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Calcined nanosized tubular halloysite for the preparation of limestone calcined clay cement (LC3)
Abstract Halloysite is a kind of 1:1 clay mineral having a special nanosized tubular morphology and pore structure. In this work, nanosized tubular halloysite calcined at 750 °C (Hal750) and limestone (LS) were used to partially replace the ordinary Portland cement (OPC) for the preparation of limestone calcined clay cement (LC3). The mechanical properties and microstructure of LC3 were studied. The results revealed that the obtained LC3 had higher early compressive strengths on 3 and 7 days than did plain OPC. LC3 with a replacement ratio of 22.5% (containing 15.0% Hal750 and 7.5% LS) resulted in maximum compressive strength of 46.38 MPa, being 9.4% higher than OPC's after 28 days of curing. Further, LC3 featured a compact microstructure and smaller critical pore size than OPC, which is mainly because more additional C-(A)-S-H, hemicarboaluminate (Hc), and monocarboaluminate (Mc) were formed in LC3 system, thus contributing to the matrix densification and strength development. However, when the replacement ratio exceeded 37.5%, the insufficient portlandite (CH) limited the pozzolanic reaction with Hal750, leaving excess Hal750 in the LC3 that led to their inhomogeneous microstructure, and thus weakened the mechanical properties. These results show that halloysite is a promising material for the preparation of LC3 whose properties are sensitive to the replacement ratio used.
Highlights Calcined halloysite is feasible to prepare limestone calcined clay cement (LC3). The compressive strength of LC3 is sensitive to the replacement ratio by Hal750 and LS. LC3 prepared from calcined halloysite features a higher compressive strength than OPC.
Calcined nanosized tubular halloysite for the preparation of limestone calcined clay cement (LC3)
Abstract Halloysite is a kind of 1:1 clay mineral having a special nanosized tubular morphology and pore structure. In this work, nanosized tubular halloysite calcined at 750 °C (Hal750) and limestone (LS) were used to partially replace the ordinary Portland cement (OPC) for the preparation of limestone calcined clay cement (LC3). The mechanical properties and microstructure of LC3 were studied. The results revealed that the obtained LC3 had higher early compressive strengths on 3 and 7 days than did plain OPC. LC3 with a replacement ratio of 22.5% (containing 15.0% Hal750 and 7.5% LS) resulted in maximum compressive strength of 46.38 MPa, being 9.4% higher than OPC's after 28 days of curing. Further, LC3 featured a compact microstructure and smaller critical pore size than OPC, which is mainly because more additional C-(A)-S-H, hemicarboaluminate (Hc), and monocarboaluminate (Mc) were formed in LC3 system, thus contributing to the matrix densification and strength development. However, when the replacement ratio exceeded 37.5%, the insufficient portlandite (CH) limited the pozzolanic reaction with Hal750, leaving excess Hal750 in the LC3 that led to their inhomogeneous microstructure, and thus weakened the mechanical properties. These results show that halloysite is a promising material for the preparation of LC3 whose properties are sensitive to the replacement ratio used.
Highlights Calcined halloysite is feasible to prepare limestone calcined clay cement (LC3). The compressive strength of LC3 is sensitive to the replacement ratio by Hal750 and LS. LC3 prepared from calcined halloysite features a higher compressive strength than OPC.
Calcined nanosized tubular halloysite for the preparation of limestone calcined clay cement (LC3)
Yu, Ting (author) / Zhang, Baifa (author) / Guo, Haozhe (author) / Wang, Qiang (author) / Liu, Dong (author) / Chen, Jiarong (author) / Yuan, Peng (author)
Applied Clay Science ; 232
2022-12-07
Article (Journal)
Electronic Resource
English
Method for preparing limestone calcined clay cement from halloysite
| European Patent Office | 2022