Alkaline-washed phosphogypsum-based cemented paste backfill prepared using steel slag and blast furnace slag: Mechanical properties, fluoride immobilization, and hydration mechanism
Phosphogypsum (PG)-based cemented paste backfill (PCPB) is an effective way to deal with the problem of PG storage, but the low strength, high cost, and serious fluoride pollution of PCPB limit the popularization of this technology. Alkaline washing has been proven to be an effective means to decrea...
Saved in:
| Main Authors: | , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Elsevier
2024-12-01
|
| Series: | Case Studies in Construction Materials |
| Subjects: | |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S221450952401180X |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| _version_ | 1850138551306420224 |
|---|---|
| author | Qiusong Chen Lingzhi Gao Aixiang Wu Yan Feng Yunbo Tao Daolin Wang |
| author_facet | Qiusong Chen Lingzhi Gao Aixiang Wu Yan Feng Yunbo Tao Daolin Wang |
| author_sort | Qiusong Chen |
| collection | DOAJ |
| description | Phosphogypsum (PG)-based cemented paste backfill (PCPB) is an effective way to deal with the problem of PG storage, but the low strength, high cost, and serious fluoride pollution of PCPB limit the popularization of this technology. Alkaline washing has been proven to be an effective means to decrease fluoride from PG. Steel slag (SS) and ground granulated blast furnace slag (GGBFS) are common materials possessing pozzolanic activity. SS and GGBFS can be employed as cement substitutes under alkaline conditions. This paper proposes the combined heuristic effect of NaOH pretreatment, SS, and GGBFS to improve the strength of alkaline-washed PCPB (APCPB) and the ability of fluoride immobilization. The study results show that alkali washing stimulates the secondary hydration activity of solid waste materials and promotes the formation of hydration products such as AFt and C-S-H so that the UCS value of APCPB increases greatly in the later stages of hydration increases by 309.8 % (7.06 MPa), and the leaching concentration of fluoride decreases by 21.5 % (0.85 mg/L). Through microscopic characterization experiments on the APCPB, it was discovered that in the alkaline hydration system, the transformation of C-S-H and AFt into C-A-S-H, F-C-S-H, and F-AFm, coupled with the physical encapsulation of hydration products, are the main factors immobilizing fluoride. This work provides a much-needed supplement to the in-situ cement-free repair technology of PG in mines to develop more lower-carbon and environmentally friendly mixture formulations. |
| format | Article |
| id | doaj-art-100289926a874c5ebd4c47b3be7535f4 |
| institution | OA Journals |
| issn | 2214-5095 |
| language | English |
| publishDate | 2024-12-01 |
| publisher | Elsevier |
| record_format | Article |
| series | Case Studies in Construction Materials |
| spelling | doaj-art-100289926a874c5ebd4c47b3be7535f42025-08-20T02:30:34ZengElsevierCase Studies in Construction Materials2214-50952024-12-0121e0402810.1016/j.cscm.2024.e04028Alkaline-washed phosphogypsum-based cemented paste backfill prepared using steel slag and blast furnace slag: Mechanical properties, fluoride immobilization, and hydration mechanismQiusong Chen0Lingzhi Gao1Aixiang Wu2Yan Feng3Yunbo Tao4Daolin Wang5School of Resources and Safety Engineering, Central South University, Changsha 410083, China; Engineering Research Center of Ministry of Education for Carbon Emission Reduction in Metal Resource Exploitation and Utilization, Central South University, Changsha 410083, China; School of Civil and Resource Engineering, University of Science and Technology Beijing, Beijing 100083, ChinaSchool of Resources and Safety Engineering, Central South University, Changsha 410083, ChinaSchool of Civil and Resource Engineering, University of Science and Technology Beijing, Beijing 100083, ChinaSchool of Resources and Safety Engineering, Central South University, Changsha 410083, ChinaSchool of Resources and Safety Engineering, Central South University, Changsha 410083, ChinaSchool of Resources and Safety Engineering, Central South University, Changsha 410083, China; Corresponding author.Phosphogypsum (PG)-based cemented paste backfill (PCPB) is an effective way to deal with the problem of PG storage, but the low strength, high cost, and serious fluoride pollution of PCPB limit the popularization of this technology. Alkaline washing has been proven to be an effective means to decrease fluoride from PG. Steel slag (SS) and ground granulated blast furnace slag (GGBFS) are common materials possessing pozzolanic activity. SS and GGBFS can be employed as cement substitutes under alkaline conditions. This paper proposes the combined heuristic effect of NaOH pretreatment, SS, and GGBFS to improve the strength of alkaline-washed PCPB (APCPB) and the ability of fluoride immobilization. The study results show that alkali washing stimulates the secondary hydration activity of solid waste materials and promotes the formation of hydration products such as AFt and C-S-H so that the UCS value of APCPB increases greatly in the later stages of hydration increases by 309.8 % (7.06 MPa), and the leaching concentration of fluoride decreases by 21.5 % (0.85 mg/L). Through microscopic characterization experiments on the APCPB, it was discovered that in the alkaline hydration system, the transformation of C-S-H and AFt into C-A-S-H, F-C-S-H, and F-AFm, coupled with the physical encapsulation of hydration products, are the main factors immobilizing fluoride. This work provides a much-needed supplement to the in-situ cement-free repair technology of PG in mines to develop more lower-carbon and environmentally friendly mixture formulations.http://www.sciencedirect.com/science/article/pii/S221450952401180XPhosphogypsumAlkali-washingFluoride immobilizationPhosphogypsum-based cemented paste backfill |
| spellingShingle | Qiusong Chen Lingzhi Gao Aixiang Wu Yan Feng Yunbo Tao Daolin Wang Alkaline-washed phosphogypsum-based cemented paste backfill prepared using steel slag and blast furnace slag: Mechanical properties, fluoride immobilization, and hydration mechanism Case Studies in Construction Materials Phosphogypsum Alkali-washing Fluoride immobilization Phosphogypsum-based cemented paste backfill |
| title | Alkaline-washed phosphogypsum-based cemented paste backfill prepared using steel slag and blast furnace slag: Mechanical properties, fluoride immobilization, and hydration mechanism |
| title_full | Alkaline-washed phosphogypsum-based cemented paste backfill prepared using steel slag and blast furnace slag: Mechanical properties, fluoride immobilization, and hydration mechanism |
| title_fullStr | Alkaline-washed phosphogypsum-based cemented paste backfill prepared using steel slag and blast furnace slag: Mechanical properties, fluoride immobilization, and hydration mechanism |
| title_full_unstemmed | Alkaline-washed phosphogypsum-based cemented paste backfill prepared using steel slag and blast furnace slag: Mechanical properties, fluoride immobilization, and hydration mechanism |
| title_short | Alkaline-washed phosphogypsum-based cemented paste backfill prepared using steel slag and blast furnace slag: Mechanical properties, fluoride immobilization, and hydration mechanism |
| title_sort | alkaline washed phosphogypsum based cemented paste backfill prepared using steel slag and blast furnace slag mechanical properties fluoride immobilization and hydration mechanism |
| topic | Phosphogypsum Alkali-washing Fluoride immobilization Phosphogypsum-based cemented paste backfill |
| url | http://www.sciencedirect.com/science/article/pii/S221450952401180X |
| work_keys_str_mv | AT qiusongchen alkalinewashedphosphogypsumbasedcementedpastebackfillpreparedusingsteelslagandblastfurnaceslagmechanicalpropertiesfluorideimmobilizationandhydrationmechanism AT lingzhigao alkalinewashedphosphogypsumbasedcementedpastebackfillpreparedusingsteelslagandblastfurnaceslagmechanicalpropertiesfluorideimmobilizationandhydrationmechanism AT aixiangwu alkalinewashedphosphogypsumbasedcementedpastebackfillpreparedusingsteelslagandblastfurnaceslagmechanicalpropertiesfluorideimmobilizationandhydrationmechanism AT yanfeng alkalinewashedphosphogypsumbasedcementedpastebackfillpreparedusingsteelslagandblastfurnaceslagmechanicalpropertiesfluorideimmobilizationandhydrationmechanism AT yunbotao alkalinewashedphosphogypsumbasedcementedpastebackfillpreparedusingsteelslagandblastfurnaceslagmechanicalpropertiesfluorideimmobilizationandhydrationmechanism AT daolinwang alkalinewashedphosphogypsumbasedcementedpastebackfillpreparedusingsteelslagandblastfurnaceslagmechanicalpropertiesfluorideimmobilizationandhydrationmechanism |