Lightweight Fillers Research Articles

Novel overlapping constructed wetlands with water drops reoxygenation and lightweight fillers for decentralized wastewater treatment

Constructed wetlands (CWs), crucial for the rural decentralized wastewater treatment, have encountered limitations in nutrient removal efficiency and require extensive land area. This study has constructed a novel overlapping horizontal subsurface flow CWs (OLCWs). Remarkably, OLCWs with mixed lightweight fillers (M-OLCWs) exhibited a significant enhancement in total nitrogen (TN) removal efficiency (88–91 %) in different hydraulic loading rates compared to single filler OLCWs (48–62 %). This significant enhancement can be attributed to the lightweight fillers, which have higher abundances and diversity of nitrogen related microorganisms. The treatment dynamics revealed that the second stage exhibited an excellent TN removal efficiency (73–75 %) attributed to sufficient dissolved oxygen concentration by water drops reoxygenation. The research reveals that M-OLCWs, by utilizing water drops reoxygenation and lightweight fillers, not only enhance pollutant treatment efficiency but also reduce required land area, thereby offering a sustainable solution for rural decentralized wastewater treatment.

Lightweight, hydrostatic pressure‐resistance, thermal insulating epoxy syntactic foam with a multiscale ternary structure for marine engineering application

AbstractThe study of lightweight epoxy syntactic foams is of great significance for the exploitation of marine resources. In this work, glass fibers reinforced epoxy hollow spheres (GFs‐EHS) were first prepared using a template method, and a lightweight three‐phase epoxy syntactic foam (LWTP‐ESF) with a multiscale ternary structure was prepared using a molding pressing method with epoxy resin as matrix, hollow glass microspheres (HGMs), and GF‐EHS as the lightweight fillers. The effect of HGMs content on the density, uniaxial compression properties, water absorption, and thermal conductivity of obtained LWTP‐ESF was evaluated. The results indicated that the density, uniaxial compression strength, and thermal conductivity of LWTP‐ESF were consistently decreased, while the water absorption was increased with the increase in HGMs content. The highest specific compression strength and lowest thermal conductivity of LWTP‐ESF could reach 52.77 ± 0.82 MPa·cm3/g and 0.113 ± 0.005 W/(m·K), respectively. Moreover, the effect of hydrostatic pressure on the water absorption and thermal conductivity of LWTP‐ESF were also systematically analyzed. This study provides a novel system and method to prepare lightweight epoxy syntactic foams, and the prepared composites have potential applications in the field of lightweight thermal insulation materials for marine.Highlights The composites with a multiscale ternary structure were designed. The composites possessed significantly lower density and thermal conductivity. The water absorption of composites under hydrostatic pressure was evaluated. The thermal conductivity of composites under hydrostatic pressure was evaluated. The water absorption mechanism and thermal insulation mechanism were proposed.

Tomographic analysis of segregation behavior of hollow glass microspheres in lightweight cementitious composites

Lightweight concrete must contain lightweight aggregates that are more susceptible to segregation than traditional concrete. Concrete has increasingly used lightweight fillers but research on segregation analysis is relatively scarce. To systematically investigate the segregation of hollow glass microspheres (HGMs), lightweight cementitious composites (LWCC) with a water-to-cement (w/c) ratio of 0.25–0.5 were investigated. The 3D structure of HGMs in the LWCC was observed with micro-computed tomography (μ-CT), and a rapid CT projection analysis was proposed to evaluate the segregation. The results showed that a slight segregation tendency of HGMs was observed from 0.45, while severe floating segregation occurred at 0.5 of w/c. The flowability of the LWCC increased with the increase of the w/c ratio, but it could not anticipate the segregation behavior. Meanwhile, 2D CT projection image could quickly evaluate the segregation phenomenon so it was proposed that it can be utilized for evaluating potential segregation of cement-based materials.

Air entrance additive effect on geopolymer mortar thermal conductivity

The article deals with research on sustainable building materials - alkali-activated mortars with high temperature resistance. A cement-free alkali-activated binder [geopolymer] based on alkali-activated fly ash from coal combustion using perlite, perlite dust and cenospheres as filler. The object of the analysis was to study the effect of fillers on the coefficient of thermal conductivity, compressive strength and microstructure of the cementless mortars. The results showed that the most effective addition was perlite sand in the amount of 30%. The other tested lightweight fillers did not significantly change the thermal conductivity of the tested mortars.

Comparative assessment of the surface properties of Ukrainian ash microspheres

The object of research is ash microspheres from the burning of hard coal in Donetsk, Lviv-Volyn (Ukraine) and foreign (South Africa) basins, power plants of various regions. The chemical and mineralogical composition of Ukrainian ash microspheres was analyzed in comparison with foreign counterparts (South Africa, Great Britain, etc.), other types of microspheres (glass, ceramic) and expanded perlite. The advantages of aluminosilicate microspheres of technogenic origin (ASM) over other lightweight fillers are noted. One of the most problematic areas is the lack of an objective comparative assessment of Ukrainian ash microspheres in terms of the influence of the structure-forming bonds Si–O, Si–O–Si and Si–O–Al on the physicochemical properties and energy and reactivity of their surface. It was established that the SiO2/Al2O3 ratio in their composition is within 1.46–1.87 against 1.53–1.64 in South African ASM and 4.81–5.61 in swollen pearlites, which ensures the content of crystalline phases (mullite, quartz) from 36 wt. % in Trypil microspheres to 53 wt. % in Kurakhove microspheres. The latter have a minimal content of Si–O–Si bonds (the I0/I ratio in the 1029 cm–1 band is 1.25 versus 6.71 in Burstyn ASM). The revealed features of changes in the chemical and mineralogical composition of microspheres, as well as structure-forming bonds, are fully correlated with the content of adsorbed water and OH and CH groups in the surface layer of the latter and, as a result, the energy state and reactivity of ASM. A quantitative assessment of their wettability with water (0.32–0.106) and under the condition of tgδ (0.196–0.4490) is given. The availability of such information makes it possible to clearly classify Ukrainian ash microspheres according to the degree of efficiency of use, taking into account their advantages in the composition of composite materials on various types of binders and to assess the presence of interchangeability in the context of a special situation in Ukraine.

Properties of fly ash-based spray-applied fire resistive materials

Spray-applied fire-resistive materials (SFRMs) are one of the most commonly used passive fire protection materials due to their low thermal conductivity, lightweight, cost-effectiveness, and ease of application. Gypsum and Portland cement are commonly used in SFRMs to bind lightweight fillers and fibres. Due to the wide application of SFRMs, their production consumes large amounts of natural and non-renewable resources and contributes significantly to greenhouse gas emissions. This paper investigates the feasibility of using industrial by-products (e.g., fly ash) and waste materials (e.g., waste glass) to manufacture SFRMs with the aim of reducing the environmental impact. Accordingly, three SFRMs with different densities were developed utilising fly ash blended cement (FAC) and expanded glass. The use of FAC significantly reduced the use of Portland cement by 81% and achieved a 28-day compressive strength of 33.8–46.3 MPa for the binder. The developed SFRMs had average densities of 345 kg/m3, 560 kg/m3, and 698 kg/m3 for low-, medium-, and high-density groups, respectively. The compressive strengths of the SFRMs ranged from 747 kPa to 888 kPa, 6188 kPa to 7314 kPa, and 2343 kPa to 3535 kPa for the corresponding three groups, respectively. Additionally, the bond strengths of the corresponding SFRMs are 14.4 kPa–19.3 kPa (low-density), 34 kPa–40.9 kPa (medium-density), and 51.5 kPa–85.1 kPa (high-density), respectively. All the tested SFRMs met the requirements for density, compressive strength, bond strength, and non-combustibility. The thermal properties of the developed SFRMs were comparable to those of commercially available cementitious-based SFRMs in the same density group. In addition, using FAC instead of Portland cement could reduce carbon emissions by 68.4% and save costs by 38.4% in the Australian context.

Investigation of gypsum composites with different lightweight fillers: A physico-mechanical characterisation regarding possibilities for building applications

This paper shows the characterization of a new lightened gypsum-based material for use in buildings. Super absorbent polymer (SAP) Potassium Polyacrylate has been used as main lightener leading to a 20% density reduction. In addition, tests have been carried out with the lightened plaster material reinforced with vermiculite (VER), recycled glass wool (RGW), expanded clay (EC). A significant improvement in physical properties was achieved. After material evaluation, a new precast design was elaborated and tested for its use in building. Physical-mechanical properties of these new material have been studied. A complementary ignitability test was also conducted to set this material's suitability for its use in building. All samples performed over standard minimum requirements. Samples containing RGW obtained best results in both, thermal conductivity, and acoustic absorption.

Hollow Glass Microspheres/Montmorillonite/Epoxy Sheet Molding Compound Composites With Low Density and Excellent Mechanical Properties

Epoxy sheet molding compound (ESMC) composites have good mechanical properties, insulation performance, and corrosion resistance, and are widely used in the automotive industry. However, the density of a typical ESMC composite is high, which limits its wider application. Lightweight fillers can reduce the density of ESMC composites, but the addition of lightweight fillers can lead to a decrease in the mechanical properties of the composite. In this paper, we describe our research in which hollow glass microspheres (HGM) were utilized to decrease the density of the ESMC composites. In addition, surface modification of the HGM was performed to enhance the compatibility between the HGM and the epoxy resin (EP), thus improving the mechanical properties. Further, montmorillonite (MMT) was introduced to further improve the mechanical properties of the ESMC composites. The results showed that the density of the prepared composite was about 1.5 g/cm3, which was significantly lower than the industry standard sheet molding compound (SMC) density of 1.9 g/cm3. The flexural strength and impact strength of the resulting ESMC composites containing the modified HGM and an appropriate amount of MMT (EP/SiHGM/MMT-1) reached the maximum value of 80.0 MPa and 28.6 kJ/m2, respectively, which were 39.9 and 51.3% higher than that of the ESMC composite containing only HGM (EP/HGM/MMT-0). On the one hand, the modified HGM was well dispersed in the EP for the chemical bonding effect. On the other hand, the fiber/matrix interface was further improved after introducing an appropriate amount of MMT. Thus, the resulting ESMC composite exhibited low density and excellent mechanical properties and showed great potential for applications that require lightweight and high strength.

Experimental Study on Compressive and Flexural Performance of Lightweight Cement-Based Composites Reinforced with Hybrid Short Fibers.

This paper aims to experimentally study the compressive and flexural characteristics of cement-based composites developed for fabricating thin, lightweight, and high-performance components of buildings. Expanded hollow glass particles with a 0.25-0.5 mm particle size were used as lightweight fillers. Hybrid fibers made of amorphous metallic (AM) and nylon fibers were used to reinforce the matrix with a total volume fraction of 1.5%. The primary test parameters included the expanded glass-to-binder (EG/B) ratio, the fiber volume content ratio, and the length of the nylon fibers in the hybrid system. The experimental results demonstrate that the EG/B ratio and the volume dosage of the nylon fibers exhibited insignificant effects on the compressive strength of the composites. Additionally, the utilization of nylon fibers with a longer length of 12 mm resulted in a slight compressive strength reduction of approximately 13% compared to that of the 6 mm nylon fibers. Further, the EG/G ratio exhibited an insignificant effect on the flexural behavior of lightweight cement-based composites in terms of their initial stiffness, strength, and ductility. Meanwhile, the increasing AM fiber volume fraction in the hybrid system from 0.25% to 0.5% and 1.0% improved flexural toughness by 42.8% and 57.2%, respectively. In addition, the nylon fiber length significantly affected the deformation capacity at the peak load and the residual strength in the post-peak stage.

Modification of Hollow Expanded Microspheres with Superior Thermal Insulation Properties and Their Applications.

Thermally expandable microspheres (TEMs) are hollow polymeric particles in which a blowing gas has been encapsulated. This property makes them excellent for thermal insulation applications, such as lightweight fillers. This study has developed a viable technology for further improving thermal insulation properties in the field that needs excellent thermal insulation of textile fabrics. The ATO/TEMs composites were designed and prepared to reduce sunlight radiation by the charge gravity method. The test results showed that the ATO-coated TEMs effectively block thermal radiation from sunlight. The temperature difference between ATO/TEMs treated cotton and the uncoated cotton fabric was 9 °C, and the thermal conductivity coatings were 0.0432 W/m⋅K. The UPF value of ATO/TEMs (ILs) coated cotton fabric is 440, significantly higher than pure cotton. This approach can provide insight into the design of high-performance solar insulation composite structures.

Mechanical properties and microstructure of basalt fiber-biobased- basic magnesium sulfate cement

A low-carbon composite termed basalt fiber (BF)-biobased-basic magnesium sulfate cement (BMSC) is proposed. It utilizes recycled wood fiber (RWF) and BF as lightweight fillers and reinforcements. The microscopic mechanism of the effect of RWF and BF on the fluidity of BMSC paste and the mechanical properties of the hardened samples is discussed. The microstructure, physical phase analysis and image identification semi-quantification demonstrated that RWF enhances the development of the 5·1·7 phase. After further incorporation of BF, the fluidity and dispersion of the paste then decrease. However, the magnesium cement matrix–RWF–BF system form in the BMSC turns the single-fiber reinforcement into a composite reinforcement. It improves the mechanical properties of the composite, especially the flexural strength, even though the addition of RWF made the BMSC composite less dense. In addition, the biobased-BMSC is influenced by the coupling-competition mechanism, which is reflected by the pore structure and mechanical properties. It indicates that the low-carbon composite has the potential for carbon sequestration and the development of environmentally friendly additives for improving the performance of BMSC.

Sustainable and cost-effective ultra-lightweight engineered cementitious composite: Design and material characterization

Lightweight ECC (LWECC) has been extensively concerned due to its superior tensile performance, durability and low self-weight. However, the high environmental impact and material cost of ECC impede its broader engineering applications. The objective of this research is to develop a novel sustainable and cost-effective ultra-lightweight engineered cementitious composite (ULECC) under the micro-mechanical design theory. Five lightweight ECCs were designed using different lightweight fillers (LF) and replacement ratios with three mixtures being categorized as ULECC. The impacts of LF content and curing regimes (standard or hot-water curing) on the density, mechanical, and microstructural properties were investigated. The proposed ULECC exhibited impressive tensile behavior and a low density of 950–1260 kg/m3. The specific tensile strengths (strength-to-density ratio) and strain capacities of ULECC were 110% and 70% higher than conventional M45-ECC. Compared to the conventional LWECC, ULECC offered the competitive strength and ductility with a substantial increase in sustainability and reduction of material cost. Hot-water curing played a vital role in improving ductility-related performance. The micro-mechanical design theory and SEM analysis of ULECC well explained the test results. This research lays the groundwork for developing the sustainable and economical ULECC for future structural application.

Modeling and Optimizing the Effect of 3D Printed Origami Bubble Aggregate on the Mechanical and Deformation Properties of Rubberized ECC

A recent development in the production of lightweight concrete is the use of bubble or hollow aggregates. Due to its exceptional energy absorption and ductility properties, engineered cementitious composite (ECC) is increasingly recommended and used for structural applications, particularly in earthquake-prone regions. As a result, researchers have started looking into the benefits of lightweight ECC for such applications. However, the strength is considerably compromised due to the use of lightweight fillers such as perlite, cenospheres, glass microbubbles, and crumb rubber (CR). This study evaluates an origami-shaped bubble aggregate (OBA) novel application in rubberized ECC (RECC) to achieve density reduction at a relatively lower strength loss. The experiment is designed using response surface methodology (RSM) with the spacing of the OBA at 10, 15, and 20 mm and its quantity at 9, 15, and 21 as the input factors (independent variables). The dependent variables (responses) assessed are density, compressive strength, modulus of elasticity, and Poisson’s ratio. The results showed that adding the OBA lowered the density of the RECC by 20%. It was revealed that using up to 15 OBAs with spacings between 15 and 20 mm, a lightweight OBA-RECC with substantial strength could be produced. Similarly, utilizing 15 and 21 OBAs at 20 mm spacing, a lightweight OBA-RECC with a comparable modulus of elasticity as the control could be developed. Models for predicting the responses were developed and validated using analysis of variance (ANOVA) with high R2 values. The spacing and quantity of the OBA’s optimal input levels were determined using the RSM multi-objective optimization to be 20 and 9, respectively. These levels produced optimal responses of 1899 kg/m3, 45.3 MPa, 16.1 GPa, and 0.22 for the density, compressive strength, modulus of elasticity, and Poisson ratio, respectively.

Starch consolidation of calcium carbonate as a tool to develop lightweight fillers for LDPE-based plastics

Calcium carbonate (CaCO3) is used as a filler to improve the stiffness and processability of plastics at low cost. However, its high density limits the quantity to be used. In this work, the feasibility of using starch consolidation of eggshells-derived CaCO3 (ES) to develop lightweight fillers for low density polyethylene (LDPE)-based materials was studied. Starch, recovered from potato by-products, was combined with ES, gelatinized, dried, and milled as a fine powder. The obtained ES/starch-based particles were then compounded with LDPE and their influence on chromatic, mechanical, morphological, and density properties of mold injected LDPE-based materials was studied. Commercially available CaCO3 (COM) was used as control. ES/starch particles were 18 times less dense than the commercially available CaCO3 (2.62 g cm−3). When incorporated into LDPE-based formulations, ES/starch originated brownish materials with lower density (1.18 g cm−3) and higher stiffness (542 MPa of Young's modulus) than those produced with the COM sample (1.33 g cm−3 of density; 221 MPa of Young's modulus). Therefore, starch consolidation of ES revealed to be a promising approach to develop lightweight fillers able to provide stiffness and color to LDPE-based plastics, while valorizing biomolecules-rich by-products.

Energy-absorbing mechanism and crashworthiness performance of thin-walled tubes diagonally filled with rib-reinforced foam blocks under axial crushing

Thin-walled structures are widely used as crucial structural components for energy absorbing applications. To design lightweight thin-walled-involved composite structures with better mechanical performance remains an open issue. In this study, the X-shaped rib-reinforced foam-filled tubes were designed and tested under quasi-static axial compression. Two types of foams, i.e., the aluminum foam and the additively manufactured polylactide (PLA) foam were considered as lightweight fillers. The effects of foam block filling ratio (rib angle) and arrangement of different foam fillers on the axial crushing performance of the diagonally rib-reinforced foam block-filled tube were analyzed. Results indicated that tubes that were diagonally filled with PLA foam blocks possessed better energy absorption capacity, whereas the higher mean crushing strength was achieved by diagonally filling with two aluminum blocks. It also revealed that tubes filled with different foam blocks did not always show advantages over those filled with the same foams. Moreover, the diagonally aluminum foam blocks filled tubes with a large rib angle could induce the global buckling, whereas that with the rib angle of 120 degrees exhibited better mechanical properties in load consistency and specific energy absorption capacity. Numerical simulations were conducted to reveal the energy absorption enhancement mechanism of the tubes filled with varying combinations of the reinforced fillers. Results indicated that the interaction between the foam blocks and the reinforced rib contributed most to the increased energy absorption. Further, an analytical model for evaluating the crushing strength of the developed structure was proposed. The theoretical predictions are in good agreement with the experimental results. The idea of tailoring the fillers arrangement and assembling pattern would promote the development of optimal energy-absorbing thin-walled involved composite structures.

Determination of rational parameters for heat treatment of concrete mixture based on a hollow aluminosilicate microsphere

The research on determining rational parameters of heat treatment of a concrete mixture based on hollow aluminosilicate microspheres has defined the features of the intensifying action on the structural concrete mixture by low-pressure steam with optimum heat and mass transfer. Optimum values of temperature, humidity and speed of the medium have been identified. The obtained heat treatment parameters are subject to general regularities of structures for the formation of hydraulic bindings and are in accordance with production conditions, thus providing possibilities for their adaptation into production. The mechanisms for determining the strength of concrete stone according to the structural and thermal effectiveness of the active medium have been defined. Thanks to the strength-building mechanisms obtained, it is possible to reduce the thermal destruction capacity of the system while reducing the process heat consumption. It is confirmed that the main direction in reducing the destructive capacity is determined by the mass flow of moisture, which has the greatest heat capacity and the least thermal conductivity at the initial stages. The invention relates to periods of temperature rise and isothermal heating without impairing the mechanical properties of concrete. It is shown that the real duration excludes high-temperature destruction processes, thereby increasing the mechanical strength of concrete and reducing the overall energy consumption. Thus, there is a reason to argue that it is possible to produce strong and light concrete products under accelerated structure formation and new technologies for heat treatment of concrete based on lightweight fillers with reduced heat consumption.

Effect of nanosilica and silica fume on the mechanical properties and microstructure of lightweight engineered cementitious composites

This paper proposes the use of nanosilica (NS) and silica fume (SF) to improve the mechanical properties of lightweight engineered cementitious composites (LECCs) and compensate for the drawbacks of lightweight fillers. Twelve LECC mixtures were prepared to study the effect of NS and SF on the mechanical properties of LECCs, and the influence mechanism was analyzed by microscopy. The results showed that the incorporation of NS can significantly improve the mechanical properties of LECCs. This improvement in performance derives from the nucleation and pozzolanic effects of NS. The nucleation effect promotes the hydration of cement. The pozzolanic effect consumes more Ca(OH)2 and forms more calcium silicate hydrate (C-S-H). The combined use of NS and SF was more effective in improving the performance. Incorporating SF based on a 3% NS content can consume more Ca(OH)2 and further improve the mechanical properties of LECCs.

Investigation of gypsum composites with different lightweight fillers

Structure and behaviour of gypsum composites, prepared from flue gas desulfurization binder and three types of fine fillers (silica sand, perlite, expanded clay aggregate and waste polyurethane foam) were studied. Their structure and composition were investigated by SEM, XRD and porosimetry, mechanical, thermal and moisture properties were tested. It was found that the type and surface quality of the aggregates affect the shape and size of gypsum crystals significantly. Largest gypsum crystals are formed in the mortars with non-porous particles. With increasing surface roughness of particles the strength of the mortars increases. Mortar with expanded clay filler has the highest strength, its compressive strength was comparable with the compressive strength of the reference material with silica sand, but its bulk density was more than 40% lower and its thermal conductivity decreased to 20% of the thermal conductivity of reference material. The mortar with waste polyurethane foam has the lowest strength (2.9 MPa at 7 days) but best thermal conductivity (0.211 W/m.K) of all materials. Technical properties of composite with waste polyurethane are still sufficient for building purposes and its environmental impact is lowest of all materials.

Development of Ultra-Lightweight and High Strength Engineered Cementitious Composites

In this study, ultra-lightweight and high strength Engineered Cementitious Composites (ULHS-ECCs) are developed via lightweight filler incorporation and matrix composition tailoring. The mechanical, physical, and micromechanical properties of the resulting ULHS-ECCs are investigated and discussed. ULHS-ECCs with a density below 1300 kg/m3, a compressive strength beyond 60 MPa, a tensile strain capacity above 1%, and a thermal conductivity below 0.5 w/mK are developed. The inclusion of lightweight fillers and the variation in proportioning of the ternary binder can lead to a change in micromechanical properties, including the matrix fracture toughness and the fiber/matrix interface properties. As a result, the tensile strain-hardening performance of the ULHS-ECCs can be altered.

Adhesive Strength of Gypsum Composites with Lightweight Fillers

Gypsum composites with several types of lightweight fillers were studied. Gypsum starts to be more important material nowadays, because it is one of the most environmentally friendly building binders. Therefore, there are new ways of the larger utilization of gypsum based materials to be sought. Even though the use of fillers in the gypsum is generally not necessary, because gypsum (opposite to cement or lime) does not shrink, fillers can be used for economic reasons or to improve some other properties of the gypsum material, e.g. thermal or fire resistance. We studied the adhesive strength of gypsum composites, containing three types of lightweight fillers (perlite, expanded clay aggregate and recycled PUR) and compared them with the properties of gypsum mortar with siliceous sand. It was found, that the type of the filler has principal impact on the adhesive strength of the gypsum composite.