Recycling Of Gypsum Research Articles

From waste to resource: Exploring the recyclability and performance of gypsum-graphene nanofiber composites

Gypsum is a widely used building material with a variety of benefits, including good fire resistance, sound insulation, and environmental friendliness. However, gypsum disposal is commonly associated with significant environmental risks, including unhealthy gas emissions and land degradation. Gypsum recycling can help to reduce these impacts, but it can also lead to a decrease in the performance of the recycled gypsum products. This study investigated the effects of graphene nanofibers (GNFs) on the recyclability and properties of gypsum plasters. The results showed that test samples containing 1 % of GNFs exhibited improved mechanical response, with flexural and compressive strength exceeding those of neat gypsum by 30 % and 60 % respectively. This improvement is attributed to the retained functional properties of GNFs during the recycling process. Recycled gypsum pastes containing GNFs presented a more uniform and denser matrix with longer crystals, enhanced bonding, and reduced porosity. These findings suggest that GNFs can be used to facilitate the recycling of gypsum waste and to produce recycled gypsum components with improved properties. Overall, this study demonstrates the potential of GNFs to improve the sustainability and performance of recycled gypsum plasters.

SITUAÇÃO DA GESTÃO DE RESÍDUOS DA CONSTRUÇÃO CIVIL: ESTUDO DE CASO DE CAPÃO DA CANOA, RIO GRANDE DO SUL

A indústria da construção civil é responsável por impactos ambientais, sociais e econômicos consideráveis, pois possui uma posição de destaque na economia brasileira. A Resolução CONAMA 307 classifica os resíduos da construção civil como classe A (inertes), B (recicláveis), C (não recicláveis) e D (perigosos). O trabalho foi realizado no município de Capão da Canoa/RS, dispondo sobre a análise dos planos de gerenciamento de resíduos de construção e demolição, avaliação da percepção ambiental dos geradores e identificação de potenciais problemas quanto ao gerenciamento e cumprimento da legislação vigente. Os resíduos classe A são os mais gerados, os resíduos classe C estão sendo destinados incorretamente e carece-se de alternativas locais para a reciclagem de gesso. Os empreendedores da construção civil apresentaram consciência quanto as formas de classificação e disposição desses resíduos. A redução da geração de resíduos na fonte e a substituição de matérias primas por outras mais rentáveis são uma boa alternativa.

Physical weathering of carbonate host-rock by precipitation of soluble salts in caves: A case study in El Orón-Arco Cave (Region of Murcia, SE Spain)

The dissolution of carbonate host-rock by freshwater in phreatic or vadose conditions is the most common mechanism for the formation of caves; however, circulation of saline solutions through carbonate materials and precipitation of soluble salts may also play an important role. We studied the stable isotope composition (δ18O and δ34S of sulfate, δ18O and δD of structurally-bound gypsum hydration water and 87Sr/86Sr) and salinity of fluid inclusions in gypsum speleothems found in El Orón-Arco Cave (Cartagena, SE Spain). We suggest that physical weathering of carbonate host-rock was driven by precipitation of soluble sea-salts (mostly gypsum and halite), and this process controlled the recent geomorphological evolution of the cave. The Triassic carbonate host-rock shows clear evidence for salt weathering, including gypsum/halite infillings in cracks of the bedrock, mechanical spalling of the carbonate, and detachment of rock fragments that lead to the formation cave voids and in-situ accumulations of piles of unsorted rubble. Sulfur and oxygen isotopes of gypsum sulfate (3.0‰ < δ18O < 11.6‰ and 16.7‰ < δ34S < 20.7‰) are generally lower than modern seawater sulfate and suggest contributions from a 34S-depleted source (i.e. oxidation of pyrite). The δ18O and δD of gypsum hydration water are relatively low compared to expected values for the evaporation of pure seawater to gypsum saturation, suggesting that gypsum precipitation involved a secondary calcium-sulfate source or recycling of gypsum from previous stages, along with mixing of seawater and meteoric water seepage to the cave. The 87Sr/86Sr in gypsum shows intermediate values between modern seawater and Triassic carbonate values because of interaction between the solution and the bedrock. The salinities of the speleothem-forming solutions are relatively high (13.2 ± 3.2 wt% eq. NaCl) compared to gypsum formed from evaporated brackish solutions (i.e. ~4–8 wt% eq. NaCl) and indicate dissolution of earlier evaporites before secondary gypsum precipitation. This cave-forming mechanism, which is related to saline water circulation and precipitation of evaporitic minerals, may be common in other coastal caves.

Role and fate of the lead during the conversion of calcium sulfate dihydrate to α-hemihydrate whiskers in ethylene glycol-water solutions

The behavior of Pb, a toxic heavy metal that commonly exists in flue gas desulfurization (FGD) gypsum, requires a systematic study for FGD gypsum recycling. In this study, we focus on the role and fate of Pb2+ during the conversion of calcium sulfate dihydrate (DH, the leading component of FGD gypsum) to α-hemihydrate (α-HH) whiskers, in Pb2+ ion-containing ethylene glycol (EG)-water solutions. The results demonstrate that Pb2+ retards DH–α-HH conversion by decreasing the driving force and simultaneously reducing the aspect ratios by shortening the lengths of the whiskers. Four major Pb2+ species, including free Pb2+ ions, Pb2+ in anglesite precipitate, weakly adsorbed Pb2+, and Pb2+ doped onto/into calcium sulfate surfaces are determined to be present. Most Pb2+ is distributed in the solids, while a small amount of Pb2+ moves freely in the solutions. During the induction period of conversion, the majority of Pb2+ is weakly adsorbed on DH, and the remaining Pb2+ exists in anglesite. Upon the initiation of conversion, the anglesite phase starts accumulating, and the adsorbed Pb2+ transfers into the surface lattice of α-HH (denoted as doping Pb2+). The adsorbed Pb2+ on α-HH increases significantly from 0.055 to 1.63 wt% and the doping Pb2+ decreases slightly from 0.82 to 0.76 wt% within a c(Pb2+)initial value of 500–1500 mg/L. Kinetically controlled lattice incorporation accounts for the variation in doping Pb2+. These findings provide new insights into the synthesis of α-HH whiskers, which is influenced by heavy metals and may be useful in FGD gypsum utilization.

The physical and mechanical properties of recycled gypsum and potential application of pre-molded panels

This study analyses the physical properties of recycled gypsum and mechanical performance of pre-molded gypsum panels made of recycled gypsum. A compatation with commercial gypsum physical properties and mechanica behavior of pre-molded commercial gypsum panels is also carried out. After collection, recycling and grinding gypsum residues, the quality of the powder produced was evaluated in terms of units of mass and fineness modulus. Additional tests of the dry paste were conducted for assessment of hardness, water absorption, and compressive strength of recycled gypsum. The commercial potential of the material was evaluated by the bending strength testing pre-molded panels. The results demonstrate that gypsum recycling is sustainable, ecologically correct and feasible for the production of pre-molded elements with great potential use in civil construction. Keywords: gypsum panels, mixed pastes, sustainable, gypsum pastes.

Characterization of quality recycled gypsum and plasterboard with maximized recycled content

The quality of secondary materials is imperative to promote a circular economy. In order to improve the way in which the quality of recycled gypsum is assessed, European guidelines on recycled gypsum (RG) quality criteria have been outlined in the framework of the Life+ Gypsum to Gypsum (GtoG) project. Such GtoG guidelines, along with the European Standard on gypsum plasterboard EN 520, provided the basis for this study. During the GtoG project, gypsum recycling and plasterboard manufacturing processes were monitored by testing the gypsum feedstock and the plasterboard produced. The aim of this paper is to discuss the results obtained on relevant parameters that characterize gypsum as a secondary raw material, as well as the resulting product. The minimum requirements were fulfilled by 56% of the RG samples and 86% of the plasterboard with increased RG.

Best practices for the management of end-of-life gypsum in a circular economy

While gypsum can effectively be recycled, most gypsum waste (GW) is currently landfilled in the European Union. In order to achieve higher recovery rates and promote a closed-loop supply chain, it is necessary that stakeholders can implement best practices, in particular from waste production to waste processing, processes that are part of the end-of-life (EoL) stage. In this stage, waste production cannot be reduced, and therefore the priority should be to appropriately collect and recover EoL products. The aim of the paper is to investigate best practices for the management of EoL gypsum in a circular economy. To achieve this, best practices for the management of EoL construction products are selected from the literature, adapted to the case of EoL gypsum and subjected to stakeholder consultation. Results revealed significant differences in the waste management practices between two target groups: gypsum recycling and non-gypsum recycling countries. It is concluded that three best practices are fundamental to promote a circular economy for gypsum products: on-site segregation of GW, clear waste acceptance criteria and clear recycled gypsum quality criteria.

Economic evaluation to recycling plaster

This paper evaluates the economic feasibility of a gypsum recycling plant in the Metropolitan Region of Curitiba, located in southern Brazil. The objective is to study this type of project behaviour on the Brazilian economic scenario, as all the production of gypsum powder concentrates at the Northeast of Brazil, around 3,000 Km far from south. This new market of recycling plants could diversify productive activities, could increase local incomes and taxes to municipality through construction waste materials. Knowing that a kilogram of virgin gypsum powder costs in average U$ 0.128, we studied seven possibilities to reach the economic feasibility of a recycling plant. The first four simulations varies selling prices and the three others simulations varies production. Besides that, we studied the possibility to sell the final product to neighbour states that have higher prices. The results indicate that the average selling price does not consolidate the company neither competes with the prices in the neighbour states. In order to make it feasible the product needs higher prices, which would need other economic arrangements, partnerships and new ideas to this sector that we discuss further.

Exploring factors influencing post-consumer gypsum recycling and landfilling in the European Union

Post-consumer gypsum waste (GW) is increasingly generated in the European Union and not adequately managed in 20 out of the 28 European countries. Overall, it is estimated that 87% of post-consumer GW is landfilled in the EU-28. This waste stream holds unique characteristics, mainly due to its non-inert nature and its high sulphate content. Two main undesirable effects are produced when gypsum is not managed appropriately. First, gypsum contaminates concrete for recycling when treated as mixed waste. Second, the disposal of GW at landfills poses a risk of higher landfill emissions. Overall, potential secondary resources are lost. The main objective of this study is to explore factors influencing gypsum recycling and landfilling in the EU-28. The method includes a study of the literature and a structured questionnaire distributed to stakeholders. Data analysis is used to rank the critical factors (CFs) and conduct a comparison of respondents’ views divided into two groups (gypsum recycling and non-gypsum recycling countries are differentiated). The results show a set of 15 CFs categorized into four domains: policy, economic, social and environmental. More than half of the CFs belong to the policy domain, which indicates the relevance of regulatory and economic instruments for promoting a circular economy for gypsum.

Characteristics of Gypsum Recycling in Different Cycles

In Brazil, the gypsum plaster waste is 4% to 15% of construction and demolition waste. The environmental legislation advises that this waste should be recycled to avoid the contamination of soil and groundwater. The aim of this work is to show that the recycled gypsum plaster maintains its characteristics when submitted to different recycling cycles. The recycled gypsum plasters were produced by grinding and burning the waste along three successive recycling cycles. The recycled materials were evaluated by chemical and physical properties. The obtained results showed that both recycled and commercial gypsum plaster are similar to using in the Construction Industry.

Management of Gypsum in Construction Site - Case Study

The waste generated by the construction sector have increased significantly, becoming an increasing problem, since most of this waste is deposited irregularly, not giving its proper disposal. Such waste, if not disposed properly contribute to environmental degradation, affecting not only the environment, but also, the quality of life. The gypsum products are among the wastes of this activity. Gypsum is a material that has many applications in the construction and generates significant volume of waste that most often is not reused, and usually has its final destination in landfills or dumps. The objective of this research was check on a construction site what kinds of alternatives are used for the management of waste gypsum in the building. The plaster can be recycled easily, being used in the production of cement. For the realization of recycling, there's the ATT - Transshipment Areas and Screening, in which they receive the plaster and other residues to prepare them for their industrial reuse. This way you can properly allocate the waste gypsum, without causing environmental damage and promoting better management of the construction site. Keywords: recycling of gypsum, management of construction site.

石膏系埋没材のリサイクルに関する研究（その２） -適切な粉砕条件-

石膏系埋没材のリサイクルに関する研究（その２） -適切な粉砕条件-