCl solution and freeze-thaw cycles (referred to as salty F-T cycles) has been carried out. In this study, the volume of the natural coarse aggregates has been replaced by recycled coarse aggregates (RCA) at replacement rates of 0%, 30%, 50%, 70%, and 100%. The results show that thermal insulation aggregate glazed hollow beads (GHBs) had a positive effect on the durability of concrete and RCA had an enormous negative influence on the durability of RATIC exposed to the salty F-T cycles. After 100 salty F-T cycles, the relative dynamic modulus of the elasticity of samples with RCA was below 60% compared to at the start of the F-T cycles. RCA has a significant effect on the chloride permeability of RATIC compared to natural aggregates. This phenomenon was caused by the special multi-interfaces structure of RATIC that are the result of the old interfacial translation zones (ITZs). These aggravate frost damage and negatively affect the durability of concrete in the salty F-T cycles environment.

Encapsulation of glucose oxidase in alginate hollow beads to reduce the fermentable sugars in simulated musts

The treatment of must with glucose oxidase (GOX) is a biotechnological alternative to the production of reduced-alcohol wines. Nevertheless, the low pH of must is a limiting factor for the enzyme's activity. This study reports on a simple immobilization method that uses enzyme encapsulation to overcome that limiting factor. The encapsulation of GOX was acceptably optimized using response surface methodology (RSM). An immobilization yield of 73% was obtained with 22 g L−1 Na-alginate, 20 g L−1 carboxymethylcellulose, and 12 g L−1 CaCl2. The apparent Km value of the immobilized GOX (4.55 mM) was slightly higher than that of the soluble enzyme (3.99 mM) and the activation energy was similar (~ 35 kJ mol−1). The encapsulated enzyme maintained about 68% and 92% of its initial activity at pH 3.0 and 4.0, respectively. Moreover, GOX-loaded alginate hollow beads could be re-used with 7 reaction cycles in model must, with a final reaction efficacy of 37%. GOX was successfully encapsulated in Ca-alginate hollow beads, and their catalytic potential remained unaffected by the immobilization process. In view of these results and the activity of the immobilized enzyme at the acidic pH of the must, this encapsulated biocatalyst is a promising alternative for industrial use in the production of reduced-alcohol wines.

Critical impeller speeds for a gas-inducing stirring tank loaded with solid particles

Abstract The influence of solid particles size, density and loading on the critical gas-inducing impeller speed was investigated in a gas–liquid–solid stirring tank equipped with a hollow Rushton impeller. Three types of solid particles, hollow glass beads with diameters of 300 μm, 200 μm, 100 μm, and 60 μm, silica gel and desalting resin, were used. It was found that the adding solid particles would change the critical impeller speed. For hollow glass beads and silica gel, whose relative densities were less than or equal to 1.5, the critical impeller speeds increased with the solid loading before reaching the maximum values, and then decreased to a value even lower than that without added solids. The size of the solids also had apparent influence on the critical impeller speed, and larger solid particles correspond to a smaller critical impeller speed. The experimental data also showed that the gas-inducing was beneficial to the suspension of the solid particles.

Shear behavior of reinforced glazed hollow bead insulation concrete beams

The application of glazed hollow bead insulation concrete can improve the seismic performance of the structure, simultaneously ensuring characteristics such as structural durability, fire resistance, thermal insulation, antifreezing, and impermeability. However, with change in material’s physical and mechanical properties, the shear resistance of vitrified microbead thermal insulation concrete members should be paid attention to. The literature search reveals only a few studies on the shear resistance of glazed hollow bead insulation concrete members. In this study, 14 glazed hollow bead insulation concrete beams and four ordinary concrete beams with C35 strength grade were tested. The mechanical failure process, failure form, failure mechanism, and the difference between vitrified microbead insulated concrete beam and ordinary concrete beam were compared. The effects of shear span ratio, hoop ratio and reinforcement ratio on the cracking load, ultimate load and failure mode were investigated. Combined with the “truss-arch” model, the shear bearing capacity of steel bar and concrete is described, and after considering the softening coefficient of glass microbead insulation concrete, based on the “truss-arch” model, a formula for calculating the shear capacity of inclined section of vitrified microbead insulated concrete beam was obtained. The results show that the shear failure test results of glazed hollow bead insulation concrete beams are similar to those of ordinary concrete beams; the shear bearing capacity of vitrified microbeads thermal insulation concrete beams is ∼13% higher than that of ordinary concrete beams under the same conditions, and stiffness degradation is slow in the later stage. After the constitutive relation and softening coefficient are modified, the “truss-arch” calculation model can be used to calculate the shear capacity of vitrified microbead insulated concrete beams, and the results are in good agreement with the experimental results. The study of the shear behavior of glazed hollow bead insulation concrete beams can provide data and technical basis for engineering application and has important theoretical significance and practical value to further understand the characteristics of this type of concrete structure, guiding engineering design, and promoting engineering application.

One-step preparation of molecularly imprinted hollow beads for pseudohypericin separation from Hypericum perforatum L. extracts

In the attempt to separate pseudohypericin (PH) from Hypericum Perforatum L. (or Saint John’s Wort, SJW) phyto-extracts, molecularly imprinted polymers (MIPs) hollow beads were prepared by one-step suspension polymerisation procedures and reported herein for the first time. The main reason for preparing such hollow materials refers to enhancing the accessibility of pH to the recognition sites that further leads to selective and high rebinding yields. In this respect, various terpolymer matrixes based on methacrylic acid (MAA), acrylonitrile (AN) and ethylene glycol dimethacrylate (EDMA) were tested for the ability to form micron-sized hollow beads. Morpho-structural analyses of resulted MIP beads confirmed their hollow structure. Evaluating the influence of different parameters like solvent, pH and concentration of the feed SJW extract, upon recognition and re-binding ability of MIPs for various naphtodianthrones (NTs) from SJW phyto-extracts, reflected that the optimum rebinding concentration, specificity and selectivity for PH can be atributed to the MIP systems with 50:50 and 100:0 (wt./wt.) of MAA:AN.

Comparison of seismic performance between thermal insulation concrete and normal concrete shear walls

Abstract Thermal insulation concrete (TIC) with glazed hollow beads (GHBs) is a new type of building materials meeting the needs of energy-saving building. The TIC is advantageous in applications due to its excellent bearing capacity and thermal insulation properties. This paper discusses the seismic performance of the shear wall with TIC. Based on the seismic tests of two specimens under low frequency cyclic horizontal loads with constant vertical actions, the hysteretic behavior, energy dissipation capacity, stiffness degradation and failure pattern of the shear wall were investigated. A finite element model was developed and nonlinear analyses were made to simulate the quasi-static test of the shear wall using ABAQUS software. Both modal and time-history analyses of a test building with TIC were also performed using SAP2000 software. The test results show that, compared with the normal concrete shear wall (SW), the shear wall with TIC (specimens named GSW) has better energy dissipation capacity and ductility, while the failure pattern is similar.

Effect of fly ash on drying shrinkage of thermal insulation mortar with glazed hollow beads

Drying shrinkage of thermal insulation mortar with glazed hollow beads was measured by a vertical length comparator, and the influences of fly ash with different contents (0, 18%, 36%, and 54% were used) on the long-term drying shrinkage were discussed. The mass loss was measured by the weighting method and the pore structure was characterized using three different methods, including the light microscopy, the mercury intrusion porosimetry (MIP), and the nitrogen adsorption/desorption (NAD) experiments, and the correlations among them were researched. The results show that drying shrinkage process of thermal insulation mortar includes three steps with increasing curing time: the acceleration period (before 7 d), the deceleration period (7-365 d), and the metastable period (after 365 d). Drying shrinkage in the first stage (7 d before) increases quickly owing to the fast water loss, and its development in the last two stages is attributed to the increment of the pore volume of mortar with the radius below 50 nm, especially the increment of the pore volume fraction of the pore radius within the size range between 7.3 nm and 12.3 nm. There is no change in the drying shrinkage development trend of mortar with fly ash addition, and three steps in the service life, but fly ash addition in the mortar restrains its value. There is a linear relationship between the drying shrinkage and fly ash content, which means that drying shrinkage reduces with fly ash addition.

Wave propagation in a strongly nonlinear locally resonant granular crystal

In this work, we study the wave propagation in a recently proposed acoustic structure, the locally resonant granular crystal. This structure is composed of a one-dimensional granular crystal of hollow spherical particles in contact, containing linear resonators. The relevant model is presented and examined through a combination of analytical approximations (based on ODE and nonlinear map analysis) and of numerical results. The generic dynamics of the system involves a degradation of the well-known traveling pulse of the standard Hertzian chain of elastic beads. Nevertheless, the present system is richer, in that as the primary pulse decays, secondary ones emerge and eventually interfere with it creating modulated wavetrains. Remarkably, upon suitable choices of parameters, this interference “distills” a weakly nonlocal solitary wave (a “nanopteron”). This motivates the consideration of such nonlinear structures through a separate Fourier space technique, whose results suggest the existence of such entities not only with a single-side tail, but also with periodic tails on both ends. These tails are found to oscillate with the intrinsic oscillation frequency of the out-of-phase motion between the outer hollow bead and its internal linear attachment.

Briefly Talk about the Acceptability Control of Thermal Insulation Glazed Hollow Bead Mortar of High Building External Wall

Abstract: Thermal insulation glazed hollow bead mortar is a new type of non-toxic green inorganic materials with the advantages of excellent sound absorption, low combustion performance,good air permeability, high temperature resistance, water resistance and frost resistance,low shrinkage, no cracks in the construction and no thermal bridge formation.The stability is very good in using, which greatly improves insulation effect of exterior wall and then improve the living environment. Thus the energy can be saved efficiently, which can be in line with the requirements of sustainable development and green building. This paper analyzes the acceptability control of thermal insulation glazed hollow bead mortar of high building external wall and hopes it can provide practical reference to further specific work.

Research on the Influence of Additive Quantity on Properties of Silica Aerogels/Glazed Hollow Beads Composite Thermal-insulating Mortar

The effects of the content of fly ash, redispersible latex powder and methyl cellulose on the properties of thermal insulation mortar were studied. The results showed that the incorporation of fly ash was beneficial to the mechanical properties and pore structure of hardened paste; redispersible emulsion powder improved the workability of thermal insulation mortar, and enhanced the bonding force between inorganic cementitious material and lightweight aggregate; methyl cellulose significantly reduced the dry density of thermal insulation mortar.

Rheological Characterization of Suspension of Hollow Glass Beads

Summary Hollow glass spheres (beads) are widely used as density and rheological modifiers for various oil and gas process fluids, particularly cement. One of the primary uses is to achieve lightweight slurries with good mechanical properties of the set cement. This paper discusses a concentrated, yet pumpable, suspension of these spheres for offshore cementing applications. Providing the lightweight spheres in a liquid suspension eliminates the risks associated with dry blending these materials. The development of the liquid suspension of hollow beads enables on-the-fly mixing of cement slurries with desired density profiles. Currently, the beads are premixed in the cement powder before they are shipped to offshore locations, which could result in the segregation of the beads during delivery and storage, and limits operations to the predetermined density (concentration of beads) of the slurry. This paper presents the rheological behavior of the concentrated suspension (up to 60% vol/vol) of hollow glass spheres suspended in a dilute aqueous solution of bentonite and soda ash. In addition, an attachment to the viscometer (called Fann Yield Stress Adaptor or FYSA) was used to characterize the flow behavior. A rheological model was developed to highlight the bead/bead surface interactions as a major component controlling flow behavior. Four different variants of beads were studied. These were selected to represent a range in surface area per unit volume of beads. Increasing the concentration of beads or the bentonite in solution correlated to increased yield stress and fluid viscosity at operational shear rates. In addition, a Krieger-Dougherty-type relation captured well the effect of the bead concentration, with the maximum packing fraction of beads as a function of surface area per unit volume of the beads. Overall, the Herschel-Bulkley (HB) model best described the suspension rheology with the shear-thinning exponent in the range of ≈0.8 to 1.0. Surface area of the beads linearly correlated to the yield stress of the corresponding concentrated bead solution. Results of this study and the model developed can be used to develop variants of the system with minimal experimentation, thus significantly shortening the design time.

Highly anisotropic Cu oblate ellipsoids incorporated polymer composites with excellent performance for broadband electromagnetic interference shielding

In this study, highly anisotropic Cu oblate ellipsoids incorporated polymer composites were prepared that revealed excellent broadband electromagnetic shielding effectiveness of 80.0 to 62.1 dB at a frequency region between 300.0 KHz and 12.0 GHz, at low Cu contents. Cu-coated hollow polymer beads were fabricated through electroless plating of Cu on the polymer hollow beads. The hollow polymer beads were prepared through thermal expansion of acrylonitrile-based polymer beads containing a blowing agent. These beads were capable of incorporating highly anisotropic 2-dimensional (2D) Cu oblate ellipsoids into polymer composite through simple compression molding process. The resulting broadband electromagnetic shielding performance attributes to a low percolation behavior of the composites due to high anisotropy of the conductive Cu filler and their multilayered structure in the composites.

A Novel Application of Expanded Glass Materials in Sulfate Reducing Bacteria Cultivation

Smelting waste water is typically considered as an environmental pollutant. It will contaminate watercourses, crops and aquatic organism when it is discharged into the environment. Traditionally, the metallurgy plant treats this kind of waste water with neutralization method. However, the neutralization method usually ends up with large amounts of neutralization sludge which is a typical kind of hazardous solid waste. In our research, we used an up-flow anaerobic sludge bed to treat smelting waste water which was neutralized to a certain pH. We combined the traditional neutralization method with microbial technique. The neutralized water was pumped into the bioreactor that had been inoculated with sulfite reducing bacteria on a novel expanded hollow glass bead. In our research, we decreased the lime consume and sludge production, and we decrease the metal ion and sulfate in the smelting waste water at the same time. We combined the traditional neutralization method with microbial treatment and developed a novel solution to deal with smelting waste water. After 8 weeks, the concentration of Zn2+ was decreased by 34.7%, and the concentration of SO42- was decreased by 58.3%.

Mechanical and thermal properties of glass fibre-reinforced ceramsite-foamed concrete

This study investigated the mechanical and thermal properties of glass fibre-reinforced ceramsite-foamed concrete with a volume of entrained air generated by hydrogen peroxide. The effects of hydrogen peroxide content, glass fibre content, glazed hollow bead content and ceramsite content on the compressive strength, splitting tensile strength and thermal conductivity were investigated. The results indicated that with the addition of hydrogen peroxide and an increase in glazed hollow bead and ceramsite content, there was a significant increase in the brittleness of foamed concrete. Glass fibre can obviously improve the splitting tensile strength and reduce the thermal conductivity of foamed concrete. In addition, an empirical compressive strength formula of glass fibre-reinforced ceramsite-foamed concrete was recommended.

Calculation on effective thermal conductivity of recycled aggregate thermal insulation concrete with added glazed hollow beads

Abstract In this paper, available structural models and equations for predicting the effective thermal conductivity (ke) of recycled aggregate thermal insulation concrete, including series, parallel, Maxwell-Eucken, eEffective medium theory, and Gong's model are discussed and extended to three phases by considering the effect of glazed hollow beads (GHBs). The solid porosity of GHBs is estimated and used in the equations. A unified model for calculating ke values is proposed, where the fractal dimension of GHBs is considered. A simple expression characterizing the fractal dimension of GHBs is derived. Nine batch specimens with different concrete mixtures are tested to determine the ke values which are compared with the predicted values. The predicted values from Unified-2 model are found to be in good agreement with the experimental results.