Statistical modeling of geopolymers from dual-alkali activation of un-calcined phosphate sludge and their potential applications as sustainable coating materials
| Autor: | Bouchaib Manoun, Touria El Ghailassi, Rachid Boulif, Mina Oumam, A. Bouih, Hasna Hamdane, Said Mansouri, Youssef Tamraoui, Hassan Hannache |
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| Rok vydání: | 2021 |
| Předmět: |
Materials science
Absorption of water Renewable Energy Sustainability and the Environment 020209 energy Strategy and Management 05 social sciences 02 engineering and technology engineering.material Industrial and Manufacturing Engineering Geopolymer Compressive strength Coating Flexural strength Chemical engineering 050501 criminology 0202 electrical engineering electronic engineering information engineering engineering Cementitious Curing (chemistry) Metakaolin 0505 law General Environmental Science |
| Zdroj: | Journal of Cleaner Production. 283:125421 |
| ISSN: | 0959-6526 |
| Popis: | Upcycling phosphate mining sludges to produce a green cementitious binder, called geopolymer, has recently been implemented; although interesting, a thermal activation has been required to increase their reactivity, in detriment of the energy consumption, environmental footprint and costs. This paper provides an innovative approach to phosphate sludge disposal without any thermal activation, through a dual-alkali activation of NaOH–KOH for designing sustainable geopolymer coating binder of metakaolin with up-to 50 wt% replacement by un-calcined phosphate sludge (UPS). RSM-based statistical design was undertaken to optimize and understand the influence of design factors of activator modulus (MS), ageing time and thermal curing on compressive strength, apparent porosity and water absorption as targeted properties, through polynomial models. Optimal geopolymer testing included measurements of initial-final setting time and durability against 5% NaCl, 5% Na2SO4 and 2% HCl attack up to 3 months, through the visual examination, weight loss and flexural strength.The microstructures of the optimal binder highlighted significant changes in the geopolymeric network, including the formation of hybrid type gels (N,K)-A-S-H or (C,N,K)-A-S-H, silica gel and C-A-S-H/C–S–H co-existing with an inactive filler material exerted by unreacted particles. The optimal binder with RSM methodology reached in a high compressive strength of 49.78 ± 0.30 MPa at 26 days of curing, which obviously confirmed in terms of the microstructural features. A thermal curing (50C°) looks effective to maintain a suitable setting time while achieving excellent mechanical and chemical stability in aggressive environments. In these blends, the UPS chemistry is effective to improve both the mechanical and the durability properties where it acts basically as a barrier (chemical and/or physical) owing to the dual-alkali cations (MS = 1.32) in the activation solution. This study confirms the promise of using the elaborated UPS-MK based geopolymers as sustainable coating materials, which could substantially promote a cleaner production in the construction sector and phosphate mines. |
| Databáze: | OpenAIRE |
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