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Sustainability of gypsum products as a construction material
... The development of environmental and environmental aspects of the building materials industry, green building technologies and health-saving building materials has made it possible to make a technical breakthrough in the application of gypsum binders and materials [1][2][3][4]. This is due to their compliance with all modern requirements for the safety of production, use and disposal [2]. ...
... Energy costs for obtaining semi-aquatic gypsum are significantly lower than in the case of cement or other mineral binders, which meets the solution to the problem of energy conservation. In the case of the use of finished products based on gypsum, there is also no danger to people, animals and plants, which compares them favorably with modern synthetic materials [3]. It should also be noted that the modern development of materials science allows the repeated recycling of gypsum, which until recently, in the 20th century, seemed impossible [3]. ...
... In the case of the use of finished products based on gypsum, there is also no danger to people, animals and plants, which compares them favorably with modern synthetic materials [3]. It should also be noted that the modern development of materials science allows the repeated recycling of gypsum, which until recently, in the 20th century, seemed impossible [3]. At the same time, issues of resource conservation and environmental protection are successfully resolved [4,5,6]. ...
The possibility of using glass hollow microspheres in self-reinforced gypsum composites in the work is investigated. The need to use microspheres for gypsum products is dictated by modern high requirements for safety and environmental protection to construction sites and the building materials industry. The dispersion characteristics and grain composition of Russian production glass hollow microspheres, as well as the main component, a gypsum binder, were studied. It was established that all compositions contain particles of micro- and nanometer size. It is shown that glass microspheres provide the structure of a composite with a hardened matrix a low density while maintaining the necessary strength without the introduction of expensive and environmentally unsafe chemical additives.
... Another potential environmental advantage of these SSC-PM is that the calcium sulfate can be sourced from>50 industrial by-product sources. That were reported to be suitable for use as a partial or total replacement for natural gypsum [55] [56], such as the An from fluorgypsum used for this research. ...
... • M6 (20%PC-500) and M9 (20%PC-600) mortars may be equivalent to Type M mortars (>17.2 MPa), which is recommended for both reinforced and non-reinforced masonries to bear a large compressive loads [56]. • M8 (10%CaO-10%PC-600) is comparable to a Type S mortar (>12.4 ...
This paper presents an investigation on the effects of pumice fineness and alkaline activators ratio on the physical, mechanical and environmental features of pumice-based supersulfated mortars. These were prepared with a water/binder ratio of 0.40 and a binder: aggregate ratio of 1:2.75 and cured at 60 °C for 22 h; then the hardened samples were stored in dry and wet conditions for up to 120 days. The best results were for the composition 10%quicklime-10%Portland cement-15%anhydrite-65%pumice wet cured that had 28 MPa and a maximum expansion ∼ 0.10%. The mortars with the supersulfated cements are a good cleaner alternative for use as a building material having emissions < 184 kgCO²-eq/m³, which are at least 66% lower than Portland cement mortars.
... The above agrees with Gartner [79] who pointed out that the most promising low-CO 2 alternative cements appear to be those that use large amounts of natural or artificial pozzolans. Therefore, the reduction in CO 2 emissions shown by the SSC-PM with CaO can be attributed mainly to the following: 1) the SSC-PM do not require calcination, which eliminates the need for fossil fuels, 2) the vesicular structure of PM facilitates the grinding process, which reduces the demand of electric energy, 3) the amount of alkaline activator (CaO) becomes the main source of CO 2 emissions and 4) the source of calcium sulfate can be obtained from than 50 sources synthetic gypsum products (industrial wastes containing high proportion of calcium sulfate) that can be applied as partial or total replacement of natural gypsum [80]. Fig. 14 compares the 360-day strength versus the intensity of CO 2 -eq emissions for the studied SSC-PM. ...
... It can also be noted that both types of sulfates are effective; nonetheless, CS resulted in better performance than Na 2 SO 4 ; after 270 days the SSC-PM 7H and 16 A had ~30 MPa, whereas the paste C reached ~22 MPa. However, although the costs could be similar (An: USD$ 60; HH: USD$ 100; Na 2 SO 4 : USD$ 102 [87]), the CaSO 4 can be resourced from the calcination of mineral gypsum or from more than 50 sources of synthetic gypsum products [80]; such as the An used in this study which is a byproduct from the production of hydrofluoric acid. ...
This investigation reports on the mechanisms of reaction, microstructure, hydration products, compressive strength and environmental impact of supersulfated cements based on pumice (SSC-PM), using 10–20%wt of quicklime (CaO) as the alkaline activator and 5–15%wt of sulfatic activators of anhydrite or hemihydrate; three different initial curing temperature (ICT) regimes were used for 24 h, of 20, 40 and 60 °C. The main hydration products were C–S–H and ettringite; minor phases included monosulfate, gypsum, portlandite and calcite. The ICT of 60 °C accelerated the reactions of formation of ettringite and C–S–H, improving the early strength, whereas; the higher contents CaO (20%) and An or HH (15%) slowed the hydration reactions and consequently the early strength development. The activation with CaO-Anhydrite densified the microstructure leading to 360-day strengths of up to 34 MPa. These SSC-PM represent a good sustainable alternative as these showed emissions of 159–281 kgCO2-eq/t, which are at least 67% lower than the manufacture of clinker of Portland cement.
... Gypsum composites are more environmentally friendly and production is faster than cement composites. Mainly due to lower greenhouse gas emissions and sustainability [3]. Gypsum is produced by thermal decomposition of CaSO 4 · 2H 2 O in a so-called boiling process at 130 − 150 • C [4]. ...
The article focuses on the effects of additives increasing biological resistance of gypsum against degradation of the material. In this study we use silver nitrate, calcium oxide and copper sulphate as an additive that improves biological resistance of gypsum composites. The amount of addition was calculated so that the amount of ions was 0.1, 0.3 and 0.5 wt. %. Microbial degradation was determined as the degree of resistance of materials to the occurrence of bacteria and molds by optical and electron microscope. The results obtained from these samples were compared with references materials created in the laboratory and available on today’s market. The results show a positive effect of silver and copper ions on the bioresistance of gypsum.
... Most of them can be considered as substitutes for natural gypsum. Synthetic gypsum normally consists of calcium sulphate dihydrate, calcium sulphate hemihydrate and anhydrite [5,6]. ...
... On the other hand, the calcium sulfate source (HH or An) can be obtained from the calcination of mineral gypsum (the most abundant of the sulfate minerals) or from more than 50 sources of synthetic gypsum products (industrial wastes containing a high proportion of calcium sulfate) that are reported as able to be applied as a total or partial substitution for natural gypsum (Lushnikova et al., 2016). Examples of the latter include the anhydrite (An) from fluorgypsum as investigated in this paper; or other examples that include binders based on BFS (Escalante-García et al., 2009), phosphogypsum (Liu et al., 2019(Liu et al., , 2020, citrogypsum (Bensted, 1980), etc. ...
Novel low emissions supersulfated cements based on volcanic pumice were evaluated in reinforced concretes; the mechanical, microstructural and electrochemical properties were studied for 180 days. The volcanic pumice was chemically activated with anhydrite or hemihydrate and an alkaline activator of quicklime and Portland cement. The binder consumption in the concretes was of 720 kg/m³, of which only 72-144 kg/m³ were of Portland cement; a reference concrete based on the latter was also prepared with 415 kg/m³. The specimens were cured at 25°C or for 22h at 60°C then at 25°C; these were exposed to laboratory conditions or to immersion in 3.5%NaCl at 25°C to induce accelerated corrosion. Compared to the reference concrete, the supersulfated cement based concretes had 65-82% less Portland cement and at least 49% lower CO2 emissions, were up to 26% cheaper and showed similar 28-day and better 180-day compressive strength, reaching up to 44 MPa. Compared to green concretes from the literature, similar or better strengths and up to 24% less CO2 emissions were noted. The penetration of chlorides and electrochemical tests showed that the activation with 10%CaO promoted adequate protection to the embedded steel, in some instances better than the reference concrete. The novel supersulfated cements appear to be a promising alternative to produce sustainable and durable concretes for regions on the world with access to volcanic materials.
The use of paper waste rich in cellulose fibers to produce building materials is an environmentally friendly alternative that conserves natural resources and protects the environment. This work aims to recycle this waste by developing a new ecological lightweight building material based on gypsum. For this purpose, the Design of Experiments (DoE) concept and Response Surface Methodology (RSM) were introduced to develop, optimize, and compare the effect of paper waste and surfactant on gypsum. The results show that after the addition of paper waste and surfactant, the density and brittleness of the formulated materials decrease. Nonetheless, the proposed formulation has allowed to maintain acceptable mechanical properties (2.45 MPa for flexural strength and 5.07 MPa for compressive strength) to be used in the construction and particularly as indoor insulation materials. Likewise, the optimal results obtained from the desirability function have shown an overall gap of 6% between the experimental values and the predicted values. This result confirms the acceptable accuracy of the proposed models for the formulation of this new construction material based on gypsum, paper waste, and surfactant.
In this study, the effectiveness of Near Surface Mounted (NSM) method, for in-plane shear strengthening of traditional and historical Unreinforced Masonry (URM) walls, is investigated through a comprehensive experimental study. For this purpose, square solid clay brick masonry wallettes (42 samples) with three different types of traditional mortars including gypsum mortar, lime-cement-sand mortar and lime-sand mortar are prepared
and retrofitted with NSM Glass Fiber Reinforced Polymer (GFRP) bars. Then, diagonal shear tests are conducted to evaluate the in-plane shear behavior of the masonry wallettes. The effects of some key variables such as wall thickness, the retrofitted face of the wall, reinforcement ratio, and the type of paste for mounting the reinforcing bars, on the effectiveness of the retrofitting method are investigated. The results of the tests are presented in
terms of the failure modes and the lateral shear stress-drift curves of the test specimens. Accordingly, the retrofitting
method can enhance the in-plane shear strength, and the ultimate lateral drift capacity of the URM wallettes. According to the test results, the type of filler paste and reinforcement ratio influence the strength enhancement of the test specimens. Furthermore, in specimens retrofitted with the one-side retrofitting scheme,
due to the asymmetry of walls under in-plane loads, an unexpected out-of-plane deformation is induced in the
walls under in-plane load which adversely affects its global behavior.
The mineralogical composition, microstructure, and reactivity of traditional gypsum, a multiphase product, is closely connected to its calcination temperature, but systematic studies which relate those features to mechanical properties and weathering resistance of plasters are scarce. Here we examined the hydration behavior of gypsum calcined between 100 and 1000 °C, which contained varying amounts of uncalcined gypsum, bassanite, and/or anhydrite II.
Detailed hydration and textural studies allowed the identification of the underlying mechanisms leading to differences in plaster performance related to (i) delayed hydration of anhydrite II along with modifications of the pore system; (ii) a filler effect exerted by anhydrite II and uncalcined gypsum; (iii) disruption of the plaster matrix by uncalcined gypsum; (iv) seeded crystallization in the presence of uncalcined gypsum and anhydrite II. Findings of this study further the understanding of traditional gypsum plaster performance and open opportunities for the development of sustainable building materials by designing optimized gypsum-based mixtures for specific application.
Recent years are showing a rapid adoption of digital manufacturing techniques to the construction industry, with a focus on additive manufacturing. Although 3D printing for construction (3DPC) has notably advanced in recent years, publications on the subject are recent and date a growth in 2019, indicating that it is a promising technology as it enables greater efficiency with fair consumption of material, minimization of waste generation, encouraging the construction industrialization and enhancing and accelerating the constructive process. This new building system not only gives an optimization of the building process but provides a new approach to the building design materiality. The direct connection between design and manufacturing allows the reduction in the number of the various construction phases needed. It is opening a new and wide range of options both formal and chromatic in customization, avoiding complex formworks, reducing costs and manufacturing time. The creative process has a strict and direct link with the constructive process, straightening design with its materiality. Cement-based materials lead the way, but new alternatives are being explored to further reduce its carbon footprint. In order to leverage its sustainability and enhance the system capacity, initiatives are being pursued to allow the reduction of the use of PC. Geopolimers are taking the first steps in 3DPC. Construction and Demolition Waste (CDW) materials are used to substitute natural aggregates. Even soil is being explored has a structural and aesthetic material. These research trends are opening a wider range of possibilities for architecture and design, broadening the spectrum of color, texture, and formal variations. The concern about textures and colours is not yet evident in many the structures already printed, opening the opportunity for future research. More can be done in the mixture and formal design of this building system, “discovering” other raw materials in others waste. This article aims to make a critical review of technologies, materials and methodologies to support the development of new sustainable materials to be used as a plastic element in the printed structure. A roadmap of 3D printing for construction is presented, and an approach on mix design, properties in the fresh and hardened state, highlighting the possibilities for obtaining alternative materials are pointed. With this review possible directions are presented to find solutions to enhance the sustainability of this system discovering “new” materiality for architecture and design.
An experimental study is carried out to investigate the mechanical properties of clay brick masonry fabricated using traditional mortars. In this regard, four types of mortar whose frequent uses in Iranian traditional and historical monuments have been reported in the literature are selected. These mortars are gypsum mortar and three types of lime-based mortars including, Sarooj, lime-sand mortar, and lime-cement-sand mortar. In this study, tests on brick units, mortar specimens, masonry prisms and wallettes are conducted. The compressive stress-strain behavior, compressive strength, elastic modulus, and rupture modulus of mortars are determined from the standard tests. Moreover, the compression test of masonry prisms, direct shear test of brick-mortar bond, and diagonal shear test of masonry wallettes are carried out. The compressive stress-strain behavior of masonry and the shear bond strength of brick-mortar interface are determined from the tests on masonry prisms. Furthermore, shear stress-strain behavior of masonry wallettes is evaluated through diagonal shear tests. Some key mechanical properties of masonry wallettes such as modulus of rigidity and Poisson's ratio are also found from the test results. Accordingly, the brick-mortar bond governed the in-plane shear behavior of the masonry wallettes in diagonal shear tests. Furthermore, the highest compressive strength, elastic modulus, and diagonal shear strength belong to the masonry fabricated with gypsum mortar. By using the results of the experimental program, the applicability of some well-known empirical formulations for estimating the compressive strength of masonry prisms as well as the accuracy of idealized stress-strain models proposed for masonry material, are assessed.
The melt–mixing of polylactide (PLA) with micro- and/or nanofillers is a key method used to obtain specific end-use characteristics and improvements of properties. So-called “insoluble” CaSO4 (CS) β-anhydrite II (AII) is a mineral filler recently considered for the industry of polymer composites. First, the study proves that AII made from natural gypsum by a specifically thermal treatment is highly stable compared to other CS forms. Then, PLAs of different isomer purity and molecular weights (for injection molding (IM) and extrusion), have been used to produce “green” composites filled with 20–40 wt.% AII. The composites show good thermal and mechanical properties, accounting for the excellent filler dispersion and stability. The stiffness of composites increases with the amount of filler, whereas their tensile strength is found to be dependent on PLA molecular weights. Interestingly, the impact resistance is improved by adding 20% AII into all investigated PLAs. Due to advanced kinetics of crystallization ascribed to the effects of AII and use of a PLA grade of high L-lactic acid isomer purity, the composites show after IM an impressive degree of crystallinity (DC), i.e., as high as 50%, while their Vicat softening temperature is remarkably increased to 160 °C, which are thermal properties of great interest for applications requiring elevated rigidity and heat resistance.
An investigation was carried out on the effect of the type of mineral additions of pulverized fuel ash and blast-furnace slag, water/binder ratio and temperature on the properties and microstructures of mortars of composite fluorgypsum-Portland cements. The mortars were cured under water at 20 and 40 °C for up to 90 days; all showed hydraulic character after gradually developing and maintaining their properties. The best 90-day compressive strength of 17.7 MPa was for a binder with 5% blast-furnace slag. The microstructures studied by SEM and EDS mappings showed intermixed hydration products of CaSO4·2H2O from the fluorgypsum and C–S–H from the Portland cement and pozzolanic reactions. Isothermal calorimetry indicated that the mineral additions influenced the rates of heat liberation and setting time. Environmental and economic analyses indicated that the embodied CO2eq for the fabrication of the binders was 2.9–4.1 times lower than Portland cement, while the economic costs were reduced in about 46–48%.
Buildings are one of the main consumers of energy in the world and it is pushing the scientific community to find alternative solutions to improve the thermal insulation of building envelope. The selection of appropriate building materials is an important challenge for improving thermal comfort and energy performance of buildings. In this scenario, the interest of gypsum-plaster based composites is increasing. In this investigation, new plaster-based composites with polyester fibers were produced and tested at lab scale, in order to obtain cheap solutions with improved thermo-acoustic performance. The results show that it is possible to improve the thermal, mechanical, and acoustic performance of construction biomaterials by using plaster as a binder and polyester fibers as reinforcement: thermal conductivity was equal to 0.20 W/m.K, the compressive strength to about 4 MPa, and the transmission loss in the 40–45 dB range. When compared to the plaster without fibers, thermal conductivity was reduced by about 29%, mechanical resistance was increased by about 76%, and absorption coefficient was reduced by about 48%.
The main purpose of this work is to analyze the elastic properties (i.e. Young's modulus and Poisson's ratio) of gypsum specimens manufactured by traditional methods (non-industrial kilns). More specifically we have evaluated the Bajo Aragon variant by means of a low-cost digital image correlation approach. The accuracy of the data was contrasted with the press, obtaining an RMSE of 0.008%, corroborating the viability of the method. The results obtained during this experimental campaign revealed a gypsum with an average compressive strength, Young's modulus and Poisson's ratio of 4.01 MPa, 2989 MPa and 0.24 respectively.
The performance of mechanochemical syngenite applied as hydration accelerator for fully formulated anhydrite-based self-levelling floor screeds was evaluated regarding workability (open time), setting time, compressive strength, shrinkage and microstructural development. Results demonstrate that mechanochemical syngenite substantially increases early and final strength development, but generally reduces workability (fluidity) and shortens the open time. However, addition of a very minor amount of sodium polyphosphate retarder eliminates these disadvantages without hampering the accelerating effect of syngenite. Hence, when combined with NaPP syngenite was found to present a highly effective hydration accelerator for anhydritebased building materials.
In the present study, the applicability of phosphated comb polymers as high range water reducing agents in a fully formulated α-calcium sulfate hemihydrate-based self-leveling floor screed was evaluated. A phosphated and two mixed phosphated-carboxylated superplasticizers were synthesized and compared to a strictly carboxylated sample (PCE) and a commercial melamine formaldehyde sulfite polycondensate (PMS). Self-leveling screeds of variable water content (w/b = 0.41 – 0.25) containing the different polymers were prepared and their key properties such as spread flow, fluidity retention, flow speed, shrinkage as well as setting behavior and strength development were examined. The results obtained encourage the utilization of phosphate group modified comb polymers in screeds based on CaSO4-hemihydrate, particularly in high-performance screeds formulated at low w/b ratio.
An attempt has been made to enhance the properties and applications of gypsum ceiling tiles by utilizing the excellent thermal insulation and flame resistance properties of wool and the durability and strength of coir.Gypsum based ceiling tiles are ubiquitously used for false ceiling applications but have several limitations. Different types of additives, finishes and chemicals have been used to overcome the lack of structural integrity under large impacts, poor resistance to moisture and limited acoustic resistance of gypsum ceiling tiles. Few studies have shown that reinforcing gypsum with natural materials provides better performance properties. Wool and coir are biodegradable natural fibers that are available in large quantities at low costs and have some unique properties suitable for developing green building materials. In this study a blend of wool and coir were used to enhance properties and performance of gypsum ceiling tiles. Composites were manufactured by using 30% fiber and 70% gypsum and varying the proportion of wool and coir between ratios 25 to 75%. The reinforcing fibers were combined with gypsum using water and no other chemical or additives are necessary, making the production of tiles simple and environmentally friendly. Fiber reinforced gypsum showed higher strength (up to 90% higher) and modulus (up to 7%) and also better resistance to moisture. Wool fibers provided substantially higher moisture resistance while coir provided better strength. A blend of the two fibers provided a flame resistance rating of V1 compared to V0 for pure gypsum. Reinforcing gypsum with coir and wool would not only improve thermal and acoustic properties but will also help to reduce cost and make a major portion of the gypsum ceiling tiles biodegradable and thereby decrease environmental burden and helps towards promoting green building initiatives.
Gypsum is widely used in the construction sector in internal coatings. The fact that the chemical composition of gypsum does not change makes the material fully and eternally recyclable, potentially solving the important problem of the large amounts of gypsum waste that each year go to landfills. Up to now, most of the works that use gypsum wastes subjected the material to a previous heating process. This implies a significant energy consumption, reducing the environmental benefits of the recycling process. This paper shows the second part of a research on which two different types of gypsum waste were used as a substitute of commercial gypsum: gypsum waste from industrial plasterboard production and flue gas desulphurization gypsum from a thermal central plant. In this research, the influence of the heating process on the development of new gypsum plaster composites containing different types and contents of waste was studied. Their mechanical properties and thermal conductivity were determined and a brief environmental analysis, using the Life Cycle Assessment method, was carried out.
Based on the findings of this paper, it is confirmed that it is possible to substitute 100% of commercial gypsum with gypsum waste from industrial plasterboard production without any heating treatment, but maintaining a good performance. With this action, apart from the benefits in terms of environmental impacts, a slight improvement in the density, mechanical properties and thermal conductivity of the plaster was obtained.
This paper presents some results on the porosity and pore size distribution of cement paste containing simulated desulphurised waste (SDW) cured for 90 d. The SDW was chosen for the investigation due to the variability in chemical composition of real desulphurised waste as explained in previous papers. The SDW is a combination of 85% fly ash and 15% gypsum. The cement in the pastes was replaced with 0, 20 and 40% SDW. The water to binder ratio was 0.5. The binder consists of cement and SDW (by weight). After 90 d of curing, the porosity and pore size distribution tests were conducted on the pastes. Increasing the amount of SDW leads to an increase in the pore volume of the paste. There is no clear trend on the effect of SDW on the size of the pores.
Smart gypsum composites were manufactured by adding different kinds of microcapsules containing phase change materials (PCMs) in order to develop building materials with high thermal energy storage (TES) capacity useful for being applied in high comfort constructive systems. The physical, thermal and mechanical properties of these composites such as density, porosity, thermal stability, thermal conductivity (k), equivalent heat capacity (cp), the accumulated heat power (qacc) and the maximum compressive strength were studied. Results showed that the higher the microcapsules content, the lower the density and k and the higher the cp and qacc, due to the PCM action. Besides, the addition of 15 wt% of microcapsules respect to the hemihydrate would allow to save 4.5 kWh of energy per operating cycle in a standard room covered with 1 m3 of this gypsum. This energy is equivalent to the energy spent by three incandescent light bulbs of 60-W kept on all the day and a reduction of 1.395 kg of CO2 emissions to the atmosphere. The addition of these thermoregulating materials to gypsum decreases their compressive strength but all the developed materials satisfied the Spanish mechanical regulations for gypsum as building material, being possible to increase the total amount of added microcapsules.
A mathematical model of the process of gypsum optimal structure formation has been designed with the application of computer simulation methods. An optimal raw mix speciation and gypsum specimen strength top values corresponding to the model were experimentally obtained and recorded. (C) 2013 The Authors. Published by Elsevier Ltd. Selection and peer-review under responsibility of the Vilnius Gediminas Technical University
This paper is part of a wide-ranging investigation on the use of flue gas desulphurisation (FGD) waste in cement-based materials. It reports the results on the porosity and pore size distribution of cement paste containing varying amounts of simulated FGD waste. The water to binder ratio was 0.5. The binder consists of cement and simulated FGD. The FGD is a combination of fly ash and gypsum ranging from 0% to 100%. Cement in the pastes was partially replaced with 25% FGD (by weight). The porosity and pore size distribution of cement pastes was determined during the early stage of hydration. Increasing the amount of gypsum does not increase the pore volume. However, increasing the amount of gypsum in the paste leads to an increase in the threshold diameter and a decrease in the percentage of small pores in the paste, both indicating a coarser pore structure. The results of this investigation were compared with data at longer curing periods.
This paper reports on the use of secondary minerals to make Controlled Low Strength Materials for trench or mine backfill. The mixes used red titanogypsum which is a by-product of titanium dioxide pigment production. A number of other secondary minerals were considered for mixing with the gypsum and steel slag from the basic oxygen process was found to be most successful. An optimised mix was developed and a site trial was carried out. The results showed a good performance but the failure of one test sample during curing showed that the material may not be suitable for other applications.
Glass fiber reinforced gypsum (GFRG) walls are prefabricated large gypsum panels with hollow cores. Developed in Australia in the early 1990s and subsequently adopted by other countries, including China and India, this material is used in residential, commercial, and industrial buildings. GFRG walls are used both architecturally and structurally as walls and slabs, with no columns and beams required. They have already found wide application, even without mature structural design codes, largely because of their environmental friendliness. In India, GFRG walls have been approved by the World Bank as being eligible for Carbon Credits under the Kyoto Protocol. GFRG panels are a composite material consisting of gypsum plaster and glass fibers. When the cavities are filled with reinforced concrete, the interaction between the concrete and the GFRG panels produces another composite. As a result, the structural behavior of GFRG walls and the associated building system are more complicated than that of conventional structural systems. This paper presents the results of extensive experimental and theoretical investigations into the structural behavior of GFRG walls, and offers a structural design methodology for GFRG walls and the associated building system.
Alpha-hemihydrate of calcium sulphate can be obtained by suspending gypsum in boiling or almost boiling aqueous solution
of an inorganic acid salts or sulphuric acid at atmospheric pressure. Our task was to try to obtain it from citrogypsum in
unheated solution of this acid. The experiment proved it possible if 10, 15, 20, 30, or 40 wt.% solution was used, and that the
resulting alpha-hemihydrate developed at various ratios and had different properties, depending on the acid solution
concentration and the gypsum/acid solution mixing ratio. An alpha-hemihydrate composed of smooth, compact, acicular
monocrystals, which according to reference data promises the best utilitarian aspect, was obtained using 20 wt.% acid
solution at 0.25 g cm-3 mixing ratio.
Gypsum is a very soft mineral composed of calcium sulfate dihydrate and often occurs in nature as flattened and often twinned crystals and transparent cleavable masses called selenite. This new book presents research data from around the globe in the study of gypsum including the mining activity and geotechnical and hydreological issues related to the presence of gypsum in Asturias, Spain; the effects of flue gas desulfurization gypsum on the performances of cement based materials; the biomechanical and biological evidences supporting the in vitro application of gypsum in three decisive spinal surgical processes and luminescence spectroscopy as a sensor for the setting of gypsum plaster.
Gypsum is the most common sulfate mineral on earth and is commonly associated with halite, anhydrite, sulfur, calcite and dolomite in recent coastal (sabkha or salina) and/or continental (playa) evaporite deposits. Gypsum can appear as transparent crystals (selenite); fibrous, elongated crystals (stain spar); granular and compact masses (alabaster); and in rosette-shaped aggregates called desert roses. The calcium sulfate-water system occurs as three principal solid phases: gypsum (CaSO4.2H2O), bassanite (CaSO4.0.5H2O), and anhydrite (CaSO4). Only gypsum and anhydrite are stable phases of these three phases. Uncalcined gypsum and calcined gypsum are consumed in large quantities worldwide, principally for use in the construction and agricultural industries. In building, it is used in plaster, plaster of Paris, wallboard, cement, and ceramic tiles. In agriculture, it is used as an amendment to neutralize sodic soils and to promote the growth of vegetables. World resources of gypsum are large and widely distributed. The top producing countries of gypsum in 2009, in descending order, are China, Iran, Spain, United States, Thailand, Japan and Canada. In 2009, crude and uncalined gypsum production in United States were estimated to be 9.4 and 7.7 million tons, respectively. The average values per metric ton reported by U.S. producers in 2009 were $8.5 for crude gypsum and $40.0 for calcined gypsum. Demand for gypsum products is expected to decreases in the coming decade as housing starts continue to drop.
The recycling of inorganic wastes generated by different industrial processes is a research field of high interest because the minimization of waste disposal, avoiding its potential release into the environment, can generate environmental and economical benefits for these industries and the general population. The appropriate treatment of industrial wastes could even lead to the generation of co-products of economic value and broad application. Obviously, the environmental and health impact of these co-products should comply with existing regulations.In this direction, the present study describes first the used raw materials ilmenite (ILM) and slag (SLAG) and a waste known as "red gypsum" (RG) coming from a titanium dioxide industrial facility located at the province of Huelva (Spain), in terms of their elemental composition, radioactive contents, granulometry, mineralogy, microscopic morphology and physical composition. The main goal was to obtain basic information for future potential applications of the RG waste in construction, civil engineering, etc. One of these applications has been studied in the second part of our study: we have analysed the main properties of cements produced with different proportions of red gypsum, and their obtained improvements, in relation to Ordinary Portland Cements (OPC). In the produced RG cements, it has been also demonstrated that the levels of pollutants associated always remain within safety limits.
The work reported here forms part of a wide-ranging research project on the optimum use of waste from dry and semi-dry flue gas desulfurisation (FGD) processes in concrete. This study examined the influence of a typical simulated desulfurised waste (SDW) on the physical and mechanical and physical properties of concrete. SDW was chosen due to the wide variability in the composition of actual FGD waste. Two binder systems were investigated: cement and SDW (C-SDW) and cement, slag and SDW (C-S-SDW). The SDW content ranged from 0 to 70% and the slag from 0 to 90% as partial cement replacements. The properties examined included compressive and flexural strengths, water absorption, shrinkage and expansion. The results showed that replacing cement with SDW beyond 20% systematically reduces strength. An increase in SDW content reduces shrinkage. The presence of small amounts of slag allows the use of high proportions of SDW. The use of desulfurised waste in concrete applications is possible as adequate strength can be achieved.
The main cost incurred in the production of concrete paving blocks is the cost of the cement-based binders. In addition, there is the environmental cost of quarrying and processing of these primary materials. Gypsum-based industrial by-products have been identified as alternative sources of cement. These materials have little or no production cost and their reuse negates the need for disposal, offering a more sustainable material for the production of paving blocks. Laboratory trials have investigated the properties of red gypsum, derived as a coproduct associated with titanium dioxide manufacture, mixed with pulverised-fuel ash, ground granulated blastfurnace slag, lime and basic steel slag. An assessment of samples was made using unconfined compressive strength after 28 days curing. It was found that a red gypsum ground granulated blastfurnace slag mix achieved the highest unconfined compressive strength (up to 39 MPa) and was selected for further investigation. Two binders, composed primarily of red gypsum and ground granulated blastfurnace slag, were mixed with sand and pea gravel to make 100 mm concrete cubes and compared with Portland cement for uniaxial compressive strength, stiffness and workability. The red gypsum-based binder compared favourably with Portland cement, indicating that there is potential to integrate red gypsum into concrete block mixes.
This paper reports on a comprehensive study on the properties of concrete containing borogypsum. Properties studied include setting time and volume expansion of paste, unit weight and consistency of fresh concrete, compressive and splitting tensile strength of hardened concrete. Potential use of borogypsum as a concrete admixture is discussed. Borogypsum contents of 0%, 3%, 5%, 10% and 15% by mass are used in the study. The strength results show that concrete mixtures containing 3% and 5% borogypsum developed higher strength values than those of control concrete mixtures. Based on strength properties, it is determined that 5-10% borogypsum may be used as a concrete additive. On the other hand, inclusion of borogypsum as a cement replacement reduced the consistency. Moreover, test results also showed that borogypsum delays setting time of paste made with cement and borogypsum. Thus, the use of borogypsum as a set retarder of Portland cement is recommended.
In this work, properties of sulphate technogenic raw material - flue gas desulphurization (FGD) gypsum have been investigated in order to obtain alpha-hemihydrate gypsum as gypsum binding material. FGD gypsum is produced as a by-product during the process of desulphurization of exhaust gas emitted in power stations heated by fuel containing sulphur. It has been determined that alpha-hemihydrate gypsum can be obtained from FGD gypsum under hydrothermal conditions at 125 degrees C and 130 degrees C. The compressive strength of gypsum samples is 13 MPa - 16 MPa after 2 h of hardening and it depends on temperature and time of isothermic curing. The compressive strength of the same samples in dry state is 49 MPa - 67 MPa. SEM analysis data showed that the properties of alpha-hemihydrate gypsum significantly depend on the shape and size of its crystals: when crystals have near form to regular hexagonal - shaped prism with length and width ratio approx. of 4 : 1, the gypsum exhibits the high quality mechanical and physical properties.
This paper presents results of an investigation of calcium sulphate-blast furnace slag binders cured for up to 600 days with small additions of fly-ash or silica fume. Hemihydrate and fluorgypsum were used as the calcium sulphate sources. The binders showed good mechanical and hydraulic properties; the water resistance was attributed to the formation of C–S–H with Ca/Si ratio between 1.08 and 1.78 finely intermixed with the gypsum initially formed. Ettringite was formed after the reaction between gypsum and aluminum from the slag and fly ash; however, its formation was hindered in the presence of silica fume, which improved the dimensional stability.
Industrial production of pipe foam insulation generates huge volumes of scrap material, driving to a serious environmental problem.
This research studies the potential of adding different size particle proportions of this waste rubber to a plaster matrix. For this purpose, an experimental plan has been elaborated which characterizes the physical and mechanical behavior of the new composite: Shore C hardness, flexure and compressive strength. Furthermore, different particle sizes, weight rates and water/plaster ratios have been analyzed.
In view of the results this waste rubber could be incorporated in gypsum based composites forming part of new lightweight products.
An investigation was performed on the improvement of properties for commercial hemihydrate by means of low additions of granulated blast furnace slag and pozzolanas like silica fume or fly ash. Results after 180 days for pastes cured under water at 20 °C showed that it is possible to triplicate the compressive strength of plain plaster. The reaction mechanism can be summarized by the total reaction of the hemihydrate in the first 24 h, followed by the slower slag and pozzolanas hydration and interaction of the sulfates with aluminium to form ettringite. Excellent dimensional stability and low density was also observed.
This article addresses the microstructure and related mechanical properties of gypsum produced from β-hemihydrate using information of its hydration process, from fresh paste to hardened gypsum.The water demand of the investigated β-hemihydrate was determined applying the spread flow test. The flowability was studied and the deformation coefficient of the β-hemihydrate was derived accordingly. The hydration process of the β-hemihydrate was investigated applying an ultrasonic wave method and the influence of the water content on hydration was analyzed.The microstructure of the generated gypsum was studied by experiments and modeling. A model [1] was applied, which was successfully validated by the present experiments. Furthermore, the mechanical properties of the produced gypsum were investigated, and a numerical relation between water amount and strength was found.
A pilot scale preparation of α-calcium sulfate hemihydrate (α-HH) from flue gas desulfurization (FGD) gypsum was conducted for the first time in mixed salt solutions under atmospheric pressure. The effects of salt solution recycling on the transition of α-HH from FGD gypsum were investigated by a comparison with that in laboratory scale, focusing on the dehydration rate of FGD gypsum, the crystal morphology, chemical composition and mechanical strength of the products. α-HH could be transformed from FGD gypsum in 3.5–6.0h even though the salt solution was recycled seven times in laboratory tests and eight times in pilot tests. The product obtained in pilot scale has a purity of 95% and the α-HH crystals are mostly a prismatic morphology, with volume weighted mean diameter (D[3,4]) in the range of 52.9–84.0μm, 2h bending strength of 5.6–6.2MPa and 3d compressive strength of 15.7–25.3MPa. The salt solution recycling achieves 56% recovery of salts in pilot scale and puts almost no negative impact on the product quality, which can be one of the best strategies to reduce the production cost. It is very likely that the process of salt solution recycling can be adopted in industry.
The aim of this paper is to investigate the possible displacement of natural gypsum (CaSO4·2H2O) in cement with an alternative setting retarder, such as the industrial by-product derived from flue gas desulfurization process called FGD gypsum. These calcium-sulfate-bearing materials (CSBM), alone or in mixtures, were ground with clinker both in laboratory and industrial scale to examine their influence on the physical and mechanical properties of cement, as well as on the industrial production line of cement. From the present work, it is extracted that the use of mixtures of sulfate-bearing materials with gypsum seems to be advantageous for the actual control of setting time. The addition of FGD gypsum increases setting time without affecting compressive strength profile. During the industrial trial, the formation of hemihydrate form of calcium sulfate dihydrate has a profound regulatory effect on the setting and strength performance of the cement partially replaced with FGD gypsum.
Portland cements containing tartaro- and titanogypsum were respectively hydrated for up to two hours at a water: cement ratio of 0.5. They were compared with a Portland cement containing high grade natural gypsum hydrated similarly. The cement containing tartarogypsum produced much more ettringite than those with titanogypsum and natural gypsum. Comparisons were made with previous examinations of the hydration of Portland cements containing other by-product gypsums. Reasons for the observed hydration behaviour of the Portland cements with tartaro- and titanogypsum are discussed.ResumenOs cimentos portlands que contêm o tartaro- e o titanogesso foram respectivamente hidratados próprio para duas horas à proporção água: cimento 0.5. Foram comparados com um cimento portland que conteve um gesso natural duma alta qualidade, que foi hidratado semelhantemente. O cimento que conteve o tartarogesso produziu mais da etringite que esses que contiveram o titanogesso e o gesso natural. As comparações foram feitas com as investigações da hidratação dos cimentos portlands que contiveram os outros gessos que são os produtos accessórios. As razões para a hidratação observada dos cimentos portlands que contiveram o tartaro- e o titanogesso são discutidas.
2) Medicines and Drugs Technology Institute, Oswaldo Cruz Foundation, Rio de Janeiro, Brazil elba1996 (at) iq.ufrj.br 1 -INTRODUCTION Energy availability, supply and use play a central role in the way societies organize themselves, from individual welfare to social and industrial development. By extension, energy accessibility and cost is a determining factor for the economical, political and social interrelations among nations. Considering energy sources, human society has dramatically increased the use of fossil fuels in the past 50 years in a way that the most successful economies are large consumers of oil. However, geopolitical factors related to security of oil supply, high oil prices and serious environmental concerns, prompted by global warming -the use of petrol for transportation accounts for one-third of greenhouse gas emissions (Wyman, 1996) -have led to a push towards decreased consumption. Indeed, the world's strongest economies are deeply committed to the development of technologies aiming at the use of renewable sources of energy. Within this agenda, the substitution of liquid fuel gasoline by renewable ethanol is of foremost importance. Brazil has been a front-runner in the use of renewable fuels. The substitution of gasoline by ethanol started in 1975, when the Brazilian Government launched the "Proálcool Program" (Programa Nacional do Álcool). At the time of the first oil crisis, in the 1970s, the country imported 85% of its oil needs and the potential for ethanol production from sugarcane as a transportation fuel was in good agreement with the Government policy regarding energy supply independence. The Proálcool Program included incentives for distilleries and automobile companies that made ethanol-only cars. Although in the mid-1970s environmental concern was not a major driving force for substituting the use of gasoline, it is worth pointing out the global environmental benefits that have resulted from this policy since then. Presently, the ethanol industry in Brazil runs without government incentives and the biofuel is distributed by the Brazilian oil company Petrobras. The Brazilian fleet of 20 million cars (the total vehicle fleet including cars, light commercials, trucks and buses is around 24 million) runs on either a gasoline blend containing 22-24% ethanol or on 100% ethanol. Natural gas has also been marginally used. Ethanol consumption is forecast to increase as the number of "flex-fuel" cars, with engines able to run on both gasoline blend or ethanol, is forecast to increase from the present 4 million to 15 million in 2013 (Associação Nacional dos Fabricantes de Veículos Automotores -www.anfavea.com.br).
The hydration of calcium sulphate hemihydrate (CaSO4·0.5H2O) leading to the crystallization of gypsum (calcium sulphate dihydrate – CaSO4·2H2O) has been the subject of several investigations over a long period and a vast amount of data is widely distributed throughout in the literature. In this review article an overall picture of the subject is presented. The properties of the two hemihydrates (α- and β-), their hydration characteristics, the mechanism of their hydration and the crystal growth of gypsum are discussed. Additives modify the microstructures of the hardened gypsum and reduce its strength. A probable mechanism is discussed.
Paper presents the studies on characterization, beneficiation and utilization of H-acid gypsum, a waste material produced by the neutralization of free sulphuric acid collected during the formation of intermediate dyes. The waste gypsum contains impurity of organic matter like nitro compounds, naphthalene etc. The removal of impurities and improvement in colour was carried out by scrubbing with water, centrifuging and drying. The beneficiated H-acid gypsum was calcined to form β-hemihydrate plaster. The plaster was tested and evaluated for engineering properties such as compressive strength, bulk density, water absorption and porosity. These properties suggest the use of beneficiated H-acid gypsum for making building and ceramic grade plasters and for casting building blocks, board and cementitious binder. Data showed that cementitious binder of low water absorption (9.5%) and adequate compressive strength (19.6 MPa at 28 days) can be produced for use as construction material. The use of waste gypsum will definitely benefit environment and sustainable development.
Boron ores are used in the production of various boron compounds such as boric acid, borax and boron oxide. Boric acid is produced by reacting colemanite(2CaO·3B2O3·5H2O) with sulphuric acid and a large quantity of borogypsum is formed during this production. This waste causes various environmental problems when discharged directly to the environment. Portland cement is the most important material in the building industry. This material is produced by adding about 3–5% gypsum (CaSO4·2H2O) to clinker as a set retarder. The aim of this study was to stabilize borogypsum, and to produce cements by adding borogypsum instead of natural gypsum to clinker. Concrete using cement produced with borogypsum was tested to find the mechanical properties and the test values were compared with those of concrete from cement with natural gypsum. Compressive strength of concrete from cement produced with borogypsum was found to be higher than that of natural gypsum. Also, the setting time of cement with borogypsum was longer than that of the Portland cement.
Contemporary requirements for gypsum-based composite materials (GBCM) for rendering or plastering include controlled setting time, good workability, sag resistance, high compressive and flexural strength, perfect bond to concrete or brick, water resistance, and improved heat and noise insulation. The application of a number of chemical admixtures and mineral additives was found to be necessary to provide the required performance for gypsum-based materials. Among the necessary chemical admixtures are the following: a retarding admixture, a water-soluble polymer (MC), an air-entraining admixture (AE), and a superplasticizer (SP). This paper describes the effect of the different admixtures on the consistency, setting time, and the compressive strength of GBCM. It also discusses the application of the stepwise optimization (SWO) method for the evaluation of the GBCM composition.
In this study, by using UV-visible adsorption spectrophotometer, Zeta potential analyzer and X-ray photo spectroscopy, the adsorption characteristics and surface electrochemical properties of two types of superplasticizer-β-naphthalene sulfonic acid type (BNS) and polycarboxylate type (PC) and their effects on the fluidity of gypsum plaster were studied. The results show that the adsorption of BNS and PC on gypsum surface approximately conforms to Langmuir's adsorption isotherm. The adsorption of BNS belongs to physical adsorption, its adsorption heat being 14.71 kJ/mol and the thickness of adsorption layer 120 Å; while the adsorption of PC belongs to chemical adsorption, with an adsorption heat of 20.85 kJ/mol and a thickness of adsorption layer of 120 Å. The adsorption conformation of BNS is lying on the flat of gypsum surface, generating weak steric hindrance to inhibit agglomerate of gypsum particles. Its dispersion effect mainly depends on electrostatic repulsive force caused by ζ-potential, which is determined by the adsorbed amount of BNS at the first adsorption layer on gypsum surface. The adsorption conformation of PC is comb-shaped, generating strong steric hindrance by side chains of adsorption layer, thus, its dispersion ability mainly comes from a combination effect of steric hindrance and electrostatic repulsive force. The dispersion by steric hindrance is less affected by the rapid hydration of gypsum, thus, its stability is much better than that of electrostatic repulsive force, resulting in little flow loss of fresh gypsum plaster.
With insufficient source separation, construction and demolition (C&D) waste becomes a mixed material that is difficult to recycle. Treatment of mixed C&D waste generates residue that contains gypsum and organic matter and poses a risk of H(2)S formation in landfills. Therefore, removing gypsum and organic matter from the residue is vital. This study investigated the distribution of gypsum and organic matter in a sorting process. Heavy liquid separation was used to determine the density ranges in which gypsum and organic matter were most concentrated. The fine residue that was separated before shredding accounted for 27.9% of the waste mass and contained the greatest quantity of gypsum; therefore, most of the gypsum (52.4%) was distributed in this fraction. When this fine fraction was subjected to heavy liquid separation, 93% of the gypsum was concentrated in the density range of 1.59-2.28, which contained 24% of the total waste mass. Therefore, removing this density range after segregating fine particles should reduce the amount of gypsum sent to landfills. Organic matter tends to float as density increases; nevertheless, separation at 1.0 density could be more efficient.
Construction and demolition (C&D) debris recycling facilities often produce a screened material intended for use as alternative daily cover (ADC) at active landfills or for shaping and grading at closed landfills. This product contains soil and small pieces of wood, concrete, gypsum drywall, shingles and other components of C&D debris. Concerns have been raised over the contribution of gypsum drywall in C&D debris fines to odor problems at landfills where the product is used. To address such concerns, limitations may be placed on the percentage of gypsum (or sulfate) that can occur, and standardized testing procedures are required to permit valid compliance testing. A test procedure was developed for measuring the gypsum content in C&D debris fines. The concentration of sulfate leached in an aqueous solution was used to estimate the initial gypsum content of the sample. The impact of sample size and leaching time were evaluated. Precision and accuracy increased with increasing gypsum content. Results from replicate samples had an average relative standard deviation of 9%. The gypsum content of fines obtained from different facilities in the US varied widely from 1% to over 25%. These variations not only occurred between differing facilities, but within batches produced within a single facility.
Building Energy Data Book, 1.6.6 Embodied Energy of Interior Wall Assemblies in the
BEDB, 2009. Building Energy Data Book, 1.6.6 Embodied Energy of Interior Wall Assemblies in
the U.S., pp. 1-37. Prepared for the Buildings Technologies Program. Energy Efficiency and
Renewable Energy U.S. Department of Energy by D&R International, Ltd., 1.6.6 Embodied
Energy of Interior Wall Assemblies in the U.S. Available at: http://static1.squarespace.com/
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A Cradle-to-Gate Life Cycle Assessment of ½″ Regular and 5/8″ Type X Gypsum Wallboard. Prepared for the Gypsum Association by Athena Sustainable Materials Institute, Ottawa, Final Report
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Bushi, L., Meil, J., 2011. A Cradle-to-Gate Life Cycle Assessment of ½″ Regular and 5/8″
Type X Gypsum Wallboard. Prepared for the Gypsum Association by Athena Sustainable
Materials Institute, Ottawa, Final Report, November 2011 [December 21, 2011], 132 pp.
Building Mineral Binding Materials. Infra-Ingeneria
- L Dvorkin
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Properties of Gypsum Binders Modified With Complex Admixtures. Ibausil-Internationale Baustofftagung
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Dvorkin, L.Y., Lushnikova, N.V., 2009. Properties of Gypsum Binders Modified With Complex
Admixtures. Ibausil-Internationale Baustofftagung, Tagunsbericht, Weimar, Institut für
Baustoffkunde, Band 2, pp. 1-0701-1-0707.
Design Strategy of Foam Gypsum Proportioning
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Dvorkin, L.Y., Dvorkin, О.L., Bezusyak, A.V., Lushnikova, N.V., Kovalyk, I.V., 2012. Design
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Declaration-Explanatory Note. Scientific and Technical Committee Environment and
Raw Materials Committee. 5 pp. Available at: http://www.eurogypsum.org/_uploads/
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Environmental Product Declaration. Typical (5/8″ Type X) North American Gypsum Boards
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EPD NAGB, 2014. Environmental Product Declaration. Typical (5/8″ Type X) North American
Gypsum Boards. Declaration number: FPI/GA/01/2014 Issued May 2014 Valid until May
2019. Available at: http://www.gypsum.org/wp/wp-content/uploads/2013/12/Gypsum-2014-FINAL-May-13-.pdf.
Gypsum Materials and Products: Production and Application
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Ferronskaya, A.V. (Ed.), 2004. Gypsum Materials and Products: Production and Application.
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Gypsum-Based Products: Environmental Product Declaration
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GBP EPD, 2009. Gypsum-Based Products: Environmental Product Declaration, first ed.
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Greene M. (Managing Editor) 2009. Gypsum Construction Handbook, sixth ed. Construction
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Rheological behaviour of gypsum plaster pastes with polyamide powder wastes. 25th Anniversary Session for ACI 228-Building on the Past for the Future of NDT of Concrete
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behaviour of gypsum plaster pastes with polyamide powder wastes. 25th Anniversary
Session for ACI 228-Building on the Past for the Future of NDT of Concrete. Constr.
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Global Industry Markets and Outlook
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Embodied Energy and Carbon Footprint Database
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Sustainable architecture module
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