Pure Gypsum Research Articles

Effects of perlite content and jute fiber reinforcement on flexural behavior of the gypsum/perlite composite core-based sandwich structures

Gypsum wallboards are widely used as a building material, but limitations exist in their weight and brittleness. The incorporation of various fillers in the gypsum makes them lightweight, stiff, and capable of resisting catastrophic failure but with the cost of strength. Sandwiching the filled gypsum using a low-cost material as skin may be an innovative approach to improve the flexural properties. In this work, sandwich structures were fabricated using jute fiber reinforced and unreinforced perlite-filled gypsum as cores and low-cost brown paper as skins. The density, flexural strength, modulus, and toughness of the resulting sandwich structures were investigated. It is found that the increase in perlite content in pure gypsum and jute fiber-reinforced gypsum significantly enhances the flexural strength, modulus, and toughness of the sandwich structures. However, previous research on jute fiber-reinforced and unreinforced gypsum/perlite composite panels (without skin) showed a decrease in flexural strength due to an increase in perlite content. The maximum flexural strengths of unreinforced sandwich (URS) and jute fiber reinforced sandwiches (JRS) at a perlite content of 15 g are found to be 13.29 % and 40.79 % greater than the control sandwich with pure gypsum core. The maximum flexural toughness of the JRS at a perlite content of 20 g and that of the URS at a perlite content of 15 g are respectively 118.31 % and 79.14 % greater than the control sandwich. A significant difference in load-displacement curves between JRSs and URSs is noticed despite the similar failure sequence i.e. core cracking→skin yielding→skin tearing.

The cores regulation of paraffin-chitosan phase change microcapsules for constant temperature building

Phase change materials (PCMs) can store and release latent heat under the designed phased change temperature and have received substantial interest for energy conservation and thermal control purposes. The use of PCMs in the construction of constant temperature buildings can improve the comfortable environment and save more energy. However, the leakage of PCMs during phase change process limits the application of PCMs. In this paper, a series of PCMs microcapsules with controllable core numbers is synthesized with paraffin (37 ℃) as the core and cross-linked chitosan as the wall. The single-core phase-change microcapsules (S−PCM) and multicore phase-change microcapsules (M−PCM) were prepared by adjusting the preparation condition. The latent heat of S−PCM and M−PCM are 61.4 mJ mg−1 and 50.1 mJ mg−1, respectively. The S-PCM and M−PCM display good stability without paraffin leakage. In addition, the composite blocks of gypsum and S−PCM (GSCM) and M−PCM (GMCM) were prepared and the thermoregulatory effection was investigated, where the surface temperature of GSCM was 5–10 ℃ lower than that of pure gypsum block. PCMs may also have broad application space in electronics, cold chain, and other industries.

Effect of HPO42− and brushite on gypsum reactivity and implications for utilization of phosphogypsum in plaster production

The implementation of a sustainable development strategy holds the potential to enhance productivity, profitability, and overall efficiency by leveraging by-products from other industries. In plaster manufacturing the substitution of natural gypsum with synthetic gypsum is worth exploring. Phosphogypsum (PG) represents a significant fraction of synthetic gypsum production, arising as a by-product of phosphoric acid manufacturing. However, the presence of impurities in PG, particularly phosphorus, poses challenges to its use as a plaster material. To identify the phases present in PG, quantify their occurrences and understand their effects on dehydration and hydration processes, our study aimed to examine simplified models. These models are specifically designed to provide insights into the underlying mechanisms governing the hydration reactivity of hemihydrate. Pure gypsum and brushite were synthesized, and mechanical mixing was carried out to explore how brushite affects the characteristics of gypsum. Additionally, a solid solution of Ca(SO4)1-x(HPO4)x·2H2O, where 0 < x < 1, was prepared to characterize and quantify the syncrystallized HPO42− as well as the effects of this impurity on typical gypsum use cases. The synthesized materials underwent physical and chemical characterization using SEM, XRD, IR spectroscopy, DSC, pH and conductivity measurements, and ion chromatography. The results demonstrated that the HPO42− ions can substitute for sulfate ions in gypsum to form solid solutions. The maximum quantity of HPO42− ions in the gypsum lattice is approximately 10%, leading to the crystallization of gypsum into sand rose shape rather than needle crystals. As the concentration of HPO42− ions increases, a new phase known as ardealite (Ca(SO4)1-x(HPO4)x·2H2O) with 0.42 < x < 0.54 emerges, followed by brushite (CaHPO4·2H2O). During the calcination of brushite at 160 °C, a mixture of brushite and monetite formed that exhibits different properties compared to its natural counterpart. In the presence of syncrystallized HPO42− ions, the transformation from anhydrite III to anhydrite II occurred at higher temperatures than for pure gypsum. The reactivity of calcined samples indicate that HPO42− ions from the dehydration products of brushite caused a delay in hydration, with the maximum delay observed at a calcination temperature of 160 °C. At this temperature, monetite begins to crystallize, and it is characterized by its inert nature, exhibiting no reactivity with water. This explains the observed decrease in setting times as the calcination temperature rises. Moreover, syncrystallized HPO42− ions induced a significant delay in the hydration process. Our research revealed that adjusting the calcination temperature can mitigate the retarding effect associated with this impurity, suggesting an industrial tendency to use the lowest possible temperature during the calcination process of PG containing syncrystallized phosphate impurity. In addition, we have observed that adjusting the pH of the mixing water to lower values can significantly accelerate setting times.

Gypsum reinforced using hemp fibers: Enhanced interfacial compatibility by dual-modification strategy

Natural fibers are promising as enhancements for gypsum. Herein, the effect of using untreated, NaOH-modified, and dual-modified hemp fibers on enhancing performances of gypsum composites is examined. The dual-modification strategy applies secondary treatment on NaOH-treated fibers with NaClO, polyoxyethylene, or Tween-80. The fibers and composites are characterized by SEM, ATR-FTIR, XRD, mechanical strength, etc. The secondary modification enhances interfacial compatibility between gypsum and fibers. Compared with pure gypsum, the elastic modulus and bending strength of the composites with dual-modified fibers increase by 56% and 42%, respectively. Hydration process reveals that dual-modification using polyoxyethylene contributes to form dense, compact composite structures.

Upcycling plastic waste into fully recyclable composites through cold sintering.

Plastics have substantial societal benefits, but their widespread use has led to a critical waste management challenge. While mechanical recycling dominates the reuse of post-consumer plastics, it is limited in efficacy, especially for composites. To address this, we propose a direct reprocessing approach that enables the creation of hybrid, long-lasting, and durable composites from difficult-to-recycle plastics. This approach utilizes cold sintering, a process that consolidates inorganic powders through fractional dissolution and precipitation at temperatures far below conventional sintering; these temperatures are compatible with plastic processing. We show that this process can create inorganic-matrix composites with significant enhancements in tensile strength and toughness over pure gypsum, which is commonly found in construction waste. These composites can be recycled multiple times through direct reprocessing with the addition of only water as a processing promoter. This approach to recycling leads to composites with orders of magnitude lower energy demand, global warming potential, and water demand, when compared against common construction products. Altogether, we demonstrate the potential for cold sintering to integrate waste into high-performance recyclable composites.

Influence of steel fiber (SF) addition on the enhancement compressive strength of pure gypsum

This research examines how reinforcing pure gypsum with steel fiber (SF) changes its compressive strength. Six pure gypsum-only mixtures will be used in the study. There are two groups of these mixtures, with water-to-gypsum ratios of 0.6 and 0.7, respectively. Steel fiber volume fractions of 0 %, 0.15 %, and 0.3 % were used to subdivide each group into three subgroups further. For every group, three samples were taken in 50x50x50 mm cubes. Steel fibers added to pure gypsum mixtures were shown to boost compressive strength for both water/gypsum ratios, with the percentage increase increasing with the water/gypsum ratio. However, the compressive strength decreases for all volume fractions of steel fiber as the water/gypsum ratio rises.

Study of possibilities of cleaning of mechanical filters of baromembrane plants

The appearance of contamination on the membrane and filters, which significantly reduces the efficiency of operation (separation efficiency, water permeate flow, salt rejection) and the service life of a reverse osmosis plant, is one of the most urgent problems that arise during water treatment using this plant. Therefore, the purpose of the work is to find optimal methods for cleaning and regeneration of mechanical filters of reverse osmosis plants. The solution to this problem is carried out by means of an empirical analysis of available scientific information and conducting laboratory studies on cartridge cleaning and infiltrate processing. A cycle of experiments on cleaning of used mechanical filters of reverse osmosis in a specially assembled plant with a gradual increase in the concentration of sulphuric acid has been conducted. According to the observations during laboratory research, effective removal of dissolved iron from the solution used to wash contaminated polystyrene filters begins at pH = 4 and up to pH = 10, but at pH = 4 the settling and filtering take 24 hours, and at pH = 10 this process takes no more than an hour. As a result of further research, the most effective hydrogen indicator for settling and almost complete removal of iron from the solution is 4.5. Further increase of the hydrogen indicator to 10 is ineffective. In addition to the chemical method of neutralising the mother solution, the use of electrodialysis is also advisable, while the use of electrolyser with a lead anode would be the best option. Thus, after cleaning of one mechanical filter, almost 80 g of pure gypsum is obtained. This gypsum can serve as a highquality cement additive or be used for the production of internal cladding plates. Clean water obtained during the process can be used for subsequent cycles of other mechanical filters cleaning

Gypsum-Based Humidity-Control Material: Preparation, Performance and Its Impact on Building Energy Consumption.

This paper introduces a new type of gypsum-based humidity-control material. The material combines gypsum-silica gel humidity-control material with 20% sepiolite powder activated by calcium chloride. Both experimental and simulation studies were conducted to assess its humidity-control performance. The experimental results indicate that gypsum-based humidity-control material has the property of absorbing moisture in high-humidity environments and releasing moisture in low-humidity environments. Moreover, both environmental temperature and relative humidity (RH) have an impact on the material's humidity-control performance. At a relative humidity of 97.4%, the maximum equilibrium moisture content of the material is 0.225 g/g, which is 1.4 times that of the gypsum-silica gel humidity-control material and 4.5 times that of pure gypsum material. The simulation results indicate that gypsum-based humidity-control material effectively mitigates indoor relative humidity fluctuations and maintains indoor air relative humidity within a narrow range. Furthermore, the material has the potential to reduce building energy consumption. This is especially evident under climate conditions with large temperature and relative humidity differences between day and night, such as in Beijing, Paris, and Atlanta. The maximum potential energy-saving rate in Beijing can reach up to 19.31%.

Comparative analysis of fracture characteristics between rock and rock-like materials

In order to investigate the characteristics of rock and rock-like materials during the fracture process, notched semi-circular bending (SCB) experiments of 3 rocks and 2 rock-like materials were conducted in this paper. The process of the crack mouth opening was measured with a clip gauge. Acoustic emission was used to analyze the damage and failure mode of the specimens. Meanwhile, the fracture process zone (FPZ) was analyzed with the digital image correlation (DIC). Finally, the differences in the fracture process between rocks and rock-like materials were observed with a polarized microscope, and the formation mechanism of FPZ was discussed. The results indicate that the sequence from brittleness to plasticity is gypsum, marble, granite, concrete and fine sandstone. The crack opening velocity of gypsum, marble, and granite reaches 0.02–0.025 mm/s, far exceeding that of sandstone and concrete at 0.003 mm/s and 0.005 mm/s. The stronger the brittleness of geomaterials, the less significant their acoustic emission effect. Only a few acoustic emissions occur during the fracture process of gypsum with 8 hits. Its fracture occurs instantaneously rather than through a process of damage to fracture and the failure mode is tensile failure. Sandstone has the strongest plasticity, with a large count of acoustic emissions before and after fracture, with a hit number of 5062, which is 630 times of pure gypsum. The fracture is a process of damage accumulation with 94% of sandstone, 89% of concrete, 80% of granite, and 60% of marble showing a tensile and shear failure mode except gypsum. In addition, the stronger the brittleness of geomaterials, the smaller their FPZ size. The FPZ of gypsum is only about 3 mm, which can be considered as lacking, while other materials are about 6–11 mm. The formation of FPZ depends on whether an interlocking structure can be formed inside the material, which is related to the base material and crystalline or aggregate particle size.

Performance enhancement and mechanism of pregelatinized starch–binding gypsum at high water–gypsum ratios

Minimizing gypsum powder usage by increasing water to gypsum (w/c) ratios has both economic and environmental benefits. However, gypsum is limited in application by its poor mechanical strength at high w/c ratios. To enhance the strength of hardened gypsum at high w/c ratios, this paper proposes a pregelatinized starch–binding gypsum structure. The mechanical strength, working abilities, and microstructure of pregelatinized starch–binding gypsum samples at high w/c ratios were evaluated. And the micro-nano structure and enhancement mechanism of pregelatinized starch–modified gypsum was investigated. The results show that at high w/c ratios from 0.8 to 1.0, pregelatinized starch significantly improved the mechanical properties of gypsum, where the flexural and compressive strength of 3 d modified drying sample were 3.3 MPa and 6.6 MPa in comparison to pure gypsum samples tending to 0 MPa. Pregelatinized starch participates in the overlapping structure of gypsum crystals and bind to them without affecting the crystal structure and morphology of single particles. The nanostructure of modified contact points involved strong adsorption of pregelatinized starch onto the (120) face by hydrogen bonding, which enhanced binding adhesion at contact points. And pregelatinized starch effectively reduced separation of the (120) face under x– and z– tensile stretching, and slipping along the (010) face under y– tensile stretching. This paper presents a modification that enhances mechanical properties of gypsum at high w/c ratios, and provides deeper understanding of crystal overlapping mechanisms at the nanoscale.

Rice husk and coir fibers as sustainable and green reinforcements for high performance gypsum composites

Reinforcing gypsum with coir and rice husk enhances the flexural properties, acoustic and thermal insulation and resistance to environmental degradation. Coir and rice husks are agricultural coproducts available in large quantities at low cost and are renewable and sustainable source. In addition, coir provides excellent strength increase and rice husks have low density and good thermal resistance. In this study, rice husk and coir were used as reinforcement for gypsum as individual components and also as blends. Up to 30 % of reinforcement was possible with enhanced properties. Compared to pure gypsum, up to 187 % increase in flexural strength, reduced moisture absorption and excellent thermal resistance were achieved. Highest flexural strength of 1.5 MPa was obtained when 10 % rice husk was added compared to highest strength of 5.6 MPa when 30 % coir fibers were added into gypsum. An equal proportion of 50 % ricehusk and 50 % coir fibers provided the highest flexural strength for the hybrid composites. Addition of ricehusk and coir also improved the acoustic resistance particularly between 2500 and 4000 Hz whereas there was no major difference in the thermal conductivity of the samples with and without the reinforcement. The extent of increase in properties could be controlled by varying the proportion of ricehusk and coir in gypsum ceiling tiles. Developing hybrid composites particularly in equal proportion of ricehusk and coir was found to be better in terms of improving the performance of gypsum. Being byproducts of major food crops, ricehusk and coir provide sustainable and renewable source for developing composites. Reinforcing gypsum with ricehusk and/or coir will also assist in decreasing the environmental burden and increasing the sustainability of buildings.

The Influence of Hydroxyethylmethyl Cellulose on the Heat Released during the Hydration of Modified Gypsum Materials

This article presents the results of experimental research of modified gypsum materials. The primary aim of the research was to assess the influence of the hydroxyethylmethyl cellulose (HEMC) polymer on the heat of hydration of gypsum. In the study, the polymer was used as an additive in weight ranges from 1% to 3% in relation to pure gypsum. The water to gypsum ratio was at the level of 0.75. The heat of hydration of building materials is crucial, because it is one of many aspects that directly affects the binding time, therefore defining the potential applications of gypsum in the construction industry. It was shown that the addition of the polymer influences the value of the heat of hydration, and also extends the crystallization process. Based on the Avrami equation, two areas of the early and late stage crystallization of gypsum were observed. The obtained values of the kinetic parameter n of this equation indicate a different mechanism of crystal growth. With an increased content of the polymer, there was a decrease in the K parameter, which confirms that HEMC interferes with gypsum nucleation and crystallization.

Improved flexural strength and morphology of gypsum by wollastonite

AbstractThe role of β‐wollastonite on the flexural strength of gypsum obtained from the hydration of alpha‐hemihydrate was investigated in this work. Starting with a synthesized Xonotlite obtained from the industry, dehydration was carried out at 880°C giving rise to the β‐wollastonite which was identified by X‐ray diffraction. The pure gypsum samples were prepared and compared with 3% and 5% replacements of the wollastonite. Increased flexural strengths were observed for 2, 7 and 28 days of storage in room temperature, normal water, and cold water. It was remarkable that the strength in water storage increased. The crystal morphology of the obtained gypsum was also improved in the presence of β‐wollastonite.

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.

Use of graphene as an additive to improve the mechanical properties of gypsum plaster

This work aimed to investigate the effects of graphene nanoparticles on the mechanical and morphological properties of gypsum plaster paste. In order to do so, samples of pure gypsum plaster paste with multilayer graphene were produced. These samples were prepared with a water/plaster factor (w/p) of approximately 0.5 with different graphene dosages. The mechanical analysis results showed that the graphene dosage of 0.02% increased the compressive and tensile strength values in the order of 120%. The increase in these properties is most likely due to the heat dissipation promoted by graphene, the greater production of crystalline nuclei and the reactivity of graphene with Ca2+ ions. Regarding the plaster setting times, a reduction in the values was observed for most samples, indicating an increase in the production of crystalline nuclei. FTIR analyzes indicate that there were no changes in terms of chemical properties.

Thermal and mechanical evaluation of natural fibers reinforced gypsum plaster composite

Many problems such as the increase in the world population, global drought, and greenhouse gases have caused materials used in industries to be reconsidered. This is how the concept of green composite material emerged. Using natural fibers to obtain such materials is important in terms of sustainability. This study is aimed to use hemp fiber and banana fiber as natural fiber additives in the gypsum composite to produce green bio-composite. Natural fibers are chemically modified with 5% NaOH solution. In this way, a good fiber/matrix interface interaction is provided. The composite hardness test result of 5 wt% HB fiber added sample is obtained as 50.4. Compared to the control plaster sample test result, which is 53.6, a slight decrease can be seen. However, it is observed that the fibers held the structure together and sopped the crack propagation. The increase in the porous structure with fiber addition caused a decrease in the thermal conductivity of the composite. Comparing thermal conductivity result of 5 wt% HB fiber reinforced gypsum composite (0.131 W⸳mK-1) with respect to pure gypsum result (0.237 W⸳mK-1), it gave a promising result as an insulation material.

Microstructural Properties of Gypsum Composites containing Pineapple Leaf Fibre

The interest in prospective uses of gypsum as a finishing component has diminished in recent years as a result of its weak mechanical strength, which is essential in interior construction. Therefore, to overcome this challenge, researchers have come up with various ways of improving the gypsum composite materials. The microstructure of the composites and the contact surface with pineapple leaf fibre were investigated by Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD). The microstructural properties of the gypsum paste changed when pineapple leaf fibre was added. These studies showed that at 2% fibre volume, a jellylike surface coating was formed around the gypsum crystals, giving the pineapple leaf fibre (PALF)-gypsum composite its high interlocking and compactness, thereby impacting high strength than the pure gypsum and this suggests its broader application in building industry for production of partition boards

Hydration and mechanical properties of FGD gypsum-cement-mineral powder composites

Solving the problem of environmental pollution caused by flue gas desulfurization gypsum (FGD gypsum) accumulation is conducive to improving FGD gypsum green and sustainable development. In this study, the ternary system was prepared by using FGD gypsum, cement,and mineral powder. The simplex-centroid design method was used to determine the optimal proportions of FGD gypsum, cement, and mineral powder. The optimal proportions of FGD gypsum, cement, and mineral powder were designed by the simplex-centroid design method. The effects of cement and mineral powder contents on the mechanical and hydration properties of the ternary system were analyzed by contour map. Furthermore, the phase composition and microscopic morphology of the ternary system were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Hydration processes of all samples were observed by the hydration heat. It was observed that the optimal proportions of FGD gypsum, cement, and mineral powder were 75%, 5%,and 20%, respectively by comprehensive considerations of strength, softening coefficient, water absorption, hydration, and microstructure. Compared with pure gypsum, both binary and ternary systems consisting of gypsum, cement, and mineral powder showed good water resistance. The softening coefficient at 28 d improved, reached 0.71 at the optimal proportion.

Preparation, performance study and application simulation of gypsum-paraffin/EG composite phase change building wallboard

The performances and application parameters of phase change materials (PCM) are crucial for integration with construction in practice. In this paper, composite PCMs (CPCM) were prepared by paraffin/expanded graphite (EG) and applied to phase change gypsum board (PCGB). The composite PCM was characterized by SEM, DSC, leakage ratio and thermal conductivity tests to determine the optimal ratio of EG and paraffin; The thermal storage and release properties of PCGB were experimentally investigated by two building cabin models. The results showed that the CPCM obtained 12 wt% EG exhibited excellent thermal conductivity (2.32 W/mK) and latent heat (103.9 J/g). The PCGB prepared with above CPCM has excellent thermal conductivity (0.3968 W/mK) and latent heat (42.2 J/g). When the EG content exceeded 12%, the thermal properties and leakage ratio of the CPCM stabilized after 200 thermal cycles despite the increase of EG. The phase change cabin exhibited much lower heating and cooling rates than that of the pure gypsum cabin, with a 1.14 °C decrease in peak internal surface temperature and a 3.4 °C decrease in temperature fluctuation. In addition, the room temperature of the established reinforced concrete wall model with PCGB was simulated based on the hourly variation pattern of the winter-summer temperature in Urumqi, China. The results show that in summer, the PCGB with phase change temperature of 29–31 °C and thickness of 20 mm possesses a larger heat storage capacity, with a smaller average internal surface temperature (28.63 °C) and a higher average phase change utilization (61.5%), which can reduce the cooling and heating load of the wall and save energy effectively.

Thermoregulating gypsums by using nanoencapsulated phase change material slurry

Thermoregulating composites were produced by using a thermoregulating slurry (NPCS) containing nanoencapsulated phase change material (NPCM) from poly(styrene-co-divinylbenzene) as shell and the commercial paraffin Rubitherm®RT27 as core material. These composites were synthesized by using the constitutive water of the slurry as setting water and changing the NPCM/Hemihydrate (NPCM/Hem) mass ratio within 0.0–0.41. It was found that nanoparticles were uniformly dispersed into the gypsum, and the gypsum crystal morphology was tuned by the addition of the slurry. Attending to the thermal properties, these materials can work either as insulating or thermal energy storage materials, decreasing the thermal conductivity up to ~ 50%, whereas the thermal energy storage (TES) capacity is enlarged in a ~ 140%, respect to the pure gypsum, when the maximum NPCM/Hem mass ratio was used. This composite had a latent heat of 30.2 J g−1 and a heat capacity of equivalent 3.5 J g−1 K−1. Composites from a NPCM/Hem mass ratio up to 0.15 satisfied European mechanical standard EN 13,279–1 for gypsum binders and gypsum plasters and all of them, presented a bulk density higher than 0.60 g cm−3. The addition of a 41% in mass of nanocapsules allowed to save 13.5 kWh m−3 and, reducing the CO2 emissions up to 3.4 kg of CO2 per operating cycle. The use of this new material would lead to significant energy and economic savings, as well as a considerable reduction in the emission of polluting gases into the atmosphere.