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A platform for research: civil engineering, architecture and urbanism
Micro and macro properties of silico-aluminophosphate geopolymer: Role of incinerated sewage sludge ash (ISSA)
Abstract The mechanistic insights into silico-aluminophosphate (SAP) geopolymer formation remain an enigma. Here, we aim to elucidate this process and improve the early-age performance of SAP geopolymers by utilizing incinerated sewage sludge ash (ISSA). Interestingly, phosphoric acid-ISSA interaction released Ca2+ and Al3+ ions from ISSA faster than the dealumination of metakaolin. These ions agglutinated with the active soluble (PO4)3- units, evidenced by transmission electron microscopy (TEM), enhancing the early-age compressive strength of ISSA-incorporated SAP geopolymer binders. In contrast, the later strengths were relatively similar to the reference. Such binders had primary silico-alumino-phosphate (S-A-P) gels, possibly intimate with calcium-phosphate (C-P) and alumino-phosphate (A-P) gels, improving the micromechanical properties of the binder. The elastic moduli of these gels lay between 23–25 GPa, higher than conventional N-A-S-H gels. Furthermore, ISSA switched the chemistry of reaction products by favoring AlIV-OP units over AlVI-OP units in SAP geopolymers, even though the Si environment remained unchanged, as confirmed by NMR.
Highlights Formation mechanism of SAP geopolymer with and without ISSA is reported. ISSA addition enhanced the early-age compressive strength of SAP geopolymer. ISSA reduced the phosphoric acid in the SAP geopolymers by up to 28% by weight. The mechanisms that govern such observations are discussed in detail.
Micro and macro properties of silico-aluminophosphate geopolymer: Role of incinerated sewage sludge ash (ISSA)
Abstract The mechanistic insights into silico-aluminophosphate (SAP) geopolymer formation remain an enigma. Here, we aim to elucidate this process and improve the early-age performance of SAP geopolymers by utilizing incinerated sewage sludge ash (ISSA). Interestingly, phosphoric acid-ISSA interaction released Ca2+ and Al3+ ions from ISSA faster than the dealumination of metakaolin. These ions agglutinated with the active soluble (PO4)3- units, evidenced by transmission electron microscopy (TEM), enhancing the early-age compressive strength of ISSA-incorporated SAP geopolymer binders. In contrast, the later strengths were relatively similar to the reference. Such binders had primary silico-alumino-phosphate (S-A-P) gels, possibly intimate with calcium-phosphate (C-P) and alumino-phosphate (A-P) gels, improving the micromechanical properties of the binder. The elastic moduli of these gels lay between 23–25 GPa, higher than conventional N-A-S-H gels. Furthermore, ISSA switched the chemistry of reaction products by favoring AlIV-OP units over AlVI-OP units in SAP geopolymers, even though the Si environment remained unchanged, as confirmed by NMR.
Highlights Formation mechanism of SAP geopolymer with and without ISSA is reported. ISSA addition enhanced the early-age compressive strength of SAP geopolymer. ISSA reduced the phosphoric acid in the SAP geopolymers by up to 28% by weight. The mechanisms that govern such observations are discussed in detail.
Micro and macro properties of silico-aluminophosphate geopolymer: Role of incinerated sewage sludge ash (ISSA)
Alrefaei, Yazan (author) / Ali, Hafiz Asad (author) / Lao, Jian-Cong (author) / Dai, Jian-Guo (author) / Poon, Chi Sun (author)
2024-01-01
Article (Journal)
Electronic Resource
English
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