Search Results (27)

Rapid urbanization and the widespread use of impervious materials have intensified the urban heat island (UHI) effect, raising surface temperatures and energy demands. Conventional concrete pavements contribute significantly due to their high thermal conductivity and low reflectivity. This study systematically investigates the development of thermally efficient concrete paver blocks using sustainable alternative fine aggregates to mitigate heat accumulation while retaining a minimum compressive strength of 35–45 MPa (recommended for medium traffic). Unlike prior isolated studies, this research offers a comprehensive comparative analysis of three sand replacements—Vermiculite powder (12.5–50%), Perlite powder (20–80%), and Crushed Glass (7.5–30%)—in M30-grade concrete. Fresh and hardened properties were evaluated through slump, density, and compressive strength tests at 7, 14, and 28 days, while infrared thermography quantified surface temperature variations under controlled heat exposure. Results showed significant thermal improvements, with optimal mixes Vermiculite 25% (VC-25), Perlite 40% (PR-40), and Crushed Glass 15% (CG-15) reducing surface temperatures by 25.1 °C, 22.2 °C, and 18.2 °C, respectively, while maintaining compressive strengths of 47.8 MPa, 38.8 MPa, and ~58 MPa. VC-25 proved superior, achieving the lowest surface temperature (26.3 °C) and 48.8% lower heat absorption than conventional concrete. The study establishes optimal replacement thresholds balancing insulation and strength, supporting SDGs 11, 12, and 13 through climate-responsive, resource-efficient construction materials. Full article

This study reports the successful fabrication and application of floatable syntactic foams derived from fine magnesium powder (<45 µm) utilizing expanded perlite (0.25 g/cm³, 0.2–0.4 mm) as the pore former. Sample disks with densities as low as 0.9 g/cm³ were produced via the classical press and sinter process. To ensure reasonable mechanical properties, the specimens were formed under a pressure of 200 MPa in a hardened steel die, followed by high-vacuum sintering (~3 × 10⁻⁶ torr) at 640 °C for 1 h. The resulting foams exhibited sufficient mechanical strength to allow for precision machining into a microboat. We demonstrated their potential use as a Marangoni-induced microswimmer. Spontaneous locomotion was observed when ethanol was used as a propellant, which generates a surface tension gradient between the upper and rear parts of the swimmer. The microboats achieved propulsion speeds of approximately 160 mm/s when propelled by a 95% ethanol + 5% ink mixture. Using a small volume (~4 µL) of the alcohol mixture, the swimmer could cover distances exceeding 350 mm. Full article

The pore structure of cocopeat-based substrates critically influences their hydraulic properties, directly affecting water use efficiency in soilless cultivation systems. Previous macroscopic modeling approaches infer pore structures indirectly from water retention curves and rely on empirical parameterization of pore geometry and connectivity, overlooking microscale features that directly control fluid pathways and permeability. To address this gap, this study employed micro-CT imaging to reconstruct the three-dimensional pore structures of coarse cocopeat and a fine cocopeat–perlite mixture. Nine regions of interest (ROIs), representing three typical pore types in each substrate, were selected for quantitative pore structure analysis and pore-scale saturated flow simulations. Results show that over 90% of pore diameters in both substrates fall within the 0–400 μm range, and variations in cocopeat particle size and perlite addition significantly affect average pore diameter, porosity, fractal dimension, and tortuosity, thereby influencing permeability and local flow distribution. This study provides new insights into the microscale mechanisms governing water movement in cocopeat-based substrates and reveals key structural factors regulating hydraulic behavior in soilless cultivation systems. Full article

This research investigates the influence of incorporating perlite aggregate and silica fume on the properties of cement mortar, with a focus on compressive strength, flexural strength, density, water absorption, and thermal conductivity. The results show that increasing the percentage of perlite (Pe) in the mixes causes a marked reduction in the compressive strength, reflecting the lightweight nature and low density of perlite. For mixes with Pe-20% through Pe-100%, the compressive strength decreased by up to 78% compared to the reference mix. However, the addition of silica fume (SF) in mixes with SF-20% to SF-100% partially offset this effect, limiting the strength losses to 18–71%, which indicates that silica fume contributes to strength enhancement over time. The flexural strength followed a similar trend, decreasing with a higher perlite content: reductions of up to 40% were observed for Pe mixtures, while SF mixes showed slightly smaller decreases, reaching 36%. The density also declined consistently with increasing perlite replacement, with a maximum reduction of 57% in mix Pe-100% due to the inherent porosity of perlite. The water absorption increased substantially in the same mix (Pe-100%), by 327% compared to the reference one, whereas the addition of silica fume (SF-100%) limited the increase to 181%, confirming its role in refining the pore structure. The thermal conductivity decreased with a higher perlite content, attributed to the formation of voids in the matrix. The lowest value was observed for Pe-100%, with an 82% reduction, while silica fume mixes also showed reductions of 37–81% relative to the reference mix. Based on a comprehensive evaluation of strength, density, water absorption, and thermal performance, mix SF-60% was identified as the optimal mixture, offering a balanced profile with a compressive strength of 4.4 MPa, thermal conductivity of 0.28 W/(m·K), and density of 1089 kg/m³. These performance levels make the developed mortars particularly suitable for non-load-bearing masonry units, lightweight blocks, and insulation panels, where reduced weight and enhanced thermal efficiency are essential. The study therefore provides practical guidance for the design of sustainable, lightweight mortars for energy-efficient construction applications. Full article

This study investigates the influence of varying water-to-cement (W/C) ratios and fine aggregate compositions on the performance of concrete incorporating expanded perlite aggregate (EPA) as a lightweight alternative to natural sand. A total of eighteen concrete mixes were produced, each with different W/C ratios and fine-to-coarse aggregate (FA/CA) ratios, and evaluated for workability, compressive strength, flexural and tensile strength, water absorption, density, and thermal conductivity. Perlite was used to fully replace natural sand in half of the mixes, allowing a direct assessment of its effects across low-, medium-, and high-strength concrete formulations. The results demonstrate that EPA can improve workability and reduce both density and thermal conductivity, with variable impacts on mechanical performance depending on the W/C and FA/CA ratios. Notably, higher cement contents enhanced the internal curing effect of perlite, while lower-strength mixes experienced a reduction in compressive strength when perlite was used. These findings suggest that expanded perlite can be effectively applied in structural and non-structural concrete with optimized mix designs, supporting the development of lightweight, thermally efficient concretes. Mixture W16-100%EPS was considered the ideal mix because its compressive strength at the age of 65 days 44.2 MPa and the reduction in compressive strength compared to the reference mix 14% and the reduction in density 5.4% compared with the reference mix and the reduction in thermal conductivity 14% compared with the reference mix. Full article

This paper aimed to evaluate two self-healing mechanisms of concrete exposed to chloride ions and carbon dioxide environments using chemical and bacterial solutions, contributing to understanding the real scenarios of concrete structures application. Expanded perlite (EP) impregnated with chemical and bacterial solutions with the aid of either a vacuum chamber or immersion was used in partial substitution of fine natural aggregate in ratios of 10%, 20%, and 30%. Samples were characterized by a compression strength test. Healing efficiency was evaluated with high precision in stereo zoom microscopy. Further characterization of the samples was obtained from SEM/EDS, and mineral content was determined from XRD. Samples impregnated with a chemical solution formed healing products identified as C-S-H, CaCO₃, and SiO₂ across and overflowing the fissure. Samples impregnated with the bacterial solution presented a maximum continuous healing region of 1.67 mm and an average of 0.514 mm. A comparison of submersed and wet curing yielded an equal number of results between the techniques. Overall, the products formed were mostly calcite (CaCO₃) and C-S-H, while the presence of CO₂ and Cl⁻ corrosives did not affect healing, with concentrations of 5% and 3%, respectively. Full article

This study compares the workability, mechanical, and thermal characteristics of structural self-compacting lightweight concrete (SCLWC) formulations using pumice aggregate (PA), expanded perlite aggregate (EPA), fly ash (FA), and silica fume (SF). FA and SF were used as partial substitutes for cement at a 10% ratio in various mixes, impacting different aspects: According to the obtained results, FA enhanced the workability but SF reduced it, while SF improved the compressive and splitting tensile strengths more than FA. EPA, used as a fine aggregate alongside PA, decreased the workability, compressive strength, and splitting tensile strength compared to the control mix (K0). The thermal properties were altered by FA and SF similarly, while EPA notably reduced the thermal conductivity coefficients. The thermal conductivity coefficients (TCCs) of the K0–K4 SCLWC mixtures ranged from 0.275 to 0.364 W/mK. K0 had a TCC of 0.364 W/mK. With 10% FA, K1 achieved 0.305 W/mK; K2 with 10% SF reached 0.325 W/mK. K3 and K4, using EPA instead of PA, showed significantly lower TCC values: 0.275 W/mK and 0.289 W/mK, respectively. FA and SF improved the thermal conductivity compared to K0, while EPA further reduced the TCC values in K3 and K4 compared to K1 and K2. The compressive strength (CS) values of the K0–K4 SCLWC mixtures at 7 and 28 days reveal notable trends. Using 10% FA in K1 decreased the CS at both 7 days (12.16 MPa) and 28 days (22.36 MPa), attributed to FA’s gradual pozzolanic activity. Conversely, K2 with SF showed increased CS at 7 days (17.88 MPa) and 28 days (29.89 MPa) due to SF’s rapid pozzolanic activity. Incorporating EPA into K3 and K4 reduced the CS values compared to PA, indicating EPA’s lower strength contribution due to its porous structure. Full article

Perlite is a volcanic glass that, under thermal treatment, expands, producing a highly porous and lightweight granular material which finds application in the construction, horticulture, insulation and other industrial sectors. Proper control of the feed properties and the expansion conditions allows the production of purpose-oriented grades, while the primary evaluation of its appropriateness for use in each sector is performed by the proper characterization of relevant physical, thermal or/and mechanical properties. However, due to its extreme fineness, low density, and friability, most of the available characterization methods either fail in testing or provide erroneous results, while for certain properties of interest, a method is still missing. As a consequence, the way towards the evaluation of the material is rife with uncertainties, while a well-defined methodology for the characterization of the critical properties is of practical importance towards the establishment of a pathway for its proper analysis and assessment. This article presents the available methodology for determining the main properties of interest, i.e., the size and density, water repellency/absorption and oil absorption, the microstructural composition, crushing and abrasion resistance and isostatic crushing strength, and also sampling and size reduction processes. The issues raised by the application of existing methods are analyzed and discussed, ending up to a proper methodology for the characterization of each property, based on the long-term experience of the Perlite Institute. The study is supplemented by updated insights on ore genesis, physicochemical properties, mineralogical composition and the expansion mechanism, as background information for the sufficient comprehension of the nature and properties of perlite. Full article

The present research compared the behaviours of lightweight mortars based on ordinary Portland cement (OPC), calcium sulphoaluminate cement (CSAC), and calcium aluminate cement (CAC) containing expanded perlite and subjected to elevated temperatures. The perlite substituted natural sand in amounts of 25, 50, 75, and 100% by volume. The mortars were subjected to heating at up to 300 °C, 650 °C, and 1000 °C at a rate of 20 °C/min. The consistency and density of fresh mortars, compressive strength and density of hardened mortars after heating and cooling, and absorbability were assessed. Such a holistic testing approach is the main novelty of this research, which is related to the aforementioned mixtures and elevated temperatures. The main contribution of this article is a comparison of various cement types coupled with variations in the level of sand replacement with expanded perlite. In previous studies, comparisons were made in pairs of OPC-CSAC and OPC-CAC for normal-weight concrete. There is a gap in our knowledge of triple comparisons and lightweight cement composites which is filled by the current study. The use of OPC at up to 650 °C is recommended because it is the most common solution, its performance is similar to that of CAC, and it is cheaper than other solutions. Above 650 °C and up to 1000 °C, CAC is the only solution because it performs better than other cements. CSAC is not suitable for use at elevated temperatures because of its poor strength performance, even if it is the best solution from an environmental point of view. Sand replacement with perlite does not increase the strength performance under elevated temperatures, but its efficiency is different for various types of cement. Full article

Perlite waste materials with different particle sizes were evaluated as potential candidates for removing the malachite green (MG) and Congo red (CR) dyes from contaminated water. Two types of waste, referred to as coarse (CP) and fine (FP), with particle sizes of 0.075 mm, 0.045 mm, and 0.037 mm, were used. The samples were characterized using X-ray diffraction, X-ray fluorescence, Fourier transform infrared spectroscopy, and N₂ adsorption/desorption. The adsorption efficiency of MG and CR was investigated by varying the parameters of pH, contact time, and initial concentration. The reduction in particle size significantly influenced the removal of the CR dye, leading to an increase in the adsorption rate of 23.9% and 45.5% for CP and FP, respectively. Conversely, the adsorption of the MG dye on the residues was not affected by different particle sizes. CP and FP exhibited a removal rate exceeding 70% for both dyes. The adsorption of MG and CR on the wastes was well-described by the Sips isotherm model. The results of adsorption kinetics were best fit by the Elovich model. Perlite waste materials have demonstrated significant potential for the adsorptive remove of cationic and anionic dyes from aqueous solutions. Full article

There is an increased interest in the hydroponic production of strawberries in protected cultivation systems, and it is, therefore, urgent to develop new, more sustainable growing media alternatives. This study investigated the physical properties of wood fiber produced from Norway spruce (Picea abies (L.) H. Karst.) and peat:wood fiber substrate blends as well as the performance of the wood fiber in comparison to the industry standards, i.e., peat and coconut coir in the cultivation of hydroponic strawberry. Tray plants of the June-bearing strawberry (Fragaria × ananassa Duch.) cultivar ‘Malling Centenary’ were transplanted into five different growing media: a peat (80%) and perlite (20%) mixture, stand-alone (100%) coconut coir and three stand-alone (100%) Norway spruce wood fiber substrates (including coarse textured fibers with compact and loose packing density and compacted fine-textured fibers). Ripe strawberries were harvested and registered throughout the production season. The overall marketable yield was comparable across all the tested growing media; however, after 4 weeks of harvest, both coarse wood fiber and fine wood fiber showed better fruiting performance than the peat-perlite mixture. A trend for earlier berry maturation was observed for all wood fiber-based substrates. Plant parameters recorded after the end of production showed that plant height, number of leaves, and biomass production were higher in coarse wood fiber than in the peat-perlite mixture. Moreover, plants grown in wood fiber-based substrates had less unripe berries and flowers not harvested in comparison to both the peat and coir treatments. Full article

The influence of the components of plaster mortars on their properties is considered in a lot of studies at a qualitative level without searching for optimal compositions of these multicomponent composite materials. The purpose of this study was to obtain the experimental–statistical models based on the results of the designed experiment, allowing the influence of light fillers and polymer admixtures on the properties of the mortars to be evaluated and analysed; the compositions complying with specified requirements and compromised optimally by a number of properties should be found. The quantities of fine limestone and perlite as well as of the hydroxyethyl methyl cellulose and dispersible polymer were varied in the experiment. The effective viscosity and thixotropy of the mix, compression, tensile, adhesive strength, frost resistance, and density of hardened mortars were determined for 18 compositions according to the experiment design. The obtained models have allowed the individual and synergetic effects of mix components to be evaluated. The fine perlite has turned out to have the greatest positive effect on the properties. This porous filler increases the strength while decreasing the density of the mortars. It is shown how the composition complying with specified requirements—and the best based on several properties—has been found. Full article

In this paper, perlite mining and rice production by-products, namely run-of-mine perlite and rice husk ash, are used as fine aggregates in combination with pumice and calcareous aggregates to produce lightweight concrete. Their use is evaluated mainly in terms of the durability of the concrete, by comparing four optimized lightweight concrete mixtures of similar density and strength with a reference one of normal weight. The sorptivity due to capillary sorption, open porosity, chloride migration, penetration resistance, and freeze and thaw response were studied to evaluate the durability of the lightweight concrete. According to the experimental results, the examined mixtures developed an adequate strength in order to be classified into strength classes greater than LC25/28 and, therefore, be used in structural applications. The durability of the mixtures was also sufficient, especially as far as the chlorides’ penetration resistance is concerned, which was found to be up to 39% lower compared to the reference mixture. The sorptivity and open porosity of the LWC mixtures increased due to the porous nature of the lightweight aggregates, and the mixtures were also found to be susceptible to freeze and thaw cycles. Exceptionally, the lightweight concrete mixtures comprising pumice and perlite exhibited a lower sorptivity and resistance to chloride penetration than the standard concrete and a promising tolerance to freezing and thawing. Thus, the optimized combination of pumice and perlite is a sustainable recommendation for structural lightweight concrete production and use, promoting the wider exploitation of natural aggregates with an acceptable compromise on strength and durability. Full article

The physical properties of growing media are dependent on the morphological characteristics of the particles composing them. Thus, their characteristics can be more precisely altered for specific purposes by a better morphological design of materials to optimize the use of raw materials and increase water efficiency. There are many references on the relationship between basic particle size and physical properties, but the arrangement of the particles and the resulting physical properties are also affected by the shape of the particles. Growing media have seldom been characterized by shape criteria and, therefore, their influence remains unknown. A dynamic image analyzer, the QicPic device, was used to assess particle shape and size for a wide diversity of growing media constituents. As well as Feret_MAX and Chord_MIN diameters describing individual particle length and width, respectively, individual particle shape was analyzed in terms of several descriptors (aspect ratio, circularity, roundness, and convexity). A classification was established to discern different particle shapes and all materials were described accordingly. Correlations between particle morphology descriptors were reported, showing that the greater the particle length, the smaller the width/length ratio, circularity, roundness, and convexity. Circularity, roundness, particle length, and its associated relative span were identified as the most relevant parameters describing materials’ morphology. This work shows a large diversity in particle morphology of growing media constituents, which were categorized into four classes of materials. Three classes were mainly described according to their particle shapes, with a decreasing elongation and an increasing circularity, roundness, and convexity: (1) fine and coarse wood and coir fibers; (2) all Sphagnum white peats, milled or sod; and (3) black peats, sedge peat, coir pith, fresh and composted pine bark, green waste compost, and perlite. A fourth class was represented by coir medium (mixing pith and fibers) and was above all characterized by high diversity in particle length. These findings extend the characterization of the materials for a more thorough evaluation of the links between particle morphology and physical properties. Full article

A cellular concrete with a fine porous structure was experimentally made using the corrosion technique for aluminum powder as an expanding agent in an aqueous solution of Ca(OH)₂. The originality of this paper was the use of our own production method for the fine aluminum powder through atomizing the recycled molten waste of this metal using concentrated jets of nitrogen. Additionally, the waste melting technique involved our own microwave heating method. A high weight proportion of calcined gypsum (maximum 82.3%) represented the main concrete binder. Using moderate contents of coal fly ash (3.6–11.1%) together with perlite (4.6–6.4%) to reduce the pore size and silica fume (0.3–1.2%) with pozzolanic properties, the aim was to obtain a macrostructure characterized by a very low pore size and to increase the compressive strength (by up to 4.1 MPa), despite the relatively low density (below 641 kg/m³). An industrial method of increasing the mechanical strength by steam curing fresh concrete was applied. Full article