Expanded Perlite Particles Research Articles

Statistical and experimental study on microcrack of mortar by a self-healing agent of bacteria adsorbed by expanded perlite

PurposeThe purpose of this paper is to add expanded perlite (EP) immobilized microorganisms that replace part of the standard sand in mortar to improve the self-healing ability of mortar cracks and reduce the water absorption of mortar after healing.Design/methodology/approachBacillus pseudofirmus spores were immobilized with EP particles as self-healing agents. The effects of adding self-healing agents on the compressive strength of mortar specimens were observed. The ability of mortar specimens to heal cracks was evaluated using crack microscopic observation and water absorption experiments. The filler at the cracks was microscopically analyzed by scanning electron microscope and X-ray diffraction experiments.FindingsFirst, the internal curing effect of EP promotes the hydration of cement in mortar, which generates more amount and denser crystal structure of Ca(OH)2 at mortar cracks and improves the self-healing ability of mortar. Second, the self-healing ability of mortar improves with the increase of self-healing agent admixture. Adding a self-healing agent of high admixture makes the planar undulation of calcite crystal accumulation at mortar cracks more significant. Finally, the initial crack widths that can be completely healed by adding EP and self-healing agents to the mortar are 200 µm and 600 µm, respectively.Originality/valueThe innovation points of this study are as follows. (1) The mechanism of the internal curing effect of EP particles on the self-healing ability of mortar cracks was revealed by crack microscopic observation tests and microscopic experiments. (2) The effect of different self-healing agent amounts on the self-healing ability of mortar cracks has been studied. (3) The effects of EP particles and self-healing agents on healing different initial widths were elucidated by crack microscopic observation tests.Graphical abstract

The effects of particle sizes of expanded perlite on the mechanical properties and chloride penetration resistance of ECCs

This study presents the development of engineered cementitious composites (ECCs) incorporating expanded perlite particles (EPPs) with varying sizes, namely 150 mesh, 50–70 mesh, and 5–15 mesh, as well as an equivalent combination of these three sizes. The primary focus of the investigation was to evaluate the microstructures at different ages, mechanical properties, and chloride penetration resistance of ECCs incorporating EPPs. The results showed the presence of a compact interfacial transition zone (ITZ) between the matrix and EPPs, attributable to the internal curing effect. The incorporation of EPPs effectively mitigated fiber damage during fiber-matrix separation, thereby preventing premature fiber rupture. Specifically, the inclusion of 150 mesh EPP demonstrated improved mechanical properties compared to the control group. Furthermore, the addition of 5–15 mesh or mixed EPP enhanced the chloride penetration resistance of ECC, while contrasting results were observed for 150 mesh and 50–70 mesh EPPs. Additionally, this study explored the use of 150 mesh recycled rubber (RR) as an additional defect. ECCs with simultaneous incorporation of RR and EPPs (at a 2% content) exhibited excellent ductility, with an overall tensile strain ranging from 4.3% to 4.7%. The results for the combined addition of RR and EPPs aligned with those observed for the singular addition of EPPs in terms of chloride penetration resistance.

Influence of Melt Infiltration Parameters on Structural and Mechanical Properties of Al-4.3wt.%Cu-EP Syntactic Foam

The present research concerns fabrication of Al-4.3wt.%Cu metal syntactic foams using expanded perlite particles (EPPs). A gas pressure infiltration technique was employed to fabricate the aluminium syntactic foams under different infiltration temperatures and pressures. Ambient air pressure and 750 °C were identified as the favoured processing conditions for full infiltration of the melt. The average density and EP volume percentage of the fabricated foams were measured to be about 1.55 g/cm3 and 50.3%, respectively. Melt infiltration is believed to be mainly controlled by the breakage of the aluminium oxide layer on the melt surface and melt viscosity. Preferential infiltration of the melt between the mould wall and the EP particles bed complemented by radial melt infiltration toward the centre of the samples was identified. The effects of EP particles on growth of the nucleated primary α-aluminium phase were discussed. XRD and EDS analyses suggested some chemical reactions at the interface of EPPs with the molten aluminium. T6 heat treatment in the ambient atmosphere improved the average compressive tensile strength, plateau stress, and absorption capacity of the syntactic foams by more than 100%. Uniform deformation and similar densification strains (about 40%) of the as-fabricated and heat-treated syntactic foams during the compression test suggested uniform distribution of EP particles and metallic struts in the aluminium alloy matrix.

Effect of jute fiber reinforcement on the mechanical properties of expanded perlite particles-filled gypsum composites

In this work, jute fiber reinforced gypsum composites (JRGCs) and unreinforced gypsum composites (URGCs) using varying amounts of expanded perlite particles as filler were manufactured to investigate the effects of perlite content and fiber reinforcement on the mechanical properties of the composites. The prepared composites were characterized for density, compressive properties, flexural properties, and failure behaviour during both compression and flexural tests. The incorporation of perlite and jute fibers in gypsum showed both positive and negative impacts on the mechanical properties. The addition of expanded perlite in pure gypsum improved the density, specific compressive strength, compressive modulus, and compressive toughness. The flexural modulus and toughness were enhanced remarkably for both JRGCs and URGCs due to the addition of perlite although the flexural strength was decreased. The compressive and flexural toughness were increased by 140.73 % and 3608.03 % respectively due to 2.44 % jute fiber reinforcement in the pure gypsum although the compressive and flexural strength were decreased by 12.79 % and 13.94 % respectively. The failure mechanisms during compression and flexural tests were positively changed and the crack propagation after failure initiation was successfully arrested by jute fiber reinforcement.

Water Retention Characteristics of Various Sizes of Expanded Perlite Produced from Two Different Types of Rocks

This study presents the results of the water retention characteristics of six groups (0.25 mm to 8.35 mm) of expanded perlite (EP) produced from two crushed raw perlite rocks of Turkey (A) and China (B). The particle size proportions of EPs showed that the particle size less than 1.68 mm was higher in B than that of A and the particle size distribution curves (PSDC) of three samples of EP A and B were similar, while the percent finer value (DN) of B was higher than that of A in all corresponding particle sizes. Volumetric water content (θv) for EPs of A and B were obtained at 11 levels of matric potentials between 0 to −50 kPa (sandbox with kaolin-plate) and −50 to −1500 kPa (pressure chamber), respectively, after fully saturating the uniformly packed EP in open-ended metal round rings. The results showed that the shapes of measured WRCs and particle size distribution curves of EP A and B were similar, while the percent values of PSDC were higher than those values of θv corresponding to each water potential greater than 0.1 kPa. The WRCs of respective EP showed that a substantial decline started at about −1 kPa and approached the residual water content (θr) observed at −500 kPa for all measurements. θv for all particle sizes of the EP A and B was not only decreased with the increasing matric potential but also distinctive with increasing particle size greater than 2.36 mm. θr was increased with decreasing particle size. For these results, we assumed that θv of the different particle sizes of EP A and B could be determined by actual pore volume excluding occluded pore volume depending on size and surface area in the EP particles.

Statistical and experimental investigation on self-healing of microcracks in cement mortar by encapsulation of calcite precipitating bacteria into expanded perlite

Healing of micro cracks in concrete using calcite precipitating microorganisms has become an interesting research for the past two decades. In this study, an attempt was made to encapsulate strong and efficient calcite precipitating spore-forming bacteria named Bacillus megaterium MTCC 8510. The encapsulation and survival of bacteria in expanded perlite was made successfully by dual coating using sodium silicate and cement. The mechanical properties and healing efficiency of the coated expanded perlite were tested after it was integrated into the cement mortar matrix. The encapsulated bacterial expanded perlite particles were added into cement mortar in 10%, 15%, 20%, and 25% replacement of fine aggregate. The results of 20% replacement of fine aggregate by expanded perlite showed an improvement in healing of microcracks of size varying from 0.154 mm to 0.626 mm. But due to the presence of expanded perlite, there was a decrease in compressive strength. To counteract the reduction in strength 5% of nano-silica was added along with cement, which had given improvement in compressive strength of mortar without compromising in healing. The improvement in healing was observed visually by width repair rate method and the healing in the depth of cracks was determined by Ultrasonic Pulse Velocity (UPV) test method. The crystal shapes and elemental analysis of calcite precipitation were observed using FESEM, and confirmed using XRD analysis. The regression equations were developed for each test procedure by considering the factors which influence the compressive strength and healing efficacy. Statistical model using ANOVA was employed to find the significance of factors and the optimum percentage of expanded perlite replacement. With a p-value of less than 0.05, the factors proved to be significant. A high R2 value nearing 100 percent and acceptable precision was used to determine the model’s predictive efficiency. The model has shown that 20 percentage replacement of fine aggregate by expanded perlite is optimum for healing efficacy without compromising the compressive strength.

Mechanical and Energy Absorption Performance of Expanded Perlite Foam-filled Steel Tubes

The main objective of this research is to manufacture expanded perlite (EP) foam-filled stainless steel tubes for energy absorption application and to investigate their physical and compressive behavior. Foam-filled steel tubes (FFT) were manufactured by consolidating expanded perlite/sodium silicate composite foam inside the tube. The EP particles of size 5-6 mm were taken for manufacturing FFTs. Two different sodium silicate solution to water (S/W) ratios and three compaction ratios (CR) were the manufacturing parameters of the foams. The manufactured FFTs were characterized for density, yield stress, plateau stress, energy absorption, and energy absorption efficiency. The compression test results showed that the foam filling improved the compressive properties and energy absorption ability of the steel tube significantly. The failure analysis along with the stress-strain curves was also conducted. The change in failure mechanism is found to be the reason for high energy absorption and energy absorption efficiency for high-density foam-filled tubes.

Investigation on Thermal Insulation and Mechanical Strength of Lightweight Aggregate Concrete and Porous Mortar in Cold Regions

Thermal insulation is an important indicator to evaluate the construction material in cold region engineering. As we know, adding the industrial waste as lightweight aggregate or creating the pore inside the cement-based composite could make the texture loose, and the thermal insulating capacity of the material would be improved with this texture. Using these methods, the industrial by-product and engineering waste could be cycled in an efficient way. Moreover, after service the fragmented cement composites paste could be used as aggregate in the thermal insulating concrete again. While the porous texture is not favorable for the mechanical strength and long-term durability in a cold environment. To balance the above three requirements from two opposite directions, different processing methods were applied to create the thermal insulation concrete/mortar. Firstly, the organic/inorganic lightweight aggregate, including the Expanded Polystyrene (EPS), Expanded Perlite (EP), and Ceramsite (CRMST) particles, were applied to create the Lightweight Aggregate Concrete (LWAC). As the comparative tests, the expanded Superabsorbent Polymer (SAP) hydrogel and Air-Entraining Agent (AEA) were also introduced to create the porous mortar. The above concrete/mortar was tested in the normal state and under the Freeze-Thaw cycle to explore the engineering performance in cold regions. During the experimenting process, the thermal insulation, mechanical strength, and frost resistance of these cement-based composites were investigated, and an optimal thermal insulation concrete/mortar was determined.

Core-Shell structured ceramsite made by excavated soil and expanded perlite through cold-bonded technology

A large amount of excavated soil (ES) is generated in subway construction. Improper stacking will bring a serious threat to the environment and human safety. To recycle this excavated soil, the method of the cold bonding granulation technique was adopted to prepare core–shell structured ceramsite, which had an ES coating of expanded perlite particles. The effects of the cement content and the curing method on the pore structure, water absorption, and mechanical properties of the ceramsite were analyzed. Scanning electron microscopy (SEM) was employed to investigate the microstructure of the ceramsite. In addition, X-ray micro-computed tomography (XCT) was used to explore the internal core–shell structure of the ceramsite. The results revealed that ceramsite with a water absorption of 26%–55% and a single particle crushing strength of 7.48–22.12 N could be achieved. This core–shell structured ceramsite could potentially be used as water-retaining materials to be applied in landscaping and agriculture.

Investigation of mechanical and tribological behaviour of expanded perlite particle reinforced polyphenylene sulphide

In this study, polyphenylene sulphide was used as a matrix material due to its superior engineering properties. Expanded perlite is formed substantially from silica oxides, and it is a volcanic based and porous structure material. Its low price and low density make it very usable as a filler material. For this reason, expanded perlite reinforced polyphenylene sulphide matrix composites were prepared at various weight ratios (0, 1, 3, 5, and 10 wt%). Mechanical and tribological characterizations were done with tensile tests, hardness measurements, solid particle erosion, ball on disc, and scratch tests. According to the tensile test results, a synergistic effect was observed in mechanical properties by using perlite as a reinforcing agent. As expected, perlite reinforcement resulted in an increase in the modulus of 54% in composites. As well as tensile strength of the composite increased by approximately 13%. Furthermore, the perlite particle reinforcement improved the adhesion resistance by 73% and the scratch resistance by 30%. On the other hand, especially at low impact angles, perlite particle reinforcement decreased the erosive wear resistance of the pure polyphenylene sulphide polymer by 50%. Furthermore, expanded perlite reinforcement decreased the plastic deformation ability of polyphenylene sulphide. In consequence of this study, it has been found that expanded perlite particles can be used as an alternative filler instead of conventional reinforcing particles.

A green rust-coated expanded perlite particle electrode-based adsorption coupling with the three-dimensional electrokinetics that enhances hexavalent chromium removal

A green rust-coated expanded perlite (GR-coated Exp-p) microelectrode was synthesized and incorporated into a column-mode three-dimensional electrokinetic (3D-EK) platform to effectively pursue a continuous Cr(VI) removal from the aqueous solution. Brucite-like layers of GR were decorated onto the Exp-p material. The molar ratio of Fe(II) to Fe(III) played a most vital role among the three synthesis factors in influencing the performance of the particle electrode. For the equilibrium adsorption experiments, the target maximum adsorption capacity of 122 mg/g was predicted by a target optimizer and desirability function at the conditions following the pH of 4.7, the initial concentration of 172.4 mg/L, the dosage of 0.28 g/L, and the temperature of 28.96 °C, respectively. SO42−, Cl−, and NO3− fiercely competed with Cr(VI) anions in the acidic conditions for the locally positive sites. A low concentration and a slow flow were favored in the column-mode 3D-EK platform. The pseudo-first-order and Langmuir models were suitable for describing the kinetics and isotherms of the adsorption process, respectively. Cr(VI) anions were electrostatically attracted to the silanol groups and GR surface of the adsorbent, subsequently reduced in both heterogeneity and homogeneity, and finally immobilized by coordinating with silanediol groups and silanetriol groups.

Development of Sustainable Lightweight Concrete Using C old-Bonded Lightweight Aggregates.(Dept.A)

lightweight concrete (LWC) can be considered as a structural material with unique characteristics such as reduced thermal insulation and low density. However, it consumes huge amount of artificial lightweight aggregates (LWA). Artificial LWA can be manufactured using sintering method or cold-bonded technique. Spite sintering method is more common due to low density of the produced LWA with appropriate mechanical characteristics, it has some economic and environmental drawbacks. Contrarily, cold-bonded technique has environmental and economic benefits due to potential lower energy consumption compared to sintering method. Nevertheless, its application still limited due to low mechanical properties as well as high density of the produced aggregate. This research presents a new method of producing sustainable core-shell artificial lightweight aggregate by using cold-bonded method. To minimize the aggregate density, expanded perlite particles with very low density was encapsulated in a cover layer made of powdered perlite, fly ash and cement. To improve mechanical characteristics of the produced aggregates, surface treatment using a mixture of microsilica and cement was applied. To compare the performance with sintered aggregates (expanded clay), several LWC mixes were prepared and tested. Mechanical properties, thermal conductivity as well as durability of LWC were measured. Scanning Electron Microscopy measurements were conducted to examine aggregate-cement matrix transition zone. The experimental results revealed that the performance of cold-bonded LWA is comparable with sintered LWA. Moreover, LWA with dry density in the range of 1200-1500 kg/m³ and compressive strength of 18-25 MPa was developed using cold-bonded LWA

Sugar-coated expanded perlite as a bacterial carrier for crack-healing concrete applications

Microbial-induced carbonate precipitation (MICP) can realize self-diagnosis and self-healing of concrete to reduce the maintenance costs and extend the lifetime of concrete structures. However, the self-healing capacity of the cracks is below par using existing self-healing methods. Thus, adopting the sugar-coating method to immobilize bacteria and nutrients was proposed in this paper. The effect of expanded perlite (EP) wrapped with various materials as bacterial carrier and nutrient carrier on the crack-healing capacity of concrete has been investigated. The results indicated that after EP particles were coated, the numerical tube pressure was increased, and the water absorption was reduced. Wrapping materials can effectively reduce the breakage rate of the EP particles and resist the invasion of water in the process of mixing with concrete. The EP particles after wrapping process were found to enhance the healing capacity of concrete cracks. In particular, the crack-healing of concrete peaked when EP particles immobilized with bacterial spores were wrapped with a low-alkaline material (potassium magnesium phosphate cement). This result was also validated by the water permeability experiments. After 28 d of crack-healing, the maximum value of the completely healed crack width was 1.24 mm. EP is a low-cost material; thus, it can be used as a bacterial carrier for large-scale self-healing concrete applications.

Properties of lightweight concrete made with core-shell structured lightweight aggregate

In this study, core-shell structured lightweight aggregates (CSA) were produced through the cold bonding method, by encapsulating an expanded perlite particle (as a core structure) within a shell matrix composed of cement, fly ash and expanded perlite powder. The effect of different curing regimes on the mechanical and microstructural properties of the CSA were studied. To enhance the characteristics of the aggregates produced, they were surface treated by a mixture of cement and silica fume, using two different treatment methods. Afterwards, the properties of lightweight concrete made of either CSA or expanded clay aggregate (ECA) were compared closely in terms of their potential economic and environmental benefits, in response to the high energy consumption associated with the production of ECA. The results revealed that curing at a relative humidity of 99% is the most appropriate curing method for CSA. In addition, treating the CSA surface contributes significantly to enhancing its bulk crushing strength, by about 14–18%. The findings also demonstrate the feasibility of using CSA to produce lightweight aggregate concrete, with a dry density and compressive strength ranging from 1115 to 1540 kg/m3 and from 17.9 to 25.8 MPa, respectively, with a corresponding thermal conductivity range of 0.3169–0.6660 W/m·K.

MECHANICAL PROPERTIES OF THE COMPOSITE MATERIAL PRODUCED BY THE MIXTURE OF EXPANDED PERLITE, WASTE MARBLE DUST AND TRAGACANTH

In this study, the strength characteristics of the expanded perlite aggregate, waste marble dust and tragacanth added cement based composite material were investigated. A composite construction material was prepared using expanded perlite aggregate with a particle size of 0-2 mm and 2-4 mm at the ratio of 10%, 30% and 50% by weight, waste marble powder produced by sieving through 0.25 mm sieve at the ratio of 10% and 20%, tragacanth at the ratio of 0%, 0.5% and %1 and CEMI 42.5 N type Portland cement. Density, compressive strength, abrasion loss, water absorption, compressive strength after elevated temperature and compressive strength after freezing-thawing tests were performed on these prepared composite samples. It was seen that compressive strength, compressive strength after elevated temperature, compressive strength after freezing-thawing and density values have decreased and abrasion loss and water absorption values have increased as expanded perlite particle size, expanded perlite ratio, tragacanth ratio have increased and waste marble powder ratio has decreased on the prepared samples .

Long-term immersion exposure of perlite–aluminium syntactic foam in seawater

Perlite–metal syntactic foam is a novel lightweight material with good specific strength and excellent energy absorption capabilities. To analyse its suitability in marine applications, perlite–metal syntactic foam has been immersed for 2 years in natural flowing seawater. The change of mass and mechanical properties has been studied as a function of exposure time. Results indicate a slow degradation of mechanical properties that can be attributed to a change of the macroscopic deformation mechanism. Interestingly, no evidence of significant corrosion was observed. Instead, the change in mechanical properties is triggered by the sedimentation of oxides and sulphates within the expanded perlite particles. Implications towards the long-term viability of such perlite–metal syntactic foam in marine applications are discussed.

Performance assessment of core-shell structured lightweight aggregate produced by cold bonding pelletization process

The density of cold-bonded lightweight aggregates is significantly higher than that of sintered lightweight aggregates. Since the sintering technique consumes an enormous amount of energy and emits a huge amount of pollutants, the implementation of a cold-bonded method, in manufacturing low-density lightweight aggregates, is very important from an economic and environmental perspective. In this study, a cold bonding granulation technique was employed to produce low-density lightweight aggregate by the encapsulation of expanded perlite particles in shell structures. A variety of tests were conducted to evaluate the physical and mechanical properties of the aggregate produced. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to study the microstructure and the phase composition of the aggregate. Furthermore, X-ray micro-computed tomography (CT) was performed to investigate the pore system of the aggregate specimens. The obtained results showed that by adopting the angle and speed of pelletizer disc, a core-shell structured lightweight aggregates with particle density of 0.88–1.14 g/cm3 and bulk crushing strength of 2.04–2.66 MPa can be produced.

Improvement of wetting properties of expanded perlite particles by an organic conformal coating

Expanded perlite particles were surface functionalized using poly(hydroxyethyl methacrylate) (PHEMA) thin film under radio frequency (RF) plasma conditions in a rotating-bed plasma enhanced chemical vapor deposition (PECVD) system. Using a rotating-bed system allowed effective agitation and mixing of the particles during depositions, which ensure uniform surface coating of highly porous and particulate materials. The effects of plasma power and plasma operation mode, namely pulsed and continuous modes on the deposition rates, structure, wettability and water holding capacities of expanded perlite particles were investigated. Chemical and morphological properties of uncoated and coated expanded perlites were determined by SEM, FTIR, contact angle, and BET analyses. Observed deposition rates changed between 10 and 35 nm/min., which were dependent on the deposition conditions. It was found that pulsing the discharge helped to minimize undesirable monomer fragmentation while providing better film structure. The most hydrophilic PHEMA thin films were fabricated at 50 W plasma power and under pulsed-plasma mode. When the expanded perlite was modified with PHEMA under suitable experimental conditions, the water holding capacity of untreated particles is increased by more than twenty percent.

Electrorheological response of mesoporous expanded perlite particles

In this study, chemical composition, structural and physical properties of expanded perlite (EP) were determined by particle size, apparent density, SEM-EDS and XRD measurements. Electrorheological (ER) properties of EP particles dispersed in silicone oil (SO) were fully investigated as a novel dry-based ER fluid. Thus, ER response of EP/SO dispersions was revealed as a function of electric field strength (E), volume fraction, shear rate, shear stress, frequency and temperature. As a result, the EP/SO ER fluid was observed to sensitive to external E, exhibiting a typical shear thinning non-Newtonian viscoelastic behavior. The correlation between the yield stress (τy) and E was deviated from polarization model (m < 2). Further, antisedimentation stabilities of the mesoporous EP particles in SO medium were determined to be perfectly suitable for potential ER applications under various temperatures.

Colloidal and viscoelastic properties of expanded perlite dispersions

In this study, structural properties of unexpanded perlite and expanded perlite particles were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis techniques. Electrokinetic properties of unexpanded perlite and expanded perlite particles in polar (water) and non-polar (silicone oil) media were determined using zeta ( ζ)-potential measurements as functions of time, pH, valences of electrolytes, type of surfactants, and temperature. Antisedimentation stabilities of the unexpanded perlite and expanded perlite particles dispersed in silicone oil were determined as a function of temperature at various volume fractions ( ϕ = 5%−25% v/v). Viscoelastic properties of expanded perlite particles dispersed in silicone oil were investigated by creep and creep-recovery tests under externally applied electric field strengths. As a result, the ζ-potential and antisedimentation stability values revealed that colloidal stabilities of the expanded perlite particles were high enough to be used as smart electrorheological material in long time durations. Expanded perlite/silicone oil dispersion behaved as a viscoelastic material and exhibited a reversible nonlinear viscoelastic deformation under applied electric field and showed a vibration damping capability for potential industrial applications.