Gypsum was used as substrate,and silica gel was mixed into substrate at a certain mass ratio to prepare humidity-controlling composites;moreover,the moisture absorption and desorption properties of gypsum-based compos...Gypsum was used as substrate,and silica gel was mixed into substrate at a certain mass ratio to prepare humidity-controlling composites;moreover,the moisture absorption and desorption properties of gypsum-based composites were compared with adding different silica gel particle size and proportion.The morphological characteristics,the isothermal equilibrium moisture content curve,moisture absorption and desorption rate,moisture absorption and desorption stability,and humidity-conditioning performance were tested and analyzed.The experimental results show that,compared with pure-gypsum,the surface structure of the gypsum-based composites is relatively loose,the quantity,density and aperture of the pores in the structure increase.The absorption and desorption capacity increase along with the increase of silica gel particle size and silica gel proportion.When 3 mm silica gel particle size is added with a mass ratio of 40%,the maximum equilibrium moisture content of humidity-controlling composites is 0.161 g/g at 98% relative humidity(RH),3.22 times that of pure-gypsum.The moisture absorption and desorption rates are increased,the equilibrium moisture absorption and desorption rates are 2.68 times and 1.61 times that of pure-gypsum at 58.5% RH,respectively.The gypsum-based composites have a good stability,which has better timely response to dynamic humidity changes and can effectively regulate indoor humidity under natural conditions.展开更多
Radionuclides naturally occurring in building materials may significantly contribute to the annual doses to the public. For instance, familiar building materials such as the concrete and gypsum board have been reporte...Radionuclides naturally occurring in building materials may significantly contribute to the annual doses to the public. For instance, familiar building materials such as the concrete and gypsum board have been reported to produce a dose of about 0.04 mSv per year for a typical person (NCRP 1987c). External as well as internal exposures are two pathways of radiation dose imparted to human beings from the building materials. As information on the radioactivity of such materials is lacking, the study of gypsum materials used in Egypt was carried out in order to estimate the annual dose to the Egyptian population due to natural radionuclides in building materials. During the study, 18 samples of commonly used gypsum raw materials were collected and measured. The activity concentrations were determined by gamma ray spectrometry. Their mean values were in the ranges of 499.29 ± 11.53 Bq·kg-1 for 40K, 91.97 ± 2.61 Bq·kg-1 for 226Ra, 37.62 ± 1.67 Bq·kg-1 for 238U and 42.27 ± 2.22 Bq·kg-1 for 232Th. The activity indexed Iγ for 18, different gypsum samples varied from 0.31 ± 0.03 to 2.3 ± 0.19 and the radium equivalent activity (Raeq), from 38.81 ± 1.68 to 324.7 ± 9.42. These values are lower than the limit of 370 Bq·kg-1 adopted by the Organization for Economic Cooperation and Development (OECD). The average indoor annual effective gamma dose rate (DE) in (mSv/y) for the people, caused by the building materials of dwellings, was assessed for most commonly gypsum materials. It was estimated to be in the range from 0.10 ± 0.003 mSv/y to 0.74 ± 0.08 mSv/y. The internal and external hazard indices (Hin, Hex) and the absorbed dose rate in air D in each sample were evaluated to assess the radiation hazard for people living in dwelling made of the studied materials. The absorbed dose rate of indoor air in samples G1, G2, G11, G17 and G18 is less than the international recommended value which is 55 nGyh-1. While the absorbed dose rate for samples G3, G4, G5, G6, G7, G8, G9, G10, G12, G13, G14, G15 and G16 is higher than 55 nGyh-1, these samples are not acceptable for use as building materials.展开更多
This article is focused on the investigation of the mechanical and thermal properties of composite material that could be used for the production of plaster or plasterboards.This composite material is made of gypsum a...This article is focused on the investigation of the mechanical and thermal properties of composite material that could be used for the production of plaster or plasterboards.This composite material is made of gypsum and reinforcing natural fibers.The article verifies whether this natural reinforcement can improve the investigated properties compared to conventional plasters and gypsum plasterboards made of pure gypsum.From this composite material,high-strength plasterboards could then be produced,which meet the higher demands of users than conventional gypsum plasterboards.For their production,natural waste materials would be used efficiently.As part of the development of new building materials,it is necessary to specify essential characteristics for their later use in civil engineering.Crushed wheat straw and three gypsum classes with strengths G2(2 MPa)—gypsum Class I.,G5(5 MPa)—gypsum Class II.and G16(16 MPa)—gypsum Class III.were used to create the test samples.Samples were made with different ratios of the two ingredients,with the percentages of straw being 0%,2.5%,and 5%for each gypsum grade.The first part of the article describes how the increasing proportion of straw affects the composite’s mechanical properties(flexural strength and compressive strength).The second part of the article focuses on the change of thermal properties(thermal conductivity and specific heat capacity).The last part of the article mentions the verification of the fire properties(single-flame source fire test and gross heat of combustion)of this composite material.The research has shown that the increasing proportion of straw reinforcement caused a deterioration in the flexural strength(up to 56.49%in the 3.series of gypsum Class II.)and compressive strength(up to 80.27%in the 3.series of gypsum Class III.)and an improvement in the specific heat capacity and thermal conductivity(up to 31.40%in the 3.series).This composite material is thus not suitable for the production of high-strength plasterboards,but its reduced mechanical properties do not prevent its use for interior plasters.Based on the performed fire tests,it can be said that this composite material can be classified as a non-flammable material of reaction to fire Classes A1 or A2.From an ecological point of view,it is advantageous to use a composite material with a higher straw content.展开更多
Gypsum is a traditional building material. To improve the humidity-controlling properties of gypsum, we prepared a new type of humidity-controlling composite using the sol-gel method. Methods to determine the maximum ...Gypsum is a traditional building material. To improve the humidity-controlling properties of gypsum, we prepared a new type of humidity-controlling composite using the sol-gel method. Methods to determine the maximum equilibrium moisture content and speed of adsorption/desorption were subsequently applied to analyze the performance of the samples. The appearance and structural properties of the samples were characterized by scanning electronic microscopy (SEM). The experimental results show that the humidity-controlling gel with added LiCl exhibits high moisture storage and that the equilibrium maximum moisture content is 5.652 g/g at a 75.29% relative humidity (RH). A mass ratio of LiCl/sol = 0.15 is demonstrated to be appropriate for the preparation of the new humidity-controlling composites. A coarse network with tiny pores is observed on the surface of the new humidity-controlling composites, and this pore network provides sufficient space for moisture adsorption.展开更多
Experimental investigation was conducted on the effects of gypsum types and SO 3 content on the fluidity and strengths of different cementitious systems.The experimental results show that influences of gypsum in vari...Experimental investigation was conducted on the effects of gypsum types and SO 3 content on the fluidity and strengths of different cementitious systems.The experimental results show that influences of gypsum in various cementitious materials are different.For cementitious materials blended with various proportions of slag fly ash and 5% gypsum content,influences of gypsum and calcined gypsum on the fluidity and flexural/compressive strength are similar.It is revealed that 'combination effect' and 'synergistic effect' of slag and fly ash play an important role during hydration.For cementitious materials with 45% clinkers,30%slag,20%fly ash and 5%limestone,the optimized SO 3 contents in gypsum and calcined gypsum are 3.13% and 3.51% respectively and the optimized gypsum content is 6.5%.While both of them are blended,the optimum ratio of gypsum to calcined gypsum is 40%∶60%(total gypsum content 6.5%),correspondingly the optimum ratio of SO 3 is 19.3%∶32.4%.展开更多
基金Funded by the National Natural Science Foundation of China(No.51678254)。
文摘Gypsum was used as substrate,and silica gel was mixed into substrate at a certain mass ratio to prepare humidity-controlling composites;moreover,the moisture absorption and desorption properties of gypsum-based composites were compared with adding different silica gel particle size and proportion.The morphological characteristics,the isothermal equilibrium moisture content curve,moisture absorption and desorption rate,moisture absorption and desorption stability,and humidity-conditioning performance were tested and analyzed.The experimental results show that,compared with pure-gypsum,the surface structure of the gypsum-based composites is relatively loose,the quantity,density and aperture of the pores in the structure increase.The absorption and desorption capacity increase along with the increase of silica gel particle size and silica gel proportion.When 3 mm silica gel particle size is added with a mass ratio of 40%,the maximum equilibrium moisture content of humidity-controlling composites is 0.161 g/g at 98% relative humidity(RH),3.22 times that of pure-gypsum.The moisture absorption and desorption rates are increased,the equilibrium moisture absorption and desorption rates are 2.68 times and 1.61 times that of pure-gypsum at 58.5% RH,respectively.The gypsum-based composites have a good stability,which has better timely response to dynamic humidity changes and can effectively regulate indoor humidity under natural conditions.
文摘Radionuclides naturally occurring in building materials may significantly contribute to the annual doses to the public. For instance, familiar building materials such as the concrete and gypsum board have been reported to produce a dose of about 0.04 mSv per year for a typical person (NCRP 1987c). External as well as internal exposures are two pathways of radiation dose imparted to human beings from the building materials. As information on the radioactivity of such materials is lacking, the study of gypsum materials used in Egypt was carried out in order to estimate the annual dose to the Egyptian population due to natural radionuclides in building materials. During the study, 18 samples of commonly used gypsum raw materials were collected and measured. The activity concentrations were determined by gamma ray spectrometry. Their mean values were in the ranges of 499.29 ± 11.53 Bq·kg-1 for 40K, 91.97 ± 2.61 Bq·kg-1 for 226Ra, 37.62 ± 1.67 Bq·kg-1 for 238U and 42.27 ± 2.22 Bq·kg-1 for 232Th. The activity indexed Iγ for 18, different gypsum samples varied from 0.31 ± 0.03 to 2.3 ± 0.19 and the radium equivalent activity (Raeq), from 38.81 ± 1.68 to 324.7 ± 9.42. These values are lower than the limit of 370 Bq·kg-1 adopted by the Organization for Economic Cooperation and Development (OECD). The average indoor annual effective gamma dose rate (DE) in (mSv/y) for the people, caused by the building materials of dwellings, was assessed for most commonly gypsum materials. It was estimated to be in the range from 0.10 ± 0.003 mSv/y to 0.74 ± 0.08 mSv/y. The internal and external hazard indices (Hin, Hex) and the absorbed dose rate in air D in each sample were evaluated to assess the radiation hazard for people living in dwelling made of the studied materials. The absorbed dose rate of indoor air in samples G1, G2, G11, G17 and G18 is less than the international recommended value which is 55 nGyh-1. While the absorbed dose rate for samples G3, G4, G5, G6, G7, G8, G9, G10, G12, G13, G14, G15 and G16 is higher than 55 nGyh-1, these samples are not acceptable for use as building materials.
基金This article was financed from the budget of the Student Grant Competition VSB-TUO(Registration No.SGS SP2020/135)This article has been elaborated in the framework of scholarship of the City of Ostrava(RRC/2806/2019)+1 种基金in the framework of the grant programme“Support for Science and Research in the Moravia-Silesia Region 2018”(RRC/10/2018)financed from the budget of the Moravian-Silesian Region.
文摘This article is focused on the investigation of the mechanical and thermal properties of composite material that could be used for the production of plaster or plasterboards.This composite material is made of gypsum and reinforcing natural fibers.The article verifies whether this natural reinforcement can improve the investigated properties compared to conventional plasters and gypsum plasterboards made of pure gypsum.From this composite material,high-strength plasterboards could then be produced,which meet the higher demands of users than conventional gypsum plasterboards.For their production,natural waste materials would be used efficiently.As part of the development of new building materials,it is necessary to specify essential characteristics for their later use in civil engineering.Crushed wheat straw and three gypsum classes with strengths G2(2 MPa)—gypsum Class I.,G5(5 MPa)—gypsum Class II.and G16(16 MPa)—gypsum Class III.were used to create the test samples.Samples were made with different ratios of the two ingredients,with the percentages of straw being 0%,2.5%,and 5%for each gypsum grade.The first part of the article describes how the increasing proportion of straw affects the composite’s mechanical properties(flexural strength and compressive strength).The second part of the article focuses on the change of thermal properties(thermal conductivity and specific heat capacity).The last part of the article mentions the verification of the fire properties(single-flame source fire test and gross heat of combustion)of this composite material.The research has shown that the increasing proportion of straw reinforcement caused a deterioration in the flexural strength(up to 56.49%in the 3.series of gypsum Class II.)and compressive strength(up to 80.27%in the 3.series of gypsum Class III.)and an improvement in the specific heat capacity and thermal conductivity(up to 31.40%in the 3.series).This composite material is thus not suitable for the production of high-strength plasterboards,but its reduced mechanical properties do not prevent its use for interior plasters.Based on the performed fire tests,it can be said that this composite material can be classified as a non-flammable material of reaction to fire Classes A1 or A2.From an ecological point of view,it is advantageous to use a composite material with a higher straw content.
基金financially supported by the National Natural Science Foundation of China(51172176)
文摘Gypsum is a traditional building material. To improve the humidity-controlling properties of gypsum, we prepared a new type of humidity-controlling composite using the sol-gel method. Methods to determine the maximum equilibrium moisture content and speed of adsorption/desorption were subsequently applied to analyze the performance of the samples. The appearance and structural properties of the samples were characterized by scanning electronic microscopy (SEM). The experimental results show that the humidity-controlling gel with added LiCl exhibits high moisture storage and that the equilibrium maximum moisture content is 5.652 g/g at a 75.29% relative humidity (RH). A mass ratio of LiCl/sol = 0.15 is demonstrated to be appropriate for the preparation of the new humidity-controlling composites. A coarse network with tiny pores is observed on the surface of the new humidity-controlling composites, and this pore network provides sufficient space for moisture adsorption.
文摘Experimental investigation was conducted on the effects of gypsum types and SO 3 content on the fluidity and strengths of different cementitious systems.The experimental results show that influences of gypsum in various cementitious materials are different.For cementitious materials blended with various proportions of slag fly ash and 5% gypsum content,influences of gypsum and calcined gypsum on the fluidity and flexural/compressive strength are similar.It is revealed that 'combination effect' and 'synergistic effect' of slag and fly ash play an important role during hydration.For cementitious materials with 45% clinkers,30%slag,20%fly ash and 5%limestone,the optimized SO 3 contents in gypsum and calcined gypsum are 3.13% and 3.51% respectively and the optimized gypsum content is 6.5%.While both of them are blended,the optimum ratio of gypsum to calcined gypsum is 40%∶60%(total gypsum content 6.5%),correspondingly the optimum ratio of SO 3 is 19.3%∶32.4%.
