The Mechanical Properties of Geopolymers from Different Raw Materials and the Effect of Recycled Gypsum
Geopolymers are amorphous inorganic polymers that are mainly used in the construction industry as an environmentally friendly alternative to ordinary cement. This study compared selected mechanical properties (setting time, shrinkage, strength) of geopolymer specimens made from different main raw ma...
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MDPI AG
2023-07-01
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| Series: | Inorganics |
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| Online Access: | https://www.mdpi.com/2304-6740/11/7/298 |
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| author | Henna Korhonen Juha Timonen Sari Suvanto Pipsa Hirva Kirsi Mononen Sirpa Jääskeläinen |
| author_facet | Henna Korhonen Juha Timonen Sari Suvanto Pipsa Hirva Kirsi Mononen Sirpa Jääskeläinen |
| author_sort | Henna Korhonen |
| collection | DOAJ |
| description | Geopolymers are amorphous inorganic polymers that are mainly used in the construction industry as an environmentally friendly alternative to ordinary cement. This study compared selected mechanical properties (setting time, shrinkage, strength) of geopolymer specimens made from different main raw materials, mainly at room temperature, and investigated the effects of recycled gypsum on these. A structural analysis of the specimens was conducted with XRD and SEM. Also, the leaching of aluminium, silicon, and calcium from the specimens was investigated. According to this study, raw materials have a significant impact on the properties of geopolymers. Recycled gypsum affected the setting time of the geopolymers, but the effect was not the same for all specimens. It increased the setting time of specimens made from calcium-rich raw materials, for example, and the ground-granulated blast furnace slag specimens hardened as fast as ordinary Portland cement (about 300 min), but the addition of gypsum decreased it to 1300 min. Gypsum-containing specimens, based on Ca-deficient metakaolin or fly ash, hardened even faster than OPC, in 100–150 min. Recycled gypsum significantly reduced the plastic shrinkage of most of the 28 d specimens to lower values than those achieved for OPC (0.07%). The only exceptions were the fly-ash-based specimens. However, gypsum had no effect on the drying shrinkage, which accounted for a larger proportion of the total shrinkage in most specimens. Therefore, it had no significant effect on the total shrinkage of the geopolymer specimens. The reducing effect of gypsum on the plastic shrinkage of geopolymers was attributed to ettringite, which was observed in all gypsum-containing specimens analysed with XRD. In this study, recycled gypsum decreased the compressive strength of the specimens, which could be prevented by using a finer gypsum powder. |
| first_indexed | 2024-03-11T00:58:53Z |
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| language | English |
| last_indexed | 2024-03-11T00:58:53Z |
| publishDate | 2023-07-01 |
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| series | Inorganics |
| spelling | doaj.art-9dc4723f20234f5a904ce935078c0cc72023-11-18T19:48:08ZengMDPI AGInorganics2304-67402023-07-0111729810.3390/inorganics11070298The Mechanical Properties of Geopolymers from Different Raw Materials and the Effect of Recycled GypsumHenna Korhonen0Juha Timonen1Sari Suvanto2Pipsa Hirva3Kirsi Mononen4Sirpa Jääskeläinen5Department of Chemistry, University of Eastern Finland, P.O. Box 111, Fi-80101 Joensuu, FinlandApila Group Oy Ab, Hietalantie 7A, Fi-80710 Lehmo, FinlandDepartment of Chemistry, University of Eastern Finland, P.O. Box 111, Fi-80101 Joensuu, FinlandDepartment of Chemistry, University of Eastern Finland, P.O. Box 111, Fi-80101 Joensuu, FinlandApila Group Oy Ab, Hietalantie 7A, Fi-80710 Lehmo, FinlandDepartment of Chemistry, University of Eastern Finland, P.O. Box 111, Fi-80101 Joensuu, FinlandGeopolymers are amorphous inorganic polymers that are mainly used in the construction industry as an environmentally friendly alternative to ordinary cement. This study compared selected mechanical properties (setting time, shrinkage, strength) of geopolymer specimens made from different main raw materials, mainly at room temperature, and investigated the effects of recycled gypsum on these. A structural analysis of the specimens was conducted with XRD and SEM. Also, the leaching of aluminium, silicon, and calcium from the specimens was investigated. According to this study, raw materials have a significant impact on the properties of geopolymers. Recycled gypsum affected the setting time of the geopolymers, but the effect was not the same for all specimens. It increased the setting time of specimens made from calcium-rich raw materials, for example, and the ground-granulated blast furnace slag specimens hardened as fast as ordinary Portland cement (about 300 min), but the addition of gypsum decreased it to 1300 min. Gypsum-containing specimens, based on Ca-deficient metakaolin or fly ash, hardened even faster than OPC, in 100–150 min. Recycled gypsum significantly reduced the plastic shrinkage of most of the 28 d specimens to lower values than those achieved for OPC (0.07%). The only exceptions were the fly-ash-based specimens. However, gypsum had no effect on the drying shrinkage, which accounted for a larger proportion of the total shrinkage in most specimens. Therefore, it had no significant effect on the total shrinkage of the geopolymer specimens. The reducing effect of gypsum on the plastic shrinkage of geopolymers was attributed to ettringite, which was observed in all gypsum-containing specimens analysed with XRD. In this study, recycled gypsum decreased the compressive strength of the specimens, which could be prevented by using a finer gypsum powder.https://www.mdpi.com/2304-6740/11/7/298geopolymermechanical propertiesrecycled gypsumside stream materialsenvironmental impact |
| spellingShingle | Henna Korhonen Juha Timonen Sari Suvanto Pipsa Hirva Kirsi Mononen Sirpa Jääskeläinen The Mechanical Properties of Geopolymers from Different Raw Materials and the Effect of Recycled Gypsum Inorganics geopolymer mechanical properties recycled gypsum side stream materials environmental impact |
| title | The Mechanical Properties of Geopolymers from Different Raw Materials and the Effect of Recycled Gypsum |
| title_full | The Mechanical Properties of Geopolymers from Different Raw Materials and the Effect of Recycled Gypsum |
| title_fullStr | The Mechanical Properties of Geopolymers from Different Raw Materials and the Effect of Recycled Gypsum |
| title_full_unstemmed | The Mechanical Properties of Geopolymers from Different Raw Materials and the Effect of Recycled Gypsum |
| title_short | The Mechanical Properties of Geopolymers from Different Raw Materials and the Effect of Recycled Gypsum |
| title_sort | mechanical properties of geopolymers from different raw materials and the effect of recycled gypsum |
| topic | geopolymer mechanical properties recycled gypsum side stream materials environmental impact |
| url | https://www.mdpi.com/2304-6740/11/7/298 |
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