Alkali-Activated Materials (AAM) (GEOPOLYMERS)
Alkali-activated materials (AAM), also called geopolymers or inorganic polymers, have received a lot of attention lately because they have the potential to partly replace ordinary Portland cement (OPC) as a construction material. Studies have shown that AAMs have mechanical properties as good as, or even better than, OPC concrete. In addition, other beneficial properties, such as fire resistance and their typically light weight, make it possible to use them for such purposes as constructing panels or making ceramics. The increased interest in AAMs lies in the fact that they can be produced from waste materials, such as fly ash, mine tailings, and slags. In 2012, OPC production was estimated to account for 8% of global CO2 emissions, and government policies worldwide strongly encourage reducing OPC use. This explains the recent interest in finding alternative construction materials and binders.
Mineral wools are the most common insulation materials in buildings worldwide. However, mineral wool waste is often considered unrecyclable because of its fibrous nature and low density. In this paper, rock wool (RW) and glass wool (GW) were studied as alkali-activated material precursors without any additional co-binders. Both mineral wools were pulverized by a vibratory disc mill in order to remove the fibrous nature of the material. The pulverized mineral wools were then alkali-activated with a sodium aluminate solution. Compressive strengths of up to 30.0 MPa and 48.7 MPa were measured for RW and GW, respectively, with high flexural strengths measured for both (20.1 MPa for RW and 13.2 MPa for GW). The resulting alkali-activated matrix was a composite-type in which partly-dissolved fibers were dispersed. In addition to the amorphous material, sodium aluminate silicate hydroxide hydrate and magnesium aluminum hydroxide carbonate phases were identified in the alkali-activated RW samples. The only crystalline phase in the GW samples was sodium aluminum silicate.
Proper thermal insulation is needed throughout the world, because it is the most effective way to save energy used for heating and cooling buildings. Mineral wools—a general term for rock wool and glass wool—are the most common insulation materials in the world. They are produced at high temperatures by melting quartz sand, basalt, dolomite, and glass. The molten mixture is fiberized by a high-speed spinning process. A small quantity of organic resin, typically phenol-formaldehyde, is used as an additive to bind the fibers together. As old buildings are torn down or renovated, a large amount of construction and demolition waste is generated, including the waste from mineral wools. Globally, 2.3 million tons of mineral wool waste was generated in 2010, and the amount is expected to rise to 2.5 million tons by the year 2020. Unfortunately, mineral wool is often unrecyclable. The problems in recycling arise from the fibrous nature and low density of the material. Despite many attempts, the utilization of mineral wool waste in post-consumer production remains very low.
Both glass wool and rock wool have high contents of Si and X-ray amorphous mineralogy and, thus, have potential as AAM precursors. However, there has been to date only one preliminary study of utilizing rock wool as raw material for alkali activation. Alkali activation of glass wool has not been previously studied. Mineral wools also have very consistent chemical and physical compositions, which make them even more attractive as raw materials for alkali activation.
SOURCE : http://www.mdpi.com/1996-1944/9/5/312
Yliniemi, J.; Kinnunen, P.; Karinkanta, P.; Illikainen, M. Utilization of Mineral Wools as Alkali-Activated Material Precursor.Materials 2016, 9, 312.
Alkali-activated materials (AAM), also called geopolymers or inorganic polymers, have received a lot of attention lately because they have the potential to partly replace ordinary Portland cement (OPC) as a construction material. Studies have shown that AAMs have mechanical properties as good as, or even better than, OPC concrete. In addition, other beneficial properties, such as fire resistance and their typically light weight, make it possible to use them for such purposes as constructing panels or making ceramics. The increased interest in AAMs lies in the fact that they can be produced from waste materials, such as fly ash, mine tailings, and slags. In 2012, OPC production was estimated to account for 8% of global CO2 emissions, and government policies worldwide strongly encourage reducing OPC use. This explains the recent interest in finding alternative construction materials and binders.
Mineral wools are the most common insulation materials in buildings worldwide. However, mineral wool waste is often considered unrecyclable because of its fibrous nature and low density. In this paper, rock wool (RW) and glass wool (GW) were studied as alkali-activated material precursors without any additional co-binders. Both mineral wools were pulverized by a vibratory disc mill in order to remove the fibrous nature of the material. The pulverized mineral wools were then alkali-activated with a sodium aluminate solution. Compressive strengths of up to 30.0 MPa and 48.7 MPa were measured for RW and GW, respectively, with high flexural strengths measured for both (20.1 MPa for RW and 13.2 MPa for GW). The resulting alkali-activated matrix was a composite-type in which partly-dissolved fibers were dispersed. In addition to the amorphous material, sodium aluminate silicate hydroxide hydrate and magnesium aluminum hydroxide carbonate phases were identified in the alkali-activated RW samples. The only crystalline phase in the GW samples was sodium aluminum silicate.
Proper thermal insulation is needed throughout the world, because it is the most effective way to save energy used for heating and cooling buildings. Mineral wools—a general term for rock wool and glass wool—are the most common insulation materials in the world. They are produced at high temperatures by melting quartz sand, basalt, dolomite, and glass. The molten mixture is fiberized by a high-speed spinning process. A small quantity of organic resin, typically phenol-formaldehyde, is used as an additive to bind the fibers together. As old buildings are torn down or renovated, a large amount of construction and demolition waste is generated, including the waste from mineral wools. Globally, 2.3 million tons of mineral wool waste was generated in 2010, and the amount is expected to rise to 2.5 million tons by the year 2020. Unfortunately, mineral wool is often unrecyclable. The problems in recycling arise from the fibrous nature and low density of the material. Despite many attempts, the utilization of mineral wool waste in post-consumer production remains very low.
Both glass wool and rock wool have high contents of Si and X-ray amorphous mineralogy and, thus, have potential as AAM precursors. However, there has been to date only one preliminary study of utilizing rock wool as raw material for alkali activation. Alkali activation of glass wool has not been previously studied. Mineral wools also have very consistent chemical and physical compositions, which make them even more attractive as raw materials for alkali activation.
SOURCE : http://www.mdpi.com/1996-1944/9/5/312
Yliniemi, J.; Kinnunen, P.; Karinkanta, P.; Illikainen, M. Utilization of Mineral Wools as Alkali-Activated Material Precursor.Materials 2016, 9, 312.
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